117 terms

lab test #3

If a bacteria produces acid from carbohydrate fermentation, what color will the medium turn?
what substances do you drop onto the bacterial colony when doing the catalase production test
hydrogen peroxide
in the catalase production test, what enzyme catalyzes the reaction
how can you tell if a catalase production test is positive
bubbles form
what are the two enzymes involved in nitrate reduction
nitrate reductase and reductase
If both steps of nitrate reduction are complete, what is the final end product that is made.
ammonia or nitrogen
If you added drops of reagent A and reagent B in the nitrate reduction test and the medium turns red, what does that indicate about the chemical reaction?
nitrite is present in the medium, the bacteria was able to reduce nitrate to nitrite.
you are performing the nitrate reduction test. After adding reagents (A and B) to the medium, there is no change to the medium. What is the next step you take to find out if the nitrate was reduced
add zinc powder
You are performing the nitrate reduction test. If after adding zinc powder, the solution turns red. What does that tell you about the chemical reaction.
nitrate was present. therefore no nitrate reduction occurred.
In what type of medium does motility test take place.
semi solid medium with reduced amount of agar.
when testing for starch hydrolysis, what reagent is used on the starch agar plate?
Grams iodine
when start is combined with grams iodine, what color does it turn.
bluish black
When performing the starch hydrolysis test, what will the medium look like if the bacteria breaks down the starch?
Clear area in the medium around the growth.
in casein hydrolysis, the enzyme casease breaks down casein into what?
polypeptides and amino acids
what does a medium look like in which casein hydrolysis has occurred.
clear area around growth.
in gelatin hydrolysis the enzyme gelatinase breaks down gelatin into what.
polypeptides and amino acids.
you are performing the gelatin hydrolysis test. After inoculation, incubation and refridgeration . How can you tell if the bacteria has the enzyme gelatinase (and can breakdown gelatin).
the medium is liquid.
you are performing the urea digestion test (urea hydrolysis test). What color does the solution turn if the bacteria is able to complete urea digestion.
bright pink
when a bacteria digests urea, what bi-products are produced.
h2O,CO2, ammonia
if a bacteria has the enzyme cysteine desulfurase it can convert cysteine into H2S(hydrogen sulfide). What will you see in the medium if this happens.
a black precipitate.
ampicillin and vancomycin do what?
inhibit cell wall synthesis
levoflaxin does what?
blocks dna gyrase
erythromycin does what
interrupts protein synthesis.
which kirby bauer test result should be most effective in treatment
what ways do microorganisms acquire resistance
alteration, degradation, impermeability of antibiotics. or modification of metabolic pathway so inhibited enzyme is no longer needed.
antibiotics that are effect against a broad array of bacteria. including both gram(+) and gram(-) organisms?
broad spectrum
antibiotics that are effective against a limited range of organisms
narrow spectrum
you have the measure the zone of inhibition and look up the interpretive criteria to determine if the bacteria is susceptible(S), Intermediate(I), resistant(R). True or false?
zone size alone doesn't determine the bacterias susceptibility or resistance to the antibiotic. True or false
you should stop taking antibiotics when the symptoms go away, and you start feeling better. true or false
antibiotics are not effective vs viral illnesses true or false.
pathogen with that zone size will likely be killed/inhibited by the concentration of drug in the bloodstream provided by the usual dose of that agent
provides a buffer zone to prevent small differences in the test from having a major impact on the interpretation.
Pathogen with that zone size will not likely be killed/inhibited.
what is true of enteric bacteria?
they normally inhabit the digestive tract.
they are gram negative rods
they are facultative anaerobes
they ferment glucose
what is true of MacConkeys agar
Bacteria that ferment lactose look pink
it is selective for gram negative bacteria
it is differential
you inoculate MacConkeys agar medium with bacteria. the bacteria grows but does not turn pink. what do you know about this bacteria?
it is gram negative
it does not ferment lactose
how does triple sugar iron agar differentiate bacteria
some bacteria might produce gas, others won't
some bacteria might produce hydrogen sulfide, others won't
it differentiates bacteria based on the ability to ferment glucose and other sugars.
indole test
determines whether a bacteria can degrade thryptophan
methyl red test
tests for mixed acid fermentation and the ability of an organism to produce highly acidic end products.
voges-proskauer test
determines whether an organism produces acetion by fermenting glucose
citrate utilization test
determines whether an organism can utilize citrate as its only source of carbon
what would you be able to learn form an organism during the citrate utilization test
whether or not the bacteria produces alkaline end products
whether or not the bacteria can utilize citrate as its only source of carbon
MacConkey agar contains
contains crystal violet and bile salts
triple sugar iron (TSI) agar contains
Voges-proskauer test
Requires adding two reagents to the medium and shaking it.
Indole production
Contains tryptophan
triple sugar iron agar positive and negative results
medium turns black if the bacteria uses iron to produce hydrogen sulfide
indole production positive and negative results
if an organism can degrade tryptophan, a red ring appears at the top of the medium
methyl red test positive and negative results
an organism that doesn't produce acid will cause this liquid medium to remain yellow.
MacConkey agar selects for?
gram negative bacteria
Voges-Proskauer test mediums turns
reddish-pink color of acetoin is present
urea hydrolysis broth appears
pale or amber color in a negative test
citrate utilization test medium turns
blue blue indicating that a medium is alkaline
Enteric bacteria are
Bacteria that normally inhabit the human digestive tract
what enzyme breaks down starch into glucose?
MacConkeys agar is selective to what bacteria
Gram-negative bacteria
MacConkeys agar is a differential agar. True or False
A positive test for a MacConkeys agar test would be?
Bacterial growth is pink
What does an Indole test determine
Determines whether an organism can degrade tryptophan
In a urea digestion Ammonia will?
Raise the Ph
Casease breaks down milk protein which releases what?
amino acids
selective media
allow certain bacteria to grow while preventing other bacteria from growing.
differential media
contain indicators that distinguish bacteria from another
enriched media
contain extra nutrients, growth stimulants.
what is blood agar
both enriched and differential
blood agar is differential because types of bacteria lyse red blood cells similarly. true or false
what organisms does MacConkey agar inhibit
Gram positive bacteria
MacConkey agar is selective because it contains bile salts and crystal violet. true or false
what color will growth on MacConkey agar turn if a bacteria produces acid?
what is true of mannitol salt agar
it is selective
it has a Ph indicator
it is differential
Carbohydrate fermentation(broth)-what is the reaction?
(glucose,lactose,sucrose)------Fermentation/enzymes--------->acid & or gas
Carbohydrate fermentation(broth)-what is the procedure
Durham tube to detect gas formation Phenol red pH indicator is in the medium
Carbohydrate fermentation(broth)-what is the interpretation
red=no acid(-)
no gas(-)
Oxidase test(trypticase soy agar(TSA) plate-streak for isolation-reaction
Oxidase test(trypticase soy agar(TSA) plate-streak for isolation- what is the procedure?
smear bacterial colony onto drop of oxidase test reagent on filter paper
Oxidase test(trypticase soy agar(TSA) plate-streak for isolation- Interpretation
(+)-purple color within 1 mins
(-)-No purple(or delayed faint purple color)
Catalase production(trypticase soy agar(TSA) plate-streak for isolation- What is reaction
Hydrogen peroxide--->catalase--->2h2O + O2
trypticase soy agar(TSA) plate-streak for isolation- Procedure
Smear bacterial colnoy on glass slide; add drop of 3% hydrogen peroxide
trypticase soy agar(TSA) plate-streak for isolation- interpretation
Nitrate reduction(nitrate broth)-reaction
Nitrate--->nitrate reductase---nitrite---->reductase--->ammonia or nitrate
trypticase soy agar(TSA) plate-streak for isolation- Procedure
Stage 1- add 5 drops of (A sulfanilic acid) and (B napthylamine)
Stage 2- add C zinc powder
Motility test(motility test broth)-procedure
inoculate by stabbing with a needle
motility test(motility test broth)-interpretation
(+)organisms grow & spread away from line of innoculation
(-)Nonmotile will only grow at line of penetration
Indole production(Tryptophan broth)-Reaction
Tryptophan--->tryptophanase--->indole + pyruvate
Indole prodction(tryptophan borth)-procedure
Add 8 drops of Kovacs reagent
Indole production(tryptophan broth)-Interpretation
Red at top=indole present(+)
Yellow clean ring=no indole present(-)
Methyl Red Test(MRVP medium)-Reaction
Glucose---fermentation/enzymes-->highly acidic products
Methyl Red Test(MRVP medium)-Procedure
Add 5 drops methyl red indicator
Methyl Red Test(MRVP)-Interpretation
Red=acid is present
yellow=not acidic
Voges-proskauer test (MRVP medium)-reaction
Voges-proskauer test (MRVP medium)-procedure
Add 15 drops of VP reagent A;mix. Add 5 drops VP reagent B; Mix let set ~4hr
Voges-proskauer test (MRVP medium)-interpretation
Redish color in 4 hr(+)
Yellow brown-no acid(-)
Citrate utilization(citrate agar slant)-reaction
Citrate utilization(citrate agar slant)-procedure
Bromthymol blue pH indicator is in the medium
Citrate utilization(citrate agar slant)-interpration
blue=alkayline, citrate used(+)
green=not alkaline, citrate not used(-)
Carbohydrate fermentation(glucose,lactose,sucrose)-(triple Sugar Iron Agar(TSI))-Reaction
Carbohydrate fermentation(glucose,lactose,sucrose)-(triple Sugar Iron Agar(TSI))-Procedure
Phenol red pH indicator is in the medium
Carbohydrate fermentation(glucose,lactose,sucrose)-(triple Sugar Iron Agar(TSI))-Interpretation
Hydrogen sulfide production(triple sugar Iron agar slant)-reaction
na thisulfate--->S reduction enzymes---->H2S
Hydrogen sulfide production(triple sugar Iron agar slant)-procedure
Ferrous sulfate is in the medium
Hydrogen sulfide production(triple sugar Iron agar slant)-interpretation
Black=hydrogen sulfide(+)
starch hydrolysis(starch agar)-reaction
Starch hydrolysis(starch agar)-Procedure
Add gram's iodine to cover surface of plate
Starch hydrolysis(starch agar)-interpretation
(+) clear area in medium around growth, starch hydrolyzed
(-)Dark area around growth, staach not hydrolyzed
Casein hydrolysis(skim agar)-reaction
Casein--->caseinase--->Polypeptides & amino acids
Casein hydrolysis(skim agar)-interpretation
(+)clear area around growth, casein hydrolyzed
(-)no change in medium around growth
Gelatin Hydrolysis(nutrient gelatin deep)-Reaction
Gelatine--->gelatinase---->Polypeptides & amino acids
Gelatin hydrolysis(nutrient gelatin deep)-procedure
Refrigerate or chill before reading
Gelatin hydrolysis(nutrient gelatin deep)-interpretation
Medium is liquid, gelatin was hydrolyzed(+)
Medium remains solid, gelatin was not hydrolyzed(-)
Urea hydrolysis(urea broth)-reaction
Urea + 2h20--->urease--->ammoinia+co2+h20
urea hydrolysis(urea broth)-procedure
Phenol red pH indicator is in the medium
urea Hydrolysis(urea broth)-Interpretation
(+)bright pink, urea hydrolyzed
(-)pale amber color, or no change urea not hydrolyzed
Hydrogen sulfide(H2S) production(Peptone iron agar deep)-reaction
Cysteine---> cysteine sulfurase--->H2S + alanine
Hydrogen sulfide(H2S) production(Peptone iron agar deep)-Procedure
Iron sulfate is in the medium
Hydrogen sulfide(H2S) production(Peptone iron agar deep)-interpretation
(+)Black precipitate, H2S produced
(-)No black precipitate, no H2S produced.
MacConkey Agar
growth=gram negative-red/pink lactose perfementer, colorless=non lactose fermenter
no growth=non gram negative.