Comparative in vitro activities of amoxicillin-clavulanic acid and imipenem against anaerobic bacteria isolated from community hospitals

The susceptibilities of recent clinical isolates of anaerobic bacteria from two community hospitals were determined. Thirty percent of pigmented Bacteroides species and bile-sensitive, nonpigmented Bacteroides species produced penicillinase and were resistant to amoxicillin. Cefoxitin and clindamycin showed good activity against most strains, with the exception of rare isolates of the Bacteroides fragilis group and some strains of Clostridium species. While amoxicillin was not active against B. fragilis and other members of the B. fragilis group, amoxicillin-clavulanic acid was very active against almost all of these organisms. Imipenem was the most potent agent against all strains tested.