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

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