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The color change to blue is useful because growth on Simmons' citrate agar is often limited and would be hard to observe if it were not for the color change. Sometimes, it is possible to detect growth on the Simmons' citrate agar without the accompanying color change to blue. This should be scored as a negative for the citrate use test. [12]
The term "IMViC" is an acronym for each of these tests. "I" is for indole test; "M" is for methyl red test; "V" is for Voges-Proskauer test, and "C" is for citrate test. The lower case "i" is merely for "in" as the Citrate test requires coliform samples to be placed "in Citrate". These tests are useful in distinguishing members of ...
Use of citrate involves the enzyme citrate lyase, which breaks down citrate to oxaloacetate and acetate. Oxaloacetate is further broken down to pyruvate and carbon dioxide (CO 2). Production of sodium bicarbonate (NaHCO 3) as well as ammonia (NH 3) from the use of sodium citrate and ammonium salts results in alkaline pH. This results in a ...
The TSI slant is a test tube that contains agar, a pH-sensitive dye , 1% lactose, 1% sucrose, 0.1% glucose, [2] and sodium thiosulfate and ferrous sulfate or ferrous ammonium sulfate. All of these ingredients are mixed together, heated to sterility, and allowed to solidify in the test tube at a slanted angle.
The plates are incubated for 12 hours up to several days, depending on the test that is performed. Commonly used types of agar plates include: Red blood cells on an agar plate are used to diagnose infection. On the left is a positive Staphylococcus infection, on the right a positive Streptococcus culture.
The spot indole test is used to determine if a microbe can deaminate tryptophan to produce indole. This test is performed by saturating a piece of filter paper with Indole Kovacs Reagent and scraping a portion of microbe onto the paper. A color to a pink-red color indicates a positive result while no color change indicates the lack of ...
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When inoculated with a sample organism and allowed to incubate, the medium will change color from red to yellow to indicate that the mannite has been fermented.