Identification of Fecal Microbiota Biomarkers of Spondyloarthritis in Patients Suffering From Crohn's Disease.

Inclusion Criteria: * Age ≥ 18 years. * Patients will be recruited according to 3 groups: * Patients with Crohn's disease and axial spondyloarthritis according to the criteria below. * Patients with Crohn's disease (MC patients) with a diagnosis established according to clinical, biological criteria, radiological, endoscopic and / or histological studies for 3 months. With diagnosis of exclusion of a spondyloarthritis on criteria ASAS and / or New York modified. * Patients with axial spondyloarthritis (SpA patients) with a diagnosis based on modified ASAS and / or New York criteria with exclusion diagnosis of Crohn's disease. * Patient with the ability to give free and express informed consent. Exclusion Criteria: * History of colonic resection * Taking antibiotics or colon preparation for colonoscopy within 8 weeks before stool collection (Temporary contraindication = removal possible before colic or first bowel preparation after the start of colonic preparation). * Ostomy at the time of sampling * BMI\> 30 * extreme diet * unbalanced diabetes * Pregnant woman * Patient under guardianship, under curatorship or under the protection of justice Contacts/Locations Central Contact