Use of antimicrobials and carriage of penicillin-resistant ... - Hirsla

Use of Antimicrobialsand Carriage ofPenicillin-ResistantPneumococci in ChildrenRepeated cross-sectional studies covering 10 yearsVilhjalmur Ari ArasonPhD ThesisUniversity of Iceland,Faculty of Medicine, Department of Family MedicineOctober 2006

FromDepartment of Family Medicine, University of Iceland,Primary Healthcare Centre of Solvangurand Healthcare Centre Fjördur, IS-220 Hafnarfjördur, IcelandUse of Antimicrobials andCarriage of Penicillin-ResistantPneumococci in ChildrenRepeated cross-sectional studies covering 10 yearsVilhjalmur Ari ArasonSupervisorJohann A. SigurdssonCo-supervisorKarl G. KristinssonPhD committee:Thorolfur Gudnason (chair), Directorate of Health, IcelandJohann A. Sigurdsson, University of IcelandVilhjalmur Rafnsson, University of IcelandMagnus Johannsson, University of IcelandHaraldur Briem, Directorate of Health, IcelandReykjavík 2006

Vilhjálmur Ari Arason:Use of Antimicrobials and Carriage of Penicillin-resistant Pneumococci inChildren. Repeated cross-sectional studies covering 10 yearsThe copyright of this thesis rests with the author and no quotation from itor information derived from it may be published without the prior writtenconsent of the author.HáskólaútgáfanReykjavík 2006©Vilhjálmur Ari Arasone-mail: vilhjalmur.a.arason@fjordur.hg.isUmbrot: Þröstur HaraldssonPrentun og bókband: LeturprentISBN 9979-70-157-9ISBN 978-9979-70-157-6

ÁGRIPNotkun sýklalyfja og beratíðni penicillín ónæmrapneumókokka hjá börnum– Endurteknar þversniðsrannsóknir á 10 ára tímabiliVilhjálmur Ari ArasonHeimilislæknisfræði, Háskóla Íslands, Heilsugæsla höfuðborgarsvæðisins,Sólvangur og Fjörður, Hafnarfirði, Íslandi.Tilgangur: Að athuga notkun sýklalyfja meðal forskólabarna á Íslandiog meta hugsanlegt samband slíkrar notkunar við beratíðnipenicillín ónæmra pneumókokka í nefkoki þeirra.Efniviður og aðferðir: Upplýsingar voru fengnar hjá foreldrum ogúr sjúkraskrám heilsugæslustöðva um sýklalyfjaávísanir 2.612 barnaá aldrinum 1-6 ára sem bjuggu á mismunandi stöðum á landinu. Úrþessum hóp voru teknar nefkoksræktanir frá 2.486 börnum. Gerðarvoru þrjár þversniðsrannsóknir á sömu svæðum á 10 ára tímabili (I.hluti 1993, II. hluti 1998 og III. hluti 2003). Þátttökuhlutfall var frá75 til 88%. Einnig var unnið úr upplýsingum apóteka sömu svæðavarðandi 22.132 ávísanir á sýklalyf til inntöku (utan spítala) fyriralla aldurshópa árið 1993 og 15.153 ávísanir árið 1998.Aðal mælibreytur: Tíðni penicillín ónæmra pnemókokka í nefkokiog áhættuþættir berasmits, heildarnotkun sýklalyfja, notkun þeirravegna bráðrar miðeyrnabólgu (acute otitis media), væntingar foreldraog notkun hljóðhimnuröra.Niðurstöður:• Sýklalyfjaávísunum heimilislækna til barna fækkaði um 1/3á rannsóknartímabilinu. Munur var á ávísanavenjum læknamilli svæða, sérstaklega varðandi meðferð við bráðri miðeyrnabólgu.• Fylgni var á milli væntinga foreldra til sýklalyfjanotkunar ogávísana lækna á sýklalyf til barna eftir búsetu.• Yfir 30% barna á Íslandi fá hljóðhimnurör á fyrstu 6 aldursárunum.Á svæðum þar sem sýklalyfjanotkunin var mikil varmeiri notkun á breiðvirkum sýklalyfjum borið saman við hiniii

ABSTRACTUse of antimicrobials and carriage of penicillin-resistant pneumococciin children– Repeated cross-sectional studies covering 10 yearsVilhjalmur Ari ArasonDepartment of Family Medicine, University of Iceland, PrimaryHealthcare Centre of Solvangur and Fjordur, IS-220 Hafnarfjordur,Iceland.Objectives: The overall aim of this thesis was to analyse the use ofantimicrobials in pre-school children in Iceland and the connectionbetween such use and the carriage of penicillin-nonsusceptible pneumococci(PNSP).Study populations and methods: Prescription data and medicalhistories from 2,612 children, aged 1 to 6 years, living in differentgeographically well-defined study areas in Iceland, and nasopharyngealspecimens from 2,486 children were analysed in three crosssectionalstudies covering 10 years (Phase I 1993, II 1998, and III2003). Participation varied from 75% to 88%. Annual analysis oforal antimicrobial sales/prescriptions for whole communities (hospitaluse excluded) were based on 22,132 prescriptions in 1993, and15,153 in 1998.Main outcome measures: The prevalence and risk factors for nasopharyngealcarriage of PNSP, total antimicrobial use, antimicrobialuse for acute otitis media (AOM), parental expectations and tympanostomytube placements.Results:• Antimicrobial prescription rates among GPs diminished byabout 1/3 over the study period. Prescription habits variedgreatly between communites especially because of AOM.• Parents’ expectations of antimicrobial prescriptions were associatedwith the antimicrobial prescription rate in each area.• The cumulative prevalence of tympanostomy tube placementamong pre-school children is high in Iceland (over 30%). In

areas where the prescription rate was high, broad-spectrumantimicrobials were prescribed relatively more often than inother areas, and the tympanostomy tube placement rate wasincreasing (up to 44% of all children). In other areas, tympanostomytube rate among children deceased (down to 17%) atthe same time as antimicrobial use for AOM diminished.• There was a strong association between antimicrobial use onthe individual level and the nasopharyngeal carriage of PNSP.• PNSP, multiresistant, serotype 6B (phenotypically identical tothe Spain 6B -2 clone) appeared and disappeared over a 10-yearperiod, in communities with both high and low antimicrobialuse.Conclusions: There is a strong association between antimicrobialuse for individual children and the nasopharyngeal carriage of PNSP.Pneumococcus is acquired from other children, usually in day-caresettings and PNSP selectively colonised when receiving antimicrobials.Spread of novel resistant clones appears to be the main reasonfor marked changes in pneumococcal resistance rates in individualcommunities over time. Antimicrobial drug (over)use for AOM mybe associated with future episodes of AOM and tympanostomy tubeplacements.Key words: antimicrobial use, drug prescription, acute otitis media,children, antimicrobial resistance, penicillin-nonsusceptible pneumococci,clonal spread, Spain 6B -2, herd immunity, tympanostomytube placement, primary healthcare, general practice.vi

ACKNOWLEDGEMENTSI wish to express my sincere gratitude to all those who have madethis thesis possible. I especially want to thank:My supervisor Professor Jóhann Ágúst Sigurðsson, head of Departmentof Family Medicine, University of Iceland. Without hisexperience, enthusiasm, positive and encouraging attitude and patience,this thesis may never have come true. Our long co-operationhas developed into a good friendship.My other co-authors, Professor Karl G. Kristinsson, Dr. SigurðurGuðmundsson, Helga Erlendsdóttir, Guðrún Stefánsdóttir, AðalsteinnGunnlaugsson, Dr. Linn Getz and Professor Sigvard Mölstadfor valuable expertise and co-operation in the research.Professor emeritus Calle Bengtsson former head of the Departmentof Primary Healthcare, Gothenburg for his generous supportand enthusiasm in beginning writing the thesis.My colleagues and others at the Fjordur Healthcentre and SolvangurHealthcentre Hafnarfjordur for encouragement and help with mypatients.Special thanks to all the children who participated in the study,their parents, the general practitioners who assisted in the studyareas and to the staff of the Department of Clinical Microbiology,Landspitali University Hospital.Last but not least, my wife Ingibjörg Ásgeirsdóttir for supportingme so unselfishly and tolerating me all the time I have spent workingin this research last 15 years. Also my children, Ásgeir Snær and hiswife Eyrún, Jóhanna and her boyfriend Hördur, Ásta and my grandchildrenSteinn Andri, Hjördís María, Ingibjörg Svana and Emilíafor their patience and encouragement.This study was mainly supported by the Icelandic College ofFamily Physicians.It was also granted by The Research Fund of the University ofIceland, and the Research Fund of the Landspitali University Hospital,Reykjavik.vii

CONTENTSÁGRIP........................................................................................ iiiABSTRACT............................................................................... vACKNOWLEDGEMENTS....................................................... viiCONTENTS............................................................................... viiiLIST OF FIGURES AND TABLES .......................................... xiLIST OF PAPERS...................................................................... xviCONTRIBUTORS...................................................................... xviiABBREVIATIONS AND DEFINITIONS................................. xviiiINTRODUCTION...................................................................... 1Bacterial resistance to antimicrobials ................................... 2Biochemical processes behind bacterial resistance............... 3Streptococcus pneumoniae..................................................... 4Pneumocaccae vaccination.................................................... 5Penicillin resistance among pneumococci............................. 6Otitis media............................................................................ 6Acute otitis media and antimicrobial use .............................. 9Tympanostomy tube placements............................................ 10Background for a study of antimicrobial use in relation toresistant bacteria in Iceland.................................................... 11Sales statistics of antimicrobials....................................... 11Penicillin-resistant pneumococci in Iceland..................... 12RESEARCH QUETION AND AIM OF THE STUDY............. 14Main research question.......................................................... 14Aim of the study.................................................................... 14STUDY POPULATION............................................................. 16Demography of Iceland......................................................... 16Characteristics of the study areas........................................... 16Choice of study areas............................................................. 18Organisational structure of the healthcare service................. 19Details on data collection from the different areas................ 19Selection criteria for the study groups................................... 20Overview of the data presented in the thesis......................... 22METHODS................................................................................. 23Antimicrobial sales statistics ................................................ 23viii

Microbiology and nasopharyngeal sampling for pneumococci................................................................................. 23Information about infection disease history and socio-demographicfactors....................................................................... 24Statistical methods................................................................. 24Ethical considerations............................................................ 25RESULTS................................................................................... 26Sales statistics of antimicrobial use in communities (I, II).... 26Antimicrobial sales according to age, gender and timeof year (1997-1998) ........................................................ 26Type of antimicrobial drugs sales (1997-1998)................ 28Changes in antimicrobial sales for children between1993 and 1998................................................................... 28Antimicrobial use among pre-school children in thesampled groups (I, III, IV) .................................................... 29Main diagnoses when prescribing antimicrobials forchildren............................................................................. 31Antimicrobial use for acute otitis media........................... 31Predictors for antimicrobial prescribing for acute otitismedia................................................................................. 34Association between parental expectation and doctors’prescription habits for management of upper respiratorytract infections in children................................................ 35Tympanostomy tube placements (III, IV).............................. 36Association between tympanostomy placements and antimicrobialuse..................................................................... 38Effects of tympanostomy tubes on recent antimicrobialdrug consumption.............................................................. 38Antimicrobial resistance in pneumococci (I, II, V)............... 38Carriage of penicillin-nonsusceptible pneumococci(PNSP).............................................................................. 38Carriage of erythromycin-resistant pneumococci............. 40Penicillin-resistance among pneumococci and antimicrobialuse..................................................................... 41Associations with PNSP-carrying in children carryingpneumococci...................................................................... 43Risk of PNSP carriage after receiving antimicrobials forall children (i.e., not only those carrying pneumococci).. 45ix

LIST OF FIGURES AND TABLESFiguresFigure 1.Figure 2.Antimicrobial consumption in the Nordic countriesbased on total sales statistics from theMinistry of Health and Social Security, Iceland,and The Nordic Council on Medicine.................. 11Total sales of antimicrobial mixtures in Iceland1989-1997 based on sales statistics from theMinistry of Health and Social Security............... 12Figure 3. Main research question of the thesis.................... 14Figure 4.Hypothesised associations between the mainfactors studied in this thesis................................. 15Figure 5. The North-Atlantic countries............................... 16Figure 6. Study areas in Iceland ......................................... 17Figure 7.Figure 8.Figure 9.Figure 10.Incidence of antimicrobial prescriptions (informationfrom annual drug-store sales statistics)by age and gender in the 1998 study................... 27Antimicrobial use as number of defined antimicrobialdoses (DDD) per 1000 inhabitants per dayby gender and month in the 1998 study (informationfrom annual drug-store sales statistics).......... 27Antimicrobial use according to age groups in thestudy areas 1997-1998 (information from annualdrug-store sales statistics).................................... 28Yearly incidence of antimicrobial treatments perchild in relation to age in 1993, 1998 and 2003.. 29xi

cocci (PNSP) 1993, 1998 and 2003. Data fromantimicrobial sales statistics in study areas forchildren < 7 years old, 1992-1993 and 1997-1998, are also shown for comparison.................. 41Figure 20.Figure 21.Figure 22.Figure 23.Figure 24.Carriage rate of penicillin-nonsusceptible pneumococci(PNSP) of all children carrying pneumococci,1-6 years of age, related to time fromlast antimicrobial treatment (2-7 weeks or 8-52weeks) or no treatment in the studies in 1993,1998, and 2003..................................................... 45Adjusted odds ratio for carrying penicillin-nonsusceptiblepneumococci (PNSP) or not accordingto multivariate logistic regression analysis instudies in 1993, 1998 and 2003........................... 46Carriage rate of penicillin-susceptible (PSP) andpenicillin-nonsusceptible pneumococci (PNSP)by all children receiving antimicrobials duringthe 12 months prior to study entry for the 1993,1998 and 2003 studies, by the number of weeksfrom the last antimicrobial treatment................... 47Spread of different serotypes of penicillin-nonsusceptiblepneumococcus (PNSP) as carryingratio (%) of all pneumococci observed in thestudies in 1993, 1998 and 2003........................... 48The prevalence of penicillin-nonsusceptiblepneumococci (PNSP) of multiresistant serotype6B (the Spain 6B -2 clone) as a carriage rate of allpneumococci and use of antimicrobials in thesample groups, as observed in the study areasin the 1993, 1998 and 2003 studies. Data fromantimicrobial sales statistics in the study areasxiii

for children < 7 years old, 1993 and 1998 arealso shown for comparison.................................. 49Figure 25. a) Prevalence of penicillin-nonsusceptible pneumococci(PNSP) of multiresistant serotype 6B(recognised as the Spanish-Icelandic clone,Spain 6B -2), as a percentage of all children carryingpneumococci, observed in areas H, V, E andB in the studies in 1993, 1998 and 2003. b) Atheoretical model (epidemiological curves) forthe spread and disappearance of Spain 6B -2 clonein four communities in Iceland 1993-2003.......... 66Figure 26.Conclusions concerning potential associationsand their directions.............................................. 72TablesTable 1.Table 2.Table 3.Table 4.Temperature, humidity and wind speed duringthe years 1993, 1998 and 2003 in four researchareas in Iceland; Hafnarfjordur (H), Vestmannaeyjar(V), Egilsstadir (E) and Bolungarvik (B) 18Study population from phases II (1998) andIII (2003) and, for comparison, from phaseI (1993), where children from area HH andchildren

Table 5.Table 6.Table 7.Table 8.Table 9.Table 10.Parents’ views on appropriate antimicrobialtreatment as reported in questionnaires from the1998 and 2003 studies......................................... 35Odds ratio by multivariate analysis, adjusted forage, for children 1-6 years old having tympanostomytube(s) at present as opposed to not havingtube(s) in the 2003 study...................................... 37Prevalence of penicillin-nonsusceptible pneumococcias observed in the studies in 1993,1998 and 2003...................................................... 40Penicillin-resistant pattern for pneumococci inchildren in the 1993 study by age groups............ 40Number (No) of penicillin-susceptible (PSP)and nonsusceptible pneumococci (PNSP), whichare nonsusceptible (intermediate or resistant)to erythromycin (ERY), tetracycline (TET)chloramphenicol (CHL) and trimethoprim-sulfamethoxazole(SXT) according to disc diffusiontests, in 1993, 1998 and 2003, in respectivestudy areas........................................................... 42Odds ratio (OR) of carrying penicillin-nonsusceptiblepneumococci (PNSP) as opposed topenicillin-susceptible pneumococci by backward,stepwise, logistic regression method in thestudies in 1993, 1998 and 2003........................... 44xv xv

ContributorsPaper IVilhjalmur Ari Arason (VAA), Johann A Sigurdsson (JAS), Sigvard Mölstad andSigurdur Gudmundsson (SG) were responsible for the design of the study. VAAand JAS were responsible for recruitment and sampling. Gudrun Stefansdottir,Karl G. Kristinsson (KGK) and SG were responsible for the bacteriological studies.VAA and other authors were responsible for analysing the data. VAA wrotethe first draft of the paper and together with KGK, JAS and SG was responsiblefor writing the paper. All authors were responsible for editing the paper and wereinvolved in final approval of the paper. VAA and JAS are guarantors.Paper IIVAA, JAS, KGK and SG were responsible for the design of the study. VAA, AdalsteinnGunnlaugsson (AG) and JAS were responsible for recruitment and sampling.Helga Erlendsdottir (HE), AG and KGK were responsible for the bacteriologicalstudies. VAA and other authors were responsible for analysis of the results.VAA wrote the first draft and then VAA and KGK were responsible for writing thepaper. All were responsible for editing the paper and all were involved in finalapproval of the paper. KGK and VAA are guarantors.Paper IIIVAA and the other authors were responsible for the design of the study. VAA andJAS were responsible for recruitment and sampling. VAA and other authors wereresponsible for analysing the results. VAA wrote the first draft and VAA, JAS andSG were responsible for writing the paper. All authors were responsible for editingthe paper and were involved in final approval of the paper. VAA and JAS areguarantors.Paper IVVAA and the other authors were responsible for the design of the study. VAA andJAS were responsible for recruitment and sampling. VAA and the other authorswere responsible for analysing the results. VAA wrote the first draft and then VAA,JAS and Linn Getz were responsible for writing the paper. All authors were responsiblefor editing the paper and were involved in final approval of the paper.VAA and JAS are guarantors.Paper VVAA and the other authors were responsible for the design of the study. VAA andJAS were responsible for recruitment and sampling. HE and KGK were responsiblefor the bacteriological studies. VAA and the other authors were responsiblefor analysing the data. VAA wrote the first draft and then VAA and KGK were responsiblefor writing the paper. All authors were responsible for editing the paperand were involved in final approval of the paper. KGK and VAA are guarantors.xvii xvii

ABBREVIATIONS AND DEFINITIONSAbbreviationsAOM Acute otitis mediaB BolungarvikCI Confidence intervalDDD Defined daily doseE EgilsstadirG GardabaerGP General practitionerH HafnarfjordurHG Hafnarfjordur and GardabaerHH Hella and HvolsvöllurMIC Minimal inhibitory concentrationNS Not significantOR Odds ratioPNSP Penicillin-nonsusceptible pneumococciPSP Penicillin-susceptible pneumococciSD Standard deviationV VestmannaeyjarDefinitionsAntimicrobials = antibioticsStrain = serotypeClone = subtype (serotype) of a bacteria with the same DNA origin(fingerprint)DDD/1000/day = defined daily dose per 1000 individuals dailyHerd immunity = immunity status in the population against specificorganismsIntermediate-resistant pneumococci = penicillin MIC ≥ 0.1-1.0 mg/lMultiresistant (multidrug-resistant) = resistant to three or moredifferent antimicrobial groupsPenicillin-nonsusceptible pneumococci (PNSP) = penicillin MIC≥ 0.1 mg/lPenicillin-resistant pneumococci, MIC ≥ 2.0 mg/lPNSP carrying rate = percentage of PNSP of all carrying pneumococcixviii

INTRODUCTIONInfections have been one of the major causes of human disease andsuffering throughout history. The introduction of antimicrobials forbacterial infections, beginning in the 1930s, is clearly one of themilestones in the history of modern medicine (Le Fanu 1999). It hasbeen claimed that the use of antimicrobials has added approximately10 years to human life expectancy in many industrialised countries(McDermott and Rogers 1982). However, bacteria resistant to antimicrobialtreatments soon became a worldwide problem, probablypartly because of overuse of antimicrobial drugs (Tenover andHughes 1996; Wise et al. 1998).In contemporary Western societies, infections from the upper respiratorytract are one of the most common reasons for visiting a doctorin primary healthcare (Monto and Ullman 1974). This is especiallytrue regarding upper respiratory tract infections in children (McCaigand Hughes 1995; Söderström 1995; Njalsson et al. 1996; Petursson1996). Of particular concern in this connection has been the rapid increaseof antimicrobial resistance in the bacteria Streptococcus pneumoniae,causing problems in the management of common childhoodinfections, such as acute otitis media (Klugman 1990; Appelbaum1992; Neu 1992; Levy 1993; Tomasz 1994; Levy 1998; Dagan 2000).The prevalence of penicillin-resistant pneumococci is highest in countrieswith relatively unrestricted antimicrobial use. It has been low innorthern Europe except Iceland, which is disconcerting as antimicrobialuse in Iceland has been relatively restricted (Kristinsson 1995).This thesis is about the use of antimicrobials in children in the communityand the possible association of such with the risk of carriage ofpenicillin-resistant pneumococci, better defined as penicillin-nonsusceptiblepneumococci (PNSP). The emphasis is on acute otitis media,which is the main reason for prescribing antimicrobials in children.Furthermore, the spread of one specific PNSP clone over a 10-year periodin four well-defined communities in Iceland is examined. Finally,the thesis examines the tympanostomy tube placements as a treatmentoption for otitis media in association with antimicrobial use.

ß-lactamase enzymatically cleaves the four-membered ß-lactam ring,rendering the antibiotic inactive (ß-lactamase-producing bacteria Haemophilusinfluenzae and Moraxella catharralis). 3) Production of analternative target (usually an enzyme) that is resistant to inhibition bythe antimicrobial. 4) Bacteria protect themselves from antimicrobialsby preventing the antimicrobial from entering the cell or by pumpingit out faster than it can flow in. Bacterial resistance to macrolides canbe explained by the two last described pathways.Streptococcus pneumoniaeStreptococcus pneumoniae, usually named pneumococcus is one ofthe most clinically significant pathogens with emerging antibiotic resistance.It was first isolated by Pasteur in 1881 and has been observedto have been the most common reason for lobar pneumonia, with veryhigh mortality (33%) before antimicrobial treatment was available.After the introduction of sulphonamides, the mortality decreased to8%, and after the introduction of penicillin, mortality has been verylow (Swartz 2002). Pneumococcus, is at present, considered to be thecommonest and most important pathogen in acute otitis media, acutesinusitis, pneumonia, septicaemia and meningitis (Musher 1992). Therisk, especially of the invasive disease, is higher for children and theelderly (Burman et al. 1985). The main habitat of pneumococcus is thenasopharynx. Pneumococcal carriage is age-related. It increases duringthe first year of life and is highest in children aged 1-2. Thereafter,carriage rates slowly decline, and adults have much lower rates thanchildren (Gray et al. 1980). Colonised children may transmit pneumococcieasily to each other.An essential immunogenic determinant of pneumococci is itscapsule made of polysaccharide, which provides protection fromphagocytosis. Thus, non-encapsulated strains have less protectionand, thereby, have also greatly reduced virulence (Tuomanen et al.1995; Hall et al. 1996). The antigenicity of the capsule forms thebasis for the classification of the 90 known pneumococcal serotypes(Henrichsen 1995; Hall et al. 1996). If sub-typing of the pneumococcusis possible, the number assignment is referred to as a serogroup,e.g., serogroup 6, with subtypes referred to as serotype or subtype6A, 6B, etc. The host’s protective antibodies are directed against the

polysaccharide capsule, and the protection is therefore type-/groupspecific,with only slight or no cross-reactivity between antibodies ofdiffering type/serogroup specificity.Pneumococcae vaccinationVaccination against pneumococci with polysaccharide vaccine has beenavailable on the market since 1977, but the immunogenicity of polysaccharidevaccines, especially among children, is low (King et al. 1996).New protein-polysaccharide conjugate vaccine, including serotypes 4,6B, 9V, 14, 18C, 19F and 23F, has much higher immunogenicity amongchildren and has been available on the market since 2000 and is part of theroutine childhood immunization schedule in the United States (MMWR2000). Clinical trials have shown efficacy of the vaccine against serotype-specificinvasive disease of > 70% (Whitney 2005). Among childrenunder two years of age, the rate of all PNSP invasive diseases hasdiminished by about 80% in the United States from 1999 to 2004 (Kyawet al. 2006). Studies evaluating pneumococcal conjugate vaccines effectson nasopharyngeal carriage demonstrate though that vaccinationdoes not impact the overall risk of pneumococcal nasopharyngeal colonizationbut reduces the acquisition of vaccine-type strains and increasesthe risk of non-vaccine serotype strain acquisition (O’Brien and Dagan2003; Veenhoven et al. 2003). The natural balance of microbial speciesin the nasopharynx might also be altered by pneumococcal vaccination.In studies from the Netherlands, there was a negative correlation for cocolonisationof Staphylococcus aureus and vaccine-type pneumococci,findings suggesting a natural competition between these bacteria, whichmight also explain an increase in Staphylococcus aureus-related otitismedia after vaccination (Bogaert et al. 2004).In Northern California, it has been shown that in those receivingthis vaccination there was an 8% reduction in otitis media episodes,a 10% reduction in frequent otitis media and a 24% reduction intympanostomy tube placements compared with children receivingcontrol vaccine (Fireman et al. 2003). Other studies from the North-America, Israel and Europe (Finland) have also evaluated the effectof pneumococcal conjugate vaccines on clinical or culture-provedpneumococcal otitis media with similar results (Black et al. 2000;Dagan et al. 2001 a; Eskola et al. 2001).

tive impact on the quality of life of children and worries their caregivers(Brouwer et al. 2005). The parents of young children holdviews on acute otitis media and antibiotics that differ markedly fromthe medical model in Iceland (Jonsson and Haraldsson 2002). Theseoutcomes should therefore be included in the evaluation of the childwith otitis media in both the clinical and research setting.Acute otitis media and antimicrobial useAcute otitis media is the most common diagnosis (30-65%) leading toantimicrobial prescription for children in the Western world (McCaigand Hughes 1995; Arason et al. 1996; McCaig et al. 2002; Arasonet al. 2002 b; Rovers et al. 2004; Arason et al. 2005). Nevertheless,antimicrobial treatment of acute otitis media is debatable. Several randomisedclinical trials (Damoiseaux et al. 2000; Little et al. 2001; LeSaux et al. 2005; McCormick et al. 2005) and meta-analyses (Rosenfeldet al. 1994; Del Mar et al. 1997; Takata et al. 2001; Glasziou et al.2004) indicate that antimicrobial treatment of acute otitis media mayoften be unnecessary, even for young children. A restrictive antibioticpolicy for acute otitis media appears therefore justifiable, and the recentemphasis in Iceland as well as elsewhere has been on watchfulwaiting for management of children with acute otitis media, especiallyfor those two years and older with mild symptoms or with uncertaindiagnoses (see the Icelandic drug guidelines, at http://landlaeknir.is/template1.asp?PageID=672, last viewed in February 2006). In general,the literature lacks studies comparing antibiotic treatment withplacebo administration for acute otitis media and there are no clinicaltrials using standardised methods for assessing acute otitis mediaseverity. Restrictive policy in antimicrobial use is supported by thedocumented link between high consumption of antimicrobials and thedevelopment of antimicrobial resistance among common pathogensin the community (see chapter “Bacterial resistance to antimicrobials”above). A strong association between antimicrobial use for acute otitismedia specifically and carriage of penicillin non-susceptible pneumococciin children has also been demonstrated (Dagan et al. 1998 a;Arason et al. 2002 a; Brook and Gober 2005; McCormick et al. 2005).The increasing rate of resistance to antibiotic drugs is, as a consequence,associated with a decrease in the rate of successful eradica-

10tion of pathogens from middle-ear fluid in acute otitis media, whichis associated with clinical failure (Dagan 2000). Further knowledge ofthe short- and long-term impact of different antimicrobial treatmentstrategies for acute otitis media is therefore important.Healthcare systems, health-seeking behaviour, and medical managementincluding management, and treatment decision for acuteotitis media, differ worldwide. Therefore, when comparing the prevalenceof antimicrobial treatments for acute otitis media, it is necessaryto adjust for baseline characteristics between countries (Froomet al. 2001). Furthermore, consistency in the treatment pattern withinthe same practice or healthcare centre in one community is also morelikely than that between communities (Diwan et al. 1992; Petursson1996; Gabbay and le May 2004).Acute otitis media was known to be one of the most commoncauses of antimicrobial use in children in Iceland when the study wasconducted (Bjarnason 1991; Petursson 1996), and pneumococcus isknown to be the most common cause, accounting for approximately50 percent of all cases of acute otitis media (Bluestone 1996; Dowellet al. 1999). One of the most common serotype comprising pneumococcalisolates from middle-ear fluid samples include serotype 6B(Hausdorff et al. 2002). This is the main reason why prescriptions foracute otitis media in different communities and the resistance patternof pneumococcus are the focus of our studies.Tympanostomy tube placementsTympanostomy tube placement is a well-established treatment optionfor chronic effusion in the middle-ear and recurrent episodes of acuteotitis media, yet the consequences of this intervention are not alwaysclear (Gates et al. 1987; Franklin and Marck 1998; Rosenfeld 2000;Lous et al. 2005; Paradise et al. 2005; Rovers et al. 2005). Tube otorrhea,often in combination with acute otitis media, is a common andoften recurrent and/or stubborn problem in young children who haveundergone tube placement for persistent middle-ear effusion (Ah-Tyeet al. 2001). No previous data were available about the prevalence oftympanostomy tube among Icelandic children before the present study.This information should also indicate, at least partly, the prevalence ofotitis-prone children in Iceland. Even though there are some clinical

trials indicating lower antimicrobial treatment frequencies after tubeplacements (Franklin and Marck 1998), there is a lack of epidemiologicalstudies showing positive effects in diminishing antimicrobialuse among children in the community by using tubes on a bigger scaleamong (all) otitis-prone children. This was one reason to include tympanostomytube placements in our research.Background for a study of antimicrobial use in relation to resistantbacteria in IcelandSales statistics of antimicrobialsAntimicrobials are commonly used, as can be seen from sales statistics.Figure 1 shows the sales of antimicrobials in the five Nordiccountries. Based on these figures, the use of antimicrobials is high andhad been much higher in Iceland than in the other Nordic countriesbefore the study period. Of special interest was the rapidly increasinguse of trimethoprim-sulfamethoxazole (trim-sulfa.) in the early 90s(Fig. 2), which was commonly used for acute otitis media.DDD/1000 inhabitants/day251120151050IcelandDenmarkNorwayFinlandSweden1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004Fig. 1. Antimicrobial consumption in the Nordic countries based ontotal sales statistics from the Ministry of Health and Social Security,Iceland, and The Nordic Council on Medicine (data from Denmarkdo not include hospital usage).Year

12DDD/year35,00030,00025,00020,00015,00010,0005,00001989 1990 1991 1992 1993 1994 1995 1996 1997amoxicillin±clavulanic acidpenicillin Vcloxacillincephalosporintrim-sulfamacrolidesFig. 2. Total sales of antimicrobial mixtures in Iceland 1989-1997based on sales statistics from the Ministry of Health and Social Security.Penicillin-resistant pneumococci in IcelandAnother reason for studying the association between the use of antimicrobialsand the appearance of antimicrobial-resistant bacteria inIceland was that a new PNSP appeared in Iceland in the late 1980s,causing clinical problems and a risk of treatment failure, especiallywhen treating children for acute otitis media caused by these pneumococci.The first case of antimicrobial-resistant pneumococcus in Icelandwas observed in 1988 and in the next years proved to be mainlya multiresistant serotype 6B strain (Kristinsson et al. 1992), probablycoming from Spain, where this tribe, now registered as Spain 6B -2, hadpreviously been observed (Soares et al. 1993). Later on it was shownthat the prevalence of this particular strain (clone) increased rapidlyin Iceland (Vilhelmsson et al. 2000; Sa-Leao et al. 2002). When thisstudy started, cultivation of bacterial sampling from hospital seriesindicated a PNSP prevalence rate of about 20%, almost all of thembeing multiresistant serotype 6B (Kristinsson 1995). The prevalencein the community was at that time not known.

It has been previously pointed out, that there has been lack ofpopulation studies, based on studies of both accurate antimicrobialsales statistics and antimicrobial resistance in the community (Wiseand Andrews 1998; Felmingham et al. 2005). A study of antimicrobialconsumption and antimicrobial resistance in Iceland was thereforeconsidered propitious for several reasons:• The study could be carried out in well-defined geographicalareas.• Computerised medical records were available and had beenused for several years.• Computerised sales records for drug sales were available fromthe pharmacies.• Areas could be studied where there was only a single primaryhealthcare centre in each community, to which the vast majorityof subjects with upper respiratory tract infections turned.• The personnel working at the primary healthcare centres arestable.• The GPs have an international view, as the vast majority ofIcelandic GPs have been educated abroad in different parts ofthe world.13

14RESEARCH QUESTION AND AIM OFTHE STUDYMain research questionThe main question of this study was the potential association betweenthe use of antimicrobials outside hospitals and the developmentand spread of antimicrobial-resistant bacteria, mainly Streptococcuspneumoniae, in the community (Fig. 3).Antimicrobial usein the communityAntimicrobial resistancein the communityFig. 3. Main research question of the thesis.As mentioned above, one of the most common reasons for prescribingan antimicrobial is middle-ear infection (acute otitis media)in children. This was a reason to confine our 1998 and 2003 studies(phase II and III) to pre-school children, 1-6 years of age, and toinclude the occurrence of acute otitis media as a main reason forantimicrobial usage and use of tympanostomy tubes as a well-establishedtreatment option for recurrent episodes of acute otitis media,in the study plan. Most pre-school children one year of age or older(about 80%), are enrolled at day-care centres and were therefore easilyavailable for possible participation.Figure 4 includes the main potential associations being focusedon in our studies.Aim of the studyIn summary, the overall aim was to analyse the use of antimicrobialsand the reasons (main diagnosis) for prescribing antimicrobials,on one hand, and carriage of penicillin-nonsusceptible pneumococci(PNSP), on the other, in pre-school children in Iceland.

15Acute otitismediaAntimicrobialuseAntimicrobialresistancedevelopmentamongpneumococci(spread/selection)TympanostomytubeplacementFig. 4. Hypothesised associations between the main factors studiedin this thesis.Specific aims• To describe the total use of antimicrobials in the communities,specifically among pre-school children, by class of antimicrobials,amount prescribed and prescription rate in selected,well-defined communities.• To describe potential links between antimicrobial treatmentfor acute otitis media, socio-demographic factors and parentalviews on the use of antimicrobials.• To describe the use of tympanostomy tube placements and possibleassociation with the use of antimicrobials among children.• To analyse associations between antimicrobial use and nasopharyngealcarriage of PNSP in children with regard to bothindividual use and total use in the community.• To describe clonal spread of PNSP in communities and to analysethe interplay of factors contributing to this spread.

16STUDY POPULATIONSDemography of IcelandIceland is a volcanic island in the North Atlantic Ocean (Fig. 5), justsouth of the Arctic Circle, with an area of 103,000 km 2 and 299,891inhabitants at the end of 2005. The population is limited to a narrowcoastal belt, and most of the people live in and around the capital,Reykjavik, on the south-west coast. Beginning in the Caribbean andending in the North Atlantic, the Gulf Stream plays an important rolein the pole-ward transfer of heat and salt surrounding Iceland. Theclimate is characterised by a relatively small difference in temperaturebetween summer and winter, an oceanic climate.Fig. 5. The North-Atlantic countries.Characteristics of the study areasThis thesis is based on studies from five areas (Fig. 6). These areHafnarfjordur and Gardabaer (HG, when both communities representone study area with a common off-hours service in phase I,but H, when Hafnarfjordur alone represented the same study area in

17Fig. 6. Study areas in Iceland.phases II and III), Vestmannaeyjar (V), Egilsstadir (E), Bolungarvik(B) and Hella and Hvolsvollur (HH, only included in phase I).Hafnarfjordur (H) and the smaller neighbour town Gardabaer (G)are adjacent to the capital Reykjavik. The town of Vestmannaeyjar(V) is a fishing centre on an island off the south coast. Egilsstadir (E)in East Iceland, and the smaller town Hella/Hvolsvollur (HH) in thesouthern part are surrounded by large farming areas. Bolungarvik(B) is a small fishing town in north-west of Iceland. The climate inVestmannaeyjar (V) is described as somewhat warmer and windierthan in other parts of Iceland, whereas Egilsstadir (E) is morecharacterised by a climate closer to some parts of Scandinavia, withcolder winters, less humidity and warmer summers than elsewherein Iceland. Classical weather parameters for the study areas as wellas the years of the three phases during the 10-year period are shownin Table 1 (The Icelandic Meteorological Office http://www.vedur.is, last viewed February 2006). The weather parameters shown didnot differ much between the research areas during the study period,except for more mean wind speed in Vestmannaeyjar than observedin the other study areas.

18Table 1. Temperature, humidity and wind speed during the years 1993, 1998 and2003 in four research areas in Iceland; Hafnarfjordur (H), Vestmannaeyjar (V),Egilsstadir (E) and Bolungarvik (B) (ND = no data available).Area Year Temperature, degrees Celsius.Mean (range)RelativehumidityMean windspeed. Metres/secondJanuary July Jan. July Jan. JulyH 1 1993 -2.3 (-12.7 to 6.8) 10.1 (4.7 to 19.7) 76.9 75.0 6.7 4.61998 0.6 (-13.7to 8.8) 11.1 (5.4 to 18.0) 73.8 78.9 5.7 3.82003 1.5 (-11.3 to 9.1) 12.3 (6.8 to 18.7) 76.7 79.5 4.7 2.6V 2 1993 -0.2 (-12.2 to 7.2) 9.3 (4.8 to 15.9) 76.2 80.2 13.0 9.01998 2.6 (-9.3 to 7.7) 10.4 (6.4 to 17.0) 77.6 88.3 9.4 6.62003 3.1 (-4.4 to 8.2) 11.4 (7.1 to 20.0) 79.8 88.6 12.9 7.5E 1993 -4.5 (-18.6 to10.0) 7.5 (3.5 to 14.5) 89.5 86.6 6.6 5.21998 3 -1.1 (-18.8 to 8.4) 8.4 (-0.9 to 25.2) 90.1 ND 6.7 ND2003 3 -2.7 (-19.9 to 7.2) 11.1 (2.5 to 22.1) ND ND ND NDB 1993 4 -3.2 (-17.0 to 7.1) 7.0 (3.3 to 15.2) 73.6 84.7 7.7 5.01998 -0.3 (-11.2 to 8.0) 8.8 (2.5 to 17.0) 79.4 79.1 7.9 3.82003 1.0 (-7.9 to 9.2) 10.3 (3.5 to 18.0) 78.8 80.7 5.7 4.41Reykjavík station, 2 Stórhöfdi station (on Heimaey, Vestmannaeyjar), 3 Egilsstada airport in July1998 and 2003, 4 Galtarviti station (15 km from Bolungarvík) in 1993.Choice of study areasThe reasons for selecting study areas vary. They were selected to representrural (B, E, HH and V) and urban (H, HG) areas. These areas are alsogeographically well-defined, evenly distributed around the country andhave reliable registers of all inhabitants, based on the National Register“Statistics Iceland” (http://hagstofan.is/, last viewed in February, 2006).The primary healthcare centres in areas H, B and E had well-establishedteaching practices, and the content of care in these practices had alsobeen well documented from previous research (Sigurdsson et al. 1989;Njalsson et al. 1996; Halldorsson et al. 2002; Petursson 2005 a ).The five study areas corresponded to seven communities, eachserved by one primary healthcare centre, where GPs and other staffare responsible for all primary healthcare, including on-call servicesnight and day, throughout the year. The medical records in allthese primary healthcare centres have long been computerised. The

healthcare centre in area H was the author’s own workplace duringall phases of this study.This study is an epidemiologic cross-sectional follow-up study. Inanalyses of individuals (randomised trials), the basic assumption is thatthere are no connections between the outcome for one person and thatof any other person (Campell et al. 1999). When analysing GPs prescriptionhabits or practices, it is more likely that the outcome for manypatients will have a similar pattern if they are treated by the one and thesame physician. Furthermore, it is more likely that there is a consistenttreatment pattern within the same practice or healthcare centre than betweenpractices and healthcare centres (Diwan et al. 1992; Gabbay andle May 2004; Petursson 2005 a). The study areas were therefore feasibleto examine differences in medical praxis in the primary healthcare inIceland in connection with antimicrobial prescription habits.Organisational structure of the healthcare serviceThe main organisational structure of the healthcare service was byand large similar during the 10-year study period. There is direct accessto all doctors in Iceland, and GPs therefore have no gate-keepingrole as they do in some other countries. The same otolaryngologyspecialist visited areas V, E and B bi-monthly during the years 1998and 2003, a fact which may be taken into consideration when dealingwith the results described in Papers III and IV. The study areaswere served by a total of 19 GPs (18.2 positions) in 2003, of whom11 were the same individuals as in the 1998 study, and 8 were thesame individuals as in the 1993 study. As areas H and G are suburbsof the capital Reykjavik, the inhabitants in these areas had easy accessto their GPs as well as to other specialists in Reykjavik. In thisrespect there was no change for H during the study period. However,some other changes took place in area H that may have affected theresults of our study. After phase II, off-hours service for children wasprovided more often outside the H area, resulting in some decline inthe continuity of care in area H and, consequently, probably someunderestimation of antimicrobial prescribing.Details on data collection from the different areasThe cross-sectional investigations were carried out in three phases: 1992-19

201993, 1997-1998 and 2003. Sales statistics over 12 months, based oncomputerised data on prescriptions from the local pharmacies were collectedseparately in the first phase from October 1992 to September 1993and in the second phase from May 1997 to April 1998. No prescriptiondata on sales statistics were collected during the third phase of the study.In the first phase, nasopharyngeal specimens were collected fromOctober 1992 to November 1993, excluding the months of June, Julyand August. In phases II and III the collection was made during themonths March to May in 1998 and 2003, respectively, as was theadministration of questionnaires. In the third phase, otoscopy wasperformed if the child’s records indicated tympanostomy tubes. Asmost contacts with the participants in 1992-1993 were made in 1993(~90%), and all contacts in the second and third phases were madein 1998 and 2003, the three phases will hereafter be referred to as the1993, 1998 and 2003 studies, respectively.Three communities Gardabaer (G) (population 7,493) and Hellaand Hvolsvollur (HH) (population 3,150), were only included in the1993 study (I). This means that the cross-sectional follow-up includesfour well-defined communities: Hafnarfjordur (H), Vestmannaeyjar(V), Egilsstadir (E) and Bolungarvik (B). Gardabaer (G) wasexcluded from the 1998 and 2003 studies for practical reasons, andHella and Hvolsvollur (HH) because no data from the local pharmacycould be obtained in 1992-1993. An overview of the studypopulation and participation is given in Table 2.Selection criteria for the study groupsIn all phases of the study, children receiving antimicrobials in thepreceding two weeks were excluded as far as the analysis of nasopharyngealspecimen sampling was concerned, as shown in Tables2 and 3. The 1993 study (I) referred mainly to children up to sevenyears of age (thus also including those less than one year of age) whowere visited at day care centres on given days or went to the primaryhealthcare centres to visit a doctor for vaccination or because of anacute, unspecified upper respiratory infection (common cold), whilethe 1998 studies (II-III) and those in 2003 (IV-V) were supposed toinclude children representative of all 1- 6 years old children living inthe study areas. In the 1998 studies (II, III), there was a computerised

Table 2. Study population from phases II (1998) and III (2003) and, for comparison,from phase I (1993), where children from area HH and children

22Table 3. Details on data collection from the different areas.Type of data Areas AgesPrescription datafrom pharmaciesPrescription datafrom parents andmedical recordsData from nasopharyngealbacteriasamplingData from questionnaireon parentalviewData on acute otitismedia and tympanostomytubesHG (1993),H (1998), V,E, and BHG (1993),H (1998,2003), V, E,and B, HH(only 1993)HG (1993),H (1998,2003), V, E,and B, HH(only 1993)StudypopulationStudyyearPapernumberAll ages 34,582 1993 I27,013 1998 II0-6 years 919 1 1993 I1-6 years 804 (743) 1998 III (II)1-6 years 889 (824) 2003 IV (V)0-6 years 919 1 1993 I1-6 years 743 1998 II1-6 years 824 2003 VH, V, E, B 1-6 years 804 1998 III1-6 years 889 2003 IVH, V, E, B 1-6 years 804 1998 III1-6 years 889 2003 IV1Of these, 791 children were 1-6 years old when area HH was excluded; they were therefore comparablein age to the children studied in phases II and III in 1998 and 2003 (see Table 2.).random sample comprising children, 1-6 years of age from all thestudy areas; it was drawn from the National Registry, “Statistics Iceland”,while in 2003 the sample was a random sample of children, 1-6 years old, from Hafnarfjordur and including all available childrenof those ages from the other areas.Overview of the data presented in the thesisTable 3 summaries the different sources of data presented in this thesis.Table 2 gives an overview of the study areas, ages and numbersof participants in the three examination phases described in the differentPapers. The lower number of the participants in Tables 2 and3, representing Papers II and V is due to the exclusion of 61 childrenfrom the nasopharyngeal bacteria sampling because of antimicrobialtreatment during the preceding 14 days in the 1998 study, and 65children being excluded from the 2003 study for the same reason.

METHODS23Antimicrobial sales statisticsIn the 1993 and 1998 studies (I, II) computerised information ontotal sales of oral antimicrobials prescribed during one year for allinhabitants, adults as well as children, was collected from the localpharmacies (not hospital use) in the four areas HG (1993), H (1998),V, E and B. No data on prescriptions were available from the localpharmacy in area HH. Numbers of defined daily doses (DDD) werecalculated per 1000 inhabitants per day (WHO 1992).Microbiology and nasopharyngeal sampling for pneumococciNasopharyngeal samples were obtained with rayon tipped swabs andstored for a maximum of 48 hours until being processed in the microbiologylaboratory of the University Hospital. They were theninoculated on blood and chocolate-blood agar and incubated aerobicallyand anaerobically in 1993 and 1998, but only anaerobically in2003.Pneumococci were identified by conventional methods andscreened for penicillin resistance by the oxacillin disc diffusion testaccording the Kirby-Bauer method 1993 (Ruoff 1995; Woods andWashington 1995) and according to the NCCLS method and criteriain the studies performed in 1998 and 2003 (Jorgensen et al.1999).The minimal inhibitory concentration was determined by the agardilution method 1993 (Woods and Washington 1995) and by E-test(Tenover et al. 1996) in 1998 and 2003, according to the manufacturer’srecommendations (AB Biodisk, Solna, Sweden). The pneumococcicolonies were also screened for susceptibility to tetracycline,erythromycin, chloramphenicol and trimethoprim-sulfamethexazole.In 2003 clindamycin was added to this screening procedure.Penicillin non-susceptible isolates were also serotyped by co-agglutination(Kronvall 1973) using antisera from the State Seruminstitute(Copenhagen, Denmark). Further details about the identificationof bacteria, the screening for antimicrobial resistance, laboratorymethods and standards are given in Papers I, II and V.

24Information about infectious disease history and socio-demographicfactorsIn the 1993 study (I) parents completed a questionnaire. The questionnaireincluded questions about demographic factors, the number ofchildren in the household, whether the children were enrolled in a daycare centre, the number of oral antimicrobial prescriptions during thepreceding year, including not only prescriptions made by their GP´sbut also those made by other specialists, the date and name of thelast antimicrobial agent, type of infection and whether the child hadbeen taking prophylactic antimicrobials for three weeks or more in thepreceding year. The information collected from parents was matchedwith that available from the medical records at the local healthcarecentre. Parental information was used when medical records could notbe traced, especially when children had been seen by other professionalsoutside the study areas (around 5% of the cases).In the 1998 and 2003 studies the parents of the participating childrenreceived postal questionnaires, asking the same questions as inthe 1993 study, with additional questions about both past and presentuse of tympanostomy tubes. In 2003, there were also additionalquestions about smoking in the household. Parents were also askedto complete a questionnaire about their personal preferences regardingantimicrobial treatment in the case of 1) unspecified upper respiratoryinfections (common cold) and 2) acute otitis media. Parentsanswered the question whether it was always, sometimes or neverappropriate to give antimicrobials in these two situations, or whetherthey did not know. They were then asked to agree, disagree or giveno comment (or answer “do not know”) to the following two statements;“Some pathogens are becoming resistant to antimicrobials”and “Inappropriate antimicrobial use can lead to antimicrobial resistanceproblems with common pathogens”.Statistical methodsCarriage of penicillin-nonsusceptible or penicillin-susceptible pneumococciwas the most important single outcome variable in Papers I,II and V. Carriage of erythromycin-resistant pneumococci or erythromycin-susceptiblepneumococci was also an outcome variable inPaper V. Antimicrobial treatment or not for acute otitis media and

the presence or history of tympanostomy tube placements or notwere the outcome variables in Papers III and IV. Recent (< 8 weeks)antimicrobial use for acute otitis media or not for children havingtympanostomy tubes or not, adjusted for age, were also outcomevariables in Papers III and IV.The Pearson chi-square test or Fisher´s exact test was used forunivariate analysis of categorical variables and one-way ANOVA forcontinuous variables. The multivariate logistic regression methodwas used to estimate the risk for all variables potentially contributingto antimicrobial resistance (I, II and V), antimicrobial treatmentfor acute otitis media (III, IV), presence of tympanostomy tube(s)(III, IV), and parental willingness to accept antimicrobial treatmentfor the common cold (III) in order to control interdependence. Individualregression coefficients were tested with the Wald statistic, andconfidence intervals were calculated for the odds. All analyses wereperformed with the SPSS® program for Windows (Advanced StatisticsRelease 6.0 (1993) and 8.0 (1998 and 2003) SPSS Inc, Chicago,IL). Linear regression analysis was used to estimate correlation coefficient(r), and the 95% confidence interval for the slope of the meannumber of antimicrobial courses for acute otitis media compared tothe tympanostomy tube placement rate (cumulative rate) by areas(IV). Linear regression analysis was also used to estimate the correlationbetween the mean number of total antimicrobial courses andthe prevalence of parents finding it appropriate to sometimes treatcommon colds with antimicrobials (IV).The level of statistical significance was set at 0.05, and 95% confidenceintervals were given. Further information about statisticalmethods is given in the separate Papers, I-V. Statistical assistancewas provided by Júlíus Björnsson and Örn Ólafsson, LandspitaliUniversity Hospital, Reykjavik.Ethical considerationsThe 1993 study was approved by the Ethics Committee of the Directorateof Health. The 1998 and 2003 studies were approved by theNational Bioethics Committee and National Data Protection Commission,Iceland. Data on individuals were only collected if the parentshad given consent for the participation of their children.25

26RESULTSSales statistics for antimicrobial use in communities (I, II)The total antimicrobial use during one year in the communities, includingall ages, was gathered in the 1993 and 1998 studies. A totalof 22,132 prescriptions were dispensed by local pharmacies in the1993 and 15,153 in 1998. The calculated amount used in terms of thenumber of defined daily doses (DDD) per 1000 inhabitants per dayis shown in Table 4.Table 4. Antimicrobial use 1993 and 1998according to sales statistics, measured asthe number of defined daily doses (DDD)per 1000 inhabitants per day in the studyareas.Number of DDD/1000/dayStudy area 1993 1998H 13.6 1 14.2V 19.9 17.2E 16.7 12.3B 13.6 11.21Together with Gardabaer in the 1993 studyAntimicrobial sales according to age, gender and time of year(1997-1998)When antimicrobial use is analysed as the rate of prescriptions in the1998 study (Fig. 7), the highest incidence of prescriptions is amongpre-school children. Women used more antimicrobials than men and,as shown in Figs. 7 and 8. Most antimicrobial use was during thewinter (Fig. 8).Fig. 7. Incidence of antimicrobial prescriptions by age and gender inthe 1998 study (information from annual drug-store sales statistics).Fig. 8. Antimicrobial use as number of defined antimicrobial doses(DDD) per 1000 inhabitants per day by gender and month in the1998 study (information from annual drug-store sales statistics).

27Number of antimicrobial prescriptions per inhabitant per year1.41.21.0MenWomen0.80.60.40.20.00 to 45 to 910 to 1415 to 1920 to 2425 to 2930 to 3435 to 39Fig.7 (above) and Fig. 8 (below). See text on opposite page.DDD/1000 inhabitants/day2540 to 4445 to 4950 to 5455 to 5960 to 6465 to 6970 to 7475 to 7980 to 8485+Age groups201510Men5Women0MayJuneJulyAugustSepOctNovDecJanFebMarchApril

28Type of antimicrobial drug sales (1997-1998)The types of drugs prescribed varied according to age. In the youngestage group, amoxicillin and amoxicillin plus clavulanic acid werethe most common drugs used, whereas tetracycline dominated in theteenage groups (Fig. 9). No big difference was observed betweenareas in the 1997-1998 study when types were analysed as a percentageof all antimicrobials prescribed. No difference was observed bygender and the type of drug prescribed.Changes in antimicrobial sales for children between 1993 and1998In Paper II, antimicrobial sales for children < 7 years old between1992-1993 (6,223 prescriptions) (I) and 1997-1998 (3,347 prescriptions)were compared for each area studied. The number of defineddaily doses/1000 children/day and the number defined daily dosesper prescription were calculated, for both the total use and each antimicrobialgroup specifically. Antimicrobial use had diminished inDDD/1000 inhabitants/day987654321098765432100-6 years old14-20 years old987654321098765432107-13 years old21 years and olderpenicillin Vtetracyclineamoxicillin±clavulanicacidtrim-sulfamacrolidesothersFig. 9. Antimicrobial use according to age groups in the study areas1997-1998 (information from annual drug-store sales statistics).

all study areas in terms of both as number of defined daily doses (14-43%) and the number of antimicrobial treatment courses per year(9-50%). The reduction in antimicrobial use was greater for trimethoprim-sulfamethoxazolethan for other antimicrobials, in one area(area V) dramatically or from 7.1 to 1.4 DDD/1000 children/day (II)(see also Fig. 2). Overall, there was no change in the number of defineddaily doses per prescription between these two periods (II).Antimicrobial use among pre-school children in the sampledgroups (I, III, IV)The use of antimicrobials was commonest in the youngest children,as shown in Figure 10. The use was statistically lower in 1998, 1.21antimicrobial treatments per child per year (95% CI 1.09-1.32) and2003, 1.06 (0.95-1.17) than during the first study period, 1993, 1.51(1.39-1.63) but the difference between children of the same age wassimilar in the three studies.Although the number of antimicrobial courses prescribed for preschoolchildren per year, as observed in the sampled children 1-6 years29Number3.02.52.01993199820031.51.00.50.012 3 4 5 6Age in yearsFig. 10. Yearly incidence of antimicrobial treatments per child inrelation to age in 1993, 1998 and 2003.

302.52.01.51.00.50.02.52.01.51.00.50.0HafnarfjordurEgilsstadir2.52.01.51.00.50.01993 1998 2003 1993 1998 2003These graphs show the number of antimicrobial treatments/child/yearVestmannaeyjarBolungarvik2.52.01.51.00.50.01993 1998 2003 1993 1998 2003Fig. 11. Yearly incidence of antimicrobials among children 1-6 yearsof age in different study areas in the 1993, 1998 and 2003 studies.of age, diminished during the 10-year period by about one third, itvaried between study areas (Fig. 11). This time trend was of statisticalsignificance for all areas except for Vestmannaeyjar (area V).Amoxicillin was most commonly the last antimicrobial drug prescribedbefore children entered the study in all three studies (1993,1998 and 2003), as shown in Figure 12. In the 1993 study, the useof trimethoprim-sulfamethoxazole was common (I) but diminisheddramatically in the 1998 study (II) and further still in the 2003 study(V), as also shown in Figure 2 (Total sales of antimicrobial mixturesin Iceland 1989-1997, based on sales statistics from the Ministry ofHealth and Social Security). The choice of antimicrobial drugs alsovaried considerably by study area. In 2003, broad-spectrum antimicrobials(amoxicillin+clavulanic acid, azithromyzin, erythromycin,trimethoprim-sulphamethoxazole) were used in only 23 out of 72cases (32%) in area E, where the total antimicrobial consumptionwas lowest, compared with 148 out of 189 cases (78%) in the high-

311993 1998 20032%6%2% 2%16%23%35%4%5%7%4%25%2%9%37%50%26%36%9%penicillin Vamoxicillin + clavulanic acidtrim.-sulfa.azithromyzinamoxicillinmacrolidesOtherFig. 12. Choice of last antimicrobial group prescribed before studyentry among 1-6 year old children in the 1993, 1998 and 2003 studies.consumption area V (p

321%17%1993 1998 20033%19935%3%8% 3%7% 7% 3%7%7%8%10%12%3%65%17%51%10%53%acute otitis mediasinusitisbronchitis acutaurinary tract infectionstonsillitispneumoniacutaneous infectionsFig. 13. Main last diagnosis when prescribing antimicrobials forchildren, aged 1-6, in the 1993, 1998 and 2003 studies.Percentage80%70%60%50%19931998200340%30%20%10%0%12 3 4 5 6Age in yearsFig. 14. Yearly prevalence as the percentage of children receiving antimicrobialtreatment for acute otitis media by age and study year.

treatment was more common in the lower ages studied, 54% (95%CI 44-64%) for one-year-old children in the 2003 study. The yearlyprevalence was statistically lower in the 1998 study for children 1-6years old, 35% (95% CI 31-38%) and in the 2003 study, 31% (95% CI28-34%) compared with the 1993 study, 48% (95% CI 45-52%).Figure 15 shows the number of treatments for acute otitis mediain the previous year by age (yearly incidence). The results are inagreement with those shown in Figure 10.Over the study period, the yearly incidence of antimicrobial treatmentbecause of acute otitis media decreased from 1.02 (95% CI0.92-1.12) in the 1993 study to 0.70 (95% CI 0.61-0.79) in the 1998study and further but not significantly, down to 0.60 (95% CI 0.52-0.68) in the 2003 study. In the 2003 study, the incidence was highestfor two-year-old children, 1.35 (95% CI 1.03-1.68), 1.27 (95%CI 0.93-1.61) for one-year-old children, 0.65 (95% CI 0.50-0.80)for tree-year-olds, 0.37 (95% CI 0.26-0.47) for four-year-olds, 0.2033Number/child/year2.52.01.51993199820031.00.50.012 3 4 5 6Age in yearsFig. 15. Yearly incidence of antimicrobial treatment for acute otitismedia per child in relation to age and study year.

341.61.41.21.00.80.60.40.20.01.61.41.21.00.80.60.40.20.0HafnarfjordurEgilsstadir1.61.41.21.00.80.60.40.21993 1998 20030.01993 1998 2003These graphs show the number of antimicrobial treatments for AOM/child/yearVestmannaeyjar1.6Bolungarvik1.41.21.00.80.60.40.20.01993 1998 2003 1993 1998 2003Fig. 16. Yearly incidence (95% confidence interval) of antimicrobialtreatment for acute otitis media per child in different areas studied in1993, 1998 and 2003.(95% CI 0.11-0.28) for five-year-olds and 0.14 (95% CI 0.07-0.21)for six-year-old children. Figure 16 shows the number of treatmentsfor acute otitis media during the preceding year in the three studiesin the different areas. Similarly to what was shown in Figure 11,there was a significant decrease in all the areas except for Vestmannaeyjar(area V).Predictors for antimicrobial prescribing for acute otitis mediaThe child’s age (younger age), history of tympanostomy tubes (pastor present) and residence in area V, were independently associatedwith the number of antimicrobial treatments for acute otitis media(IV). In the 1998 study (III), this was the case only for younger age.Smoking in the family household did not influence the odds forwhether children received antimicrobials for acute otitis media ornot in the 2003 study.

Association between parental expectations and doctor’s prescriptionhabits for management of upper respiratory tract infections inchildrenIn both the 1998 and 2003 studies (III, IV), the vast majority of parents(80-90%) in all areas agreed to the following two statements:“Some pathogens are becoming resistant to antimicrobials” and “Inappropriateantimicrobial use can lead to antimicrobial resistanceproblems with common pathogens”.Table 5 shows the results of the questionnaires about what theparents considered appropriate antimicrobial usage for the commoncold and for acute otitis media in the total number of participants inthe 1998 (III) and 2003 (IV) studies.Table 5. Parents’ views on appropriate antimicrobial treatment as reported inquestionnaires from the 1998 and 2003 studies (percentage in brackets).Year Always Sometimes Never Don’t knowIs it appropriate to give antimicrobial treatment for unspecified upper respiratorytract infections (common cold)?1998 1 (0.1) 346 (43.4) 377 (47.3) 73 (9.2)2003 0 (0) 394 (45.0) 420 (48.2) 59 (6.8)Is it appropriate to give antimicrobial treatment for acute otitis media?1998 66 (8.3) 686 (86.0) 13 (1.5) 33 (4.1)2003 75 (8.5) 757 (86.3) 6 (0.7) 39 (4.4)35The vast majority of parents in all the areas were also of the opinionthat acute otitis media should only sometimes be treated withantimicrobials. Very few stated that antimicrobial treatment was alwaysindicated for treating a common cold, while a similar percentageof parents stated “sometimes” and “never”. At the communitylevel (IV), a significant correlation was found between the children’stotal use of antimicrobials and the percentage of parents consideringit sometimes appropriate to treat a common cold with antimicrobials(r = 0.99, p = 0.01). In area E, where the prescription rate waslowest, it was also commonest for the parents to state that antimicrobialtreatment was never necessary for treatment of a commoncold, both 1998 and 2003 (III, IV). The response from parents to thequestionnaire addressing issues of parental expectations and aware-

36ness, further indicated that parents who consider it inappropriate totreat unspecified upper respiratory tract infections with antimicrobialssignificantly more often preferred that acute otitis media not betreated with antibiotics (III). They also more often considered it appropriateto prescribe antimicrobials for unspecific upper respiratorytract infection if their child had previously received antibiotics foracute otitis media (III).Tympanostomy tube placements (III, IV)Figure 17 shows the cumulative prevalence of being subjected totympanostomy tube insertion as reported in the 1998 and 2003 studies.About one third of the children had tympanostomy tube(s) currentlyor earlier. The curves for cumulative prevalence of tympanostomytubes during the first six years were similar in the 1998 and2003 studies.From 1998 to 2003 there was an increase in tympanostomy tubePercentage50%45%40%35%30%25%20%15%__ __199810%_____20035%0%01 2 3 4 5 6Age in yearsFig. 17. Cumulative prevalence as a percentage (95% confidenceinterval) of use of tympanostomy tubes 1998 and 2003 among 1-6years old children in the study areas.

placements in areas V (34.8 to 44.1%, p=0.034) and H (26.1 to36.8%, p=0.006), where antimicrobial prescription rates were highest,and a decrease in areas E (26.4 to 17.2%, p=0.049) and B (34.0to 24.6%, p=0.299), where the antimicrobial rates were lowest. Inarea E antimicrobial use had also diminished significantly (IV).Table 6 shows the odds ratio for having tympanostomy tube(s),compared with those not having tympanostomy tube(s) for variousvariables studied. Odds ratios were significantly higher for residentsof area V versus area E, day care attendance, and treatment with antimicrobialsfor acute otitis media, but not for gender or smoking inthe family household (IV).37Table 6. Odds ratio by multivariate analysis, adjusted for age, for children 1-6years old having tympanostomy tube(s) at present (n=123) as opposed to nothaving tube(s) (n=736) in the 2003 study.Variable No. Odds ratio 95% CI p-valueResidenceArea V 314 1Area E 214 0.35 0.17-0.64 0.0021Area B 61 1.02 0.46-2.24 0.97Area H 270 0.81 0.50-1.30 0.38GenderFemale 407 1Male 452 1.28 0.84-1.94 0.25Day careNo 71 1Yes 788 2.38 1.07-1.72 0.0317Smoking in the family householdNo 701 1Yes 158 1.01 0.60-1.72 0.95Number of antimicrobial treatments for acute otitis media during the last 12months0 594 11-2 203 1.96 1.22-3.17 0.0059>3 62 4.98 2.60-9.53 0.0001Multivariate analysis (859 cases analysed, data missing in 30 cases)Overall significance: chi-square = 100.176, df = 9, p < 0.0001

38Association between tympanostomy tube placements and antimicrobialuseBased on analyses by individuals, there was an association betweenhaving at present tympanostomy tube(s) and antimicrobial use becauseof acute otitis media in the last 12 months among children 1-6years old, as observed when studying these two factors in the 2003study (Table 6) (IV). There was also a significant association betweenthe use of antimicrobials for acute otitis media and cumulative prevalenceof tympanostomy tube placement as observed on the communitylevel when plotting the data for the different areas studied 2003 (IV).In Figure 18, changes in the use of tympanostomy tubes over the lastfive years are plotted against changes in use of antimicrobials (as apercentage) for acute otitis media in the different areas involved. Eventhough the association was not statistically significant (p = 0.138), inarea E, there was a concomitant and significant decrease both for tympanostomytube placements in children and for antimicrobial treatmentof acute otitis media as mentioned earlier (IV).Effects of tympanostomy tubes on recent antimicrobial drug consumptionIn 2003, of a total of 123 children having tubes (at present), 49 (40%)had received oral antimicrobials at least once during the previous8 weeks, compared with 124 of 737 children (17%) without tubes(p

39Differences in cumulative prevalence (%) of tympanostomy tubeplacements in children between 1998 and 20033834r = 0.86230p = 0.13826221814Area H10Area V62-2Area E-6Area B-10-14-18-22-26-30-50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5Changes (%) in the number of antimicrobial treatments per childper year for otitis media between 1998 and 2003Fig. 18. Differences in the use of tympanostomy tubes (cumulativeprevalence) in relation to change (%) in the use of antimicrobials(yearly incidence) for acute otitis media between 1998 and 2003 forthe different studies areas.(51.7%) of 743 children, and in 31 (8.1% of all children carryingpneumococci), the pneumococci were penicillin-nonsusceptible. Inthe 2003 study, 525 of 824 children studied (63.7%) carried pneumococci,and 50 (9.5%) were penicillin-nonsusceptible. If only typeablestrains of pneumococci are taken into account, then 31 (5.9%)were penicillin-nonsusceptible in the 2003 study.A comparison between the three study periods concerning prevalenceof PNSP is shown in Table 7. The carrying rate was highestin area V in the 1993 study (18.2%), in area E in the 1998 study(18.8%) and in area H in the 2003 study (13.0% or 10.6% if nontypeablestrains are excluded) (II, V).

40Table 7. Prevalence of penicillin-nonsusceptible pneumococci as observed inthe studies in 1993, 1998 and 2003.Study yearTotal studygroupPneumococcipresentPenicillin-nonsusceptiblepneumococci presentNumber Number Number % 11993 791 426 36 8.51998 743 384 31 8.12003 824 525 50 9.52003 824 525 31 a) 5.92003 824 525 19 b) 3.61Of all pneumococcal carriers,a)Typeable-stains, 2003b)Non-typeable (non-encapsulated) strains, 2003Table 8 shows the numbers of children carrying pneumococci andpercentages carrying PNSP in the 1993 study. Resistance was morecommon in the youngest children, those less than two years of age,compared with the children who were 2-6 years of age (I). This associationwas confirmed by multivariate analysis. In the 1998 study,age was also significantly associated with the presence of PNSP inunivariate analysis (II), while no significant association was observedin the 2003 study (V).Table 8. Penicillin-resistant pattern for pneumococci in children in the 1993study by age groups.Study yearTotal studygroupPneumococcipresentPenicillin-nonsusceptiblepneumococci presentNumber Number Number % 1

increases significantly between 1998 (II) and 2003 (from 2% to 7.8%,p < 0.001) (V). They increased in areas H and V (p = 0.0004 and p

42Table 9. Number (No) of penicillin-susceptible (PSP) and nonsusceptible pneumococci(PNSP), which are nonsusceptible (intermediate or resistant) to erythromycin(ERY), tetracycline (TET) chloramphenicol (CHL) and trimethoprimsulfamethoxazole(SXT) according to disc diffusion tests, in 1993, 1998 and2003, in respective study areas.Area Year ERY TET CHL SXTNo No % No % No % No %H PSP 1993 256 0 0 1 3.0 0 0 62 24.41998 163 1 0.6 1 0.6 0 0 46 28.82003 134 13 9.7 2 1.5 0 0 34 25.4PNSP 1993 24 20 83.3 22 91.7 13 54.2 24 1001998 11 7 63.6 8 72.7 8 72.7 11 1002003 20 10 50.0 10 50.0 4 20.0 20 100V PSP 1993 45 2 4.4 2 4.4 0 0 17 37.81998 117 0 0 0 0 0 0 25 20.72003 199 21 10.6 3 1.5 0 0 50 25.1PNSP 1993 10 9 90.0 9 90.0 10 100 10 1001998 5 5 100 5 100 5 100 5 1002003 15 14 93.3 14 93.3 9 60.0 15 100E PSP 1993 51 0 0 0 0 0 0 12 23.51998 56 4 7.1 2 3.6 0 0 10 17.92003 108 1 0.9 0 0 0 0 41 38.0PNSP 1993 1 1 100 1 100 1 100 1 1001998 13 13 100 13 100 13 100 13 1002003 12 8 66.7 7 58.3 0 0 12 100B PSP 1993 38 0 0 0 0 0 0 6 15.81998 17 2 11.8 2 11.8 0 0 12 70.62003 34 2 5.9 0 0 0 0 2 5.9PNSP 1993 1 1 100 1 100 1 100 1 1001998 2 2 100 2 100 1 50.0 2 1002003 3 2 66.7 2 66.7 0 0 3 100TOTAL PSP 1993 390 2 0.5 3 0.8 0 0 97 25.01998 353 7 2.0 5 1.4 0 0 93 26.62003 475 37 7.8 5 1.1 0 0 127 26.7PNSP 1993 36 31 86.1 33 91.6 25 69.4 36 1001998 31 27 87.1 28 90.3 27 87.1 31 1002003 50 34 68.0 33 66.0 13 26.0 50 100

ished by about one third from 1993 to 2003. The association betweenchanges in antimicrobial use and the carrying rate of PNSP, multiresistant,serotype 6B (Spain 6B -2) over the 10 years in each area will bedescribed below (Fig. 24).Associations with PNSP-carrying in children carrying pneumococciAlready at the time of the first study in 1993 (Paper I), the prevalenceof PNSP was higher among children who had taken antimicrobials.Of 317 children participating in the 1993 study who had receivedantimicrobials during the preceding year, 44 (13.9%) carried PNSPcompared with 3 out of 167 (1.8%) of those who had not receivedantimicrobials during the preceding year (p

44Table 10. Odds ratio (OR) of carrying penicillin-nonsusceptible pneumococci asopposed to penicillin-susceptible pneumococci by backward, stepwise, logisticregression method in the studies in 1993a), 1998b) and 2003c).Variable Number OR 95% CI P valueAge, 1993a) 424 0.70 0.52-0.96 0.025Residence, 1993a) Area H 279 1 (referencearea)Area V 55 2.62 1.00-6.81 0.048Area E 52 0.23 0.03-1.81 0.163Area B 38 0.31 0.04-2.43 0.266Number of antimicrobialtreatments in last12 months, 1993a) 424 1.32 1.11-1.58 0.002Residence, 1998b) Area H 170 1 (referencearea)Area V 122 0.519 0.17-1.62 0.260Area E 67 4.139 1.65-10.39 0.003Area B 19 1.852 0.36-9.50 0.460Number of antimicrobialtreatments in last12 months, 1998b) 378 1.50 1.23-1.82 0.0001Number of antimicrobialtreatments in last12 months, 2003c) 506 1.28 1.11-1.48 0.007a) Number of children in analysis, 1993 = 424, X2 = 35.87, df = 5, p < 0.0001.b) Number of children in analysis, 1998= 378, X2 = 25.49, df = 4, p < 0.0001 (II).c) Number of children in analysis, 2003= 506, X2 = 10.412, df = 1, p = 0.013 (V).much higher total use of antimicrobials, especially trimethoprim-sulfamethoxazoleand erythromycin in 1993 (I) and azithromycin in 2003(V) in this area.The carriage rate of PNSP was also associated with the lapsed timesince the last course of antimicrobials as shown in Figure 20. As seenin the figure, the prevalence of PNSP was higher in children who hadtaken antimicrobials recently (last 2-7 weeks).The observation of an association between recent antimicrobial useand carriage of PNSP was confirmed in multivariate analysis of datafrom all phases of our studies. Recent antimicrobial use (2-7 weekssince last treatment) instead of the number of antimicrobial courses

45%302520p

46Odds ratio765432102-7 weeks from last AM treatm. 19932-7 weeks from last AM treatm. 19982-7 weeks from last AM treatm. 2003Hf./Vestm.1993Hf./Vestm.1998Hf./Vestm.2003Egilsst./Vestm.1993Egilsst./Vestm.1998Egilsst./Vestm.2003Bol.vik/Vestm.1993Bol.vik/Vestm.1998Bol.vik/Vestm.2003Age in years 1993Age in years 1998Age in years 2003Fig. 21. Adjusted odds ratio (95% confidence interval) for carrying penicillin-nonsusceptiblepneumococci (PNSP) or not according to multivariatelogistic regression analysis in studies in 1993, 1998 and 2003.(Number of children in analysis 1993 = 426, X2 = 46.72, df = 8,p < 0.0001. Number of children in analysis 1998 = 384, X2 = 22.12,df = 9, p = 0.0085. Number of children in analysis 2003 = 510, X2 =31.47, df = 11, p = 0.0009)Boys 1993Boys 1998Boys 2003Number siblings 1993Number siblings 1998Number siblings 2003Day care 1993Day care 1998Day care 2003History of tympanostomy tubes, 1998History of tympanostomy tubes, 2003Smoking in the household, 2003crobials 8-52 weeks before study entry (p

47Carrying ratio0.80.70.60.50.40.30.20.10.0PSP 2-3 weeksPNSP 2-3 weeksPSP 4-5 weeksPNSP 4-5 weeksPSP 6-7 weeksPNSP 6-7 weeksPSP 8-9 weeksPNSP 8-9 weeksPSP 10-11 weeksPNSP 10-11 weeksPSP 12-13 weeksPNSP 12-13 weeksPSP 14-15 weeksPNSP 14-15 weeksPSP 16-17 weeksPNSP 16-17 weeksPSP 18-19 weeksPNSP 18-19 weeksPSP 20-21 weeksPNSP 20-21 weeksPSP 22-23 weeksPNSP 22-23 weeksPSP 24-25 weeksPNSP 24-25 weeksPSP 26 weeks or morePNSP 26 weeks or moreFig. 22. Carriage rate (95% confidence interval) of penicillin-susceptible(PSP) (green) (n=648) and penicillin-nonsusceptible pneumococci(PNSP) (red) (n=97) by all children receiving antimicrobialsduring the 12 months prior to study entry (n=1315) for the 1993,1998 and 2003 studies, by the number of weeks from the last antimicrobialtreatment.in the preceding 2-7 weeks carried PNSP, as opposed to only 18 outof 253 children receiving antimicrobial treatment 8-52 weeks beforesampling carrying PNSP (p=0.027).Figure 22 shows the carriage of penicillin-susceptible (PSP) andPNSP of all children receiving antimicrobials (i.e., not only of thosecarrying pneumococci) for the three studies by the number of weeksfrom the last antimicrobial treatment. Relatively speaking the numberof PSP strains are similar to the number of PNSP strains two tothree weeks after antimicrobial treatment.

48% PNSP87656B23F1419F9VNon-typeable432101993 1998 2003Fig. 23. Spread of different serotypes of penicillin-nonsusceptiblepneumococcus (PNSP) as carrying ratio (%) of all pneumococci observedin the studies in 1993, 1998 and 2003.Factors associated with carriage of erythromycin-resistant pneumococciAll the variables tested for association with carriage of PNSP werealso tested for association with carriage of erythromycin-resistantpneumococci with a multivariate, backward, stepwise, logistic regressionmodel in the 2003 study (V). As for PNSP carriage, the numberof antimicrobial treatments was the only independent risk factorfor carriage of erythromycin-resistant pneumococci, with an oddsratio of 1.18 for each treatment (95% CI 1.03-1.35), p=0.0157.Spread of resistant strainsIn the 1998 study the carrying rate of PNSP, multiresistant, serotype6B, 7.5%, was similar to the 1993 study, 7.7% but decreased in the2003 study to 2.5% (p

4925Egilsstadir3.025Vestmannaeyjar3.0% PNSP type 6B20151052.52.01.51.00.5Number of antimicrobialcourses/child/year% PNSP type 6B20151052.52.01.51.00.5Number of antimicrobialcourses/child/year01993 1998 20030.001993 1998 20030.025Bolungarvik3.025Hafnarfjordur3.0% PNSP type 6B20151052.52.01.51.00.5Number of antimicrobialcourses/child/year% PNSP type 6B20151052.52.01.51.00.5Number of antimicrobialcourses/child/year01993 1998 20030.001993 1998 20030.0Fig. 24. The prevalence of penicillin-nonsusceptible pneumococci(PNSP) of multiresistant serotype 6B (the Spain 6B -2 clone) as a carriagerate of all pneumococci and use of antimicrobials in the samplegroups, as observed in the study areas in the 1993, 1998 and 2003studies (♦---♦). Data from antimicrobial sales statistics in the studyareas for children < 7 years old, 1993 and 1998 are also shown forcomparison (• --- • ).(V). The new non-typeable PNSP serotype was found in all studyareas. Serotype 9V was found only in area H and a new serotype 14only in area E.Clonal spread of PNSP of multiresistant 6B strain (Spain 6B -2) indifferent communitiesWhen studying different areas separately, obvious differences betweenhow the prevalence of PNSP of multiresistant serotype 6B(phenotypically identical according to antibiotic susceptibility test-

50ing as the Spain 6B -2 clone) changed in these areas were observed(II, V). The PNSP 6B strain was quite common in area V and areaH in the south, near Reykjavik, the capital of Iceland, already in the1993 study but decreased in the next two studies (Fig. 24). This maybe compared with what was observed in areas E and B in the eastand west, remote areas, where the prevalence was low in the 1993study but increased considerably in 1998 and had disappeared againin 2003. As can also be seen in Figure 24, the use of antimicrobialswas lower in the later studies, but there seems to be no obvious correlationbetween total use of antimicrobials in the community forchildren and increase or decrease in the prevalence of the multiresistantPNSP 6B strain (the Spain 6B -2 clone).

DISCUSSION51Starting-points when planning the studiesThere were many reasons for focusing my research in primaryhealthcare in Iceland on upper respiratory tract infections and theuse of antimicrobials drugs among children. Upper respiratory tractinfection and especially acute otitis media, continues to be one ofthe most common childhood infections and source of morbidity inchildren (Söderström 1995; Rovers et al. 2004). Acute otitis mediais one of the commonest reason for a child visiting a GP, and alsothe most common reason for antimicrobial prescription (McCaigand Hughes 1995; Arason et al. 1996; McCaig et al. 2002; Roverset al. 2004). The prevalence of PNSP of multiresistant serotype 6B(now recognised as Spain 6B -2) increased rapidly in Iceland after itsfirst appearance 1989. The prevailing knowledge at that time indicateda causal relationship between antimicrobial use and developmentof resistant strains of pathogens not only in hospital settings(McGowan 1983) but also possibly in communities (Molstad et al.1988; Molstad and Hovelius 1989; Eliasson et al. 1990; Molstad etal. 1992; Reichler et al. 1992). GPs’ prescription pattern in differentareas have been shown to differ, which might make a study of antimicrobialprescription in relation to bacterial resistance pattern bothinteresting and important.When planning the study, it was known that the prescription ofantimicrobials was commoner in Iceland than in the other Nordiccountries. Acute otitis media in a child was found to be the mostcommon reason for prescribing an antimicrobial for a child, andthis was a reason for focusing the study on children with specialreference to the treatment of acute otitis media. International ratesof antimicrobial prescriptions and tympanostomy tube placementsfor otitis media vary greatly, which can be explained largely by thelack of uniform evidence-based guidelines (Schilder et al. 2004). Althoughtympanostomy tube placement has been a well-establishedtreatment option for chronic effusion in the middle-ear and recurrentepisodes of acute otitis media, the prevalence rate of tympanostomytube placements in Iceland during the planning of phase II of this

52study was not known at that time. It was therefore deemed of interestto include a study of tympanostomy tubes in the study plan,with special focus on the potential association between frequent useof antimicrobials and the tympanostomy tube placement rate on thecommunity level, especially in the third phase of the study wheretime trends could also be observed.Iceland should be a suitable country for studying the associationsbetween antimicrobial use and the development of resistance incommon pathogens like pneumococcus in the community. Prescriptionpatterns can easily be described, thanks to: computerised informationin the primary healthcare centres, computerised informationfrom the local pharmacies and the organisation of healthcare in Iceland,where people, at least outside the capital of Reykjavik, visittheir own primary healthcare centre and their own pharmacy. Becauseof the special geography of Iceland, areas are, to some extent,isolated from each other; this makes it easier to study changes inresistance patterns or to follow up newly recognised resistant clones.Furthermore, the prescription patterns of GPs in different areas hasbeen shown to differ in Iceland, which might make a study of antimicrobialprescription in relation to bacterial resistance patterns evenmore interesting.Performance of the studiesThis thesis is mainly based on the following basic examinations:• Prescription studies on all antimicrobial sales, carried out in1992-1993 and 1997-1998, including all ages, and involvingthe pharmacies of the study areas.• Sampling of nasopharyngeal bacteria, cultivation for pneumococciwith serotyping of PNSP strains and study of their resistancepattern; this sampling included children up to 6 years oldin 1993 and was confined to children 1-6 years old in 1998 and2003.• Questionnaire about socio-demographic factors and history ofprevious use of antimicrobials and causes in the same childrenand on the same occasions as mentioned in the precedingpoint.• Questionnaire to parents about personal preferences in relation

53to antimicrobial treatment for upper respiratory tract infections1998 and 2003.• Questionnaire about previous and present history of tympanostomytube use in 1998 and 2003.It was possible to carry out all these examinations according toplan. The co-operation with the local pharmacies was excellent, aswas the co-operation with the GPs and other personnel at the involvedprimary healthcare centres and the laboratory where pneumococcicultivation was done.The co-operation with the personnel at the day care centres aswell as with the children and their parents was also very good, andin the studies based on random sampling or all available children(II-V), the participation rates were high, 75-90%. In the first phase,where sampling was from all available sick and healthy 0-6-year-oldchildren, the participation rate was also high (15-38% of total populationunder 7 years old).In summary this means that the prerequisites and the performanceof the different examinations were of high quality, facilitating thedrawing of safe (accountable) conclusions when analysing the data.Antimicrobial useThe use of drugs by sales statistics, measured as number of defineddaily doses (DDD) per 1000 inhabitants per day, is useful when comparingnations and whole communities (Medicines consumption in theNordic countries http://www.nom-nos.dk/nomesco.htm , last viewedMai 2006 ; Goossens et al. 2005). One defined daily dose is by definitionthe certain therapeutic amount (for example in milligrams) of adrug needed by an adult person per day. Although this calculation canbe used to describe the amount (in milligrams) used in each age group,it does not give a clear picture when comparing therapeutic doses forchildren and adults. Therefore, the prescription rate (incidence rate) isbetter for demonstrating differences in consumption between childrenand adults as was demonstrated in Figure 7.As observed in a previous Icelandic study (Njalsson and McAuley1992), women use the healthcare centres more than men anduse more drugs. This is also true regarding the use of antimicrobials

54specifically, as shown in our study. It is, however, worth noting thatthis gender difference first becomes apparent in the early teenageyears. This is in accordance with results from other studies showingthat women have more episodes of respiratory tract infections thanmen, probably due to the fact that women have closer contact withchildren, both at home and in child-related work (Monto and Ullman1974; Söderström 1995).Seasonal variation with the highest peak of antimicrobial use inlate winter has been reported from previous studies (Söderström1995; Goossens et al. 2005). It was also confirmed in our study. Viralinfections like the common cold are far more common than bacterialinfections (Benediktsdottir 1993; Monto 1994; Söderström 1995)and more common during the winter, but it can sometimes be hardto distinguish accurately between viral and bacterial infections clinically(Heikkinen and Chonmaitree 2003). This can partly explainwhy antimicrobial prescriptions are so prevalent during the winterin Iceland like in other countries with heightened winter peaks withhigh yearly use of antibiotics (Goossens et al. 2005). This means alsothat the peak load of infections in people seeking healthcare servicein Iceland is during late winter, and this was one of the reasons thatwe mainly collected the nasopharyngeal specimens March to May.A child with a bacterial upper respiratory tract infection oftenhas a clinical picture of symptoms involving more than one site, includingthe middle-ear, nose and throat. The higher prescription ofantimicrobials for sinusitis in 1998 and 2003 than in 1993 possiblydepends on a shift from stating acute otitis media as the main diagnosisto sinusitis when prescribing antimicrobials is deemed to beneeded. In others studies, antibiotics are also frequently prescribedfor children with unspecified upper respiratory tract infections andbronchitis, despite recommendations to the contrary (Howie 1983;Hamm et al. 1996; Schwartz et al. 1997; Nyquist et al. 1998; Wang etal. 1999). A frequent claim, which has not been adequately studied,is that restrictions in social security systems make people go to workeven though they or their children suffer from infections. As a consequenceof this social pressure, children “have to” be treated withanti-infective drugs to be able to go to school or day care centres(Agenas et al. 1995; Jonsson and Haraldsson 2002).

A phenomenological investigation in Iceland of why GPs prescribeantimicrobials in cases when there are no clear signs of bacterialinfections, called “non-pharmacological prescriptions of antibiotics”concludes that the principal causes of such use of antibioticsare “the lack of stable doctor-patient relationships due to lack of continuityin medical care, pressure from patients in a stressful society,physician’s work pressure, the physician’s own personality, particularlythe earnings incentive and service mentality and, last but notleast, the physician’s lack of confidence and uncertainty, resulting inuse of antibiotic prescriptions as a coping strategy in an uncomfortablesituation” (Petursson 2005 a).Antibiotic utilisation among Icelandic children, age < 7 years, inour study 1998 (II), varied between areas in similar amount (from7.6 to 17.1 DDD/1000 children/day) as was shown in others studiesthe same year between various Danish and Swedish counties (from8.0 to 19.7 DDD/1000 children/day) (Melander et al 2000; Melanderet al. 2003). “The observed variations in antibiotic prescribing mayreflect different parental and/or prescribes attitudes towards use ofantibiotics and they emphasise that antibiotic prescribing is influencedby factors other than the prevalence of bacterial infections.Relationships between socio-economic position (educational level)and drug utilisation should not be generalised from one area to another”(Melander et al. 2003).The first part of the study was followed by an unstructured nationwidecampaign to reduce unnecessary antimicrobial use for upperrespiratory tract infections, mainly in children. The interventionsconsisted of information and education of both the public throughmass media and of physicians through meetings and the IcelandicMedical Journal. Prudent antimicrobial use was encouraged especiallyfor acute otitis media. New antimicrobial prescription guidelineswere prepared and made available on the Internet (1997) http://lyf.landlaeknir.is/Brad_eyrnabolga_barna.htm (last viewed in January2006). Simultaneously a greater reduction in antimicrobial salesfor trimethoprim-sulfamethexazole statistics was observed than forother antimicrobials. Indirect effect of social (parental educationallevel) and climatological factors (on infection rate) on antimicrobialuse are possible but unlikely in our study but are reported to be indi-55

56rect force on antimicrobial use and resistance in Spain (Garcia-Rey etal. 2004). A national ambulatory medical survey in North-Americashow dramatic decline (~40%) in the population based prescribingof antimicrobial agent to children and adolescents from 1990 to 2000and 47% decline because of otitis media specifically (McCaig et al.2002). The bad news is that during the 1990´s, a shift occurred fromusing targeted narrow-spectrum antimicrobials (the second componentof appropriate antimicrobial use) to broad-spectrum antimicrobialsfor children, from 23% to 40% (Steinman et al. 2003). The useof second-generation macrolides (including azithromyzin) amongchildren has increased dramatically in North-America, even amongyounger children, for whom use for initial treatment of illness is notrecommended (Stille et al. 2004). Changes in antimicrobial prescribingin our study and increasing use of broad-spectrum antimicrobialsin some study areas along with high antimicrobial use will howeverbe further discussed her below in connection with changes in theantimicrobial treatment options for acute otitis media over the studyperiod and in the chapter “Amount and type of antimicrobials associatedwith resistance in the community”.The incidence of antimicrobial treatments because of acute otitismedia was found to be similar in our 2003 study as has been reportedto the incidence of diagnosed acute otitis media for children in earlierstudies from the United States (Teele et al. 1989; Paradise et al.1997) and from Finland (Alho et al. 1991). There is more opportunityfor the spread of respiratory infections and also a higher rate of acuteotitis media among children in day care settings (Wald et al. 1988;Uhari et al. 1996; Rovers et al. 1999). In our studies, ~80% of all thechildren attended day care. The child’s age (younger age), residencein a high antimicrobial consumption area and history of tympanostomytubes (past or present), were independently associated with thenumber of antimicrobial treatments for acute otitis media (IV). In the1998 study (III), this was only the case for younger age and the highantimicrobial consumption area.The prescription of antimicrobials for children, particularly theprescriptions for acute otitis media, decreased considerably in thecommunities over the study period; in some areas the decrease isdramatic. The difference in prescriptions of antimicrobials was rath-

er small between different areas at the beginning of our study period,but increased, and, at the end of the period, it was three times higherin the area where the prescription rate was highest, compared withthe area where it was lowest. Not only is the prescription rate ofantimicrobials different from one area to another in the end of ourstudy but also the choice of an antimicrobial agent when prescribingan antimicrobial. Broad-spectrum antimicrobials, especially azithromycin,were more often prescribed in areas where the total antimicrobialuse was highest. Success in this aspect in some areas and notothers is of special interest and may have complex explanations.A recent study addressed the phenomenon of varying clinical“mindlines” among primary healthcare practices in the United Kingdom(Gabbay and le May 2004). The authors found out that experiencedGPs rarely use explicit evidence from research. They createshortcuts in their decision making, based on a combination of inputsand impulses from their professional surroundings, such as trustedcolleagues and opinion leaders, written guidelines, material from patients,and pharmaceutical representatives.Parents in the area where antimicrobial consumption was lowestand narrow-spectrum antimicrobials were most often used, were lesslikely to be in favour of antimicrobial treatment (III, IV). The responsefrom parents to the questionnaire addressing issues of parentalexpectations and awareness, further indicated that parents whoconsider it inappropriate to treat unspecified upper respiratory tractinfections with antimicrobials significantly more often preferred thatacute otitis media not be treated with antibiotics (III). These variationsin parental attitude together with a significant correlation at thecommunity level between the children’s total use of antimicrobialsand the percentage of parents considering it sometimes appropriateto treat a common cold with antimicrobials (IV), may be importantobservations in this study as primary care physicians maintain thatparental pressure and expectations in relation to antimicrobial drugprescriptions represent an important barrier to restrictive prescriptionpractices (Macfarlane et al. 2002; Garbutt et al. 2003; Siegel et al.2003; Petursson 2005 b). The high percentage of parents consideringit sometimes appropriate to treat a common cold with antimicrobialsin our studies is in accordance with results from study conducted in57

58the United States where misconception about the appropriate treatmentfor colds was concluded to be predictive of increased healthservice utilization (Lee et al. 2003). Other studies have shown atendency to reduce antimicrobial treatments for acute otitis mediain children in tandem with parents’ acceptance of the reduction,through educational intervention with parents, watchful waiting andsafety-net antibiotic prescription (Little et al. 2001; Smabrekke etal. 2002; Siegel et al. 2003; McCormick et al. 2005). It seemed thatthe prescribing doctor’s habits were adopted by the parents whendealing with children with upper respiratory tract infections in ourstudies (III, IV). It is reasonable to believe that parents’ views reflectthe information given in mass media and during discussionswith the healthcare personnel (nurses as well as GPs). This is in accordancewith the observation that healthcare practices can functionlike “families”, where habits or indirect rules are created (Gabbayand le May 2004). Variations in parental attitude toward antimicrobialtreatment may therefore be important and are possibly part ofthe above-mentioned “mindlines”.Possible causative explanation of success in diminishing antimicrobialuse in some areas but not others may be explained by possiblecorrelation between non-antimicrobial drug use for acute otitismedia specifically and lower risk of relapsing episodes of acute otitismedia later and therefore decreasing need for antimicrobials as willbe discussed below in the next chapters in connection with changesin the microflora of the nasopharynx after antimicrobials use.Tympanostomy tube placementsOur feeling that tympanostomy tubes were common was confirmedin our studies, and we also found that it was more common than inother countries (Paradise et al. 1997; Coyte et al. 2001; Desai etal. 2002; Schilder and Rovers 2003). In a recent Finnish otitis mediavaccine trial study, children were followed up to 24 months ofage (Palmu et al. 2004). Tympanostomy tube placement and/or adenoidectomywere performed in 24.1% and 20.6% of the children inthe control and trial group, respectively (not significant difference).Tympanostomy tube placement, though, was much less common inthe south of Sweden, where ~10% of children had a history of tym-

panostomy tube insertion (Melander et al. 1998). This contrasts alsosomewhat to results from the United States, where the incidence ofacute otitis media among children seems to be similar to that in Icelandbut the rate of tympanostomy tube placements is generally muchlower (

60(Kristinsson 1995). The prevalence in the community was not knownat that time.Comparative and analytical studies have demonstrated a relationshipbetween high antibiotic consumption and increasing penicillin-resistanceamong pneumococci. In few reported epidemiologicalstudies for whole communities like in our studies (I, II, V) and someothers (Melander et al. 1998), this correlation was found not only forantimicrobial use by whole communities (comparative and indirect relationship)like in some others studies (Melander et al. 2000; Granizoet al. 2000; Dias and Caniça 2004; García-Rey et al. 2004; Goossenset al. 2005) but also for individual antimicrobial use (analytical andcausative relationship). It is therefore of interest to observe the bigdifferences in the prevalence of antimicrobial resistance among pneumococcifrom time to time in the separate areas with interplay of otherpossible risk factors for individual carrying in our studies, especiallybecause the increase in the prevalence of PNSP 1993 and 1998 wasalmost solely due to an increase in one particular strain, multiresistantserotype 6B which was shown to be phenotypically identical by antibioticsusceptibility testing as the Spain 6B -2 clone and may be explainedby a novel clonal spread into “virgin” communities and possible herdimmunity could therefore be better defined as will be discussed laterin the chapter “Clonal spread in the community”.Studies of the individual relationship between antimicrobial useand resistance in pneumococci have produced conflicting results,reflecting differences in the study design, setting, and measures ofassociation used (Lipsitch 2001). In previously published studies thecarriage rate of resistant pneumococci has usually been calculatedwith the total number of children carrying pneumococci as the denominator.In all our three cross-sectional studies, the risk of carryingPNSP was 4-5 times greater during the first 7 weeks after eachantimicrobial course for children actually carrying pneumococci.Antimicrobial treatment does though not appear to increase an individual’sabsolute risk of carrying PNSP after treatment in some studies.However, it may increases a patient’s relative risk of carriage ofPNSP (Lipsitch 2001). In French prospective studies, antimicrobialtreatment did not increase the risk of an individual child carryingPNSP even though the proportion of PNSP increased (i.e., only for

those carrying pneumococci) (Cohen et al. 1997; Varon et al. 2000).This was mainly explained by a significant decrease in the number ofindividuals carrying penicillin-susceptible pneumococci after havingreceived antimicrobials and thereby relatively higher PNSP rate(relative risk) among those still carrying pneumococci.Because of the above-mentioned observations, we recalculatedthe data from all three studies for all children, i.e., not only those carryingpneumococci. The results were nevertheless identical to thosethat had been obtained before i.e., higher (absolute) risk of PNSPcarriage for all children recently after antimicrobial treatment. Ourresults are therefore not congruent with the results from the Frenchprospective studies. We conclude that current antimicrobial use encouragesthe uptake of resistant pneumococci and subsequent colonisationor “selective acquisition of (foreign) nonsusceptible strains”from the outer ecosystem (from the community). In addition, PNSPnot previously detected by our methods may proliferate and becomeabundant and detectable after antimicrobial treatment (unmasking ofdormant and/or nonsusceptible strains present in very low numbersfrom the mucosa). This may be supported by the fact that in our laststudy, carriage of 2-3 strains was not uncommon (sometimes bothpenicillin-susceptible and nonsusceptible) (V). Detection of multiplepneumococcal carriages by our culture methods is though not possibleunless the strains exhibit different colonial morphologies.In vitro studies show that low doses of beta-lactam antimicrobialscan increase the growth of both intermediate and resistant pneumococciin cultures on agar plates (Negri et al. 1994). Therapeuticregimens containing beta-lactam antibiotics should therefore beable to select for PNSP, especially if given in low dosages. Clinicalstudies from France also support this theory (Guillemot et al. 1998).Modifying (increasing) the dose and duration of antibiotic therapymay therefore potentially limit the spread of resistant pneumococcias shown in another study (Schrag et al. 2001). Although it was notpart of our prospective epidemiological study we confirmed thatprescribed antibiotic dosages did not change between the first twophases of the study (II) and such change was unlikely between thesecond and third phases when antimicrobial use decreased much lessthan between the first phases.61

62In a Swedish study, a median duration of PNSP carriage (MIC, >or = 0.5 mg/L) was 19 days (range 3-267 days), but it was 10 dayslonger in infected than in asymptomatic contact cases (Ekdahl et al.1997). A significant risk factor for prolonged carriage was repeatedtreatment courses for acute otitis media. Other significant risk factorsfor prolonged carriage were the occurrence of first episode of acuteotitis media before the age of one year, the carriage of PNSP by otherfamily members, and the obtainment of a first positive culture duringthe winter months (Ekdahl et al. 1997). In our studies most childrencarried PNSP 28-42 days after the last antimicrobial treatment.A rapid selection of PNSP isolates during or after (II) antibiotictreatment for acute otitis media specifically has also been shownin other studies (Dagan et al. 1998 a; Brook and Gober 2005; Mc-Cormick et al. 2005). The clinical outcome of antibiotic treatmentof acute otitis media may depend on antibiotic-mediated bacterialeradication and the spread of resistant clones could be facilitated byfailures to eradicate resistant strains and subsequent re-colonisationof the mucosal membranes after discontinuation of therapy (Daganet al. 2001 b). Conversely, eradication of susceptible pneumococcusin the nasopharyngeal flora by antimicrobials means that new strainswill emerge thereafter and hence may also increase the likelihood ofnew episodes of acute otitis media (recurrent otitis media) and possiblyincrease the risk of having tympanostomy tube later as describedlater on page 68-69.Amount and type of antimicrobials associated with resistance inthe communityAlthough the prevalence of resistant strains can be related to thecommunity use of antimicrobials, in most countries, it is often notpossible to quantify this use. Accordingly, it has not been possibleto define acceptable levels of antibiotics usage. In our study wehave tried to quantify the use, especially among Icelandic children,from the prevalence of prescriptions, the number of defined dailydoses/1000/day and the number of defined daily doses per prescriptionby antimicrobial class and residence (II). At the same time, wemeasured the resistance rate among pneumococci, and its relation toantibiotic usage. On the other hand, it was not our aim to analyse the

safety thresholds of use for either each antibiotic class or the totaluse.Low dosage and long duration of antimicrobial treatment hasbeen demonstrated to increase the risk of PNSP carriage (Guillemotet al. 1998). Comparison of the number of DDD/prescription in 1993and 1998 studies shows that this is not likely to be the explanationfor differences in PNSP rate in the study areas (II).Our data suggest that some antimicrobial agents may be moreactive in inducing PNSP carrier state because of selective antimicrobialpressure. For example, only trimethoprim-sulfamethoxazolewas significantly associated with carriage of PNSP in our first study(I). Other authors have also shown an association between trimethoprim-sulfamethoxazoleand carriage of PNSP (Dagan et al. 1998b; Melander et al. 1998)An explanation similar to that for increased carriage risk of PNSPby selective antimicrobial pressure after recent antimicrobial treatmentmay also apply to carriage of erythromycin-nonsusceptiblestrains of pneumococci (V). Much higher use of macrolides, especiallyazitromycin, in 2003 than in 1998 may be one explanation forthis development. Even though the continued high use of antimicrobialsin one area (area V) could perhaps explain why the PNSPof multiresistant serotype 6B (the Spain 6B -2 clone) is still presentin 2003, it is tempting to conclude that rapidly increasing use ofazithromycin (one third of all prescriptions in 2003 and much higherthan in the other areas) has established a favourable selective environmentfor this clone, which is also macrolide-nonsusceptible. Thisenvironment may also have led to the marked increase in the numberof erythromycin-resistant but penicillin-susceptible pneumococci inthat area. In fact, the long half-life and low serum concentrations ofazithromycin have been associated with increased resistance ratesof not only macrolide-nonsusceptible but also penicillin-nonsusceptiblepneumococci (Kastner and Guggenbichler 2001; Dias andCaniça 2004). This is in accordance with what is now observed inmany other countries as the hidden epidemic of macrolide-resistantpneumococci (Klugman and Lonks 2005).Our study (comparative and analytical covering 10 years) is oneof the first clearly showing that there is an causative association be-63

64tween antimicrobial use and antimicrobial resistance patterns in differentcommunities, something which had previously been shown inhospital settings (McGowan 1983) and day-care settings (Reichleret al. 1992). A recent French study showed also that intensive educationalstrategies aimed at optimizing antibiotic use could significantlyreduce the rate of PNSP colonization in areas with high resistancerates (Guillemot et al. 2005).Results from studies in Sweden, Spain and Portugal dealing withthe association between antimicrobial use and carriage of antimicrobial-resistantpneumococci are congruent with results from ourstudies in most aspects (Melander et al. 1998 a; Melander et al. 1998b; Melander et al. 2000; Granizo et al 2000; Dias and Caniça 2004;García-Rey et al. 2004). Other older Swedish studies showed theemergence and persistence of ß-lactamase-producing bacteria (Haemophilusinfluenzae and Moraxella catharralis) in the upper respiratorytract in children treated with ß-lactam antibiotics (Molstad etal. 1988; Molstad and Hovelius 1989; Eliasson et al. 1990). This resistancepattern also appeared to be a long-term ecological effect ofdifferences in the level of use of antibiotics between different communitiesin Sweden (Molstad et al. 1992).Clonal spread in the communityThe first observation of a PNSP, multiresistant, serotype 6B in Icelandwas in 1989 and in the following years proved to be strain recognisedas the Spanish Icelandic clone, i.e., Spain 6B -2 as mentioned earlier.Before the first phase of the study, this clone was the first to spread inthe heavily populated metropolitan areas near Reykjavik, the capitalof Iceland, and then spread to remote areas. Despite means for thefast transport of people, the transfer of new pneumococcal clones ishighly time-dependent (Melander et al. 1998 b; Arason et al. 2002a). In this study, special attention has been given to not only the fastspread of this clone in the community through high antimicrobial usebut also its disappearance (V). The disappearance, however, was notexplained, as might be expected, by direct (individual) associationbetween antimicrobial use and carriage risk of PNSP in children, asdiscussed above. The effect of possible interaction of antimicrobialuse and herd immunity may have been the missing explanatory link

in the first phase of the study. We have therefore studied the possibleinterplay of known individual risk factors for PNSP carriage in thecommunities, such as antimicrobial usage interacting with factorslike time and the distance between study areas in the second andthird phases of the study. The increase of PNSP of multiresistant serotype6B studied in this study, shown to be phenotypically identicalby antibiotic susceptibility testing to the Spain 6B -2 clone, in “virgin”communities (E and B) in the second phase explains the fitness ofthat particular clone to spread even in communities with low antimicrobialuse. The prevalence has decreased in all of the study areas(V) and, as far as I know, in Iceland as a whole. For this particularpenicillin-resistant pneumococcal strain (clone), it can be postulatedthat the period from the onset to the end of an epidemic in smallcommunities with low antimicrobial use is less than 10 years. In additionto herd immunity, it is likely that the extent of antimicrobialuse will play a role in determining the peak prevalence (how fastthis clone will spread through the community by high carrying rateby the individuals) and the subsequent endemic prevalence and behaviour.This led us to construct a theoretical model for a plausibleexplanation of the appearance and disappearance of this special bacterialclone, which is shown in Figure 25 b. It is reasonable to believethat other or new antimicrobial-resistant pneumococcal clones willbehave in a similar manner.Strains failing to produce a polysaccharide capsule have commonlybeen isolated from carriage and disease contexts in some otherstudies (Hanage et al. 2006). Some studies seem to indicate thatmost non-typeable pneumococci may have diverse genetic backgroundscompared to typeable pneomococci and may have evolvedas a distinct group of pneumococcal isolates (Sa-Leao et al. 2006;Hanage et al. 2006). The non-typeable pneumococci in our 2003study (V) all had a rough appearance and are therefore probably nonencapsulated,although this has not been confirmed with molecularinvestigations. Such rough (non-encapsulated) strains had not beenobserved in the previous two studies. It is unlikely that such roughstrains were missed in the previous studies since all the agar plateswere read by the same two senior biomedical laboratory scientists.Their appearance therefore probably indicates the introduction of a65

66a)2 5Area HArea VArea E and B2 01 51 0BE501 9 9 3 1 9 9 8 2 0 0 31 9 9 3 1 9 9 8 2 0 0 31 9 9 3 1 9 9 8 2 0 0 3b)2 52 0Area VArea E1 51 0Area HArea B501993 1998 2003Fig. 25. a) Prevalence of penicillin-nonsusceptible pneumococci(PNSP) of multiresistant serotype 6B (recognised as the Spanish-Icelandic clone, Spain 6B -2), as a percentage of all children carryingpneumococci, observed in areas H, V, E and B in the studies in 1993,1998 and 2003. b) A theoretical model (epidemiological curves) forthe spread and disappearance of Spain 6B -2 clone in four communitiesin Iceland 1993-2003 (The form of the curves indicate that thetime scale for the emergence of resistance under constant selectivepressure is typically much shorter than the decay time (Austin et al.1999)).novel clone. Probably the new non-typeable strains (clone) have appearedand spread successfully in the day care centres. This increase,however, has not been noted in specimens from infected patients inIceland (Kristinsson K.G., personal communication), probably consistentwith the lack of virulence of these strains. The significance ofpenicillin non-susceptibility in the non-typeable (non-encapsulate)pneumococci is not clear.

New typeable (encapsulated) as well as non-typeable (non-encapsulated)PNSP have become established in recent years in the study areas.The choice of antimicrobial class may influence the selective environment,favouring this particular resistant clone and stabilising the olderones. Also, in the near future, herd immunity may change through theimpact of new pneumococcal conjugate vaccines (if used), which willprobably reduce the acquisition of vaccine-type strains but increase therisk of non-vaccine serotype strain acquisition in the population.Associations between acute otitis media, antimicrobial use andtympanostomy tube placementsIn the first part of our 1993 study, evaluation of risk factors for carriageof PNSP demonstrated that antimicrobial use was an importantrisk factor. Our results indicated that the use of trimethoprim-sulphamethoxazolemight be worse than the use of other antimicrobials(I). This was followed by a nationwide campaign to reduce unnecessaryantimicrobial use for upper respiratory tract infections, mainlyin children as described earlier (Kristinsson 1999). These efforts resultedin a 35% reduction in the use of liquid antimicrobials for oraluse by children from 1992 to 1997. This is in congruence with evenbigger changes in one study area (area E), where the antimicrobialprescription for acute otitis media diminished by about 2/3 over the10-year period, and broad-spectrum antimicrobials were only usedin 32% of cases compared to 78% in the high-consumption area (IV).The most likely explanation, in my opinion, is a change in antimicrobialprescription habits for acute otitis media among the GPs inthat particular area rather than diminished prevalence of the naturalonset of acute otitis media in that area but not the others as discussedabove in relation to total antimicrobial use. How conservative treatmentstrategy may possibly diminish the prevalence of acute otitismedia will be discussed better in connection to the changes in therate of tympanostomy placements for children here below (diminishedrate of children who may develop chronic effusion or relapsingacute otitis media and who may need tympanostomy tubes later).An important question is also whether tympanostomy tubes will protectagainst new middle-ear infections, diminishing the need for antimicrobialslater. Our results indicate that the wide-use of tympanostomy67

68tubes does not support this view. This does not exclude the possibilitythat a subgroup of infection-prone children with chronic middle-ear effusionmight benefit from placement of tympanostomy tubes.An association was observed between individual previous prescriptionsof oral antibiotics for acute otitis media among childrenwith tubes. Furthermore, there was an association between overallcommunity antimicrobial use for acute otitis media and the cumulativeprevalence of tympanostomy tube placement among childrenin the community (IV). Of special interest was that the prevalenceof tympanostomy tubes decreased in areas with decreasing use ofantimicrobials for acute otitis media (IV). This observation, however,was only statistically significant in one area, between 1998 and2003, although similar time trend changes were also observed for theother areas. This was also in accordance with parental attitude towardrestrictive antimicrobial prescription policy. This phenomenonmay have different underlying explanations.One possible causative correlation may be explained partly by thefact that children having tubes had got recent oral antimicrobials foracute otitis media more often than children not having tympanostomytubes. This may be due to the fact that otorrhea is a commonproblem in children with tympanostomy tubes (Ah-Tye et al. 2001).This may lead to prescriptions of oral antibiotics due to suspicion ofacute otitis media. In our study, we did not analyse the use of topicalantibiotics, such as ear-drops, that are also frequently used andrecommended as a first line therapy in clinical guidelines for thisproblem.The possibility of a positive causative correlation between antimicrobialdrug (over) use for acute otitis media, further episodesof acute otitis media and tympanostomy tube placement later maybe explained in connection with changes in the microflora of thenasopharynx by antimicrobias. Three different scenarios can be postulated:1. The majority of pneumococcal acute otitis media events maydevelop in association with newly acquired carriage of pneumococcus(Gray et al. 1980; Syrjanen et al. 2005). Eradicationof susceptible pneumococcus in the nasopharyngeal floraby antimicrobials means that new strains will emerge thereaf-

69ter and hence may increase the likelihood of new episodes ofacute otitis media.2. A rapid selection of PNPS isolates during antibiotic treatmentfor acute otitis media as has been shown in some studiesas mentioned earlier (Dagan et al. 1998 a; Brook and Gober2005) or after treatment (Arason et al. 2002 a; McCormick etal. 2005) (See discussion on pages 60-62).3. Frequent use of antimicrobial drugs probably leads to changein the bacterial flora in the community by promoting the emergenceof resistant bacteria. This and no. 2 is associated witha decreased rate of successful eradication of pathogens frommiddle-ear fluid, which is associated with clinical failure,chronic middle-ear effusion and risk of relapsing acute earsymptoms (Reichler et al 1992; Dagan 2000; Brook and Gober2005; Libson 2005) (See also discussion in the next chapter).Another explanation for the correlation between antimicrobialuse for acute otitis media and prevalence of tympanostomy tubeson community level may be non-causative. Differences in medicalpractice both for antimicrobial prescribing and threshold indicationsfor tympanostomy placements among otitis-prone children andchanges overtime because of intervention strategies to lower antimicrobialuse in some practices as described earlier is one possibleexplanation of the correlation (Gabbay and le May 2004; Petursson2005 a). It must also be kept in mind, although an unlikely explanationconcerning our results in a small country that the incidence ofrespiratory tact infections may vary.Acute otitis media in relation to antimicrobial-resistant bacteriaOur results specifically show rapid selection of PNSP isolates afterantimicrobial treatment because of acute otitis media, as has alsobeen shown in other studies during treatment (Dagan et al. 1998 a;Brook and Gober 2005). This may increase the risk of treatmentresistantepisodes of acute otitis media and chronic effusion in themiddle-ear (Reichler et al. 1992; Dagan 2000; Brook and Gober2005; Libson 2005) as mentioned above. One study in the 1970s,showed that when acute otitis media was treated with a broad-spec-

70trum antibiotic, it relapsed more often than after a course of narrowspectrumantibiotic (Howard et al. 1976). The incidence of recurrentacute otitis media increased three-fold in Finland from 1978/1979to 1994/1995, at the same time as penicillin-V was replaced withbroad-spectrum antibiotics as the first-line drug without any obviouschange in microbial ecology that would justify the shift (Joki-Erkkilaet al. 2000). However, I can not draw any safe conclusion from ourstudies concerning the question of whether resistant bacteria increasethe risk of new episodes of acute otitis media more often, comparedwith the risk of a new episode due to non-resistant bacteria.Tympanostomy tubes and bacterial antimicrobial resistanceThe potential association between tympanostomy tube placementsand antimicrobial resistance was not specifically studied. However,it may be concluded, in agreement with what was stated above aboutthe associations between antimicrobial use and resistance and aboutantimicrobial use and tympanostomy tubes placements in the studyareas, that there is probably a indirect association between tympanostomytube placements and the prevalence of bacterial antimicrobialresistance in the community (see discussion above). Our results,however, do not support a conclusion that frequent use of tympanostomytubes protects against antimicrobial resistance.Limitations in the study designI have mentioned some strengths of our studies, one being that it isbased on subjects from different well-defined communities, allowingconclusions, based on the population level as well as differences inclinical practice in Iceland. However, the study samples are limitedas they are focused on pre-school children, and also limited to antimicrobialuse, mostly because of diagnosed upper respiratory tractand middle-ear infections by GPs in primary healthcare settings.Diagnosis of precise acute otitis media can be hard to define anddiffer also by national perspectives and specialty (Rosenfeld 2002).A child with a bacterial upper respiratory tract infection often has aclinical picture of symptoms involving more than one site, includingthe middle-ear, nose and throat. One diagnosis (acute otitis media)may therefore be used more often than others as a primary reason for

antimicrobial prescription among GPs in ordinary clinical settingswhen prescribing antimicrobials is deemed to be needed. Furthermore,only bacteria from the nasopharynx have been cultured, andthe culturing of bacteria has focused on pneumococci. This makes itimpossible to conclude anything about adults, other infections, andbacteria other than pneumococci and the resistance patterns of bacteriaother than pneumococci. On the other hand, this focus on aspecified population, specified infections and a specific bacteriummay also be a strength as confounding factors can be expected to beless important.In our studies we used antibiotic susceptibility testing togetherwith serotyping to characterise the bacterial isolates of pneumococcias a phenotypes. Although it is probably true that PNSP of multiresistantserotype 6B are members of the Spain 6B -2 clone, antibiotype andserotype alone are not enough to draw a definitive conclusion. Molecularmethods, such as pulsed-field gel electrophoresis and multilocussequence typing for DNA fingerprinting would be the only methodssuitable for drawing a definitive conclusion about the clonal origin ofthe multiresistant 6B strain to the Spain 6B -2 clone. The non-typeablepneumococci in the 2003 study (V) all had a rough appearance andare therefore probably non-encapsulated, although this has not beenconfirmed with molecular investigations. A clonal origin for this nontypeablepneumococci is therefore also hard to define.Summary of associations studiedFigure 4 shows some potential associations analysed in this thesis.These potential associations have been discussed, and Figure 26summarises this discussion.Recent antimicrobial use is the most consistent and important riskfactor for the carriage of resistant pneumococci at each time (I, II,V), and the choice of antimicrobial class may influence the selectiveenvironment, favouring particular resistant clones (I, V). It seemsthat age was strongly associated with the carriage of PNSP in thefirst study but not at all in the third one. Neither did gender (I, II V),number siblings (I, II, V), day care (I, II, V), history of tympanostomytubes (II, V), presence of an upper respiratory tract infection (I)and smoking in the household of the index child (V).71

72Antimicrobialuse for acuteotitis mediaTotalantimicrobial use)Antimicrobialresistancedevelopmentamongpneumococci(spreadselection)(Parentalview()TympanostomytubeplacementFig. 26. Conclusions concerning potential associations and their directions.An association was observed between individual previous prescriptionsof oral antibiotics for acute otitis media and younger age,living in a high antimicrobial consumption area and among childrenwith tubes (IV), between day care attendance and children havingtubes (IV) and between overall community antimicrobial use foracute otitis media and the cumulative prevalence of tympanostomytube placement among children in the community (IV).Parents’ expectations of antimicrobial prescriptions for their childbecause of acute otitis media were associated with former antimicrobialuse (III) and by living in area with high antimicrobial utilization(III, IV).A bidirectional arrow means that our studies provide some direct(causative) or indirect (non-causative) support for such a relationship,and a bracketed arrow means that there is a probable association,although one not covered by our studies.As far as I know, this is the first time that such associations for

these subjects have been studied in the general population. However,I am well aware that our data can never allow final conclusions concerningcausal relationships between the factors studied.73

74SUMMARY OF AIMS, MAIN RESULTSAND CONCLUSIONSSome specific aims were stated in the introductory chapter. Theyare repeated below along with the relevant main findings from ourstudies.• To describe the total use of antimicrobials in the communities,specifically among pre-school children, by class of antimicrobials,amount prescribed and prescription rate in selected, well-definedcommunities.Repeated cross-sectional studies have enabled us to observe possibletrends over time regarding antimicrobial use over a 10-yearperiod. Prudent antimicrobial use was encouraged, especiallyfor upper respiratory tract infections and acute otitis media. Thenumber of antimicrobial courses prescribed to pre-school childrendiminished markedly, especially for acute otitis media, butvaried between study areas, indicating that in areas where the prescriptionrate is high, GPs prescribe broad-spectrum antimicrobialsrelatively more often than narrow-spectrum antimicrobials.• To describe potential links between antimicrobial treatment foracute otitis media, socio-demographic factors and parental viewson the use of antimicrobials.The child’s age and residence were independently associated withthe number of treatments for acute otitis media. Parents’ expectationsof antimicrobial prescriptions for common colds were associatedwith the doctor’s handling of upper respiratory tract infections.It is concluded that antimicrobial prescriptions may bemore common in areas where parents have such expectations.• To describe the use of tympanostomy tube placements and possibleassociation with the use of antimicrobials among children.The cumulative prevalence of tympanostomy tube placementsamong pre-school children is very high in Iceland (over 30%).An association was observed on the community level between

75the prescription of oral antimicrobials, specifically for acute otitismedia, and the cumulative prevalence of tympanostomy tubeplacements. Of special interest was the observation that the prevalenceof tympanostomy tubes decreased significantly in areaswhere the use of antimicrobials for acute otitis media decreased,and increased where the use of antimicrobials was highest. Thepossibility of a causative, positive correlation between antimicrobialdrug (over)use for acute otitis media, future episodes of acuteotitis media and tympanostomy tube placement later, warrantsfurther investigation. Differences in routine medical practice maybe a possible non-causative explanation of the correlation.• To analyse associations between antimicrobial use and nasopharyngealcarriage of PNSP in children with regard to both individualuse and total use in the community.There was a strong association between antimicrobial use on anindividual level and the nasopharyngeal carriage of PNSP in allthree phases of our studies. The results indicate that this associationcannot be solely explained by (selective) antimicrobialpressure on penicillin-susceptible strains. It is proposed that “selectiveacquisition” of (foreign) non-susceptible strains from theouter ecosystem together with unmasking of dormant and/or nonsusceptiblestrains present in very low numbers from the innerecosystem could also be a possible explanation. Nevertheless, theinterplay between antimicrobial use on a community level andclonal spread of non-susceptible pneumococci is harder to explain(see next paragraph).• To describe the clonal spread of PNSP in communities and analysethe interplay of factors contributing to this spread.The PNSP strain of multiresistant type 6B (phenotypically identicalby antibiotic susceptibility testing to the Spain 6B -2 clone)appeared and disappeared over a 10-year period in the communities,both in communities with high and low antimicrobial use.This probably reflects the strain’s fitness to spread where herd immunityof the population is lacking. We conclude that the spreadof resistant clones within well-defined areas seems to follow a

76classical “rise and fall” epidemiological pattern. The extent of antimicrobialuse may determine both the peak prevalence and thesubsequent endemic prevalence in the community. The choice ofantimicrobial class may influence the selective environment, favouringparticular resistant clones.

CLINCAL IMPLICATIONS77The prescription of antimicrobials for children has decreased considerablyin some of the study communities, particularly prescriptionsfor acute otitis media. In some areas the decrease is dramatic.I believe that GPs in some of the areas studied greatly changed theirprescription patterns for antimicrobials immediately after the firstphase of this study in 1993 because of the study’s findings regardingthe risk of development of bacterial resistance in the community.Antimicrobial use for acute otitis media, however, is still about50% of all antimicrobial prescribing today for children in Iceland. Insome areas the parents are well informed about the consequences ofuncritical antimicrobial use, and in these areas the parents are alsomore prepared to wait before starting antimicrobials for their children.This indicates the importance of getting information to parents aboutthe appropriate management of infectious diseases, especially in casesof mild symptoms because of acute otitis media.The use of tympanostomy tubes is commoner in Iceland than inother comparable countries. Our studies indicate that the use of tympanostomytubes does not lead to less use of antimicrobials, eitherin children as a whole or, specifically, in the children with a currenthistory of tympanostomy tubes. Our results also demonstrate an associationbetween the use of antibiotics and use of tympanostomy tubeplacements. However, it is impossible to say whether this associationis due to causal effects or differences in the routine medical practice orboth. These observations may warrant further discussion on optimaltreatment to achieve a consensus on such treatment of middle-ear infectionsand other upper respiratory tract infections.For small communities the spread of resistant clones appears to bethe main reason for rapid and significant changes in pneumococcalresistance rates. Herd immunity against new strains of PNSP seemsto appear within a certain period, even where the consumption of antimicrobialsis high. The extent of antimicrobial use may determineboth the peak prevalence and the subsequent endemic prevalence inthe community. Recent antimicrobial use by direct (selective) antimicrobialpressure on susceptible strains, “selective acquisition” of

78(foreign) non-susceptible strains from the community and unmaskingof dormant non-susceptible strains present from the inner ecosystem,is the most consistent and important risk factor for carriage of theseresistant strains.Associated with a decreased rate of successful eradication of pathogensfrom middle-ear fluid because of antimicrobial resistance amongthem is a tendency toward chronic middle-ear effusion and risk ofrelapsing acute ear symptoms. The positive effect of decreased antibioticuse on antibiotic resistance may outweigh the possible benefitof earlier symptom resolution attributed to antibiotic treatment in thecase of mild acute otitis media.Eradication of the susceptible pneumococcus in the nasopharyngealflora and interference on the natural balance of microbial speciesin the nasopharynx by antimicrobials means that new strains willemerge thereafter and hence may also increase the likelihood of newepisodes of acute otitis media.“Preventing recurrent acute otitis media is a goal of child healthcare.The objective is to reduce the frequency of pain and fever becauseof otitis media, shorten the duration of hearing loss, reduce thecosts of physician visits, surgery and drugs, reduce parent anxiety andprevent long-term sequelae” (Giebink 2000). Identification of risk factorsfor acute otitis media and antimicrobial-resistant pneumococcalcolonisation of the nasopharynx together with the possible use of thenew protein-polysaccharide conjugate pneumococcal vaccine againstthe most potential pathogenic strains of pneumococci, although it hasnot yet been used in Iceland, provides new opportunities for preventingand managing acute otitis media and other pneumococcal diseasesamong children in the future. Efforts to improve the judicious use ofantimicrobials for acute otitis media should focus on improving diagnosticaccuracy. There is also a need to use qualitative methods toprepare information and to understand factors influencing behavioralchange among antimicrobial prescribers.Our results indicate that the uncritical use of antibiotics increasesthe risk of developing antimicrobial resistance. Therefore, prudent useof antimicrobials is recommended.

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MICROBIALDRUGRESISTANCEVolume8,Number3,2002© MaryAnnLiebert,Inc.ClonalSpreadofResistantPneumococciDespiteDiminishedAntimicrobialUseVILHJALMURA.ARASON, 1 ADALSTEINN GUNNLAUGSSON, 2 JOHANN A.SIGURDSSON, 1HELGAERLENDSDOTTIR, 2 SIGURDURGUDMUNDSSON, 3 andKARLG.KRISTINSSON 2ABSTRACTTheeffectsofcommunity-wideinterventionstoreduceresistanceratesarepoorlyunderstood.Thisstudyevaluatedtheeffectofreducedantimicrobialusageonthespreadofpenicillin-nonsusceptiblepneumococci(PNSP)infourcommunitiesinIceland.Thestudywasperformedafterinterventionstoreduceantimicrobialusageandcomparedtoanidenticalstudyperformed5yearsbefore.Arandomizedsampleof953childrenwaschosenfromall2,9001-to6-year-oldchildrenlivinginfourwell-definedcommunities.ThemainoutcomemeasureswerenasopharyngealcarriageofPNSPandindividualandcommunityuseofantimicrobials.Pneumococciwerecarriedby51.7%ofthe743childrenenrolled,and8.1%ofthepneumococciwerePNSPasopposedto 8.5% in the previous study. The antimicrobial use of participants had been reduced from 1.5 to 1.1courses/yearandtheoveralluseamongchildren,7yearsoldlivinginthestudyareasfrom13.6to11.1defineddailydosages/1000childrenperday.TheprevalenceofPNSPincreasedinthetwoareasfurthestawayfromthecapitalareadespitereducedconsumption.ThemajorriskfactorsforcarriageofPNSPremainedthesame.Interventionscanbeeffectiveinreducingantimicrobialuse.Pandemicmultiresistantclonescanalsospreadfastinsmallcommunitieswithlowantimicrobialuse,wheretheirappearancemaybedelayedcomparedtohighlypopulatedurbanareas.Clonalspreadandherdimmunityareimportantfactorstobeconsideredintheevaluationofinterventioneffects.INTRODUCTIONCOMPARATIVE AND ANALYTICAL STUDIES havedemonstratedarelationshipbetweenhighantibioticconsumptionandincreasingdrugresistance.Thiscorrelationhasbeenfoundbothforindividualantimicrobialuse 1,13 andantimicrobialuse bywholecommunities. 1,15–17 However,theeffectofreducedantimicrobialconsumptionontheprevalenceofresistancehasnotbeenclearlydocumentedonacommunitywidescale.The incidence of penicillin-nonsusceptible pneumococci(PNSP) increasedrapidlyin Icelandfrom 1989 6 until 1993,whenithadreached20%inpneumococcalinfections. 7 MostofthePNSPbelongedtoasinglemultiresistantserotype6Bclone(theSpanish-Icelandicclone,Spain-2 6B ). 18 Astudyperformedin1993toevaluateriskfactorsforcarriageofPNSPdemonstratedthatantimicrobialusewasanimportantriskfactor,andsuggestedthattheuseoftrimethoprim-sulfamethoxazoleandmacrolidesmightbeworsethanuseofotherantimicrobials. 1Thiswasfollowedbyanationwidecampaigntoreduceunnecessaryantimicrobialuseforupperrespiratorytractinfections,mainlyinchildren. 9 TheinterventionsconsistedbothofinformationandeducationofthepublicthroughmassmediaandofphysiciansthroughmeetingsandtheIcelandicMedicalJournal.NewantimicrobialprescriptionguidelineswerepreparedandmadeavailableontheInternet.Prudentantimicrobialusewas encouraged,especiallyforupperrespiratorytract infections.Theseeffortsresultedina35%reductionintheuseofliquidantimicrobialsfororalusebychildrenfrom1992until1997(datafromtheMinistryofHealth).SubsequentlytheoverallincidenceofPNSPinpneumococcalinfectionsinIcelanddeclinedto12%in1997. 2,9TherearemanyfactorsotherthanantimicrobialusethatcanplayaroleinthespreadofPNSP. 8 Theinterplaybetweentheseriskfactorsmaybecomplexandispoorlyunderstood.Studiesevaluatingthisinterplayinthecommunityareurgentlyneededtoassistpublichealthofficialsindesigningeffectiveinterven-1 DepartmentofFamilyMedicine,UniversityofIceland,Solvangur,Hafnarfjordur,Iceland.2 DepartmentofClinicalMicrobiology,LandspitaliUniversityHospital,Reykjavik,Iceland.3 DirectorateofPublicHealth,Reykjavik,Iceland.187

188tionstrategiestocurtailtherapidlyincreasingresistancerates.TheconfinedIcelandiccommunityisidealforsuchstudies.Togetabetterunderstandingoftheinterplayofriskfactorsandtime,theaimofthisstudywastoanalyzetheeffectofdiminishedantimicrobialuseonindividualriskfactorsandtheprevalenceofPNSPinthesamecommunitiesaswerestudiedinIcelandin1993.1 MATERIALSANDMETHODSStudypopulationanddesignFouroffivegeographicalareasthathadbeenstudiedinacomparativestudyin1993 1 couldbere-examinedin1998.Attheendof1997(December1,1997),theseareashadatotalpopulationof27,013,including2,900childrenfrom1to6yearsold,e.g., Hafnarfjordur(H),18,203inhabitants,1,989children1–6yearsold.Correspondingfiguresfortheotherareaswere:Vestmannaeyjar(V),4,640and512;Egilsstadir(E),3,076and300;andBolungarvik(B),1,094and99.AreaHisatownadjacenttothecapital(Reykjavik),areaVafishingtownonanislandofthesouthcoast,areaEatownsurroundedbyalargefarmingarea,andareaBafishingtown(Fig.1).Thepopulationdensityandlivingstandardsaresimilarinallthestudytowns.Thestudypopulationwaschosentoallowarepresentativecomparisonwiththe1993studyperformedintheseareas.Aftercomputerrandomizationofall1-to6-year-oldchildrenidentifiedfromtheNationalRegistryoftheseareas,953children(33%ofthechildrenofthatage)wereselectedforparticipation(H,20%;V,58%;E,63%;andB,62%).Seventeengeneralpractitioners,ofwhom14werethesameasinthe1993study,servedtheseareas.ThesiteswerevisitedinAprilandMay,1998(sametimeoftheyearasinthe1993study).Afterinformedparentalconsent,anasopharyngealspecimenwastakenfromeachchild.Parentswereaskedtobringtheirchildtothelocalhealthcenterorthesamplewasobtainedattherelevantdaycarecenter.Theparentswerealsoaskedthefollowingquestionsregardingantimicrobialuseoftheirchild:numberofantimicrobialcoursesintheprecedingyear;thedateandtypeofthelastantimicrobialagentused;typeofinfectionandwhetherthechildhadbeentakingprophylacticantibiotics$3weeksduringtheprecedingyear.Thesameinformationwasalsocollectedfromthemedicalrecordsatthelocalhealthcenter.Childrenthathadreceivedantimicrobialtreatment in the preceding 2 weeks were excluded,asinthepreviousstudy.The NationalBioethicsCommitteeandtheNationalDataProtectionCommission,Iceland,approvedthestudy.MicrobiologyARASONETAL.Nasopharyngealsampleswereobtainedwitharayon-tippedswab(Mini-tipCulturette ® ,BectonDickinsonandCo.,Sparks,MD),storedformaximumof24hrbeforetheywereinoculatedontwobloodagars(Difco,Detroit,MI)onecontaininggentamicin(5mg/L)andincubatedanaerobicallyandtheotherincubatedaerobicallywithaddedCO2 .Colonieswereidentifiedwith conventionalmethods,andpneumococciwere screenedforpenicillinresistancebytheoxacillindiscdiffusiontest 19 andtheMIC of nonsusceptibleisolatesdeterminedby theE-test(ABBiodisk,Solna,Sweden)accordingtothemanufacturer’srecommendations.Susceptibilitytoerythromycin,tetracycline,chloramphenicol,andtrimethoprim-sulfamethoxazolewasdeterminedbydiscdiffusiontestsaccordingtotheNCCLSmethodsand criteria. 5 Penicillin nonsusceptible isolates wereFIG.1.MapofIcelandshowingthemajorroads,Reykjavik,Akureyri,andthestudysites.

ANTIMICROBIALUSEANDCLONALSPREAD 189serotypedbyco-agglutination 11 usingantiserafromtheStateSeruminstitute(Copenhagen,Denmark).AntimicrobialsusceptibilitiestootherantimicrobialsweretestedbydiscdiffusiontestsusingtheNCCLSmethodsandcriteria. 5AntimicrobialsalesInformationontotalantimicrobialsales(adultsandchildren)wascollectedfromcomputerizedrecordsofthelocalpharmaciesinthestudyareasforthe12monthsprecedingthestudyvisits(May,1997,toApril,1998).Thesaleswereassumedtorepresenttheantimicrobialuseandcalculatedinnumberofdefineddailydosesper1,000inhabitantsperday(DDD/1000inhabitantsperday).21 Inaddition,theantimicrobialsalesfortheagegroup0–6yearswereanalyzedseparatelybylookingattheamountprescribedofthemajorantimicrobialclassesandtheamountineachprescription(calculatedasthemeannumberofDDDsperprescription).StatisticalanalysisNasopharyngealcarriageRESULTSThesingleoutcomevariablewascarriageofPNSPpenicillinsusceptiblepneumococci(PSP).Thevariablesofsex,age,areaofresidence,siblings,daycareattendance,thelastantimicrobialagentused,2–7or8–52weeksfromlastantimicrobialtreatment,thenumberofcoursesinthepreceding12months,anduseofprophylacticantibioticswereexaminedforassociationwiththeoutcomevariable.TheFisher’sexacttestswereusedfor univariateanalysisof categoricalvariablesand one-wayanalysisofvariance(ANOVA)forcontinuousvariables.Multivariate logistic regression by backward stepwisemethodwasusedtoestimatetheriskofcarryingPNSPtocontrolinterdependence. IndividualregressioncoefficientsweretestedwiththeWaldstatistic,andconfidenceintervalscalculatedfortheodds.ThemultivariateanalyseswereperformedwiththeSPSS ® programforWindows(AdvancedStatisticsRelease8.0,SPSSInc,Chicago,IL).Thelevelofstatisticalsignificancewastakenas0.05.Ofthe953childreninvitedtoparticipate,743(78%)participated(H,301,75%;V,224,76%;E,167,88%;andB,51,83%)and384(52%)carriedpneumococci.Thepneumococcalcarriageratevariedfrom37%to58%(H,58%;V, 54%;E,41%;andB,37%).Themeanageforthewholegroupwas4.2years(95%CI4.1–4.3)andtheagerangedfrom1to6years[V, 4.2 (4.0–4.5); B, 4.2 (3.8–4.7); E 4.1 (3.8–4.4); H 4.2(4.0–4.4)].Theproportionofpneumococcithatwasnonsusceptibletopenicillinwas8.1%andallofthenonsusceptiblestrainsexcepttwoweremultiresistantandofserotype6B(i.e.,phenotypicallyidenticalto theSpanish–Icelandicclone). 18,20 ThesemultiresistantstrainswerefoundinallstudyareasandtheirpenicillinMICswerethefollowing:onestrain,0.125mg/L, 21strains0.5mg/L,sixstrains1.0mg/L,andonestrain2.0mg/L.Thetwo other strains were only found in area H; one was ofserogroup9(MIC1mg/L)andtheotherofserogroup19(MIC0.5 mg/L), both resistant to trimethoprim-sulfamethoxazole.Therewasamarkeddifferencebetweentheresistanceratesofthestudyareas,withratesrangingfrom4.1%to18.8%.Therateshadalsochangedsignificantlyfromthe1993rates(Table1),withreducedresistanceratesinthetwoareaslocatedinthesouthwest(HandV),butanincreasedrateinthetwoareasfurthestawayfromthecapitalarea(BandE).PNSPwerefoundinalldaycarecentersinareaE.ThePSPwereallsusceptibletochloramphenicolandnonsusceptibilitytoerythromycinandtetracyclineremaineduncommoninthesestrains(Table2).AllPNSPwerenonsusceptibletotrimethoprim-sulfamethoxazole,andapproximatelyone-quarterofthePSP.AntimicrobialuseBythewholepopulationinthestudyareas: In1998,atotalof15,153antimicrobialprescriptionsweredispensedtothein-TABLE 1.CARRIAGE OF PNEUMOCOCCI (PNC)AND PNSP AND THE NUMBER OFANTIMICROBIAL (AM)COURSES PER YEAR IN THE STUDY GROUPSDDD/1000children,7yrs/day DDD/prescriptionNo. No. No. AMcoursesperArea Year children PNC(%) PNSP (%) year(95%CI) Total PEN AMP ERY SXT PEN AMP ERY SXTH 1993 527 280(53.1) 24(8.6) a 1.5(1.4–1.7) 11.9 2.2 7.0 0.5 2.2 3.7 4.4 2.7 2.41998 301 174(57.8) 11(6.3) a 1.0(0.8–1.1) 9.9 1.3 7.3 0.5 0.8 3.7 4.4 2.5 2.8V 1993 100 55(55.0) 10(18.2) a 1.7(1.2–2.1) 23.2 3.5 9.7 2.9 7.1 3.6 4.2 3.0 2.41998 224 122(54.5) 5(4.1) a 1.4(1.1–1.6) 17.1 1.8 13.0 0.9 1.4 4.5 4.3 2.7 2.5E 1993 111 52(46.8) 1(1.9) a 1.3(1.0–1.6) 13.4 2.4 7.0 0.5 3.5 4.6 3.9 3.3 2.31998 167 69(41.3) 13(18.8) a 0.9(0.7–1.1) 7.6 1.2 5.2 0.2 1.0 3.7 4.4 2.8 2.4B 1993 53 39(73.6) 1(2.6) a 1.5(1.0–2.0) 9.6 2.5 4.3 0.6 2.2 3.2 4.1 2.7 2.11998 51 19(37.3) 2(10.5) a 1.0(0.6–1.4) 8.3 0.5 5.9 0.0 1.9 5.0 3.4 — 2.0Total 1993 791 426(53.9) 36(8.5) a 1.5(1.4–1.6) 13.6 2.5 7.3 0.8 3.0 3.7 4.3 2.9 2.41998 743 384(51.7) 31(8.1) a 1.1(1.0–1.2) 11.1 1.3 8.3 0.5 1.0 3.9 4.3 2.6 2.6a p , 0.01.Thecorrespondingfiguresfromthe1993studyareshownforcomparison.Theuseofthemainantimicrobialclasses(indefineddailydosages[DDD];penicillin[PEN],ampicillin[AMP],trimethoprim-sulfamethoxazole[SXT],anderythromycin[ERY])bychildren,7yearsoldlivinginthestudyareasisshownontheright-handside,togetherwiththemeannumberofDDDsperperscription.

190ARASONETAL.TABLE 2.NUMBER OF PNEUMOCOCCI NONSUSCEPTIBLE (RESISTANT OR INTERMEDIATE)TO ERYTHROMYCIN (ERY),TETRACYCLINE (TET),CHLORAMPHENICOL (CHL),AND TRIMETHOPRIM-SULFAMETHOXAZOLE (SXT),ACCORDING TO DISC DIFFUSION TESTS,IN 1993AND 1998,IN THE RESPECTIVE AREASNo. No. No. No.Area Year ERY (%) TET (%) CHLO (%) SXT (%)H PSP 1993 0 0 1 3.0 0 0 62 24.41998 1 0.6 1 0.6 0 0 46 28.8PNSP 1993 20 83.3 22 91.7 13 81.3 24 1001998 7 63.6 8 72.7 8 72.7 11 100V PSP 1993 2 4.4 2 4.4 0 0 17 37.81998 0 0 0 0 0 0 25 20.7PNSP 1993 9 90.0 9 90.0 10 100 10 1001998 5 100 5 100 5 100 5 100E PSP 1993 0 0 0 0 0 0 12 23.51998 4 7.1 2 3.6 0 0 10 17.9PNSP 1993 1 100 1 100 1 100 1 1001998 13 100 13 100 13 100 13 100B PSP 1993 0 0 0 0 0 0 6 15.81998 2 11.8 2 11.8 0 0 12 70.6PNSP 1993 1 100 1 100 1 100 1 1001998 2 100 2 100 1 50.0 2 100Total PSP 1993 2 0.5 3 0.8 0 0 97 25.01998 7 2 5 1.4 0 0 93 26.6PNSP 1993 31 86.1 33 91.6 25 69.4 36 1001998 27 87.1 28 90.3 27 87.1 31 100habitantsof thetargetareas by thelocal pharmacies,correspondingto14.2DDD/1000inhabitantsperdayinareaH,17.2inareaV,12.3inareaEand11.5inareaB.Ofthese,3,347(22.1%)wereforchildrenunder7yearsold.Comparedtothe1993study,antimicrobialconsumptionhaddiminishedinallstudyareasbothasmeasuredindefineddailydoses(14–43%)andasnumberofantibiotictreatmentcoursesperyear(9–50%).ThegreatestreductionwasseeninareaE(Table1).ChildreninareaVstillconsumedaround50%moreantimicrobialsthanchildrenintheotherareas.Thereductioninantimicrobialusewasgreaterfortrimethoprim-sulfamethoxazolethanforotherantimicrobials.Inthreeoftheareas(H,V,andB),therewasaslightincreaseintheuseofbroad-spectrumpenicillins(mainlyamoxycillin and amoxycillin with clavulanicacid). Overall,therewasnochangeinthenumberofDDDsperprescription,andtherewereonlyrelativelysmallchangeswithintheareaswithoneexception.InareaB,therewasalmosta50%increasein theaverageamountprescribedfornarrowspectrumpenicillins(mainlyphenoxymethylpenicillin)(Table1).By the studypopulationalone: The meannumberof antimicrobialcoursesperchildinthestudypopulationwas1.1duringtheyearprecedingthesampling(95%CI1.0–1.2).Thiswas a 26.7%reductioncomparedto comparabledataof the1993study(Table1).Fortypercentofthechildren(298)hadreceivedantimicrobialsatleastonceduringtheprecedingyear,comparedto65%in 1993.In both1993and1998,theconsumptionwaslowestinareaEandhighestinareaV.Acuteotitismediawasstillbyfarthemostcommonreasonforantimicrobialprescriptions, constituting 55% of all antimicrobialprescriptions(65%in1993).Thenumberoftreatmentsforotitismediaperchildhaddiminishedfrom1.0(95%CI0.9–1.1)in1993to0.6(0.5–0.7)in1998.In1993trimethoprim-sulfamethoxazolewasthemostcommonlyrecentlyprescribedan-timicrobial agent (50.1%) but not in 1998 (11.8%) (p 50.0001).FactorsassociatedwithcarriageofPNSPByunivariateanalysis,youngage(p 5 0.013),geographicallocation(areaE;p 5 0.003),prophylacticantimicrobialtreatment(p5 0.008),antimicrobialtreatmentforotitismedia(p 50.001),totalnumberofantimicrobialtreatmentcourses(p ,0.0001),and,8 weeksfrom lastantimicrobialcourse(p 50.002),weresignificantlyassociatedwithPNSPcarriage.ThePNSP carriagerate was 21.6% (11/51) 2–7 weeks after antimicrobialtreatmentcomparedto5.6%(8/142)8–52weeksaftertreatment(p5 0.002)or6.3%(12/191)ifnotreatmenthadbeen received(p 5 0.001).The same risk factors were alsoidentifiedinthe1993study,butnotthesamegeographicallocations.FactorsthatwerenotfoundtobesignificantlyassociatedwithPNSPcarriageweregender,numberofsiblings,daycareattendance,andantimicrobialcoursesfortonsillitisandsinusitis.Thenumbersweretoosmalltoassesstheriskofindividualantimicrobialclasses.Tocontrolforconfoundingfactors,allsignificantvariablesfromtheunivariateanalysiswereusedinamultivariatebackwardstepwiselogisticregressionmodel.Number of antimicrobialtreatmentsandgeographicalarea(areaE)weretheonlyindependentriskfactorsforcarriageofPNSP(Table3).DISCUSSIONThenationwidecampaigntoreduceunnecessaryantimicrobialuseforupperrespiratorytractinfectionsinchildrenthattookplacebetween1993and1998wasassociatedwithasig-

ANTIMICROBIALUSEANDCLONALSPREAD 191TABLE 3.RISK (ODDS RATIO)OF CARRYING PNSP AS OPPOSED TO PSPBY BACKWARD STEPWISE LOGISTIC REGRESSION METHODVariable Number OR 95%CI p valueResidenceAreaH 170 1(referencearea)AreaV 122 0.519 0.17–1.620 0.2600AreaE 67 4.139 1.65–10.39 0.0030AreaB 19 1.852 0.36–9.500 0.4600Numberofantimicrobial 378 1.50 1.23–1.820 0.0001treatmentsOverallsignificance:x 2 5 25.49,df5 4,p, 0.0001.nificantreductioninantimicrobialusebychildreninthestudyareas(from13.6to11.1DDD/1000children,7yearsoldperday)andinthestudypopulations(1.5–1.1antimicrobialcoursesperyear).This reductionwas mainlydueto reduceduseoftrimethoprim-sulfamethoxazoleandfewerprescriptionsforotitismedia(from1.0to0.6prescriptionsperyear).Despitethisreductioninantimicrobialuse,theproportionofPNSPcarriageonlydeclinedto8.1%,fromthecorrespondingfigureof8.5%,obtainedinthecomparablestudyperformedin1993. 1 ThisisincontrastwiththemuchgreaterreductionintheincidenceofPNSPobservedinspecimenssubmittedfrompatientsfromthewholeofIceland(i.e., 20–13%),wherethemajority(.80%)ofthespecimenscamefromthecapitalarea. 8 Inthe1993study,oneofthemainriskfactorsforcarryingPNSPwasrecentantimicrobialuse,1 yet5yearslatertherewasanincreasingPNSPprevalenceinthetwoareasthatnotonlyhadthelowestuseofantimicrobialsbutalsooneoftheseareashadthegreatestreductionintheiruse.Theotherimportantriskfactorswereyoungageandlivinginanareawithhighantimicrobialconsumption,buttheagedistributionofthechildreninthesepopulationsdidnotchangebetweenthestudyperiods.Therefore,animportantvariableislikelytobemissingfromtheriskfactoranalysisinthepreviousstudy.RiskfactorsforPNSP carriagethathavebeendemonstratedbyotherinvestigators(daycarecenterattendance,priorhospitalization,otitis-pronecondition,otitismedianotresponsivetoantimicrobials,whiterace,lowdose,andlongdurationofantimicrobialprescriptions) 10 cannotaccountforthesedifferences.Howcantheapparentcontradictionbetweentheknownriskfactorsandthechangeinprevalenceofresistanceinthesecommunitiesbeexplained?Importantfactorssuchasthespreadofnovelbacterialclonestocommunitieswithlittleornoherdimmunitytothenewcloneshasnotbeenevaluatedinpreviouscommunity-widestudieson antimicrobialresistance.Despitefastmeansoftransportforpeople,thetransferofnewpneumococcalclones is highly time dependent. 14 Internationalclonesarelikelytoappearfirstinhighlypopulatedurbanareasandthenspreadfromtheretoruralareasanddistantandsmallerurbanareas.Reachingremoteruralareasshouldtakeevenlongertime.TheSpanish–Icelandicserotype6BpneumococcalclonefirstappearedinIcelandin1989andwasalmostexclusivelyisolatedfrompatientslivinginthecapitalareaduringthefirst2years.SubsequentlyitappearedandspreadinthetownofAkureyri,whichisthelargesturbanareaoutsidethecapitalarea(389kmbyroad;seeFig.1)(K.G.Kristinsson,unpublisheddata).ThePNSP6BprevalenceinareasEandBwasverylowin1993(1.9and2.6%;onestrainineacharea)comparedtotheotherstudyareasandtheyarealsofurthestawayfromthecapitalarea(seeFig.1).ItisverylikelythatittooktheSpanish–IcelandicclonelongertoreachareasBandEthantheotherareas.Another important observation is the high prevalencereachedbytheSpanish–IcelandiccloneinareaE(18.8%),anareawithlowanddeclininguseofantimicrobials.Thisdemonstratesthatthisclonecanalsospreadfastincommunitieswithlowantimicrobialconsumption,whichprobablyreflectsitsfitnessandlittleornoherdimmunityofthepopulationinthatarea.LowdosageandlongdurationoftreatmenthasbeendemonstratedtoincreasetheriskofPNSPcarriage. 4 ToseeifthiscouldaccountforsomeofthechangesinPNSPprevalence,wecalculatedthenumberofdefineddailydosagesprescribedperprescription.ComparisonofthenumberofDDD/prescription(Table1)showsthatthisisnotlikelytobetheexplanationinthestudyareas.Infectioncontrolmeasuresarealsoimportantinreducingresistancerates 12 andhavebeenshowntobeeffectiveinreducingantimicrobialprescriptionsandresistanceindaycarecenters. 3 InfectioncontrolwasnotpartoftheIcelandicintervention.Oneofthemajorstrengthsofthisstudyistheuseofrandomsampling in unselectedpopulations,high participationrates,andthequalityofthedataingeneral.Thenumberofparticipantswasjustoverone-quarterofall1-to6-year-oldchildrenlivinginthestudyareasandtheactualsalesofallantimicrobialagentsinthestudyareastogetherwiththeindividualuseofantimicrobialsbytheparticipantswasavailableforstudy.ThestudyconfirmedtheriskfactorsforcarryingPNSPdemonstratedinthe1993study,i.e.,antimicrobialuse,timefromlastantimicrobialtreatment,age,andlivinginahighprevalencearea.Again,daycarecenterattendancewasnotariskfactor.Thisisprobablybecauseonly17%oftheparticipantswerenotattendingdaycarecentersandtheirsiblingsand/orfriendsarethereforehighlylikelytobeattendingdaycarecenters,enablingefficienttransmissionfromthedaycarecenters.ThereducedantimicrobialuseislikelytohavecontributedtothereducedprevalenceofPNSPinareasHandVandlimitedtheincreaseinareasBandE.Icelandhasasmallhomogenouspopulationandsomepartsaresparselypopulated.Apartfromthat,it isverysimilartootherwesternEuropeancountries.Themainresultsofthisstudy

192demonstratingthefitnessofaparticularpneumococcalcloneinitsabilitytospreadfastincommunitieswithlittleornoherdimmunityshouldthereforealsobeapplicabletoothercountries.Theimportanceofsuchfitnessisobviousifsuchclonesaremultiresistantand/or virulentandalsofor futurevaccinationstrategies.Interventionscan be effectivein reducingantimicrobialuseinsmallcommunitiessuchasinIceland,buttheymaynotleadtoimmediatereductionsinprevalenceofresistantstrains.Longitudinalepidemiologicalinterventionstudiescarriedoutindifferentareasandassessingallknownandlikelyriskfactorsareneededtoassistpublichealthofficialsfurtherindesigningthemosteffectivestrategiestoreduceresistancerates. Future studies on the epidemiologyof pneumococcalclonesandtheeffectsofinterventionsmustconsidertheeffectofdistance,time,andherdimmunity.ACKNOWLEDGMENTSSpecialthanksareduetoallthechildrenwhoparticipatedinthestudyandtotheirparents.ThisstudywassupportedbytheIcelandicCollegeofFamilyPhysicians,TheResearchFundoftheUniversityofIceland,andtheResearchFundoftheLandspitaliUniversityHospital,Reykjavik.REFERENCES1. Arason,V.A.,K.G.Kristinsson,J.A.Sigurdsson,G.Stefansdottir,S.Molstad,andS.Gudmundsson.1996.Doantimicrobialsincreasethecarriagerateofpenicillinresistantpneumococciinchildren?Crosssectionalprevalencestudy.Br.Med.J.313:387–391.2. Austin,D.J.,K.G.Kristinsson,andR.M.Anderson. 1999.Therelationshipbetweenthevolumeofantimicrobialconsumptioninhumancommunitiesandthefrequencyofresistance. Proc.Natl.Acad.Sci.USA96:1152–1156.3. Ekdahl, K., H.B. Hansson, S. Molstad, M. 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Kristinsson,K.G. 1997.EffectofantimicrobialuseandotherriskARASONETAL.factorsonantimicrobialresistanceinpneumococci.Microb.DrugResist.3:117–123.9. Kristinsson,K.G. 1999.Modificationofprescribers’behavior:theIcelandicapproach.Clin.Microbiol.Infect.5(Suppl.4):43–47.10. Kristinsson,K.G. 2000.Effectofantimicrobialuseandotherriskfactorsonantimicrobialresistanceinpneumococci.In A.Tomasz(ed.),Streptococcuspneumoniae: MolecularBiologyandMechanismsofDisease.MaryAnnLiebertInc.,NewYork,pp.419–425.11. Kronvall,G. 1973.Arapidslide-agglutinationmethodfortypingpneumococcibymeansofaspecificantibodyadsorbedtoprotein-A-containingstaphylococci.J.Med.Microbiol.6:187–190.12. Lipsitch,M.,C.T.Bergstrom,andB.R.Levin. 2000.Theepidemiologyofantibioticresistanceinhospitals:paradoxesandprescriptions.Proc.Natl.Acad.Sci.USA97:1938–1943.13. Melander,E.,S.Molstad,K.Persson,H.B.Hansson,M.Soderstrom,andK.Ekdahl. 1998.Previousantibioticsconsumptionandotherriskfactorsforcarriage ofpenicillin-resistantStreptococcuspneumoniaeinchildren.Eur.J.Clin.Microbiol.Infect.Dis.17:834–838.14. Melander,E.,K.Ekdahl,H.B.Hansson,C.Kamme,M.Laurell,P. Nilsson, K. Person, M. Soderstrom, andS. Molstad.1998.Introductionandclonalspreadofpenicillin-andtrimethoprim/sulfamethoxazole-resistantStreptococcus pneumoniae,serotype9V,insouthernSweden.Microb.DrugResist.4:71–78.15. Melander,E., K. Ekdahl,G.Jonsson,andS.Molstad. 2000.Frequencyofpenicillin-resistantpneumococciinchildreniscorrelatedtocommunityutilizationofantibiotics.Pediatr.Infect.Dis.19:1172–1177.16. Molstad,S.,E.Arvidsson,I.Eliasson,B.Hovelius,C.Kamme,andC.Schalen. 1992.Productionofbetalactamasebyrespiratorytractbacteriainchildren:relationshiptoantibioticuse.Scand.J.Prim.Health.Care.10:16–20.17. Seppala,H.,T.Klaukka,J.Vuopio-Varkila,A.Muotiala,H.Helenius,K.Lager,andP.Huovinen. 1997.Theeffectofchangesintheconsumptionofmacrolideantibioticsonerythromycinresistancein group A streptococci in Finland. N. Engl. J. Med.337:441–446.18. Soares, S., K.G. Kristinsson, J.M. Musser, and A. Tomasz.1993.Evidencefor the introductionof a multiresistantclone ofserotype6BStreptococcuspneumoniae fromSpaintoIcelandinthelate1980s.J.Infect.Dis.168:158–163.19. Swenson,J.M.,B.C.Hill,andC.Thornsberry. 1986.Screeningpneumococci for penicillin resistance. J. Clin. Microbiol.24:749–752.20. Vilhelmsson,S.E.,A.Tomasz,andK.G.Kristinsson. 2000.Molecularevolutioninamultidrug-resistantlineageofStreptococcuspneumoniae: emergenceofofstrainsbelongingtotheserotype6BIcelandicclonethatlostantibioticresistancetraits.J.Clin.Microbiol.38:1375–1381.21. World Health Organisation. 1992. Anatomical TherapeuticalChemical(ACT)classificationindexincludingdefineddailydoses(DDDs)forplainsubstances.Oslo:WHOCollaboratingCentreforDrugStatisticsMethodology.Addressreprintrequeststo:Dr.KarlG.KristinssonDepartmentofMicrobiologyLandspitaliUniversityHospitalP.O.Box1465121Reykjavik,IcelandE-mail: karl@landspitali.is

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Pediatr Infect Dis J, 2002;21:1110–15 Vol. 21, No. 12Copyright © 2002 by Lippincott Williams & Wilkins, Inc.Printed in U.S.A.Tympanostomy tube placements,sociodemographic factors and parentalexpectations for management of acute otitismedia in IcelandVILHJALMUR A. ARASON, MD, JOHANN A. SIGURDSSON, MD, PHD, KARL G. KRISTINSSON, MD, PHD ANDSIGURDUR GUDMUNDSSON, MD, PHDAccepted for publication July 25, 2002.From the Department of Family Medicine, University of Iceland,Solvangur, Hafnarfjordur (VAA, JAS), and the Departmentof Clinical Microbiology, Landspitali University Hospital (KGK)and Directorate of Public Health (SG), Reykjavik, Iceland.Key words: Acute otitis media, antimicrobial use, drug prescription,tympanostomy tube, parental expectations, Iceland.Address for reprints: Vilhjálmur Ari Arason, M.D., Departmentof Family Medicine, Solvangur Health Centre, Solvangsvegur3, 220 Hafnarfjordur, Iceland. Fax (354) 55026 71; E-mailvaa@hgsolvangur.is.DOI: 10.1097/01.inf.0000040702.00373.951110Background. Widespread antimicrobial use is arisk factor for development of antimicrobial resistance.Antimicrobial treatment of acute otitismedia (AOM) may not always be necessary. Littleis known about the influence of parental expectationson physicians’ decision-making in relationto treatment of AOM. Evidence is insufficientas to whether tympanostomy tubeplacement reduces antibiotic consumption.Methods. We randomly selected 1030 children 1to 6 years old living in 4 geographic areas inIceland to be invited to participate in the study.Information about sociodemographic factors, antimicrobialprescriptions and their indicationsduring the preceding 12 months, tympanostomytube placements and parental views on antimicrobialuse and bacterial resistance were obtainedfrom a questionnaire completed by theparents and medical records.Results. The incidence of AOM episodes resultingin antimicrobial prescription for 804 childrenrecruited into the study was 0.7 (95% confidenceinterval, 0.6 to 0.8) per child per year, highestamong children age 1 year, i.e. 1.8 prescriptions(95% confidence interval, 1.4 to 2.2). The cumulativeincidence of tympanostomy tube placementswas 30%. Antimicrobial use during the preceding8 weeks for children with and without tubesdid not differ (P 0.36). Fifteen percent of childrenwith tubes had received antimicrobials duringthe preceding 8 weeks at last once for AOMcompared with 14% of those without tubes (P 0.97). Parents in the area where antimicrobialconsumption was lowest were less likely to acceptantimicrobial treatment than parents in theother areas (P 0.005). Parents of children whohad previously received antimicrobials for AOMwere more likely to accept antimicrobials (P 0.04).Conclusions. Parental expectations to antimicrobialtreatment and awareness about resistancedevelopment appear to influence treatmentstrategies for AOM. The high rate oftympanostomy tube placement in preschool childrendoes not result in reduced antimicrobialconsumption.INTRODUCTIONAntimicrobial overuse is one of the major causes forthe development of antimicrobial resistance amongcommon pathogens. 1 A strong association between theoverall antimicrobial use and carriage of penicillinresistantpneumococci has been documented in Icelandicchildren. 2 During the years 1993 to 1998 an Icelandicpublic information campaign accompanied bytargeted information to physicians resulted in a 30%reduction of the total antimicrobial prescriptions ratefor acute otitis media (AOM) in children. 3 A reducedprevalence of penicillin resistance among pneumococcifollowed in the wake of the campaign. 4AOM was the single most common (65%) diagnosisresulting in antimicrobial prescription for Icelandicchildren in 1993 2 which is in agreement with studiesfrom other countries. 5, 6 Previously we demonstratedan association between antimicrobial consumption andprevalence of penicillin-nonsusceptible pneumococci inrelation to AOM. 3 There are several randomized clinicaltrials 7, 8 and metaanalyses 9, 10 that indicate thatantimicrobial treatment of AOM may not always benecessary or that treatment may have only a limitedeffect. Despite successful efforts to reduce antibiotic

Vol. 21, No. 12, Dec. 2002 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL1111consumption in Iceland, there could be a potential forfurther reduction of antibiotic prescriptions for AOM.Physicians considering an antimicrobial prescriptionmay consider not only clinical symptoms and signs butalso social factors and parental expectations. 11–14 Theaim of this study was to investigate factors contributingto antibiotic prescriptions for AOM in preschoolchildren, including sociodemographic factors, parentalexpectations and awareness to resistance development,as well as the impact of former antimicrobial usage bythe index child. We also evaluated whether tympanostomytubes placement reduces antibiotic consumptionamong children.METHODSStudy population and design. Children in fourgeographic areas in Iceland were included in the study(Fig. 1). At the end of 1997 these areas had a totalpopulation of 27 013 inhabitants, of whom 2900 werechildren from 1 to 6 years old, according to the NationalRegistry. These areas were served by 17 general practitioners.The areas were: Hafnarfjordur (H), 18 203inhabitants, including 1989 children 1 to 6 years old;Vestmannaeyjar (V) with 4640 inhabitants, including512 children; Egilsstadir (E), with 3076 inhabitants,including 300 children; and Bolungarvik (B), with 1094inhabitants and 99 children. After computer randomizationof all 2900 eligible children, 1030 children (36%of the total) were selected, and their parents received aletter inviting them to participate in the study togetherwith their child (H, 20%; V, 58%; E, 63%; and B, 62%).Informed parental consent was obtained from all participants.Data were collected in April and May 1998. Parentsof participating children received postal questionnaires,addressing sociodemographic factors, numberof children in the household and day-care attendance.Antimicrobial use was measured as the number of oralantimicrobial courses during the preceding year. TheFIG. 1. The study areas in Iceland.date of the last antimicrobial prescription was noted,together with the type of agent prescribed and theclinical indication (diagnosis) for the prescription. Pastor present use of tympanostomy tubes was recorded.The information collected from parents was matchedwith information available from the medical records atthe local health center.Parents were also asked to complete a questionnaireabout their personal preferences in relation to antimicrobialtreatment in the case of (1) unspecified upperrespiratory infections (common cold) and (2) acuteotitis media. Parents answered the question whether itwas always, sometimes or never appropriate to giveantimicrobials in these two situations, or whether theydid not know. They were then asked to agree, disagreeor give no comment (or answer “do not know”) to thefollowing two statements: “Some pathogens are becomingresistant to antimicrobials” and “Inappropriateantimicrobial use can lead to antimicrobial resistanceproblems among common pathogens.”The study was approved by the National BioethicsCommittee and the National Data Protection Commission,Iceland.Statistical analysis. The Pearson chi square testwas used for univariate analysis of categorical variables.Multivariate logistic regression was used toestimate the odds if a child had been given treatmentby antimicrobials because of AOM or not, adjusted toage, gender, residence, having siblings or not andday-care attendance to control interdependence. Themultivariate logistic regression was also used to determinethe odds if a child had received tympanostomytubes or not, adjusted for residence and gender and forthe odds if a child had received antimicrobials duringthe preceding 8 weeks or not, adjusted for age, and ifthe child had tympanostomy tube inserted or not.Furthermore the logistic regression method was usedfor the odds that a parent would express the opinionthat it is never appropriate to give antimicrobial treatmentfor colds (unspecified upper respiratory tractinfection) rather than sometimes, adjusted for residence,the child having siblings or not, parental viewthat AOM should be treated with antimicrobials or notand whether a child had received antimicrobial treatmentfor otitis media during the last 12 months or not.Individual regression coefficients were tested with theWald statistic, and 95% confidence intervals (95% CI)were calculated for the odds. The statistical analyseswere performed with the SPSS program for Windows(Advanced Statistics Release 8.0; SPSS Inc, Chicago,Ill.). The level of statistical significance was taken as0.05.RESULTSEight hundred four children and their parents participatedin the study. The mother was the responder in

1112 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL Vol. 21, No. 12, Dec. 2002TABLE 1. Study populationArea Participants Boys GirlsMean Age ofParticipantsHafnarfjordur 331 (75)* 173 (52.3) 158 (47.7) 4.07 1.75†Vestmannaeyjar 244 (76) 131 (53.7) 113 (46.3) 4.20 1.67Egilsstadir 174 (88) 83 (47.7) 91 (52.3) 4.04 1.78Bolungarvik 55 (83) 28 (50.9) 27 (49.1) 4.23 1.72Total 804 (78) 415 (51.6) 389 (48.4) 4.11 1.73* Numbers in parentheses, percent enrolled of those invited.† Mean SD.92% of cases. This represented a response rate rangingfrom 75 to 88% of the total random sample of the studyareas (Table 1). A total of 439 (54.6%) had receivedantimicrobial treatment at least once during the preceding12 months. The total incidence of antibiotictreatments for any reason was 1.21 per child per year(95% CI 1.09 to 1.32). This number was significantlyhigher in area V, 1.51 (95% CI 1.26 to 1.75) than in areaE, 0.89 (95% CI 0.60 to 1.09). In area H the incidencewas 1.16 (95% CI 0.99 to 1.33), and in area B it was1.15 (95% CI 0.72 to 1.57).Antimicrobial prescriptions for acute otitismedia. The yearly incidence of disease episodes diagnosedas AOM and resulting in oral antimicrobialtreatment was 0.70 (95% CI 0.61 to 0.79) per child,constituting 58% of total antimicrobial prescriptionsfor any reason. The rate was highest, 1.79 (95% CI 1.40to 2.18) per child, among children 1 year of age andlowest among the 6-year-olds, i.e. 0.25 (95% CI 0.15 to0.36) per child. Analyzed by areas the incidence was: E,0.57 (95% CI 0.41 to 0.74); B, 0.65 (95% CI 0.32 to 0.99);H, 0.69 (95% CI 0.56 to 0.83); and V, 0.81 (95% CI 0.62to 1.00).The types of antimicrobial agent used in the mostrecent treatment for AOM were amoxicillin or ampicillinin 111 cases (50.7%), amoxicillin plus clavulanicacid in 56 cases (25.6%), trimethoprim-sulfamethoxazolein 35 cases (16.0%), penicillin in 11 cases (5,0%),erythromycin in 1 case (0.5%) and other classes (or notknown) in 5 cases (2.3%).The yearly incidence of clinical episodes other thanAOM resulting in antimicrobial prescriptions were:tonsillitis, 0.18 (95% CI 0.15 to 0.21); acute sinusitis,0.10 (95% CI 0.08 to 0.13); bronchitis, 0.07 (95% CI 0.05to 0.09); pneumonia, 0.07 (95% CI 0.05 to 0.09); skininfections, 0.05 (95% CI 0.04 to 0.07); and urinary tractinfections, 0.04 (95% CI 0.02 to 0.06).Sociodemographic risk factors for antimicrobialprescription for acute otitis media. Young age(1 to 3 years old) was significantly associated with moreantimicrobial prescriptions for AOM than in childrenages 4 to 6 years old (Table 2). Gender, number ofsiblings, residence and day-care attendance did notinfluence the odds of receiving antimicrobials for AOM.Use of tympanostomy tubes. Information abouttympanostomy tube usage was obtained for 735 children.Among these 213 or 29% (95% CI 26 to 33%) hadat some point received tympanostomy tube in one orboth ears. Twenty-three percent (95% CI 16 to 31%) of1-year-old children had already received tubes (Fig. 2).The percentage of children who had received tubes was26% in Areas E and H, 34% in Area B and 35% in AreaV (P 0.113). Adjusted for area of residence, the oddsfor boys to receive tympanostomy tubes (128 of 377)was 1.56 as compared with girls (88 of 358) (P 0.01).Of 88 children currently having tympanostomy tubes,31 (35%) had received oral antimicrobials at least onceduring the previous 8 weeks compared with 162 of 645children (25%) not having tympanostomy tubes (P 0.059). When adjusted also for age the odds if childreceived antimicrobials or not was not statisticallysignificant (P 0.36).Thirteen children with tympanostomy tubes (15%)had received oral antimicrobials for AOM during thepreceding 8 weeks (mean, 3.77 weeks; 95% CI 2.11 to5.43), compared with 90 children (14%) without tubes(mean, 3.76 weeks; 95% CI 3.24 to 4.27) (P 0.97).Parental expectations and awareness in relationto antimicrobial treatment. Parents in Area E,TABLE 2. Adjusted odds ratio for children who have beentreated with antimicrobials for acute otitis media in thepreceding 12 months (N 277) as opposed to not (N 519)by multivariate analysis (796 cases analyzed, data missingin 8 cases)VariableNo.OddsRatio95% CI P*Age1–3 yr 386 14–6 yr 410 0.24 0.17–0.33 0.0001GenderMale 409 1Female 387 1.25 0.92–1.71 0.156SiblingsNo 128 1Yes 668 1.04 0.69–1.58 0.844Residence 0.558Area H 327 1Area V 242 1.21 0.83–1.74 0.332Area E 172 0.89 0.59–1.35 0.581Area B 55 1.16 0.62–2.17 0.636Day careNo 145 1Yes 651 1.01 0.68–1.50 0.972* Overall significance: chi square, 88.8; df, 7; P 0.0001.

Vol. 21, No. 12, Dec. 2002 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL1113where antibiotic consumption was lowest, answeredsignificantly more often than parents in other areasthat it was never appropriate to give antimicrobialtreatment for unspecified upper respiratory tract infection(Table 3). The statement “some pathogenic bacteriaare becoming resistant to antimicrobials” was answeredby 798 parents, of whom 719 agreed (89.4%), 2(0.2%) disagreed, 33 (4.1%) were passive and 44 (5.5%)did not know. Similarly 797 parents gave their opinionon the statement “inappropriate antimicrobial use canlead to resistance development among common pathogens”and 644 (80.1%) agreed, 4 (0.5%) disagreed, 76(9.5%) were passive and 73 (9.1%) did not know. Theresponse from parents to the questionnaire addressingissues of parental expectations and awareness furtherindicated that parents who consider it inappropriate totreat unspecified upper respiratory tract infectionswith antimicrobials significantly more often preferredthat AOM not be treated with antibiotics (Table 4).They also more often considered it appropriate toprescribe antimicrobials for unspecific upper respiratorytract infection if their child had previously receivedantibiotics for AOM. Tympanostomy tube usagefor their child did not influence parental opinion inrelation to this matter.FIG. 2. Cumulative prevalence in percentage ( 95% CI) ofpreschool children in Iceland who have received tympanostomytube placements.DISCUSSIONAOM is the most common clinical diagnosis underlyingantimicrobial prescriptions for Icelandic preschoolchildren. Physician treatment strategies for thiscondition are likely to have a significant impact on thetotal antibiotic consumption in the community. Thestudy indicates that antimicrobial consumption in acommunity can be influenced by efforts that aim atincreasing parental interest and awareness in relationto antibiotic use. As has been shown in a recentstudy, 15 involving patients more actively in evaluatingthe need for antimicrobial treatment in situations inwhich convincing evidence for a clear benefit is lacking,may lead to reduced drug consumption.Parents of children who had previously been treatedfor AOM with antimicrobials were more likely to concurwith antimicrobial therapy, even for the commoncold. This may be caused by positive reinforcementgiven that the child might have improved from upperairway infections on a previous occasion while takingan antimicrobial agent. Similar findings have beenreported for treatment of sore throat. 16A major benefit of this study is the comparisonbetween geographically well-defined areas. The impactof day-care attendance is hard to evaluate on the basisof this study, given that 80% of 1- to 6-year-oldchildren in Iceland attend day care. Other studieshave, however, demonstrated that day care appears tohave a clear impact on the number of treatment courses.17There was a surprisingly high use of tympanostomytubes among the participating children. This number ismuch higher than in the south of Sweden where 10%of children had a history of tympanostomy tube insertions.18 Use appears to be even less in the UnitedStates where a recent study found that 1.8% of 1-yearoldchildren and 4.2% of 2-year-old children had tympanostomytube placement. 19 The explanation for theseTABLE 3. Results from parent’s questionnaire about appropriate antimicrobial usage for upper respiratory tract infectionsfor childrenQuestion 1*: Is It Appropriate to Give AntimicrobialTreatment for AOM?Question 2†: Is It Appropriate to Give AntimicrobialTreatment for Unspecified Upper Respiratory Tract Infection(Common Cold)?Always Sometimes Never Don’t know Always Sometimes Never Don’t knowArea H 27 (8.3)‡ 286 (87.5) 3 (0.9) 11 (3.4) 0 (0.0) 154 (47.2) 148 (45.4) 24 (7.4)Area V 28 (11.5) 197 (81.1) 4 (1.6) 14 (5.8) 1 (0.4) 121 (49.8) 95 (39.1) 26 (10.7)Area E 9 (5.2) 152 (87.9) 5 (2.9) 7 (4.0) 0 (0.0) 50 (28.9) 109 (63.0) 14 (8.1)Area B 2 (3.6) 51 (92.7) 1 (1.8) 1 (1.8) 0 (0.0) 21 (38.2) 25 (45.5) 9 (16.4)Total 66 (8.3) 686 (86.0) 13 (1.6) 33 (4.1) 1 (0.1) 346 (43.4) 377 (47.3) 73 (9.2)* Pearson chi square, 13.01; df 9; P 0.159.† Pearson chi square, 32.27; df 9; P 0.0001.‡ Numbers in parentheses, percent.

1114 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL Vol. 21, No. 12, Dec. 2002TABLE 4. Adjusted odds ratio for parental answers from the questionnaire; “Is it appropriate to give antimicrobial treatmentfor unspecified upper respiratory tract infection (cold), never as opposed to sometimesVariable No. Odds Ratio 95% CI P*Residence 0.005Area E 124 1Area H 277 0.50 0.32–0.78 0.002Area V 190 0.45 0.28–0.72 0.001Area B 39 0.68 0.32–1.43 0.302SiblingsNo 104 1Yes 526 1.10 0.72–1.71 0.652Day careNo 119 1Yes 511 1.08 0.71–1.63 0.728Want to treat acute otitis media with antibiotics?Always 58 1Sometimes 572 4.49 2.30–8.74 0.00001Antibiotic treatment for AOM last 12 mo?No 407 1Yes 223 0.70 0.50–0.98 0.040Tympanostomy tube now or before?No 442 1Yes 188 0.94 0.66–1.35 0.732* Chi square, 43.812; df 8; overall significance, P 0.00001.differences is not clear. Availability of physicians didnot appear to influence treatment strategies in general,including selection of children for tympanostomy tubeplacements. The numbers of ear, nose and throatphysicians and general practitioners in Iceland were7.3 and 56.7/100 000 inhabitants, respectively, which iscomparable with conditions in Sweden, where the correspondingfigures have been 6.6 and 59.1/100 000. 20The main indications for tympanostomy tube placementsare persistent fluid in the middle ear and recurrentAOM. This study focuses on causes of antimicrobialtreatment in children, especially the diagnosis ofAOM, with and without tympanostomy tubes. It didnot specifically address the criteria for insertion oftympanostomy tubes, but we assume that the indicationsare comparable with those in the US, Canada andScandinavia, given that all ear, nose and throat specialistsin Iceland and most of remitting general practitionershave completed their postgraduate trainingabroad, usually in the above-mentioned countries.Tympanostomy tube placement was not associatedwith reduced antimicrobial use for AOM in the presentstudy. This does not exclude the possibility that asubgroup of infection-prone children with chronic middleear effusion might benefit from the placement oftympanostomy tubes.ACKNOWLEDGMENTSWe thank the children and parents who participated in thestudy and the general practitioners who assisted in recruiting theparticipants. This study was supported by the Icelandic College ofFamily Physicians and The Research Fund of the University ofIceland, Reykjavik.REFERENCES1. Levy SB. Multidrug resistance: a sign of the times. N EnglJ Med 1998;338:1376–8.2. Arason VA, Kristinsson KG, Sigurdsson JA, Stefansdottir G,Mölstad S, Gudmundsson S. Do antimicrobials increase thecarriage rate of penicillin resistant pneumococci in children?Cross sectional prevalence study. BMJ 1996;313:387–91.3. Arason VA, Gunnlaugsson A, Sigurdsson JA, ErlendsdottirH, Gudmundsson S, Kristinsson KG. Clonal spread of resistantpneumococci despite diminished antimicrobial use. MicrobDrug Resist 2002;8:187–92.4. Kristinsson KG. Modification of prescribers’ behavior: theIcelandic approach. Clin Microbiol Infect 1999;5(Suppl 4):43–7.5. McCaig LF, Hughes JM. Trends in antimicrobial drug prescribingamong office-based physicians in the United States.JAMA 1995;273:214–9.6. Froom J, Culpepper L, Jacobs M, et al. Antimicrobials foracute otitis media? A review from the International PrimaryCare Network. BMJ 1997;315:98–102.7. Little P, Gould C, Williamson I, Moore M, Warner G, DunleaveyJ. Pragmatic randomised controlled trial of two prescribingstrategies for childhood acute otitis media. BMJ2001;322:336–42.8. Damoiseaux R, Van Balen F, Hoes A, Verheij T, De Melker R.Primary care based randomised double blind trial of amoxicillinversus placebo for acute otitis media in children agedunder 2 years. BMJ 2000;320:350–4.9. Rosenfeld RM, Vertrees JE, Carr J et al. Clinical efficacy ofantimicrobial drugs for acute otitis media: metaanalysis of5400 children from thirty-three randomized trials. J Pediatr1994;124:355–67.10. Del Mar C, Glasziou P, Hayem M. Are antibiotics indicated asinitial treatment for children with acute otitis media? Ametaanalysis. BMJ 1997;314:1526–9.11. Howie JG. Some non-bacteriological determinants and implicationsof antibiotic use in upper respiratory tract illness.Scand J Infect Dis 1983;39(Suppl):68–72.12. Macfarlane J, Holmes W, Macfarlane R, Britten N. Influenceof patients’ expectations on antibiotics management of acutelower respiratory illness in general practice: questionnairestudy. BMJ 1997;315:1211–14.13. Butler C, Rollnick S, Pill R, Maggs-Rapport F, Stott N.Understanding the culture of prescribing: qualitative study ofgeneral practitioners’ and patients’ perceptions of antibioticsfor sore throat. BMJ 1998;317:637–42.14. Hamm RM, Hicks RJ, Bemben DA. Antibiotics and respiratoryinfections: are patients more satisfied when expectationsare met? J Fam Pract 1996;43:56–62.15. Macfarlane J, Holmes W, Gard P, Thornhill D, Macfarlane R,Hubbard R. Reducing antibiotic use for acute bronchitis inprimary care: blinded, randomised controlled trial of patientinformation leaflet. BMJ 2002;324:91–4.

Vol. 21, No. 12, Dec. 2002 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL111516. Little PS, Gould C, Williamson I, Warner G, Gantley M,Kinmonth AL. Reattendance and complications in a randomisedtrial of prescribing strategies for sore throat: the medicalisingeffect of prescribing antibiotics. BMJ 1997;315:350–2.17. Uhari M, Mäntysaarik K, Niemelä M. A meta-analyticalreview of the risk factors for acute otitis media. Clin InfectDis 1996;22:1079–83.18. Melander E, Mölstad S, Persson K, Hansson HB, SöderströmM, Ekdahl K. Previous antibiotics consumption and otherrisk factors for carriage of penicillin-resistant Streptococcuspneumoniae in children. Eur J Clin Microbiol Infect Dis1998;17:834–8.19. Paradise JL, Rockette HE, Colborn DK et al. Otitis media in2253 Pittsburgh-area infants: prevalence and risk factorsduring the first two years of life. Pediatrics 1997;99:318–33.20. Medical Association in the Nordic countries 1999. Availableat: http://www.slf.se. Accessed October 22, 2002.Pediatr Infect Dis J, 2002;21:1115–23 Vol. 21, No. 12Copyright © 2002 by Lippincott Williams & Wilkins, Inc.Printed in U.S.A.Population-based surveillance for hospitalizedand ambulatory pediatric invasivepneumococcal disease in Santiago, ChileROSANNA LAGOS, MD, ALMA MUÑOZ, MD, MARÍA TERESA VALENZUELA, MD, INGRID HEITMANN, MD ANDMYRON M. LEVINE, MD, DTPHBackground. Nine- and 11-valent pneumococcalconjugate vaccines under development maycontrol pediatric pneumococcal disease in nonindustrializedcountries. Because these vaccinesare expensive, population-based surveillance ofpneumococcal disease in children

117PAPER IV

Scandinavian Journal of Primary Health Care, 2005; 23: 184/191ORIGINAL ARTICLEOtitis media, tympanostomy tube placement, and use of antibioticsCross-sectional community study repeated after five yearsVILHJALMUR A. ARASON 1 , JOHANN A. SIGURDSSON 1 , KARL G. KRISTINSSON 2 ,LINN GETZ 1 & SIGURDUR GUDMUNDSSON 31 Department of Family Medicine, University of Iceland, Solvangur, Hafnarfjordur, 2 Department of Clinical Microbiology,Landspitali University Hospital, Reykjavik, 3 Directorate of Public Health, Reykjavik, IcelandAbstractObjective. To investigate potential links between antimicrobial drug use for acute otitis media (AOM) and tympanostomytube placements, and the relationship between parental views and physician antimicrobial prescribing habits. Design. Crosssectionalcommunity study repeated after five years. Subjects. Representative samples of children aged 1/6 years in four welldefinedcommunities in Iceland, examined in 2003 (n/889) and 1998 (n/804). Main outcome measures. Prevalence ofantimicrobial treatments for AOM, tympanostomy tube placements, and parental expectations of antimicrobialtreatment. Results. Tympanostomy tubes had been placed at some time in 34% of children in 2003, as compared with30% in 1998. A statistically significant association was found between tympanostomy tube placement rate and antimicrobialuse for AOM in 2003. In the area where antimicrobial use for AOM was lowest in 1998, drug use had further diminishedsignificantly. At the same time, the prevalence of tympanostomy tube placements had diminished from 26% to 17%. Tubeplacements had increased significantly, from 35% to 44%, in the area where antimicrobial use for AOM was highest. Parentsin the area where antimicrobial consumption was lowest and narrow spectrum antimicrobials were most often used were lesslikely to be in favour of antimicrobial treatment. Conclusions. Comparison between communities showed a positivecorrelation between antimicrobial use for AOM and tympanostomy tube placements. The study supports a restrictive policyin relation to prescriptions of antibiotics for AOM. It also indicates that well-informed parents predict a restrictiveprescription policy.Key Words: Acute otitis media, antimicrobial use, drug prescription, epidemiology, Iceland, intervention, parentalexpectations, tympanostomy tube placementAcute otitis media (AOM) is the single mostcommon diagnosis resulting in antimicrobial prescriptionfor children in the Western world [1/4],including Iceland. Nevertheless antimicrobial treatmentof AOM is debatable. Several randomizedclinical trials [5,6] and meta-analyses [7,8] indicatethat it may often be unnecessary, yet severe infectionssuch as acute mastoiditis can complicateAOM. Comparison of the incidence of mastoiditisin the USA where AOM has usually been treatedwith antimicrobials and the Netherlands whereAOM is usually not treated with antimicrobials,however, reveals a negligible difference [9]. Arestrictive antibiotic policy for AOM thereforeIn Iceland, 30% of pre-school children have hadtympanostomy tube placements for recurrent orchronic otitis media. It is unclear whether this isdue to high disease prevalence or medical overtreatment.. We found a positive correlation betweentympanostomy tube placements and rate ofantimicrobial drug prescription for acuteotitis media.. In regions with diminishing use of antimicrobials,a decrease in tympanostomy placementscould be observed over time.Correspondence: Vilhjalmur Ari Arason MD, Department of Family Medicine, Solvangur Health Center Solvangsvegur 3, IS-220 Hafnarfjordur, Iceland.E-mail: vaa@hgsolvangur.is(Received 30 December 2004; accepted 19 April 2005)ISSN 0281-3432 print/ISSN 1502-7724 online # 2005 Taylor & FrancisDOI: 10.1080/02813430510031298

Association between antibiotic usage for AOM and tympanostomy tube placement 185. Parental knowledge about appropriate use ofantimicrobial drugs was found to be relatedto physician prescribing habits.appears justifiable. Such a policy is further supportedby the documented link between high consumptionof antimicrobials and development ofantimicrobial resistance among common pathogens[1,10,11]. A strong association between antimicrobialuse for AOM and carriage of penicillin nonsusceptiblepneumococci in children has beendemonstrated [12]. Further knowledge about theshort- and long-term impact of different treatmentstrategies for otitis media is important.Tympanostomy tube placement is a well establishedtreatment option for chronic effusion in themiddle ear and recurrent episodes of AOM [13], yetthe consequences of this intervention are not clear[14/16]. The cumulative prevalence of tympanostomytube placement among Icelandic pre-schoolchildren has been shown to be 30% [2], which ismuch higher than reported in other countries [17].Furthermore, children with tympanostomy tubesreceived as many antimicrobial courses as childrenwithout tubes.The aim of the present study was to investigatepotential links between antimicrobial treatment forAOM and tympanostomy tube placements andevaluate the impact of sociodemographic factorsand parental views on physician prescribing habits.We approached these research questions by conductinga cross-sectional investigation in four welldefinedareas with a five-year interval.Material and methodsStudy population and designEligible participants included all children 1 to 6years of age living in the four Icelandic communitiesHafnarfjördur (H), Vestmannaeyjar (V), Egilsstadir(E), and Bolungarvik (B). All eligible children in V,E, and B were invited to participate, whilst a randomsample was invited in area H (Table I). The studyareas were served by a total of 19 general practitioners(GPs) (18.2 positions), of whom 11 were thesame individuals as in the 1998 study. The organizationalstructure of the healthcare service was similarfor both study periods, except in area H which is asuburb of Reykjavik. Emergency appointments weremore often provided by doctors outside area H in2003 than in 1998, resulting in somewhat decliningcontinuity of care in area H. The same ear, nose, andthroat specialists were responsible for bi-monthlyvisits to each of the areas V, E, and B during theyears 1998 and 2003. Inhabitants in area H had easyaccess to such specialists in Reykjavik. Informedparental consent was obtained for all participants.The parents received a questionnaire regardingsociodemographic factors, number of children andsmoking habits in the household, and day careattendance. Antimicrobial use was measured as thenumber of oral antimicrobial courses during thepreceding year, according to parents’ recollection.The date of the last antimicrobial prescription wasnoted, together with the type of agent prescribed andthe clinical indication (diagnosis) for the prescription.A history of past or present use of tympanostomytubes was recorded. Information gathered fromparents was matched with information from themedical records at the local health centre. Parentswere furthermore asked to complete a questionnaireabout their personal views in relation to antimicrobialtreatment, similar to the 1998 study [2]. Thestudy was approved by the National BioethicsCommittee and the National Data Protection Commission,Iceland.Statistical analysisThe statistical methods have been described in detailelsewhere [2]. Fisher’s exact test and the Pearsonchi-square test were used for univariate analysis ofcategorical variables. Linear regression analysis wasused to estimate correlation coefficient (r) and 95%confidence interval for the slope of mean number ofantimicrobial courses for AOM compared withtympanostomy tube placement rate by areas andmean number of total antimicrobial courses comparedwith the prevalence of parents finding itappropriate sometimes to treat common cold withantimicrobials. Multivariate logistic regression modelswere used to estimate odds ratio. Individualregression coefficients were tested with the Waldstatistic and 95% confidence intervals were calculatedfor the odds. The statistical analyses wereperformed with the SPSS † program for Windows(Advanced Statistics Release 8.0, SPSS Inc,Chicago, Ill.). The level of statistical significancewas taken as 0.05.ResultsParticipationIn total, 889 children participated (see Table I),representing a response rate from 76 to 84 percent.According to the questionnaires most of the childrenattended day care centres (84/94%). The child’smother provided the parental information in 90% ofcases.

186 V. A. Arason et al.Table I. Study population: characteristics of the populations in 2003 and 1998.Mean age of participants(years9/SD)ParticipationrateParticipantsNo.Children 1/6 yearsold invited No.Children 1 /6years old No.Total no. of inhabitants and no. of GPpositions within parenthesesArea YearH Hafnarfjordur 1998 18.203 (9.2) 1.989 442 331 75% 4.079/1.752003 20.675 (10.2) 2.004 380 287 76% 4.169/1.65V Vestmannaeyjar 1998 4.640 (4) 512 321 244 76% 4.209/1.672003 4.416 (4) 406 396 324 82% 4.379/1.57E Egilsstadir 1998 3.076 (3) 300 198 174 88% 4.049/1.782003 2.874 (3) 265 256 216 84% 4.209/1.71B Bolungarvik 1998 1.094 (1) 99 66 55 83% 4.239/1.722003 957 (1) 82 75 62 83% 3.899/1.64Total 1998 27.013 (17.2) 2.900 1.030 804 78% 4.119/1.732003 28.922 (18.2) 2.757 1.107 889 80% 4.229/1.64Prescription of antibioticsA total of 48% of the participating children hadreceived oral antimicrobial treatment at least onceduring the preceding 12 months, compared with55% in 1998 (p/0.007). The mean number ofantibiotic treatments per year was 1.06 (1.21 in1998, Table II). The usage was significantly higherin area V compared with the other areas on bothoccasions. The proportion of antimicrobial prescriptionsfor AOM was about the same (57%) as in 1998(58%). The number of treatment courses for theindication AOM was also highest in area V, i.e. 0.88courses per year per child (Table II). In area E,where the antimicrobial prescription rate was lowest(0.57) in 1998, it had decreased significantly to 0.27in 2003.The choice of antimicrobial drug also variedconsiderably by study areas. Broad-spectrum antimicrobials(amoxicillin/clavulanic acid, azitromyzin,erythromycin, trimethoprim-sulphamethoxazole), wereused in only 23 of 72 cases (32%) in area E wherethe total antimicrobial consumption was lowest butin 148 of 189 cases (78%) in the high-consumptionarea V (pB/0.0001).Predictors of prescriptions for antibiotics for otitis mediaAs shown in Table III, the child’s age, residence, andhistory of tympanostomy tubes (past or present)were independently associated with the number ofantimicrobial treatments for AOM. In our 1998study, this was the case only for age. Smoking didnot influence the odds if the child received antimicrobialsfor AOM or not.Predictors of tympanostomy tube placementsInformation about tympanostomy tube usage wasobtained for 880 children. A total of 298 (34%)reported tympanostomy tube insertions in one orboth ears at some time point (cumulative prevalence),and among these, as many as 22% (95% CI14/31%) of one-year-old children. Boys, as in 1998,had received tympanostomy tubes significantly moreoften (178/467) than girls (120/413) (p/0.018).The percentage of children who had received tubesvaried significantly from 17% in area E to 44% inarea V in 2003 (see Table II, pB/0.0001).From 1998 to 2003, there had been a significantincrease in tympanostomy tube placements in areasV and H (where antimicrobial prescription rates werehighest), and a decrease in areas E and B (notsignificant in area B) (see Table II). In area E, aconcurrent and significant decrease took place intympanostomy tube placements among children andantimicrobial prescriptions (total use as well as for

Association between antibiotic usage for AOM and tympanostomy tube placement 187Table II. Total number of antimicrobial treatment courses during the 12 months prior to enrolment, number of treatment courses forAOM, and number (%) of children 1/6 years of age having had tympanostomy tube placement.AreaYearNo. of treatment coursesper child per year(95% CI)No. of treatment courses forAOM per child per year(95%CI)No. (%) of children havinghad tympanostomy tubeplacementp-value* for changes intympanostomy tubeplacement rate between1998 and 2003H 1998 1.16 (0.99/1.33) 0.69 (0.56/0.83) 81/310 (26.1)2003 1.05 (0.86/1.23) 0.57 (0.43/0.71) 103/280 (36.8) 0.006V 1998 1.51 (1.26/1.75) 0.81 (0.62/1.00) 79/227 (34.8)2003 1.48 (1.27/1.69) 0.88 (0.71/1.04) 143/324 (44.1) 0.034E 1998 0.89 (0.60/1.09) 0.57 (0.41/0.74) 39/148 (26.4)2003 0.53 (0.41/0.65) 0.27 (0.19/0.36) 37/215 (17.2) 0.049B 1998 1.15 (0.72/1.57) 0.65 (0.32/0.99) 17/50 (34.0)2003 0.72 (0.46/0.98) 0.41 (0.20/0.62) 15/61 (24.6) 0.299Total 1998 1.21 (1.09/1.32) 0.70 (0.61/0.79) 216/735 (29.4)2003 1.06 (0.95/1.16) 0.60 (0.52/0.68) 298/880 (33.9) 0.060Corresponding figures from the 1998 study are included.the indication AOM specifically). According tomultivariate analysis, adjusted for age, a child havingtympanostomy tube(s) was more likely to have hadrecurrent antimicrobial treatment and to live inthe area where antimicrobials were most frequentlyused (area V, Table IV). Day care attendance wasalso a predictor of having tubes. A significantcorrelation was found at the community levelTable III. Mean number of antimicrobial treatment courses per year for AOM and adjusted odds ratios (OR) for children treated withantimicrobials for AOM in the preceding 12 months (n/270), as opposed to not (n/593).VariableMean number of treatment coursesper year for AOM (95%CI) OR 95% CI p-valueAge1/3 yrs 1.06 (0.90/1.21) 14/6 yrs 0.23 (0.18/0.28) 0.18 0.12/0.25 0.0001Gendermale 0.61 (0.50/0.72) 1female 0.59 (0.47/0.70) 1.01 0.73/1.40 0.99SiblingsNo 0.82 (0.57/1.08) 1Yes 0.55 (0.47/0.63) 0.79 0.52/1.20 0.25ResidenceArea V 0.88 (0.71/1.04) 1Area E 0.27 (0.19/0.36) 0.32 0.20/0.51 0.0001Area B 0.41 (0.20/0.62) 0.44 0.22/0.88 0.019Area H 0.57 (0.43/0.71) 0.50 0.34/0.74 0.0003Day careNo 0.89 (0.58/1.20) 1Yes 0.57 (0.49/0.66) 0.86 0.50/1.47 0.56Tympanostomytube, now or beforeYes 0.94 (0.75/1.13) 1No 0.43 (0.36/0.50) 0.49 0.35/0.70 0.0001Smoking in the houseNo 0.59 (0.50/0.68) 1Yes 0.64 (0.45/0.82) 0.92 0.61/1.41 0.69Multivariate analysis (863 cases analysed, data missing for 26 cases). Overall significance: chi-square/165,79, df/10, p/0.0000.

188 V. A. Arason et al.between tympanostomy tube placement rate andantimicrobial use for AOM (r/0.97, p/0.032)(Figure 1).Effects of tympanostomy tubes on recent antimicrobialdrug consumptionOf 123 children having tubes, 49 (40%) had receivedoral antimicrobials at least once during the previous8 weeks, as compared with 124 of 737 children(17%) without tubes (pB/0.001). Considering onlyantimicrobial treatment for AMO, 25 children(20%) in the tympanostomy group had recentlyreceived antimicrobials, compared with 74 children(10%) among those without tubes (pB/0.001).Adjusting for age, the odds ratio for receivingantimicrobials was significantly higher for childrenwith tubes (pB/0.001). In 1998, this difference wasnot statistically significant.Parental views on antimicrobial drug treatmentTable V gives the results of the questionnairesregarding appropriate antimicrobial usage for upperrespiratory infections in children. Data from 1998are provided for comparison. At the communitylevel, a significant correlation was found between thechildren’s total antimicrobial use and the rate ofparents considering it sometimes appropriate to treatcommon cold with antimicrobials (r/0.99, p/0.01).DiscussionFour communities in Iceland have been studied withan interval of five years with regard to use ofantimicrobial drugs, prevalence of tympanostomytube placements, and prevalence of penicillin nonsusceptiblepneumococci, in particular to see howthese factors interact with each other. Our earlierstudies have highlighted the risk of recent antimicrobialusage on carriage of penicillin non-susceptiblepneumococci [1,12] as well as an unusuallyhigh prevalence of tympanostomy tube placementsin Iceland [2]. In the present paper we observed notonly an association between antimicrobial prescriptionrates for AOM and prevalence of tympanostomytube placements at the community level, but alsochanges with time between 1998 and 2003 inrelation to antimicrobial usage. In the area whereantimicrobial consumption was lowest in 1998,antimicrobial use for AOM as well as tympanostomytube placements decreased significantly. In the twoareas where antimicrobial use was highest in 1998,antimicrobial use remained high, and the tympanostomytube placement rate increased significantly.Changes in the delivery of acute healthcare servicesin area H from 1998 to 2003 weakened the quality ofthe local data where a higher antimicrobial prescriptionrate could be expected.There was a significant association between thenumber of antimicrobial prescriptions for AOM inchildren and tympanostomy tube placements on theTable IV. Odds ratio (OR) adjusted for age for children having tympanostomy tubes (n/123), as opposed to not (n/736).Variable No. OR 95%CI p-valueResidenceArea V 314 1Area E 214 0.35 0.17/0.64 0.0021Area B 61 1.02 0.46/2.24 0.97Area H 270 0.81 0.50/1.30 0.38Number of antimicrobial treatments for AOM, last 12 months0 594 11/2 203 1.96 1.22/3.17 0.0059]/3 62 4.98 2.60/9.53 0.0001GenderFemale 407 1Male 452 1.28 0.84/1.94 0.25Smoking in the family house settingNo 701 1Yes 158 1.01 0.60/1.72 0.95Day careNo 71 1Yes 788 2.38 1.07/5.28 0.0317Multivariate analysis (859 cases analysed, data missing in 30 cases). Overall significance: chi-square/100.176, df/9, p/0.0000.

Association between antibiotic usage for AOM and tympanostomy tube placement 189% received tympanostomy tubes6055504540Area V3530Area H252015Area EArea Br = 0.97p = 0.032100.290.33 0.37 0.41 0.45 0.49 0.53 0.57 0.61 0.66 0.70 0.74 0.78 0.82 0.86Number of antimicrobial courses for AOM per child per yearFigure 1. Correlation between tympanostomy tube placement rate (cumulative prevalence) and antimicrobial use for acute otitis media (last12 months) among 1- to 6-year-old children in Iceland, 2003.level of both the individual and the community. Thisphenomenon may have different underlying explanations.One possibility is that frequent use ofantimicrobial drugs might change the bacterial florain the community, by promoting the emergence ofresistant bacteria [1,12]. This could in turn increasethe risk of treatment-resistant episodes of bacterialinfections including AMO [18], chronic effusion inthe middle ear, and subsequent tympanostomy tubeplacement. A second possibility may be due to thefact that otorrhea is a common problem in childrenwith tympanostomy tubes [19]. This may lead toprescriptions of antibiotics due to suspicion or fear ofAOM and may at least partly explain why childrenwith tubes in the present study had more oftenreceived recent oral antimicrobial treatment.On the other hand, the observed difference ofpractice may have a complex set of explanations.Table V. Results from parents’ questionnaires regarding appropriate antimicrobial usage for upper respiratory tract infections for children,number and percentage (%), compared with results from the 1998 study.Question/area Year Always Sometimes Never Don’t knowQuestion 1 1Is it appropiate to give antimicrobial treatment for acute otitis media?Area H 1998 27 (8.3) 286 (87.5) 3 (0.9) 11 (3.4)2003 30 (10.7) 231 (82.5) 3 (1.1) 16 (5.7)Area V 1998 28 (11.5) 197 (81.1) 4 (1.6) 14 (5.8)2003 33 (10.2) 274 (85.1) 1 (0.3) 14 (4.3)Area E 1998 9 (5.2) 152 (87.9) 5 (2.9) 7 (4.0)2003 11 (5.1) 194 (90.7) 1 (0.5) 8 (3.7)Area B 1998 2 (3.6) 51 (92.7) 1 (1.8) 1 (1.8)2003 1 (1.6) 58 (95.1) 1 (1.6) 1 (1.6)Total 1998 66 (8.3) 686 (86.0) 13 (1.6) 33 (4.1)2003 75 (8.6) 757 (86.3) 6 (0.7) 39 (4.4)Question 2 2Is it appropriate to give antimicrobial treatment for unspecified upper respiratory tract infection (common cold)?Area H 1998 0 (0.0) 154 (47.2) 148 (45.4) 24 (7.4)2003 0 (0) 122 (44.0) 137 (49.5) 18 (6.5)Area V 1998 1 (0.4) 121 (49.8) 95 (39.1) 26 (10.7)2003 0 (0) 186 (57.9) 114 (35.5) 21 (6.5)Area E 1998 0 (0.0) 50 (28.9) 109 (63.0) 14 (8.1)2003 0 (0) 64 (30.2) 131 (61.8) 17 (8.0)Area B 1998 0 (0.0) 21 (38.2) 25 (45.5) 9 (16.4)2003 0 (0) 20 (32.8) 38 (62.3) 3 (5.1)Total 1998 1 (0.1) 346 (43.4) 377 (47.3) 73 (9.2)2003 0 (0) 392 (45.0) 420 (48.2) 59 (6.8)1 1998, Pearson chi-square 13.01, df 9, p/0.159; 2003, Pearson chi-square 15.05, df 9, p/0.090. 2 1998, Pearson chi-square 32.27, df 9,p/0.0001; 2003, Pearson chi-square 46.65, df 9, p/0.0001.

190 V. A. Arason et al.The incidence of respiratory tract infections mayvary between areas. There may also be a tendency tounder-diagnose AOM in some areas and overdiagnoseAOM in others. Furthermore, the variousareas may have different treatment traditions/culturesin relation to the clinical problem in question.A recent study by Gabbay and Le May addressed thephenomenon of varying clinical ‘‘mindlines’’ amongprimary health care practices in the UK [20].Parents in areas where antimicrobial drug usagewas lowest and broad-spectrum antimicrobialsmost rarely prescribed appeared to be better informedabout the benefits of restrictive use ofantimicrobial drugs for upper respiratory tractinfections. These variations in parental attitudemay be important as primary care physicians maintainthat parental pressure and expectations inrelation to antimicrobial drug prescriptions representan important barrier to a restrictive prescribingpractice [2,21/27].Our results demonstrate an association betweenthe use of antibiotics, parental views about antimicrobialtreatment, and use of tympanostomy tubeplacements. However, it is impossible to say whetherthe associations between antimicrobial use for AOMand tympanostomy tube placements are due todirect causal effects or because of differences inmedical practice. The possibility of a direct positivecorrelation between antimicrobial drug (over) usefor AOM, future episodes of AOM, and tympanostomytube placement later warrants further investigation.AcknowledgementsThe authors would like to thank all the children andparents who participated in the study and the generalpractitioners who assisted in the study areas. Thisstudy was supported by the Icelandic College ofFamily Physicians and the Research Fund of theUniversity of Iceland, Reykjavik.References[1] Arason VA, Kristinsson KG, Sigurdsson JA, GudmundssonS, Stefansdottir G, Mölstad S. Do antimicrobials increasethe carriage rate of penicillin resistant pneumococci inchildren? Cross sectional prevalence study. BMJ 1996;/313:/387/91.[2] Arason VA, Sigurdsson JA, Kristinssson KG, GudmundssonS. Tympanostomy tube placements, sociodemographicfactors and parental expectations for management ofacute otitis media in Iceland. Pediatr Infect Dis J 2002;/21:/1110/5.[3] McCaig LF, Hughes JM. Trends in antimicrobial drugprescribing among office-based physicians in the UnitedStates. JAMA 1995;/273:/214/9.[4] Froom J, Culpepper L, Jacobs M, De Melker RA, Green LA,van Buchem L, et al. Antimicrobials for acute otitis media? Areview from the International Primary Care Network. 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Association between antibiotic usage for AOM and tympanostomy tube placement 191[21] Garbutt J, Jeffe DB, Shackelford P. Diagnosis and treatmentof acute otitis media: an assessment. Pediatrics 2003;/112:/143/9.[22] Melander E, Bjorgell A, Bjorgell P, Ovhed I, Mölstad S.Medical audit changes physicians’ prescribing of antibioticsfor respiratory tract infections. Scand J Prim Health Care1999;/17:/180/4.[23] Munck A, Gahrn-Hansen B, Soegaard P, Soegaard J. Longlastingimprovement in general practitioners’ prescribing ofantibiotics by means of medical audit. Scand J Prim HealthCare 1999;/17:/185/90.[24] Macfarlane J, Holmes W, Gard P, Thornhill D,Macfarlane R, Hubbard R. Reducing antibiotic use foracute bronchitis in primary care: blinded, randomisedcontrolled trial of patient information leaflet. BMJ 2002;/324: /91/4.[25] Siegel RM, Kiely M, Bien JP, Joseph EC, Davis JB, MendelSG, et al. Treatment of otitis media with observation and asafety-net antibiotic prescription. Pediatrics 2003;/112:/527/31.[26] Jonsson H, Haraldsson RH. Parents’ perspectives on otitismedia and antibiotics. A qualitative study. Scand J PrimHealth Care 2002;/20:/35 /9.[27] Petursson P. GPs’ reasons for ‘‘non-pharmacological’’ prescribingof antibiotics / a phenomenological study. Scand JPrim Health Care 2005;23:120/5.

127PAPER V

MICROBIAL DRUG RESISTANCEVolume 12, Number 3, 2006© Mary Ann Liebert, Inc.The Role of Antimicrobial Use in the Epidemiology ofResistant Pneumococci: A 10-Year Follow UpVILHJALMUR A. ARASON, 1 JOHANN A. SIGURDSSON, 1 HELGA ERLENDSDOTTIR, 2SIGURDUR GUDMUNDSSON, 3 and KARL G. KRISTINSSON 2,4ABSTRACTThe relative effects of risk factors on the prevalence of resistant pneumococcal clones are hard to determine.Our aim was to evaluate the effect of risk factors on the prevalence of resistant pneumococci in Iceland in2003 and compare these data with results of identical studies performed in 1993 and 1998. A randomized sampleof 1,107 children was chosen from all 2,532 children 1 to 6 years old living in four communities. Pneumococciwere carried by 64% of the 824 children enrolled and 9.5% were penicillin nonsusceptible (PNSP),as opposed to 8.1% (1998) and 8.5% (1993), and multiresistant strains of serotype 6B were 2.5% comparedto 7.5% and 7.7% (p 0.001). Antimicrobial use had declined in 10 years from 1.5 to 1.0 courses/child peryear. The only significant risk factor for carriage of PNSP and erythromycin-resistant pneumococci was antimicrobialconsumption. The multiresistant type 6B strains disappeared from the areas with the lowest antimicrobialuse but maintained unchanged prevalence in the area with the highest use. The number of erythromycin-resistant,penicillin-susceptible strains of all pneumococci (37/475, 7.8%) increased significantlyfrom the previous studies (7/353, 2.0%, 1998, and 2/390, 0.5%, 1993). This observation is associated with increaseduse of macrolides, especially azithromycin, in one of the study areas. Spread of novel resistant clonesappears to be the main reason for rapid and significant changes in pneumococcal resistance rates. The choiceof antimicrobial class appears to influence the selective environment favoring particular resistant clones.INTRODUCTIONCOMPARATIVE AND ANALYTICAL STUDIES have demonstrateda relationship between high antimicrobial consumptionand increasing antimicrobial drug resistance in pneumococci.1,2,12,13,18 However, the effects of reduced antimicrobialconsumption and herd immunity on the prevalence of resistancehave been harder to document. 2 This requires long-term longitudinalepidemiological studies of risk factors for carriage ofresistant pneumococci and prevalence of resistant clones. 10There is an increasing need to analyze available data to constructmathematical models that can be used as tools to predictthe likely outcomes of various antibiotic policy options. 3,15 Theincidence of penicillin-nonsusceptible pneumococci (PNSP) increasedrapidly in Iceland from 1989 7 until 1993, when it hadreached 20% in pneumococcal infections. 8 Most of the PNSPbelonged to a single multiresistant clone of serotype 6B (theSpanish-Icelandic clone, Spain-2 6B ). 19 An unstructured nationwidecampaign to reduce antimicrobial use followed. The campaignwas led by key opinion leaders and involved all of themass media together with meetings with health professionals.Subsequently, the overall antimicrobial use for children reducedby about one third. 2,9Our studies to evaluate risk factors for PNSP carriage in 1993and 1998 demonstrated the importance of antimicrobial use,clonal spread, and herd immunity. 1,2 The relative importanceof antimicrobial use compared to clonal spread and herd immunityon PNSP carriage is not known.This is the third cross-sectional study of risk factors andPNSP carriage in the same communities, giving three snapshotsover a 10-year period. Our aim is to analyze the relative effectsof various risk factors, clonal spread, and herd immunity.1 Department of Family Medicine, University of Iceland, Solvangur, Hafnarfjordur, Iceland.2 Department of Clinical Microbiology, Landspitali University Hospital, Reykjavik, Iceland.3 Directorate of Public Health, Reykjavik, Iceland.4 Faculty of Medicine, University of Iceland, Reykjavik, Iceland.169

170MATERIALS AND METHODSStudy population and designFour geographical areas that had been studied in comparativestudies in 1993 and 1998 were reexamined in 2003 by comparablemethods. 1,2 At the end of 2002 (December 1, 2002)these areas had a total population of 28,922, including 2,757children from 1 to 6 years old, i.e., Hafnarfjordur (H), 20,675inhabitants, 2,004 children 1–6 years old. Corresponding figuresfor the other areas were Vestmannaeyjar (V), 4,416, 406,Egilsstadir (E), 2,874, 265, and Bolungavik (B), 957, 82. AreaH is a town adjacent to the capital Reykjavik, area V is a fishingtown on an island of the south coast, area E is a town surroundedby a large farming area, and area B is a fishing townon the northwest coast. The population density and living standardsare similar in all the study towns. All eligible children,according to the Icelandic National Registry, were invited toparticipate in V (396), E (256), and B (75), whereas a randomsample of 380 children was invited to participate in area H.Eighteen general practitioners, of whom 11 were the same asin the 1998 study, served these areas.The sites were visited in April and May, 2003. After informedparental consent, a nasopharyngeal specimen was takenfrom each child. The parents answered a postal questionnaireregarding the use of antimicrobials by their child: number ofantimicrobial courses in the preceding year; the date and typeof the last antimicrobial agent used; type of infection andwhether the child had been taking prophylactic antibiotics 3weeks during the preceding year. They were also asked aboutthe presence of tympanostomy tubes (TT) (presently and in thepast) and if someone smoked in the same household. Informationon antibiotic and tympanostomy use was also collectedfrom the medical records at the local health center. Childrenthat had received antimicrobial treatment in the preceding 2weeks were excluded, as in the previous studies.The National Bioethics Committee and the National DataProtection Commission approved the study.MicrobiologyNasopharyngeal samples were obtained with rayon-tippedswabs (Mini-tip Culturette ® , Becton Dickinson and Co., MD),stored for a maximum of 24 hr before they were inoculated onblood agar (Difco, Detroit, MI) containing gentamicin (5 mg/L)and incubated anaerobically. Typical colonies were identifiedwith conventional methods, and pneumococci were screenedfor penicillin resistance by the oxacillin disc diffusion test. 20 Ifcolonial appearance suggested the presence of more than onepneumococcal strain, each of the colonies was tested separately.The MIC of nonsusceptible isolates was determined by the E-test (AB Biodisk, Solna, Sweden) according to the manufacturer’srecommendations. Isolates having a penicillin MIC of0.094 mg/L were defined as nonsusceptible. Susceptibility toerythromycin, tetracycline, chloramphenicol, clindamycin, andtrimethoprim-sulfamethoxazole was determined by disc diffusiontests according to the Clinical and Laboratory StandardsInstitute (CLSI) methods and criteria. 4 Penicillin nonsusceptibleisolates were also serotyped by co-agglutination 11 using antiserafrom the State Seruminstitute (Copenhagen, Denmark).Statistical analysisARASON ET AL.Carriage of penicillin-nonsusceptible as opposed to -susceptiblepneumococci or erythromycin-resistant as opposed to erythromycin-susceptiblepneumococci were the single outcomevariables. Each case could only be associated with a singlestrains, so where there was carriage of a typeable PNSP strainwith a nontypeable (nonencapsulated) strain, the nontypeablestrain was excluded from the analysis because it is much lesslikely to be associated with infections. Similarly, we excludedpenicillin-susceptible strains in dual carriage with PNSP strains.Analysis of possible association with the outcome variable was:TABLE 1.ANTIMICROBIAL (AM) USAGE IN NUMBER OF COURSES PER YEAR, CARRIAGE OF PNEUMOCOCCI AND PNSP AND THENUMBER OF DIFFERENT PNSP STRAINS IN THE STUDY GROUPSAM coursesType of PNSPNumber of per year Number of Number ofNon-Area Year Children (95% CI) PNC a (%) PNSP (%) 6B (%6B) 9V 14 19F 23 typeableH 1993 527 1.5 (1.4–1.7) 280 53.1 24 8.6 21 7.5 1 21998 301 1.0 (0.8–1.1) 174 57.8 11 6.3 9 5.2 1 12003 258 1.0 (0.8–1.1) 154 59.7 20 13.0 4 2.6 10 2 4V 1993 100 1.7 (1.2–2.1) 55 55.0 10 18.2 10 18.21998 224 1.4 (1.1–1.6) 122 54.5 5 4.1 5 4.12003 301 1.4 (1.2–1.6) 214 71.1 15 7.0 9 4.2 6E 1993 111 1.3 (1.0–1.6) 52 46.8 1 1.9 1 1.91998 167 0.9 (0.7–1.1) 69 41.3 13 18.8 13 18.82003 207 0.5 (0.4–0.6) 120 60.0 12 10.0 0 0 5 7B 1993 53 1.5 (1.0–2.0) 39 73.6 1 2.6 1 2.61998 51 1.0 (0.6–1.4) 19 37.3 2 10.5 2 10.52003 58 0.7 (0.4–1.0) 37 63.8 3 8.1 0 0 1 2Total 1993 791 1.5 (1.4–1.6) 426 53.9 36 8.5 33 7.7 1 21998 743 1.1 (0.0–1.2) 384 51.7 31 8.1 29 7.5 1 12003 824 1.0 (0.9–1.1) 525 63.7 50 9.5 13 2.5 11 5 2 0 19a PNC, Pneumococcal carriers.

EPIDEMIOLOGY OF RESISTANT PNEUMOCOCCI 171sex, age, area of residence, siblings, day-care attendance, typeof the last antimicrobial agent used, weeks from last antimicrobialtreatment, number of courses in the preceding 12months, use of prophylactic antibiotics, use of tympanostomytubes at the time of sampling or before, and tobacco smokingin the same household. The Pearson chi-square tests were usedfor univariate analysis of categorical variables and one-wayanalysis of variance (ANOVA) for continuous variables.As in the earlier studies of 1993 and 1998, the multivariatelogistic regression method was used to estimate the risk for allknown variables of carrying PNSP to control interdependence.Individual regression coefficients were tested with the Wald statistic,and confidence intervals calculated for the odds. The multivariateanalyses were performed with the SPSS ® program forWindows (Advanced Statistics Release 8.0, SPSS Inc, Chicago,IL). The level of statistical significance was 0.05. Confidenceintervals are given as 95% confidence intervals.Nasopharyngeal carriageRESULTSOverall carriage: Of the 1,107 children invited, 848 (77%)participated (H, 74%; V, 78%; E, 82%, and B 79%). Twentyfour were excluded from nasopharyngeal culturing because theyhad received antimicrobials in the 2 preceding weeks. Thus,824 children were studied. The mean age for the whole groupwas 4.3 years (SD 1.7) (H, 4.2; V, 4.4; E, 4.2, and B, 3.9).A total of 525 carried pneumococci (63.7%) and average carriagerate in the communities varied from 59.7% to 71.1%(Table 1).Carriage of PNSP: The proportion of PNSP was 9.5%, butonly 5.9% if nontypeable strains are excluded (Table 1). Multiresistantserotype 6B strains (n 13) (phenotypically identicalto the Spanish-Icelandic clone) were only found in twoareas (Table 1). Fifty four children carried at least two pneumococcalstrains. In two instances, children carried two PNSPstrains where one was nontypeable and therefore excluded fromstatistical analyses and Table 1. Similarly, we excluded 9 penicillin-susceptiblestrains in dual carriage with PNSP nontypeablestrains and 12 penicillin-susceptible strains in dual carriagewith PNSP typeable strains. Thirty-one children carried two ormore penicillin-susceptible pneumococci. Two children carriedonly penicillin-susceptible nontypeable pneumococci. All of thePNSP were resistant to trimethoprim-sulfamethoxazole and alltype 6B, type 19F, and nontypeable strains were multiresistant.All except the serotype 6B strains were susceptible to chloramphenicol.The serotype 9V and 14 strains were susceptibleto erythromycin, tetracycline, and clindamycin but the nontypeableand serotype 6B strains were not. The penicillin MICswere as follows: serotype 6B, nine strains 0.25 mg/L, three 0.38mg/L, and one 0.75 mg/L; serotype 9V, one 0.125 mg/L, two0.25 mg/L, four 0.38 mg/L, and four 0.5 mg/L; serotype 14,three 0.5 mg/L, one 0.75 mg/L, and one 1.0 mg/L; serotype19F, one 0.25 mg/L and one 0.5 mg/L; nontypeable (nonencapsulated)strains, five 0.094, one 0.19 mg/L, eight 0.25 mg/L,three 0.38 mg/L, and one 0.5 mg/L. There was a marked differencein the PNSP rates between the study areas (7.0–13.0%,Table 1), which had decreased from 1998 in two areas but increasedin the other two. The number of serotype 6B strainshad decreased in all areas except area V and the rate of typeablePNSP had also decreased in all areas (Fig. 1). Nontypeable(nonencapsulated) PNSP strains had not been observed in thetwo previous studies.Carriage of erythromycin-resistant pneumococci: The numberof erythromycin-resistant and penicillin-susceptible strainsincreased significantly from the previous study in 1998 in areasH and V (p 0.0004 and p 0.0001, respectively), but decreasedin the other two areas (E and B, p 0.05 and p 0.6,respectively) (see Table 2). However, the proportion of erythromycinresistance among PNSP remained similar.Antimicrobial use: The mean number of antimicrobialcourses per child in the study population was 1.0 during theyear preceding the sampling (CI 0.9–1.1; 33.3% reduction from1993 and 9.1% from 1998, Table 1 and Fig. 1). Forty six percentof the children (n 379) had received antimicrobials atleast once during the preceding year, compared to 65% in 1993and 40% in 1998. The consumption was lowest in area E andhighest in area V. As previously, acute otitis media was theTABLE 2.ERYTHROMYCIN SUSCEPTIBILITY OF PENICILLIN-SUSCEPTIBLE AND NONSUSCEPTIBLE PNEUMOCOCCI, IN 1993,1998, AND 2003, IN THE RESPECTIVE AREAS (NUMBER OFERYTHROMYCIN-RESISTANT PNEUMOCOCCI)NumberArea Year Number of ERY a %H PSP b 1993 256 0 01998 163 1 0.62003 134 13 9.7PNSP 1993 24 20 83.31998 11 7 63.62003 20 10 50.0V PSP 1993 45 2 4.41998 117 0 02003 199 21 10.6PNSP 1993 10 9 90.01998 5 5 1002003 15 14 93.3E PSP 1993 51 0 01998 56 4 7.12003 108 1 0.9PNSP 1993 1 1 1001998 13 13 1002003 12 8 66.7B PSP 1993 38 0 01998 17 2 11.82003 34 2 5.9PNSP 1993 1 1 1001998 2 2 1002003 3 2 66.7Total PSP 1993 390 2 0.51998 353 7 22003 475 37 7.8PNSP 1993 36 31 86.11998 31 27 87.12003 50 34 68.0a ERY, Erythromycin.b PSP, Penicillin-susceptible pneumococci.

172FIG. 1. The proportion of PNSP (typeable and nontypeable,typeable strains only, and serotype 6B only), and antimicrobialuse in the years 1993, 1998, and 2003.most common reason for antimicrobial prescriptions (56%). Antimicrobialuse by age was 1.82 courses per one year old childper year (CI 1.36–2.28), 1.94 (1.56–2.33) for 2 years old, 1.17(0.96–1.38) for 3 years old, 0.76 (0.58–0.94) for 4 years old,0.46 (0.32–0.61) for 5-year-old, and 0.35 (0.23–0.48) for 6-year-old children. The choice of antimicrobial class differedmarkedly between areas. Amoxicillin was the most commonlyprescribed antimicrobial agent overall 29% (37% in 1998 and20.8% in 1993), and in all areas except area V (E, 43%; B,32%; H, 39%, and V, 17%). The penicillins (amoxicillin, amoxicillin clavulanic acid, and phenoxmethylpenicillin) accountedfor 62% overall (B, 82%; H, 75%; E, 77%; and V,46%). Other antimicrobials accounted for less than 15% in allareas except area V. The main antimicrobial used in area V wasazithromycin (33.3%), which was rarely used in the other areas(E 1.5%, B 13.6%, and H 9.7%).Factors associated with carriage of PNSPAntimicrobial use: Antimicrobial use was the most significantrisk factor for carrying PNSP by univariate analysis (Table 3).Children carrying PNSP had received on average 1.78antimicrobial courses during the preceding 12 months (CI1.24–2.32) compared to 0.95 courses (CI 0.82–1.09) for childrencarrying penicillin-susceptible pneumococci (Table 3) and 0.93(CI 0.75–1.10) for no carriage. The PNSP carriage rate was 26.7%(16/60) 2–7 weeks after antimicrobial treatment compared to 7.3%(34/465) 8 weeks after treatment (p 0.001). On the other hand,the overall pneumococcal carriage was similar for children thathad received antimicrobial treatment 2–7 weeks before samplingtime (60/104, 58%) as opposed to 8 weeks before sampling time(465/720, 64%)(p 0.1906). There was no significant differencein the recorded risk factors between children carrying typeablePNSP versus nontypeable PNSP (Table 4).ARASON ET AL.Age: The mean age for children carrying pneumococci waslower, 4.12 years (CI 3.98–4.26), than for children not carryingpneumococci, 4.49 years (CI 4.29–4.69), but not significantlylower for PNSP carriage. The PNSP carriage rate was highestfor 2-year-children, 18% (16/89); 8.3% for 1 year, 9% for 3years, 7.4% for 4 years, 6.1% for 5 years, and 8.3% for 6-yearoldchildren. The carriage of specific serotypes/groups of PNSPwas not related to particular age groups, except that carriers ofnontypeable pneumococci were significantly older than carriersof serotype 14 (mean age 4.08 years (95% CI 3.22–5.00) as opposedto 2.82 (2.57–3.08). The mean age was 3.95 years(2.70–5.19) for type 6B and 3.41 (2.50–4.31) for type 9V.Tympanostomy tubes: Information on tympanostomy tubeuse was available for 817 children; thereof 279 (34%) childreneither currently had tubes or had had tubes before. Informationon current use was available for 782, and of these as many as111 (14.2%) had tympanostomy tubes at the time of sampling.Presence of tympanostomy tubes was neither associated withcarriage of pneumococci nor PNSP (Table 3).Smoking: Pneumococcal carriage was slightly higher in childrenfrom smoking households as opposed to nonsmokinghouseholds, but the difference was not significant (100/522 forcarriers vs. 48/297 for others, p 0.30). There was no associationbetween smoking in the household settings and PNSP carriage(Table 3).Other factors: Children attending day care were more likelyto carry pneumococci 489/752 than children not attending daycare 35/70 (p 0.0138), but pneumococcal carriage was neitherassociated with gender nor to number of siblings.Factors that were not found to be significantly associatedwith PNSP carriage (Table 3) were gender, number of siblings,and day-care attendance.Multivariate analysis: To control for confounding factors, allsignificant variables from the univariate analysis were used ina multivariate backward stepwise logistic regression model(number of children in analysis 506, 2 10.412, df 1,p 0.013). The number of antimicrobial treatments was theonly independent risk factor for carriage of PNSP, odds ratio1.28 for each treatment (95% CI 1.11–1.48), p 0.007. Figure2 shows the odds ratio by using a similar multivariate logisticmodel for different variables in the 1993, 1998, and 2003 studies,where the number of weeks from last antimicrobial coursesis used in the models instead of the number of antimicrobialcourses in the preceding 12 months. The time duration of 2–7weeks from last antimicrobial treatment compared to 8 weekswas the only significant risk factor for PNSP carriage in all thethree analyses.Factors associated with carriage of erythromycin-resistantpneumococci: All of the variables tested for association withcarriage of PNSP were also tested for association with carriageof erythromycin-resistant pneumococci with multivariate backwardstepwise logistic regression model (number of children inanalysis 524, 2 5.35, df 1, p 0.027). As for PNSPcarriage, the number of antimicrobial treatments was the onlyindependent risk factor for carriage of erythromycin-resistantpneumococci, odds ratio 1.18 for each treatment (95% CI1.03–1.35), p 0.0157. The association of using a particularantimicrobial class was compared with using any other class orno antibiotic. By testing the risk of using a particular antimicrobialclass versus not having used an antimicrobial agent, the

EPIDEMIOLOGY OF RESISTANT PNEUMOCOCCI 173TABLE 3.UNIVARIATE ANALYSIS ON DIFFERENT VARIABLES FOR CHILDREN CARRYING PNSP COMPARED TO CHILDRENCARRYING PENICILLIN-SUSCEPTIBLE PNEUMOCOCCIPenicillin-NumbersusceptibleVariable children pneumococci PNSP p valueResidence Area H 258 134 20 0.280Area V 301 199 15Area E 207 108 12Area B 58 34 3Age Mean 4.16 Mean 3.78(95% CI 4.01–4.30) (95% CI 3.03–4.25)Sex Male 430 249 29 0.462Female 394 226 21Number of Mean 1.40 Mean 1.63siblings (95% CI 1.30–1.50) (95% CI 1.31–1.95)Day-care Yes 752 443 46attendance No 70 31 4 0.764Smoking in the Yes 148 94 6household No 671 378 44 0.255Tympanostomy Yes 279 169 20tubes at No 689 391 37 0.175sampling timeNumber of Mean 0.95 Mean 1.78 0.001antimicrobial (95% CI 0.82–1.09) (95% CI 1.24–2.32)(AM) courseslast 12 monthsNumber of weeks Mean 21.50 Mean 10.82 0.001from last AM (95% CI 19.46–23.53) (95% CI 7.58–14.06)treatmentProphylactic Yes 12 2AM last 12 No 460 48 0.635monthsType of last AM Amoxicillin 105 52 (25.9%) 12 (34.3%) 0.938Amox.-clav.acid 87 49 (24.4%) 13 (37.1%) 0.144Fenox.m.pc. 32 15 (7.5%) 1 (2.9%) 0.478Trimethophrim- 23 14 (7.0%) 1 (2.9%) 0.705sulphaErythromycin 20 13 (6.5%) 0Azithromycin 71 41 (20.4%) 6 (17.1%) 0.820Cefuroxime 6 5 (2.5%) 0Cefalexin 9 5 (2.5%) 1 (2.9%) 1.000Dicloxacillin 8 7 (3.5%) 1 (2.9%) 1.000use of macrolides and amoxicillin clavulanic acid was associatedwith carriage of erythromycin-resistant pneumococci(p 0.081 and p 0.043, respectively), but not the otherclasses.DISCUSSIONObserving the rates of PNSP together with antimicrobial useat three occasions over a 10-year period in four communitiesin different parts of Iceland gives important clues regarding theepidemiology of PNSP. Antimicrobial use was highest at thefirst study in 1993 (1.5 AM courses/child per year) and hadcome down by a third at the last study in 2003. At the sametime, there was little overall change in the rates of PNSP (8.5,8.1, and 9.5% respectively), yet by excluding nontypeable pneumococcithe PNSP rate has also come down by almost a third(8.5, 8.1, and 5.9% respectively). The association between therates of antimicrobial use and resistance is not surprising, andin that sense these studies do little but confirm previous studies.However, the design of our studies allows us to look at thechanges within individual communities at different times.There are much greater changes taking place within the individualcommunities, changes that may be difficult to explainby antimicrobial use alone. In 1998, there was marked increasein PNSP rates in the two communities, which had had the lowestPNSP rates in 1993, despite significant decrease in antimicrobialuse. The increase was only due to an increase in multiresistantserotype 6B strains (representative phenotypicallyidentical strains have previously been shown to belong to theSpanish Icelandic clone, i.e., Spain 6B -2) 16,19 and was explainedby clonal spread into “virgin” communities. 2 The current studydoes indeed support that explanation, as that serotype (clone)has now disappeared from these two communities, probably due

174ARASON ET AL.TABLE 4.ASSOCIATION OF POTENTIAL RISK FACTORS WITH CARRIAGE OF TYPEABLE AND NONTYPEABLE(NONENCAPSULATED) PNSPTypeableNontypeableVariable PNSP PNSP p valueAge Mean 3.18 Mean 3.77(95% CI 2.64–3.72) (95% CI 2.63–4.90)Gender Male 18 11 1.000Female 13 8Number of siblings Mean 1.18 Mean 2.08(95% CI 0.86–1.51) (95% CI 1.13–3.04)Daycare attendance Yes 29 17 0.629No 2 2Smoking in the household Yes 3 3 0.661No 28 16Tympanostomy tubes Yes 13 7 0.774anytime No 18 12Tympanostomy tube at Yes 7 3 0.727sampling time No 23 14Prophylactic antimicrobial Yes 2 0(AM) last 12 months No 29 19Number of AM courses last Mean 2.36 Mean 2.3312 months (95% CI 1.66–3.07) (95% CI 1.71–2.96)Number of weeks from last Mean 11.64 Mean 9.33AM treatment (95% CI 7.00–16.27) (95% CI 5.00–13.66)to increased herd immunity to that particular clone and reducedantimicrobial use. The five yearly data are demonstrated in Fig.3A and the proposed prevalence of the Spanish-Icelandic clonewith time in the different areas in Fig. 3B. Therefore, it is reasonableto state that clonal spread in specific geographical areascan have more profound effects on the rates of PNSP thanantimicrobial use. Such changes may be more difficult to detectin large populations, yet similar changes took place withStreptococcus pyogenes clones in Finland. 6 We can also statethat the time period from the onset to the end of the epidemicwave for a particular clone is less than 10 years. In addition, itis likely that the extent of antimicrobial use will determine boththe peak prevalence and the subsequent endemic prevalence.Pneumococcal vaccination has not been recommended for chil-FIG. 2. Odds ratio for carrying PNSP as opposed to susceptible pneumococci, according to multivariate logistic regressionanalysis for the 1993, 1998, and 2003 studies. TT, Tympanostomy tubes.

EPIDEMIOLOGY OF RESISTANT PNEUMOCOCCI 175FIG. 3. The proportion of multiresistant serotype 6B strains (phenotypically identical to the Spanish-Icelandic clone) in the differentareas in 1993, 1998, and 2003 (A), and the postulated epidemic curves for the Spanish-Icelandic clone in the four studyareas (B).dren in Iceland, unless they belong to specific risk groups. Veryfew children have been vaccinated with the new conjugate vaccines,and therefore vaccinations should not play a role in thechanging epidemiology.The Spanish Icelandic clone appears to have disappearedfrom two of the communities (B and E), continued to declinein one (H), but surprisingly remained stable in one community(V). This cannot be explained by lack of herd immunity, becausethe clone has been present in that area at least since 1993.The continued high antimicrobial use in the area could perhapsexplain why the clone is still present in 2003 and it is temptingto conclude that rapidly increasing use of azithromycin (onethird of all prescriptions in 2003, and much higher than in theother areas) has established a favorable selective environmentfor this macrolide-resistant clone. This environment may alsohave led to the marked increase in the number of erythromycinresistantand penicillin-susceptible pneumococci in that area.In fact, the long half-life and low serum concentrations ofazithromycin have been associated with increased resistancerates. 5The nontypeable pneumococci all had a rough appearanceand are probably nonencapsulated, although this has not beenconfirmed with molecular investigations. Such rough (nonencapsulated)strains had not been observed in the previous twostudies. It is unlikely that such rough strains were missed in theprevious studies because all the agar plates from the 1998 and2003 studies were read by the same senior biomedical laboratoryscientist, and their appearance in 2003 could indicate theintroduction of novel clone(s). In a recent study of pneumococcicolonizing children attending day-care centers in Lisbon,Portugal, 7.4% were nontypeable, but after retesting and PCRof the lytA and psaA genes the true nontypeable rate was 5.9%.This rate had increased from 3.8% in 1997 to 11% in 1999 andthe strains were genetically diverse, although a dominant cloneaccounted for about half the strains. Most of the strains (86%)were resistant to antibiotics. 17 Another recent study of 121 nontypeablestrains from Finland, also showed genetic diversity,yet the majority belonged to a single lineage with defective capsularlocus. Comparison with the multilocus sequence typingdatabase showed that strains of that lineage have spread intercontinentally.14 The significance of penicillin nonsusceptibilityin the nontypeable pneumococci is not clear. Although suchstrains have lost their main virulence determinant, they may stillbe important as reservoirs of resistance genes.Although the three studies only give three snapshots of theresistance situation, we have reliable information about the antimicrobialuse in the study areas in the years preceding thesnapshots and could sample at least 74% of the children in thestudy areas, giving very representative snapshots. Adding furtherstrength to the studies was having the same investigatorstake all of the nasopharyngeal samples in all areas for all of thestudies, and the same biomedical laboratory scientists inoculatingand reading most of the agar plates.In conclusion, for small communities, the spread of resistantclones appears to be the main reason for rapid and significantchanges in pneumococcal resistance rates. Recent antimicrobialuse is the most consistent and important risk factor for carriageof resistant pneumococci and the choice of antimicrobial class

176may influence the selective environment favoring particular resistantclones.ACKNOWLEDGMENTSWe extend special thanks to all of the children who participatedin the study, their parents, the general practitioners who assistedin the study areas, and to the staff of the Department ofClinical Microbiology, Landspitali University Hospital. Thisstudy was supported by the Icelandic College of Family Physicians,The Research Fund of the University of Iceland, and theResearch Fund of the Landspitali University Hospital, Reykjavik.REFERENCES1. Arason, V.A., K.G. Kristinsson, J.A. Sigurdsson, G. Stefansdottir,S. Molstad, and S. Gudmundsson. 1996. Do antimicrobialsincrease the carriage rate of penicillin resistant pneumococciin children? Cross sectional prevalence study. Br. Med. J.313:387–391.2. Arason, V.A., A. Gunnlaugsson, J.A. Sigurdsson, H. Erlendsdottir,S. Gudmundsson, and K.G. Kristinsson. 2002. Clonalspread of resistant pneumococci despite diminished antimicrobialuse. Microb. Drug. Resist. 8:187–192.3. Austin, D.J., K.G. Kristinsson, and R.M. Anderson. 1999.Therelationship between the volume of antimicrobial consumption inhuman communities and the frequency of resistance. Proc. Natl.Acad. Sci. USA. 96:1152–1156.4. Clinical and Laboratory Standards Institute. 2006. PerformanceStandards for antimicrobial susceptibility testing. CLSI documentM100-S16 [ISBN 1-56238-588-7]. Clinical and Laboratory StandardsInstitute, PA 19087-1898 USA.5. Kastner, U., and J.P. Guggenbichler. 2001. Influence ofmacrolide antibiotics on promotion of resistance in the oral floraof children. Infection 29:251–256.6. Kataja, J., P. Huovinen, A. Muotiala, J. Vuopio-Varkila, A. Efstratiou,G. Hallas, and H. Seppala. 1998. Clonal spread of groupA streptococcus with the new type of erythromycin resistance.Finnish Study Group for Antimicrobial Resistance. J Infect. Dis.3:786–789.7. Kristinsson, K.G., M.A. Hjalmarsdottir, and O. Steingrimsson.1992. Increasing penicillin resistance in pneumococci in Iceland.Lancet 339:1606–1607.8. Kristinsson, K.G. 1995. Epidemiology of penicillin resistant pneumococciin Iceland. Microb. Drug Resist. 1:121–125.9. Kristinsson, K.G. 1999. Modification of prescribers’ behavior: theIcelandic approach. Clin. Microbiol. Infect. 5 (suppl. 4):43–47.10. Kristinsson, K.G. 2000. Effect of antimicrobial use and other riskfactors on antimicrobial resistance in pneumococci. In A.TomaszARASON ET AL.(ed.), Streptococcus pneumoniae. Molecular biology and mechanismsof disease. Mary Ann Liebert Inc., New York, pp. 419–425.11. Kronvall, G. 1973. A rapid slide-agglutination method for typingpneumococci by means of a specific antibody adsorbed to protein-A-containing staphylococci. J. Med. Microbiol. 6:187–190.12. Melander, E., K. Ekdahl, G. Jonsson, and S. Molstad. 2000.Frequency of penicillin-resistant pneumococci in children is correlatedto community utilization of antibiotics. Pediatr. Infect. Dis.19:1172–1177.13. Melander, E., S. Molstad, K. Persson, H.B. Hansson, M. Soderstrom,and K. Ekdahl. 1998. Previous antibiotics consumptionand other risk factors for carriage of penicillin-resistant Streptococcuspneumoniae in children. Eur. J. Clin. Microbiol. Infect. Dis.17:834–838.14. Hanage, W.P., T. Kaijalainen, A. Saukkoriipi, J.L. Rickcord,and B.G. Spratt. 2006. A successful, diverse disease-associatedlineage of nontypeable pneumococci that has lost the capsularbiosynthesis locus. J. Clin. Microbiol. 44:743–749.15. Huovinen, P. 2005. Mathematical model-tell us the future! J. Antimicrob.Chemother. 56:257–258.16. Sa-Leao, R., S.E. Vilhelmsson, H. de Lencastre, K.G. Kristinsson,and A . Tomasz. 2002. Diversity of penicillin-nonsusceptibleStreptococcus pneumoniae circulating in Iceland after the introductionof penicillin-resistant clone Spain(6B)-2. J. Infect. Dis.186:966–975.17. Sa-Leao, R., A.S. Simoes, S. Nunes, N.G. Sousa, N. Frazao, andH. de Lencastre. 2006. Identification, prevalence and populationstructure of non-typeable Streptococcus pneumoniae in carriagesamples isolated from preschoolers attending day-care centres. Microbiology152:367–376.18. Seppala, H., T. Klaukka, J. Vuopio-Varkila, A. Muotiala, H.Helenius, K. Lager, and P. Huovinen. 1997. The effect of changesin the consumption of macrolide antibiotics on erythromycin resistancein group A streptococci in Finland. N. Engl. J. Med.337:441–446.19. Soares, S., K.G. Kristinsson, J.M. Musser, and A. Tomasz.1993. Evidence for the introduction of a multiresistant clone ofserotype 6B Streptococcus pneumoniae from Spain to Iceland inthe late 1980s. J. Infect. Dis. 168:158–163.20. Swenson, J.M., B.C. Hill, and C. Thornsberry. 1986. Screeningpneumococci for penicillin resistance. J. Clin. Microbiol.24:749–752.Address reprint requests to:Dr. Karl G. KristinssonDepartment of Clinical MicrobiologyLandspitali University Hospitalv/Baronstig101 Reykjavik, IcelandE-mail: karl@landspitali.is

APPENDIX137Informed parental consent and questionnaire 2003.Upplýsingar um rannsóknina:Sýklalyfjanotkun og ónæmar bakteríur í nefkoki barnaÁbyrgðamaður: Vilhjálmur Ari Arason, heimilislæknir, HeilsugæslustöðinniSólvangi, Hafnarfirði (Sími: 550 26 70, GSM: 8959156 ).(Aðrir umsjónarmenn og samstarfsaðilar: Prófessor Jóhann Ágúst Sigurðsson, Heimilislæknisfræði, LæknadeildHáskóla Íslands, Dr. Sigurður Guðmundsson, landlæknir og prófessor Karl G.Kristinsson, sýklafræðingur,Landsspítala-Háskólasjúkrahús. Rannsóknin er gerð í samvinnu við lækna heilsugæslustöðvarinnar).Tilgangur og ávinningur rannsóknarinnar: Tíðni baktería sem eruónæmar fyrir sýklalyfjum fer vaxandi, einkum svonefndra pneumókokkaí nefkoki barna. Margar rannsóknir (meðal annars þær semgerðar voru í Vestmannaeyjum, Egilsstöðum, Bolungarvík og í Hafnarfirðiá árunum 1993 og 1998), sýna tengsl milli þessarar þróunarog mikillar notkunar á sýklalyfjum. Tilgangur rannsóknar nú er aðendurtaka fyrri rannsóknir hér á landi 5 árum eftir síðustu rannsókn.Ræktaðar verða bakteríur úr nefkoki barna á aldrinum 1-6 ára með þvíað taka strok úr nefi með bómullarpinna, fengnar upplýsingar um sýkingarog notkun sýklalyfja, samkvæmt spurningablaði og samkvæmtupplýsingum úr sjúkraskrá heilsugæslustöðvarinnar. Markmiðið ersem fyrr að skoða árangur fyrri úrlausna og finna aðferðir til þess aðminnka ört vaxandi tíðni ónæmra bakteríustofna gegn sýklalyfjum.Þátttaka barns felst í því að:1) Foreldri fyllir út í spurningalista þar sem spurt er m.a um sýklalyfjanotkunbarnsins, (verður einnig athugað í sjúkraskrá), notkunröra í hljóðhimnur og viðhorf foreldis til sýklalyfjanotkunar.2) Stroksýni verður tekið úr nefi barnsins með bómullarpinna semer barninu að skaðlausu og án teljandi óþæginda (e.t.v smá kláði ínefi á eftir og hnerri).Sýnatakan er framkvæmd í leikskólunum eða skólanum af rannsóknaraðilum(ef foreldri er búið að samþykkja þátttöku skriflega) eða áHeilsugæslustöðinni ef foreldri óskar eftir.

138Stroksýnið er sent til Sýkladeildar Landspítala-Háskólasjúkrahússog eingöngu notað til ræktunar á bakteríum og athugun á hugsanleguónæmi þeirra gegn sýklalyfjum.Viðkomandi heilsugæslulæknar fá sent bréf ef barn greinist meðpenicíllin ónæman pneumókokk (foreldrar geta fengið upplýsingarhjá þeim ef um er að ræða spurningu um meðhöndlun á efri loftvegasýkingummeð sýklalyfjum).Persónuupplýsingum sem ekki tilheyra sjúkraskrá barnsins verðureytt að lokinni úrvinnslu innan 2ja ára frá sýnatökunni.Fyllsta trúnaðar verður gætt hvað varðar allar upplýsingar semaflað verður. Farið verður með persónuupplýsingar og skráningu þeirraí samræmi við lög um persónuvernd nr. 77/2000. Rannsókninhefur jafnframt hlotið leyfi Vísindasiðanefndar og Persónuverndar.Úrvinnsla gagna er í höndum umsjónarmanna og fer eingöngu framinnanlands. Niðurstöður rannsókna verða eingöngu birtar fyrir hópaog ekki persónugreinanlegar. Tekið skal fram að rannsóknin beinistekki að erfðaefnum eða ættartengslum.Forráðarmönnum er hvenær sem er heimilt að afturkalla samþykkitil þátttöku í rannsókninni. Gögnum um barnið sem tilheyra þessarirannsókn verður þá eytt. Hætti barn þátttöku mun það ekki í neinutilviki skerða þá heilbrigðisþjónustu sem barninu stendur annars tilboða í heilsugæslunni.Ef þú hefur spurningar um rétt þinn sem þátttakandi í vísindarannsókneða vilt hætta þátttöku í rannsókninni getur þú snúið þértil Vísindasiðanefndar, Laugavegi 103, 105 Reykjavík. Sími: 551-7100, fax: 551-1444

Samþykki foreldris um þátttöku barnsins:139Kæru foreldrarErindi bréfsins er að leita eftir þátttöku barns yðar í rannsókn semfelst í því að taka nefstrok úr barninu, svara spurningalista ogskoðun sjúkraskrár samkvæmt nánari lýsingum á meðfylgjandiupplýsingablaði sem foreldri/forráðamaður heldur eftir fyrir sig.Rannsóknin er framkvæmd á leikskólum/skólum bæjarins og Heilsugæslustöðinni,á tímabilinu 31. mars - 9. apríl 2003.Foreldrar sem samþykkja þátttöku eru góðfúslega beðnir um aðstraðfesta það með undirskrift sinni hér að neðan og að svarameðfylgjandi spurningalista.Blaðinu með spurningalistanum má síðan skila til leikskóla/skólabarnsins eða á Heilsugæslustöðina ef barnið kemur til sýnatöku þar.nafn barns:_______________________ kt.___________________sími:______________nafn foreldris/forráðamanns:_________________________ kt. ______________Dagsetning samþykkis:______ / _______ 2003Fyrir hönd rannsóknarhóps,Vilhjálmur Ari Arason, læknirEf þú hefur spurningar um rétt þinn sem þátttakandi í vísindarannsókneða vilt hætta þátttöku í rannsókninni getur þú snúið þér tilVísindasiðanefndar, Laugavegi 103, 105 Reykjavík. Sími: 551-7100,fax: 551-1444.

140Spurningalisti(krossið við eða svarið spurningum eftir sem við á)Aldur foreldris/forráðamanns sem svarar spurningum ____ áraKarl ❏Kona ❏Svarið hvað ykkur finnst réttast:Á að meðhöndla eyrnabóglur með sýklalyfjum?AlltafStundumAldreiVeit ekki❏❏Á að meðhöndla kvef með sýklalyfjum?AlltafStundumAldreiVeit ekki❏❏❏Takið afstöðu til neðangreindra fullyrðinga:Sumir sýklar (bakteríur) eru að verða ónæmir fyrir sýklalyfjum.Sammála (já)HlutlausÓsammála (nei)Veit ekki❏❏❏❏Ofnotkun sýklalyfja getur leitt til þess að þau tapi virkni sinni.Sammála (já)HlutlausÓsammála (nei)Veit ekki❏❏❏

Er barnið í dagvistun/leikskóla/skóla: Já ❏Nei ❏141Nafn á leikskóla/skóla: __________________________________Fjöldi systkina á heimilinu? _______________Hve oft hefur barnið fengið sýklalyf sl 12 mán? _____________Ástæður og fjöldi sýklalyfjameðferða sl. 12 mán. (skrifið fjöldameðferða fyrir aftan sjúkdómsgreiningu eftir því sem við á):Hálsbólga ________ Skútabólga (kinnholubólga)________Eyrnabólga ________ Húðsýking ____________Berkjubólga ________ Þvagfærasýking ____________Lungnabólga ________ Aðrar ástæður ____________Barnið verið á samfeldri sýklalyfjameðferð (3 vikur eða lengursamfellt) sl. 12 mán.? já ❏ nei ❏Ef já, hvers vegna (við hverskonar sýkingu)? _________________Ef barn hefur fengið sýklalyfjameðferð á árinu, hvað eru margarvikur frá síðustu meðferð? __________ vikurEðaEr barnið á sýklalyfjameðferð nú, hvað hefur sýklalyfjameðferðþá staðið í marga daga? __________ dagarEf barn hefur fengið sýklalyf sl. 12 mán., hver var ástæða fyrirsíðustu sýklalyfjameðferð barnsins? _______________________og hvaða sýklalyf fékk barnið þá? _________________________

142Hafa kokkirtlar (nefkirtlarnir) verið fjarlægðir úr barninu?JáNeiVeit ekki❏❏Ef já, þá hver/hvar/hvenær_______________________________________________________________________________________Hafa hálseitlar/hálskirtlar (tonsillur) verið frjarlægðir?JáNeiVeit ekki❏❏Ef já, þá hver/hvar/hvenær_______________________________________________________________________________________Hversu oft að meðaltali fór barnið þitt í sund á aldrinuma) 0 – 1 árs?: ________ sinni á árib) 1 – 2 ára?: ________ sinni á áric) 2 – 3 ára?: ________ sinni á árid) 3 – 4 ára?: ________ sinni á árie) 4 – 5 ára?: ________ sinni á árif) 5 – 6 ára?: ________ sinni á árig) 6 – 7 ára?: ________ sinni á áriAldur við fyrstu sundferðir? _________ áraEr reykt á heimilinu?JáNei❏❏

Hefur barnið þitt einhven tíman haft rör í eyrum?JáNeiVeit ekki❏❏143Ef já, hversu gamalt var það þegar það fékk fyrst rör? ______ áraHefur barnið þitt rör í eyra núna?JáNeiVeit ekki❏Ef já við spurningu hvort barnið sé með eða hafi verið með rör vinsamlegasvarið eftirtöldum spurningum:Geturðu nefnt helstu ástæðurnar fyrir rörísetningu að þínu mati(Má merkja við fleiri en einn, gjarnan forgangsraða fyrstu 3 frá1-3)a) Var áður alltaf að fá eyrnabólgu ....................... ❏b) Var alltaf að fá sýklalyf..................................... ❏c) Var með vökva í eyrum..................................... ❏d) Heyrði illa ........................................................ ❏e) Svaf illa ............................................................ ❏f) Var alltaf með kvef og hor ................................ ❏g) Lækirinn taldið þetta ráðlegt ........................... ❏h) Vegna ráðlegginga frá vinum og kunningjum... ❏i) Aðrar ástæður:________________________________________Skánaði barninu eftir röraísetningu?JáNeiVeit ekki❏❏Ef já hvað skánaði?: _____________________________________

144Telurðu vera einhverjar sérstakar skýringar á því að barnið þittvar „eyrnabarn“ (t.d.)Í ættinni? Já ❏Rysjótt veðurfar? Já ❏Nei ❏Reykingar á heimilinu? Já ❏Nei ❏Nei ❏Annað: _________________________________Takk fyrir

Paper V. Arason et al. MDR 2006 ERRATUM PAGE 173145TABLE 3. UNIVARIATE ANALYSIS ON DIFFERENT VARIABLES FOR CHILDRENCARRYING PNSP COMPARED TO CHILDREN CARRYING PENICILLIN SUSCEPTIBLEPNEUMOCOCCI.VariableNumberchildrenPenicillinsusceptiblepneumococciPenicillinnon-susceptiblepneumococciP valueResidence Area H 258 134 20 0.280Area V 301 199 15Area E 207 108 12Area B 58 34 3Age Mean 4.16(95%CI 4.01-4.30)Mean 3.78(95%CI 3.03-4.25)SexMale 430 249 29 0.462Female 394 226 21Number ofsiblings.Mean1.40(95%CI 1.30-1.50)Mean 1.63(95%CI 1.31-1.95)Daycare Yes 752 443 46attendance No 70 31 4 0.764Smoking in the Yes 148 94 6household. No 671 378 44 0.255Tympanostomy Yes 279 169 20tubes any time. No 538 301 30 0.766Tympanostomy Yes 111 70 10tubes at No 689 391 37 0.175sampling time.Number ofantimicrobial(AM)courseslast 12 months.Mean 0.95(95%CI 0.82-1.09)Mean 1.78(95%CI 1.24-2.32)