Susceptibilities of anaerobic bacteria to N-formimidoyl thienamycin (MK0787) and to other antibiotics.

The susceptibilities of 462 clinical anaerobic bacterial isolates to N-formimidoyl thienamycin and 16 other currently available and investigational antibiotics were determined by the agar dilution technique. N-Formimidoyl thienamycin was significantly more active than the reference antibiotics against most organisms tested, especially Bacteroides sp., including clindamycin-resistant strains. All 462 isolates were inhibited by 4 micrograms of N-formimidoyl thienamycin per ml, and no resistant strains were found in the species tested. N-Formimidoyl thienamycin was less active (i.e., had a higher 50% minimal inhibitory concentration) against Fusobacterium sp. than clindamycin, SM-1652, and piperacillin, and less active against Clostridium difficile than metronidazole, but was equally active or more active than the other reference antibiotics tested.