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This article is from the WebMD News Archive
Bug May Cause Crohn's Disease
Sept. 16, 2004 -- A treatable infection may be the cause of Crohn's disease, new evidence shows.
The idea that a germ causes Crohn's disease isn't new. It goes back to 1913, when a surgeon noticed that the ulcer-ridden intestines of people with Crohn's disease look a lot like the intestines of animals with Johne's disease.
Scientists later learned a relative of the tuberculosis germ, Mycobacterium avium paratuberculosis, or MAP, causes Johne's disease. Does MAP cause Crohn's disease, too? That has been hard to prove. Why? MAP is incredibly hard to grow in the lab. It has been hard to show that Crohn's patients carry the living bug -- the first step in proving that MAP is the Crohn's culprit.
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That has changed. Saleh A Naser, PhD, associate professor of molecular biology and microbiology at the University of Central Florida, Orlando, developed a better way to culture MAP. Now he reports that he can grow living MAP from the blood of 50% of patients with Crohn's disease, 22% of people with ulcerative colitis -- and none from patients who don't have inflammatory bowel disease.
"We have strong evidence now that MAP is responsible for many cases of Crohn's disease -- maybe two-thirds of cases, we do not yet know," Naser tells WebMD. "We should be concerned that these bacteria are present in patients with Crohn's disease."
Naser and colleagues report their findings in the Sept. 18 issue of The Lancet.
The Proof in the Pudding -- Treatment
Simply showing that Crohn's patients are more likely to have MAP infection than healthy people doesn't prove MAP causes the illness, warns Warwick Selby, MD, clinical associate professor of gastroenterology at the University of Sydney in Australia.
"The Naser findings are interesting and provocative," Selby tells WebMD in an email interview. "However, as with all of the studies looking at MAP in Crohn's disease, it does not prove that MAP is the cause."
Selby's editorial appears alongside the Naser team's report in The Lancet.
MAP "does seem to be there," Selby says. But that might only mean that existing Crohn's disease damages the intestinal wall, and lets MAP and other bacteria out of the gut and into the bloodstream.
What would prove a connection? Selby would be convinced if Crohn's patients get better after taking MAP-killing drugs. Even though he's been skeptical about the MAP-Crohn's connection, he's leading a study in which 214 patients received two years of a potent anti-MAP drug combination.
"The Australian trial was specifically designed to use antibiotics that would be effective against MAP," Selby says. "We used clarithromycin [Biaxin], rifabutin [ Mycobutin], and clofazimine [Lamprene] for two years. All patients were initially treated with a course of [steroids] for 16 weeks as well and were randomized to antibiotics or placebo. After their two-year course of treatment they were then followed for one year off trial therapy."
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