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| Imvic Testing |
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- Methyl red test
- Voges-Proskauer test
- Citrate utilization test
Inorde to obtain the results of these four tests, three test tubes are inoculated viz tryptone broth (indole test), methyl red – Voges Proskauer broth (MR-VP broth), and citrate.
IMViC tests are used in identification and differentiation of some enterobacteriaceae members.
Procedure required for performing IMViC Tests and their interpretations
Culturing of enterobacteriaceae for 24 to 48 hours at 37°C inorder to performed these respective test
Inorde to obtain the results of these four tests, three test tubes are inoculated viz tryptone broth (indole test), methyl red – Voges Proskauer broth (MR-VP broth), and citrate.
IMViC tests are used in identification and differentiation of some enterobacteriaceae members.
Procedure required for performing IMViC Tests and their interpretations
Culturing of enterobacteriaceae for 24 to 48 hours at 37°C inorder to performed these respective test
Indole Test
It is performed either on sulfide-indole-motility (SIM) medium or in tryptophan broth, or in motility urease indole (MIU) medium. The Result is read after adding Kovac’s reagent.
- The positive result is indicated by the red layer at the top of the tube after the addition of Kovács reagent.
- A negative result is indicated by the lack of color change at the top of the tube after the addition of Kovács reagent.
Also read IMViC Indole Test Method principle, procedure, Observation and interpretation
The Methyl red test and Voges-Proskauer test are both done in methyl red–Voges-Proskauer (MR-VP) broth, but there is a variation in the reagents that are being added.
Methyl Red (MR)Test:
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| Methyl red test |
- Positive methyl red test are indicated by the development of red color after the addition of methyl red reagent.
- A negative methyl red test is indicated by no color change after the addition of methyl red reagent
Voges-Proskauer (VP) test:
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| voges proskauer |
- Negative test is indicated by lack of color change after the addition of Barritt’s A and Barritt’s B reagents.
- A positive Voges-Proskauer test is indicated by the development of red-brown color after the addition of Barritt’s A and Barritt’s B reagents.
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| citrate utilization test |
This test is performed on Simmons citrate agar:
- Negative citrate utilization test is indicated by a lack of growth and color change in the tube
- While A positive citrate result as indicated by growth and a blue color change.
Below are IMViC Test results of Some Genera of Enterobacteriaceae:
IMViC tests of Escherichia coli
- Indole: Positive
- Methyl-Red: Positive
- Voges-Proskauer test: Negative
- Citrate test: Negative
IMViC tests of Enterobacter aerogenes
- Indole: Negative
- Methyl-Red: Negative
- Voges-Proskauer test: Positive
- Citrate test: Positive
IMViC tests of Proteus vulgaris
- Indole: Positive
- Methyl-Red: Positive
- Voges-Proskauer test: Negative
- Citrate test: Negative
IMViC tests of Citrobacter freundii
- Indole: Negative
- Methyl-Red: Positive
- Voges-Proskauer test: Negative
- Citrate test: Positive
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