The comparative in-vitro activity of cefotetan against anaerobic bacteria.

The in-vitro activity of cefotetan, a new cephamycin, was assessed against a total of 336 strains of anaerobic bacteria by means of an agar dilution procedure and compared with that of cefoxitin, mezlocillin, piperacillin, clindamycin and metronidazole. Overall clindamycin and metronidazole were the most active of the test compounds. Cefotetan showed good activity against anaerobic cocci and clostridia, except for Clostridium difficile (MIC90 = 16 mg/l), although it was comparatively less active than the other beta-lactams against anaerobic cocci. In the case of the Gram-negative anaerobes, cefotetan showed moderate activity comparable to that of cefoxitin; against the 120 test strains of Bacteroides fragilis both cefotetan and cefoxitin were markedly more active than the penicillins. In studies with antibiotic combinations, cefotetan + cefsulodin showed marked synergy (FIC index less than 0.3) against the majority of strains of Bact. fragilis tested.