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72 Cards in this Set
- Front
- Back
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Principal of OF carbs
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Differentiates fermentors and oxidizers of carbs
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How is an OF carb test set up?
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Inoculate 2 tubes with bug;
-one overlaid, anaerobic environment; -one is left open for aerobic; Incubate, wait to see which turn acid |
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Results of OF:
-Fermentor only of carb -Fermentor and Oxidizer of carb -Oxidizer of carb -Neither |
1. Only tube overlaid will turn yellow
2. Both tubes turn yellow 3. Only open tube turns yellow. 4. Both stay neutral or blue due to peptone use |
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What's in an OF carb tube?
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-1% carb
-Brom thymol blue Semisolid agar |
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what type of dye is in DNAse plates?
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-methyl green
or -toluidine blue |
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what reagent is used for catalase?
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3% H2O2
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How can you mess up a catalase?
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1. Dropping H2O2 and then adding bug; touching needle to H2O2 causes false +.
2. Blood agar in peroxide -> false+ 3. Old cultures 4. Exposing H2O2 to light. |
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What does coagulase test differentiate?
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S. aureus from coag-neg staphs.
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what isbound coagulase also known as?
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clumping factor
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Which type of coagulase does the tube coag test detect?
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Both free and bound.
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Which type of coagulase does the slide test detect?
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Bound (to the cell) coagulase
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What is the action of bound coagulase?
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Converting fibrinogen rapidly to fibrin.
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What is the action of free coagulase?
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Reacts w/ a plasma factor to form substance like thrombin which eventually activates formation of FIBRIN.
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Process of a Slide coag test:
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1. Heat slide; draw 2 circles, label TEST and CONTROL
2. drop of water in each circle. 3. emulsify w/ organism 4. to test add drop of plasma 5. rotate/look for clumps in 30 sec. |
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how long should a tube coag test be incubated before calling negative?
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4 hours
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What is the reagent for a coag test?
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Plasma
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How can you mess up a coag test?
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1. Using cold plasma -> false neg
2. Failing to run control; maybe it was a false neg. 3. Using a mixed culture can give false pos (even tho its not coag) 4. Observe every 30 min; fibrinolysin may break down clot b4 you see it. 5. Don't shake tube or you'll ruin it. |
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What does a DNAse differentiate?
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1. S. aureus from coag neg staphs
2. Serratia(+) from Enterobacter(-) 3. M. catarrhalis(+) from Neisseria(-) |
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Which produces DNAse, S. aureus or S. epidermidis?
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BOTH; but s. epi produces less - not enough to make a positive test.
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2 types of DNA agar:
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-methyl green
-toluidine blue |
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whats teh problem with toluidine blue?
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inhibits growth of enteric bacteria
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What are results of a DNase test:
positive negative |
pos = zone of clearing around inoculum
neg = growth right up to edge |
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How can you mess up a DNAse
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not enough inoculum - not enough DNAse activity to cause clearing
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What's in a Mannitol salt agar?
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-7.5% salt
-Phenol red -Mannitol |
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Purpose of Mannitol salt
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to preliminary id. S. aureus from coag neg s. aureus.
-isolate S. aureus from a clinical specimen |
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Results of a Mannitol Salt agar test:
pos neg |
Pos = growth; yellow - mannitol ferm.
Neg = no growth; red - nonfermentor. |
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How can you mess up a mannitol salt agar?
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Too much inoculum - the mannitol runs out, Positive bugs revert to peptone use and it appears negative falsely.
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What is a BACTi staph?
What does it detect? |
Quick slid latex agglutination test kit.
Both protein A and coagulase from S. aureus |
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Why are acid fast organisms called that?
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they don't decolorize with acid alcohol
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What dye is used in a cold acid fast stain?
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Kinyoun's carbol fuchsin
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What is the counterstain in a cold acid fast stain?
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methlene blue
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What stains are used in a cold acid fast stain?
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Primary - Kinyoun's carbol fuchsin
Counter - Methylene blue or brilliant green |
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What are 2 alternates to an acid fast stain?
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-Ziehl-neelson
Truant flourescent |
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What is
-beading -cording |
beading - the rods don't take up the stain evenly.
cording - cells grow lying end-end; make long strands when stained. |
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What do Acid fast stain results look like?
-Pos -Neg |
pos = red
neg = blue or green |
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What is a bacitracin test for, what are
-Pos -Neg results? |
Strep group A;
Pos = inhibition, susceptible. Neg = no inhibition, growth right up to disc |
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how can you mess up a bacitracin test?
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-use bugs other than beta-strep; can give false +
-think it's a definitive test - some Beta-streps other than Strep A can give false + |
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What do you run a Bile Solubility test for?
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To differentiate Strep pneumonia from other alpha-hemolytic Streps. Alternative to optichin
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What are the active factors in a bile solubility test?
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Bile salts - sodium deoxycholate, sodium taurocholate
Streptolysin produced by the strep pneumoniae itself. |
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What do the active ingredients of the Bile solubility test do?
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Bile salts and autolysin cause cell-memrane derangement, and destruction of the pneumococcal cell.
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What are results of a bile solubility
-Pos -Neg |
Pos:
-Cleared (lysed) test, Turbid control Neg: -Turbid test AND control |
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What reagent is added to a broth culture for a bile solubility test?
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Sodium deoxycholate - the bile salt
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How to report Bile solubility results?
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Positive, bile soluble
Negative, bile insoluble. |
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Camp test identifies what?
Alternate? |
Strep group B
Hippurate hydrolysis |
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What happens in a CAMP test?
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CAMP factor produced by Strep B bugs acts synergistically with Staph A's beta hemolysin to lyse sheep RBCs
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What is a hippurate hydrolysis test for?
Alternate to: |
I.D. of Strep group B; an alternate for the CAMP test.
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What chemical reaction occurs in the hippurate hydrolysis?
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Hippuricase hydrolyzes Sodium hippurate into benzoid acid plus glycine.
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What reagent is used in the Hippurate Hydrolysis test;
what product does it check for? What color forms? |
Ninhydrin; checks for glycine produced from hippurate hydrolysis.
Forms a purple color |
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what do results of a hippurate hydrolysis test look like?
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Positive = deep purple
Negative = faint purple |
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What error can occur in hippurate hydrolysis?
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Incubating too long = results beyond thirty min after adding the ninhydrin can be false positive since everything will be positive after a while.
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6.5% NACL is for:
Error can be from: |
Enterococcus differentiation from Strep group D nonentero.
Contamination |
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optichin test is for:
error can be from: |
-strep pneumo from viridans
-presumptive only; using non-alpha hemolytic bugs |
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Chemical ingredient of Optochin:
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ethylhydrocupreine hydrochloride
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What is the alternate test for a Bacitracin test?
What does it identify? |
PYR hydrolysis;
Identifies Strep group A |
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What enzyme hydrolyzies PYR, and what bugs produce it?
What is produced from the hydrolysis? |
L-pyroglutamyl aminopeptidase.
Enterococci and Strep group A. Produces Beta-naphthylamine |
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What reagent do you add run a PYR test?
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Cinnamaldehyde
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What are PYR test results
-Pos -Neg What does the test indication result from? |
Pos = bright red color w/in 5 min
Neg = no color or orange. Red is from Cinnemaldehyde reacting with Beta-naphthylamine. |
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What tests are used to identify/differentiate Neisserias and Moraxella catarrhalis?
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-CTA carb tubes
-Oxidase -APT NH |
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what are CTA carbs for?
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differentiating Neisserias.
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What is CTA?
What does it show? |
Cystine Trypticase Agar;
carbs added to it; Shows organism's ability to oxidize carbs. |
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what is the pH indicator in CTA tubes
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phenol red
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CTA results for
positive negative |
pos = yellow; oxidizer of carb
neg = red/orange. |
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how can you mess up a CTA carb?
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Too small of inoculum gives = false neg
Incubating not long enough = false neg Yellow color all the way down indicates a contaminant |
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What is OXIDASE essentially for differentiating?
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gram negative cocci and bacilli
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What is oxidase?
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an enzyme necessary for some bugs, for oxidation of carbs.
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What is the reagent used for oxidase testing?
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tetramethylparaphenylendiamine dihydrochloride.
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What happens when colonies are rubbed into filter paper soaked in Oxidase reagent?
Pos Neg |
Pos = purple color forms when reagent reacts with oxidase.
Neg = no color appears. |
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How can you mess up an oxidase test?
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-Exposing Oxidase reagent to light causes auto-oxidation; discard.
-Reading beyond 10 seconds. -using a metal inoculating needle - false positive -getting culture media in the reagent. -false neg for organisms growing on high-glucose media; fermentation inhibits oxidase activity. |
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when testing a gram neg cocci on a nutrient agar plate, how do you incubate it?
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in a candle jar. they're fastidious organisms.
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what is the endproduct that is purple in the Oxidase reaction?
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indophenol
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what is the staining reaction of Listeria?
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very short gram positive coccobacilli
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How can gram positive bacilli be identified?
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-various catalase reactions
-various lengths on gram stain -all oxidase positive |
