While most researchers focus their investigations on these bacteria, few have examined the role of fungi, which are also present in everyone's intestines," Ghannoum added.In the study, the researchers analyzed the microorganisms found in fecal samples from 20 people with Crohn's, 28 of their relatives without the disease, and 21 people without Crohn's who were not related to the 20 people with Crohn's or their relatives. All of the participants were residents of Belgium or northern France.The researchers found that the people with Crohn's disease had significantly higher levels of two types of bacteria, called Escherichia coli and Serratia marcescens, and one fungus, called Candida tropicalis, compared with their healthy relatives and the other people in the study who did not have the disease, according to the study, published Sept. 20 in the journal mBio.Although previous research in mice has suggested that this fungus may be involved in Crohn's, this is the first time it has been linked to the condition in people, the researchers said.Moreover, when the researchers examined these bacteria and fungus, they found that the three microorganisms worked together to form a so-called biofilm — a thin, sticky layer of microorganisms — that attaches itself to a portion of the gut. This biofilm could trigger the inflammation that causes the symptoms of Crohn's disease, the researchers said. [5 Ways Gut Bacteria Affect Your Health]