Louis Pasteur Germ Theory

Louis Pasteur's germ theory of disease changed the course of medical history. The understanding, prevention, and treatment of diseases were revolutionised. What did Pasteur discover, and how did he affect modern medicine? Let's find out!

Louis Pasteur Germ Theory of Disease

Before Louis Pasteur and his germ theory of disease, scientists broadly believed that disease was caused by non-living organisms, for example, dust, or dirt. This belief led to ideas such as the miasma theory.

The miasma theory was disproved by scientist Robert Koch with his discovery of the microorganism bacillus anthrax in 1876, but it wasn't the only explanation for diseases that needed de-bunking! During the 18^th century, the theory of the four humours also explained the cause of disease.

The theory of the four humours was discredited and ultimately disproven by William Harvey through his experimentations on blood circulation and body temperature during the 16^th century. It was in 1861 that Louis Pasteur discovered the true origin of disease with his germ theory.

Louis Pasteur Timeline

Louis Pasteur was born in Dole, France, in 1822. Louis Pasteur was a microbiologist, scientist, and medical physician who changed the course of medical history through his discoveries of vaccination through weakened bacteria, microbial fermentation, and pasteurisation.

Fig. 2 - Louis Pasteur

The road towards Louis Pasteur's germ theory development was one rife with scientific experimentation. Here is a timeline outlining his progress.

Louis Pasteur Germ Theory Experiments

During Louis Pasteur's lifetime, the concept of an immune system or bacteria and microbiology did not exist, certainly not in the form we know it today. Pathogens are too small to view without a very powerful microscope, and since these were not available at the time that Pasteur popularised the germ theory, no one knew they existed. Thus, he battled a lot of pushback and was very under-appreciated in his time. However, Pasteur's perseverance led to the discovery of the different components of the Germ Theory.

Fig. 3 - Artwork called Cholera in Paris created in 1865

The overview below describes pathogens, Pasteur's key discovery of Germ Theory.

• A specific group of microorganisms, commonly referred to as pathogens, can lead to or cause disease.

• Pathogens cause disease when they enter into a living organism such as a human or animal and multiply and reproduce.

• Pathogens are not just bacteria but include other pathogens such as fungi and viruses.

Pasteur's experiments were extremely influential to science as his subjects of discovery varied from germs, diseases, old bacteria, the cholera vaccine, anthrax, rabies, and more!

Louis Pasteur Germ Theory Development

Louis Pasteur and his early investigations and discoveries set up the foundations for many advancements in medicine. His research around anthrax and cholera led to his discovery of weakening the microbes that caused disease, ultimately creating the concept of vaccine-making. By helping people understand just how diseases were spread, consequent scientific experiments were more efficient.

Pasteur's developments were popularised during the 19^th century and even led to a new field of science: microbiology.

Developments in 19^th-Century Medicine

It was also believed that life could just evolve from spontaneous generation, which meant that life evolved from non-living matter and did not have any relation to other existing creatures. This meant fermentation, which is the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, and putrification was believed to be caused by spontaneous generation.

Putrification

The decomposition or breakdown of a substance.

Although there was some talk about the germ theory of medicine before Louis Pasteur, it was very unpopular and widely discredited. Furthermore, there was little scientific evidence that this was the case at the time because there was no scientific way to see germs in that period. Thus, germ theory remained a very unpopular and unresearched theory of medicine before the 19^th century.

The 19^th century, however, brought about a revolution in medicine. The 19^th century saw medical practitioners incorporate scientific experimentation and investigation methods into their practice. Medicine was now beginning to become a field of science. Consequently, many doctors, surgeons, dentists, and scientists in the 19^th century used experimentation to guide their treatments.

John Hunter, who is considered the father of surgery, was among the first practitioners to integrate scientific inquiry into medical practice. Edward Jenner was greatly inspired by this and used his scientific experiments later to develop a smallpox vaccine. Though Jenner was in England, his discovery greatly influenced Louis Pasteur in France which prompted him to develop other vaccines based on germ theory.Fig. 4 - John HunterWith the advancements made by Jenner, Pasteur, and Koch, the miasma theory could not compete with the now widely accepted and proven germ theory by the end of the 19^th century.

Louis Pasteur Germ Theory Impacts

So, how did Pasteur's discoveries change modern medicine and public understanding?

The impact of Louis Pasteur's germ theory were many, for instance, it helped develop a true understanding of why so many diseases were prevalent and remained prevalent during the 17^th and 18^th centuries, pushing medicine into modernity. But, what immediate results can be seen in changes to public health?

Public health in Industrial Britain was impacted by Pasteurs discoveries. By the end of the 19^th century, the miasma theory of medicine and Humoral theory had largely been abandoned. The 1848 Public Health Act is a demonstration of how Pasteur affected British legislation and understanding of science.

The 1848 Public Health Act ultimately started the movement for the improvement of Britain's public health administration. The Act meant that several things were now essential. Every public health authority had to have or do the following:

• A sanitary inspector.
• Medical officer.
• Confirm laws on housing, water, and food were being upheld.
• Towns had street lighting and pavements.

To begin with, the Board of Health created by the 1848 Public Health Act had limited influence, money, or power. However, Pasteur and other medical scientists and their discoveries helped to justify the need for good public health, improving public health in Industrial Britain dramatically.

Fig. 5 - Member of the U.S. Army receiving the third in a series of six inoculations against anthrax in 1998

Louis Pasteur Germ Theory Importance

Louis Pasteur's germ theory importance will never be forgotten as his discovery enabled him to become the father of immunology and preventative disease. Here is an overview of the importance of Pasteur and Germ Theory.

• Louis Pasteur revolutionised immunology. Although Edward Jenner had created the very first vaccine, it was not until Pasteur that it was understood that vaccination methods could be extended to a wide range of diseases.
• Pasteur disproved many of the widely accepted theories of medicine, allowing for effective treatment to be made as people now knew the cause of various diseases.
• Disproving spontaneous generation allowed for pasteurisation and food preservation methods to be devised.
• Pasteur and his contemporaries helped fight diseases such as cholera, anthrax, and rabies in Industrial Britain.
• Pasteur treated 350 people for rabies in 1886, and only one of these patients got rabies.²
• Pasteur changed how scientific experimentation was completed. The scientific method (An empirical method of gaining knowledge that began in the 17^th century which key concepts include observation and scepticism) is highly influenced by him.
• Later developments in modern medicine and public health came with Florence Nightingale and hospital conditions, Joseph Lister and antiseptics, the 1875 Public Health Act, and Robert Koch and bacteria. Koch's work was directly influenced by Pasteur as he used Pasteur's work to support his own.