The primary objective of the study aims to compare the biodiversity of intestinal microbiota between spondylarthritis (SPA) or rheumatoid arthritis (RA) patients and healthy volunteers, by microbiota DNA sequencing in order to further and respond the prior results, which suggested that there is a specific dysbiosis for each of the 2 diseases. A comparative analysis will allow to identify the biomarkers of the specific bacteria.

As secondary objectives, the study aims to analyse the relation between different clinical parameters such as age, gender, duration of the disease, or the nature of ongoing treatment, and the the composition of intestinal microbiota, and identify dysbiosis of bacteria, which will be specific functional signatures of intestinal microbiota in SPA and/or RA. Analyse the relation between metabolome of faecale and plasma and the composition of intestinal microbiota.

This study will be performed in the rheumatology department in Ambroise Paré hospital of APHP group in France.

Inclusion Criteria:

Patients:

• Patient ⩾ 18 years;
• Diagnosed as spondyloarthritis (SpA) according ASAS classification, or rheumatoid polyarthritis according ACR/EULAR;
• Affiliated to a social security scheme;
• Have signed the written informed consent form.

Healthy control subjects:

• Adult women and men;
• Subjet free of chronic pathology;
• Affiliated to a social security scheme;
• Have signed the written informed consent form.

Exclusion Criteria:

Patients:

• Patients unable to understand the proposed study and/or sign a informed consent form;
• Pregnant women or breast feeding women;
• Patient ⩾ 18 years;
• Patients under guardianship or curatorship;
• Have taken antibiotic 1 month prior to inclusion or digestive coloscopy 6 months prior inclusion;
• Presenting acute or chronic severe pathology may likely to interfere with the interpret of outcome;
• Foreign patients under french AME scheme;
• Patients had have participated in the prior study Microbiart.

Healthy control subjects:

• Subjects unable to understand the proposed study and/or sign a informed consent form;
• Pregnant women or breast feeding women;
• Subjects < 18 years;
• Subjects under guardianship or curatorship;
• 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;
• Subjects had have participated in the prior study Microbiart.

• Adult patient diagnosed spondyloarthritis or rheumatoid polyarthritis;
• Healthy adult subjects free of chronic pathology.