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MICRO/PARA > Methods and Procedures in Diagnostic Microbiology > Flashcards

Methods and Procedures in Diagnostic Microbiology Flashcards

1
Q

Bacteria capable of growth on this medium produce the enzyme acylamidase, which deaminates acetamide to release ammonia.

A

Acetamide Utilization Test

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2
Q

Positive color of Acetamide Utilization Test

A

Deamination of the acetamide resulting in a BLUE color.

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3
Q

POS organism in Acetamide Utilization Test

A

P.aeruginosa

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4
Q

NEG reaction in Acetamide Utilization Test

A

No color change/Green

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5
Q

NEG organism in Acetamide Utilization Test

A

E.coli

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6
Q

Purpose:
Differentiate microorganisms based on the ability to use acetamide the sole source of carbon.

A

Acetamide Utilization Test

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7
Q

Principle:
Organism capable of using sodium acetate grow in the medium, resulting in an alkaline pH, turning the bromothymol blue ind. from green to blue.

A

Acetate Utilization Test

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8
Q

POS reaction in Acetate Utilization Test

A

Medium becomes alkalinized (BLUE) as a result of the growth and use of acetate.

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9
Q

POS organism in Acetate Utilization Test

A

E.coli

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10
Q

NEG reaction in Acetate Utilization Test

A

No color change/Green

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11
Q

NEG organism in Acetate Utilization Test

A

S.sonnei

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12
Q

Purpose:
Differentiate microorganisms based on the ability to use acetate as the sole source of carbon. Generally used to differentiate Shigella from E. coli.

A

Acetate Utilization Test

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13
Q

Principle
➢ Bacitracin inhibits the synthesis of bacterial cell walls.
➢ A disk (TaxoA) impregnated with a small amount of bacitracin (0.04 units) is placed on an agar plate.
➢ After incubation the inoculated plates are examined for zone of inhibition.

A

Bacitracin Susceptibility Test

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14
Q

POS reaction in Bacitracin Susceptibility Test

A

Any zone of inhibition >10 mm

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15
Q

POS organism in Bacitracin Susceptibility Test

A

S. pyogenes
M. luteus

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16
Q

NEG reaction in Bacitracin Susceptibility Test

A

No zone of inhibition (resistant)

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17
Q

NEG organism in Bacitracin Susceptibility Test

A

S. agalactiae
S. aureus

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18
Q

This test is used to provide presumptive identification and differentiation of:
➢ Beta-hemolytic group A streptococci (S. pyogenes are susceptible) from other beta hemolytic streptococci.
➢ Also used to distinguished staphylococci (resistant) from micrococci (susceptible)

A

Bacitracin Susceptibility Test

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19
Q

This test is used for the presumptive identification of enterococci and organism in the Streptococcus bovis group. The test differentiates enterococci and group D streptococci from non-group D viridans streptococci.

A

Bile Esculin Test

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20
Q

➢ Gram-positive other than some streptococci and enterococci are inhibited by the bile salts in this medium.
➢ Organisms capable of growth in the presence of 4% bile and able to hydrolyze esculin to esculetin.
➢ Esculetin reacts with Fe3+ and forms a dark brown to black precipitate.

A

Bile Esculin Test

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21
Q

POS reaction in Bile Esculin Test

A

Growth and blackening of the agar slant

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22
Q

POS organism in Bile Esculin Test

A

E.faecalis

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23
Q

NEG reaction in Bile Esculin Test

A

Growth and no blackening of medium, no growth

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24
Q

NEG organism in Bile Esculin Test

A

E. coli (growth, no color change)
S. pyogenes (no growth, no color change)

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25
Q

This test differentiates Streptococcus pneumoniae (positive-soluble) from alpha-hemolytic streptococci (negative-insoluble)

A

Bile Solubility Test

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26
Q

➢ Bile or a solution of a bile salt (ex. sodium desoxycholate) rapidly lyses pneumococcal colonies.
➢ Lysis depends on the presence of an intracellular autolytic enzyme, amidase.

A

Bile Solubility Test

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27
Q

POS reaction in Bile Solubility Test

A

Colony DISINTEGRATES; an imprint of the LYSED colony may remain in the zone

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28
Q

POS organism in Bile Solubility Test

A

S.pneumoniae

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29
Q

NEG reaction in Bile Solubility Test

A

Intact colonies

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30
Q

NEG organism in Bile Solubility Test

A

E.faecalis

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31
Q

This is a rapid test to detect the enzyme butyrate esterase, to aid identification of Moraxella (Branhamella) catarrhalis.

A

Butyrate disk

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32
Q

➢ Organisms capable of producing butyrate esterase hydrolyze bromochlorindolyl butyrate.
➢ Hydrolysis of the substrate in the presence of butyrate esterase releases indoxyl.
➢ Indoxyl in the presence of oxygen spontaneously form indigo, a blue to blue- violet color.

A

Butyrate disk

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33
Q

POS reaction in Butyrate disk

A

Development of a blue color during the 5-minute incubation period

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34
Q

POS organism in Butyrate disk

A

M.catarrhalis

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35
Q

NEG reaction in Butyrate disk

A

No color change/Indigo

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36
Q

NEG organism in Butyrate disk

A

N.gonorrhoeae

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37
Q

This test is used to differentiate group B streptococci (Streptococcus agalactiae-positive) from other streptococci. L. monocytogenes also produces a positive CAMP reaction.

A

Christie, Atkins, and Munch-Peterson (CAMP) test

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38
Q

➢ Certain organisms produce a diffusible extracellular hemolytic protein (CAMP factor) that acts synergistically with the beta-lysin of Staphylococcus aureus to cause enhanced lysis or red blood cells.
➢ The group B streptococci are streaked perpendicular to a streak of S. aureus on sheep blood agar.

A

Christie, Atkins, and Munch-Peterson (CAMP) test

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39
Q

POS reaction in CAMP test

A

Enhanced hemolysis is indicated by an ARROWHEAD-SHAPED zone of beta- hemolysis at the juncture of the two organisms.

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40
Q

NEG reaction in CAMP test

A

No enhancement of hemolysis

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41
Q

POS organism in CAMP test

A

S. agalactiae

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42
Q

NEG organism in CAMP test

A

S. pyogenes

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43
Q

This test differentiates catalase-positive micrococcal and staphylococcal species from catalase-negative streptococcal species.

A

Catalase Test

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44
Q

➢ Aerobic and facultative aerobic organisms produce two toxins during normal metabolism, hydrogen peroxide (H2O2) and superoxide radical (O2-).
➢ These organisms have the enzyme catalase.
➢ Catalase converts H2O2 to water and oxygen.

A

Catalase test

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45
Q

POS reaction in Catalase test

A

Copious bubbles are produced

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46
Q

NEG reaction in Catalase test

A

No or few bubbles are produced

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47
Q

POS organism in Catalase test

A

S. aureus

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48
Q

NEG organism in Catalase test

A

S.pyogenes

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49
Q

This test is primarily used to isolate and purify Pseudomonas aeruginosa from contaminated specimens.

A

Cetrimide agar

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50
Q

➢ Used to determine the ability of an organism to grow in the presence of cetrimide (cetyltrimethylammonium bromide), a toxic substance that inhibits the growth of many bacteria by causing the release of nitrogen and phosphorus, which slows or kills the organism.
➢ Pseudomonas aeruginosa is malupit and lodi
(haha ) and is resistant to cetrimide.

A

Cetrimide agar

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51
Q

POS reaction in Cetrimide agar

A

Growth, variation in color of colonies.

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52
Q

POS organism in Cetrimide agar

A

P.aeruginosa

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53
Q

NEG reaction in Cetrimide agar

A

No growth

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54
Q

NEG organism in Cetrimide agar

A

Escherichia coli

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55
Q

Used to identify organisms capable of using sodium citrate as the sole carbon source and inorganic ammonium salts as the sole nitrogen source.

A

Citrate Utilization

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56
Q

➢ Bacteria that can grow in this medium produce the enzyme citrate-permease
➢ Citrate-permease, capable of converting citrate to pyruvate.
➢ Pyruvate is used in the production of energy.
➢ Bacteria capable of growth use citrate to convert ammonium phosphate to ammonia and ammonium hydroxide, creating an alkaline environment.

A

Citrate Utilization

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57
Q

POS reaction in Citrate Utilization

A

Growth on the medium, with or without a change in the color of the indicator. GREEN to BLUE color.

58
Q

POS organism in Citrate Utilization

A

E.aerogenes

59
Q

NEG reaction in Citrate Utilization

A

Absence of growth

60
Q

NEG organism in Citrate Utilization

A

Escherichia coli

61
Q

This test is used to differentiate Staphylococcus aureus (positive) from coagulase-negative staphylococci (negative).

A

Coagulase Test

62
Q

S. aureus form of coagulase that bound to the bacterial cell wall and reacts directly with fibrinogen.
• Detected by the Slide test.

A

Bound coagulase or clumping factor

63
Q

POS reaction in Slide Coagulase test

A

Macroscopic clumping in 10 seconds in plasma, no clumping in saline or water drops

64
Q

NEG reaction in Slide Coagulase test

A

No clumping in either drop.

65
Q

Preferred coagulase plasma in Slide test

A

rabbit plasma with EDTA

66
Q

An extracellular protein enzyme that causes formation of a clot when colonies are incubated.
• Detected by the tube test.

A

Free coagulase

67
Q

➢ Bacterial colony is emulsified in 0.5 mL of rabbit plasma (with EDTA) to give a milky suspension.
➢ Incubate at 35-37 C in ambient air for 4 hours.

A

Coagulase Tube test

68
Q

POS reaction in Coagulase Tube test

A

Clot of any size

69
Q

POS organism in Coagulase Tube test

A

S.aureus

70
Q

NEG reaction in Coagulase Tube test

A

No clot

71
Q

NEG organism in Coagulase Tube test

A

S.epidermidis

72
Q

This test is used to differentiate decarboxylase- producing Enterobacteriaceae from other gram- negative rods.

A

Decarboxylase Tests (Moeller’s method)

73
Q

➢ This test measures the enzymatic ability (decarboxylase) of an organism to decarboxylate (or hydrolyze) an amino acid to form amine.
➢ Decarboxylation of amino acid results in an alkaline pH and a color change from orange to purple. (Take note that this method uses bromocresol purple)

A

Decarboxylase Tests (Moeller’s method)

74
Q

POS reaction in Decarboxylase Tests (Moeller’s method)

A

Alkaline (PURPLE) color change compared with the control tube

75
Q

NEG reaction in Decarboxylase Tests (Moeller’s method)

A

No color change or acid (YELLOW) color in test and control tube.
Growth in control tube

76
Q

POS organism in Decarboxylase Tests (Moeller’s method)

A

Lysine: K. pneumoniae
Ornithine: E. aerogenes
Arginine: E. cloacae

77
Q

NEG organism in Decarboxylase Tests (Moeller’s method)

A

Lysine: E. cloacae
Ornithine: K. pneumoniae
Arginine: K. pneumoniae

78
Q

This test is used to differentiate organisms based on the production of deoxyribonuclease (DNase):
➢ Serratia (positive) vs. Enterobacter (negative)
➢ Staphylococcus aureus (positive) from others
➢ Moraxella catarrhalis (positive) from Neisseria (negative)

A

DNA hydrolysis

79
Q

➢ Determine the ability of an organism to hydrolyze DNA.
➢ The medium is pale green because of the DNA-methyl green complex.
➢ If the organism growing on the medium hydrolyses DNA, the green color fades and the colony is surrounded by a colorless zone.

A

DNA hydrolysis

80
Q

POS reaction in DNA hydrolysis

A

When DNA is hydrolyzed, methyl green is released and combines with highly polymerized DNA at a pH of 7.5. TURNING THE MEDIUM COLORLESS.

81
Q

POS organism in DNA hydrolysis

A

S.aureus

82
Q

NEG reaction in DNA hydrolysis

A

If no degradation of DNA occurs, the medium remains GREEN

83
Q

NEG organism in DNA hydrolysis

A

E.coli

84
Q

This test is used for the presumptive identification and differentiation of Enterobacteriaceae.

A

Esculin hydrolysis

85
Q

➢ This test is used to determine whether an organism is able to hydrolyze the glycoside esculin.
➢ Esculin is hydrolyzed to esculetin, which reacts with Fe3+ and forms a dark brown to black precipitate.

A

Esculin hydrolysis

86
Q

POS reaction in Esculin hydrolysis

A

Blackened medium + loss of fluorescence under the wood’s lamp

87
Q

POS organism in Esculin hydrolysis

A

E.faecalis

88
Q

NEG reaction in Esculin hydrolysis

A

No blackening + No loss of fluorescence. Or Slight blackening + No loss of fluorescence

89
Q

NEG organism in Esculin hydrolysis

A

E.coli

90
Q

It is used to differentiate organism based on their ability to ferment carbohydrates.

A

Fermentation media

91
Q

It is is used to differentiate enteric bacteria from coryneform.

A

Andrade formula

92
Q

➢ A fermentation medium consists of basal medium containing a single carbohydrate (glucose, lactose, or sucrose) for fermentation.
➢ Color indicator detects the formation of acids.
➢ A Durham tube is placed to capture gas produced by metabolism.

A

Fermentation Media: Peptone w/ Andrade

93
Q

POS reaction in Fermentation Media: Peptone w/ Andrade

A

Indicator change to PINK with or without gas

94
Q

NEG reaction in Fermentation Media: Peptone w/ Andrade

A

Growth, but no color change. Medium remains clear to straw colored.

95
Q

POS organism in Fermentation Media: Peptone w/ Andrade

A

Dextrose:
➢ E. coli (positive with gas)
➢ S. flexneri (positive, no gas)

96
Q

NEG organism in Fermentation Media: Peptone w/ Andrade

A

Dextrose:
Moraxella osloensis

97
Q

It is used to differentiate enterococci from streptococci

A

Bromocresol purple formula

98
Q

POS reaction in Fermentation Media: BHI w/ Bromocresol

A

Indicator change to YELLOW

99
Q

NEG reaction in Fermentation Media: BHI w/ Bromocresol

A

Growth, but no color change. Remain purple

100
Q

POS organism in Fermentation Media: BHI w/ Bromocresol

A

Dextrose:
➢ E. coli (positive with gas)

101
Q

NEG organism in Fermentation Media: BHI w/ Bromocresol

A

Dextrose:
Moraxella osloensis

102
Q

This technique is used to visualize the presence and arrangement of flagella for the presumptive identification of motile species.

A

Flagella stain: Wet mount technique

103
Q

➢ RYU (Remel, Lenexa, Kansas) flagella stain is used.
➢ Cells with flagella are observed at 100x (oil)

A

Flagella stain: Wet mount technique

104
Q

E. coli flagella

A

Peritrichous

105
Q

Polar flagella

A

P. aeruginosa

106
Q

Negative flagella

A

K. pneumoniae

107
Q

The production of gelatinases capable of hydrolyzing gelatin is used as a presumptive test for the identification of various organisms, including Staphylococcus, Enterobacteriaceae, and some gram-positive bacilli.

A

Gelatin Hydrolysis

108
Q

➢ Test to determine the ability to produce gelatinase that liquefy gelatin (a component of vertebrate connective tissue)
➢ In this test, instead of agarose, gelatin is used as the solidifying agent.
➢ WHEN AN ORGANISM PRODUCES GELATINASE, the enzyme liquefies the growth medium.

A

Gelatin Hydrolysis

109
Q

POS reaction in Gelatin Hydrolysis

A

Partial or total liquefaction at 4C within 14 days.

110
Q

NEG reaction in Gelatin Hydrolysis

A

Complete solidification of the tube at 4C.

111
Q

POS organism in Gelatin Hydrolysis

A

B.subtilis

112
Q

NEG organism in Gelatin Hydrolysis

A

E.coli

113
Q

This test is used to differentiate a pyocyanogenic pseudomonads (as in P. aeruginosa) from another Pseudomonas.

A

Growth at 42 C

114
Q

➢ Used to determine the ability of an organism to grow at 42C.

A

Growth at 42 C

115
Q

POS reaction in Growth at 42 C

A

Good growth at both 35C and 42 C

116
Q

NEG reaction in Growth at 42 C

A

No growth at 42C, but good growth at 35C.

117
Q

(+) Good growth at both 35C and 42 C

A

P.aeruginosa

118
Q

(-) No growth at 42C, but good growth at 35C.

A

Pseudomonas fluorescens

119
Q

This test is used to detect the presence of the enzyme hippuricase.

A

Hippurate test

120
Q

➢ Hippuricase hydrolyzes hippuric acid in the test into glycine and benzoic acid.
➢ Glycine is deaminated by the oxidizing agent ninhydrin, which is reduced during the process.
➢ The end products of ninhydrin oxidation react 22 to form a purple-colored compound.

A

Hippurate test

121
Q

POS reaction in Hippurate test

A

Deep purple color

122
Q

NEG reaction in Hippurate test

A

Colorless or slightly yellow pink

123
Q

POS organism in Hippurate test

A

S.agalactiae

124
Q

NEG organism in Hippurate test

A

S.pyogenes

125
Q

This test is used to identify organism that produce the enzyme tryptophanase.

A

Indole production

126
Q

Used determine the capability of an organism to hydrolyze tryptophan to indole.
Bacteria with tryptophanase are capable of hydrolyzing tryptophan to pyruvate, ammonia, and indole.

A

Indole production

127
Q

Reagents used to detect indole

A

Kovac’s reagent (dimethylamine-
benzaldehyde and HCl)
— Produces red color with indole.

Ehrlich’s reagent (Kovac’s + absolute ethyl alcohol)
— More sensitive for detecting small
amounts of indole.
— Technique of choice for anaerobes.

128
Q

POS reaction in Indole production

A

Pink- to wine-colored ring after addition of appropriate reagent

129
Q

NEG reaction in Indole production

A

No color change after addition of the appropriate reagent

130
Q

Kovac’s Indole Method (+)

A

E. coli

131
Q

Kovac’s Indole Method (-)

A

K.pneumoniae

132
Q

Ehrlich’s Indole method (+)

A

H.influenzae

133
Q

Ehrlich’s Indole method (-)

A

H. parainfluenza

134
Q

Ehrlich’s Indole method (Anaerobic) (+)

A

Porphyromonas assacharolytica

135
Q

Ehrlich’s Indole method (Anaerobic) (-)

A

Bacteroides fragilis

136
Q

This test is used for the presumptive identification of catalase-negative gram-positive cocci.

A

LAP test

137
Q

➢ The LAP disk is a rapid test for the detection of the enzyme leucine aminopeptidase (LAP).
➢ Leucine-beta-naphthylamide-impregnated disks serve as substrate for LAP.
➢ After hydrolysis by LAP the resulting beta- naphthylamine produces RED COLOR upon addition of cinnamaldehyde reagent.

A

LAP test

138
Q

POS reaction in LAP test

A

Development of a red color within 1 minute after adding cinnamaldehyde reagent

139
Q

NEG reaction in LAP test

A

No color change or development of a slight yellow color.

140
Q

POS organism in LAP test

A

Enterococcus faecalis

141
Q

NEG organism in LAP test

A

Aerococcus viridans

MICRO/PARA (5 decks)

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