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LABORATORY DIAGNOSIS OF ENTEROBACTERIACEAE Flashcards

1
Q

Enterobacteriaceae specimens

A

Stool, rectal swab, blood and urine

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2
Q

The members of Enterobacteriaceae are commonly isolated from _____ specimens because identification should only be performed with true intestinal pathogens.

A

stool

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3
Q

Enterics that are isolated from sterile site such as Salmonella from _______ aspirates are highly significant

A

bone marrow

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4
Q

in gram staining, the Enterobacteriaceae appears

A

Straight Gram-negative rods or coccobacilli with rounded ends.

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5
Q

Stain that can be used to observe the bipolar bodies of Y. pestis

A

Wayson Stain

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6
Q

culture medias of Enterobacteriaceae

A

BAP, CAP, MAC, HEA, XLD agar, CIN agar, Salmonella Shigella agar, EMB, bismuth sulfite agar (BSA), selenite F and GN broth.

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7
Q

transport media of Enterobacteriaceae

A

Amies, Cary-Blair, and Stuart transport media.

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8
Q

colony morphology of Enterobacteriaceae

A

BAP and CAP – large, gray and smooth

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9
Q

Enterobacteriaceae fecal pathogens are generally _____

A

non-lactose fermenters.

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10
Q

_____ species produce colonies with black centers in media with H2S indicators such as HEA, BSA, and XLD agar.

A

Salmonella

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11
Q

The optimal temperature for the growth of enterobacteria is between _____ deg. Cent.

A

35-37

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12
Q

Serratia and Yersinia optimal temperature for growth

A

1-5 deg

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13
Q

E. coli optimal temperature for growth

A

45 -50 deg.cent.

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14
Q

Plated and tube media should be read within _____ to avoid false results.

A

18 to 24 hours of incubation

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15
Q

Enterobacteriaceae that are rapid lactose fermenters

A

Enterobacter, E.coli and Klebsiella

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16
Q

Enterobacteriaceae that are late lactose fermenters

A

Citrobacter freundii, Shigella sonnei, and Serratia

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17
Q

Enterobacteriaceae that are non-lactose fermenters

A

Citrobacter koseri, Edwardsiella, Morganella, Proteus, Providencia, Salmonella, Shigella, and Yersinia.

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18
Q

It is used to differentiate E. coli 0157:H7 ( sorbitol-negative) from other strains of E.coli (sorbitol-positive)

A

MacConkey-Sorbitol agar (MAC-SOR/SMAC)

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19
Q

MacConkey-Sorbitol agar (MAC-SOR/SMAC) pH indicator

A

Neutral red

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20
Q

MacConkey-Sorbitol agar (MAC-SOR/SMAC) result

A

E.coli O157:H7 exhibits clear or colorless colonies while the other strains remain with pink colonies.

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21
Q

Hektoen enteric agar (HEA) contains

A

bile salt, bromthymol blue dye, salicin, lactose, and sucrose.

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22
Q

____ inhibit the growth of other Gram-negative bacilli in the GIT and promote the isolation of _____

A

bile and dye; Salmonella and Shigella

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23
Q

Hektoen enteric agar (HEA) pH indicator

A

Bromthymol blue

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24
Q

Hektoen enteric agar (HEA) H2S indicator

A

Ferric ammonium citrate

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25
Q

lactose fermenters growth on HEA

A

colonies exhibit a yellow color ( black center colonies for C. freundii)

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26
Q

non-lactose fermenters growth on HEA

A

exhibit a blue-green color ( green with black center colonies for Proteus)

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27
Q

non-enteric pathogens growth on HEA

A

exhibit an orange to pinkish orange color.

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28
Q

Eosin methylene blue (EMB) or Levine’s medium contains

A

eosin Y, methylene blue, lactose and sucrose

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29
Q

Eosin methylene blue (EMB) or Levine’s medium pH indicator

A

Eosin and methylene blue

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30
Q

lactose fermenters results on Eosin methylene blue (EMB) or Levine’s medium

A

E. coli exhibit a greenish metallic sheen while those of other LF’s exhibit purple color.

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31
Q

non-lactose fermenters results on Eosin methylene blue (EMB) or Levine’s medium

A

colonies are colorless

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32
Q

other coliforms results on Eosin methylene blue (EMB) or Levine’s medium

A

exhibit a pink color

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33
Q

Differentiates Salmonella and Shigella species from other enteric bacteria.

A

Salmonella Shigella agar

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34
Q

SSA bile salts and brilliant green dye contents inhibit ____

A

Gram-positive bacteria and some lactose fermenters that are found in stool specimens.

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35
Q

Salmonella Shigella agar carbohydrate source

A

lactose

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36
Q

Salmonella Shigella agar pH indicator

A

Neutral red

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37
Q

Salmonella Shigella agar H2S indicator

A

sodium thiosulfate and ferric ammonium citrate

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38
Q

Salmonella Shigella agar results on salmonella

A

colonies are pink or colorless with black centers

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39
Q

Salmonella Shigella agar result on shigella

A

colonies are pink or colorless without black centers.

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40
Q

Serological test that identifies strains ( serovars or serotypes) of microorganisms that differ their antigenic composition.

A

Serotyping ( Slide agglutination test)

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41
Q

commonly tested organisms on Serotyping ( Slide agglutination test)

A

Salmonella, Shigella and E. coli O157:H7

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42
Q

preferred medium for testing in Serotyping ( Slide agglutination test)

A

BAP with 5% sheep’s blood.

43
Q

based on the heat stable somatic O antigen and heat labile flagellar H antigen for Salmonella while Shigella serotypying is based on the somatic O antigen.

A

Salmonella and Shigella serotyping

44
Q

Most of the salmonella isolates from humans belong to serogroups ___

A

A to G.

45
Q

Sorbitol-negative E.coli can be serotyped to identify whether the somatic O antigen O157 and the flagellar H antigen are present.

A

E. coli typing

46
Q

serotypes that are most frequently associated with infantile diarrhea.

A

E. coli O55, O111, and O127

47
Q

Serotyping ( Slide agglutination test) (+) result

A

agglutination

48
Q

It is used to determine whether a Gram-negative rod utilizes glucose and lactose or sucrose fermentatively or not.

It also identifies bacteria that can produce gas and H2S.

A

Fermentation of sugar – triple sugar iron agar (TSIA) test

49
Q

Two (2) necessary enzymes for an endobacterium to take up lactose in TSIA

A

β- galactoside permease
β – galactosidase

50
Q

facilitates the entry of the lactose molecule through the bacterial cell wall.

A

β- galactoside permease

51
Q

hydrolyzes lactose into glucose and galactose.

A

β – galactosidase

52
Q

Characteristics of TSIA:

A
  1. Uninoculated TSI (red color medium) is at pH 7.4
  2. The ratio of sugars in TSI is 10:10:1 ( lactose, sucrose, and glucose respectively)
  3. pH indicator: Phenol red
  4. H2S indicators: Ferrous sulphate and sodium thiosulfate
  5. TSIA reactions should not be read beyond 24 hours of incubation because the aerobic oxidation of the fermentation products from lactose and/or sucrose will revert the slant to an alkaline state.
53
Q

. Uninoculated TSI (red color medium) is at pH ___

A

7.4

54
Q

The ratio of sugars in TSI is _____

A

10:10:1 ( lactose, sucrose, and glucose respectively)

55
Q

TSIA pH indicator

A

Phenol red

56
Q

TSIA H2S indicator

A

H2S indicators: Ferrous sulphate and sodium thiosulfate

57
Q

TSIA reactions should not be read beyond _____ of incubation because the ______ of the fermentation products from ___ will revert the slant to an _____ state.

A

24 hours ; aerobic oxidation ; lactose and/or sucrose ; alkaline

58
Q

TSIA reaction: no fermentation of sugars result

A

Alkaline slant/ Alkaline butt (K/K)

59
Q

Organism with this reaction - TSIA reaction: no fermentation of sugars result (K/K)

A

are not members of the Enterobacteriacea.

60
Q

TSIA reaction: No lactose and sucrose fermentation (glucose fermenter) result

A

Alkaline slant/Acid butt (K/A) – red color slant

61
Q

in TSIA reaction: No lactose and sucrose fermentation (glucose fermenter), glucose concentration is ____

A

depleted

62
Q

TSIA reaction: Lactose, sucrose, and glucose fermentation result

A

Acid slant/Acid butt – yellow butt /slant

63
Q

Hydrogen sulfide (H2S) production, the H2S indicators are

A

Sodium thiosulfate and ferrous sulphate

64
Q

Hydrogen sulfide (H2S) production (+) result

A

Formation of black precipitate in the medium

65
Q

H2S production requires an _____ environment

A

acidic

66
Q

gas production (+) result of enterobacteriaceae

A

Formation of bubbles ( CO2 and H2), splitting of media in the butt, or complete displacement of the media from the bottom of the tube.

67
Q

TSIA interpretation

A
  1. Bacterial species that are incapable of fermenting glucose cannot utilize lactose.
    2.Lactose fermenters possess both β- galactosidase.
  2. Non-lactose fermenters (NLF) do not possess β- galactosidase permease.
  3. Late lactose fermenters (LLF) only possess β- galactosidase.
  4. Glucose and lactose fermenters are mostly opportunistic enterics.
  5. True enterics only ferment glucose.
68
Q

Bacterial species that are incapable of fermenting glucose cannot utilize _____.

A

lactose

69
Q

Lactose fermenters possess both ______.

A

β- galactosidase

70
Q

Non-lactose fermenters (NLF) do not possess ______.

A

β- galactosidase permease

71
Q

Late lactose fermenters (LLF) only possess ______.

A

β- galactosidase

72
Q

Glucose and lactose fermenters are mostly _____.

A

opportunistic enterics

73
Q

____ only ferment glucose.

A

True enterics

74
Q

in Sulfide indole motility (SIM) test, sulfide (+) results in

A

Black color formation in the butt

75
Q

in Sulfide indole motility (SIM) test, indole (+) results in

A

Pink to “wine-colored” ring formation after the addition of Kovac’s reagent.

76
Q

in Sulfide indole motility (SIM) test, motility (+) movement

A

Movement away from the stab line that produces a hazy appearance.

77
Q

_____ reagent should be added into the SIM medium after ______ of incubation.

A

Kovac’s ; 18 to 24 hours

78
Q

Used to determine the ability of an organism to utilize sodium citrate as its only carbon source and inorganic ammonium salts as its only nitrogen source.

A

Citrate utilization test

79
Q

Citrate utilization test (+) result indicator

A

Blue-colored citrate agar slant

80
Q

Citrate utilization test pH indicator

A

Bromthymol blue

81
Q

If citrate is used as the carbon source, the medium will turn ____

A

alkaline

82
Q

____ utilize citrate

A

Klebsiella and Enterobacter

83
Q

Escherichia and Edwardsiella reaction on Citrate utilization test

A

Escherichia and Edwardsiella have a negative reaction (green slant) in this test

84
Q

Used to determine whether a Gram-negative rod decarboxylates or deaminates lysine.

A

Lysine iron agar (LIA) test

85
Q

Lysine iron agar (LIA) test aids in the identification of ______ since they deaminate amino acids

A

Proteus, Morganella and Providencia

86
Q

LIA components

A

Lysine, peptones, and 0.1% glucose

87
Q

LIA H2S indicator

A

Ferric ammonium citrate and sodium thiosulfate

88
Q

LIA pH indicator

A

Bromcresol purple

89
Q

LIA interpretation

A

A. If the organism secretes lysine decarboxylase, cadaverine (purple) is formed.
B. If the decarboxylase is not produced, the butt remains acidic (yellow color)
C. If deamination of lysine occurs, it will form a burgundy (red) color on the slant.
D. If deamination does not occur, the LIA slant remains purple in color.
E. If glucose is fermented, the butt of the medium becomes acidic (yellow color)

90
Q

If the organism secretes lysine decarboxylase, _____ is formed.

A

cadaverine (purple)

91
Q

If the decarboxylase is not produced, the butt remains _____

A

acidic (yellow color)

92
Q

If deamination of lysine occurs, it will form a ______ on the slant.

A

burgundy (red) color

93
Q

If deamination does not occur, the LIA slant remains _____ in color.

A

purple

94
Q

If glucose is fermented, the butt of the medium becomes ______

A

acidic (yellow color)

95
Q

It measures the enzymatic ability of an organism to decarboxylate ( or hydrolyze) an amino acid to form an amine ( putrescine or cadaverine)

A

Decarboxylase test ( Moeller’s method)

96
Q

Moeller decarboxylase base media

A

Glucose, arginine, lysine, and ornithine

97
Q

Decarboxylase test ( Moeller’s method) pH indicator

A

Bromcresol purple or phenol red

98
Q

In decarboxylase test ( Moeller’s method), ____ promotes anaerobiosis

A

Mineral oil

99
Q

Decarboxylase test (Moeller’s method) incubation period

A

Four days

100
Q

Decarboxylase test (Moeller’s method) (+) result that produces alkaline product

A

purple or red color

101
Q

Decarboxylase test (Moeller’s method) (+) result associated with fermentation of glucose

A

exhibits a yellow color

102
Q

Enterobacter species on ornithine decarboxylase test

A

positive reaction

103
Q

Klebsiella species on ornithine decarboxylase test

A

negative reaction

mt (54 decks)

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