Virulence markers in patient and carrier strains of Neisseria meningitidis.

Patient and carrier strains of Neisseria meningitidis from 2 different periods were compared with respect to serogroups, serotypes and sensitivity to sulphadiazine. The majority of 249 patient strains were resistant to sulphadiazine, and belonged to the groups A, B or C. The group B and C strains were mainly type 15/16 and 2, respectively. In contrast, most of the 400 carrier strains belonged to serotypes other than 2 or 15/16, or were non-typable, and most strains were sensitive to sulphadiazine. Among the resistant group B and C carrier strains there were more type 2 and 15/16 strains than would have been expected from the average. The virulence markers: serogroup A, B and C, serotype 2 and 15/16, and resistance to sulphadiazine, coexist in more carrier strains than would be expected if the distribution of these markers was random.