مکانیسم آزمایش VP (وژز اسکوئرر)
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Voges–Proskauer (VP) Test

Principle :
The VP test detects acetoin (acetyl methyl carbinol), an intermediate produced during 2,3-butanediol fermentation of glucose. In the presence of α-naphthol, potassium hydroxide (KOH), and oxygen, acetoin is oxidized to diacetyl, which reacts with guanidine compounds in the medium to produce a cherry-red color.

Results:

* ✅ Positive: Cherry-red color
* ❌ Negative: No red color (yellow or copper/brown)

Examples of VP-positive bacteria:

* Enterobacter cloacae
* Klebsiella pneumoniae
* Serratia marcescens
* Hafnia alvei