Tuberculosis is caused by the Mycobacterium tuberculosis, which was discovered   in 1882 by the German bacteriologist Robert Koch (1841 – 1912). 

We owe the detectability by corresponding colouring to the Dermatologist Albert Neisser (1855 – 1916) from Bresslau.

The M. tuberculosis is gram-positive and acid-resistant, resistant do dehydration and heat. In the microscopic picture, it appears as a rod of 2  µm - 4 µm in length and bears a strong resemblance to the Mucobacterium leprae.

The material for the microscopic examination of the pathogen is obtained from body fluids and tissue biopsies after flouorchrome colouring or Ziehl-Neelsen colouring. The detection of the Tuberculosis bacteria only succeeds at germ counts 10`-10`pro ml Sputum. In case of a negative result, Tuberculosis cannot be excluded. The microscopic examination is a routine and an indispensable part of Tuberculosis diagnostics.

(Braveny,I, Maschmeyer,G.TUberculosis in infectious diseases)

The germ culture of the pathogen is indispensable, liquid cultures shorten the period of examination.