In-vitro activity of cefoperazone-sulbactam against Bacteroides species

The in-vitro activity of two combinations of sulbactam and cefoperazone against 187 strains of Bacteroides fragilis were evaluated; their activity was compared with that of the drugs alone, and correlated with the production of beta-lactamase by the bacterial strains. The results indicated that both combinations had a synergistic effect: the addition of 8 mg/l of sulbactam to the MIC of cefoperazone reduced the percentage of resistant strains from 58% to 0.5%; while the combination of two parts of cefoperazone to one pact of sulbactam lowered the resistance rate to 1%. Synergy was observed most frequently with beta-lactamase positive strains, but it also occurred among beta-lactamase negative strains.