Bezlotoxumab is not an antibiotic. It is a selective, fully-human, monoclonal antibody designed to neutralize C. difficile toxin B, a toxin that can damage the gut wall and cause inflammation, leading to the symptoms of C. difficile enteritis, which include abdominal pain and watery diarrhea. Bezlotoxumab was developed by researchers at the University of Massachusetts Medical School’s MassBiologics Laboratory in conjunction with Medarex (now part of Bristol-Myers Squibb), and licensed to Merck in 2009 for development as a potential therapeutic for C. difficile infection.
To read more, here is the source: Merck: Phase 3 Studies of Bezlotoxumab to Prevent Clostridium Difficile Infection Recurrence