In which situation would Koch's postulates most appropriately be utilized?

• A. To classify bacteria based on their Gram stain reaction
• B. To identify the metabolic pathways used by a microorganism
• C. To establish a causal relationship between a specific microorganism and a particular disease
• D. To determine the effectiveness of an antibiotic against a bacterial infection

Answer: (C)

Verified step by step guidance

1. Understand the purpose of Koch's postulates: they are a set of criteria designed to establish a causal relationship between a specific microorganism and a particular disease.
2. Recognize that Koch's postulates involve isolating the microorganism from a diseased host, growing it in pure culture, reproducing the disease in a healthy host by introducing the microorganism, and then re-isolating the same microorganism from the experimentally infected host.
3. Compare the options given: classifying bacteria by Gram stain is a staining technique, identifying metabolic pathways involves biochemical tests, and determining antibiotic effectiveness involves susceptibility testing; none of these directly establish causality of disease.
4. Conclude that Koch's postulates are most appropriately used to establish a causal relationship between a microorganism and a disease, as this aligns with their original purpose and methodology.
5. Therefore, the correct situation to apply Koch's postulates is to establish causality between a specific microorganism and a particular disease.