#8. Koch’s postulates

 A postulate is a statement that is assumed to be factually true which is then used as the basis of reasoning in another argument. In 1884, the time of your great grandparents, an English physician, Robert Koch gave the final word for defining diseases caused by microorganisms. These (below) are known as Koch’s Postulates.

#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.

#3. The isolated pathogen can be grown in pure culture. (This means that a tiny sample of the pathogen, when placed on an agar-plate or in a nutrient broth, will proliferate abundantly.)

#4. The pathogen from the pure culture must cause the disease   when inoculated into a healthy, susceptible laboratory animal.