In vitro activity of meropenem compared with imipenem, metronidazole, ampicillin, and ampicillin/sulbactam against anaerobes.

The aim of the present study was to compare the in vitro activity of meropenem (ICI 194660, CAS 96036-03-2) with imipenem, metronidazole, clindamycin, ampicillin and ampicillin/sulbactam against a variety of anaerobic bacteria using an agar dilution method. 423 clinical isolates were tested belonging to 70 species of 15 anaerobic genera. They included Bacteroides fragilis (n = 62), Bacteroides thetaiotaomicron (n = 45), Prevotella bivia (n = 11), Fusobacterium nucleatum (n = 12), Clostridium perfringens (n = 15) and several rarely isolated species and genera, e.g. Selenomonas sputigena and Clostridium symbiosum. Bacteroides species were inhibited by meropenem at < or = 2.0 micrograms/ml, Clostridium species, including C. difficile, at < or = 4.0 micrograms/ml and all the other anaerobes at < or = 0.5 microgram/ml. Meropenem and imipenem were the most active substances, but often equal to, or only slightly better than, metronidazole, clindamycin or ampicillin/sulbactam, dependent on species. Meropenem was especially active against Bacteroides gracilis (MIC90 0.015 microgram/ml), Prevotella disiens (MIC90 0.03 microgram/ml), Fusobacterium nucleatum (MIC90 0.015 microgram/ml), Clostridium perfringens (MIC90 0.015 microgram/ml) and Veillonella parvula (MIC90 0.03 microgram/ml). The results obtained indicate that meropenem might be a useful adjunct to chemotherapy of anaerobic and mixed aerobic and anaerobic infections.