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Questions and Answers
What does the blue color in the Simmons' citrate agar slants indicate?
What does the blue color in the Simmons' citrate agar slants indicate?
Why do we use Simmons' citrate agar slants for the citrate test instead of other growth media?
Why do we use Simmons' citrate agar slants for the citrate test instead of other growth media?
What is the purpose of the pH indicator bromothymol blue in Simmons' citrate agar slants?
What is the purpose of the pH indicator bromothymol blue in Simmons' citrate agar slants?
Why does the pH indicator turn blue during a positive citrate test?
Why does the pH indicator turn blue during a positive citrate test?
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What happens when bacteria oxidize citrate in Simmons' citrate agar slants?
What happens when bacteria oxidize citrate in Simmons' citrate agar slants?
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Why is it crucial to label each Simmons' citrate agar slant with the bacterium's name and date?
Why is it crucial to label each Simmons' citrate agar slant with the bacterium's name and date?
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What does a green color of the medium in Simmons' citrate agar slants indicate?
What does a green color of the medium in Simmons' citrate agar slants indicate?
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Why is it recommended to incubate the Simmons' citrate agar slants at 37ºC?
Why is it recommended to incubate the Simmons' citrate agar slants at 37ºC?
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Study Notes
IMVIC Test
- Objective:
- Understand how some bacteria degrade the amino acid tryptophan
- Differentiate between glucose-fermenting enteric bacteria
- Determine the ability of some bacteria to oxidize glucose with the production of acid end products
- Differentiate among enteric bacteria on the basis of their ability to ferment citrate
Enterobacteriaceae
- Enteric (intestinal) bacteria, found in the intestines of humans and other mammals
- Family Enterobacteriaceae includes pathogens like Salmonella, Proteus, Escherichia, and Shigella
- Differentiation and identification of these enteric bacteria can be accomplished by using the IMViC test
Indole Production (I)
- Tryptophan is an amino acid found in nearly all proteins
- Bacteria containing the enzyme tryptophanase can hydrolyze tryptophan to indole, pyruvic acid, and ammonia
- Kovacs' reagent detects indole production, resulting in a bright red compound
- Indole positive: red layer following addition of Kovacs' reagent
- Indole negative: absence of a red color
Methyl Red Test (MR)
- All enteric bacteria catabolize glucose for energy needs
- Methyl red detects pH change to the acid range as a result of acidic end products like lactic, acetic, and formic acids
- pH 4: methyl red indicator turns red, positive test
- pH 6: methyl red indicator turns yellow, negative test
Voges-Proskauer Test (VP)
- Identifies bacteria that ferment glucose, leading to 2,3-butanediol accumulation
- Barritt's reagent detects the presence of acetoin, a precursor in the synthesis of 2,3-butanediol
- Positive VP test: cherry red color within 15 minutes
- Negative VP test: absence of a red color
Citrate Utilization Test
- Determines the ability of bacteria to use citrate as a sole carbon source for energy needs
- Citrate permease facilitates transport of citrate into the bacterium
- Citrate utilization leads to CO2 production, which combines with sodium and water to form an alkaline product
- Positive citrate test: blue color due to raised pH
- Negative citrate test: absence of a color change, green color
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Description
This quiz covers the IMVIC test in the Medical Bacteriology Laboratory Practical 2 at Al-Bayan University College Of Health and Medical Techniques. Topics include understanding how bacteria degrade tryptophan, differentiating between glucose-fermenting enteric bacteria, and determining the ability of bacteria to oxidize glucose.
