The tubercle bacillus was first isolated and identified in 1882 by Robert Koch of Berlin, Germany. He inoculated guinea pigs and a variety of other mammals with infectious material from the lungs, intestines, scrofula, or brains of humans and cattle that died of TB to prove the same bacterium was responsible for the debilitating disease.
- Koch was able to grow the organism in Petri dishes containing potato agar (used to grow other organisms as well, such as Bacillus anthracis), then stain growth with methylene blue dye (developed by Paul Ehrlich, 1854-1915). Demonstrating his techniques during his presentation, Koch convinced the scientists of the German Physiological Society that all the animals inoculated subsequently exhibited clinical symptoms typically recognized as tuberculosis in humans.
- Criteria for determining basic epidemiology (for example, a "cause and effect" relationship between an organism and disease) was defined by his discovery, according to the steps laid out in the Henle-Koch postulates (published as the Koch postulates in 1890).
- Koch was then able to inhibit the growth of the bacilli by inoculating guinea pigs with a compound called “tuberculin” made from glycerol extracts of liquid tubercle bacilli cultures. Human treatment with tuberculin, however, was not successful. The resulting TB skin test (TST) or Mantoux test, which was a purified protein derivative of tuberculin, was later used as a diagnostic tool.
The TB bacillus has existed for thousands of years and was the first bacterial organism to be studied. It has been detected in DNA from ancient archaeological specimens as far back as the Iron Age (400-230 BC), in Andean mummies carbon-dated from 140-1200 AD, and from a Byzantine basilica. The unique characteristics of Mycobacterium tuberculosis (lipid-containing cell wall and large guanine-cytosine content) met the criteria for extended molecular study. Molecular methods used include polymerase chain reaction (PCR), high-performance liquid chromatography (HPLC), and spoligotyping (used to distinguish M. tuberculosis from M. bovis).
