Germ Theoryand Principles of Infection

By Rabia Chaudhry

Louis Pasteur, French microbiologist and the 'father' of “Germ theory of disease.”

Background of Theorists

Louis Pasteur (1822-1895),

• French professor of microbiology.• Studied how yeasts (fungi) ferment in wine and beer• Proved that heat destroys bacteria and fungi • First to propose the Germ theory of disease in 1958.• Pasteur proves that germs cause disease.• Micro organism enter the body in number of ways.• Specific diseases are caused by specific micro- organism.• Natural immunity is an inherited resistance to infection.

• Therapeutic measures suggested by the Germ Theory included asepsis, antisepsis and disinfection techniques (to prevent contamination by microbes).

• He theorized that a specific bacterial organism were capable of causing an infectious disease.

• This theory seems simple but it is one of the most critically beneficial in medical field.

(Jeffery, 2006)

Robert Kock (1843-1910)

• German general practitioner• Grew bacteria in culture medium• Showed which bacteria caused particular diseases• Classified most bacteria by 1900

• He stained germs to help him to see them better.

• Among others, he identified the germs which cause tuberculosis and cholera.

• More scientific basis “Robert Koch postulates”.

(Thomas, 1996)

Louis Pasteur discovered that germs cause disease. He believed that they caused things like food and drink to go bad, and brought sickness to animals and men.

Germ Theory of Disease

Louis was studying wine and why wine went bad. He found that the wine remained good if it is air sealed.

In addition, he found that heat kills the germs. In turn, milk is heated today to destroy germs. We call it ‘pasteurised milk’. Pasteurization prevents milk from going sour by killing the germs and we sealing it from the air.  

(Ernst, 1995)

Research on Theory Pasteurization

Linking Germs to Disease/Infection

• Louis proposed “If wine and beer are changed by germs, then the same can and must happen sometimes in humans and animals.”

• French Silk Industry• Asked Pasteur to investigate

why their silkworms kept dying.

• He discovered that a certain germs were responsible for it.

(Ernst, 1995)

Theory applied to Nursing

In 1873 Louis Pasteur’s little daughters died from typhoid. He mourned his daughter but also decided to study the disease which attacked animals and men.

He began to work in hospitals which were dreadful places in 1800s, full of germs. He used disinfectants to kill germs and kept everything clean. After that, number of deaths reduced dramatically in the hospital.

(Jeffery, 2006)

Theory applied to Nursing

(Vaccinations)Germ = Germination

Louis was able to show that germs caused disease in sheep. He noticed that once an animal had a disease they never caught it again. He decided it must have been that the dead germs in blood saved the animals from new, living germs. So if he put some harmless germs into the animals blood it would never be attached by live germs. Today we call this vaccination. This was a wonderful discovery! Pasteur also produced a vaccines for chicken cholera and anthrax, and then a vaccine for humans against rabies.

(Jeffery, 2006)

Further Research with Theory Louis/Koch’s

• Koch’s demonstrated the Germ Theory of Disease

• Koch’s Postulates:1. The same pathogen must be present in every

case of the disease.2. Pathogen must be isolated from the diseased

host and grown in pure culture.3. The pathogen from the pure culture must cause

the disease when inoculated into a healthy susceptible laboratory animal.

4. Pathogen must be isolated from the inoculated animal and shown to be the original organism.

(Tortora, 2004)

Koch’s Postulates

Tortora, 2004

Theory applied in Nursing Practice

• According to the CDC, hand-washing is the single most important means of preventing infection

• Pasteur brought the use of aseptic techniques which is wildly used all over the world

• Handling contaminated materials carefully • Paying special attention to cleanliness of respirators/humidifiers• Single-use dressings/tubes• Prescribe antibiotics only when necessary• Using personal protective equipment [PPE]• Isolation (Contact, Droplet, Airborne)• Environmental cleaning• Risk management/assessment

(McEwen, 2007)

Conclusion• Acceptance of germ theory is highly significant for medicine.

• Reformation of this theory helped practicing medicine more efficiently

• Immunology• Antiseptic/aseptic surgery• Public health

• Medicine became more effective once the cause of disease had been found, scientists could work on preventions and cures.

• It influenced public health , e.g. encouraging the 1875 Public Health Act.

• Emphasis on breaking chain of infection• Discovery of healthy carriers• Typhoid fever

• Germ phobia & changes in hygienic practices were implemented.

• Recent events: the swine flu to fight this virus most important thing is to do frequent handwashing.

References

• Ernst, H. C.,Pasteur, L., On the extension of germ theory to the etiology of certain disease. http://biotech.law.lsu.edu/cphl/history/articles/pasteur.htm#paperIII, 1995.

• Jeffrey, C. P., (2006). Alcamo's Fundamentals of Microbiology: Body Systems. Microbiology then and now. (pp19-22). Jones and Bartlett Publishers.

 • McEwen, M., (2007). Theoretical Basis for Nursing. (2nd Ed.), Philosophy, Science, and

Nursing. (pp.3-23). Lippincott Williams & Wilkins

• Pasteur, Louis. (2001).Scientific Papers. Vol. XXXVIII, Part 7. The Harvard Classics. New York: P.F. Collier & Son, 1909–14; Bartleby.com. www.bartleby.com/38/7/.

• Thomas, D. B., (1996). Robert Koch: a life in medicine and bacteriology Sequence-based identification of microbial pathogens a reconsideration of Koch's postulates by Clin Microbiol Rev. Jan;9(1):18-33.

• Tortora, F., (2004). Microbiology: An Introduction, (8th Ed.), Infectious Diseases and Epidemiology: Concepts; Koch's Postulates. Pearson Education, Inc, San Francisco.