Antimicrobial activity and synergism of cefuroxime on anaerobic bacteria.

In vitro efficacy of cefuroxime was tested against 333 clinical isolates of anaerobic bacteria, including 80 strains of Bacteroides fragilis. Its activity was compared with that of cefamandole and cefoxitin. In addition, the antimicrobial synergism of cefuroxime was tested in combination with either penicillin or carbenicillin against B. fragilis. At 16 microgram/ml, cefuroxime inhibited 70% of all anaerobic bacteria, but it was ineffective against 64% of B. fragilis strains tested. Cefuroxime in combination with penicillin or carbenicillin exerted excellent synergistic activity against two of the three isolates of B. fragilis tested and had an additive effect on the other. Although cefuroxime by itself is ineffective against B. fragilis, it acts synergistically with penicillin or carbenicillin.