Beta-lactamases from Bacteroides fragilis active against oximino-cephalosporins

Four clinical isolates of Bacteroides fragilis were resistant to penicillins and cephalosporins with exception to 7-alpha-methoxy cephalosporins such as latamoxef (moxalactam) and cefoxitin. In contrast the 6-alpha-methoxy penicillin temocillin was not active. The beta-lactam resistance correlates with the presence of two beta-lactamases with an isoelectric point (IEP) = 4.9 and 5.4, respectively. The necessity of antimicrobial susceptibility testing before the therapy of infections with anaerobic bacteria is discussed.