Role of Bile Acids and Microbiota in Clostridioides Difficile Infection in Ulcerative Colitis

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.