v Principle:-

It is based on the ability of bacteria such as Proteus species to convert phenylalanine in the medium to phenylpyruvic acid by deamination. Phenylpyruvic acid is detected by the addition of ferric chloride ions, which give green color on the surface of the culturez.

v Requirements:-

1.      Phenylalanine agar

2.      10 g/dl ferric chloride (freshly prepared)

v Procedure:-

1.      Inoculate a slope of the phenylalanine agar with test organisms.

2.      Incubate at 35-37°C overnight.

3.      Add 3 to 4 drops of ferric chloride reagent and observe the color.

v Observations:-

1.      Green color                     : Positive test

2.      No green color              : Negative test

v  Quality control:-

Use following microorganisms to confirm the reliability of reagents:

Positive control         : Proteus sp.

Negative control         : E. coli