Robert Koch announced the discovery of the tuberculosis bacterium in 1882. He presented his findings to the Physiological Society in Berlin on 24 March, identifying the rod-shaped organism now called Mycobacterium tuberculosis.
Koch’s discovery challenged the widespread belief that tuberculosis was inherited or caused by general weakness. Using staining techniques and microscopic examination, he found the bacillus in tuberculous tissue and demonstrated that it could be cultivated and reproduced. His work provided powerful evidence that a specific microorganism caused a specific disease.
The announcement became a landmark in the germ theory of disease. Koch later published a fuller account and connected the evidence to principles now associated with Koch’s postulates. The date, 24 March, is commemorated internationally as World Tuberculosis Day.
A common mix-up is confusing the announcement date with the later publication of his expanded report, which appeared in 1884. Another is confusing the tuberculosis bacterium with the anthrax bacterium, which Koch had identified earlier, in 1876.