Question

An outbreak of a disease occurs, and a scientist at the Centers for Disease Control (CDC) is in charge of determining the cause. She is studying the microorganism that is thought to be responsible for the disease. Which of the following would be the most helpful to the scientist?
Pasteur's germ theory of disease
Koch's postulates

Answer 1

Koch's postulates.

Reason: Koch’s postulates give specific, testable steps for proving that a particular microorganism causes a particular disease (presence in diseased hosts, isolation and growth in pure culture, reproduction of disease upon inoculation of a healthy host, and re-isolation of the same organism). Pasteur’s germ theory is the broad principle that microbes can cause disease, but Koch’s postulates are the practical framework used to identify and demonstrate the causal agent.

Note: Some pathogens (viruses, obligate intracellular organisms, asymptomatic carriers, polymicrobial diseases) don’t fit the classical postulates, so modern investigators often use molecular Koch’s postulates and molecular/epidemiologic methods (PCR, sequencing, serology) alongside the classical approach.