Study of Gut Microbiota in Crohn's Disease Patients Suffering From Spondylarthritis

Inclusion Criteria: * Patients with Crohn's disease and axial spondyloarthritis according to the criteria below. * Patients with Crohn's disease (CT patients) diagnosed according to clinical, biological, radiological, endoscopic and / or histological criteria for 3 months. With diagnosis of spondyloarthritis exclusion on modified ASAS and / or New York criteria. * Patients with axial spondyloarthritis (SpA patients) diagnosed according to the modified ASAS and / or New York criteria with exclusion diagnosis of Crohn's disease. * Patient with the capacity to give free and informed consent. Exclusion Criteria: Antecedent of colonic resection * Antibiotic or colonic colonoscopy preparation in the 8 weeks prior to stool collection (against temporary indication = collection possible before colic preparation or on the first saddle after the start of the colic preparation). * Ostomy at time of collection * BMI\> 30 * extreme diet * unbalanced diabetes * Patient under guardianship, under curatorship or under safeguard of justice