Voges–Proskauer / / or VP is a test used to detect acetoin in a bacterial broth culture. The test is performed by adding alpha-naphthol and potassium hydroxide to the Voges-Proskauer broth which has been inoculated with bacteria. A cherry red color indicates a positive result, while a yellow-brown color indicates a negative result.
The test depends on the digestion of glucose to acetylmethylcarbinol. If glucose is being broken down, it will react with alpha-naphthol (VP reagent #1) and potassium hydroxide (VP reagent #2) to form a red color. Alpha-naphthol and potassium hydroxide are chemicals that detect acetoin.
Procedure: First, add the alpha-naphthol; then, add the potassium hydroxide. A reversal in the order of the reagents being added may result in a weak-positive or false-negative reaction.
VP is one of the four tests of the IMViC series, which tests for evidence of an enteric bacterium. The other three tests include: the indole test [I], the methyl red test [M], and the citrate test [C].
- MacFaddin, J. F. 1980. Biochemical Tests for Identification of Medical Bacteria, 2nd ed. Williams and Wilkins, Baltimore
- Bachoon, Dave S., and Wendy A. Dustman. Microbiology Laboratory Manual. Ed. Michael Stranz. Mason, OH: Cengage Learning, 2008. Exercise 15, "Normal Flora of the Intestinal Tract" Print.
- Bergey's Manual of Systematic Bacteriology, Vol. 1. Baltimore, Williams and Wilkins, 1984.