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ASCP M Mometrix > GI tract > Flashcards

GI tract Flashcards

1
Q

Salmonella species biochemical reactions

A

Indole −
Citrate +
H2S +
LDC + ∗
LDA −
Urease −
Ornithine decarboxylase (ODC) +
Motility +
TSI agar K/A
Gas production Variable

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2
Q

Salmonella species gram stain

A

GNRs

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3
Q

Salmonella species growth requirements

A

mainly aerobic but facultative anaerobe as well, 37 °C with growth
in 16–24 hours of inoculation

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4
Q

Salmonella species colony morphology

A

opaque or translucent, smooth, 2–4 mm in diameter on supportive
media, green or transparent with black center on Hektoen enteric agar, transparent or red
with black centers on xylose-lysine-deoxycholate agar

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5
Q

Shigella species biochemical reactions

A

Indole Variable
Citrate −
H2S − ∗
LDC −
LDA − ∗
Urease −
ODC Variable
Motility − ∗
TSI agar K/A
Gas production −

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6
Q

Shigella species gram stain

A

GNRs

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7
Q

Shigella species growth requirements

A

aerobic and facultative anaerobe, 35 °C with growth 18–24 hours
after inoculation

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8
Q

Shigella species colony morphology

A

clear or slightly pink on MacConkey agar, green or transparent on
Hektoen agar, transparent or red on xylose-lysine-deoxycholate agar

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9
Q

Toxigenic Escherichia coli biochemical reactions

A

Indole +
Citrate –
H2S –
LDC +
LDA –
Urease –
ODC +
Motility +
TSI agar A/A
Gas production +

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10
Q

Toxigenic E. coli gram stain

A

GNRs

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11
Q

Toxigenic E. coli growth requirements

A

aerobic and facultative anaerobe, grow best at 37 °C

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12
Q

Toxigenic E. coli colony morphology

A

circular, convex colonies, gray, translucent to opaque on sheep blood
agar, pink, opaque on MacConkey, green with a metallic sheen, opaque on eosin methylene
blue agar

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13
Q

Campylobacter species biochemical reactions

A

Catalase +
Oxidase +
Hippurate +

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14
Q

Campylobacter species gram stain

A

Gram-negative bacilli, small curved rods, “seagull appearance”

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15
Q

Campylobacter species growth requirements

A

Microaerophilic, Campylobacter-selective agar at 42 °C

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16
Q

Campylobacter species colony morphology

A

mucoid, flat, grayish colonies with irregular edges, potentially
swarming.

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17
Q

Vibrio species biochemical reactions

A

Catalase +
Oxidase +

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18
Q

Vibrio species gram stain

A

Gram-negative bacilli, curved rod with polar flagella

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19
Q

Vibrio species growth requirements

A

aerobic and facultative anaerobe, require media with increased salt
concentration, sodium chloride, and acidic pH, 35–37 °C for 6–8 hours for APW or 35–37 °C
18–24 hours to TCBS and all other media

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20
Q

Vibrio species colony morphology

A

creamy white, smooth and convex; yellow-green on TCBS, colorless
on MacConkey agar

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21
Q

Yersinia enterocolitica biochemical reactions

A

Indole V
Citrate –
H2S –
LDC –
LDA –
Urease V
ODC +
Motility V*
TSI agar K/A
Gas production –
Catalase +
Oxidase –
*Motile at 22–25 °C; nonmotile at 37 °C (body temperature)

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22
Q

Yersinia enterocolitica gram stain

A

GNRs

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23
Q

Yersinia enterocolitica growth requirements

A

aerobic and facultative anaerobe, grow optimally at room
temperature (22–25 °C)

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24
Q

Yersinia enterocolitica colony morphology

A

translucent or opaque or gray-white, slightly mucoid (after 24 hours
of growth) on sheep blood agar, flat, colorless or pale pink on MacConkey agar, “bulls-eye”
appearance with deep-red center and translucent outer zone on cefsulodin irgasan
novobiocin (CIN) agar

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25
Aeromonas species biochemical reactions
Indole + Citrate + H2S V LDC + Urease – ODC – Motility V TSI agar K/A Gas production V Catalase + Oxidase +
26
Aeromonas species gram stain
Gram-negative bacilli, single, in pairs, or short chains
27
Aeromonas species growth requirements
aerobic and facultative anaerobe, grow best at 35–37 °C
28
Aeromonas species colony morphology
circular, gray on sheep blood agar, dark green on sheep blood agar after 72 hours due to beta-hemolysis, deep-red center surrounded by translucent outer zone of colony on CIN agar
29
Plesiomonas shigelloides biochemical reactions
Indole + Citrate H2S LDC + LDA Urease ODC – Motility TSI agar K/A Gas production – Catalase + Oxidase +
30
Plesiomonas shigelloides gram stain
GNRs
31
Plesiomonas shigelloides growth requirements
aerobic and facultative anaerobe, grow best at 35–37 °C
32
Plesiomonas shigelloides colony morphology
clear and colorless on MacConkey, CIN, and XLD agars, clear and green on Hektoen agar
33
DIRECT AND MOLECULAR TECHNIQUES FOR DETECTING CLOSTRIDIUM DIFFICILE- AND SHIGA TOXIN- PRODUCING ORGANISMS
PCR and nucleic acid amplification testing molecular methods Direct immunochromatographic C. diff testing
34
Due to their ability to cause life-threatening infections, the rapid detection of
C. difficile- and Shiga toxin-producing E. coli organisms is pertinent for prompt patient care.
35
Direct immunochromatographic C. difficile testing methods simultaneously target the
glutamate dehydrogenase (GDH) antigen and toxins A and B produced by toxigenic strains
36
Rapid tests for Shiga toxins 1 and 2 use
antibody-labeled assays to determine the presence or absence of toxigenic strains of E. coli
37
C. difficile evaluation
o GDH antigen and toxin absent: no C. difficile infection o Both GDH antigen and toxin present: ❖ Symptomatic: consistent with active infection ❖ Asymptomatic: consistent with C. difficile colonization o Either GDH antigen or toxin present: inconclusive; molecular testing recommended
38
Shiga toxin (ST1 and ST2): evaluation
o ST1 and ST2 absent: no Shiga toxin-producing E. coli present o Either ST1 or ST2 or both present: Shiga toxin-producing E. coli present.
39
PCR and nucleic acid amplification testing molecular methods provide a definitive rule-out or supportive diagnosis of
toxigenic infections
40
Nucleic acid amplification testing targets genes specific to toxigenic C. difficile strains including
A and B and 16S ribosomal RNA. Genes for ST1, ST2, E. coli O157:H7, and Shigella dysenteriae type 1 are targeted for detection of Shiga toxin-producing organisms.
41
SEROTYPING E. COLI, SALMONELLA, AND SHIGELLA ORGANISMS
allows for the differentiation of species and subspecies of organisms that otherwise have indistinguishable physical and biochemical properties
42
Determining the serotype of enteric pathogens allows for
further insight on disease manifestations and proper treatment methods
43
Serotyping can be completed using the following test methodologies:
bacterial, latex, or coagglutination, and fluorescent or enzyme-labeled immunoassay
44
E. coli, Salmonella, and Shigella species and subspecies are differentiated from one another by
antigenic properties of their O, K, and H antigen
45
Present in the outermost layer of the bacterial cell wall, the
O antigen is a polymer of immunogenic repeating oligosaccharides.
46
The K antigen is present in
the capsular polysaccharides
47
threadlike structure portion of the flagella in motile organisms contains the
H antigen
48
More than 2,000 Salmonella serotypes have been detected and are determined by their
individual expression of the O and H antigens
49
Shigella organisms are organized into four main species, or serogroups:
A (S. dysenteriae) B (S. flexneri) C (S. boydii) D (S. sonnei)
50
E. coli subspecies are differentiated based on the
composition and immunogenic properties of the O, K, and H antigens
51
E. coli O157:H7 is the extremely dangerous subspecies that produces a
Shigella-like toxin that causes an enterohemorrhagic response
52
MAJOR GASTROINTESTINAL PATHOGENS
Salmonella Shigella P. shigelloides Aeromonas species Y. enterocolitica Campylobacter species E. coli Vibrio species
53
Gastrointestinal infections occur from
humans ingesting bacteria present in raw, undercooked, or unpasteurized products or human to human via the fecal–oral route
54
Salmonella reservoir
Poultry
55
Salmonella virulence factors
Lipopolysaccharide endotoxin: intracellular survival O and H antigens: immunogenic, motility Adhesion, colonization, and antiphagocytic properties Type III secretion system for survival in macrophages
56
Shigella reservoir
Human
57
Shigella virulence factors
Endotoxins: invasion, multiplication, and antiphagocytic properties Adhesion factor: colonization O antigen, Shiga toxin: immunogenic, inhibits cell protein synthesis causing life-threatening disease Type III secretion system: invading macrophage
58
P. shigelloides reservoir
soil water seafood
59
Aeromonas species reservoir
Amphibians, reptiles, fish; more prevalent during warm- weather months
60
P. shigelloides virulence factors
Lophotrichous flagella: motility Various toxins, proteases, hemolysins, lipases, adhesins, and agglutinins
61
Y. enterocolitica reservoir
Swine
62
Y. enterocolitica virulence factors
Lipopolysaccharide endotoxin Protein capsular antigen: protects against phagocytosis Proteins to promote adhesion and invasion
63
Campylobacter species reservoir
poultry cattle sheep
64
Campylobacter species virulence factors
Lipopolysaccharide endotoxin and exotoxins Superoxide dismutase: harmful to cells’ DNA or membrane factors Siderophores: iron sequestering
65
E. coli reservoir
cattle
66
E. coli virulence factors
O, K, and H antigens: immunogenic, encapsulation, motility K1: inhibits phagocytosis, resists serum antibody activity O157:H7: hemorrhagic effects
67
Vibrio species reservoir
water oysters seafood
68
Vibrio species virulence factors
Adhesion factor, pili: colonization, mucosa adherence Hemagglutination protease: intestinal inflammation and degradation Cholera toxin: quickly causes severe dehydration Siderophores
69
DETECTION METHODS FOR HELICOBACTER PYLORI
Serological tests urea breath test histological identification culture rapid urease test PCR
70
Serological tests using monoclonal IgG H. pylori antibodies or polyclonal H. pylori antibodies can
used to screen for a past or present infection
71
Antigens produced by the presence of H. pylori can be detected in
serum or stool samples by binding to antibodies embedded in a test cartridge and migrating to a test window where they produce a colored line
72
The urea breath test is a
confirmatory method used for the detection of an active H. pylori infection or to monitor the efficacy of treatment
73
H. pylori rapidly metabolizes urea, and it is excreted as
carbon molecules in the breath
74
For this method, patients
ingest urea capsules that contain radioactively labeled carbon molecules and then they exhale into a collection container 10– 15 minutes after swallowing the capsule
75
Breath samples are qualitatively analyzed for
the presence or absence of the radioactive labeled carbon molecules
76
Direct detection of H. pylori can be determined from
gastric or duodenal biopsy specimens via microscopy, culture, or molecular methods
77
Histological identification of the organism observed in Gram-stained smears or imprints of biopsy samples yields the
presence of curved Gram-negative bacilli.
78
Culture of these specimens is required if
antibiotic susceptibility testing is needed for treatment options.
79
rapid urease test
placing a biopsy specimen in agar or on a reaction strip containing urea, a buffer, and a pH indicator.
80
Urease from H. pylori will
metabolize the urea to ammonia and bicarbonate, increasing the pH in the test system, and change the color of the pH indicator to reflect the alkaline environment.
81
Results can be determined in
1-24 hours
82
Polymerase chain reaction (PCR) testing is
highly specific and is more sensitive for H. pylori detection than other methods.
83

ASCP M Mometrix (18 decks)

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