Microbial factors in inflammatory bowel disease

An unsolved puzzle in IBD research is whether our germs, our genes, or a combination of the two with excessive immune responses to gut-associated bacteria explain the pathogenesis of UC and Crohn's disease. While a long search has so far failed to confirm a direct pathogenic role for a specific infectious agent, ample evidence suggests that commensual enteric bacteria and their products are the environmental "triggers" that initiate and perpetuate IBD, reactivate quiescent disease, result in the frequent septic complications of Crohn's disease, and contribute to the development of several extraintestinal manifestations of IBD. The most compelling evidence for involvement of the enteric flora in the pathogenesis of IBD has been generated from studies of animal models. Furthermore, therapeutic manipulation of the intestinal flora with antibiotics and, more recently, probiotics has been shown to be putative beneficial effects in humans and animal models. This article summarizes recent data implicating pathogenic and endogenous microbial factors in the pathogenesis of IBD and reviews the results of trial evaluating therapeutic manipulation of the intestinal flora.