Therapeutic Manipulation of the Microbiota in Inflammatory Bowel Disease: Antibiotics and Probiotics

The microbiota represents an essential component of the pathogenesis of IBD. Some components of the microbiota are required for mucosal homeostasis and protection against injury; whereasothers are a potential risk factor for IBD, depending on the genetic status of the host. This provides the rationale fortherapeutic manipulation or optimization of the microbiota. Antibiotics directed non-specifically against the microbiota may have a role in colonic rather than small bowel Crohn'sdisease. Their apparent efficacy may relate to increased mucosal numbers of bacteria. Trials of antibiotics directed at Mycobacterium avium subspecies paratuberculosis in Crohn's disease have beenlimited, but negative or inconclusive, to date. There is strong anecdotal clinical support for antibiotics such as metronidazole and ciprofloxacin in pouchitis, but littleevidence for these in uncomplicated ulcerative colitis. Despite the strong rationale for probiotics, they have been remarkably disappointing in clinical trials in Crohn's diseasebut more encouraging in ulcerative colitis. The best results have been reported in pouchitis but a favorable experienceis not uniform.