Question

Explain how you would use Robert Koch's postulates to determine that Streptococcus pyogenes is the causative agent of streptococcal pharyngitis ("strep throat").

Answer 1

Robert Koch postulates are -

• An infectious agent must be identified in a specimen.
• Can be cultured as a pure culture
• The infectious agent when injected into healthy individual should produce same type of infection
• Same infectious agent must be isolated from all infected individuals.

To identify Streptococcus pyogens as the causative agent of strptococcal pharyngitis, first, sputum or throat swab of infected person should be collected.

The collected sample is cultured.

The cultured organism is identified through staining and biochemical tests.

The oragnism again cultured to obtain a pure culture.

Then the pure cultured organism is tested on a healthy individual, if same type of symptoms are observed then the samples are collected to isolate the infectious agent (Streptococcus pyogens). Culturing and identification of organism from the sample is if found with Streptococcus pyogens, then it is confirmed that streptococcal pharyngitis is caused by Streptococcus pyogens.