A Bacterial Cause of Crohns Disease?

A study in this weeks issue of The Lancet suggests that Crohns disease may be caused by Mycobacterium avium subspecies paratuberculosis (MAP), the same bacterium that causes a similar intestinal disorder (known as Paratuberculosis or Johnes disease) in cattle, sheep, and goats.


Crohns disease, a form of inflammatory bowel disease (IBD) with at least one million diagnosed cases worldwide, resembles some aspects of tuberculosis, leprosy, and paratuberculosis. The role of MAP, first identified from a person with Crohns disease 20 years ago, remains controversial. Saleh A Naser of the University of Central Florida, and colleagues used microbiological and molecular biology techniques to investigate the presence of MAP in the blood of 28 individuals with Crohns disease, nine with ulcerative colitis, and 15 without inflammatory bowel disease.


The live bacterium (viable MAP) was cultured from the blood of 14 (50 percent) patients with Crohns disease, two (22 percent) with ulcerative colitis, and none of the people who did not have IBD.


Naser comments: This is the first study designed to culture MAP from human blood. We detected viable MAP in peripheral blood in half of patients with Crohns disease and none in those people who did not have IBD. The two ulcerative colitis patients with viable MAP may represent misdiagnosis or possible co-infection cases. Detection of Viable MAP in the blood of Crohns disease patients suggests that MAP infection in this IBD may be systemic. In addition to the fact that the outcome of our study contributes to the evidence that MAP might be a cause of Crohns disease, it is of great interest to address the epidemiologic source of MAP in these patients. A multi-center, larger-scale investigation is urgently needed.


In an accompanying commentary, Warwick S. Selby, of the Royal Prince Alfred Hospital/University in Sydney, Australia, concludes, This report by Naser et al may still fall short of proving that MAP is one of the causes of Crohn's disease but as with similar studies it raises many important questions. The findings now need to be replicated in other laboratories. Whatever ones view, MAP cannot continue to be ignored in Crohn's disease. Funding bodies, laboratory and clinical researchers must clarify with some urgency, once and for all, whether this organism is important in Crohn's disease or is merely a curious bystander. This is not just for the patients but also in the interest of public health.


Source: The Lancet