Arginine dihydrolase test for pseudomonas aeruginosa procedure result microbiology

The arginine dihydrolase test (ADH test) is a biochemical test used primarily to determine which bacteria can produce the enzyme arginine dihydrolase. This enzyme breaks down the amino acid arginine through a process called dihydrolysis.

Arginine dihydrolase enzyme converts arginine into ornithine, ammonia, and carbon dioxide. This reaction causes a change in pH, which is detected by a pH indicator in the test medium.

Arginine dihydrolase test procedure

• A broth or semi-solid medium containing arginine and a pH indicator (phenol red) is inoculated with the test organism.
• The inoculated medium is typically incubated for 24-48 hours at an appropriate temperature (usually 35-37°C).
• After incubation, the color change in the medium is observed.
  • A color shift to purple (alkaline pH), indicating the presence of arginine dihydrolase in positive result.
  • No color change or a shift to yellow (acidic pH), indicating the absence of enzyme activity and negative result.

Result Interpretation

• A color shift to purple : The organism can hydrolyze arginine, indicating that it possesses the arginine dihydrolase enzyme.
• No color change : The organism cannot hydrolyze arginine, indicating a lack of arginine dihydrolase enzyme.

Uses of Arginine dihydrolase test

The arginine dihydrolase test is one among many tests used for:

1. Differentiating members of Enterobacteriaceae and Pseudomonas.
2. Identifying other Gram-negative and some Gram-positive bacteria.