Which organism shows a positive phenylalanine deaminase reaction?

Which organism shows a positive phenylalanine deaminase reaction?

• A. Proteus vulgaris
• B. Hafnia alvei
• C. Moraxella catarrhalis
• D. Salmonella Enteritidis

Answer: (A)

Phenylalanine deaminase activity is what this test detects: the enzyme removes an amino group from phenylalanine to form phenylpyruvic acid. After incubation, adding ferric chloride reacts with phenylpyruvic acid to produce a green color. That green change signals a positive reaction. Proteus vulgaris is a classic PAD-positive organism, so it reliably yields the green color and a positive result. The other organisms listed typically do not produce phenylpyruvic acid under standard test conditions, so they fail to develop the green coloration and give a negative result.

Phenylalanine deaminase activity is what this test detects: the enzyme removes an amino group from phenylalanine to form phenylpyruvic acid. After incubation, adding ferric chloride reacts with phenylpyruvic acid to produce a green color. That green change signals a positive reaction. Proteus vulgaris is a classic PAD-positive organism, so it reliably yields the green color and a positive result. The other organisms listed typically do not produce phenylpyruvic acid under standard test conditions, so they fail to develop the green coloration and give a negative result.