Cluster analysis of Neisseria meningitidis type 22 strains isolated in Poland.

The aim of this study was to investigate the genetic relationships among strains belonging to Neisseria meningitidis serotype 22 recovered in Poland from 1995 to 1998. Phenotypical characterisation of meningococcal strains isolated from patients with meningococcal disease has been performed since 1995. Strains belonging to Neisseria meningitidis type 22 were most frequently recovered from severe cases of meningitis and septicaemia. The type 22 strains were separated into clusters by serosubtyping and DNA analyses by pulsed-field gel electrophoresis and ribotyping. However, the grouping according to serosubtypes was quite different from that obtained by ribotyping and pulsed-field gel electrophoresis. Furthermore, the two genotyping methods seldom identified the same clusters, nor were clusters identified among 26 Neisseria meningitidis type 22 strains recovered from patients hospitalised in five cities. Determination of the susceptibility to penicillin showed that a single strain was resistant (MIC, 2 mg/l) and that one-third (24/71) of the strains tested had reduced susceptibility (MIC range, 0.1-1 mg/l).