Moeller Decarboxylase Broth Base, when supplemented with arginine, aids in the differentiation of enteric bacilli by means of a dihydrolase reaction.

• Differentiates gram-negative enteric bacilli based on decarboxylation of amino acids
• Beef extract and peptic digest of tissue provide nitrogenous nutrients
• Dextrose is a fermentable carbohydrate
• Pyridoxal is the co-factor for the decarboxylase enzyme
• Bromo cresol purple and cresol red are pH indicators

Arginine is first hydrolyzed to ornithine, which is then decarboxylated to form putrescine. Formation of these amines increases the pH of the medium, changing the color of the indicator from yellow to purple. If the organisms do not produce the appropriate enzyme, the medium remains acidic, yellow in color. Each isolate to be tested should also be inoculated into Moeller Decarboxylate Broth Base medium tube lacking the amino acid.