Lysine Decarboxylase Medium is recommended by ISO 6579 and ISO 19250 for the biochemical confirmation of Salmonella based on lysine decarboxylation. It is also recommended by ISO 10273 for the biochemical confirmation of Yersinia. When the medium is inoculated with a bacterium that is able to ferment dextrose, the acid produced lowers the pH of the medium and changes the color of the indicator from purple to yellow. The acidic condition also stimulates decarboxylase activity. The bacteria that decarboxylate the L-Lysine to cadaverine are identified by the presence of a purple-red color. The production of these amines elevates the pH of the medium. A yellow color after 24 hours indicates a negative result. A yellow color after 24 hours indicates a negative result, such as Yersinia. Yeast extract extract is the source of vitamins, of particularly the B-group, essential for growth. Dextrose is the fermentable carbohydrate. Bromocresol purple is the pH indicator. Lysine is added to detect the production of the specific enzyme.
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