Decarboxylase Broth Base, Moeller is supplied by HiMedia. It is a sterile ready prepared media containing 5ml of purple coloured clear solution in bottles. Decarboxylase Broth Base, with the addition of L-aminoacid, is generally used to differentiate bacteria on the basis of their ability to decarboxylate the amino acid. It is advisable to store this ready prepared media between 2-8C. Composition (in gm/L) is as follows:

Peptic digest of animal tissue (5.00)

Beef extract (5.00)

Dextrose (0.50)

Bromocresol purple (0.01)

Cresol red (0.005)

Pyridoxal (0.005)

Moeller Decarboxylase Broth Base is used for differentiating gram-negative enteric bacilli on the basis of their ability to decarboxylate amino acids. This medium comprises of beef extract and peptic digest of animal tissue, which provide nitrogenous nutrients for the growth of bacteria. The fermentable carbohydrate is dextrose and pyridoxal is the co-factor for the decarboxylase enzyme. Bromo cresol purple and cresol red are the pH indicators in this medium. When the medium is inoculated with the dextrose fermenting bacteria, the pH is lowered due to acid production, which changes the colour of the indicator from purple to yellow. Acid produced stimulates decarboxylase enzyme. Decarboxylation of lysine yields cadaverine while putrescine is produced due to ornithine decarboxylation. 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 colour of the indicator from yellow to purple. If the organisms do not produce the appropriate enzyme, the medium remains acidic, yellow in colour. Each isolate to be tested should also be inoculated into Moeller Decarboxylase Broth Base medium tube lacking the amino acid.