Comparative activity of beta-lactamase inhibitors YTR 830, clavulanate, and sulbactam combined with beta-lactams against beta-lactamase-producing anaerobes

The in vitro activities of the beta-lactamase inhibitors YTR 830, clavulanate, and sulbactam combined with six beta-lactams against 88 beta-lactamase-producing anaerobes were determined. When combined with the beta-lactams, the three beta-lactamase inhibitors showed no synergy against the 10 Bacteroides fragilis homology group II strains. When the beta-lactams were combined with the inhibitors, their geometric mean MICs against the remaining 78 strains were reduced from 4.2 to 150.2 micrograms/ml to 0.2 to 12.9 micrograms/ml. The activity of the beta-lactams combined with the beta-lactamase inhibitors was significantly greater than that of the beta-lactams alone against all groups except B. fragilis homology group II, with 76 to 100% of the strains susceptible to ampicillin plus inhibitor and greater than or equal to 90% susceptible to the other combinations.