5 Jan 2012

VOGES - PROSKAUER TEST


VOGES - PROSKAUER TEST

This test is occasionally used to assist in the differentiation of enterobacteria. K.Pneumoniea, Vibrio cholerae and some strains of  Enterobacter, ferment glucose with the production of acetylmethylcarbinol ( acetoin ) which can be detected by an oxidation reaction.
PRINCIPLE:
The test organism is cultured in a glucose phosphate peptone water for 48 hrs. Sodium hydroxide and a small amount of creatine are then added. Under alkaline conditions and exposure to the air, the acetoin produced from the fermentation of the glucose is oxidized to diacetyl which forms a pink compound with the creatine.

REQUIREMENTS:

GLUCOSE PHOSPHATE PEPTONE WATER:

Glucose phosphate peptone water is a fluid medium used in the Vogues-Proskauer test and Methyl Red test.
Formula and Preparation ---------     To make about 50 bottles
Peptone………………………………………….0.5g
Glucose (dextrose)……………………………    0.5g
Di-Potassium hydrogen phosphate………           0.5g
Distilled Water………………………………….100ml.

a.      Dissolve the peptone and phosphate salt in the water by steaming. When cool, filter,       and adjust the pH to 7.5.
b.      Add the glucose and mix well.
c.       Dispense the medium in 2 ml amounts in small screw-cap tubes or bottles.
d.      Sterilize by autoclaving (with caps loosened) at 115oC for 10 minutes. When cool,            tighten the container tops.

Sodium hydroxide, 400g/l.
Creatine powder.

METHOD ;
1.         Inoculate 2 ml of sterile glucose phosphate peptone water with the test organism. Incubate at 35-37 oC for 48 hrs.
2.         Add a very small amount (knife point) of creatine and mix.
3.         Add about 3 ml of the sodium hydroxide reagent and shake well. The sodium hydroxide reagent is corrosive, therefore handle with care and do not mouth- pipette.
4.         Remove the bottle cap, and leave for 1 hour at room temperature. Look for the slow development of a pink-red color.

RESULTS:

Pink-red color………………………  Positive test (Acetoin produced)
No pink-red color……………………Negative test  (No acetoin produced)


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