IMVIC Flashcards
IMViC Tests- Help identify?
*Help identify enteric bacteria (bacteria found in the gut)
IMViC Tests- enteric bacteria can be
Pathogens
*Occasional pathogens
*Normal gut flora
IMVIC consiste of 4 tests
*Indole
*Methyl Red
*Vogues-Proskauer
*Citrate Utilization
Indole test is a product of
tryptophan hydrolysis
Indole test- Bacteria are grown in_______, which contains_______
Bacteria are grown in SIM agar, which contains trypotphan
Addition of Kovak’s reagent will turn indole
cherry red
What is kovak’s reagent made up of?
*, p-dimethylaminobenzaldehye, and HCl
Methyl Red is a pH indicator
what does red and yellow indicate?
*Red for solutions with a pH < 6.2
*Yellow for solutions with pH > 6.2
What does methyl red test for?
*The use of Methyl red is a test for glucose fermentation
*ONLY tests for acidic end products of fermentation.
What is the purpose of the vogues-Proskauer test? Give an example. What is the positive rxn? What is Barritt’s reagent made up of?
*Some organisms ferment glucose, but produce nonacidic or neutral end products
*Example: production of acetylmethylcarbinol by E. aerogenes
*Addition of Barrit’s reagent will turn the solution RED if non-acidic fermentation has occurred
*Barrit’s reagent = α-naphthol + 4%KOH
what are the reagents used in the VP test?
Acetylmethyl-carbinol + a-naphtol—-> products
Barrit’s reagent, diacetyl + (Guanidine + peptone)
What is the purpose of the urease test? what does urease break down? What is the indicator used and what color does it turn into?
*Identifies if a microorganism uses the enzyme urease
*Urease breaks down urea to produce ammonia, which is highly basic
*Used to identify Proteus species because catalyze urea breakdown faster than many other species
*Uses phenol red to determine if ammonia has been formed
*Turns PINK if solution is basic and Yellow if solution is acidic
When do organisms ferment citrate? Which enzymes are used? What does the media contain? Blue vs Green?
*Some microorganisms ferment citrate when lactic acid and glucose are not available
*2 enzymes must be available for this to occur
*A citrate permease to allow citrate into the cell
*Citrase to breakdown citrate to oxaloacetate and acetic acid
*Oxaloacetate is further broken down to pyruvate and CO2, making the medium alkaline
*Media containing bromothymol blue, a pH indicator, will become BLUE when citrate is utilized
*Media will stay GREEN if citrate is not utilized
What is the use of the Hydrogen Sulfide test? What does the media contain? What is the indicator?
*Determines if microorganisms are able to ferment thiosulfate
*Media contains peptone and and sodium thiosulfate, with FeSO4 as the H2S indicator
*FeSO4 combines with H2S gas to form an insoluble black ferrous sulfide precipitate
