Activity of the investigational fluoroquinolone finafloxacin and seven other antimicrobial agents against 114 obligately anaerobic bacteria.

The activity of finafloxacin against 73 strains of the Bacteroides fragilis group, 10 other Gram-negative anaerobic rods and 31 Clostridium difficile strains was determined by the broth microdilution technique. The activity was compared with that of moxifloxacin, levofloxacin, ciprofloxacin, clindamycin, imipenem, piperacillin/tazobactam and metronidazole. MIC(50/90) values (minimum inhibitory concentration, in μg/mL, at which 50% and 90% of the isolates tested are inhibited, respectively) for finafloxacin for the different species were determined: B. fragilis group, 0.5/2; other Gram-negative rods, 0.06/0.25; and C. difficile, 4/16. Furthermore, the MICs against 11 selected B. fragilis strains were determined under acidic conditions and resulted in MIC(50/90) values for finafloxacin of 0.25/4 μg/mL. Thus, finafloxacin shows promising activity against several pathogenic species of anaerobes. Furthermore, finafloxacin has increased activity against selected B. fragilis strains under acidic conditions compared with activity at neutral pH.