Serological classification of Neisseria gonorrhoeae by co-agglutination: a study of serological patterns in two geographical areas of Sweden.

Gonococcal strains, isolated in two different geographical areas of central Sweden (Stockholm and Orebro County) during two corresponding time periods, were subjected to serogrouping by the co-agglutination method with reagents covering the previously described serogroups W I, W II and W III. All strains tested could be grouped. Significant differences were found between the two geographical areas studied. Isolates from different sites on one and the same patient and strains from contact pairs gave identical results. The test results were reproducible, when the strains were exchanged between the two participating laboratories. The reagents distinguished Neisseria gonorrhoeae from other Neisseria species and other oxidase-positive bacteria. The potential of serogrouping gonococci for epidemiological studies by means of the co-agglutination method is discussed.