Bactericidal activity of DU-6859a compared to activities of three quinolones, three beta-lactams, clindamycin, and metronidazole against anaerobes as determined by time-kill methodology

The activities of DU-6859a, ciprofloxacin, levofloxacin, sparfloxacin, piperacillin, piperacillin-tazohactam, imipenem, clindamycin, and metronidazole against 11 anaerobes were tested by the broth microdilution and time-kill methods, DU-6859a was the most active drug tested (broth microdilution MICs, 0.06 to 0.5 mu g/ml), followed by imipenem (MICs, 0.002 to 4.0 mu g/ml). Broth macrodilution MICs were within 3 (but usually 1) dilutions of the broth microdilution MICs. All compounds were bactericidal at the MIC after 48 h; after 21 h, 90% killing was shown for all strains when the compounds were used at four times the MIC. DU-6859a at less than or equal to 0.5 mu g/ml was bactericidal after 38 h.