Serologic classification and contact-tracing in the control of microepidemics of beta-lactamase-producing Neisseria gonorrhoeae.

Serologic classification of isolated gonococcal strains and thorough contact-tracing were proved to be valuable in controlling an indigenous outbreak of infections caused by beta-lactamase-producing Neisseria gonorrhoeae (PPNG). Only 1-2% of gonococcal strains isolated in Sweden are PPNG, and before 1983 most of them were imported. During January-August 1983, 43 PPNG strains were isolated from 42 patients in Gothenburg. The PPNG strains were auxotyped and classified serologically. PPNG strains of serogroup WI, serovar (subgroup) Ae and of the prototrophic auxotype were isolated from 27 patients, including six prostitutes. Information obtained at interviews with these patients indicated that there had been a chain of infections. Quick and thorough contact-tracing stopped this microepidemic within three months. The serologic classification of the PPNG strains helped us to concentrate the epidemiologic efforts on those persons known to be infected with the epidemic strain, to trace this infection to other parts of Sweden, and to determine when the outbreak was finished.