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'Kochs postulates (or Henle-Koch postulates''') are four criteria designed to establish a causal relationship between a causative microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890. Koch applied the postulates to establish the etiology of anthrax and tuberculosis, but they have been generalized to other diseases.
The Postulates 'Kochs postulates are:'''
# The microorganism must be found in abundance in all organisms suffering from the disease, but not in healthy organisms.
# The microorganism must be isolated from a diseased organism and grown in pure culture.
# The cultured microorganism should cause disease when introduced into a healthy organism.
# The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
History Koch's postulates were developed in the 19th century as general guidelines to identify pathogens that could be isolated with the techniques of the day. Even in Koch's time, it was recognized that some infectious agents were clearly responsible for disease even though they did not fulfill all of the postulates.Koch R. (1884) Mitt Kaiser Gesundh 2, 1-88; Koch R. (1893) J. Hyg. Inf. 14, 319-333 Attempts to rigidly apply Koch's postulates to the diagnosis of viral diseases in the late 19th century, at a time when viruses could not be seen or isolated in culture, may have impeded the early development of the field of virology.Brock TD (1999) Robert Koch: a life in medicine and bacteriology. American Society of Microbiology Press, WashingtonEvans AS (1976) Causation and disease: the Henle-Koch postulates revisited. Yale J Biol Med 49:175–195 Currently, a number of infectious agents are accepted as the cause of disease despite their not fulfilling all of Koch's postulates. Therefore, while Koch's postulates retain historical importance and continue to inform the approach to microbiologic diagnosis, fulfillment of all four postulates is not required to demonstrate causality.Koch's postulates have also influenced scientists who examine microbial pathogenesis from a molecular point of view. In the 1980s, a molecular version of Koch's postulates was developed to guide the identification of microbial genes encoding virulence factors.Falkow S (1988). "Molecular Koch's postulates applied to microbial pathogenicity." Rev Infect Dis 10(Suppl 2):S274-S276.
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