IMVic (Indole, Methyl Red, Voges-Prokauer, and Cietrate) Reactions Name_________
ID: 256359 • Letter: I
Question
IMVic (Indole, Methyl Red, Voges-Prokauer, and Cietrate) Reactions
Name___________________________________________________________ Date _________________________
Record your results after incubation in the table.
SIM
MRVP
Citrate
Organism
Sulfide
(+ or -)
Indole
(+ or -)
Motility
(+ or -)
MR
(+ or -)
VP
(+ or -)
Slant
Color
Citrate
(+ or -)
Salmonella
typhimurium
NA
NA
NA
NA
Escherichia
coli
Enterobacter
aerogenes
NA
NA
NA
Klebsiella
pneumonia
NA
NA
NA
NA
Interpretation and Questions:
The IMViC tests are based on some enzymatic/physiological process. Name the substrates for the enzymes in the indole, MRVP reactions, and citrate test.
Is it possible for an organism to be MR+ and VP+? Why or why not?
Why is it important to inoculate only a single tube per organism when performing the MRVP test?
During lab, your lab partner bumps into your, jostling your arm while you are inoculating your SIM tube. Is it still possible to reliably evaluate the sulfide, indole, and motility results from this tube? Which reactions will still be accurate?
The case study describes a cluster of food poisoning incidences. If the causative agent is Salmonella spp., then give your prediction of the IMViC test results.
SIM
MRVP
Citrate
Organism
Sulfide
(+ or -)
Indole
(+ or -)
Motility
(+ or -)
MR
(+ or -)
VP
(+ or -)
Slant
Color
Citrate
(+ or -)
Salmonella
typhimurium
NA
NA
NA
NA
Escherichia
coli
Enterobacter
aerogenes
NA
NA
NA
Klebsiella
pneumonia
NA
NA
NA
NA
Explanation / Answer
It is a group of individual test used in microbiology lab for the identification of organism of coliform group. Here I stands for indol test, M for methyl red test, Vi for Voges- Proskauer test and C for citrate test.
In indole test , Tryptophan is a substrate that is catalyzed by tryptophanase and converted to indole molecule. , ammonium and pyruvate. Indole then extracted from broth by means of xylene. To test indole production , kovac reagent added after incubation which gives pink/ red layer on the top of liquid in the presence of indole.
For methyl red (MR) and vogos-proskeur (VP) test use same broth for bacterial growth. This broth is called MRVP broth. MR test uses glucose as a substrate and detect acid production during metabolism using mixed acid fermentation pathway. pH indicator dye (methyl red) is used to check whether test is positive or negative. Red colour means lower pH and test is positive ( acid production is present).
For VP test uses alpha -naphthol and potessium hydroxide to detect the presence of acetyl methyl carbinol. The substrate is glucose and enzyme is 2,3 butandiol in this test. After adding both reagents, shake the tube vigrously and settle for 5 min and then appearance of pink/red colour show positive results. yellow means negative test.
Citrate test uses citrate as a substrate. this test is used to check ability of microorganism to utilize citrate as a sole carbon source. Bromothymal blue is used as a indicator. Citrate agar is green before incubation and turn blue if the test is positive means citrate is utilized.