Each of the letters in “IMViC” stands for one of these tests. “I” is for indole; “M” is for methyl red; “V” is for Voges-Proskauer, and “C” is for citrate, lowercase “i” is added for the ease of pronunciation. IMViC is an acronym that stands for four different tests
To obtain the results of these four tests, three test tubes are inoculated: tryptone broth (indole test), methyl red – Voges Proskauer broth (MR-VP broth), and citrate. IMViC tests are employed in the identification/differentiation of members of the family Enterobacteriaceae.
General procedure for performing IMViC Tests and their interpretations:
Cultures of any members of Enterobacteriaceae have to grow for 24 to 48 hours at 37°C and the respective tests can be performed:
Table of Contents
Indole test
It is performed on sulfide-indole-motility (SIM) medium or in tryptophan broth, or in motility urease indole (MIU) medium. 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.
Methyl red test and Voges-Proskauer test both are done in methyl red–Voges-Proskauer (MR-VP) broth, but the reagents that are added varies according to the tests.
Methyl Red (MR) test
- Positive methyl red test is 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
- Negative VP test is indicated by a 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.
Citrate Utilization test
The test is performed on Simmons citrate agar:
- Negative citrate utilization test is indicated by the lack of growth and color change in the tube
- A positive citrate result is indicated by growth and a blue color change.
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 Klebsiella (formerly 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
Acharya Tankeshwar
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please email at microbeonline@gmail.comKeep Reading
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Hello Dr Acharya I’m glad to see your blog.Nice information.i have one query for u . Typhoid is quite common in our scenario.How can we pick this fever early as many fever start without systemic features.Although many of them r viral fevers.