Ulcerative Colitis (UC) is a chronic Inflammatory Bowel Disease characterized by chronic inflammation of the colon. Composition of gut microbiota of UC patients is abnormal (dysbiosis).

Ulcerative Colitis patients have an increased risk of Clostridioides difficile infection (CDI) and CDI complications (colectomy, death, recurrence). The reason for this increased risk in IBD patients is not fully understood. The decrease in the proportion of secondary bile acids, induced by microbiota dysbiosis in patients with UC could favor C. difficile infection.

The main objective of the study is to describe the composition of bile acids (primary and secondary) in children followed for UC during relapse with or without CDI and to compare it to children with UC in remission and healthy controls. The composition of fecal microbiota will be also describe to correlate dysbiosis and bile acid abnormalities. And finally some fecal biomarkers will be study : short chain fatty acids, metabolic pathway of Tryptophan, and fecal Calprotectin.

Ulcerative Colitis (UC) is a chronic inflammatory bowel disease (IBD) characterized by chronic inflammation of the colon. Clinical symptoms include bloody diarrhea associated with abdominal pain, fecal incontinence, urgency, and tenesmus. Approximately 15-20% of patients develop UC during childhood or adolescence, with a sustained worldwide rise of the incidence of IBD, particularly pediatric forms. While there are many similarities between adult- and childhood-onset UC, pediatric-onset UC appears to be more severe and extensive with more rapid spread of the disease leading to high morbidity, more severe acute flares and more frequent use of intravenous corticosteroids. To date, there is no medical treatment that can cure the disease but only treatments that shorten the duration of relapses or prevent them.

An imbalance in the composition of the intestinal microbiota named "dysbiosis" has been demonstrated in IBD. This dysbiosis is characterized by a strong instability of the microbiota over time, and a reduction of diversity and particularly a reduction in bacteria belonging to the Firmicutes and Bacteroidetes phyla with an increase in Proteobacteria and Actinobacteria. More recently, a UC-specific dysbiosis has been described including a decrease in butyrate-producing bacteria, in particular Faecalibacterium prausnitzii, and Roseburia hominis.

It has also been shown that if adult patients with UC in flare-up and remission have similar total fecal bile acids, they have a lower proportion of fecal secondary acids compared to healthy control subjects.

Patients with UC have an increased risk of Clostridioides difficile infection (CDI) and complications from the CDI (coletomy, deaths) as well as a higher risk of CDI recurrences. Clostridioides difficile is a strict anaerobic bacteria, which represents the main cause of post-antibiotic diarrhea.

The hypothesis of the project is that gut microbiota dysbiosis in patients with UC alters the bile acid profile and metabolite profile and could promote C difficile infection in these patients without any other risk factors such as antibiotics. To confirm this hypothesis, the investigating team proposes to study the microbiota, bile acid profiles and microbial metabolites in the stools of 40 pediatric-onset UC patients with a flare-up of their disease with (n=20) or without (n=20) a concomitant CDI and to compare them to healthy children (n=20) and UC children with clinical remission (n=20). Bile acids will be determined by high performance liquid chromatography coupled with tandem mass spectrometry detection, the short chain fatty acids and tryptophan derivatives derived from TRP and AGCC will be determined by GC-MS or LC-MS and the microbiota by the MiSeq technique.

The investigating team hopes to identify bile acid profiles predisposing for CDI and to correlate them with microbiota abnormalities. This will allow to better understand the factors associated with CDI but also to identify biomarkers of infection and maybe protective bacterial strains. In the long term, the investigating team hopes to find new therapeutic perspectives by providing bacteria of interest to transform bile acids and to protect against Clostridioides difficile.

For everyone :

Inclusion Criteria:

• Pediatric patients (<18 years) consultant or hospitalized in the Gastroenterology department of Necker-Enfants Malades Hospital.
• Information and consent of parents and the patient

Exclusion Criteria:

• Patient who received antibiotic or antifungal treatment in the 4 weeks prior to inclusion.
• Patients colonized by C. difficile.
• Pregnant or breastfeeding young girl.
• Refusal of the protocol by parents or patient.

For group 1: Patients with active UC

Inclusion criteria:

• Patient with UC, whatever the extent, except isolated proctitis (<5 cm), diagnosed for more than 3 months according to the usual clinical, biological and endoscopic criteria.
• UC in flare defined by a PUCAI score of between 35 and 65.

Non-inclusion criteria:

• Patient with IBD unclassified or Crohn's disease.
• Patient with isolated proctitis (<5 cm).
• Colectomized patients.
• Patients with sclerosing cholangitis associated with their UC or liver disease.

Group 2: Patients in UC remission

Inclusion criteria:

• Patient with UC, whatever the extent, except isolated proctitis (<5 cm), diagnosed for more than 3 months according to the usual clinical, biological and endoscopic criteria.
• UC in remission defined by a PUCAI score <10.

Non-inclusion criteria:

• Patient with IBD unclassified or Crohn's disease.
• Patient with isolated proctitis (<5 cm).
• Colectomized patients.
• Patients with sclerosing cholangitis associated with their UC or liver disease.

Group 3: Healthy control subjects

Inclusion criteria:

- Patients hospitalized for an endoscopic assessment to control for abdominal pain, gastroesophageal reflux or polyposis.

Non-inclusion criteria:

• Patient with chronic liver disease.
• Patient with chronic digestive disease (celiac disease, IBD, chronic chronic).

Pediatric patients consulting or hospitalized in the Gastroenterology department of Necker-Enfants Malades Hospital, with ulcerative colitis (UC) in flare-up with and without Clostridioides difficile infection (CDI), patients UC in remission and healthy controls.