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Introduction

Robert Koch is generally considered to be one of the two founders of modern bacteriology. The other is, of course, Louis Pasteur.

The French parasitologist Casimir-Joseph Davaine inspired by the work of the French microbiologist Louis Pasteur had showed, in 1863, that anthrax in sheep was due to the presence of rod-like bodies in the blood. However, the natural history of the disease was not complete. This required the painstaking observational work of Koch.

Investigation of Anthrax

Finding that dried spores remained viable for years explained the recurrence of the disease in pastures long unused for grazing. When conditions were right the spores could develop into the rod-shaped bacilli of anthrax. On the invitation of an eminent botanist, Ferdinand Cohn, the anthrax life cycle was demonstrated at Breslau in 1876. However, it was only after Pasteur's demonstration of an anthrax vaccine in 1882 were Koch's findings accepted.

Research Methods & 'Koch's Postulates

As well as experimenting with various dyes  that stain bacteria and make them more visible under the microscope, he also devised an ingenious method of separating a mixture of bacteria. This involved inoculating an animal with the bacteria and passing the resulting infection from one animal to another until, at the end of the experimental chain, only one type of bacterium remained. Using this method he identified the bacteria responsible for several: disorders, including septicaemia.

To obtain pure cultures outside the body, Koch mixed the organisms in melted gelatine. After solidification of the gelatine and growth of the organisms, portions of pure colonies were placed into separate tubes of broth or other media. This work offered the early formulation of what to was become known as Koch's Postulates. These were formalised in 1882 and stated that to prove an organism was the cause of any disease it was necessary to demonstrate:

• That the organism could be discoverable in every instance of the disease;

• That, extracted from the body, the germ could be produced in a pure culture, maintainable over several microbial generations.

• That the disease could be reproduced in experimental animals through a pure culture removed by numerous generations from the organisms initially isolated;

• That the organism could he retrieved from the inoculated animal and cultured anew.

Although some pathogenic entities, notably viruses, had to be accepted without meeting all the conditions most conditions were able to be fulfilled. The applicability and thinking behind these rigorous postulates, boosted the dogma of specific aetiology - the idea that a disease has a specific causative agent. The implication was that once the agent has been isolated, it will be possible to control the disease.

Koch announced that he had isolated, and grown, the tubercle bacillus to the Physiological Society of Berlin on 24 Mach 1882. He believed this to be the cause of all forms of tuberculosis.

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Cholera in Egypt

Koch & his wife at time of his Nobel Prize

The outbreak of cholera in Egypt, and the danger of it finding its way to Europe, caused Koch, as a member of the German government commission, to go to Egypt to investigate the disease. Although he was frustrated by the cessation of the epidemic, he was able to study the disease long enough to suspect a particular comma-shaped bacillus. Whilst there, however he was able to discover the cause of amebic dysentery and the bacilli of two varieties of Egyptian conjunctivitis. He was able to complete his work on cholera by proceeding to India. He discovered the cholera organism and its transmission via drinking water, food and clothing.

When he returned to Berlin Koch advised regular checks on the water supplies and  recommendations regarding sewage disposal. He also organised courses in the recognition of cholera. He also resumed his studies of tuberculosis.

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Tuberculin

Koch investigated the effect an injection of dead bacilli would have on a person who subsequently received a dose of living ones. He concluded that the local reaction produced might provide the means by which the disease could not only be diagnosed but, in the early stages, perhaps even cured. He used as the active agent a sterile liquid produced from cultures of the bacillus. As the liquid (tuberculin, 1890) proved disappointing as a curative agent its importance as a means of detecting a present or past tubercular state was not immediately recognised.

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Other Investigations

After the seeming disappointment of tuberculin, he became occupied from 1891-99 with investigations into many other diseases of humans and animals. The result of Koch investigations into a bubonic plague epidemic in Calcutta in 1897 showed that rats were vectors of the disease. He also demonstrated that sleeping sickness is transmitted by the tsetse fly. Other studies by Koch included leprosy, surra, rinderpest, Texas fever and malaria.

Although malaria was still a mystery, Koch had nearly satisfied himself that the disease was transmitted by mosquitoes when the British bacteriologist, Ronald Ross, published his findings in 1898 pointing to the same conclusions.

Koch formulated systematic method for biological research (Koch's Postulates, given above) are still observed to this day.

In 1905 Koch won the Nobel Prize for Physiology or Medicine "For his investigation and discoveries in relation to tuberculosis".