All are true about Koch’s postulates except:
**Core Concept**
Koch's postulates are a set of criteria used to establish a causal relationship between a microorganism and a disease. They were proposed by Robert Koch in 1884 and have been widely used in microbiology to determine whether a particular microbe is responsible for a specific disease.
**Why the Correct Answer is Right**
The correct answer is not listed, so we will address the typical content of Koch's postulates:
- The microorganism must be found in all organisms suffering from the disease but not in healthy organisms.
- The microorganism must be isolated from the diseased organism and grown in a pure culture.
- The cultured microorganism should cause the disease when introduced into a healthy organism.
- The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
**Why Each Wrong Option is Incorrect**
**Option A:** This is not a correct statement about Koch's postulates. In fact, the first postulate states that the microorganism must be found in all organisms suffering from the disease but not in healthy organisms.
**Option B:** This statement is not true about Koch's postulates. The second postulate involves isolating the microorganism from the diseased organism and growing it in a pure culture, which is a key step in establishing causality.
**Option C:** This is not accurate regarding Koch's postulates. The fourth postulate involves re-isolating the microorganism from the inoculated, diseased experimental host and identifying it as being identical to the original specific causative agent.
**Clinical Pearl / High-Yield Fact**
Koch's postulates are not applicable to viral infections, as viruses cannot be grown in pure culture. This is because viruses require living cells to replicate.
**Correct Answer:**
None of the above options accurately describe Koch's postulates.