Inclusion Criteria:  For patient with spondyloarthritis:  Diagnosed for spondyloarthritis or pure axial or axial type psoriatic rheumatism according to Assessment of Spondyloarthritis International Society (ASAS) criteria. Requiring treatment with anti-TNFα or anti- IL-17 according to the treatment recommendations of the French Society of Rheumatology (SFR) patient not previously treated with biotherapy Aged ≥ 18 years Having given free and informed written consent Being affiliated to the center national security system social  For control Subject:  Healthy volunteers without diagnosis of spondyloarthritis or any other chronic disease. Aged ≥ 18 years Having given free and informed written consent Being affiliated with or benefiting from a social security scheme.  Exclusion Criteria:  Persons treated with antibiotics, probiotics, prebiotics or any other treatment that may disrupt the gut microbiota within one month before stool sampling. Association with another chronic pathology