Is Simmons citrate agar selective or differential?

Simmons citrate agar is a differential medium. It is used to determine an organism's ability to utilize citrate as its sole carbon source. The medium contains bromothymol blue as a pH indicator, which changes color based on the pH level, allowing for differentiation between citrate-utilizing and non-utilizing bacteria. While it has some selective properties due to its composition, its primary function is to differentiate based on metabolic capabilities.