ex 8: IMViC TEST Flashcards
What is the purpose of the IMVIC test
seperate various types of coliform ESP escherichia coli and Enterobacter aerogenes
what does each letter stand for
I: Indole production
M: Methyl red test
Vi: Voges-Proskauer reaction (production of acetylmethylcarbinol)
C: Citrate utilization as only carbon source
What are the common results of this test
E.Coli: ++–
enterbacter aerogenes: –++
Indole test
uses truptone broth rich in tryptophane
-test differentiates the organisms that can seperate the indole ring from the tryptophan from those that cant, because these orgs that can contain the enzyme tryptophanase which catalyze thehydrolysis of it to indole, pyruvic acid and ammonia
kovacs reagent forms a red ring when combined with the indole ring (ammonia and pyruvate are used by the org)
Methyl red test
-peptone water with small amount ofglucose is used,
ecoli ferments the glucose into acid products
other organisms turn it into other things like butylene glycol, they just take out the glucose, attack the peptone releasing ammonia and make a more basic environemnt,
therefore methyl red is added to test the pH of it
hat is methyl red red below
4.5 (pos result), yellow above 4.5
Voges Proskauer test
tests for acetylmethylcarbinol (acetoin) from sugar fermentation
-add 6 drops alcoholic alpha-naphthol and 3 drpps KOH
-shake and allow to rest at room temp for 20 mins
pos is red colour, neg is brown
Citrate test
-tests for only sodium citrate as the carbon source
-if they can use it, they shift the pH to basic side, so it becomes (thebromomythol blue) blue
if not, it remains green
Citrobacter Freundii results
- +-+
