The objective of this study is to constitute cohorts of IBD versus non-IBD patients to identify (a) new biomarker(s) of intestinal dysbiosis associated with inflammatory bowel disease, and develop a prototype for assaying such marker(s) in blood.

Inclusion Criteria:

General criteria:

• Male or female ≥ 18 years old
• Able to follow the instructions of the study
• Having signed an informed consent

Specific for Crohn cohort:

• A confirmed diagnosis of IBD
• Rectal or colonic or ileocolic involvement
• Patients with CD presenting inflammatory flare and disease extent in the colon or ileocolic region with:
• A clinical activity defined by an average of four or more instances of very soft or liquid stools daily or an abdominal pain score of 2 or more OR a CDAI (CD Activity Index) ≥ 220 OR a Harvey-Bradshaw Index > 8 OR a faecal calprotectin ≥ 250 µg/g And
• A endoscopic activity defined by a SES-CD (Simple Endoscopic Score for Crohn Disease) ≥ 6 or a CDEIS (CD Endoscopic Index score) ≥ 7
• Patients with UC presenting inflammatory flare with:

A clinical activity defined by a modified Mayo score ≥ 3 OR a Simple Clinical Colitis Activity Index ≥5 OR Patient Reported Outcome (PRO2) ≥ 4 with a subscore of rectal bleeding ≥1 OR a faecal calprotectin ≥ 250 µg/g AND An endoscopic activity defined by a Mayo endoscopic sub-score ≥ 2

Specific for Control cohort:

Patient with no colonic lesion(s) visible during the endoscopical examination (neither Crohn's nor other colitis nor cancer)

Exclusion Criteria:

General criteria:

• Commercial Pharmaceutical probiotic administration within the previous month
• Treatment with antibiotics (whatever the route of administration) within last 3 months
• Non-remission Cancer or in remission for less than 6 months
• Any contraindication to colonoscopy and/or biopsy, left to PI discretion
• Under guardianship or judiciable protection
• Pregnant or breastfeeding women
• Currently participating or having participated in the last 3 months to a clinical study with investigational medicine or food supplement

Specific for Crohn cohort:

• Crohn disease localized only in Ileum
• Inflammatory colon pathology other than Crohn's (infectious, drug-induced,…)