Germ Theory

1. Germ Theory

2. Koch’s Postulates • If a microorganism is the causative agent of an infectious disease, it must be: • found in abundance in all organisms suffering from the disease, but should not be found in healthy animals* • isolated from a diseased organism and grown in pure culture. • should cause disease when introduced into a healthy organism. • must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

3. Koch’s Postulates Continued • Basically, Robert Koch established a scientific method for establishing the cause of a disease.  • In doing so, he pioneered the field of microbiology.  • He received a Nobel Prize in 1905 for isolating bacteria that caused anthrax, tuberculosis and cholera.  * His first postulate he abandoned some time later, after he discovered some hosts had no symptoms

4. Steps in Pathogenesis • To cause disease, a pathogen must: • Contact the host - be transmissible • Colonize the host - adhere to and grow or multiply on host surfaces • Infect the host - proliferate in host cells or tissues • Evade the host defense system - by avoiding contact that will damage it • Damage host tissues - by physical (mechanical) or chemical means

5. Milestones in the History of Medicine

6. Overview of Some Diseases • The Germ Theory (around 1860) • single most important contribution by the science of microbiology to the general welfare of the world's people • The theory that microorganisms may be the cause of some or all disease. • Key to developing the germ theory of disease was a refutation of the concept of spontaneous generation. • Specific aseptic techniques are employed to avoid microbial contamination • Method of prevention of spoilage of liquid foodstuffs - Pasteurization