Serotype protein agglutinogens of Neisseria gonorrhoeae.

The distribution among Neisseria gonorrhoeae strains of the serotype protein agglutinogens (SPA) carried by the laboratory strains VII, V, and 8551 was studied. The bacterial outer membrane was isolated, treated with periodate, and used for immunization of rabbits. Each antiserum was cross-absorbed with both of the heterologous strains and examined by a bacterial agglutination test against 42 other gonococcal isolates, including laboratory strains and recent clinical isolates. In all, 36 of the isolates could be serotyped, 23 of which carried SPA VII, six SPA V, three SPA 8551, and four both of the SPAs V and 8551. Antiserum was prepared in a similar way against each of the six strains that could not be serotyped. These antisera showed varying patterns of cross-reactivity, depending on the strains used for cross-absorption.