Question

Which of the following statements are true for Koch's postulates
A. The microorganisms must be present in every case of the disease
B. The microorganisms may not be present in every case of the disease
C. The microorganisms must be isolated from the diseased host and grown in pure culture
D. The specific disease must be reproduced on inoculation of a pure culture of microorganisms in the healthy susceptible host
E. The microorganism must be recoverable once again from the inoculated susceptible host
Choose the most appropriate answer from the options given below:

• A. A, B, C and D only
• B. A, B, C, D, E
• C. A, C, D, E only
• D. C, D, E only

Hint:

Koch's Postulates: Associate \( \rightarrow \) Isolate \( \rightarrow \) Inoculate \( \rightarrow \) Re-isolate.
Note: These cannot be satisfied by obligate biotrophs (like viruses) because they cannot be grown in "pure culture" on artificial media.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
Koch's postulates, proposed by Robert Koch in 1884, are the four criteria designed to establish a causative relationship between a microbe and a disease.

Step 2: Detailed Explanation:
The postulates are defined as follows:

• Postulate 1 (A): The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. Thus, Statement A is True and B is False.

• Postulate 2 (C): The microorganism must be isolated from a diseased organism and grown in pure culture. This proves the microbe exists independently. Thus, Statement C is True.

• Postulate 3 (D): The cultured microorganism should cause disease when introduced into a healthy, susceptible host. This demonstrates the pathogenic potential. Thus, Statement D is True.

• Postulate 4 (E): The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent. Thus, Statement E is True.
Final Answer:
Statements A, C, D, and E correctly represent the four pillars of Koch's postulates.
The correct option is (C).