Question

According to Koch’s first postulate

• A. The same disease causing agent must be isolated from experimentally infected animal
• B. The isolated causative agent of the disease must be able to produce disease when injected into healthy animal
• C. The causative agent of the disease must be present in every diseased animal
• D. The disease causing agent must be isolated from diseased animal and grown in pure culture

Hint:

While highly useful, Koch's postulates have limitations; for example, they cannot be fully applied to viruses or prions, which are obligate intracellular parasites that cannot be grown in cell-free pure culture.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Koch’s postulates are a set of four generalized criteria established by Robert Koch in 1890.
They are used to identify the causal relationship between a specific microorganism and a specific infectious disease.

Step 2: Detailed Explanation:
Let us review the four classical postulates in sequence:
1. First Postulate (C): The suspected pathogen must be present in all cases of the disease, and absent from healthy, susceptible animals. This matches option (C).
2. Second Postulate (D): The suspected pathogen must be isolated from the diseased host and grown in a pure culture laboratory media.
3. Third Postulate (B): The isolated pathogen from the pure culture must cause the same disease when inoculated into a healthy, susceptible experimental host.
4. Fourth Postulate (A): The same pathogen must be re-isolated from the experimentally infected host and shown to be identical to the original isolated pathogen.

Step 3: Final Answer:
According to Koch's first postulate, the causative agent must be present in every diseased animal, corresponding to option (C).