Study of Fecal Microbiota Transplantation (FMT) in Severe IBS Patients

The objective of this protocol is to evaluate the efficacy of fecal microbiota transplantation (FMT) using oral capsules containing frozen stools vs sham FMT on IBS severity score at 12 weeks in patients with severe irritable bowel syndrome refractory to conventional treatments.

Irritable bowel syndrome (IBS) is a chronic disease. It affects about 4.4 to 10 % of the French general population (according to Rome III or Rome IV definition) and is the most frequent functional bowel disorder in patients visiting general practitioners or gastroenterologists. The efficacy of treatments is often limited, in particular form the case severe of IBS (IBS-SSS\>300) which concerns at least 20 to 25% of patients and IBS can cause significant deterioration in quality of life.

In this context, microbiota could become a potential therapeutic target, and replacement of the abnormal fecal microbiota by an "healthy" one, especially in patients refractory to previous treatment and with severe symptoms, is a seducing new therapeutic strategy. The primary outcome is an improvement in the IBS-SSS score level at 12 weeks after taking a oral capsules of FMT in patients with severe IBS.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥ 18 years and \< 75 years
* IBS defined according to Rome IV definition (IBS-C, IBS-D or IBS-M)
* Severe disease (IBS-SSS \>300) and refractory to at least two previous treatment strategies:among the following : anti-spasmodic and/or laxatives (polyethylene glycol) or anti-diarrheal drug (loperamide) according to transit subtype for one month, antidepressants for 2 months, probiotics (ALFLOREX, SMEBIOCTA, PROBIOLOG FLORVIS) for 1 month, hypnosis for 5 hypnosis sessions in two months, Cognitive Behavioral Therapies for 2 months, colestyramine for IBS-D patients for 1 month, ondansetron for IBS-D patients and for 1 month, ebastine for 2 months, L-glutamine (5g x3/day, for 2 months, Gelsectan for one month, Biofeedback for 15 sessions in IBS-C (3 months), Low FODMAP diet for 1 month, gluten free diet for 1 month, standard dietary advice from the NICE (UK) for 1 month, increase in physical activity.
* Patient with health insurance (AME excepted)
* Informed written consent
* For women with childbearing potential, efficient contraception for the duration of the participation to the study

Exclusion Criteria:

* Other chronic gastrointestinal disease (celiac disease, inflammatory bowel disease)
* participants if there is a reason to suspect an alternative diagnosis to the IBS complaints
* Surgical intervention in the gastrointestinal region except for appendectomy, hernia repair, cholecystectomy and hemorroidectomy
* Treatment preceding FMT with: antibiotics, antifungic or probiotics treatment \< 4 weeks, or factors that may affect the composition of intestinal microbiota
* Abuse of alcohol or drugs
* Pregnancy or breastfeeding
* Participation in any other interventional study
* Patients under legal protection.
* Acute COVID-19 infection
* Presence of systemic disease, immune deficiency or treatment with immune-modulators
* Severe psychiatric disorder
* Participants who were assessed as likely to be noncompliant (ie, not adhering to the tasks they were to perform as participants)