For the first time, researchers have identified a fungus to be a key factor in the development of Crohn's disease (CD) in humans. The fungus also was found working together with two kinds of bacteria to produce a "biofilm" in the intestines, leading to inflammation and the symptoms associated with CD. The study “Bacteriome and Mycobiome Interactions Underscore Microbial Dysbiosis in Familial Crohn’s Disease”, was published in mBio. "We already know that bacteria, in addition to genetic and dietary factors, play a major role in causing Crohn's disease," Mahmoud A Ghannoum, PhD, professor and the study's senior author, said in a news release. "Essentially, patients with Crohn's have abnormal immune responses to these bacteria, which inhabit the intestines of all people,” he said. While most researchers have focused their investigations on these bacteria, few have examined the role of fungus, which exists throughout the body of all humans. Researchers recently identified there are between 9 and 23 fungal species just in our mouths. Ghannoum and his team investigated the presence of fungus in the intestines of CD patients, and also its interaction with bacteria. They analyzed fecal samples of 20 CD patients and 28 of their healthy relatives. As a comparator group, 21 healthy persons from families with no history of CD were used and all participants were living in northern France-Belgium. Researchers found the presence of one fungus (Candida tropicalis) to be higher in the CD patients compared to their healthy relatives. This is the first time any fungus has been linked to CD in humans, although it has been found in mice with the disease. Also, two bacteria (Escherichia coli and Serratia marcescens) were present in the patients to a higher degree.