Metronidazole antibiotic pills, held in a hand. This antibiotic drug is used in the treatment of anaerobic bacterial infections, particularly psuedomembranous colitis, a severe infection of the colon. Pseudomembranous colitis is caused by the bacterium Clostridium difficile. It usually occurs after the normal gut flora has been destroyed by a course of antibiotics, allowing Clostridium. difficile to flourish.
