Decarboxylase Test
Used to determine whether an organism can decarboxylate an amino acid leading to formation of an amine. Two tubes are used, one containing Møller's decarboxylase medium (control tube), and the other containing Møller's decarboxylase medium and an amino acid (lysine, ornithine or arginine). After inoculation both tubes are overlayed with sterile paraffin oil. Here lysine is used. Glucose-fermenting organisms produce acid in the media and cause the control tube to turn yellow after incubation. Organisms that utilise the amino acid cause alkalinity due to formation of an amine. The indicators are bromcresol purple and cresol red. 1. Uninoculated medium. 2. The control tube is more yellow after incubation than an uninoculated medium. 3. Positive reaction: Salmonella. 4. Positive reaction: Klebsiella. 5. Negative reaction: Citrobacter. Here the medium is more yellow than an uninoculated medium.
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