What is the name of the organism that causes tuberculosis?

The organism that causes tuberculosis is the bacterium Mycobacterium tuberculosis, often abbreviated M. tuberculosis or M. tb. It is also known historically as Koch’s bacillus.

German physician Robert Koch identified the tuberculosis bacterium in 1882, providing decisive evidence that the disease was caused by a specific infectious organism. M. tuberculosis most often affects the lungs, although it can spread to other organs. Transmission generally occurs through airborne particles released when a person with active pulmonary tuberculosis coughs, speaks, or sneezes; it is not normally spread by sharing food, touching surfaces, or shaking hands.

The bacterium has a distinctive cell wall rich in waxy mycolic acids. This coating helps it resist ordinary staining and contributes to its ability to persist inside immune cells called macrophages. Because of this feature, laboratories commonly use acid-fast stains when examining suspected samples. Another frequent confusion is Mycobacterium leprae, which causes leprosy, not tuberculosis.