What are Koch's postulates used to prove?

Developed by the German physician Robert Koch, Koch’s postulates are a set of four scientific criteria used to establish a definitive causal relationship between a specific microorganism and a specific disease.12

These postulates are as follows:

• A specific microorganism is always associated with a specific disease.12
• The microorganism can be isolated from the diseased animal and grown in pure culture in the laboratory.12
• The cultured microorganism will cause the same disease when transferred to a healthy animal.12
• The microorganism can be isolated from the newly infected animal and confirmed as being identical to the original causative organism.12

By providing a rigorous framework for identifying the etiology of infectious diseases, these postulates transformed the field of microbiology and remain a fundamental component of medical research.32