Which bacterium causes tuberculosis, the infectious disease described by Robert Koch in 1882?

Mycobacterium tuberculosis causes tuberculosis, the infectious disease Robert Koch identified in 1882.

This species is a slender, rod-shaped bacterium with a distinctive waxy cell wall rich in mycolic acids. That wall helps it retain certain stains and contributes to its resistance to drying and some disinfectants. The organism most often enters the body through inhaled airborne droplets and initially infects the lungs.

Tuberculosis can remain latent, meaning the bacteria are present but not causing symptoms or spreading normally. Active disease may produce a persistent cough, fever, night sweats, fatigue, and weight loss. The bacterium can also spread beyond the lungs. Koch’s discovery provided decisive evidence that tuberculosis had a specific microbial cause, helping establish modern bacteriology. The disease is treatable, but therapy usually requires several antibiotics taken for many months because resistant bacterial populations can emerge when treatment is incomplete.