Question

Which of the following statements is NOT true for Koch's postulates?
A. A specific organism can always be found in association with a given disease
B. The organism can be isolated from a diseased animal and grown in pure culture in the laboratory
C. The pure culture will produce the disease when inoculated into a resistant animal
D. The pure culture will not produce the disease when inoculated into a susceptible animal
E. It is possible to recover the organism in pure culture from the experimentally infected animal
Choose the correct answer from the options given below:

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

Hint:

Koch's postulates:
1. The pathogen must be present in every diseased host.
2. It must be isolated and grown in pure culture.
3. It must cause the disease when inoculated into a healthy susceptible host.
4. It must be re-isolated from the experimentally infected host.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
Koch's postulates are a set of criteria used to establish a causal relationship between a microorganism and a disease.

Step 2: Detailed Explanation:
Koch's postulates state that:
1. The microorganism must be found in all organisms suffering from the disease (A).
2. The microorganism must be isolated from a diseased organism and grown in pure culture (B).
3. The pure culture must cause the disease when inoculated into a healthy susceptible organism (C is incorrect because it says 'resistant animal' instead of 'susceptible').
4. The microorganism must be re-isolated from the experimentally infected organism and identified as the same as the original (E).
Thus, C is incorrect because it mentions "resistant animal" instead of "susceptible animal".
D is incorrect because the pure culture will produce the disease when inoculated into a susceptible animal.
Therefore, statements C and D are NOT true for Koch's postulates.

Step 3: Final Answer:
Thus, the correct answer is C and D only, which corresponds to option (A).
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