In vitro activity of imipenem against anaerobic bacteria

The in vitro activity of imipenem, metronidazole, clindamycin, moxalactam, and cefoxitin against 203 strains of anaerobic bacteria isolated from patients at the Veterans Administration Wadsworth Medical Center in Los Angeles was studied. Imipenem and metronidazole were the most active agents overall, inhibiting 98% and 99%, respectively, of all anaerobes tested. At breakpoint levels all of the agents tested were very active against anaerobic cocci. Clostridium perfringens, and Bacteroides species other than those of the Bacteroides fragilis group. Imipenem, metronidazole, and clindamycin were the most active agents against the B. fragilis group in this study, although more recent experience with clindamycin indicates less potency. Marked variation among the susceptibility results obtained at various centers may be due to differences in technique, including inoculum size, media, and incubation time. In all instances, however, imipenem has clearly been the most active of the beta-lactam agents.