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Etymology: Robert Koch; L, postulare, to demand
the prerequisites for experimentally establishing that a specific microorganism causes a particular disease. The following conditions must be met (1) the microorganism must be observed in all cases of the disease; (2) the microorganism must be isolated and grown in pure culture; (3) microorganisms from the pure culture, when inoculated into a susceptible animal, must reproduce the disease; and (4) the microorganism must be observed in and recovered from the experimentally diseased animal.
Koch's postulatesA series of 4 conditions that must be met to establish an infectious agent as the cause of a particular disease or condition. See Molecular Koch's postulates.
1. The agent must be present in all cases of the disease
2. The agent must be isolated from someone with the disease and grown in pure culture
3. Inoculation into a susceptible organism of the agent–from a pure culture—must produce the disease
4. The agent must be recovered from the infected–inoculated organism and grown again in culture