In vitro activity of seventeen antimicrobial agents against Gardnerella vaginalis.

The in vitro activity of 17 antimicrobial agents was tested against 25 clinical isolates of Gardnerella vaginalis. Minimum inhibitory concentrations were determined by agar dilution. The isolates were sensitive to penicillin, ampicillin, ticarcillin, piperacillin, cephalothin, cefoxitin, cefotaxime, cefoperazone, N-formimidoyl-thienamycin, chloramphenicol, clindamycin and erythromycin. MIC90 for the beta-lactam antibiotics ranged from 0.12 mg/l for penicillin to 2 mg/l for ticarcillin. Cefoperazone was the most active cephalosporin, inhibiting all isolates at 1.0 mg/l. N-formimidoylthienamycin was the most active of the newer beta-lactam compounds inhibiting all isolates with a concentration of 0.5 mg/l. Clindamycin and erythromycin were highly active, inhibiting all isolates at 0.6 mg/l. Susceptibility to tetracycline, gentamicin, metronidazole and tinidazole varied between strains. All isolates were resistant to rosoxacin. The hydroxy-metabolites of metronidazole and tinidazole were more active than the parent compounds, inhibiting all isolates.