IMVIC TEST PROCEDURE PDF

Tryptophan is hydrolysed by tryptophanase to produce three possible end products — one of which is indole. Indole Test Reaction Indole test is a commonly used biochemical test e. Indole test helps to differentiate Enterobacteriaceae and other genera. Inoculate the tryptophan broth with broth culture or emulsify isolated colony of the test organism in tryptophan broth. Add 0. Photo Courtesy: Karen M.

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A Methyl Red Test is a procedure that checks the ability of the microbe to perform mixed acids fermentation in the presence of glucose, which helps in differentiating enteric bacteria.

It is also used to characterize other bacteria groups such as Actinobacteria. Picture Source: microbiologyinfo. Photo Source: slideplayer.

Some group of bacteria can use glucose and convert it to stable acids such as lactic acid, formic acid, and acetic acid. It metabolizes glucose to pyruvic acid and further metabolized through mixed acid pathway until such time it reaches the stable acid state. The type of acid produced will be determined by the species of an organism and the enzymatic pathway.

The acid produced by the organism can significantly affect the pH level. It causes a drop in the pH level 4. Picture Source: i Photo Source: i. The color of methyl red changes from yellow to red if the bacteria being tested has the ability to use glucose and produce a stable acid. The media and reagents used for the methyl red test procedure include the following: MRVP broth glucose, buffered peptone, and dipotassium phosphate Methyl red solution 0.

Inoculate two tubes that contain MR-VP broth containing a pure culture of the organism being tested. Before inoculation, make sure you allow the medium to equilibrate at a room temperature. Incubate at 35 to 37 degree Celsius for 24 hours or up to four days. Add five drops or at least 1 ml of methyl red indicator solution to the test tube. Re-incubate the remaining broth for at least 24 hours and add at least three drops of methyl red indicator. Observe for any changes in the color.

Examples of methyl red positive organisms are Escherichia, Proteus E. This is because less acid is produced during the fermentation of glucose. Examples of methyl red negative organisms are Enterobacter and Klebsiella.

Further biochemical tests need to be performed on pure culture so as to completely identify the organism. The medium to be tested using the methyl red test should be incubated for at least 48 hours. Doing the test too early would lead to a false positive result.

A light inoculum should be used. A too heavy inoculum will inhibit bacterial growth which could lead to invalid results. An incubation period of up to five days is necessary.

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IMVIC Test

Do not alter the pH. Solution B is prepared by dissolving 16 gms of potassium hydroxide in mL of water. Inoculate the tubes with the bacterial culture. Pipette 1 mL from each culture tube into clean separate tubes. Use separate pipettes for each tubes.

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Indole Test: Principle, Procedure and results

Procedure of Indole Test Take a sterilized test tubes containing 4 ml of tryptophan broth. Inoculate the tube aseptically by taking the growth from 18 to 24 hrs culture. Add 0. Observe for the presence or absence of ring. With an inoculating loop or wooden applicator stick, pick a portion of an hour isolated colony from a non-selective media and rub it onto the reagent saturated area of the filter paper.

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IMViC Tests: Principle, Procedure and results

A Methyl Red Test is a procedure that checks the ability of the microbe to perform mixed acids fermentation in the presence of glucose, which helps in differentiating enteric bacteria. It is also used to characterize other bacteria groups such as Actinobacteria. Picture Source: microbiologyinfo. Photo Source: slideplayer. Some group of bacteria can use glucose and convert it to stable acids such as lactic acid, formic acid, and acetic acid. It metabolizes glucose to pyruvic acid and further metabolized through mixed acid pathway until such time it reaches the stable acid state. The type of acid produced will be determined by the species of an organism and the enzymatic pathway.

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IMViC Tests

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