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People with Crohn’s disease know the uncomfortable symptoms of the chronic condition all too well: diarrhea, abdominal pain, weight loss and fatigue, among others. But what doctors have not been able to tell the approximately 565,000 people in the U.S. with Crohn’s is why they’ve developed the inflammatory bowel condition in the first place.

Most experts suspect the condition is the result of the body’s immune system attacking healthy cells, mistakenly triggered by bacteria in the digestive tract. Now, a new study has identified a specific fungus and two bacteria they think play a key role in what leads some people to develop the disease.

“Among hundreds of bacterial and fungal species inhabiting the intestines, it is telling that the three we identified were so highly correlated in Crohn’s patients,” the study’s senior author Mahmoud A. Ghannoum, professor and director of the Center for Medical Mycology at Case Western Reserve and University Hospitals Cleveland Medical Center, said in a press release.

Research has previously identified that E. coli bacteria contribute to Crohn’s symptoms, but this is the first study to show the bacteria Serratia marcescens and the fungus Candida tropicalis are also involved.

“Crohn’s disease has other factors that impact it: Number one is genetics and number two is environmental factors, such as what people eat,” Ghannoum told HuffPost.

This study is distinct because it compared patients with Crohn’s disease to both healthy strangers and to their own family members who did not have Crohn’s. This is important because family members share genes, household environments and food, and researchers were able to further isolate what distinguishes the microbiomes of those with Crohn’s from those around them.

“This cuts a lot of the noise,” Ghannoume said.

The researchers analyzed fecal samples from 20 patients with Crohn’s and 28 healthy patients without Crohn’s from nine different families, as well as from 21 patients from four other families who did not have relatives with Crohn’s. They found high amounts of E. coli and Serratia marcescens and Candida tropicalis in the patients with Crohn’s ― significantly more so than in the family members without Crohn’s, as well as the individuals from families without a history of Crohn’s disease.

The researchers ran additional tests to see what happened when the two bacteria and the fungus interacted. Together the organisms produced a thin, slimy layer of microorganisms they say would be able to adhere to various organs in the body, including the intestines, which would likely cause the same type of inflammation known to affect people with Crohn’s.

Better treatment options are now on the table

Doctors currently use a variety of prescription drugs to help decrease inflammation caused by Crohn’s and to prevent symptoms from flaring up. But finding better treatment options is important because this type of chronic inflammation can lead to ulcers, fistulas and malnutrition, as well as severe pain and extreme fatigue.

In some cases, Crohn’s disease may require treatment with several surgeries. And living with Crohn’s can also increase risk of colon cancer and other health problems like anemia, osteoporosis and liver disease.

Thanks to this new finding, researchers have a big leg up on developing better treatments for the disease. One possibility is a probiotic with the right mix of good bacteria to control the bad bacteria that cause Crohn’s symptoms, Ghannoum said. He’s also hoping it will inform the development of drugs that prevent these two bacteria and specific fungus from working together in the first place.

“For patients, this is a very good start because we now understand more about the disease and how we can interfere with it,” Ghannoum said.

The first step is to conduct more studies to design therapies, then test them in animal models followed by clinical trials.

The bottom line for patients with Crohn’s: This is a big step toward designing more effective treatment options, but it’s still a pretty early one.

CLARIFICATION: Language has been updated to reflect that this is not the first study to suggest there are other microorganisms that may join E. coli in playing a role in Crohn’s disease.