What is the main function of bile salts in Salmonella-Shigella agar?

The main function of bile salts in Salmonella-Shigella agar is to inhibit the growth of coliforms. This selective inhibitory action allows for the preferential growth of salmonella and shigella, which are pathogenic bacteria that need to be isolated from samples. Bile salts create an environment that suppresses many non-pathogenic enteric bacteria, particularly coliforms, which are typically less resistant to bile salts.

This selective pressure is crucial in diagnostic microbiology, as it helps to identify and differentiate pathogenic strains by preventing the overgrowth of competing organisms, thereby enhancing the visibility and isolation of the target pathogens. The effectiveness of Salmonella-Shigella agar in isolating these pathogens can be attributed to this selective inhibition, ensuring that the culture conditions favor the growth of the desired bacteria while limiting contaminants.