Erythromycin-Resistant Neisseria gonorrhoeae and Oral Commensal Neisseria spp. Carry Known rRNA Methylase Genes

Two Neisseria gonorrhoeae isolates from Seattle and two isolates from Uruguay were resistant to erythromycin (MIC, 4 to 16 μg/ml) and had reduced susceptibility to azithromycin (MIC, 1 to 4 μg/ml) due to the presence of the self-mobile rRNA methylase gene(s) ermF or ermB and ermF. The two Seattle isolates and one isolate from Uruguay were multiresistant, carrying either the 25.2-MDa tetM-containing plasmid (Seattle) or a β-lactamase plasmid (Uruguay). Sixteen commensal Neisseria isolates (10 Neisseria perflava-N. sicca, 2 N. flava, and 4 N. mucosa) for which erythromycin MICs were 4 to 16 μg/ml were shown to carry one or more known rRNA methylase genes, including ermB, ermC, and/or ermF. Many of these isolates also were multiresistant and carried the tetM gene. This is the first time that a complete transposon or a complete conjugative transposon carrying an antibiotic resistance gene has been described for the genus Neisseria.