What are acid-fast bacillus (AFB) tests?

Acid-fast bacillus (AFB) is a type of bacteria that causes tuberculosis and other types of mycobacterial infections, such as leprosy (Hansen’s disease). AFB tests are usually ordered for people with symptoms of active tuberculosis, commonly known as TB. TB is a serious bacterial infection caused by Mycobacterium tuberculosis. It mainly affects the lungs. But can also affect other parts of the body, including the brain, spine, and kidneys. TB bacteria spread from person to person through coughing or sneezing.