Recent research on Crohn’s disease has focused a lot on bacteria, but a new study has concluded that fungus is a factor in developing the inflammatory bowel disease.

Researchers from Case Western Reserve University School of Medicine led a study that evaluated patients with the disease, as well as their disease-free relatives.

They looked at both bacteria and fungi from fecal samples. In doing so, they found a strong interaction between two bacteria and one fungus in sick family members. That interaction was significantly higher compared to their healthy relatives.

The bacteria, Escherichia coli and Serratia marcescens, and one fungus, Candida tropicalis, work together when E. coli cells join with the fungal cells and S. marcescens to generate a biofilm.

That biofilm can trigger inflammation and Crohn’s symptoms. According to estimates, about 780,000 Americans have Crohn's disease.

“The fungus is found as a colonizer in our gut. Change in the microbiota caused by a number of factors, including use of antibiotics, allow this fungus to flourish and start causing problems,” Mahmoud A. Ghannoum, Ph.D., professor and director of the Center for Medical Mycology at Case Western Reserve and University Hospitals Case Medical Center, told Healthline.

Researchers also noted that beneficial bacteria were lower in Crohn’s patients than in their healthy relatives.

Doctors already knew that bacteria, along with genetic and dietary factors, had a role in causing the disease. People with the disease have a different immune response to certain bacteria in human intestines.

Read more: Study reveals specific gut bacteria involved in Crohn's disease »

The fungi factor

Fungi have already been linked to Crohn’s in humans, but this study is the first one to include S. marcescens in the Crohn’s-linked bacteriome, or network of bacteria.

The study was published in mBio. It included a total of 69 people from 13 families in France and Belgium.

"We already know that bacteria, in addition to genetic and dietary factors, play a major role in causing Crohn's disease," Ghannoum said in a statement.

Ghannoum hopes the findings lead to a new pathway in treating the disease that can improve the quality of life for people with Crohn’s.

"We have to be careful, though, and not solely attribute Crohn's disease to the bacterial and fungal makeups of our intestines,” he warned.

Ghannoum called for more research to “better understand the mechanism of how the fungus and the two bacteria cooperate to cause problems.”

“Once this is done we will be in a position to perform translational research aimed at developing new treatment options,” he added.

Read more: 14 things doctors really want you to know about Crohn's disease »

Consider fungi, too

Dr. Jean Frederic Colombel, a gastroenterologist at The Mount Sinai Hospital in New York, also participated in the research.

Although fungi have been known to be in our bodies, this study sheds more light on the role it can play.

“Maybe in the future if we want to treat patients with Crohn’s disease … we should think about not only their bacteria but also the fungi,” he told Healthline.

He does not want people to think this study confirms fungi as a cause of Crohn’s, but said it certainly is “a piece of the puzzle.”

Read more: How close are we to a cure for Crohn's disease? »