Role of Gut Microbiota in the Pathophysiology of Aseptic Abscesses

Inclusion Criteria:

• For cases: adult patients meeting the diagnostic criteria for aseptic abscesssyndrome described by André et al:

• Deep abscesses on radiological examination with neutrophilic features proven bypathological analysis of a surgical specimen or biopsy when performed

• Negative blood cultures, negative serological tests for bacteria, including alwaysYersinia enterocolitica, and, during surgery or aspiration, sterile pus (withstandard cultures, BAAR and fungal tests) Failure of antibiotic therapy, whenprescribed, after at least 2 weeks for conventional antibiotic therapy and at least 3 months for anti-tuberculosis treatment

• Rapid clinical improvement the day after the prescription of corticosteroids (atleast 1/2 mg/kg prednisone or equivalent) followed by radiological improvement after 1 month of corticosteroids, sometimes in association with immunosuppressivetreatments.

For controls: adult person living in the same environment as the case to which it is matched. Adult person living in the same household or near the patient.

For cases and controls:

• Ability to provide informed consent.

• Membership in the Social Security system.

Exclusion Criteria:

• Pregnant women. Incapable patients Patients deprived of liberty Antibiotic therapyadministered within 6 weeks prior to inclusion.