The last statement does not represent one of Koch's postulate, that is, the postulate did not include determination of how long it takes for the healthy animal to become ill. Koch's postulate established four criteria for determining the causative organism for a particular disease. The criteria are: the causative organism must be present in all cases of the disease, the causative organism must be isolated from the diseased host and grown in pure culture, the causative organism from the pure culture must cause the disease when inoculated into a health susceptible animal and the causative organism must be re-isolated from the new host and proof to be the same as the original causative organism inoculated into the health animal.
