Bacteria tied to Crohn's disease

Bacteria may be behind Crohn's disease, an inflammatory bowel disease, researchers say.

For decades, scientists have suspected Crohn's is caused by bacteria that cause a similar intestinal disorder in cattle, sheep and goats, but there was little evidence.

Until now, microbiologists have been unable to culture bacteria from the blood of patients with the disease.

Common symptoms of Crohn's disease include abdominal pain, diarrhea, weight loss and fever. Inflamed parts of the intestine may need to be surgically removed.

The bacteria, called Mycobacterium avium subspecies paratuberculosis or MAP, are a relative of the tuberculosis germ.

Molecular biology and microbiology Prof. Saleh Naser of the University of Central Florida tested for MAP in 28 individuals with Crohn's disease, nine with ulcerative colitis, and 15 controls without inflammatory bowel disease.

Living bacteria were found in half the patients with Crohn's disease, 22 per cent of those with ulcerative colitis but in none of the healthy people.

The presence of bacteria in the blood suggests the infection may be systemic, meaning it starts in the intestine and then enters other organs, Naser said.

"These data contribute to the evidence that MAP might be a cause of Crohn's disease," the researchers wrote in the Sept. 18 issue of the medical journal The Lancet.

The study does not prove if MAP causes Crohn's disease or is "merely a curious bystander," said Prof. Warwick Selby of Royal Prince Alfred Hospital in Newtown, Australia.

In a commentary accompanying the study, Selby said the results raise important questions.

"The findings now need to be replicated in other laboratories," Selby wrote. "Whatever one's view, MAP cannot continue to be ignored in Crohn's disease."

Researchers still need to sort out a chicken-and-egg scenario. Does MAP cause the disease, or does damage from Crohn's disease allow the bacteria out of the intestine?