In vitro activity of imipenem against gram-positive anaerobic bacteria.

The in vitro activity of imipenem, a new penem antibiotic, was determined against 210 clinical Gram-positive anaerobic isolates and compared with the activities of metronidazole, clindamycin, cefoxitin, moxalactam, ceftizoxime, ceftriaxone and cefotiam. All investigated strains were inhibited by a 4-mg/l concentration of imipenem. Cefoxitin demonstrated good activity against most strains with exception of some Clostridium difficile and Clostridium ramosum strains. Cephalosporins were classed in decreasing activity order as follows: cefoxitin moxalactam ceftriaxone ceftizoxime cefotiam. Metronidazole had better activity against Clostridium spp. than against non-sporulated bacilli. Clindamycin resistance rates were superior to 10% for most groups, with the exception of Clostridium perfringens. Actinomyces and Bifidobacterium. Imipenem was the most potent inhibitor, as 81% and 95% of tested strains were inhibited at concentrations of 0.25 and 0.5 mg/l respectively.