Identification Tests for Gram Negative Bacteria
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Questions and Answers

What is the purpose of the ammonia test using phenol red?

  • To detect the presence of indole
  • To test an organism's ability to produce indole from tryptophan
  • To detect a change in pH caused by ammonia (correct)
  • To determine the ability of an organism to ferment glucose

    • What is the end product of glycolysis tested in the glucose fermentation with Durham tubes?

  • Formic acid
  • Ammonium ion
  • H2 and CO2 gas (correct)
  • Pyruvate

    • What is the positive result for the indole test?

  • Deep pink color in the tryptophan broth
  • Yellow color in the tryptophan broth
  • Presence of a red color on the surface of the broth (correct)
  • Appearance of gas bubbles at the top of the tube

    • What indicates a positive result for H2S production in Kliger’s Iron Agar (KIA) test?

    <p>Formation of a black precipitate in the medium</p> Signup and view all the answers

    What is the purpose of Kliger’s Iron Agar (KIA) test?

    <p>To identify sulfur reducers and test carbohydrate fermentation abilities</p> Signup and view all the answers

    Study Notes

    Identification of Gram Negative Bacteria

    • Various tests are employed to identify Gram negative bacteria in a laboratory setting.
    • Tests include Oxidase Test, Urease Test, Indole Test, Sugar broth with Durham tubes, Kliger’s Iron Agar (KIA), Simmon’s Citrate Agar, Methyl Red Test, Voges-Proskauer Test, and Nitrate Broth.
    • API System Test and automated identification systems, like Vitek-2 Compact, are also used for biochemical identification.

    Oxidase Test

    • Identifies microorganisms that possess the enzyme cytochrome oxidase.
    • Procedure involves saturating filter paper with tetramethyl-p-phenylenediamine dihydrochloride dye.
    • Bacterial colonies are transferred onto the filter paper to observe color change within 10 seconds.
    • A deep purple or violet color indicates a positive result, while colorless indicates a negative result.
    • False positives can occur due to contaminating ions; transferring bacteria with a toothpick mitigates this risk.

    Urea Hydrolysis Test

    • Used to identify bacteria that can hydrolyze urea using the enzyme urease.
    • Urease catalyzes the breakdown of urea into ammonia (NH3) and carbon dioxide (CO2).

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    Description

    Test your knowledge of the biochemical and antimicrobial susceptibility tests used to identify Gram Negative Bacteria in practical medical microbiology. This quiz covers important tests such as Oxidase, Urease, Indole, Sugar broth with Durham tubes, Kliger’s Iron Agar, Simmon’s Citrate Agar, and more.

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