tube Yellow Yellow Green or blue
Sealed tube Green Yellow Green
Oxidative organism Fermentative organism No utilization of carbohydrate
Oxidative control: Pseudomonas aeruginosa. Fermentative control: Escherichia coli.
PHENYLALANINE DEAMINASE TEST
The test, which is also referred to as the Phenylpyruvic acid (PPA) test, is used mainly to assist in the identification of enterobacteria. It is based on the ability of bacteria such as Proteus specdies and some Providencia strains to break down phenylalanine (by oxidative deamination) with the production of phenylpyruvic acid. Y.enterocolitica (urease – producer is a phenylalanine negative.
The test organism is cultured on a slope of phenyiaianine medium. After overnight incubation, the deamination of phenylaianjine to phenyl – pyruvic acid is detected by adding iron III chloride (ferric chloride) which produces a green colour on the surface of the culture.