In vitro comparison of cefoperazone/sulbactam with selected antimicrobials against 300 bacteroides isolates. Inhibitory activity and time-kill kinetic studies.

The susceptibilities of 258 Bacteroides fragilis group isolates and 42 other Bacteroides species isolates against cefoperazone, cefoperazone/sulbactam (2:1 ratio) and selected other antimicrobials were determined by broth microdilution method. All isolates were susceptible to cefoperazone/sulbactam, ampicillin/sulbactam, ticarcillin/clavulanate, metronidazole, and imipenem. Other antibiotics showed variables levels of resistance (5-30%). Killing curves with the cef/sulb against selected B. fragilis group isolates were performed and showed excellent bactericidal activity at two to four times the minimum inhibitory concentration (MIC) after 12 hr incubation, even against the isolates with high cefoperazone MICs (greater than or equal to 64 micrograms ml). There was no regrowth at 24 hr. Cefoperazone/sulbactam is a compound with excellent inhibitory and bactericidal activity against B. fragilis group isolates.