Meningococcal disease in the Netherl<strong>an</strong>ds, 1958-1990Over the years, the proportion of NT strains varied irregularly from 22% to 56%, <strong>an</strong>dth<strong>at</strong> of NST strains varied from 12% to 26%.The most common combin<strong>at</strong>ions of serotypes <strong>an</strong>d subtypes among serogroup Bmeningococci were 2a:Pl.2, 2b:P1.2, 4:Pl.4, 4:P1.l5, 15:P1.l6, <strong>an</strong>d 15:P1.7,16 (Table5). Strain B:2b:Pl.2 was isol<strong>at</strong>ed once during 1958-1961; its prevalence increased to15% of all serogroup B isol<strong>at</strong>es during 1964-1965 <strong>an</strong>d to 57% in 1970. Since 1980 ithas almost disappeared (17 isol<strong>at</strong>es in 1980 [18%] <strong>an</strong>d 3 [1 %] in 1990). The phenotypeB:4:P1.4, which was not found before 1980, was encountered twice in 1980. Itbecame the most prevalent phenotype in 1990 (28% of all serogroup B isol<strong>at</strong>es <strong>an</strong>d21% of all isol<strong>at</strong>es). One isol<strong>at</strong>e of the "Norwegi<strong>an</strong>" epidemic strain B:15:Pl.7,16, wasfound in 1975 <strong>an</strong>d one in 1980. It increased in frequency during subsequent years to11% of all isol<strong>at</strong>es in 1986, but its frequency declined to 3% in 1990. B:4:P1.l5isol<strong>at</strong>es were found throughout the period of 1958-1990. Their frequency increasedmoder<strong>at</strong>ely during the mid-1980s but decreased after 1987.Serogroup C. The distribution of serotypes <strong>an</strong>d sub types of 543 serogroup Cmeningococci obtained in 1980 <strong>an</strong>d 1983 <strong>an</strong>d during 1985-1990 is shown in Table 6.In the early 1980s serotypes 2a <strong>an</strong>d 2b were scarcely represented, but their rel<strong>at</strong>ivefrequency increased to 48% <strong>an</strong>d 17%, respectively, of all serogroup C isol<strong>at</strong>es in1990. The prevalence of serotypes 1 <strong>an</strong>d 4 decreased from 15% <strong>an</strong>d 23% to 3% <strong>an</strong>d9%, respectively. Two isol<strong>at</strong>es were of a comhined serotype (4/14 <strong>an</strong>d 4/16). SubtypePl.2 was frequently linked to serotypes 2a <strong>an</strong>d 2b. Its frequency increased from 7% in1983 to 37% in 1990. Isol<strong>at</strong>es with subtypes Pl.4, Pl.7 <strong>an</strong>d Pl.10 were not foundbefore 1986. The prevalence of subtypes Pl.4 <strong>an</strong>d Pl.7 remained moder<strong>at</strong>e, but 10%of all serogroup C isol<strong>at</strong>es in 1990 were found to be of subtype Pl.I0. Isol<strong>at</strong>es ofsubtypes Pl.12 <strong>an</strong>d Pl.14 were recovered mai<strong>nl</strong>y in the early <strong>an</strong>d mid-1980s. Therel<strong>at</strong>ive frequency of serogroup C isol<strong>at</strong>es of other subtypes showed o<strong>nl</strong>y minorfluctu<strong>at</strong>ions. One isol<strong>at</strong>e was characterized by 3 subtypes (Pl.7,1,15). The proportionof NT isol<strong>at</strong>es varied from 21 % to 64%, <strong>an</strong>d th<strong>at</strong> of NST isol<strong>at</strong>es varied from 29% to43%.Apart from the combin<strong>at</strong>ions 2a:P1.2 (102 isol<strong>at</strong>es), 2a:NST (58), <strong>an</strong>d 4:Pl.1 (21),m<strong>an</strong>y different serosubtype combin<strong>at</strong>ions were found to characterize the 543 serogroupC isol<strong>at</strong>es. Strain C:2a:P1.2 was found o<strong>nl</strong>y once in 1980, but it became thesecond most frequently isol<strong>at</strong>ed strain in 1990 (6% of all isol<strong>at</strong>es, 28% of all serogroupC isol<strong>at</strong>es).Serosubtype in rel<strong>at</strong>ion to ET among scrogroup B meningococci, isol<strong>at</strong>ed between1958 <strong>an</strong>d 1986The ET of 278 serogroup B meningococci recovered between 1958 <strong>an</strong>d 1986 wasdetermined in <strong>an</strong> earlier surveyY Two isol<strong>at</strong>es were lost in storage. Of the remaining276 isol<strong>at</strong>es, 7 were of phenotype B:4:P1.4 <strong>an</strong>d were all identified as ET-24. With 1ET-25 isol<strong>at</strong>e (B:4:NST, isol<strong>at</strong>ed in 1986) they formed <strong>an</strong> independent clone lineage(lineage HI), which appeared after 1981 in the Netherl<strong>an</strong>ds. This lineage containedno other strains, <strong>an</strong>d no Pl.4 strains outside this lineage were found.27
Chapter 2Table 6. Rel<strong>at</strong>ive distribution of scrotypes <strong>an</strong>d subtypes among serogroup C meningococci recoveredfrom p<strong>at</strong>ients with mcningococc<strong>nl</strong> disease in the Netherl<strong>an</strong>ds between 1980 <strong>an</strong>d 1990(n = 543)D<strong>at</strong>a [or year of recoveryVariable 1980 1983 1985 1986 1987 1988 1989 1990No. of isol<strong>at</strong>es lost in storage 6 0 0 0 0 0 0 0No. of isol<strong>at</strong>es tested 39 45 49 64 56 81 94 115Serotypes (%)1 15 4 8 3 7 0 I 32a 5 2 20 19 29 35 43 482b 0 2 0 5 9 7 7 174 21 22 22 13 18 16 11 914 5 2 2 2 4 2 I I15 3 0 2 3 2 I 2 216 0 2 2 2 5 I I 04/14 3 0 0 0 0 0 0 04/16 0 0 0 2 0 0 0 0Nonserotypcable 49 64 43 53 27 37 34 21SUbtypes (%)Pl.l 3 2 8 5 4 4 5 6P12 10 7 12 17 23 26 38 37PI.4 0 0 0 2 2 4 2 IPl.6 15 13 8 \3 0 5 3 3Pl.7 0 0 0 0 4 I 2 3P1.7,1· 8 9 8 \3 7 6 6 2Pl.7,I6 3 0 0 2 0 4 0 0Pl.9 0 0 2 0 2 0 0 1PI. 10 0 0 0 3 2 I I 10P1.l2 8 16 8 3 5 1 1 IP1.l4 21 4 6 9 9 0 3 IPJ.l5 3 11 6 0 5 4 4 2P1.l6 0 9 6 0 4 I I 3No nsubtypcnblc 31 29 35 34 34 43 32 32includes onc isol<strong>at</strong>e of subtypc P1.7,l,15, isol<strong>at</strong>ed in 1980Of the 10 B:4:P1.15 isol<strong>at</strong>es, 4 were of the ET-5 in lineage I, which appeared after1975 in the Netherl<strong>an</strong>ds. This lineage is also known as the ET-5 complex. Of theremaining 6 B:4:P1.15 isol<strong>at</strong>es, 5 were of genotypes in lineage X. Those isol<strong>at</strong>es wererecovered in 1965 (2), 1975 (1) <strong>an</strong>d 1978 (2). Lineage X contained no other phenotypes.The remaining 18 serotype 4 isol<strong>at</strong>es, which were NST or were of subtypesother th<strong>an</strong> P1.4 or P1.15, were of m<strong>an</strong>y different ETs. All 4 isol<strong>at</strong>es of the subtypecombin<strong>at</strong>ion P1.7,16 belonged to the ET-5 complex. Of those 4 isol<strong>at</strong>es, 3 were ofserotype 15 (ET-5) <strong>an</strong>d the other was of serotype 14 (ET-3). Of 10 P1.16-isol<strong>at</strong>es,o<strong>nl</strong>y 2 helonged to the ET-5 complex; the other 8 isol<strong>at</strong>es were of different ETs. All28
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