Mycobacterium avium Complex (MAC)

November 2004     View PDF     En español

Cause

MAC is the term for two related bacteria: Mycobacterium avium and Mycobacterium intracellulare (MAI). These bacteria are found in water, dust, soil and bird droppings. They enter the body in food and water or sometimes through the lungs.

Most people usually have small numbers of these bacteria growing in their gut or lungs, but do not have any symptoms. This is because a weakened immune system allows the bacteria to attack the lining of the gut and multiply. From there, they can enter the blood and spread through the body, which is called disseminated infection.