Susceptibility of Mobiluncus species to 23 antimicrobial agents and 15 other compounds.

The susceptibility of 12 strains of Mobiluncus curtisii and 10 strains of M. mulieris to 23 antimicrobial agents and 15 other compounds was determined. All strains were susceptible to chloramphenicol, clindamycin, rifampin, tobramycin, vancomycin, virginiamycin, and all beta-lactam antibiotics tested, including imipenem. One strain of M. mulieris was resistant to erythromycin and josamycin. All were resistant to colistin, cycloserine, nalidixic acid, and neomycin. Tetracycline had variable activity. All M. curtisii strains were resistant to metronidazole and its hydroxy metabolite. Of 10 M. mulieris strains, 5 were resistant to metronidazole and 2 were resistant to its hydroxy metabolite. All 12 M. curtisii and 1 of 10 M. mulieris strains were resistant to tinidazole. M. curtisii and M. mulieris produced two mutually exclusive clusters of MICs when tested against ampicillin, cefoxitin, cephalothin, moxalactam, alizarin red, Evans blue, and sodium fluoride. Gardnerella vaginalis was more susceptible to Nile blue A than was either M. curtisii or M. mulieris. Clindamycin and imipenem may be useful agents in the therapy of metronidazole-resistant bacterial vaginosis. Metronidazole, tinidazole, and Nile blue A may be of value in the development of a selective agar for Mobiluncus species.