Serological classification and genetic characterization of clinical isolates of Neisseria gonorrhoeae

Neisseria gonorrhoeae is the etiologic agent of gonorrhoea, one of the oldest and most widespread of human infections. The development of methods to characterize the bacterium is of central importance in the control of the disease. One aim of this thesis was to evaluate serotyping of N.gonorrhoeae strains with monoclonal antibodies directed to Protein I in a clinical setting. The subdivision of gonococcal isolates into serovars was stable with the GS panel of monoclonal antibodies tested. Serovar analysis using the coagglutination technique is simple, rapid and does not require expensive equipment. It has a better resolution than auxotyping and is well suited for routin-testing of clinical samples. In a one year study in 1982-1983, N.gonorrhoeae strains of serogroup WII/III were more common than strains of serogroup WI. The serogroups were not equally distributed among women, heterosexual men and homosexual men. Different serovars dominated among strains from heterosexual and homosexual patients. However, many of the serovars confined to only one of the subpopulations represented a small number of isolates.

Decreased susceptibility to multiple antibiotics was found in all serogroup WII/III transformants studied indicating a possible genetic linkage between the por gene and locus/loci coding for resistance to antibiotics. The proportions of gonococcal strains with chromosomally mediated resistance to tetracycline increased during 1982-1993, especially during the latter part of the study. Gonococcal strains carrying tet(M) plasmids were first isolated in Sweden in 1991. The proportion of penicillinase producing N.gonorrhoeae isolates increased at Stockholm Söder Hospital 1982-1993. The serovar analysis of N. gonorrhoeae strains carrying plasmids encoding for antibiotic resistance implies a minor spread of these strains in Stockholm. This emphasizes the importance of susceptibility testing of all N.gonorrhoeae isolates. PilC is a 110 kD pilus-associated minor outer membrane protein involved in the biogenesis of pilus. The pilC gene of a N.gonorrhoeae strain isolated from disseminated gonococcal infection showed 88% homology with pilC2 of N.gonorrhoeae strain MS11 and 84% homology with pilCI of MS11. Ten variable cassettes were identified. This suggests that PilC is a antigenically diverse protein. The pilC gene was also present in two other clinical isolates tested. The strains examined belonged to different serovars.