Single-center Exploratory Study of the Intestinal Microbiota in Patients Treated for Irritable Bowel Syndrome With Predominant Constipation and Methane Production

Inclusion Criteria: * Patient suffering from Irritable Bowel Syndrome (IBS) (abdominal pain for the past 6 months occurring on average at least 1 day per week in the last 3 months, with at least 2 of the following criteria: associated with defecation, associated with a change in stool frequency, associated with a change in stool consistency): 1. Predominant constipation type (IBS-C): Bristol Stool Scale 1-2 ≥ 25% of the time and Bristol Stool Scale 6-7 ≤ 25% of the time 2. Alternating diarrhea-constipation type (IBS-M): Bristol Stool Scale 1-2 25% of the time and Bristol Stool Scale 6-7 25% of the time 3. Unspecified type: absence of sufficient criteria to meet criteria for IBS-C, IBS-D, or IBS-M. * Patient exhibiting a high methane level (≥ 10 ppm) during a glucose breath test. * Aged ≥ 18 years at the time of study entry. * Patient not opposing participation in the study. Exclusion Criteria: * Patient who has been treated with antibiotics or probiotics in the last 3 months prior to inclusion. * Patient suffering from diarrhea-predominant IBS (Bristol Stool Scale 6-7 ≥ 25% of the time and Bristol Stool Scale 1-2 ≤ 25% of the time). * Patient with a history of abdominal surgery other than appendectomy and cholecystectomy. * Patient with a history of celiac disease. * Patient with proven inflammatory bowel disease. * Patient with a history of colorectal cancer. * Patient with uncontrolled hypothyroidism. * Patient with uncontrolled diabetes. * Pregnant or breastfeeding women. * Patient deprived of liberty by a judicial or administrative decision. * Adult patient under legal protection (guardianship, curators). * Patient unable to discontinue proton pump inhibitor treatment during the study period