Susceptibility of the Bacteroides fragilis group to newer quinolones and other standard anti-anaerobic agents

The susceptibilities of 200 clinical isolates of the Bacteroides fragilis group to four quinolones (moxifloxacin, clinafloxacin, trovafloxacin and ciprofloxacin) were determined, as well as to cefoxitin, clindamycin, metronidazole, imipenem and ticarcillin–clavulanic acid. The results for the latter five agents were compared with those of a study on 200 isolates done 6 years previously. Clinafloxacin and trovafloxacin were the most active agents tested with MIC90s lower than all other antimicrobials except imipenem. Susceptibility rates for imipenem, ticarcillin– clavulanic and metronidazole continue to be high, although resistant strains are emerging. For ticarcillin–clavulanic acid and metronidazole, MIC90s increased four- to eight-fold for the B. fragilis species between the two study periods.