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CLS 753 > Micro - Biochemical Testing II > Flashcards

Micro - Biochemical Testing II Flashcards

1
Q

Are biochemical tests to determine the genotype or phenotype of an organism?

A

Phenotype

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2
Q

Two types of general biochemical tests as they relate to speed of the test

A

Rapid test

  • spot tests = immediate reaction
  • same-day tests = 4 hours or less

Conventional tests
-single tube tests usually within 18-24 hrs

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3
Q

Single enzyme tests (6)

A

Catalase

Coagulase

Oxidase

Indole

Urease

PYR

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4
Q

Catalase converts ___ into…

A

Hydrogen peroxide

Water and oxygen

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5
Q

This group of organisms do not have catalase

A

Obligate anaerobes

-lethal for them

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6
Q

Catalase differentiates these 3 major genera of organisms: Staph, Strep, Listeria. What are the test results for each?

A

Staphylococcus and Listeria = positive

Streptococcus = negative

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7
Q

Weak bubbling or bubbling that takes place a few minutes later is catalase ___

A

Negative

-positive must be IMMEDIATE bubbling

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8
Q

When should we perform a coagulase test?

A

For gram-positive cocci that are catalase positive

-need to determine if organism is Staph aureus

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9
Q

What organism (genus/species) does the slide coagulase test SCREEN for? What test do we use to CONFIRM if it’s this organism?

A

Staph aureus
-most virulent Staph

Tube coagulase test

  • read every 30 mins for 4 hrs
  • incubate and read after 18 hrs if negative
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10
Q

Which coagulase test is used to detect bound coagulase and which is used to detect free coagulase?

A

Slide coagulase test = bound coagulase

Tube coagulase test = free coagulase

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11
Q

Both slide and tube coagulase tests are based on this mechanism that causes coagulation

A

Bound coagulase on cell wall or free coagulase converts fibrinogen to insoluble fibrin clot

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12
Q

When doing the tube coagulase test, why should we check on the tube every half hour for up to 4 hours to determine if there’s coagulation?

A

Staphycoccus produces staphylokinase, which dissolves the fibrin clot
-causes false negative results

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13
Q

Oxidase is an enzyme that is involved in what types of reactions?

A

Redox reactions

  • catalyzes transport of electrons from donor compounds (NADH) to electron acceptors
  • Kovac’s reagent acts as artificial electron acceptor and changes color
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14
Q

The oxidase test is used to differentiate gram-positive or gram-negative bacteria? Differentiates what groups of organisms? Enterobacteriaceae are catalase positive or negative?

A

Gram-negative

Non-enterics from enterics

Negative

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15
Q

An organism that is oxidase positive will convert the reagent, ___, into this color… A negative result looks like this…

A

Kovac’s

Blue-purple

No color change

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16
Q

Positive and negative QC cells for catalase test are

A

Positive control = Staph aureus

Negative control = Strep pyogenes

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17
Q

Positive and negative QC cells for oxidase test are

A

Positive control = Pseudomonas aeruginosa

Negative control = E coli

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18
Q

The indole test detects the presence of the enzyme ___, which hydrolyzes the amino acid ___ into ___

A

Tryptophanase

Tryptophan

Indole

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19
Q

The indole test is used in the differentiation of this group of organisms. The test is useful for the identification of these two organisms in the group that test positive…

A

Anaerobes/Enterobacteriaceiae

E. coli
Proteus vulgaris

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20
Q

Bromcresol purple has this color at acidic pH and this color at alkaline pH

A

Yellow

Purple

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21
Q

Bromcresol blue has this color at acidic pH and this color at alkaline pH

A

Yellow

Blue

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22
Q

Phenol red has this color at acidic pH and this color at alkaline pH

A

Yellow

Red/pink

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23
Q

Neutral red has this color at acidic pH and this color at alkaline pH. What common agar plate is it normally used in?

A

Red

Yellow

MacConkey agar

24
Q

There are 3 types of indole tests. A positive result looks like this… A negative result looks like this…

A

Color change
-blue-green or bright pinkish red

Colorless

25
Q

The urease enzyme is used to break down ___ into ___

A

Urea

Ammonia and CO2

  • CO2 released
  • ammonia reacts with water to form ammonium hydroxide, which raises pH
26
Q

Is a positive urease test acidic or alkaline pH? What is the pH indicator for the urease test?

A

Alkaline

Phenol red

27
Q

Urease test - what color is the positive tube? What color is the negative tube? What is a weak positive reaction considered?

A

Pink

Yellow

Weak positive = positive
-any pink is positive for test

28
Q

The PYR test is to ID this organism (genus). The test is also used to differentiate ___ (genus) from Group D Streptococcus

A

Group A Streptococcus (S. pyogenes)

Enterococcus

-both are positive for PYR test

29
Q

PYR test - a positive result looks like this

A

Red/pink color

30
Q

The carbohydrate fermentation tests are useful to differentiate this family of organisms…

A

Enterobacteriaceae

31
Q

Carbohydrate fermentation - pH indicator… Gas in trapped in inverted…

A

Phenol red

Durham tube

32
Q

Carbohydrate fermentation - positive result looks like… Negative result looks like…

A

Yellow (with/without gas production)

Red

33
Q

Amino acid degradation results in pH that is… Why?

A

Alkaline

Due to actions of dehydrolyase, decarboxylase or deaminase

34
Q

Amino acid degradation is used to differentiate these species (3) from the rest of Enterobacteriaceae. Are they all positive or negative for the test?

A

Proteus
Morganella
Providencia

Positive
-rest of enterics are negative

35
Q

Amino acid degradation - decarboxylase positive looks like… Decarboxylase negative looks like…

A

Purple

Yellow (from glucose fermentation)

36
Q

How do we create an anaerobic condition for amino acid degradation test tube (ie lysine decarboxylase)

A

Add mineral oil

37
Q

Phenylalanine deaminase test - what color is produced once ferric chloride is added?

A

Green

38
Q

MR test checks for production of… VP test checks for production of…

A

Mixed acids

Neutral end products (acetoin, diacetyl)

39
Q

Can an organism be positive for both MR and VP?

A

No, either MR or VP is positive, never both

40
Q

A positive MR or VP test is the appearance of a ___ color upon addition of their respective reagents

A

Red

  • neg MR = yellow/orange
  • neg VP = brown/copper
41
Q

Citrate, malonate, and acetate are tests that utilize…

A

Their respective substrates as the sole carbon source

-citrate most common

42
Q

Citrate test - pH indicator? What does the positive result look like (2)? What does the negative result look like?

A

Bromothymol blue

Growth or blue color

Green

43
Q

Salt tolerance test - pH indicator… How much salt does the media contain?

A

Bromocresol purple

6.5% sodium chloride

  • high salt inhibitory to many organisms
  • contains glucose
44
Q

What is the term for a salt loving organism?

A

Halophile

-ie Enterococcus

45
Q

Salt tolerance test - what does a positive result look like (2)? What does a negative result look like?

A

Turbidity in medium
OR
Yellow

Purple

46
Q

Bile esculin hydrolysis - positive result look like… Negative result looks like…

A

Black slant

  • indicates esculin hydrolysis
  • bile is inhibitory to most pathogens

No color change
-brown

47
Q

Optochin sensitivity test - what is optochin? What organism is the test confirmatory for (genus/species)? What similar group of organisms does the test rule out (what type of hemolysis)?

A

Antibacterial agent

Streptococcus pneumoniae = alpha hemolytic

Rules out other alpha hemolytic streptococci
-not done for beta or gamma-hemolytic

48
Q

Is Streptococcus pneumoniae optochin sensitive or insensitive?

A

Sensitive - look for zone of inhibition around disk

49
Q

Which group of organisms are vancomycin resistant? Which are not?

A

Gram-negative = resistant

Gram-positive = susceptible

50
Q

Novobiocin resistance is used to screen for what organism (genus/species)? Is it resistant or susceptible to the antibiotic?

A

Staphylococcus saprophyticus
-UTI pathogen

Resistant

51
Q

Does Haemophilus grow on blood agar or chocolate agar? Why or why not?

A

Grows only on chocolate agar (hemolysed RBCs). Cannot grow on blood agar since it can’t break down RBCs (unless satelliting around another organism)

52
Q

Haemophilus requires these two factors for growth… Which factor(s) does H. influenziae require for growth? Which factor(s) does H. parainfluenzae require for growth?

A

X or V or both, depending on species

Both X and V

V
-has X

53
Q

Haemophilus exhibits satelliting around this organism when co-cultured on a blood plate… Why?

A

S aureus

S aureus breaks down RBCs, allowing Haemophilus to grow around it
-make small streaks of S aureus on blood agar plate with Haemophilus lawn of growth

54
Q

What is CAMP? What organism is it made by?

A

Extracellular protein

Group B streptococci (S. agalactiae)

  • weakly beta hemolytic
  • Group A streptococci (S. pyogenes) do not make CAMP
55
Q

What does CAMP interact with? What species makes this other compound? What does the interaction do?

A

Beta lysin toxin

Staph aureus

Synergistic effect - enhanced hemolysis on blood agar

56
Q

Carbohydrate fermentation uses how many tubes per sugar tested? OF oxidative/fermentation uses how many tubes per sugar tested?

A

1

2
-cover one tube with mineral oil for fermentation conditions

CLS 753 (12 decks)

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