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Koch’s Postulates. A Logical Mechanism for Determining the Cause of Diseases with Near Certainty. What do they do? . Koch’s postulates provide a logical mechanism used to prove that a specific microorganism causes a specific disease with near certainty. Overview of Koch’s Postulates.
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Koch’s Postulates A Logical Mechanism for Determining the Cause of Diseases with Near Certainty
What do they do? Koch’s postulates provide a logical mechanism used to prove that a specific microorganism causes a specific disease with near certainty.
Overview of Koch’s Postulates • Overall, Koch’s postulates state: • The suspected pathogenic organism should be present in all cases of the disease. In addition, the organism should be absent from all healthy animals. • The suspected organism should be grown in pure culture, a laboratory grown culture containing only one type of microorganism. • If a healthy animal is inoculated with cells from the pure culture, that is the cells are introduced to the animal’s body, the animal should become diseased. • The pathogenic organism should be isolated from the newly infected animal, grown in laboratory culture and be shown to be identical to the original organism.
Step One: Determine a suspected pathogen. • Observe infected samples (blood, tissue, etc.). • Should contain the suspected pathogen. • Different staining techniques may be used to allow better differentiation between cells. • Observe healthy samples. • Should not contain the microorganism. • If the suspected microorganism is present in the healthy animal it can be concluded that it is not the pathogen for the target disease.
Step Two: Grow suspected organism in laboratory culture. • Grow a pure culture on a media. • A culture media is a solution of various nutrients, such as carbon, nitrogen, vitamins, sugars and amino acids, suitable for the growth of microorganisms. • Different types of media: • Solid, semi-solid and liquid • Defined and complex • Note: Choosing the proper media is essential because different microorganisms will grow in certain conditions, but not others.
Step Three: Test the isolated suspect organism. • Inoculate a healthy test animal with the suspected pathogen. • If the animal develops the disease, the microorganism may still be the causative agent. • If the animal does not develop the disease, the organism is not the causative agent.
Step Four: Reisolate the suspected pathogen. • If the suspected pathogen caused disease in the test animal: • Reisolate the microorganism from the animal. • Grow the microorganism in a pure culture. • Examine the microorganism. • If the microorganism is the same as the original organism used in step two, it can be concluded that it is the causative agent of the disease in question.
Conclusion • Koch’s postulates can determine with an unparalleled amount of certainty that a microorganism causes a specific disease. • Helps researchers understand the behavior of diseases. • Aids in the discovery of cures and vaccines. • It is sometimes impossible to satisfy all of Koch’s postulates. • Other methods must be employed to link a pathogen to a specific disease. • The logical mechanism can also be used in other applications.
Bibliography Leboffe, M. J., & Pierce, B. E. (2006). Microbiology Laboratory Theory and Application. Morton Publishing Company. Madigan, M. T., Martinko, J. M., Dunlap, P. V., & Clark, D. P. (2009). Brock: Biology of Microorgansism. San Francisco: Pearson Education, Inc.
