What are Koch's Postulates

What are Koch's Postulates? 

Answer:  Robert Koch proposed four postulates to identify the causative agent of a particular disease.

These postulates are: 

1. The microorganism or other pathogen must be present in all cases of the disease. 

2. Pathogens can be isolated from the diseased host and grown in pure culture. 

3. Pathogens from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal. 

4. Pathogen must be re-isolated from the new host and shown to be the same as the originally inoculated pathogen