Study Set Content:
orange
neutral
Red
Acid
Methyl Red Test Positive
red colored broth (acidic)
Methyl Red Test Negative
No color change
red colored broth (acidic) means
Glucose fermenter
B. No color change means
Non-glucose fermenter
Applications:
E. coli =
+ (positive)
Klebsiella =
- (negative)
Voges-Proskauer Test
Principle/Inference (blank)Glucose fermenter – production of acid product (acetoin)
Barritt’s Method
Positive result
Red color complex
weakly positive
red orange
negative
Yellow
POSITIVE VP TEST
Acetoin production From pyruvic acid
Applications of VP test: Identification of
Klebsiella, bacillus, E. coli and other enterobacter
Citrate Utilization test Principle/Inference
When citrate gets consumed as an exclusive source of carbon it gives rise to an ultimate (blank) of the medium
alkalinization
When citrate gets consumed as an exclusive source of carbon it gives rise to an ultimate alkalinization of the medium indicating the presence of the enzyme
citrate permease
POSITIVE
Agar butt/slant
(Simmon Citrate Agar)
Citrate Utilization test positive
1. Prussian blue (alkaline)
Production of
carbonate/bicarbonate
Citrate utilization test negative
1. No color change
