Subject: biography, biology
German bacteriologist who, with Louis Pasteur, is generally considered to be one of the two founders of modern bacteriology. He developed techniques for culturing, staining, and observing micro-organisms and discovered the causative pathogens of several diseases - including tuberculosis, for which discovery he was awarded the 1905 Nobel Prize for Physiology or Medicine.
Koch was born on 11 December 1843 in Klausthal, Germany, one of 13 children of a mining official. He studied natural sciences and then medicine at Göttingen University, where he was taught by Friedrich Wöhler and Friedrich Henle (1809-1885), obtaining his medical degree in 1866. After serving as an army surgeon (on the Prussian side) in the Franco-Prussian War, Koch became in 1872 district medical officer in Wollstein where, despite having few research facilities, he began important investigations into anthrax. For a brief period in 1879 he was town medical officer in Breslau, before being appointed to the Imperial Health Office in Berlin to advise on hygiene and public health. By 1881 his work was becoming well known and he was invited to speak at the Seventh International Medical Congress in London. In 1882 he announced to the Berlin Physiological Society his discovery of the bacillus that causes tuberculosis, and in the following year, while investigating an outbreak of cholera in the Nile delta, he identified the cholera bacillus. In 1885 he was appointed professor of hygiene at Berlin University and director of the Institute of Hygiene. The Tenth International Medical Congress was held in Berlin in 1890 and Koch was persuaded to announce the discovery of an anti-tuberculosis vaccine; this proved to be premature, however, as the vaccine was ineffective. In 1891 he was appointed director of the newly established Institute for Infectious Diseases, but he resigned his directorship in 1904 and spent much of the rest of his life advising foreign countries on ways to combat various diseases. Koch died on 27 May 1910 in Baden-Baden, Germany.
Koch started his bacteriological research in the 1870s with the gift of a microscope from his wife, and built up a primitive laboratory in part of his consulting room. Out of necessity Koch devised simple and original methods for growing and examining bacteria. For three years he worked on anthrax in his spare time, developing techniques for culturing the bacteria in cattle blood and in aqueous humour from the eye. He trapped a small smear of blood from an anthrax victim with a drop of aqueous humour between two microscope slides and observed the bacteria grow and divide under the microscope, finding that the bacteria were short-lived but that they formed spores that were resistant to desiccation. He then inoculated animals with the spores and found that they developed anthrax, thus proving that the spores remained infective; this was the first time a bacterium cultured outside a living organism had been shown to cause disease. Koch published his findings, but only after Pasteur's demonstration of an anthrax vaccine in 1882 were Koch's findings accepted.
Koch experimented with various dyes and found some that stain bacteria and make them more visible under the microscope. He also devised an ingenious method of separating a mixture of bacteria, which 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.
On joining the Imperial Health Office in 1879, Koch was provided with two assistants and for the first time had adequate laboratory facilities. Here he developed the technique of culturing bacteria on gelatin. Using this technique Koch and his assistants isolated several micro-organisms and showed that they cause disease. They also investigated the effects of various disinfectants on different bacteria and showed that steam is more effective than dry heat in killing bacteria, a discovery that revolutionized hospital operating-theatre practice.
Koch then set out to discover the causative agent of tuberculosis, a common and frequently fatal disease at that time. Initially he was unable to find any micro-organisms that might cause the disease, but after developing a special staining technique he identified the bacterium responsible and, despite the difficulties caused by the bacterium's small size and slow rate of growth, managed to culture it in 1882.
In 1883 Koch went to the Nile delta to investigate a cholera epidemic. Finding bacteria in the intestinal walls of dead cholera victims and the same bacteria in the excreta of cholera patients, he succeeded in isolating the causative organism. On a later visit to Calcutta (now Kolkata), where cholera was rife, he found similar bacteria in excreta and in supplies of drinking water. On returning to Berlin he advised regular checks on the water supply, made recommendations regarding sewage disposal, and organized courses in the recognition of cholera. And when the disease occurred in Hamburg in 1892, he recommended that the victims should be isolated, all excretory matter should be disinfected and that a special check should be made on the water supply.
Koch made several other important contributions. As a result of his investigations into a bubonic plague epidemic in Calcutta in 1897, he showed that rats are vectors of the disease (although there is no evidence that he knew that the rat flea was the actual vector). He also demonstrated that sleeping sickness is transmitted by the tsetse fly. His isolation of many disease-causing organisms eventually led to the development of vaccines and to the realization of the importance of the public health measures he recommended. Furthermore, many bacteriologists received their training as his assistants, including Shibasaburo Kitasato, and the Nobel prizewinners Emil von Behring and Paul Ehrlich. Perhaps most importantly, however, Koch formulated a systematic method for bacteriological research, including various rules - still observed today - for identifying pathogens. According to these rules (called Koch's postulates), the suspected pathogen must be identified in all of the cases examined; the pathogen must then be cultured through several generations; these later generations must be capable of causing the disease in a healthy animal; and the newly infected animal must yield the same pathogen as that found in the original victim.
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