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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
lactose fermenters growth on HEA
colonies exhibit a yellow color ( black center colonies for C. freundii)
26
non-lactose fermenters growth on HEA
exhibit a blue-green color ( green with black center colonies for Proteus)
27
non-enteric pathogens growth on HEA
exhibit an orange to pinkish orange color.
28
Eosin methylene blue (EMB) or Levine’s medium contains
eosin Y, methylene blue, lactose and sucrose
29
Eosin methylene blue (EMB) or Levine’s medium pH indicator
Eosin and methylene blue
30
lactose fermenters results on Eosin methylene blue (EMB) or Levine’s medium
E. coli exhibit a greenish metallic sheen while those of other LF’s exhibit purple color.
31
non-lactose fermenters results on Eosin methylene blue (EMB) or Levine’s medium
colonies are colorless
32
other coliforms results on Eosin methylene blue (EMB) or Levine’s medium
exhibit a pink color
33
Differentiates Salmonella and Shigella species from other enteric bacteria.
Salmonella Shigella agar
34
SSA bile salts and brilliant green dye contents inhibit ____
Gram-positive bacteria and some lactose fermenters that are found in stool specimens.
35
Salmonella Shigella agar carbohydrate source
lactose
36
Salmonella Shigella agar pH indicator
Neutral red
37
Salmonella Shigella agar H2S indicator
sodium thiosulfate and ferric ammonium citrate
38
Salmonella Shigella agar results on salmonella
colonies are pink or colorless with black centers
39
Salmonella Shigella agar result on shigella
colonies are pink or colorless without black centers.
40
Serological test that identifies strains ( serovars or serotypes) of microorganisms that differ their antigenic composition.
Serotyping ( Slide agglutination test)
41
commonly tested organisms on Serotyping ( Slide agglutination test)
Salmonella, Shigella and E. coli O157:H7
42
preferred medium for testing in Serotyping ( Slide agglutination test)
BAP with 5% sheep’s blood.
43
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.
Salmonella and Shigella serotyping
44
Most of the salmonella isolates from humans belong to serogroups ___
A to G.
45
Sorbitol-negative E.coli can be serotyped to identify whether the somatic O antigen O157 and the flagellar H antigen are present.
E. coli typing
46
serotypes that are most frequently associated with infantile diarrhea.
E. coli O55, O111, and O127
47
Serotyping ( Slide agglutination test) (+) result
agglutination
48
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.
Fermentation of sugar – triple sugar iron agar (TSIA) test
49
Two (2) necessary enzymes for an endobacterium to take up lactose in TSIA
β- galactoside permease β – galactosidase
50
facilitates the entry of the lactose molecule through the bacterial cell wall.
β- galactoside permease
51
hydrolyzes lactose into glucose and galactose.
β – galactosidase
52
Characteristics of TSIA:
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
. Uninoculated TSI (red color medium) is at pH ___
7.4
54
The ratio of sugars in TSI is _____
10:10:1 ( lactose, sucrose, and glucose respectively)
55
TSIA pH indicator
Phenol red
56
TSIA H2S indicator
H2S indicators: Ferrous sulphate and sodium thiosulfate
57
TSIA reactions should not be read beyond _____ of incubation because the ______ of the fermentation products from ___ will revert the slant to an _____ state.
24 hours ; aerobic oxidation ; lactose and/or sucrose ; alkaline
58
TSIA reaction: no fermentation of sugars result
Alkaline slant/ Alkaline butt (K/K)
59
Organism with this reaction - TSIA reaction: no fermentation of sugars result (K/K)
are not members of the Enterobacteriacea.
60
TSIA reaction: No lactose and sucrose fermentation (glucose fermenter) result
Alkaline slant/Acid butt (K/A) – red color slant
61
in TSIA reaction: No lactose and sucrose fermentation (glucose fermenter), glucose concentration is ____
depleted
62
TSIA reaction: Lactose, sucrose, and glucose fermentation result
Acid slant/Acid butt – yellow butt /slant
63
Hydrogen sulfide (H2S) production, the H2S indicators are
Sodium thiosulfate and ferrous sulphate
64
Hydrogen sulfide (H2S) production (+) result
Formation of black precipitate in the medium
65
H2S production requires an _____ environment
acidic
66
gas production (+) result of enterobacteriaceae
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
TSIA interpretation
1. Bacterial species that are incapable of fermenting glucose cannot utilize lactose. 2.Lactose fermenters possess both β- galactosidase. 3. Non-lactose fermenters (NLF) do not possess β- galactosidase permease. 4. Late lactose fermenters (LLF) only possess β- galactosidase. 5. Glucose and lactose fermenters are mostly opportunistic enterics. 6. True enterics only ferment glucose.
68
Bacterial species that are incapable of fermenting glucose cannot utilize _____.
lactose
69
Lactose fermenters possess both ______.
β- galactosidase
70
Non-lactose fermenters (NLF) do not possess ______.
β- galactosidase permease
71
Late lactose fermenters (LLF) only possess ______.
β- galactosidase
72
Glucose and lactose fermenters are mostly _____.
opportunistic enterics
73
____ only ferment glucose.
True enterics
74
in Sulfide indole motility (SIM) test, sulfide (+) results in
Black color formation in the butt
75
in Sulfide indole motility (SIM) test, indole (+) results in
Pink to “wine-colored” ring formation after the addition of Kovac’s reagent.
76
in Sulfide indole motility (SIM) test, motility (+) movement
Movement away from the stab line that produces a hazy appearance.
77
_____ reagent should be added into the SIM medium after ______ of incubation.
Kovac’s ; 18 to 24 hours
78
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.
Citrate utilization test
79
Citrate utilization test (+) result indicator
Blue-colored citrate agar slant
80
Citrate utilization test pH indicator
Bromthymol blue
81
If citrate is used as the carbon source, the medium will turn ____
alkaline
82
____ utilize citrate
Klebsiella and Enterobacter
83
Escherichia and Edwardsiella reaction on Citrate utilization test
Escherichia and Edwardsiella have a negative reaction (green slant) in this test
84
Used to determine whether a Gram-negative rod decarboxylates or deaminates lysine.
Lysine iron agar (LIA) test
85
Lysine iron agar (LIA) test aids in the identification of ______ since they deaminate amino acids
Proteus, Morganella and Providencia
86
LIA components
Lysine, peptones, and 0.1% glucose
87
LIA H2S indicator
Ferric ammonium citrate and sodium thiosulfate
88
LIA pH indicator
Bromcresol purple
89
LIA interpretation
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
If the organism secretes lysine decarboxylase, _____ is formed.
cadaverine (purple)
91
If the decarboxylase is not produced, the butt remains _____
acidic (yellow color)
92
If deamination of lysine occurs, it will form a ______ on the slant.
burgundy (red) color
93
If deamination does not occur, the LIA slant remains _____ in color.
purple
94
If glucose is fermented, the butt of the medium becomes ______
acidic (yellow color)
95
It measures the enzymatic ability of an organism to decarboxylate ( or hydrolyze) an amino acid to form an amine ( putrescine or cadaverine)
Decarboxylase test ( Moeller’s method)
96
Moeller decarboxylase base media
Glucose, arginine, lysine, and ornithine
97
Decarboxylase test ( Moeller’s method) pH indicator
Bromcresol purple or phenol red
98
In decarboxylase test ( Moeller’s method), ____ promotes anaerobiosis
Mineral oil
99
Decarboxylase test (Moeller’s method) incubation period
Four days
100
Decarboxylase test (Moeller’s method) (+) result that produces alkaline product
purple or red color
101
Decarboxylase test (Moeller’s method) (+) result associated with fermentation of glucose
exhibits a yellow color
102
Enterobacter species on ornithine decarboxylase test
positive reaction
103
Klebsiella species on ornithine decarboxylase test
negative reaction

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