Assessing the ecological role of yeasts in the human gut

The influence of gut microorganisms in health and disease is well documented, however, the role of yeasts has not been as widely studied as bacteria, despite associations with gastrointestinal disorders, such as Irritable Bowel Syndrome (IBS). For instance, Candida albicans is an opportunistic pathogen that has been linked to gastrointestinal symptoms.

Urine, stool and blood samples will be collected from 40 healthy controls, 40 IBS and 40 inflammatory bowel disease (IBD) patients for microbial and metabolic analysis using primarily flow cytometry-fluorescence in situ hybridisation (FC-FISH) and proton nuclear magnetic resonance (1H-NMR) spectroscopy, respectively. Calprotectin and anti-Saccharomyces cerevisiae antibodies (ASCA) levels will assess gastrointestinal inflammation. Statistical analysis will identify yeasts and their metabolites associated with the cohorts of interest.

Preliminary tests to assess the presence and functionality of yeasts in healthy and IBS faecal samples using in vitro batch culture fermentation highlighted significant metabolic differences between the phenotypes: Trimethylamine (TMA), short chain fatty acids (SCFA) and ethanol predominantly distinguished in the IBS metabolic profile, compared to gamma-amino-N-butyrate (GABA) in the healthy donor. The addition of C. albicans shifted the healthy phenotype to resemble the IBS donor, whereas nystatin shifted the IBS phenotype towards the healthy metabolic profile.

This study will further define the preliminary results that indicate the implication of yeasts in IBS pathogenesis. Understanding the role of yeasts within the healthy and diseased human gut is necessary to develop targeted therapies to improve patient’s quality of lives and relieve burdens on the economy and healthcare systems.