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LOUIS PASTEUR (1822-95)

 

 

 

 

 

 

Louis Pasteur with tribute paid to him as a benefactor of humanity.

  The Welcome Institute, London.

 

WHO WAS LOUIS PASTEUR?

Louis Pasteur was a world renowned French chemist and biologist. He was born on December 27 1822 in the town of Dole in Eastern France. Pasteur's parents were peasants, his father was a tanner by trade. He spent the early days of his life in the small town of Arbois where he attended school and where it seems that Pasteur did not do very well, preferring instead to go fishing. His headmaster, however, spotted potential in Pasteur and encouraged him to go to Paris to study. So, aged fifteen Pasteur set off for Paris hoping to study for his entrance exams. Unfortunately, the young Pasteur was so homesick that his father had to travel to Paris to bring him home. He then continued to study locally at Besancon, until he decided to try again in Paris. This time he succeeded and went on to study at the Ecole Normale Superieure. Curiously, although the young Pasteur worked hard during his student days he was not considered to be exceptional in any way at chemistry.

In 1847 Pasteur was awarded his doctorate and then took up a post as assistant to one of his teachers. He spent several years teaching and carrying out research at Dijon and Strasbourg and in 1854 moved to the University of Lille where he became professor of chemistry. Here he continued the work on fermentation he had already started at Strasbourg. By 1857 Pasteur had become world famous and took up a post at the Ecole Normale Superieure in Paris. In 1863 he became dean of the new science faculty at Lille University. While there, he started evening classes for workers. In 1867 a laboratory was established for his discovery of the rabies vaccine, using public funds. It became known as the Pasteur Institute and was headed by Pasteur until his death in 1895.


SO WHAT DID PASTEUR ACTUALLY DO?

 

Pasteur founded the science of microbiology and proved that most infectious diseases are caused by micro-organisms. This became known as the "germ theory" of disease. He was the inventor of the process of pasteurisation and also developed vaccines for several diseases including rabies. The discovery of the vaccine for rabies led to the founding of the Pasteur Institute in Paris in 1888.


SO HOW DID PASTEUR MAKE HIS DISCOVERIES?

When he was only twenty-six years old Pasteur solved a problem that had been puzzling the great chemists of the day. He found that when light was passed through tartaric acid - this was found in wine dregs, it produced a strange effect. Pasteur proved that this was because the acid is actually not one acid but a mixture of different acids. This find impressed the scientists of influence and established Pasteur's reputation.

While at the University of Strasbourg he became interested in fermentation and this interest continued when he moved to the University of Lille. The faculty had been established partly to serve as a means of applying science to the problems of the industries of the region, especially the production of alcoholic drinks. This work in fermentation enabled Pasteur to identify that the changes brought about when beer or wine ferments, milk turns sour or meat decays, occur when special micro-organisms are present.

As a result of these findings Pasteur was asked to help the local breweries where the beer had turned bad. The souring of wine and beer was a major economic problem in France. Pasteur looked at some droplets of bad beer through a microscope and observed that the beer contained small rod shaped bacteria, instead of round yeast cells. Although micro-organisms are essential in fermentation they must be the right ones. This was a major discovery. Pasteur made brewing a more scientific procedure and showed brewers how to culture the right organisms for good beer. He also demonstrated to the wine industry that if wine is gently heated to sixty degrees celsius for a short time, the growth of harmful bacteria is prevented and the wine does not go sour in bottles or barrels.

Pasteur then extended this to other problems such as the souring of milk. He proposed heating the milk to a high temperature and pressure before bottling. The process is now in widespread use and is called pasteurisation.


WHAT OTHER DISCOVERIES DID PASTEUR MAKE?

By 1857 Pasteur had become world famous and took up an appointment as director of scientific studies at the Ecole Normale in Paris. He was asked to help to investigate a serious disease that was ruining the silk industry in southern France. The disease known as pebrine attacked the silk worms. The signs of the disease were that the eggs did not hatch or the worms would die before making their silk cocoons. It had now reached epidemic proportions and even disease free worms brought in from Spain and Italy had been contaminated. By 1864 there were no uncontaminated eggs left, except for those brought in from Japan.

Pasteur observed through his microscope that the diseased caterpillars and eggs all contained tiny organisms. He identified these as disease producing organisms. He managed to obtain some healthy worms and he divided them into two lots. He fed one lot with mulberry leaves smeared with the remains of diseased worms and fed the others with mulberry leaves smeared with the remains of healthy worms. Pasteur was able to show that the worms fed on diseased smeared leaves got the disease, whereas those fed on uncontaminated leaves remained disease free. He then worked with the silk industry to devise a simple way of keeping silk worms under healthy conditions and therefore disease free.

Not only had Pasteur rescued the French silk industry but he had established the connection between bacteria and disease. The connection had not been fully understood before.

This was a major discovery.

Pasteur's work on the link between bacteria and disease came to the attention of the famous Edinburgh surgeon Lord Lister. Lord Lister was concerned with the number of people who died after having operations in hospital. To combat infection, Lister introduced disinfectant sprays during operations, these prevented bacteria from entering a wound. He also introduced the use of dressings soaked in carbolic acid and strict hygiene rules to combat sepsis. The sterile methods introduced by Lister, drastically reduced the number of hospital deaths.

In France at that time many cattle suffered from anthrax, a serious disease from which many of them died. Pasteur made a careful study of anthrax and noticed that some cows developed the disease more severely than others. So he decided to inject two cows with a strong dose of the anthrax bacteria, fully expecting them to die. To Pasteur's amazement neither of them developed the disease. Later, he found that both animals had already suffered from anthrax. Could they be immune to it? Could they be protected in some other way? Pasteur believed that if it were possible to give an animal a mild attack, this might be sufficient to prevent it from getting the disease later on.

Eventually, after many experiments Pasteur succeeded in producing a weakened and harmless culture of anthrax bacteria. He inoculated cattle and sheep with this giving them a mild form from which they recovered. When these animals were put with others who had a severe form they remained unaffected. They were immune.

Pasteur worked throughout the rest of his life on the various causes of diseases and how these could be prevented by vaccination.


PASTEUR AND RABIES

Pasteur is particularly renowned for his work on the vaccine for rabies, a highly contagious infection which attacks the central nervous system. It enters the body through the bite of an infected animal or through infected saliva entering an existing wound. After experimenting with the saliva of animals suffering from the disease, Pasteur concluded that the disease rests in the central nervous system of the body. When an extract from the spinal column of an rabid dog was injected into healthy animals symptoms of rabies were produced. By studying the tissues of infected animals- rabbits, Pasteur was able to produce an attenuated form of the virus. This could be used for inoculation.

On July 6 1885, Pasteur tested his pioneering rabies vaccine on man for the first time. He saved the life of a young man called Joseph Meister who had been bitten by a rabid dog. Pasteur was urged to treat him with his new method. The treatment lasted 10 days and at the end he recovered and remained healthy. Since then thousands have been saved by this treatment.

On March 1886, Pasteur was invited to present his results to the Academy of Sciences and in 1888 went on to found the Pasteur Institute in Paris. This was a pioneering clinic for the study of infectious diseases, the treatment of rabies and a centre for teaching. Pasteur directed the Institute personally until he died. The Pasteur Institute is still one of the most important centres in the world.

Pasteur became a national hero and was honoured in many ways. He died at Saint-Cloud on 28 September 1895 and was given a state funeral at the Cathedral of Notre Dame and his body placed in a permanent crypt at the Pasteur Institute.

Modifications of the Pasteur method are still used in rabies therapy today. The traditional vaccine contains inactivated rabies virus grown in duck eggs. A newer vaccine which contains virus prepared from human cells grown in the laboratory is safer and requires a shorter course of injections.