Inclusion Criteria:  Patients with SPA:  Patients ⩾ 18 years; Diagnosed as spondyloarthritis (SpA) according ASAS classification; Affiliated to a social security scheme; Have signed the written informed consent form.  Control subjects:  Subjects ⩾ 18 years; Subjects free of SPA and planned for a digestive endoscopy for another indication such as to explore the risk of colorectal cancer in family member; Affiliated to a social security scheme; Have signed the written informed consent form.  Exclusion Criteria:  Subjects unable to understand the proposed study and/or sign a informed consent form; Pregnant women or breast feeding women; Subjects under guardianship or curatorship; Have taken antibiotic 1 month prior to inclusion; Presenting acute or chronic severe pathology may likely to interfere with the interpret of outcome; Refusal of subjects to participate to the study; Foreign patients under french AME scheme.