Voges–Proskauer test

Enterobacter cloacae Voges-Proskauer test

Cosenzaea myxofaciens Voges-Proskauer test

Voges–Proskauer test

The Voges–Proskauer test (VP test) is a biochemical test used to detect the presence of acetoin in a bacterial broth culture. It is one of the series of tests known as the IMViC tests, which are used to differentiate between members of the family Enterobacteriaceae.

Principle

The Voges–Proskauer test is based on the detection of acetoin, a neutral end product of glucose metabolism. When bacteria ferment glucose via the butanediol pathway, acetoin is produced. The test involves adding specific reagents to the bacterial culture, which react with acetoin to produce a red color, indicating a positive result.

Procedure

1. Inoculate a tube of MR-VP broth with the test organism. 2. Incubate the tube at 35-37°C for 24-48 hours. 3. After incubation, add 0.6 mL of 5% alpha-naphthol (Barritt's reagent A) and 0.2 mL of 40% potassium hydroxide (Barritt's reagent B) to the culture. 4. Shake the tube gently to mix the reagents. 5. Allow the tube to stand for up to 60 minutes. 6. Observe the color change. A red color indicates a positive result, while no color change or a copper color indicates a negative result.

Interpretation

- Positive result: Development of a red color within 60 minutes indicates the presence of acetoin, suggesting that the organism ferments glucose via the butanediol pathway. - Negative result: No color change or a copper color indicates the absence of acetoin, suggesting that the organism does not ferment glucose via the butanediol pathway.

Applications

The Voges–Proskauer test is primarily used in the identification and differentiation of Enterobacteriaceae and other Gram-negative bacteria. It is particularly useful in distinguishing between Escherichia coli (VP-negative) and Enterobacter species (VP-positive).

Related Pages

• IMViC
• Methyl red test
• Enterobacteriaceae
• Escherichia coli
• Enterobacter