Germ theory of disease: History, Experiments, Postulates

The germ theory of disease is a medical theory that asserts that microorganisms are the cause of disease. When the French chemist Louis Pasteur discovered that processes like putrefaction and fermentation occur due to the existence of organisms that thrive in air, he developed the germ theory.

Key Takeaways: Germ theory of disease, microorganism, microbes, fermentation, disease, bacteria, organism

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History of Germ Theory of Disease

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The Miasma theory, which claimed that disease was caused by the decomposition of organic matter, which generated a noxious air containing disease-causing chemicals, was popular until germ theory was recognised. Experiments conducted by Fransisco Redii in the 1600s proved the concept of spontaneous development of diseases. He put a loaf of meat and an egg in three different jars in his experiments:

• The first jar had been left open. The meatloaf and egg were found to be covered in maggots.
• The second jar was tightly sealed with a lid. There were no maggots found.
• Only gauze was used to cover the third jar. There were no maggots within the jar, but they were found on the surface of the gauze.

As a result, Redii disproved the idea of spontaneous generation. The germ theory of disease was also reinforced by Anton Van Leeuwenhoek, the first microbiologist to view microorganisms under a microscope. Marcus Antonius Von Plenzic later backed Richard Bradley's hypothesis that diseases were caused by microbes.

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Experiments that support the Germ Theory of Disease

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Under the following conditions, the freshly boiled soup was exposed to air:

• To prevent particles from entering the growth medium, it was stored in a tank with a filter.
• The growth media was exposed to room air and kept in a vessel without a filter.
• To prevent dust particles from entering the growing medium, it was kept in a vessel and exposed to room air through a long tube.

Pasteur noticed that soup that was not filtered and exposed to room air generated bacteria. Ignaz Semmelweis, John Snow, and Robert Koch, among others, made significant contributions to the germ theory of disease.The experiments carried out by Louis Pasteur and Robert Koch, on the other hand, gave precise proofs in support of the germ theory of disease.

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Importance of Germ Theory of Disease

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The germ theory revolutionised pathology and surgery by demonstrating that significant disorders are caused by microorganism infection. The discovery of penicillin marked a milestone moment in history, a revolution within a larger revolution. Antibiotics were developed in the context of the discovery of germ theory, which explained how different diseases worked.

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Why was the Germ Theory of Disease not accepted? 

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The germ theory of disease, which states that infectious disease is produced primarily by the passage of an organism from one host to another, is an oversimplification. It agrees with the fundamental truths that infection is impossible without an organism and that transmissible organisms can cause disease, but it fails to explain the exceptions and anomalies. Because it ignores the many other elements that play a role in determining whether the host/germ/environment complex will lead to infection, the germ theory has become a dogma. Susceptibility, genetic constitution, behaviour, and socioeconomic factors are among them.

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Germ Theory of Fermentation

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Louis Pasteur's experiments led him to the conclusion that bacteria in the air spoiled the fermentation broths. He carried out a variety of different fermentation procedures for substances such as lactic acid, butyric acid, and others. As a result, he proposed the germ theory of fermentation, according to which every fermentation process is influenced by microbes. He went on to explain that the hypothesis may be applied to both animal and human diseases. He discovered that microorganisms existing in or around the body are also responsible for the diseases.

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Koch’s Postulates

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A specific disease is caused by a specific organism, according to Robert Koch. He was able to extract anthrax from a diseased patient and use it in studies. He then came up with a set of postulates based on the following four rules:

• Only the infected person's microbe needs to be recognised, not the healthy person.
• The microorganism should be identified and cultured from the diseased person.
• When a healthy person is exposed to the cultured microbe, it should cause disease.
• The microbe should be extracted from the experimental host once more, and it should be the same as the original organism.

When Louis Pasteur cultured anthrax bacillus, he provided the decisive proof of the germ theory of disease. He took blood from an anthrax-infected sheep and placed it on a sterile culture, where the bacilli could thrive. He continued the process until the final dish included no trace of the original culture. When the final culture was put into the sheep, anthrax was produced. This established that the bacillus was the cause of the sickness.

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Things to Remember

Following are some important points:

• Many diseases are caused by microorganisms such as bacteria, viruses, protozoa, or fungi, according to the germ theory of disease.
• Until the germ hypothesis was developed, the Miasma theory was popular and widely accepted.
• When the French chemist Louis Pasteur discovered that processes like putrefaction and fermentation occur due to the existence of organisms that thrive in air, he developed the germ theory.
• According to the germ theory of fermentation, certain bacteria are responsible for initiating the fermentation process.
• Robert Koch was the first to propose that a given type of microbe caused a specific form of disease.

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