Paper I — 2025 March (Supplementary) (2010 Scheme) — Q12
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Paper I
2025 March (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Koch’s postulates
Q122 marksShort Notes
Answer
Koch’s postulates are a set of criteria formulated by Robert Koch to establish a causal relationship between a specific microorganism and a specific disease.
The four postulates:
The microorganism must be found in abundance in all organisms suffering from the disease, but not in healthy individuals.
The microorganism must be isolated from a diseased host and grown in pure culture.
The cultured microorganism, when introduced into a healthy, susceptible host, should cause the same disease.
The microorganism must be re-isolated from the experimentally infected host and identified as identical to the original agent.
Limitations: some pathogens cannot be grown in pure culture (M. leprae, T. pallidum); some require living host cells (viruses, obligate intracellular bacteria); asymptomatic carriers exist for many pathogens; some diseases require multiple organisms or host/environmental cofactors; ethical constraints prevent deliberate human experimental infection. Modified/molecular Koch’s postulates incorporating molecular genetic criteria have been proposed to address these gaps.
