Question: What is Koch's postulates

Michael Kimwele answered on 17 Jul 2025:

Koch’s postulates are a set of four criteria established by German physician Robert Koch in the 19th century to identify the causative agent of a particular infectious disease. They are:

The microorganism must be found in all organisms suffering from the disease, but not in healthy individuals.

The microorganism must be isolated from a diseased organism and grown in pure culture.

The cultured microorganism should cause disease when introduced into a healthy, susceptible host.

The microorganism must be re-isolated from the experimentally infected host and identified as being identical to the original causative agent.

These postulates laid the foundation for microbiology and infectious disease research, though modern science recognizes that some pathogens (like viruses or asymptomatic carriers) may not fulfill all four postulates.