Voges Proskauer (VP) Test- Principle, Procedure, Results, Uses

The VP test is a biochemical test that is used to differentiate two major types of facultative anaerobic enteric bacteria based on the production of neutral products from glucose fermentation.

The VP test is used to determine the ability of some organisms to produce neutral end products from glucose fermentation.

The medium used for the VP test is MRVP broth, which stands for methyl red and Voges-Proskauer broth.

1. Inoculate MRVP broth with a pure culture of the organism.
2. Incubate at 35°-37°C for a minimum of 48 hours in ambient air.
3. After incubation, observe the color of the broth.
4. To perform the VP test, add VP reagent I (alpha napthol) and VP reagent II (40% KOH) to the broth.
5. Observe for the color change in the broth medium within 10 to 60 minutes.

The result of the VP test is based on the color change of the broth medium after adding the VP reagents.

• The VP test may be used in the identification of gram-negative bacteria, but additional biochemical testing using pure culture is recommended for complete identification.
• Prolonged incubation of certain VP-positive strains may result in false-negative reactions.
• The order of the addition of reagents is extremely important.
• MR-VP testing should be used in conjunction with other confirmatory tests to differentiate organisms among the Enterobacteriaceae.

Quality control is essential to ensure the accuracy and reliability of the VP test results.

The VP test is used for identification to the species level of various groups of organisms, including enteric gram-negative rods, aquatic bacteria, viridans group streptococci, and staphylococci.

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