Susceptibility of Bacteroides ureolyticus to antimicrobial agents and identification of a tetracycline resistance determinant related to tetM.

The in-vitro activity of ten antimicrobial agents was evaluated for 28 clinical isolates of Bacteroides ureolyticus, an obligate anaerobe associated with non-gonococcal urethritis. The isolates were characterized by plasmid DNA profile and PAGE protein pattern. All isolates were inhibited at concentrations equal to or lower than the recommended breakpoint concentration for ampicillin (16 mg/l), metronidazole (16 mg/l) and erythromycin (4 mg/l). Twenty-seven isolates were inhibited by less than or equal to 2 mg/l of ciprofloxacin, pefloxacin and ofloxacin. Four isolates were tetracycline-resistant requiring 2-64 mg/l of tetracycline, minocycline or doxycycline for inhibition. In two tetracycline-resistant isolates tetM was demonstrated by dot-blot and Southern hybridizations. These two isolates did not contain a plasmid and had a PAGE protein pattern type III. These data confirm the spread of the tetM determinant in various bacteria of the genital tract.