What sugar is used in Salmonella-Shigella agar?

The primary sugar used in Salmonella-Shigella agar is lactose. This agar is designed to differentiate between lactose fermenting and non-fermenting bacteria. Specifically, lactose fermentation results in acid production, which can be detected by a color change in the pH indicator incorporated into the medium. When lactose is fermented by certain bacteria, it leads to a pink coloration of the colonies due to the acid produced.

Salmonella and Shigella species are non-lactose fermenters, which means that colonies of these organisms will appear colorless or pale on the agar, distinguishing them from lactose fermenters. The incorporation of lactose into the media is crucial for identifying these pathogenic bacteria, making it an essential feature of Salmonella-Shigella agar.

Other sugars like glucose, sucrose, or xylose are not used in this medium for the primary differentiation of lactose fermenters versus non-fermenters regarding Salmonella and Shigella. Each of those sugars may have their own applications in different media types, but they do not play a role in the specific functionalities of Salmonella-Shigella agar.