**What are Koch's postulates designed to establish?** Koch's postulates are designed to establish *a causal relationship between a microbe and a disease.* > **How many criteria are there in Koch's postulates?** > There are *four criteria* in Koch's postulates. **What are Koch's four postulates?** Koch's four postulates are: 1. The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms. 2. The microorganism must be isolated from a diseased organism and grown in pure culture. 3. The cultured microorganism should cause disease when introduced to a healthy organism. 4. The microogranism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.