Serogrouping of Neisseria gonorrhoeae: identification of four immunologically distinct acidic polysaccharides.

A series of population-specific acidic polysaccharides have been described that can be used as a basis for serogrouping of Neisseria gonorrhoeae. These polysaccharides have been designated Gc antigens, and four immunologically distinct types have been identified. With these purified serogroup antigens and appropriately absorbed antisera in hemagglutination-inhibition systems, four typing systems have been established. Their sensitivities for purified homologous antigens range from 16 to 1 mug/ml. Purified heterologus antigens fail to inhibit at concentrations of 1,000 mug/ml. Clinically isolated N. gonorrhoeae are incorporated into these systems by conversion to standardized crude Gc antigen extracts by alkaline hhydrolysis. Of the 163 strains studied, 83% could be typed; 85% of these were typed for only one serogroup. Twenty strains were typed for two serogroups, and reisolation studies demonstrated that these strains were mosaics rather than mixed cultures. Four strains from each serogroup were selected, and antisera and purified serogroup antigens were produced from them. These were identical with their respective standard serogroup antigen and antisera in hemagglutination-inhibition and immunodiffusion systems.