Lysine iron agar is a differential medium for the detection of Salmonella spp. and other enteric pathogens on the basis of lysine decarboxylase and hydrogen sulphide production. Lysine iron agar was originally developed by Edwards and Fife for Salmonella arizonae detection. The peptone and yeast extract provides the required nitrogen, carbon and vitamins. Glucose is a fermentable carbohydrate. L-lysine is used to detect lysine decarboxylase and lysine deaminase enzymes. Sodium thiosulphate is reduced to hydrogen sulphide which is detected by the ferric citrate indicator. Sodium chloride maintains the osmotic balance. Bromocresol purple is a pH indicator. For use the medium is inoculated using a pure culture of the test organism which should be smeared onto the surface of the slope and stabbed into the butt of the medium.