Germ Theory and Principles of Infection

Louis Pasteur 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. Pasteur proves that germs cause disease. Micro organism enter the body in number of ways. Specific diseases are caused by specific micro- organism. 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.

Germ Theory of Disease 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.

Research on Theory Pasteurization 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.  

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.

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.

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.

1546- Girolamo Fracastaro- Disease caused by minute seeds and was spread from person to person. 1835: Agostino Bassi- showed a silkworm diseases was caused by a fungus 1840s: Ignaz Semmelwise- advocated hand washing to prevent transmission of fever from one patient to another. He promoted the idea that doctors were killing their patients by not washing their hands after an operation and moving on to the next patient. 1860s: Joseph Lister- He is the father of antiseptic surgery. He introduces antiseptic for the prevention and cure of wound infection.

He used a chemical disinfectant (carbolic acid) to prevent surgical wound infections after reading Pasteur’s work showing microbes are in the air, can spoil food, and cause animal disease.

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. He identified the germs which cause tuberculosis and cholera. More scientific basis “Robert Koch postulates”.

Further Research with Theory Louis/Koch’s Koch’s demonstrated the Germ Theory of Disease Koch’s Postulates: The same pathogen must be present in every case of the disease. Pathogen must be isolated from the diseased host and grown in pure culture. The pathogen from the pure culture must cause the disease when inoculated into a healthy susceptible laboratory animal. Pathogen must be isolated from the inoculated animal and shown to be the original organism.

Koch’s Postulates

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.