Synergistic activity of cefsulodin combined with cefoxitin and sulbactam against Bacteroides species.

The in-vitro activity of cefsulodin combined with sulbactam, cefoxitin or cefotaxime was investigated against 32 strains of beta-lactamase-producing Bacteroides species. Synergy of cefsulodin-sulbactam or cefsulodin-cefoxitin could be demonstrated against 30 of 32 and 32 of 32 strains tested at the concentrations readily achievable in serum. In the presence of 1 mg/l of sulbactam or cefoxitin, more than 90% of the Bacteroides isolated were inhibited by 32 mg/l of cefsulodin. The inhibitory activity of cefsulodin-sulbactam or cefsulodin-cefoxitin combinations was bactericidal against Bact. fragilis and Bact. vulgatus. In contrast, no synergistic inhibitory or bactericidal activities can be observed by the cefsoludin-cefotaxime combination. Both sulbactam and cefoxitin were potent inhibitors of beta-lactamases produced by Bact. fragilis and Bact. melaninogenicus suggesting that this inhibitory activity might be one of the factors contributing to the synergistic combinations.