Koch's postulates

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Dna ncifcrf gov.jpg This article/section deals with advance bioscience concepts appropriate for a student in late university and graduate school.

Koch's postulates are a set of broad principles laid out by Robert Koch in the 1880's. They are the basic criteria for determining what is and is not an infectious disease in plants, animals, and humans. Because they are at the level of philosophy of science, they can be applied to viral, bacterial, or parasite-caused infection theories. Though aspects of the principles were not original, Robert Koch provided an experimental basis for these principles that was very convincing to the scientists of his day.

Contents

The Postulates

Epidemiological association

An association should exist between a microorganism and disease (i.e., the organism is identified or recovered from patients).

For a molecular version: a relationship exists between a phenotype/function and pathogenicity.

Isolation

The suspected pathogen can be isolated - and propagated - outside the host.

For a molecular version: a mutation should be constructed or isolated in the gene encoding the function, forming an isogenic mutant strain, so that the function is eliminated.

Transmission Pathogenesis

Transfer of the suspected pathogen to an uninfected host, man or animal, produces the disease in that host.

For a molecular version: the isogenic mutant strain should be attenuated for virulence in an appropriate model (a negative control).

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