IMViC Tests Overview

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Questions and Answers

What is the acronym for IMViC?

  • Indole, Methyl Red, Voges-Proskauer, Ethanol Production
  • Indole, Methyl Red, Ester Test, Citrate Utilization
  • Indole, Methyl Red, Voges-Proskauer, Carbon Utilization
  • Indole, Methyl Red, Voges-Proskauer, Citrate Utilization (correct)

Why is the IMViC test used?

Because it is a fast, inexpensive way to distinguish between most enteric bacteria.

What are the IMViC tests frequently used for?

To check for the possibility of fecal contamination of food or water supplies.

What bacteria is associated with fecal contamination?

<p>Escherichia coli.</p> Signup and view all the answers

What bacteria is associated with soil?

<p>Enterobacter aerogenes.</p> Signup and view all the answers

What is E. coli positive for in the IMViC tests?

<p>Indole, methyl red.</p> Signup and view all the answers

What is E. coli negative for in the IMViC tests?

<p>Voges-Proskauer, citrate utilization.</p> Signup and view all the answers

What is E. aerogenes positive for in the IMViC tests?

<p>Voges-Proskauer, citrate utilization.</p> Signup and view all the answers

What is E. aerogenes negative for in the IMViC tests?

<p>Indole, methyl red.</p> Signup and view all the answers

What color is a positive Indole test?

<p>red</p> Signup and view all the answers

What color is a negative Indole test?

<p>yellow</p> Signup and view all the answers

What color is a positive Methyl Red test?

<p>red</p> Signup and view all the answers

What color is a negative Methyl Red test?

<p>yellow</p> Signup and view all the answers

What color is a positive Voges-Proskauer test?

<p>pink</p> Signup and view all the answers

What color is a negative Voges-Proskauer test?

<p>no color</p> Signup and view all the answers

What color is a positive Citrate Utilization test?

<p>blue</p> Signup and view all the answers

What color is a negative Citrate Utilization test?

<p>green</p> Signup and view all the answers

_____ is a component of the amino acid tryptophan.

<p>Indole</p> Signup and view all the answers

When tryptophan is broken down, the presence of indole can be detected through the use of _________.

<p>Kovac's reagent</p> Signup and view all the answers

What color is Kovac's reagent?

<p>yellow</p> Signup and view all the answers

Kovac's reagent reacts with indole to produce a _____ color on the surface of the broth in the test tube.

<p>red</p> Signup and view all the answers

What family does the IMViC test distinguish between?

<p>Enterobacteriaceae.</p> Signup and view all the answers

What media is used for the Indole test?

<p>Tryptone broth.</p> Signup and view all the answers

What media is used for the Methyl Red test?

<p>MRVP broth.</p> Signup and view all the answers

What media is used for the Voges-Proskauer test?

<p>MRVP broth.</p> Signup and view all the answers

What is the Methyl Red test used for?

<p>To detect whether the environment has been acidified to a pH below 5.</p> Signup and view all the answers

At what pH does Methyl Red change red?

<p>5 or below.</p> Signup and view all the answers

Organisms that lower the pH of the culture to 5 in a Methyl Red test are _____.

<p>positive</p> Signup and view all the answers

Organisms that do not lower the pH of the culture to 5 in a Methyl Red test are _____.

<p>negative</p> Signup and view all the answers

What does the Methyl Red test check for?

<p>Glucose fermentation.</p> Signup and view all the answers

What does the Voges-Proskauer test check for?

<p>It detects the presence of acetoin.</p> Signup and view all the answers

What is acetoin?

<p>One of the neutral products formed by bacteria that gives a negative Methyl Red test.</p> Signup and view all the answers

How is the VP test performed?

<p>By adding Barrit's reagent.</p> Signup and view all the answers

What does a Citrate Utilization test check for?

<p>The ability of organisms to use citrate as a carbon source.</p> Signup and view all the answers

What media is used for the Citrate Utilization test?

<p>Simmon's citrate agar.</p> Signup and view all the answers

What does bromthymol blue mean in the Citrate test?

<p>Increases the pH.</p> Signup and view all the answers

What does green mean in the Citrate test?

<p>The pH remains the same.</p> Signup and view all the answers

Flashcards

IMViC test

A group of tests used to quickly and cheaply distinguish different types of enteric bacteria.

Escherichia coli (E. coli)

A bacterium often found in fecal matter and can indicate fecal contamination.

Enterobacter aerogenes

A bacterium often found in soil environments.

Indole test

Checks for the presence of Indole, a substance derived from the breakdown of tryptophan.

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Methyl Red test

Identifies organisms capable of producing acidic byproducts during fermentation of glucose.

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Voges-Proskauer test

Checks for the production of acetoin, a compound formed during anaerobic glucose fermentation.

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Citrate Utilization test

Determines an organism's ability to use citrate as a carbon source for growth.

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Positive Indole

Produces a Red color during the Indole test.

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Negative Indole

Produces a Yellow color when using Kovac's reagent in Indole test.

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Positive MR

A red color in the Methyl Red test, indicating acidic byproduct formation from glucose.

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Negative MR

(Methyl Red) test results in a yellow solution, no significant acid production during glucose fermentation.

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Positive VP

(Voges Proskauer) test results in a Pink/red color when using Barrit's reagent after a period.

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Negative VP

No color change in the Voges-Proskauer test.

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Positive Citrate

(Citrate test) The culture turns a Blue color.

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Negative Citrate

The culture retains the initial color(not Blue), indicating no citric acid use.

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Kovac's reagent

A reagent used to detect the presence of Indole, changing color to Red in presence of Indole.

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Tryptone broth

A culture medium commonly used in the Indole test.

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MRVP broth

Culture medium for Methyl Red and Voges-Proskauer tests.

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Simmons citrate agar

A culture medium for citrate utilization tests.

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Barrit's reagent

Reagent used in the Voges-Proskauer test to detect acetoin.

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Study Notes

IMViC Tests Overview

  • Acronym IMViC stands for Indole, Methyl Red, Voges-Proskauer, and Citrate Utilization.
  • Used for distinguishing most enteric bacteria quickly and cost-effectively.
  • Frequently checks for fecal contamination in food or water, indicating hygiene levels.

Key Bacteria

  • Escherichia coli (E. coli): Commonly associated with fecal contamination.
  • Enterobacter aerogenes: Typically found in soil environments.

Test Results for E. coli

  • Positive results: Indole and Methyl Red.
  • Negative results: Voges-Proskauer and Citrate Utilization.

Test Results for E. aerogenes

  • Positive results: Voges-Proskauer and Citrate Utilization.
  • Negative results: Indole and Methyl Red.

Color Indicators in IMViC Tests

  • Indole test:
    • Positive: Red
    • Negative: Yellow
  • Methyl Red test:
    • Positive: Red
    • Negative: Yellow
  • Voges-Proskauer test:
    • Positive: Pink
    • Negative: No color
  • Citrate Utilization test:
    • Positive: Blue

Additional Information

  • Indole is a component derived from tryptophan.
  • Kovac's reagent is used to detect indole, producing a red color when reacting.
  • Kovac's reagent itself is yellow.

Test Media

  • Indole test: Tryptone broth is used.
  • Methyl Red test: MRVP broth is utilized.
  • Voges-Proskauer test: Also conducted in MRVP broth.
  • Citrate Utilization test: Simmon's citrate agar is employed.

Methyl Red Test Specifics

  • Detects if the pH lowers below 5, indicating glucose fermentation.
  • Organisms that acidify the culture to a pH of 5 are considered positive, while those that do not are negative.

Voges-Proskauer Test Specifics

  • Tests for the presence of acetoin, a neutral product from fermentation.
  • Conducted by adding Barrit's reagent to the culture.

Citrate Utilization Test Mechanism

  • Assesses the ability of organisms to use citrate as their carbon source.
  • Bromthymol blue indicates increasing pH during the test.
  • A green result indicates no change in pH.

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