Delayed Colonic Transit is Associated with a Decrease of the Normal Predominant Bacteria in the Colon Microbiota

Introduction/Aims: Post-infectious irritable bowel syndrome (PI-IBS) may develop in 4% to 30% of affected patients following bacterial gastroenteritis (GE), but limited information is available on outcome of viral GE. During summer 2009 a massive outbreak of viral GE associated with contamination of municipal drinking water (Norovirus and Enterovirus) occurred in San Felice del Benaco (Lake Garda, Italy) [1]. In order to investigate the natural history of a community outbreak of viral GE and to assess the incidence of functional gastrointestinal disorders and PI-IBS, we carried out a prospective population-based cohort study with control group. Methods: Baseline questionnaires were administered to the resident community within one month of the outbreak. Follow-up questionnaires of the Italian version of Gastrointestinal Symptom Rating Scale (GSRS, a 15 item survey scored according to a 7-point Likert scale) were mailed to all patients responding to baseline questionnaire at 3 and 6 months and to a cohort of unaffected controls, living in the same geographical area, at 6 months after the outbreak. GSRS itemwere grouped into five dimensions: abdominal pain, reflux, indigestion, diarrhea and constipation. At month 12 all patients and controls were interviewed by an health assistant in order to verify Rome III criteria of IBS. T-test and χ2 or fisher's exact test were used as appropriate. Results: Baseline questionnaires were returned by 348 patients: mean age ± SD 45 ± 22 years, 53% female. At outbreak nausea (scored ≥4), vomiting and diarrhea lasting 2-3 days or more were reported by 66%, 60% and 77% of patients, respectively. Fifty percent reported fever and 19% referred weight loss (mean 3 Kg). Follow-up surveys were returned at month 6 by 185 patients and 168 controls: mean of GSRS score for each dimension is reported in the figure. At month 12 we identified 40 patients with a new diagnosis of IBS (Rome III criteria), in comparison with 3 subjects in the control cohort (p<0.0001; OR 11.40, 3.44-37.82, 95%CI). The 40 cases of PI-IBS, according to the subclassification of IBS by predominant stool pattern [2], were subtyped as follow: 4 IBS with constipation, 7 IBS with diarrhea, 16 with mixed IBS and 13 with unsubtyped IBS. Conclusion: Our study provides evidence that mixed Norovirus and Enterovirus GE may lead to post-infectious gastrointestinal disordes which persist for at least 12 month after infection. PI-IBS following viral infections develops in a substantial proportion of patients (22%) similar to that reported after bacterial GE. References: 1) Scarcella et al. Eurosurveillance 2009 2) Longstreth et al, Gastroenterology 2006.