Koch's postulates

Koch's postulates are four criteria designed to establish a causative relationship between a microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884, based on earlier concepts described by Jakob Henle, and refined and published by Koch in 1890. Koch applied the postulates to describe the etiology of cholera and tuberculosis, but they have been generalized to other diseases.

Koch's Postulates

Postulates

Koch's postulates are as follows:

1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
2. The microorganism must be isolated from a diseased organism and grown in pure culture.
3. The cultured microorganism should cause disease when introduced into a healthy organism.
4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Limitations and refinements

While Koch's postulates have historically played an important role in microbial pathogenesis research, they have been recognized as largely outdated for modern bacterial pathogenesis. Many bacterial species, for example, are not culturable in the laboratory, and it is now clear that there can be healthy carriers of diseases.

See also

• Molecular Koch's postulates
• Rivers' postulates
• Hill's criteria

References

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