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Louis Pasteur (1822–1895), a French chemist and bacteriologist, was a pioneer in the fields of bacteriology and preventive medicine. He had already established an international reputation as a chemist and won the Rumford Medal of the British Royal Society for his work on the structure of crystals when he made his first foray into bacteriology in 1854. Having recently been appointed a professor of chemistry in Lille, Pasteur was invited to solve a problem in the fermentation of beer that affected its taste and rendered it undrinkable. He showed that this was caused by bacteria that could be killed by heat. In this way he invented the process for heat treatment to kill harmful bacteria, first applied to the making of beer, then to milk. This process has been known ever since as pasteurization.

He next turned his attention to two diseases of silkworms, showing these to be due to microparasites and demonstrating how these diseases could be prevented. Soon after this he suffered a stroke from which he was not expected to recover. Defying this prognosis, he went on to study and solve other bacteriological problems in both industry and animal husbandry. He showed that chicken cholera could be prevented by inoculating chickens with an attenuated vaccine and in 1881 he demonstrated that a similar attenuated vaccine could be used to control anthrax, which was then a serious threat to livestock, and occasionally to humans.

In 1880, Pasteur had begun experiments on rabies, seeking a vaccine to control this disease, which without treatment has a 100 percent death rate. Following the success of the anthrax vaccine he believed that an attenuated rabies vaccine could be made. The only way to test this vaccine would be on a human who had been bitten by a rabid dog, and this he did in July 1885. His patient was a boy, Joseph Meister. The vaccine worked, Joseph Meister survived, and Pasteur became not just a national but an international celebrity.

Pasteur made many other important contributions to microbiology and continued to work until near his death, despite the gloomy prognosis he had been given after his stroke more than a quarter of a century earlier. Pasteur's antirabies regimen consisted of multiple injections of rabies vaccine into the skin of the abdomen. This sequence of multiple (and painful) injections was used for many years without modification to prevent the onset of rabies in anyone who had been bitten by a rabid animal. No one was brave enough to try an experiment to determine whether a less protracted and painful regimen would be as effective. Only in the 1980s did the development of genetically engineered vaccines lead to a simpler way to prevent rabies. Pasteur's name lives on in the microbiological research institute in Paris that bears his name, the Institut Pasteur, and its branches in former French colonies in Africa and Asia.

JOHN M. LAST

(SEE ALSO: Immunizations; Rabies)