Synergistic activity of cefotaxime and desacetylcefotaxime against the Bacteroides fragilis group.

Sensitivities to cefotaxime (CTX) and its metabolite, desacetylcefotaxime (DCTX), alone and in combination, were determined for 77 organisms of the B. fragilis group. Synergy was observed in 23 (30%) of the strains, of which 21 were those that had a MIC to CTX alone of less than or equal to 16 micrograms/ml. In the remaining two strains, which were resistant to CTX alone, one strain was susceptible to the combination, while the second strain was not. In one strain of B. fragilis, the drug combination increased the MIC of CTX, but both the MIC and MBC remained in the susceptible range.