Therapeutic Efficacy of Moxifloxacin, a New Quinolone, in the Treatment of Experimental Intra-Abdominal Abscesses Induced by <i>Bacteroides fragilis </i>in Mice

Moxifloxacin, a new quinolone, is effective in vitro against several anaerobic bacteria including Bacteroides fragilis, but its in vivo activity against anaerobic infections is not known. In this study, we evaluated the in vivo activity of moxifloxacin in the treatment of experimentally induced intra-abdominal abscesses (IAA) caused by B. fragilis. For comparison, clindamycin, metronidazole, and levofloxacin were used, and saline for control. Absence of bacteria (sterile) in the abscess pus was required to call it a cure. Mice were intraperitoneally injected with B. fragilis plus sterile rat feces and barium sulfate. Animals were treated with moxifloxacin (40 mg/kg/b.i.d.), clindamycin (75 mg/kg/b.i.d.), levofloxacin (40 mg/kg/b.i.d.) or metronidazole (75 mg/kg/b.i.d.) for 10 days. The cure rate was 12% in controls on saline therapy, 57% on metronidazole, 67% on levofloxacin, 73% on moxifloxacin and 79% on clindamycin. The therapeutic efficacy of moxifloxacin in this B. fragilis infection was not significantly different from that observed with clindamycin. By virtue of its established efficacy on gram-negative aerobic bacteria and the observed in vivo efficacy on B. fragilis, moxifloxacin can be evaluated in the treatment of clinical anaerobic infections.