Classification of Neisseria meningitidis group B into distinct serotypes. II. Extraction of type-specific antigens for serotyping by precipitin techniques.

Over 10 distinct serotypes of group B Neisseria meningitidis have been found to date by using a sensitive microbactericidal assay developed by the authors. The serotype antigens have now been extracted by hot acid or saline extraction procedures. It was found that these extracted serotype antigens may be used in a simple capillary precipitin method. This method uses unadsorbed, undiluted rabbit antisera. In the capillary precipitin method a 3+ to 4+ reaction was considered significant. The microbactericidal assay and capillary precipitin methods for serotyping group B meningococci show excellent agreement. Group B meningococci were also serotyped by an agar gel double diffusion technique. The latter technique conserves reagents and has the further advantage that it does not show the minor cross-reactions observed in the capillary precipitin method. Thus two simple, reproducible methods for serological typing of group B meningococci have been developed. These methods developed for the serological typing of group B meningococci will aid in epidemiological studies of meningococcal disease. They may also be of value for selecting suitable strains for vaccine production.