Bacteremia Due to Bacteroides fragilis Group: Distribution of Species, β-Lactamase Production, and Antimicrobial Susceptibility Patterns

Abstract

ABSTRACT A retrospective analysis of susceptibility data on 542 blood isolates of the Bacteroides fragilis group tested from 1987 to 1999 by the same NCCLS-recommended broth microdilution method throughout is presented. Metronidazole, β-lactam-β-lactamase inhibitor combinations, carbapenems, and trovafloxacin were the most active agents (susceptibility of ≥93%). Among the cephalosporin-cephamycins, the order of activity was cefoxitin > ceftizoxime > cefotetan = cefotaxime = cefmetazole > ceftriaxone. All isolates were resistant to penicillin G, and 22% were resistant to clindamycin. The susceptibility rates to piperacillin-tazobactam, imipenem, and meropenem were affected least among isolates resistant to cefoxitin or clindamycin. Except for piperacillin-tazobactam, imipenem, and meropenem, the B. fragilis species was more susceptible than were the non- B. fragilis species. These data underscore the importance of susceptibility testing of the B. fragilis group and can serve as a guide in the choice of empirical antimicrobial therapy.