Identification Tests for Gram Negative Bacteria

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

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

What is the positive result for the indole test?

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

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

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).

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.