Inclusion Criteria:  healthy volunteer of both sexes between the ages of 18 and 65 years old included subject considered healthy after a thorough general examination (interrogation, physical examination) subject with normal transit with usually one molded saddle per day BMI between 18.5 and 35 kg / m² included  Exclusion Criteria:  Subject living in an institution Known immunosuppression (HIV, concomitant immunosuppressive therapy, chemotherapy, long-term corticosteroids regardless of the dose> 2 weeks in the last 6 months) Chronic gastrointestinal illness (Chronic Hemorrhagic Recto-colitis, Crohn's Disease) Any digestive resection except appendectomy and resection of polyps Subject with a history (s) of bacteremia Subject protected by law under guardianship or curator-ship Pregnant or lactating woman Subject deprived of liberty under judicial duress Lack of affiliation to a social security scheme Patient on State Medical Aid Absence of signed consent before entering the study