About this test
What is the purpose of the test?
The purpose is to see if the microbe can ferment the carbohydrate (sugar) adonitol as a carbon source.
How is adonitol fermentation determined?
If adonitol is fermented to produce acid end products, the pH of the medium will drop. A pH indicator in the medium changes color to indicate acid production.
What medium is used?
Several media are available for this. Most commonly used is phenol red adonitol broth. The medium is a nutrient broth to which 0.5-1.0% adonitol is added. The pH indicator phenol red is red at neutral pH but turns yellow at pH <6.8. It also changes to magenta or hot pink at pH >8.4.
How is the test performed?
An inoculum from a pure culture is transferred aseptically to a sterile tube of phenol red adonitol broth. The inoculated tube is incubated at 35-37 C for 24 hours and the results are determined. A positive test consists of a color change from red to yellow, indicating a pH change to acidic.
What reagents are added?
Performing this test in the VUMIE Online lab
Inoculation of Medium
1. Select the phenol red adonitol broth medium.
2. Complete the process of a tube-to-tube aseptic transfer to inoculate the medium. Forgotten how to do these things? Watch the “Show Me How To” videos.
Incubation of the Inoculated Medium
3. Place the inoculated tube into the 35-37 C incubator.
Determination of Test Results
5. Incubate this test for only 24 hours.
6. Retrieve the incubated culture from the incubator.
7. No reagents are required for completion of this test.
8. Positive tests will be yellow; negative results are any other color.
9. Record test result. Forgotten how to do these things? Watch the “Show Me How To” videos.