- 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. The four are:
1. The microorganism or other pathogen must be present in all cases of the disease
2. The pathogen can be isolated from the diseased host and grown in pure culture
3. The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal
4. The pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen