Microbiota, gastrointestinal infections, low-grade inflammation, and antibiotic therapy in irritable bowel syndrome: an evidence-based review.

BACKGROUND Post-infectious irritable bowel syndrome (PI-IBS) prevalence, small intestinal bacterial overgrowth (SIBO), altered microbiota, low-grade inflammation, and antibiotic therapy in IBS are all controversial issues. AIMS To conduct an evidence-based review of these factors. METHODS A review of the literature was carried out up to July 2012, with the inclusion of additional articles as far as August 2013, all of which were analyzed through the Oxford Centre for Evidence-Based Medicine (OCEBM) system. RESULTS 1.There is greater SIBO probability in IBS when breath tests are performed, but prevalence varies widely (2-84%). 2.The gut microbiota in individuals with IBS is different from that in healthy subjects, but a common characteristic present in all the patients has not been established. 3.The incidence and prevalence of PI-IBS varies from 9-10% and 3-17%, respectively, and the latter decreases over time. Bacterial etiology is the most frequent but post-viral and parasitic cases have been reported. 4.A sub-group of patients has increased enterochromaffin cells, intraepithelial lymphocytes, and mast cells in the intestinal mucosa, but no differences between PI-IBS and non-PI-IBS have been determined. 5.Methanogenic microbiota has been associated with IBS with constipation. 6.Rifaximin at doses of 400mg TID/10days or 550mg TID/14days is effective treatment for the majority of overall symptoms and abdominal bloating in IBS. Retreatment effectiveness appears to be similar to that of the first cycle. CONCLUSIONS Further studies are required to determine the nature of the gut microbiota in IBS and the differences in low-grade inflammation between PI-IBS and non-PI-IBS. Rifaximin has shown itself to be effective treatment for IBS, regardless of prior factors.