THE VIRGIN POPULATION OF NEISSERIA-GONORRHOEAE IN STOCKHOLM HAS DECREASED AND ANTIMICROBIAL RESISTANCE IS INCREASING

Aims-To investigate the evolution of chromosomal and plasmid mediated resistance for ampicillin and tetracycline of N gonorrhoeae strains in Stockholm during 1982-1993. Methods-A total of 404 gonococcal strains isolated in 1982, 1987, 1990, 1992, 1993 were analysed for minimal in hibitory concentrations (MIC) of ampicillin and tetracycline and for p lasmid content. MIC values were determined by the agar dilution method and plasmid preparations were performed using alkaline lysis. To dete ct additional gonococcal strains with tet(IM) plasmids all strains iso lated in 1988-1989 and 1991, in all 234 isolates, were analysed retros pectively for MIC values of tetracycline. If an MIC value of greater t han or equal to 4 0 mg/l was recorded plasmid analysis was performed. Results-Increased proportions of chromosomally mediated resistance to te tracycline (p < 0.001) as well as plasmid mediated resistance to bo th ampicillin (p < 0.02) and tetracycline were found in the later part of the study. In 1991 the first gonococcus with tet(M) plasmid was is olated in Sweden. The proportion of strains with chromosomally mediate d resistance for ampicillin did not change during the study period. Th e proportion of gonococcal strains with the 39 kb conjugative plasmid was increased in the later part of the study. Conclusions-The increase d proportion of N gonorrhoeae strains with resistance to ampicillin an d tetracycline is most likely due to importation of strains from areas with high prevalence of antibiotic resistant gonococci. The proportio n of N gonorrhoeae strains with tet(M) plasmids is low in Sweden, but might increase in the same way as the proportion of PPNG strains has i ncreased during 1982-1993.