structural:scholar_edition
Koch's postulates

During his time as government advisor, Koch published a report on how he discovered and experimentally showed tuberculosis bacterium as the pathogen of tuberculosis. He described the importance of pure cultures in isolating disease-causing organisms and explained the necessary steps to obtain these cultures, methods which are summarized in Koch's four postulates. Koch's discovery of the causative agent of anthrax led to the formation of a generic set of postulates which can be used in the determination of the cause of most infectious diseases. These postulates, which not only outlined a method for linking cause and effect of an infectious disease but also established the significance of laboratory culture of infectious agents, became the "gold standard" in infectious diseases.

Although Koch worked out the principles, he did not formulate the postulates, which were introduced by his assistant Friedrich Loeffler. Loeffler, reporting his discovery of diphtheria bacillus in 1883, stated three postulates as follows:

The fourth postulate was added by an American plant pathologist Erwin Frink Smith in 1905, and is stated as: