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20 Cards in this Set
- Front
- Back
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Which test MR or VP would be more likely to produce more false negatives w/ a shorter incubation time? Why? |
VP, b/c it requires a longer incubation time in order to allow the organism run it’s metabolism. |
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Which test (VP or MR) would likely benefit most from a longer incubation time? Why? |
VP, b/c it would allow the organism to build up acetone |
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Would a false negative result for VP more likely be attributable to poor sensitivity or to poor specificity of the system? |
A false negative result attributes to poor sensitivity |
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Why were you told to shame the VP tubes after the reagents were added? |
We needed oxygen b/c color changes better in the presence of oxygen. |
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Why is the methyl red test read immediately after addition of methyl red reagent & the VP read up to 60 mon after addition of VP reagents A & B? |
MR changes color immediately telling us rather it’s basic or acidic. VP takes awhile to chemically react & produce a result, which is why we gave it some time. |
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Some microbiologists recommend reincubating organisms producing methyl red-negative results for an additional 2 to 3 days. Why do you think this is done? |
It gives the organism enough time to lower pH in order to ensure you don’t produce a false negative result. |
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An organism that produces a red result for MR test allows us to interpret that.. |
It performed a mixed acid fermentation |
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What’s the symbol for a red MR test result? |
+ |
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What’s the symbol for a no color change result for MR test? |
- |
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If an organism displays no color change from MR test we can interpret that.. |
It doesn’t perform mixed acid fermentation |
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If an organism produces a red result from VP test we can interpret that.. |
It performed a 2,3 butanediol fermentation (produced acetone) |
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What’s the symbol used for a red VP test result? |
+ |
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What’s the symbol used for a no color change result from VP test? |
- |
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If an organism produces no color change during VP test we can interpret that.. |
It doesn’t perform 2,3 butanediol fermentation (acetone is not produced) |
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Methyl red is red at what pH? |
pH 4.4 |
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Methyl red is yellow at what pH? |
pH 6.2 |
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What is the MR test used for? |
To detect if an organism is capable of mixed acid fermentation. |
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What is the VP test used for? |
To identify organisms capable of fermenting glucose w/ the production of acetone |
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What are the products of the VP test? |
Acetone |
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What are the products of the MR test? |
H2 & Co2 gas |
