Frequency in the United States of Non-/3-Lactamase-Producing Strains of Neisseria gonorrhoeae Possessing the 24.5-Mdal Conjugative Plasmid

We characterized 475 non-beta-lactamase-producing gonococcal isolates from five U.S. cities by auxotype, serovar, and plasmid content to determine the frequency of isolates with the 24.5-Mdal gonococcal conjugative plasmid. A total of 150 (32%) of all isolates possessed the 24.5-Mdal plasmid; these isolates represented between 10% and 53% of isolates from each city. Isolates possessing the 24.5-Mdal plasmid belonged to 45 (56%) of 81 auxotype/serovar (A/S) classes, or between 24% and 70% of the A/S classes isolated in each city. Overall, a higher proportion of strains isolated in the southern cities possessed the 24.5-Mdal plasmid than did those from northeastern or northwestern cities. These strains appear to have spread independently of the spread of beta-lactamase-producing Neisseria gonorrhoeae strains. The prevalence of N. gonorrhoeae strains with the 24.5-Mdal conjugative plasmid has increased substantially and may have important implications for the epidemiology of gonorrhea caused by beta-lactamase-producing strains.