Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis is a pathogenic bacteria in the genus Mycobacteria. It is often abbreviated Map, M. paratuberculosis, or M. avium sub. paratuberculosis. The type strain is ATCC 19698 (equivalent to CIP 103963 or DSM 44133).

Pathophysiology
Map causes Johne's disease in cattle and other ruminants, and it has long been suspected as a causative agent in Crohn's disease in humans; this connection is controversial.

Recent studies have shown that Map present in milk can survive pasteurization, which has raised human health concerns due to the widespread nature of Map in modern dairy herds. Map is heat resistant and it is capable of sequestering itself inside white blood cells, which may contribute to its persistence in milk. It has also been reported to survive chlorination in municipal water supplies.

Even though Map is hardy, it is slow growing and fastidious, which means it is difficult to culture. Many negative studies for Map presence in living tissue, food, and water have used culture methods to determine whether the bacteria is present. Due to recent advances in our knowledge of the bacterium, some or all of these studies may need to be re-evaluated on the basis of culture methodology.

Map, like most mycobacteria, is difficult to treat. It is not susceptible to anti-tuberculosis drugs (which can generally kill Mycobacterium tuberculosis), but can only be treated with a combination of antibiotics such as Rifabutin and a macrolide such as Clarithromycin. Treatment regimes can last years.

Crohn's disease
MAP is recognized as a multi-host mycobacterial pathogen with a proven specific ability to initiate and maintain systemic infection and chronic inflammation of the intestine of a range of histopathological types in many animal species including primates.

On the assumption that Map is a causative agent in Crohn's, the Australian biotechnology company Giaconda is seeking to commercialise a combination of Rifabutin, clarithromycin and clofazimine as a potential drug therapy for Crohn's. As of April 2007, Giaconda received United States FDA IND approval for this medication, now called Myoconda.

Genome
The genome of Map strain K-10 was sequenced in 2005 and found to consist of a single circular chromosome of 4,829,781 base pairs.