Comparative activity of moxifloxacin in vitro against obligately anaerobic bacteria

The antimicrobial activity of moxifloxacin and seven other antibiotics (four of them quinolones) against 292 strains of obligately anaerobic bacteria was assessed employing a broth microdilution technique performed in Wilkens-Chalgren broth. MIC50/MIC90 values (mg/l) for moxifloxacin were as follows: Bacteroides fragilis (n=62) 0.25/2, Bacteroides ovatus (n=70) 1/4, Bacteroides vulgatus (n=29) 0.25/1, Bacteroides thetaiotaomicron (n=17) 2/2, Bacteroides caccae (n=11) 1/2, Prevotella spp. (n=11) 0.25/2, Fusobacterium spp. (n=17) 1/4, Bilophila wadsworthia (n=29) 0.5/1, and Clostridium spp. (n=29) 0.125/0.5, respectively. MIC50/MIC90 values (mg/l) for Bacteroides distasonis (n=8) and Peptostreptococcus spp. (n=9) were 0.25. The results indicated that moxifloxacin was almost as active as trovafloxacin, as active as gatifloxacin, and more active than levofloxacin and ciprofloxacin against the anaerobes tested.