Bacteria, genetics and irritable bowel syndrome

EVALUATION OF: Villani AC, Lemire M, Thabane M et al. Genetic risk factors for post-infectious irritable bowel syndrome following a waterborne outbreak of gastroenteritis. Gastroenterology 138, 1502-1513 (2010). While the pathogenesis of irritable bowel syndrome (IBS) remains to be fully defined, two clinical observations - the occurrence, de novo, of IBS following bacterial gastroenteritis and the history, commonly obtained from IBS patients, of other instances of the syndrome within their families - have instigated investigations, in IBS, of the potential roles, on the one hand, of the gut microbiota and the host response and, on the other hand, of genetic factors. The study reviewed here relates to both of these factors by studying genetic predisposition to postinfective IBS in a large population of individuals who were exposed to a multimicrobial enteric infection, which resulted in a severe outbreak of gastroenteritis and was followed by the development of IBS in over a third. In this detailed study, the investigators identified a number of genes that were linked significantly to the development of postinfectious-IBS in the Toll-like receptor 9, IL-6 and cadherin 1 regions. These genes play important roles in bacterial recognition, the inflammatory response and epithelial integrity, respectively, and provide considerable support for the hypothesis that links IBS onset to disturbances in the microbiota and the host response.