Germ theory & public health
What is Germ Theory?
The word 'germ' is the commonly used term for microorganisms, such as bacteria, viruses, fungi, and protozoa. The discovery of germs revolutionized our understanding of how diseases spread. The idea of germ theory evolved gradually in the 19th century.
The microscope
The invention of the microscope nearly five hundred years ago, transformed our understanding of the world around us. Credited with the discovery of microorganisms using rudimentary microscopes, Robert Hooke described mold structures in 1665, while Antoni van Leeuwenhoek unveiled bacteria in 1676. Their pioneering observations laid the foundation for the discipline of microbiology, which later resolved longstanding scientific mysteries about spontaneous generation and infectious diseases.
Antoni van Leeuwenhoek
Antoni van Leeuwenhoek (1632-1723), a cloth merchant from Belgium, afforded humanity a glimpse into a new world: using microscopes he had built himself, he studied pond and rainwater in 1675, discovering what he described as little animals ('animalcula') - protozoa and bacteria. Later, he also observed microorganisms in human saliva and dental plaque. It was apparently a life-altering experience. From then on, Leeuwenhoek rubbed his teeth with salt and killed bacteria by gargling with vinegar.
Antoni van Leeuwenhoek (1632-1723) is deemed to be the discoverer of bacteria.
In 1826, better quality glass production, allowed Joseph Jackson Lister, father of Joseph Lister, to make improved microscopes with 1,000 times magnification.
However, despite these early discoveries, it took approximately two centuries for microorganisms' significance in causing diseases - to be recognized. Scholars of that era persisted in the belief of four humours as the cause of epidemics, attributing them to toxic emanations from the ground.
The next great breakthrough came in the 1860s when Louis Pasteur, using Joseph Lister's microscope, confirmed germ theory and revolutionised medical knowledge.
Video: Microscopes and Germ Theory
Louis Pasteur
In the 1850s, French scientist Louis Pasteur was employed by a brewing company to find out why their beer was going sour. Through the microscope he discovered micro-organisms growing in the liquid. He believed that these germs, so-called because they appeared to be germinating or growing, were causing the problem. He discovered that the microscopic bacteria which turned beer bad could also be killed by heating, ie by pasteurisation.
Louis Pasteur (1822 - 1895). French chemist and microbiologist.
In 1861, Pasteur published his germ theory and by 1865, had proved the link between germs and disease. In 1879, he discovered a vaccine for chicken cholera. He found that when the germ was exposed to air it weakened, and that injecting this weakened germ into chickens prevented them from catching the disease.
Robert Koch
In the late 1870s the German, Robert Koch began to apply Pasteur's ideas to human diseases. In doing so, he created the science of bacteriology. He identified the bacteria which caused anthrax (1875), TB (1882) and cholera (1883). Koch was very thorough. To isolate the anthrax bacteria, he transferred the bacteria through 20 generations of mice until he was satisfied that he had the right micro-organism. Koch also developed a medium for growing bacteria and a way of staining them so that they could be seen more easily.
Koch's success spurred Pasteur into action again. At the time, there was intense rivalry between France and Germany, following a war in 1870. The German government had given Koch a team of scientists to assist him and now the French government decided to back Pasteur, who went on to develop vaccines. In the 1880s and 1890s rapid progress was made in identifying the bacteria that caused disease and in developing vaccines.
Heinrich Hermann Robert Koch (1843-1910) German physician and microbiologist.
Government supported research
Governments in Europe, recognizing the importance of the field or medical research, supported the efforts of scientists with money and significant progress was made.
- In Wales, Dr J W Power, the Medical Officer of Health for Ebbw Vale, was instrumental in getting courses in bacteriology set up in King's College, London.
- Scientists like Pasteur and Koch led teams of able scientists. Emil von Behring, one of Koch's team, discovered anti-toxins and, with Emile Roux, an associate of Pasteur, used them to develop a vaccine for diphtheria.
- Paul Ehrlich, a student of Koch, produced the drug Salvarsan 606 to treat syphilis. This was the first of what came to be known as silver bullets, drugs designed to target specific germs.
- Scottish surgeon Joseph Lister (1827-1912) began successfully using phenol to disinfect wounds prior to operating.
Public healthcare emerges
The late 19th century saw devastating cholera outbreaks, like the 1892 epidemic in Germany and governments finally began recognizing the need for the systematic development of public health care systems. In order to deprive disease of what it needs to spread, an effort was made to eliminate garbage and sewage from cities. Extensive efforts were made including the distribution of boiled water, disinfection of streets and buildings with various chemicals and heightened public health awareness campaigns. Toward the century's end, the widespread use of sterilizers, sterile materials and disinfectants became customary in medical practices.
