Recent medical research has focused on links between the fungal composition of human microbiota and chronic inflammatory bowel disease. A research team in Cleveland, USA, has identified one specific fungus as a key factor in the development of Crohn's disease. Previously identified in mice with the disease, the scientists linked this fungus and two bacteria in microbiota to inflammation and Crohn's disease in humans.

"We already know that bacteria, in addition to genetic and dietary factors, play a major role in causing Crohn's disease," said the study's senior and corresponding author, Mahmoud A Ghannoum, PhD, professor and director of the Center for Medical Mycology at Case Western Reserve and University Hospitals Cleveland Medical Center.

The specialist and his team took things one step further by investigating the role of fungi present in the gut. These fungi exist alongside bacteria, some of which can trigger abnormal immune responses in patients with Crohn's disease.

After analyzing fecal samples from patients with and without Crohn's disease, the scientists identified strong fungal-bacterial interactions in the patients suffering from Crohn's. The bacteria "Escherichia coli" and "Serratia marcescens" and the "Candida tropicalis" fungus were present at higher levels in Crohn's patients than in healthy patients.

The researchers suggest that these two types of bacteria and the fungus interact in the gut, working together to create a biofilm, which adheres to a part of the intestines and can prompt inflammation and Crohn's disease symptoms (diarrhea, constipation, weight loss, fatigue).

"Candida tropicalis" was previously found in mice with the disease. However, this is the first time that the bacteria "S. marcescens" has been linked to the disease.

In addition, the researchers found lower levels of beneficial bacteria in Crohn's patients.

Recent French research, published in the journal Gut, also established a link between fungi and yeast composition in the microbiota and chronic inflammatory bowel disease (IBD). The team, led by Dr Harry Sokol at Saint-Antoine hospital in Paris, found that in 235 patients with IBD has an increased Basidiomycota / Ascomycota ratio, a higher proportion of Candida albicans and a lower presence of Saccharomyces cerevisiae than 38 healthy patients.

The findings could give rise to new treatments for Crohn's disease, notably probiotics, which could reduce the level of inflammation-causing fungi or enrich the microbiota with protective fungi. However, genetic and environmental factors also play a role in Crohn's disease.

The study is published in the journal mBio.