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Crohn's Disease Health Center

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Gut Bacteria May Play Role in Crohn's Disease

Study found more harmful strains, fewer helpful ones in people with the inflammatory bowel condition


Six types of harmful bacteria were elevated in patients with Crohn's compared to those without inflammation, while levels of four varieties of bacteria that are thought to be beneficial to digestion and health were lower in those patients. The differences were even more pronounced in patients who had the most severe symptoms.

"We now know which organisms should be studied more closely," Gevers said.

About 10 percent of patients in the study were taking antibiotics -- not for Crohn's, but for other reasons when the tissue samples were taken. Antibiotic treatment seemed to aggravate the bacterial imbalances seen in the study even further, suggesting that doctors may want to steer clear of these drugs, which are commonly prescribed for Crohn's.

"We should probably be wary of giving antibiotics in the early stages of Crohn's disease, because we may not be accomplishing what we want to accomplish," said Dr. Balfour Sartor, a distinguished professor of microbiology and immunology at the University of North Carolina School of Medicine in Chapel Hill.

"Because most of the antibiotics that are used in Crohn's disease are broad-spectrum antibiotics, you're basically hitting both the beneficial and detrimental bacteria in the process, and maybe that's really not a good idea," said Sartor, who is also the chief medical advisor for the Crohn's and Colitis Foundation, which helped fund the study. He was not involved in the research.

It's impossible to say whether the bacteria were present in response to the inflammation or if they may have caused it.

Sartor thinks it may be some of both. He said inflammation undoubtedly changes the bacterial environment. But some studies in mice have offered evidence that the bacteria may be the root of the illness. Those studies have shown that transferring gut bacteria from mice with Crohn's-like inflammation to healthy, germ-free animals can make healthy mice ill.

"There's pretty good evidence that some of these bacteria have causative and preventative activities, rather than just being secondary to the inflammatory response," Sartor said.

Now that doctors have a bacterial signature for the disease, Sartor thinks there may soon be a time when they can take a quick tissue sample and quickly know if they are looking at Crohn's.

Right now, he said, it takes an average of three years for doctors to diagnose someone who's having symptoms. And most patients get two incorrect diagnoses before doctors zero in on the true cause of their problems.

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