Rapid serogroup identification of Neisseria meningitidis by using antiserum agar: Prevalence of serotypes in a disease-free military population.

Nasopharyngeal cultures from 414 Marines were plated directly onto antiserum agar containing the antibiotics vancomycin, colistin, and nystatin for meningococcal isolation and serogroup identification. Meningococci were isolated from 267 Marines, giving a carrier prevalence of 64.5%. A total of 58% of the isolates could be placed into serogroups; of these 22.3% were group B, 4.7% were group C, 25.7% were group Y, 24.3% were group W135, and 23.0% were group 29E. No serogroup A organisms were recovered. Serotyping by agar gel double diffusion was performed on 148 strains. More than 70% of these strains were nontypable, and the disease-associated serotype 2 was present only in two group Y isolates. The same 148 isolates were also classified by major outer membrane protein patterns after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polyacrylamide gel electrophoresis pattern IV was most common among all serogroups. The data demonstrate the effective use of antiserum agar for meningococcal surveillance and document the frequency of specific serotypes and polyacrylamide gel electrophoresis types among carrier isolates obtained from a nonrecruit military population.