Mycobacterium vaccae

Mycobacterium vaccae are a species of the Mycobacterium family of bacteria that lives naturally in soil. Its name is derived from the Latin word, vacca (cow) as the first described strain was isolated from cow dung in Austria.

Scientists believe the bacteria may work as an antidepressant because they stimulate the generation of serotonin in the brain.

M. vaccae is related to the tuberculosis bacterium. Early trials indicated that exposure to M. vaccae would relieve tuberculosis symptoms. However, a 2002 review found no benefit from immunotherapy with M. vaccae in people with tuberculosis.