IMViC Flashcards
(19 cards)
What is the purpose of the indole Test?
5-20: Indole Production Test
To test if bacteria have the tryptophanase enzyme.
What is the Medium, Reagent, Positive, and Negative?
5-20: Indole Production Test
Medium: Tryptone broth (contains tryptophan).
Reagent: Kovac’s reagent
Positive result: Red/pink layer on top after adding Kovac’s.
Negative result: No color change (or yellow layer).
Why isn’t a pH indicator used in indole test?
5-20: Indole Production Test
Because break down of tryptophan results in acid (pyruvate) and base (NH3)
What is the purpose of the Methyl Red Test?
5-4: MRVP
To detect mixed acid fermentation
What is the Medium, Reagent, Positive, and Negative?
MR
5-4: MRVP
Medium: MR-VP broth.
Reagent: Methyl red indicator.
Positive result: Red color (pH < 4.4).
Negative result: Yellow/orange (pH > 6.0).
What is the purpose of the VP test?
5-4: MRVP
To test is acetoin was produced due to glucose fermentation.
What is the Medium, Reagent, Positive, and Negative?
VP
5-4: MRVP
Medium: MR-VP broth (same as MR test).
Reagents: VP-A (alpha-naphthol) and VP-B (KOH).
Positive result: Red color (after 15–30 min).
Negative result: No color change or copper/brown.
What is the purpose of the citrate utilization test?
5-9 Citrate Utilization
To deterimine if bacteria can utilize citrate as a sole carbon source.
What is the Medium, Positive, and Negative?
5-9 Citrate Utilization
Medium: Simmons citrate agar (contains citrate and bromothymol blue).
Positive result: Blue color (alkaline pH shift), or green with growth
Negative result: Green (no growth or pH change).
What is the purpose of the PR broth test?
5-3 Phenol Red Broth
To determine what sugars can be fermented by a bacteria
What is the Medium, Positive, and Negative?
5-3 Phenol Red Broth
Medium: Phenol Red Broth
Positive: Yellow indicates fermentation occured resulting in pH decreasing (Turbid)
Negative: Pink/orange indicates Peptones (turbid)
Inconclusive: Orange
Why must the interpretation occur between 24-48 hours?
Because eventually the bacteria expend the sugar and must use peptones to survive leading to pH to bounce and become alkaline
What is the purpose of the OF test?
5-2: OF Test
Determine whether bacteria oxidize and/or ferment glucose
What is the Medium, Positive, and Negative?
5-2: OF Test
Medium: Agar deep
Positive: Yellow indicates glucose was metabolized
Negative: Green/Blue indicates glucose was not fermented/peptones were fermented
What is the importance of wheather glucose is metabolized or not metabolized?
5-2: OF Test
It shows us the bacteria’s capacity to metabolize glucose as well as understand the oerobic needs of the bacteria
strict oxidizer, facultative anaerobe, non-ox/fer = nonsacc
What is the purpose of the decarboxylase test?
5-11: Decarboxylase
To determine if bacteria can decarboxylate lysine or ornithine
What is the Medium, Positive, and Negative?
5-11: Decarboxylase
Medium: Lysine/ornothine broth
Positive: Broth initially turned yellow from glucose fermentation, then returned to purple as decarboxylation of lysine or ornithine produced alkaline amines (cadaverine/putrescine), raising the pH.
Negative: Broth remained yellow, indicating fermentation occurred but no decarboxylation of lysine or ornithine took place.
What is the purpose of the phenylalanine deaminase test?
5-12: Phenylalanine Deaminase
To determine if bacteria can deaminate phenylalanine
What is the Medium, Reagent, Positive, and Negative?
5-12: Phenylalanine Deaminase
Medium: Phenylalanine slant
Reagent: Ferric Chloride is phenylpyruvic acid indicator
Positive: Green as phenylpyruvic acid and ferric chloride turns green
Negative: Yellow as no phenylpyruvic acid was produced
