High M. Avium Subspecies Prevalence Found in Crohn's Gut Tissue Samples

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"He concludes: "This controversy has persisted far too long and needs to be expeditiously resolved."

http://www.medscape.com/viewarticle/507613

High M. Avium Subspecies Prevalence Found in Crohn's Gut Tissue Samples

Reuters Health Information 2005. © 2005 Reuters Ltd.

NEW YORK (Reuters Health) Jun 30 - A new study has identified a high prevalence of Mycobacterium avium subspecies paratuberculosis (MAP) in gut tissues from Crohn's disease patients.

While MAP infection has been proposed as a potential cause of Crohn's, the organism is difficult to detect by both conventional microbiology techniques and PCR, and studies of MAP prevalence in Crohn's have yielded conflicting results, Dr. J. Schmidt of the University of Heidelberg in Germany and colleagues write.

The researchers looked for the MAP DNA sequence IS900 in 100 samples of gut tissue from Crohn's patients, 100 from patients with ulcerative colitis (UC), and 100 from patients with no inflammatory bowel disease using specialized tissue sample processing and a nested IS900-specific PCR test. The findings are published in the July issue of Gut.

Fifty-two percent of the samples from CD patients contained IS900, compared to 2% of those from UC patients and 5% from controls. IS900 was found in 47% of small bowel samples from the CD patients, and 61% of colon samples. The researchers found no significant association between CD phenotype and MAP detection rates, although their was a weak association between disease duration of longer than 15 years and decreased MAP detection as well as corticosteroid treatment at the time the sample was taken.

Dr. Schmidt and his team suggest the variability of past findings may in part be due to the use of standard DNA extraction in some studies, "which rather facilitates the detection of the vegetative form of MAP but may have led to non-detection of the lysis-resistant paucibacillary form which is postulated to reside in the intestines of CD patients."

The findings, the researchers conclude, suggest MAP could be a target for mitigating disease in Crohn's patients.

In an editorial accompanying the study, Dr. R. Balfour Sartor writes that well designed studies are "urgently needed" to settle the question of whether MAP infection itself causes CD, which the editorialist considers "unlikely," or if the relationship between MAP and CD is similar to that of Helicobacter pylori with peptic ulcers and gastric cancer, "where host genetics and microbial virulence factors determine immune responses that mediate clinical disease in a small minority of patients exposed to a widespread infectious agent."

He concludes: "This controversy has persisted far too long and needs to be expeditiously resolved."

Gut 2005;54::944-949.