The French chemist and microbiologist Louis Pasteur made an immeasurable impact in the fields of hygiene and modern medicine, with his groundbreaking discoveries and pioneering research fundamentally transforming the understanding of disease causation and leading to significant advancements in public health.
Pasteur’s work spanned multiple areas, laying the foundation for the germ theory of disease, sterilisation techniques, the development of vaccination, and the concept of pasteurisation – revolutionising the understanding and practice of medicine and leaving a lasting legacy that continues to shape modern medicine and human health.
Here we explore more about the impact Pasteur and his work have had.
Early life and scientific background
Louis Pasteur was born on 27 December 1822, in Dole, in eastern France. From an early age, he demonstrated a keen interest in chemistry and pursued his education in the field at the École Normale Supérieure in Paris. He excelled in his studies, earning his master’s degree in 1845 and his doctorate in 1847, and became an assistant professor of chemistry there in 1848.
Pasteur’s initial research focused on crystals and isomerism, but changed focus to the world of microbiology when he was appointed as the dean of the Faculty of Sciences at the University of Lille in 1854.
Fermentation and spontaneous generation
Pasteur’s exploration into microbiology began with research into fermentation. He observed that fermentation was not a spontaneous chemical process but rather the result of the action of living microorganisms, specifically yeast cells. This insight contradicted the prevailing theory of spontaneous generation, which posited that life could arise spontaneously from non-living matter.
Louis Pasteur in 1857
In 1857 Pasteur returned to the École Normale as Director of Scientific Studies, and by 1859, Pasteur’s experiments definitively disproved the theory of spontaneous generation, paving the way for a new understanding of the role of microorganisms in biological processes.
Germ Theory of disease
One of Pasteur’s most significant contributions to modern medicine was the development of the germ theory of disease. Building on his work in fermentation, he expanded his research to investigate the causes of infectious diseases in humans and animals, including a devastating blight that had befallen the silkworms that were the basis for France’s then-important silk industry.
At the time, prevailing beliefs attributed diseases to “miasma” or “bad air,” and there was little understanding of the role of microorganisms in causing illnesses. Through rigorous and meticulous experimentation and observations, Pasteur conclusively demonstrated that microorganisms, such as bacteria and viruses, were responsible for causing various diseases. This groundbreaking revelation fundamentally changed the way diseases were understood and treated, shifting the focus from the symptoms to the underlying causes.
In 1865, Pasteur presented his germ theory to the French Academy of Sciences. His theory revolutionised the understanding of disease causation, laying the groundwork for the development of modern infectious disease control and the importance of sanitation and hygiene in disease prevention.
Louis Pasteur experimenting on bacteria, c1870
Vaccination
Louis Pasteur, one of the biggest figures in immunology, was investigating chicken cholera when he discovered attenuation, the process of weakening a strain of bacteria over time. He accidentally successfully vaccinated chickens against chicken cholera in 1879, sparking a whole new dimension of thought in immunology.
Building upon Edward Jenner’s earlier work with cowpox and smallpox, one of Pasteur’s most celebrated achievements came in 1885 when he successfully developed the first rabies vaccine.
After a boy named Joseph Meister had been bitten by a rabid dog and was brought to Pasteur, Pasteur took a daring approach, vaccinating him with a weakened strain of the rabies virus that had been cultivated in rabbits. To the astonishment of the medical community, the boy survived without contracting the disease.
This groundbreaking success led to widespread recognition of Pasteur’s work, solidifying his reputation as a leading figure in the field of immunology. Pasteur’s rabies vaccine (and his development of the first anthrax vaccine) also became a turning point in preventive medicine. His success in producing weakened strains of these pathogens inspired further research into vaccination, opening up new possibilities for controlling, preventing and eradicating deadly infectious diseases.
Vaccination has since become a cornerstone of public health, preventing countless illnesses and saving millions of lives worldwide.
Listen NowPasteurisation
In the mid-19th century, the spoilage of wine and beer due to microbial contamination was a widespread problem. Pasteur’s earlier work on fermentation and ‘diseases’ of wine in his laboratory led him to realise that these were caused by unwanted microorganisms, that could be destroyed by heating wine to a temperature between 60° and 100°C.
Aware of people’s natural reluctance in embracing new technology, Pasteur often carried out public demonstrations to convince sceptics. In one such experiment, a batch of wine was heated and then sent to sea along with some unheated wine on a vessel named Jean Bart as an experiment. On its return 10 months later, the heated wine was fine whereas the unheated wine tasted almost acidic.
Pasteur also personally supervised the French Navy frigate La Sibylle to carry a complete cargo of heated wine on a circumnavigation of the world that arrived back ‘unspoilt’. This helped enable the protection of the French wine and beer industries (pasteurised wine is rare today). Pasteur’s experiments demonstrated that heating liquids, such as wine and milk, to a specific temperature could kill harmful microorganisms and bacteria while preserving the taste, quality and nutritional value of the product.
In 1864, Pasteur presented his findings to the French Academy of Sciences. His simple yet effective process of pasteurisation – which he patented in 1865 and is named after him – revolutionised food and beverage preservation, reducing the risk of food-borne illnesses and ensuring a safer food supply.
The process was later extended to all sorts of other spoilable substances, including milk in 1886 by German chemist, Franz von Soxhlet – indeed pasteurisation was used for most commercial milk by the late 1920s. Today, pasteurisation remains a standard practice in the food industry, ensuring the safety and longevity of various perishable products.
Contributions to surgical practices and aseptic techniques
Pasteur’s germ theory also had profound implications for advancing surgical practices.
Prior to Pasteur’s work, surgical procedures were often performed in unsterilised environments, leading to high rates of infections and post-operative complications. Understanding that microorganisms could cause wound infections and transmit disease, Pasteur advocated for antiseptic practices to reduce surgical complications.
British surgeon Joseph Lister was greatly inspired by Pasteur’s work, introducing aseptic techniques into surgical procedures. Lister’s use of antiseptics to sterilise surgical instruments and wound dressings significantly reduced infection rates and improved patient outcomes, transforming the field of surgery and promoting a major shift in surgical practices.
Pasteur’s influence on surgical techniques and infection control has saved innumerable lives and laid the groundwork for modern aseptic surgical procedures.
Portrait of Louis Pasteur, by Albert Edelfelt (1854–1905) (cropped)
Image Credit: Wikimedia Commons / Musée d'Orsay / Public Domain
Legacy and impact
Despite his lack of a medical degree, Pasteur’s work was internationally recognised, and his influence was far-reaching. He received numerous accolades during his lifetime, including his election to the French Academy of Sciences and being awarded the Copley Medal from the Royal Society of London.
Pasteur personally initiated The Pasteur Institute in Paris, established in 1888, which became a centre of scientific excellence and research in microbiology and immunology. It remains a prominent research institution, continuing Pasteur’s mission of advancing medical knowledge and finding solutions to public health challenges.
Whilst Pasteur is said to have downplayed assistance from colleagues and not reported his findings in an appropriate or timely manner, his accomplishments have been summarised by many via his famous maxim, “chance favours only the prepared mind”.
Nevertheless, beyond his scientific achievements, Pasteur’s dedication to rigorous scientific methods, rigorous experimentation and intellectual curiosity has inspired generations of scientists to push the boundaries of medical research. His emphasis on evidence-based medicine has become a cornerstone of modern medical practice, ensuring that treatments and interventions are based on solid scientific evidence.
