Wowld s falue negative resslt for the VP test more likehy be attributable to poo

Question

Wowld s falue negative resslt for the VP test more likehy be attributable to poor sensitivity o of the test system? to poor specificity 3 Why were you told to shake the VP tubes after the reagents were addedr 5 4 Why is the methyl red test read immediately after addition of methyl red reagent and the Voges-Proskauer read up to 60 minutes after addition of VP reagents A and B microbiologists recommend reincubating organisms producimg methyl red-negative results for an additional 2 to 3 days. Why do you think this is donet

Explanation / Answer

2. Yes it may be due to poor specificity of test system.

3. Shaking is required for proper mixing of reagent in the broth as all the bacterium should react with it.

3. vP test includes the digestion of glucose to acetylmethyl carbinol. In the presence of strong base acerylmethylcarbinol oxidised into diacetyl.

In MR test the bacteria metabolise pyruvic acid and lowers the pH to 4.2. at this pH methyl red changes into red rapidly.

5. May be the growth of bacterium not occurs so much that they metabolically produce pyruvic acid and gives negative test.but after reincubation the metabolism gets active and ay be the test becomes positive.

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