VP Test: A Microbiology Technique for Detecting Acetoin Production in Bacteria, Slides of Microbiology

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Name of the Student: SMITA D. Class- TY MICROBIOLOGY Under The Guidance of Chitra Nair

Sr

no

Name of apparatus volume Quantity

Media & Reagents

Sterile Glucose Phosphate Broth

5ml _

2 40 % Koh 2ml

_

3 Alpha Naphthol 2ml

_

4 Provided Sample 1ml

_

Miscellaneous

Nichrome Wire Loop

_ _

6 Incubator at 37 ◦C for 24 hrs

_ _

Protocol :

Inoculate loopful sample in sterile glucose phosphate broth.

Incubate it at 37 ◦c for 24 hrs.

Add 0.5 ml of 5% alpha naphthol ,0.2 ml 40% KOH Shake gently.

Allow to remain undisturbed

• Red color within 15

mins indicates

positive result

• Yellow color indicates

negative result

 Results of VP tests need to be used in conjunction with other

biochemical tests to differentiate genus and species within the Enterobacteriaceae.

 VP reagents must be added in the order.

 A weak-positive reaction may be masked by a copper-like color

which may form due to the reaction of KOH and a-naphthol.

 Read the VP test within 1 hour of adding the reagents. The KOH

and a-naphthol may react to form a copper-like color.

 Some organisms destroy acetoin, thereby rendering the VP tests

invalid.

 Shaking the tubes enhances the VP reaction.