Pulsed-field gel electrophoresis as an epidemiologic tool for Neisseria gonorrhoeae -: Identification of clusters within serovars

Background: The increasing incidence of gonorrhea in Sweden in 1998 was due to mostly domestic cases. Among these, two core groups were identified: homosexual men with serovar IB-2 and young heterosexuals with serovar IB-3. Goals: To explore the genetic homogeneity/heterogeneity within the predominant serovars, IB-2 and IB-3, of Neisseria gonorrhoeae in Sweden by pulsed-field gel electrophoresis (PFGE) and to compare these results to epidemiologic information, as well as examine the genetic diversity within and between the 25 other represented serovars of N gonorrhoeae. Study Design: By PFGE, 237 N gonorrhoeae isolates were examined, and the results were compared with epidemiologic data for the IB-2 and IB-3 isolates. Results: In 79% of the domestic IB-2 cases involving homosexuals and 66% of the domestic IB-3 cases involving young heterosexuals, the isolates were genetically indistinguishable by PFGE. A high genetic diversity was identified within and between the 27 included serovars. Conclusions: Examination by means of PFGE indicated that one N gonorrhoeae clone each of the serovars IB-2 and IB-3 created the majority of the two core groups of domestic cases.