Which genera are known to produce a positive VP reaction in MRVP testing?

Which genera are known to produce a positive VP reaction in MRVP testing?

• A. Escherichia
• B. Klebsiella
• C. Pseudomonas
• D. Bacillus

Answer: (B)

Voges-Proskauer tests look for acetoin production from glucose fermentation via the 2,3-butanediol pathway. When an organism makes acetoin, adding Barritt’s reagents (alpha-naphthol and KOH) produces a red color, signaling a positive VP reaction. Klebsiella species are classic VP-positive members of the Enterobacteriaceae; they commonly use the butanediol pathway to yield acetoin, so the test turns red. In contrast, Escherichia coli typically ferments to mixed acids and remains VP negative, while Pseudomonas and Bacillus are not standard VP-positive in this testing context. Thus, Klebsiella is the genera known to produce a positive VP reaction.

Voges-Proskauer tests look for acetoin production from glucose fermentation via the 2,3-butanediol pathway. When an organism makes acetoin, adding Barritt’s reagents (alpha-naphthol and KOH) produces a red color, signaling a positive VP reaction. Klebsiella species are classic VP-positive members of the Enterobacteriaceae; they commonly use the butanediol pathway to yield acetoin, so the test turns red. In contrast, Escherichia coli typically ferments to mixed acids and remains VP negative, while Pseudomonas and Bacillus are not standard VP-positive in this testing context. Thus, Klebsiella is the genera known to produce a positive VP reaction.