MIU test for bacteria :Introduction, Test procedure and Result-Interpretation

MIU Test for Bacteria: Introduction,Test procedure and Result Interpretation

Introduction of MIU Test

MIU test stands for motility indole urease test uses for three tests among them one for motility of bacteria, second for indole formation and third for urea hydrolyzation test of bacteria as shown above image. This test is useful for the identification of gram-negative bacilli especially bacteria of Enterobacteriaceae. Three tests in a single tube that helps to differentiate the organisms on the basis of motility, indole, and urease production.

Requirements for MIU Test

Test organisms (Gram-negative bacilli)
MIU test medium
Inoculating wire
Bunsen burner
Incubator

Quality control strains

Escherichia coli ATCC 25922
Klebsiella pneumoniae ATCC 13883
Proteus mirabilis ATCC 25933

Test Procedure for MIU Test

Take a well-isolated single colony with an inoculating needle and stab the medium leaving 1/3 part from the bottom of a tube.
Use a loose-fitting cotton plugin as a test tube.
Incubate at 37°C for 18-24 hours.
Repeat steps 1 to 3 for all quality control strains i.e. Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13883, and Proteus mirabilis ATCC 25933.

Observation of MIU Test

Observe the tube for growth, motility, and color change of the medium. Only check indole formation taking a reading of motility and urease reaction. Urease test positive– A color change from yellow–orange to pink-red. No color change indicates a negative reaction. Motility test – A positive reaction is shown by clouding of the medium or by growth extension from the inoculating line. A negative reaction is seen when the growth is restricted to the inoculating line. Indole test positive– Record as Indole Positive Reaction if a pink-red color ring appears in a test tube upon addition of Kovac’s reagent and as Indole Negative if there is no color.

Result and Interpretation of MIU Test

Motility test positive: a diffuse zone of growth flaring from the line of inoculation

Motility test Negative: restricted growth along the stab line

Indole test positive: a pink to red color ring is formed at the top of the medium after the addition of Kovac’s reagent

Indole test negative: A yellow color denotes a negative indole test after the addition of Kovac’s reagent

Urease test positive: A color change from yellow-orange to pink-red

Urease test negative: No color change indicates a negative reaction

Escherichia coli ATCC 25922

Motility test: Positive, Indole test: positive, and Urease test: negative

Klebsiella pneumoniae ATCC 13883

Motility test: Negative, Indole test: negative, and Urease test: weakly positive

Proteus mirabilis ATCC 25933

Motility test: positive, Indole test: negative, and Urease test: positive

Keynotes on MIU Test

Urea test or urease test or urea hydrolyzation test for bacteria is the same thing.
The motility and urease reactions are read before testing Indole production.
The medium is heat-sensitive. No further sterilization is necessary or desirable.

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