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Gram Negative Algorithm Flashcards

1
Q

What are the Gram-negative diplococci?

A

Neisseria meningitidis

Neisseria gonorrhoeae

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2
Q

What lab test can you use to differentiate between the Gram-negative diplococci?

A

Neisseria meningitidis ferments maltose (and glucose). Neisseria gonorrhoeae does not ferment maltose (it can only ferment glucose).

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3
Q 
What bacteria is:
pink on Gram-stain
diplococci
oxidase +, catalase +
motile, capsule
maltose fermenter, glucose +
A

Neisseria meningitidis

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4
Q 
What bacteria is: 
pink on Gram stain
diplococci
oxidase +, catalase + 
motile (twitching), no capsule 
maltose -, glucose +
A

Neisseria gonorrhoeae

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5
Q 
What bacteria is: 
pink on Gram stain
diplococci
oxidase +, catalase +
non motile, capsule variable
maltose +, glucose +, lactose +, sucrose + 
DNase + 
Pinkish brown hockey puck colonies on CHOC
A

Moraxella catarrhalis

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6
Q

Which diplococci has a distinctive feature of pinkish brown hockey puck colonies on CHOC?

A

Moraxella catarrhalis

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7
Q

What are 2 key lab tests to distinguish among the Gram-negative rods?

A

1) if it ferments lactose
2) if it ferments lactose fast or slow (among lactose fermenters)
3) if it has oxidase (among non-lactose fermenters)

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8
Q

Differentiating between fast lactose fermenters

A
  • IMViC
    - > E coli: IMViC ++–
    - > Klebsiella IMViC –++
    - > Enterobacter IMViC –++
  • Motility
    - > E. coli: Motile
    - > Klebsiella: Non-motile
    - > Enterobacter: Motile
  • Urease
    - > E. coli: Urease -
    - > Klebsiella: Urease +
    - > Enterobacter: Urease -
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9
Q

Growth on EMB Agar for E. coli vs Klebsiella

A

E coli: black colonies with metallic sheen

Klebsiella: purple colonies

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10
Q

Which gram -ve fast lactose fermenter bacilli has distinctive feature of a capsular halo on gram stain?

A

Klebsiella

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11
Q

Name the bacteria:

  • Glucose +, Maltose +
  • IMViC ++ - - (Indole +, Methyl Red +, Voges-Proskauer -, Citrate Utilization -)
  • Urease -
  • Motile (flagella)
  • Growth on Eosin Methylene Blue (EMB) Agar = black colonies with metallic sheen
  • can cause disease in anyone
  • TSIA: A/A (Acid slant/Acid butt) gas +, H2S -
A

E coli

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12
Q

Name the bacteria:

  • Glucose +, Maltose +, Sucrose +
  • IMViC - - ++ (Indole-, MR -, VP+, Citrate+)
  • Urease +
  • Non motile
  • Growth on Eosin Methylene Blue (EMB) Agar = purple colonies
  • Capsule, capsular halo on gram stain
  • can cause disease in anyone
  • TSIA: A/A (Acid slant/Acid butt) gas +, H2S -
A

Klebsiella

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13
Q

Name the bacteria:

  • Glucose + , Maltose +, Sucrose +
  • Oxidase -, catalase +
  • IMViC - - + + (Indole -, MR -, VP+, Citrate +)
  • Urease -
  • Motile, non-capsulated
  • opportunistic pathogen
  • TSIA: A/A (Acid slant/Acid butt) gas +, H2S -
A

Enterobacter

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14
Q

Ways to differentiate slow lactose fermenters

A

Citrobacter
IMViC - + - +
No red pigment
TSIA: A/A +, +/-

Serratia
IMviC - - + +
Red pigmented colonies (Prodigiosin)
TSIA: K/A - -

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15
Q

Name the bacteria

  • IMViC - + - + (Indole -, MR +, VP -, Citrate +)
  • Motile
  • No red pigment
  • TSIA: A/A +, +/- (Acid slant/Acid butt, gas+, H2S +/-)
A

Citrobacter

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16
Q

Name the bacteria

  • IMViC - - + + (Indole -, MR -, VP +, Citrate +)
  • Motile
  • Red pigmented colonies due to Prodigiosin (anti-cancer, anti-microbial, anti-oxidant and immunosuppressant)
  • TSIA: K/A - - (Alkaline slant/ Acid butt, gas -, H2S -)
  • opportunistic pathogen
A

Serratia

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17
Q

Which gram negative slow lactose fermenter has distinct red pigmented colonies?

A

Serratia

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18
Q

IMViC for Citrobacter

A
      • +
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19
Q

IMViC for Serratia

A
      • +
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20
Q

Name fast lactose fermenting gram negative bacteria

A

E. coli, Klebsiella, Enterobacter

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21
Q

Name slow lactose fermenting gram negative bacteria

A

Citrobacter, Serratia

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22
Q

Non lactose fermenters are colourless on MacConkey (T/F)

A

True

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23
Q

How can we separate NLFs (Non Lactose Fermenters)?

A

Split into oxidase + and -

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24
Q

Oxidase + NLF

A

Pseudomonas

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25
Q

Two distinct features of Pseudomonas

A

Blue green pigment

Grape odour

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26
Q

Name the bacteria

  • IMViC - - - + (Indole -, MR -, VP -, Citrate +)
  • Motile
  • Urease +
  • TSIA: K/K + + (Alkaline slant/Alkaline butt, gas+, H2S+)
  • Blue-green pigment
  • Grape odour
  • P. aeruginosa grows on cetrimide selective media
A

Pseudomonas

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27
Q

Give IMViC for Pseudomonas

A
      • +
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28
Q

Pseudomonas is non motile (T/F)

A

False

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29
Q

Oxidase - NLF

A

Shigella, Salmonella, Proteus

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30
Q

Differentiating between the gram negative, oxidase -ve, NLFs

A 
- Growth on Salmonella Shigella Agar
    Shigella: green colonies
    Salmonella: black colonies
- IMViC
     Shigella: - + - -
     Salmonella: - + - - 
     Proteus: - + - +
- TSIA
     Shigella: K/A - - 
     Salmonella: K/A + + 
     Proteus: K/A + +
- Motility 
      Shigella: Non-motile  
      Salmonella: Motile
      Proteus: Swarming motility
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31
Q

Name the bacteria:

  • Catalase +, Oxidase -
  • IMViC - + - - (Indole -, MR +, VP -, Citrate -)
  • Non-motile
  • TSIA: K/A - - (Alkaline slant/ Acid butt, gas -, H2S -)
  • Green colonies on Haktoen/Salmonella Shigella Agar
A

Shigella

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32
Q

Which of the gram negative, oxidase -ve, NLFs is non motile?

A

Shigella

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33
Q

Give IMViC for Shigella

A
      • -
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34
Q

Give TSIA for Shigella

A

K/A - -

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35
Q

Name the bacteria:

  • Catalase +, Oxidase -
  • IMViC - + - - (Indole -, MR +, VP -, Citrate -)
  • Motile
  • TSIA: K/A + + (Alkaline slant/Acid butt, gas +, H2S +)
  • Black colonies on Haktoen/Salmonella Shigella Agar and XLD Agar
A

Salmonella

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36
Q

Which of the gram negative, oxidase -ve, NLFs shows black colonies on XLD Agar?

A

Salmonella

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37
Q

Give IMViC for Salmonella

38
Q

Give TSIA for Salmonella

39
Q

Name the bacteria:

  • Catalase +, Oxidase -
  • IMViC - + - + (Indole -, MR +, VP -, Citrate +)
  • Motile (swarming on BA= thin layer arranged circular)
  • Fishy odour
  • TSIA: K/A ++ (Alkaline slant/ Acid butt, gas +, H2S +)
  • opportunistic pathogen
40
Q

Which of the gram negative, oxidase -ve, NLFs has swarming motility on BA?

41
Q

Give IMViC for Proteus

42
Q

Give TSIA for Proteus

43
Q

Curved rods

A

Growth
V. cholera: hemodigestion in areas of confluent growth on BA but non hemolytic
Growth on TCBS (yellow colonies)/peptone water
C. jejuni: Swarming growth on moist agar
Grey, convex, glistening, non-hemolytic on BA
H. pylori
More difficult to grow on BA
Growth on Skirrow’s medium, transparent colonies

Flagella
V. cholerae
- Single flagellum
C. jejuni
- Capsule, Single flagellum
H. pylori
- 6-8 flagella

String test
V. cholerae +
C. jejuni -
H pylori -

Urease test
V cholera
- Urease -
C. jejuni
- Urease - 
H. pylori 
- Urease ++
44
Q

Name the Curved gram -ve rods and how we can differentiate them

A

V. cholerae, C. jejuni, H. pylori

Growth
V. cholera: hemodigestion in areas of confluent growth on BA but non hemolytic
Growth on TCBS (yellow colonies)/peptone water
C. jejuni: Swarming growth on moist agar
Grey, convex, glistening, non-hemolytic on BA
H. pylori
More difficult to grow on BA
Growth on Skirrow’s medium, transparent colonies

Flagella
V. cholerae
- Single flagellum
C. jejuni
- Capsule, Single flagellum
H. pylori
- 6-8 flagella

String test
V. cholerae +
C. jejuni -
H pylori -

Urease test
V cholera
- Urease -
C. jejuni
- Urease - 
H. pylori 
- Urease ++
45
Q

Name the gram -ve, curved bacteria:

  • IMViC + - v + (Indole +, MR -, VP variable, Citrate +)
  • +ve string test
  • Non hemolytic (only take observations from isolated colonies due to hemodigestion in areas of confluent growth)
  • Urease -
  • Motile
  • Single flagellum
  • Growth on Thiosulphate Citrate Bile Salt (TCBS) (yellow colonies due to sucrose fermentation)/ alkaline peptone water
A

Vibrio cholera

46
Q

Which gram -ve, curved bacterium has yellow colonies on TCBS due to sucrose fermentation?

A

V. cholerae

47
Q

Which gram -ve, curved bacterium has a +ve string test?

A

V. cholerae

48
Q

Which gram -ve, curved bacterium requires salt supplementation for optimal growth?

A

V. cholerae

49
Q

Coalesce - define

A

come together to form one mass or whole.

50
Q

Preliminary identification of Campylobacter species from primary culture is by ?

A

Colonial appearance,
Gram stain,
Growth in oxygen,
Oxidase test, Hippurate test

51
Q

Name the bacterium:

  • Catalase +, Oxidase +
  • Urease -
  • Motile
  • Capsulated, single flagellum
  • Non-hemolytic, grey, convex, glistening
  • Colonies coalesce on moist agar and do exhibit swarming growth
  • Hippurate hyrolysis + (only spp of Campylobacter to hydrolyze hippurate)
  • RAPID test (stool/body tissue)
A

Campylobacter jejuni

52
Q

Which gram -ve, curved bacterium has swarming growth on BA?

53
Q

Which gram -ve, curved bacteria have a single flagella?

A

V. cholerae, C. jejuni

54
Q

Which gram -ve, curved bacterium grows on TCBS/peptone water?

A

V. cholerae

55
Q

In order to optimize the diagnosis ofH. pylori, it is usually recommended that several tests be used together (T/F)

56
Q

In order to optimize the diagnosis ofH. pylori, it is usually recommended that several tests be used together, what are these tests?

A
  1. Serology: measure pylori IgG antibodies via fecal antigen, urea breath test.
  2. Microscopy (gold std):
  3. Culture: - Growth on Skirrow’s medium
  4. Rapid Urease Testing (RUT): Urease ++
57
Q

Name the bacterium:

  1. Serology: measure pylori IgG antibodies to see if person is infection via fecal antigen, urea breath test.
  2. Microscopy (gold std): - Curved, gram -ve rods, 6-8 flagella
  3. Culture: - Growth on Skirrow’s medium = transparent colonies
  4. Rapid Urease Testing (RUT) indicated by change in pH indicator = Urease ++
    - Catalase +, Oxidase +
    - Motile
A

Helicobacter pylori

58
Q

Which gram -ve, curved bacterium grows on Skirrow’s medium as transparent colonies?

59
Q

Which gram -ve, curved bacterium has 6-8 flagella?

60
Q

Which gram -ve, curved bacterium is urease ++ ?

61
Q

Which gram -ve, curved bacterium is more difficult to grow on BA?

62
Q

Which gram -ve, curved bacterium is grey, convex, glistening, non-hemolytic on BA

63
Q

Match the bacteria based on growth on BA:
1. Grey, convex, glistening, non-hemolytic on BA
2. Hemodigestion in areas of confluent growth on BA but non hemolytic
3. More difficult to grow on BA
V. cholerae, C. jejuni, H. pylori

A
  1. C. jejuni,
  2. V. cholerae,
  3. H. pylori
64
Q

Skirrows medium: has _ Vancoymcin, _ Polymyxin, _ Trimethroprim

A

Skirrows medium: has 1 Vancoymcin, 2 Polymyxin, 3 Trimethroprim

65
Q

Name the gram-ve coccobacilli and how we can differentiate them

A

H. influenzae, Bordetella pertussis, Brucella, Francisella tularensis, Pasteurella multicoda

66
Q

What gram-ve coccobacilli requires factors V and X for growth?

A

Haemophilus influenzae

67
Q

No growth on BA, gray, opaque, large colonies on CHOC, this describes which gram -ve coccobacilli?

A

Haemophilus influenzae

68
Q

What gram-ve coccobacilli is oxidase + with +ve satellite test?

A

Haemophilus influenzae

69
Q

Name the bacteria:

  • Coccobacilli
  • Oxidase +, Catalase +
  • No growth on BA, growth on CHOC = gray, opaque, large colonies
  • Growth factor requirement test (factor V and X) / Satellite test
  • Slide agglutination serotyping (determines capsular serotype)
A

Haemophilus influenzae

70
Q

Bordet-Gengou agar contains blood, _______ extract, glycerol with _______/penicillin

A

Bordet-Gengou agar contains blood, potato extract, glycerol with cephalexin/penicillin

71
Q

Name the gram-ve, coccobacilli:

  • Bordet-Gengou agar gives dome-shaped, small, pearl-like, opaque colonies
  • Detected via fluorescent antibody/PCR
A

Bordetella pertussis

72
Q

Pearl-like, opaque colonies on Bordet-Gengou agar can be seen in what gram -ve bacterium?

A

Bordetella pertussis

73
Q

What are other tests used to ID Bordetella pertussis?

A

Fluorescent antibody/PCR

74
Q

Brucella easily mistaken for Haemophilus, what is a test used to differentiate the two?

A

Satellite test
Brucella = no satellitism
H influenzae = satellitism

75
Q

If Brucella is Urease + what is the next test done?

A

Phenylalanine deaminase test (PDA)

76
Q
  • BA, CHOC, Brucella agar
    Brucellagrows on both Blood and Chocolate agar without satelliting around staphylococcus.
  • Catalase +, Oxidase +
  • Rapid urease test +
  • If urease + do Phenylalanine deaminase test (PDA)
77
Q

Culture and isolation ofFrancisella tularensisis easy (T/F)

A

False; Culture and isolation ofFrancisella tularensisis difficult

78
Q

The medium of choice for F. tularensis is ________ _______ blood agar

Good growth has also been achieved on modified ______-______ broth, ______ agar supplemented with IsoVitale X and modified ______ yeast extract agar.

A

The medium of choice for F. tularensis is cysteine glucose blood agar

Good growth has also been achieved on modified Mueller-Hinton broth, chocolate agar supplemented with IsoVitale X and modified charcoal yeast extract agar.

79
Q

Biochemical tests aren’t particularly used for F. tularensis (T/F)

80
Q

Blue-gray, round, smooth and slightly mucoid colonies - which gram -ve coccobacilli?

A

Francisella tularensis

81
Q

Name the gram -ve bacterium

  • Growth on:
    - - Cysteine glucose BA
    - - Modified Mueller-Hinton broth
    - - CHOC with IsoVitale X
    - - Modified charcoal yeast extract agar
  • Colonies are blue-gray, round, smooth and slightly mucoid.
  • On BA, a small zone of alpha-hemolysis surrounds colony.
  • Slide agglutination tests / direct fluorescent antibody using commercially-available antisera for ID
A

Francisella tularensis

82
Q

Tularemia is not often confirmed by serology (T/F)

A

False; Tularemia is most frequently confirmed by serology

83
Q

Pasteurella multicoda can be contracted from a dog bite (T/F)

84
Q

Name the bacterium:
- Oxidase +
- Capsulated
- Non-motile
- Bipolar staining with Giesma/ methylene blue
- No growth on MAC
- ‘Safety pin’ appearance
- Grows well on CBA (Columbia Blood Agar), CHOC
- Ferments glucose, sucrose with little/no gas
- Weak acid production in TSIA
- Colonies grey and viscous but rough irregular colonies occur frequently.
- Strong mucinous odour resembling H. influenzae
- On CHOC - round, greyish/ yellowish colonies
Butterfly colonies may also occur.
- No haemolysis on BA - butterfly colonies

A

Pasteurella multicoda - dog bite

85
Q

We differentiate 3 subspecies of Pasteurella by ?

A

Sorbitol and dulcitol fermentation

86
Q

Differentiation of Pasteurella strains (multicoda, septica, gallicida)

A

multocida strains - ferment sorbitol but do not ferment dulcitol;
septica strains - negative rxns for sorbitol and dulcitol fermentation,
gallicida strains - ferment both sorbitol and dulcitol.

87
Q

Which gram -ve coccobacilli has a safety pin appearance

A

Pasteurella multicoda

88
Q

Which gram -ve coccobacilli has butterfly colonies on BA/CHOC?

A

Pasteurella multicoda

89
Q

Which gram -ve coccobacilli has weak acid production in TSIA?

A

Pasteurella multicoda

90
Q

Which gram -ve coccobacilli has strong odour resembling H. influenzae?

A

Pasteurella multicoda

91
Q

Name the bacterium:
- Oxidase +
- Capsulated
- Non-motile
- Bipolar staining with Giesma/ methylene blue
- No growth on MAC
- ‘Safety pin’ appearance
- Grows well on CBA (Columbia Blood Agar), CHOC
- Ferments glucose, sucrose with little/no gas
- Weak acid production in TSIA
- Colonies grey and viscous but rough irregular colonies occur frequently.
- Strong mucinous odour resembling H. influenzae
- On CHOC - round, greyish/ yellowish colonies
Butterfly colonies may also occur.
- No haemolysis on BA - butterfly colonies

A

Pasteurella multicoda - dog bite

92
Q

Non haemolytic, grey, butterfly colonies on BA and non motile, which gram - coccobacilli?

A

Pasteurella multicoda

Lab Diagnostics (12 decks)

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