SUSCEPTIBILITY OF ANAEROBIC-BACTERIA TO 9 ANTI-MICROBIAL AGENTS AND DEMONSTRATION OF DECREASED SUSCEPTIBILITY OF CLOSTRIDIUM-PERFRINGENS TO PENICILLIN

The activity of moxalactam, cefoxitin, cephalothin, cefamandole, chloramphenicol, clindamycin, metronidazole and ticarcillin was determined against 344 isolates of anaerobic bacteria. The activity of penicillin G was determined as well for 234 isolates not of the Bacteroides fragilis group. Moxalactam was more active than cephalothin and cefamandole and slightly less active than cefoxitin. Metronidazole was the most active antimicrobial agent against the B. fragilis group, chloramphenicol was most active overall. Clostridium spp. were the most resistant group of organisms tested. Relatively high concentrations of penicillin were required to inhibit the C. perfringens strains: 80% at 0.5 U/ml and 100% at 16 U/ml. The study demonstrates the need for periodic anaerobe susceptibility testing in order to better guide empiric antibiotic therapy.