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Bacteriology 🦠 > (1) Gram Negative Bacilli > Flashcards

(1) Gram Negative Bacilli Flashcards

1
Q

What is the purpose of the Oxidase Test?

A

To identify bacteria that produce cytochrome oxidase, which turns indophenol blue.

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2
Q

What is the main reagent used in the Oxidase Test?

A

Tetramethyl-p-phenylenediamine dihydrochloride.

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3
Q

What is a positive result in the Oxidase Test?

A

A bluish-purple color, indicating the presence of cytochrome oxidase.

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4
Q

Which organisms are positive and negative in the Oxidase Test?

A

Positive: Pseudomonas; Negative: E. coli

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5
Q

What is the purpose of the Nitrate Reduction Test?

A

To determine if an organism can reduce nitrate (NO₃) to nitrite (NO₂).

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6
Q

What are the main reagents used in the Nitrate Reduction Test?

A

Sulfanilic acid and α-naphthylamine

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7
Q

What does a positive result look like in the Nitrate Reduction Test?

A

A red color, indicating nitrate reduction

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8
Q

What does a colorless result mean after adding zinc dust in the Nitrate Reduction Test?

A

True positive, indicating complete nitrate reduction beyond nitrite.

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9
Q

What does a red color after adding zinc dust in the Nitrate Reduction Test indicate?

A

True negative, meaning nitrate was not reduced.

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10
Q

What is the purpose of the ONPG Test?

A

To test for beta-galactosidase enzyme, which indicates lactose fermentation.

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11
Q

What is a positive result in the ONPG Test?

A

A yellow color, showing the presence of beta-galactosidase.

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12
Q

What is the purpose of the LOA Test?

A

To determine the presence of amino acid decarboxylase activity in organisms like Enterics, Aeromonas, Vibrio, and Plesiomonas.

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13
Q

What medium is used in the LOA Test?

A

Moeller’s Decarboxylase Medium.

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14
Q

What indicator is used in the LOA Test?

A

Bromcresol purple

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15
Q

What is a positive result in the LOA Test?

A

A purple color, indicating the production of amine products.

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16
Q

What does a yellow result mean in the LOA Test?

A

Negative result, indicating no production of amine products.

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17
Q

What is the purpose of the Triple Sugar Iron (TSI) Test?

A

To differentiate bacteria based on sugar fermentation, gas production, and hydrogen sulfide (H2S) production.

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18
Q

What indicator is used in the TSI Test?

A

Phenol red, which shows pH changes

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19
Q

What indicates H2S production in the TSI Test?

A

Black discoloration due to ferrous sulfate.

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20
Q

When is H2S seen in the TSI Test?

A

Only under acidic conditions.

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21
Q

How is gas production shown in the TSI Test?

A

By splits or cracks in the medium.

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22
Q

What are the conditions in the slant and butt of the TSI medium?

A

Slant: Aerobic; Butt: Anaerobic.

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23
Q

What does an A/A (yellow/yellow) result indicate in TSI?

A

2-3 sugars were fermented;
gas production may create space at the bottom (A/A + gas).

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24
Q

What does a K/A (red/yellow) result indicate in TSI?

A

Only glucose was fermented.

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25
Q

What does a K/K (red/red) result indicate in TSI?

A

No sugars were fermented; typical of non-fermenters like Pseudomonas.

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26
Q

What is the purpose of the Lysine Iron Agar (LIA) Test?

A

To determine an organism’s ability to decarboxylate or deaminate lysine and produce H2S.

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27
Q

What medium and indicator are used in the LIA Test?

A

Moeller’s Medium with bromcresol purple as the pH indicator.

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28
Q

What indicates H2S production in the LIA Test?

A

Ferric ammonium citrate.

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29
Q

What does a positive lysine decarboxylation (LDC) result look like in LIA?

A

Purple color in the butt, indicating decarboxylation under anaerobic conditions.

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30
Q

What does a negative lysine decarboxylation (LDC) result look like in LIA?

A

Yellow in the butt, indicating no decarboxylation.

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31
Q

What does a positive lysine deamination result look like in LIA?

A

Red color on the slant, indicating deamination under aerobic conditions.

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32
Q

What does a K/K (purple/purple) result indicate in LIA?

A

Positive for decarboxylation

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33
Q

What does a K/A (purple/yellow) result indicate in LIA?

A

Negative for decarboxylation (no reaction/neutral).

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34
Q

What does an R/A (red/yellow) result indicate in LIA?

A

Positive for deamination

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35
Q

What reagent is used in the Indole Test?

A

Kovac’s reagent and Ehrlich’s reagent (PDAB)

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36
Q

What is a positive result in the Indole Test?

A

A red ring, commonly seen in E. coli

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37
Q

What is the purpose of the Rapid Spot Indole Test?

A

To quickly screen for indole production under anaerobic conditions.

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38
Q

What material is used in the Rapid Spot Indole Test?

A

Filter paper impregnated with p-DAC

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39
Q

What does a positive result look like in the Rapid Spot Indole Test?

A

A blue spot indicates the presence of indole.

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40
Q

What pathway does the Methyl Red Test detect in bacteria?

A

The mixed acid pathway of glucose fermentation.

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41
Q

What indicator is used in the Methyl Red Test?

A

Methyl red

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42
Q

What medium is used in the Methyl Red Test?

A

MRVP medium

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43
Q

How long is the Methyl Red Test incubated?

A

3-5 days to achieve turbidity.

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44
Q

What does a yellow result mean in the Methyl Red Test?

A

Negative result, indicating a pH above 4.4.

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45
Q

What is a positive result in the Methyl Red Test?

A

A red color at pH 4.4

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46
Q

What metabolic pathway is detected by the Voges-Proskauer Test?

A

The butylene glycol pathway of glucose fermentation.

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47
Q

What medium is used in the Voges-Proskauer Test?

A

MRVP medium

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48
Q

What are the end products detected in the Voges-Proskauer Test?

A

Acetoin or acetylmethylcarbinol

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49
Q

What reagents are used in Barritt’s Method for the VP Test?

A

α-naphthol and KOH.

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50
Q

What color indicates a positive result in the VP Test (Coblentz Method)?

A

Cherry red or port wine red

51
Q

What color indicates a negative result in the VP Test?

A

Chocolate brown

52
Q

What medium is used in the Citrate Utilization Test?

A

Simmons’ citrate medium.

53
Q

What indicator is used in the Citrate Utilization Test?

A

Bromthymol blue

54
Q

What is the end product in the Citrate Utilization Test?

A

Ammonia

55
Q

What color indicates a positive result in the Citrate Utilization Test?

A

Blue

56
Q

What color indicates a negative result in the Citrate Utilization Test?

A

Green

57
Q

What mediums are used in the Urea Hydrolysis Test?

A

Christensen’s agar or Stuart urea broth

58
Q

What indicator is used in the Urea Hydrolysis Test?

A

Phenol red

59
Q

What color indicates a positive result in the Urea Hydrolysis Test?

A

Fuchsia pink or deep pink

60
Q

What color indicates a negative result in the Urea Hydrolysis Test?

A

Yellow

61
Q

How long can the Urea Hydrolysis Test be incubated?

A

Up to 7 days at 35°C

62
Q

What does a positive result look like in the KCN Broth Test?

A

Turbidity in the broth

63
Q

What does a negative result look like in the KCN Broth Test?

A

Clear broth

64
Q

What genera are positive in the KCN Broth Test?

A

KEPC: Klebsiella, Enterobacter, Proteus, Providencia, Citrobacter

65
Q

What reagent is used in the String Test?

A

0.5% sodium deoxycholate (bile salt)

66
Q

What indicates a positive result in the String Test?

A

String-like colony formation

67
Q

What organism is identified by a positive String Test?

A

Vibrio cholerae

68
Q

What does a positive result look like in the Esculin Hydrolysis Test?

A

Black color, seen in Klebsiella pneumoniae.

69
Q

What does a negative result look like in the Esculin Hydrolysis Test?

A

Yellow color, seen in Shigella flexneri

70
Q

What substrate is used in the MUG Test?

A

4-methylumbelliferyl-D-glucuronide

71
Q

What does a positive colorimetric result look like in the MUG Test?

A

Yellow fluorescence

72
Q

What does a positive fluorogenic result look like in the MUG Test?

A

Electric blue fluorescence, indicating Escherichia coli.

73
Q

Which organism gives a negative result in the MUG Test?

A

Pseudomonas aeruginosa.

74
Q

What does a positive result look like in the Gelatin Hydrolysis Test?

A

Gel liquefies, as seen in Proteus vulgaris.

75
Q

What does a negative result look like in the Gelatin Hydrolysis Test?

A

Gel remains solid, as seen in Enterobacter aerogenes.

76
Q

How long can the Gelatin Hydrolysis Test be incubated?

A

Up to 14 days at 4°C

77
Q

Are all glucose fermenters motile (gram negative bacilli)?

A

Yes, all are motile with peritrichous flagella except Klebsiella spp. and Shigella spp.

78
Q

Which genus is cytochrome oxidase positive among Enterobacteriaceae?

A

Plesiomonas spp.

79
Q

Are Enterobacteriaceae catalase positive and nitrate reducers?

A

Yes, they are catalase positive and nitrate reducers.

80
Q

What are the antigenic structures in Enterobacteriaceae?

A

Capsule (K), cell wall/somatic (O), and flagella (H/Vi)

81
Q

What effect does boiling have on the Vi antigen?

A

Boiling removes the Vi antigen

82
Q

Which organisms are Lactose Fermenters among Enterobacteriaceae?

A

Escherichia coli, Klebsiella spp., Enterobacter spp., Arizona, Citrobacter spp., and Hafnia.

83
Q

Which organisms are Non-Lactose Fermenters among Enterobacteriaceae?

A

Proteus, Morganella spp., Providencia spp., Serratia spp., Salmonella spp., Shigella spp., Yersinia spp., and Plesiomonas spp.

84
Q

What is the Gram stain result and shape of Enterobacteriaceae?

A

Gram-negative bacilli

85
Q

What is another name for Escherichia coli?

A

Colon bacillus

86
Q

Can Escherichia coli be part of normal flora?

A

Yes, it can be either normal flora or pathogenic.

87
Q

What are common infections caused by Escherichia coli?

A

Watery diarrhea (due to enterotoxin), UTI, gram-negative sepsis, neonatal meningitis, nosocomial infections, wound infections, bacteremia, and pneumonia.

88
Q

What is the most common cause of UTI?

A

Escherichia coli

89
Q

What is the role of the K1 antigen in Escherichia coli?

A

It is associated with neonatal meningitis, often acquired during vaginal delivery.

90
Q

What is the #1 cause of gram-negative sepsis?

A

Escherichia coli

91
Q

What is Enterotoxigenic Escherichia coli (ETEC) commonly known to cause?

A

Traveler’s diarrhea (Turista)

92
Q

What type of toxin is produced by ETEC?

A

Cholera-like toxin that is heat-labile.

93
Q

What are common serotypes of ETEC?

A

06, 08, and 025

94
Q

What symptoms are typically caused by ETEC?

A

Watery diarrhea

95
Q

What type of diarrhea does EPEC cause?

A

Infantile diarrhea

96
Q

What is a key virulence structure in EPEC?

A

Pathogenicity island

97
Q

What are common serotypes of EPEC?

A

0111 and 0114

98
Q

What type of diarrhea does EIEC cause?

A

Dysentery-like diarrhea, similar to Shigella.

99
Q

What is the major virulence factor in EIEC?

A

Invasin

100
Q

What does EIEC-infected stool typically contain?

A

Blood and mucus

101
Q

What test is used to detect EIEC virulence?

A

Sereny test (ocular test in animals) showing keratoconjunctivitis as a positive result.

102
Q

What are common serotypes of EIEC?

A

0124, 0143, and 0164

103
Q

What syndromes are caused by EHEC?

A

Hemolytic uremic syndrome (HUS) and hemorrhagic colitis

104
Q

Which organs are primarily affected by EHEC?

A

Kidneys and gastrointestinal tract (GIT).

105
Q

What is the major virulence factor in EHEC?

A

Verotoxin (Shigella-like toxin)

106
Q

What is a notable strain of EHEC?

A

E. coli O157

107
Q

What is the result for EHEC on Sorbitol MacConkey (SMAC) and MUG tests?

A

Sorbitol MacConkey negative and MUG negative

108
Q

What type of diarrhea is associated with EAEC?

A

Both acute and chronic diarrhea

109
Q

What is the major virulence factor in EAEC?

A

Aggregative adhesion fimbriae

110
Q

What unique cell pattern is formed by EAEC?

A

Stacked brick pattern

111
Q

What is another name for Klebsiella pneumoniae?

A

Friedlander’s bacillus

112
Q

Is Klebsiella pneumoniae motile or non-motile?

A

Non-motile

113
Q

What colony characteristic does Klebsiella pneumoniae exhibit on MacConkey agar?

A

Mucoid colony

114
Q

What is the result of the String Test for Klebsiella pneumoniae?

A

Positive

115
Q

What are the TSI and LIA results for Klebsiella pneumoniae?

A

TSI: A/A + gas; LIA: K/K

116
Q

What is the IMViC result for Klebsiella pneumoniae?

A

(-) (-) (+) (+)

117
Q

What infections can Klebsiella pneumoniae cause?

A

Pneumonia, wound infection, meningitis, and UTI

118
Q

What is a distinctive characteristic of Proteus spp. on Blood Agar Plate (BAP)?

A

Proteus spp. swarms on BAP

119
Q

What are the TSI results for Proteus spp.?

A

TSI: K/A + gas + H2S.

120
Q

What is the second leading cause of UTI?

A

Proteus spp.

121
Q

What phenomenon is associated with Proteus spp.?

A

Dienes phenomenon (+)

122
Q

What type of stones can Proteus spp. induce?

A

Renal stones, due to urease production (NH4 carbonate)

123
Q

What is the medium used for Indole test?

A

SIM Medium (Sulfide Indole Motility

Bacteriology 🦠 (2 decks)

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