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

Who May Qualify: - 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 willing to sign a consent form. Who Should NOT Join This Trial: - 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 Always talk to your doctor about whether this trial is right for you.