Study of the In Vitro Activities of Rifaximin and Comparator Agents against 536 Anaerobic Intestinal Bacteria from the Perspective of Potential Utility in Pathology Involving Bowel Flora

Rifaximin, ampicillin-sulbactam, neomycin, nitazoxanide, teicoplanin, and vancomycin were tested against 536 strains of anaerobic bacteria. The overall MIC of rifaximin at which 50% of strains were inhibited was 0.25 microg/ml. Ninety percent of the strains tested were inhibited by 256 microg/ml of rifaximin or less, an activity equivalent to those of teicoplanin and vancomycin but less than those of nitazoxanide and ampicillin-sulbactam.