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Robert Koch


The ubiquitous 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 horrendous and debilitating disease. Furthermore, Koch was able to grow the organism in Petri dishes containing potato agar (used to grow other organisms as well, such as Bacillus anthrasis), then stain them with methylene blue dye, developed by Paul Ehrlich (1854-1915). Demonstrating novel laboratory techniques along with 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’s work took another revolutionary step when he was able to inhibit 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. It was later globally recognized as a diagnostic tool, the TB skin test (TST) or the Mantoux test, which was a purified protein derivative of tuberculin.
The TB bacillus has existed throughout all historical time periods 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) easily 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, predominant in both wild and domestic animals).