Definition of Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis: (MAP) A bacterium that causes Johne's disease, a form of chronic inflammatory bowel disease (IBD) in cattle and other species, including primates. Because Johne's disease is in some ways quite similar to Crohn's disease in humans, MAP has been suspected of playing a role in Crohn's disease, too. This matter has been the subject of lively debate in the medical literature.

DNA from MAP has been detected in the blood of patients with IBD and in controls without the disease. The viable organism (MAP) has been cultured from blood only in patients with Crohn's disease or ulcerative colitis, another form of IBD. MAP has also been cultured from intestinal tissue and breast milk in people with Crohn's disease. However, the evidence that MAP is one of the causes of Crohn's disease is still not conclusive.

MAP is a member of the Mycobacterium avium complex (MAC) but it differs significantly from other forms of MAC in its DNA. (It has 14 to 18 copies of IS900 and a single cassette of DNA involved in the biosynthesis of surface carbohydrate.)