Louis Pasteur, the father of modern medicine

” Science transcends frontiers…”


Louis Pasteur was born on December 27, 1822 in Dole, in the region of Jura, France. His discovery that most infectious diseases are caused by germs, known as the “germ theory of disease”, is one of the most important in medical history. His work became the foundation for the science of microbiology, and a cornerstone of modern medicine.

Pasteur’s phenomenal contributions to microbiology and medicine can be summarized as follows. First, he championed changes in hospital practices to minimize the spread of disease by microbes. Second, he discovered that weakened forms of a microbe could be used as an immunization against more virulent forms of the microbe. Third, Pasteur found that rabies was transmitted by agents so small they could not be seen under a microscope, thus revealing the world of viruses. As a result he developed techniques to vaccinate dogs against rabies, and to treat humans bitten by rabid dogs. And fourth, Pasteur developed “pasteurization”, a process by which harmful microbes in perishable food products are destroyed using heat, without destroying the food.

His Works

Each discovery in the body of Pasteur’s work represents a link in an uninterrupted chain, beginning with molecular asymmetry and ending with his rabies prophylaxis, by way of his research in fermentation, silkworm, wine and beer diseases, asepsis and vaccines.

From Crystallography to Molecular Asymmetry

In 1847 at the age of 26, Pasteur did his first work on molecular asymmetry, bringing together the principles of crystallography, chemistry and optics. He formulated a fundamental law: asymmetry differentiates the organic world from the mineral world. In other words, asymmetric molecules are always the product of life forces. His work became the basis of a new science — stereochemistry.

Research on Fermentation and Spontaneous Generation

At the request of a distiller named Bigo from the north of France, Pasteur began to examine why alcohol becomes contaminated with undesirable substances during fermentation. He soon demonstrated that each sort of fermentation is linked to the existence of a specific microorganism or ferment — a living being that one can study by cultivation in an appropriate, sterile medium. This insight is the basis of microbiology.

Pasteur delivered the fatal blow to the doctrine of spontaneous generation, the theory held for 20 centuries that life could arise spontaneously in organic materials. He also developed a germ theory. At the same time, he discovered the existence of life without oxygen: “Fermentation is the consequence of life without air”. The discovery of anaerobic life paved the way for the study of germs that cause septicemia and gangrene, among other infections. Thanks to Pasteur, it became possible to devise techniques to kill microbes and to control contamination.

Technique of “Pasteurization”

Emperor Napoleon III asked Pasteur to investigate the diseases afflicting wine which were causing considerable economic losses to the wine industry. Pasteur went to a vineyard in Arbois in 1864 to study this problem. He demonstrated that wine diseases are caused by microorganisms that can be killed by heating the wine to 55deg.C for several minutes. Applied to beer and milk, this process, called “pasteurization”, soon came into use throughout the world.

Research on Infectious Diseases Afflicting Man and Animal

In 1865, Pasteur began to study the silkworm diseases that were crippling the silk industry in France. He discovered the infectious agents and revealed the manner in which these agents are transmitted–by contagion and hereditary principle — and how to prevent them. Elaborating on his study of fermentation, he could now confirm that each disease is caused by a specific microbe and that these microbes are foreign elements. With this knowledge, Pasteur was able to establish the basic rules of sterilization or asepsis. Preventing contagion and infection, his method of sterilization revolutionized surgery and obstetrics.

From 1877 to 1887, Pasteur employed these fundamentals of microbiology in the battle against infectious diseases. He went on to discover three bacteria responsible for human illnesses : staphylococcus, streptococcus and pneumococcus.

Treatment and Prevention of Rabies

Louis Pasteur discovered the method for the attenuation of virulent microorganisms that is the basis of vaccination. He developed vaccines against chicken cholera, anthrax and swine erysipelas. After mastering his method of vaccination, he applied this concept to rabies. On July 6, 1885, Pasteur tested his pioneering rabies treatment on man for the first time : the young Joseph Meister was saved.

The Creation of the Pasteur Institute

On March 1, 1886, Pasteur presented the results of his rabies treatment to the Academy of Sciences and called for the creation of a rabies vaccine center. An extensive, international public drive for funds financed the construction of the Pasteur Institute, a private, state-approved institute recognized by the President of France, Jules Grévy, in 1887 and inaugurated by his successor Sadi Carnot in 1888. In accordance with Pasteur’s wishes, the Institute was founded as a clinic for rabies treatment, a research center for infectious disease and a teaching center.

The 66-year-old scientist went on to dedicate the last seven years of his life to the Institute that still bears his name. During this period, Pasteur also came to know the joys of fame and was honored throughout the world with prestigious decorations.

His work was continued and amplified throughout the world by his disciples, the Pasteuriens.

A Man of Freedom and Rigor

Pasteur’s work is not simply the sum of his discoveries. It also represents the revolution of scientific methodology. Pasteur superimposed two indisputable rules of modern research: the freedom of creative imagination necessarily subjected to rigorous experimentation. He would teach his disciples :
“Do not put forward anything that you cannot prove by experimentation”
Louis Pasteur was a humanist, always working towards the improvement of the human condition. He was a free man who never hesitated to take issue with the prevailing yet false ideas of his time.

He ascribed particular importance to the spread of knowledge and the applications of research. In the scientist’s lifetime, Pasteurien theory and method were put into use well beyond the borders of France.

Fully aware of the international importance of his work, Pasteur’s disciples dispersed themselves wherever their assistance was needed. In 1891, the first Foreign Institut Pasteur was founded in Saigon (today Ho Chi Minh City, Vietnam) launching what was to become a vast international network of Instituts Pasteur.

Because he changed the world forever, his homeland and the world have long considered him a benefactor of humanity.

The Progress of Humanity

“I beseech you to take interest in these sacred domains so expressively called laboratories. Ask that there be more and that they be adorned for these are the temples of the future, wealth and well-being. It is here that humanity will grow, strengthen and improve. Here, humanity will learn to read progress and individual harmony in the works of nature, while humanity’s own works are all too often those of barbarism, fanaticism and destruction.” — Louis Pasteur

Source: Hyperlab, Science and Technology Department, Embassy of France in Canada.

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This post is also available in : French