lab tests Flashcards
what type pH test is able to hydrolyze urea?
urease test
what is urea?
a product of the carboxylation of several amino acids
when you hydrolyze urea you get two products, what are they?
ammonia and CO2
what is used for the detection of urease-producing bacteria?
pH indicator (phenol red)
in a urease test, if the bacteria has a high pH this means it is_______ and the broth will turn______.
basic, hot pink
RAPID urease producers
media that have two buffers to resist alkalization
T/F you have to read the urease test within 24hrs.
True
why do you have to read the urease test within 24 hours?
So it doesn’t make a burst of ammonia to take over the system in a very lange concentration
Is the urease test able to be autoclaved?
No
How do you sterilize the urease test?
use filter sterilization (need to have pores of 0.2 uL)
DNAase test
Excoenzyme, Depolimerizes DNA
After the DNA is polimerized, can DNA associate with methyl green?
no
what kind of organism is the IMViC test mostly used for?
gram negative enteric organisms
what does IMViC stand for?
Indole, Methyl red, Voges-pros-Kaver, citrate
what does the Indole test look for?
looks for the expression of tryptophanase
what does tryptophanase do?
breaks down tryptophan
what 3 products are produced if tryptophanase is produced?
indole, pyruvate, ammonia
In the indole test, what is the only product that sticks around?
indole (its the key target)
what type of broth do you use during the indole test? what do you add to see the results?
1% tryptone broth, add kovacs reagent
what does the kovacs reagent do?
adds a red ring on top of the media
what does SIM media stand for?
sulfer reduction, indole, motility
Both methyl red and voges pros kaver use________
MR-VP broth
what is methyl red looking for?
looks for evidence of mixed acid fermentation (lactase succinate, formate, acetate)
in the IMViC test does methyl red use a pH indicator?
yes, if red its an acidic pH which is a positive test
what is the voges pros kaver test looking for?
looking for evidence of butandiol fermentation, acetoin
what is acetoin?
precurser to butandiol
what two reagents do you add to the voges pros kaver test?
Barritts reagent A( alpha napthol) and Barritts reagent B (KOH)
Are you able to get an organism that is positive for mixed acid and butandiol fermentation?
No
what type of agar does the citrate test use?
simmons citrate agar (synthetic media)
all ______ ________ ________ bacteria can use citrate as an energy source
gram negative enteric
what does the citrate test look for?
looking for the expression of citrate permease
what is in simmons citrate agar?
mineral salts, sodium citrate, and ammonium ions
T/F if bacteria can grow in the simmons citrate agar they have citrate permease
true
in citrate test, if the broth uses _______ _____ and increase pH, this can be used as a definitive answer. (look for pH change)
ammonium ions
what is the pH indicator in the citrate test?
Bromthymol blue
if the pH _____ then the tube turns _____. green means _______
increases, blue, neutral
T/F Methyl green attaches to fragmented DNA to signify a positive DNase result
False
why are there two buffers that resist alkilization in the urease test?
so you can distinguish the RAPID urease producers
what three characteristics can be determied by inoculating SIM media?
sulfer reduction
indole
motility
the ___________________ test determines whether a bacteria can undergo butandiol fermentation by looking for the production of the butandiol precursor, _________, after incubation after the the addition of _____________.
voges pros kaver, acetoin, barritts reagents
