Robert Heinrich Hermann Koch

1843-1910

German Physician

Robert Koch was a key player in the field of bacteriology and, ultimately, hygiene and public health. His brilliant research uncovered the causes of anthrax, tuberculosis, and cholera, and led to the development of Koch's Postulates, a series of guidelines for the study of infectious diseases that are still used today.

Koch was born on December 11, 1843, in Clausthal, Germany, a mining town in the Harz Mountains. As a boy he loved natural science and collected rocks and plants and dreamed of being a great explorer. He studied at the University of Göttingen and, after interning in Hamburg, married and settled down to become a country doctor. Upon receiving a microscope for his 28th birthday, he began to study many things, including anthrax, a dreaded disease of warm-blooded animals, especially sheep. Isolating the organism from the blood, he grew the microbes in various media and discovered a stage where the anthrax bacilli have translucent coverings called spores. These spores could remain in the ground for years, then, when conditions were right, emerge into the rod-shaped organisms that cause the disease. Koch perfected the idea that these organisms could be cultured in pure form. In 1877 he published a work describing how thin smears of bacteria could be fixed on slides by gentle heat. His work was illustrated with excellent photomicrographs. He also invented the hanging drop, in which bacteria are suspended in a nutrient solution on a glass slide. Studying various wounds, Koch infected healthy animals with six different bacteria, demonstrating that a particular bacteria causes a specific disease.

Koch's scientific investigations earned him a position in Berlin in the German Health Office. He devised a new method of growing organisms on gelatin and then transferring pure colonies to test tubes of nutrient broth. Modifying the staining techniques developed by Paul Ehrlich (1854-1915), Koch worked to find the cause of tuberculosis. The bacillus that causes tuberculosis is very difficult to grow in pure culture, but Koch devised a technique of successive media and finally succeeded in growing them. On March 24, 1882, he announced to the Physiological Society of Berlin that he had isolated the bacillus that causes tuberculosis.

Koch devised a series of four basic principles, known as Koch's Postulates, by which a particular bacterium may be decisively linked to a specific disease. First, the bacterium in question must be present in every case of the infectious disease. Second, it must be possible to cultivate this bacterium in a pure culture. Third, a laboratory animal inoculated with the pure culture of the bacterium must develop the disease. Fourth, the bacterium must be recovered from the inoculated and infected test animal and reproduced again in a pure culture. If all of these criteria are met, it may be deduced that the suspect bacterium is indeed the cause of the disease.

When a serious cholera epidemic struck in 1883, Koch participated in a medical expedition to Egypt as a member of a German government commission. He soon isolated a small commashaped bacillus that he believed to be the cause. When the outbreak subsided he went to India, where cholera was endemic, and found the disease was transmitted by drinking water, food, and clothing.

Winning much acclaim and a large monetary prize, Koch returned to Germany to continue research as the director of the Institute of Hygiene. He concentrated again on tuberculosis and, in 1890, announced the discovery of tuberculin, which he hoped would be a cure. Tuberculin proved a failure as a cure for the disease, but is still used today as a diagnostic test for tuberculosis.

After his disappointment and embarrassment with tuberculin, Koch expanded his research into a variety of diseases, including leprosy, hinderpest, bubonic plague, surra, Texas fever, and malaria. He led expeditions in East and West Africa to study tropical diseases. In 1905 he received the Nobel Prize in medicine for his investigations and discoveries in relation to tuberculosis. He died on May 10, 1910, in Baden-Baden, Germany, of a heart attack.

EVELYN B. KELLY