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BACTERIOLOGY > Tests for Gram-Negative (Enterobact > Flashcards

Tests for Gram-Negative (Enterobact Flashcards

1
Q

Principle of Gram Sure

A

L-alanine-7-amido-4-methylcoumarin + aminopeptidase (from Gram neg) → blue fluorescence

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2
Q

Indicator of Gram Sure

A

Longwave UV light

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3
Q

Incubation for Gram Sure

A

22-25°C for 5-10 minutes

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4
Q

Positive QC for Gram Sure

A

Blue fluorescence (E. coli)

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5
Q

Negative QC for Gram Sure

A

No fluorescence (S. aureus)

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6
Q

Differentiates Enterobacterales from other GN bacilli

A

Oxidase test (Kovac’s method)

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7
Q

Principle of Oxidase Test (Kovac’s Method)

A

Tetramethyl-p-phenylenediamine dihydrochloride + cytochrome oxidase → indophenol

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8
Q

Incubation for Oxidase Test (Kovac’s Method)

A

22-25°C, within 10 seconds

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9
Q

Positive QC for Oxidase Test

A

Dark purple/Deep blue (P. aeruginosa)

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10
Q

Negative QC for Oxidase Test

A

No color change (E. coli)

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11
Q

Aid in ID of Gram-negative along with Gram stain

A

Gram Sure

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12
Q

Differentiates Enterobacterales from other GN bacilli

A

Oxidase test (Kovac’s method)

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13
Q

Positive for all Enterobacteriales/Enterobacteriaceae

A

Nitrate Reduction

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14
Q

Principle of nitrate reduction

A

Nitrate + bacterial nitrate reductase → Nitrite

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15
Q

Medium for nitrate and nitrite reduction

A

Peptone broth

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16
Q

Indicator/Reagent for Solution A in nitrate/nitrite reduction

A

Sulfanilic acid

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17
Q

Indicator/Reagent for Solution B in nitrate/nitrite reduction

A

α-naphthylamine

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18
Q

Durham tube purpose in nitrate/nitrite

A

N2 gas (detection is positive)

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19
Q

Incubation of nitrate and nitrite reduction

A

35-37°C, 48 hours

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20
Q

Positive QC for nitrate reduction

A

RED after addition of indicator (E. coli)

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21
Q

Negative QC for nitrate reduction

A

Colorless or change of color after zinc dust (Acinetobacter baumanii)

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22
Q

Positive QC for nitrite reduction

A

Colorless, gas production (P. mirabilis)

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23
Q

Negative QC for nitrite reduction

A

Red, no gas (Acinetobacter baumanii)

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24
Q

Tests bacteria for oxidative or fermentative ability

A

Oxidation and Fermentation (CDC Method)

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25
Q

Principle for oxidation and fermentation (CDC Method)

A

6 Carbohydrates: Glucose, Xylose, Mannitol, Maltose, Lactose, Sucrose → Acids

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26
Q

Medium for oxidation and fermentation (CDC Method)

A

Agar deep + 1 carbohydrate, Anaerobic: Sterile melted petrolatum or paraffin oil

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27
Q

Indicator/Reagent for oxidation and fermentation (CDC Method)

A

Phenol red

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28
Q

Incubation of OF (CDC Method)

A

35-37°C, Up to 7 days

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29
Q

QC positive for OF method (CDC Method)

A

Yellow (acids); Oxidizer: P. aeruginosa; Fermenter: E. coli

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30
Q

For decarboxylase-producing Enterobacteria

A

Moeller’s decarboxylase test

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31
Q

Principle of Moeller’s test

A

Lysine → Cadaverine; Ornithine → Putrescine; Arginine → Citrulline

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32
Q

Medium for Moeller’s decarboxylase test

A

Moeller’s decarboxylase medium, add 4mm Mineral oil

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33
Q

Indicator of Moeller’s decarboxylase test

A

Bromocresol purple and Cresol red

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34
Q

Incubation period for Moeller’s decarboxylase test

A

35-37°C, Examine at 24, 48, 72, and 96 hours

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35
Q

Positive QC for Moeller’s Decarboxylase test Lysine (purple)

A

K. pneumoniae

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36
Q

Positive QC for Moeller’s Decarboxylase test Ornithine (purple)

A

K. aerogenes

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37
Q

Positive QC for Moeller’s Decarboxylase test Arginine (purple)

A

P. aeruginosa

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38
Q

Negative QC for Moeller’s Decarboxylase test Arginine

A

E. coli

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39
Q

Negative QC for Moeller’s Decarboxylase test Ornithine

A

P. vulgaris

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40
Q

Negative QC for Moeller’s Decarboxylase test Lysine

A

C. freundii

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41
Q

LIA is a test for

A

Enterobacterales/Enterobacteriaceae

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42
Q

Principle of LIA aerobic and anaerobic

A

Aerobic Slant: Lysine; Anaerobic Butt: Glucose

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43
Q

Purple slant LIA (K)

A

Lysine decarboxylase

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44
Q

Red slant (R) LIA

A

Lysine deamination

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45
Q

Glucose fermentation (A) color

A

Yellow butt (A)

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46
Q

Black precipitate in LIA indicates

A

H2S production

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47
Q

Lysine Iron Agar reactions: Positive Lysine decarboxylation (LDC+)

A

K/K (ALK/ALK)

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48
Q

Lysine Iron Agar reactions: Negative Lysine decarboxylation (LDC-)

A

K/A (ALK/ACD)

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49
Q

Lysine Iron Agar reactions: Positive Lysine deamination (LDA+)

A

R/A or R/Y

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50
Q

Indicator for LIA

A

Bromocresol Purple; Ferric ammonium citrate (H2S)

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51
Q

Incubation for LIA

A

35-37°C, 18-24 hours

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52
Q

Positive QC for LIA Lysine decarboxylation (K/K)

A

Klebsiella, E. coli, Edwardsiella, Salmonella, Serratia

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53
Q

Positive QC for LIA Lysine deamination and glucose fermentation (R/A or R/Y)

A

PMP group

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54
Q

Quality control K/A LIA

A

E. coli

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55
Q

Quality control R/A LIA

A

Proteus mirabilis

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56
Q

LIA negative for Lysine decarboxylation, positive for glucose fermentation only (K/A)

A

Citrobacter, Shigella

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57
Q

Triple Sugar Iron (TSI) test for Enterobacterales contents (LSG)

A

Aerobic Slant: Lactose (10%), Sucrose (10%); Anaerobic Butt: Glucose (1%)

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58
Q

Medium: TSI Agar reactions

A

K: Alkaline (Red); A: Acid (Yellow); H2S: Black ppt.; g: Small gas (Bubble); G: Large gas (Cracks)

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59
Q

Reaction interpretations for TSI Ⓐ

A

E. coli

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60
Q

Reaction interpretations for TSI K/A, g/G, H2S+

A
  • Salmonella enterica subsp. enterica serovar Typhimurium
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61
Q

Reaction interpretations for TSI K/A, H2S+

A

P. mirabilis

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62
Q

Reaction interpretations for TSI K/A

A

Shigella flexneri

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63
Q

Reaction interpretations for TSI K/K

A

P. aeruginosa

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64
Q

Indicators for TSI

A

Phenol Red (acid production), Ferric ammonium citrate (H2S)

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65
Q

Incubation for TSI

A

35-37°C, 18-24 hours

66
Q

Gelatin hydrolysis test purpose

A

Positive for Moraxella lacunata, Serratia orodifera, Proteus spp., Pseudomonas

67
Q

Principle of gelatin hydrolysis

A

Gelatin + gelatinase → liquefaction (refrigerated)

68
Q

QC for gelatin hydrolysis Partial or total liquefaction at 4°C

A

Bacillus subtilis

69
Q

QC for gelatin hydrolysis Complete solidification at 4°C

A

E. coli

70
Q

Principle of fermentation media for differentiating enteric bacteria from Coryneforms

A

Glucose → Pyruvate

71
Q

Medium for fermentation of enteric bacteria from Coryneforms

A

Peptone medium + 1 drop BHI culture

72
Q

Indicator for fermentation media for enteric bacteria from Coryneforms

A

Andrade’s indicator

73
Q

Gas detection method in fermentation media for enteric bacteria from Coryneforms

A

Durham tube

74
Q

Incubation conditions for fermentation media of enteric bacteria from Coryneforms

A

35-37°C, Up to 7 days

75
Q

QC reactions for fermentation media for enteric bacteria from Coryneforms (positive)

A

Pink with gas: E. coli; Pink without gas: S. flexneri

76
Q

QC reactions for fermentation media for enteric bacteria from Coryneforms (negative)

A

Clear or straw, no gas: Coryneforms

77
Q

Fermentation media to differentiate Enterococci from Streptococci medium

A

Broth + 2 drops of BHI culture

78
Q

Indicator of fermentation media to differentiate Enterococci from Streptococci

A

Bromocresol purple

79
Q

Incubation period for fermentation media to differentiate Enterococci from Streptococci

A

35-37°C, 4 days

80
Q

Positive QC for fermentation media to differentiate Enterococci from Streptococci

A

Yellow with gas: E. coli

81
Q

Negative QC for fermentation media to differentiate Enterococci from Streptococci

A

Pink, no gas: Moraxella osloensis

82
Q

ONPG test purpose

A

Distinguishes late lactose fermenter from non-lactose fermenters

83
Q

ONPG test principle

A

ONPG + β-galactosidase → o-nitrophenol (yellow)

84
Q

Incubation for ONPG test

A

37°C, 4 hours

85
Q

QC for ONPG test Positive

A

Yellow: Shigella sonnei

86
Q

Negative QC for ONPG test

A

Colorless: Salmonella enterica serovar Typhimurium

87
Q

Spot indole test purpose

A

Rapid ID of indole positive organisms (e.g., E. coli)

88
Q

Spot indole test principle

A

1% p-dimethylamino-cinnamaldehyde + tryptophanase → blue

89
Q

Incubation for spot indole test

A

22-25°C, within 30 seconds

90
Q

QC for spot indole test positive

A

Blue within 20 seconds: E. coli

91
Q

QC for spot indole test negative

A

Slight pink/No color change: K. pneumoniae

92
Q

Indole positive reaction bacteria in IMViC (PEKPEC)

A

PMP group E. coli, Klebsiella oxytoca, Plesiomonas, Edwardsiella, Citrobacter koseri

93
Q

Positive for Methyl red in IMViC (CEPSS)

A

Citrobacter, E. coli, PMP, Salmonella, Shigella

94
Q

IMViC bacteria positive for Voges-Proskauer (Barritt’s method)(KESH)

A

Klebsiella, Enterobacter, Serratia, Hafnia

95
Q

Acetate Utilization purpose

A

Differentiate E. coli from Shigella

96
Q

Urease (Christensen’s method) purpose

A

Presumptive ID of Proteus spp. and other enterobacteria

97
Q

Motility test purpose

A

Detects motile organisms

98
Q

MUG test purpose

A

Detection of EHEC/E. coli O157:H7 (no fluorescence)

99
Q

PAD test purpose

A

Detects PMP/PPM group (Positive)

100
Q

String test purpose

A

Rapid detection of Vibrio spp.

101
Q

Principle for indole

A

Tryptophan + tryptophanase → indole (detected by indicators)

102
Q

Medium for Indole

A

SIM (20-25°C), Tryptophan broth (35°C)

103
Q

Indicator for indole (positive for Enterobacterales/Enterobacteriaceae)

A

Kovac’s reagent

104
Q

Composition of Kovac’s reagent

A

Dimethylamine-benzaldehyde & HCl

105
Q

Composition of Ehrlich’s reagent

A

Dimethylamine-benzaldehyde & HCl, Absolute ethanol, Xylene

106
Q

Incubation of indole

A

35-37°C, 48 hours

107
Q

Positive QC for Indole Kovac’s reagent

A

Pink/Wine color ring after addition of Kovac’s reagent (E. coli)

108
Q

Positive QC for Indole Ehrlich’s reagent

A

H. influenzae and Porphyromonas asaccharolytica

109
Q

Negative QC for Indole Kovac’s reagent

A

K. pneumoniae

110
Q

Negative QC for Indole Ehrlich’s reagent

A

H. parainfluenzae and Bacteroides fragilis

111
Q

Principle for Methyl Red

A

Carbohydrate → mixed acids; Acids make pH < 4.4 (positive)

112
Q

Medium for Methyl Red and Voges-Proskauer

A

MRVP medium or Clark & Lubs medium

113
Q

Incubation for Methyl Red

A

35-37°C, 48 hours

114
Q

Positive QC for Methyl Red

A

E. coli

115
Q

Negative QC for Methyl Red

A

Yellow - K. aerogenes

116
Q

Voges-Proskauer (Barritt’s method) principle

A

Carbohydrate → 2,3-Butanediol or acetoin (end product)

117
Q

Voges-Proskauer (Barritt’s method) indicator

A

Solution A: ɑ-naphthol; Solution B: KOH

118
Q

Positive QC for Voges-Proskauer

A

Red (K. aerogenes)

119
Q

Negative QC for Voges-Proskauer

A

Yellow (E. coli)

120
Q

Principle for Citrate Utilization Test

A

Citrate → Ammonium PO4 and Ammonium hydroxide

121
Q

Medium for Citrate Utilization Test

A

Simmons citrate agar slant

122
Q

Indicator for Citrate Utilization Test

A

Bromothymol blue

123
Q

Incubation for Citrate Utilization Test

A

35-37°C, Up to 7 days

124
Q

Positive QC for Citrate Utilization Test

A

Blue (K. aerogenes)

125
Q

Negative QC for Citrate Utilization Test

A

Small/No growth; Green (E. coli)

126
Q

Acetate (Malonate, Acetamide) Utilization principle

A

Ability to use Sodium acetate as sole source of carbon

127
Q

Medium for Acetate Utilization

A

Acetate slant

128
Q

Indicator for Acetate Utilization

A

Bromothymol blue

129
Q

Incubation for Acetate Utilization

A

35-37°C, Up to 7 days

130
Q

Positive QC for Acetate Utilization Test

A

Growth; Blue (E. coli)

131
Q

Negative QC for Acetate Utilization Test

A

Small/No growth; Green (S. sonnei)

132
Q

Urease (Christensen’s method) principle

A

Urea + urease → Ammonium carbonate (alkaline, pH >8.1)

133
Q

Medium for Urease (Christensen’s method)

A

Urease agar slant + 2 drops BHI culture

134
Q

Indicator for Urease (Christensen’s method)

A

Phenol Red

135
Q

Incubation for Urease (Christensen’s method)

A

35-37°C, Up to 7 days

136
Q

Positive QC for Urease (Christensen’s method)

A

Magenta/Red (P. vulgaris)

137
Q

Other positive organisms for Urease (Christensen’s method)

A

Klebsiella, PMP group, Nocardia, Rhodococcus, Helicobacter, Ureaplasma, Cryptococcus

138
Q

Negative QC for Urease (Christensen’s method)

A

Light Orange/Yellow (E. coli)

139
Q

Motility test principle

A

Motile bacteria produce a diffuse zone of growth

140
Q

Motility test agar

A

Semisolid Gelatin butt

141
Q

Incubation for Motility test

A

35-37°C, Up to 7 days

142
Q

Positive QC for Motility test

A

Spreading (P. vulgaris)

143
Q

Negative QC for Motility test

A

Colonies remain on site of stab (K. pneumoniae)

144
Q

MUG test principle

A

4-methylumbelliferyl-β-d-glucuronide + β-d-glucuronidase → 4-methylumbelliferyl

145
Q

Medium for MUG test

A

MUG disk, add drop of water and incubate at 35°C for 2 hours

146
Q

Indicator for MUG test

A

366 nm Ultraviolet light

147
Q

Incubation for MUG test

A

35-37°C, 2 hours, Closed container

148
Q

Positive QC for MUG test

A

Electric Blue fluorescence (All E. coli except O157:H7)

149
Q

Negative QC for MUG test

A

No fluorescence (K. pneumoniae, E. coli O157:H7)

150
Q

Principle for PAD test

A

Phenylalanine + PAD → ammonia and phenylpyruvic acid

151
Q

Medium for PAD test

A

PAD agar/slant

152
Q

Indicator for PAD test

A

10% FeCl3

153
Q

Incubation for PAD test

A

35-37°C, 18-24 hours

154
Q

Positive QC for PAD test

A

GREEN (P. mirabilis)

155
Q

Negative QC for PAD test

A

Yellow (E. coli)

156
Q

String test principle

A

0.5% Sodium deoxycholate lyses DNA of VIBRIO only, forming a string

157
Q

String test medium

A

In glass slide + bile

158
Q

Incubation period for String test

A

22-25°C, Within seconds

159
Q

Positive QC for String test

A

String-like formation between loop and slide (Vibrio spp.)

160
Q

Negative QC for String test

A

No string formation

BACTERIOLOGY (49 decks)

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