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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
Q

Aeromonas species biochemical reactions

A

Indole +
Citrate +
H2S V
LDC +
Urease –
ODC –
Motility V
TSI agar K/A
Gas production V
Catalase +
Oxidase +

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26
Q

Aeromonas species gram stain

A

Gram-negative bacilli, single, in pairs, or short chains

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27
Q

Aeromonas species growth requirements

A

aerobic and facultative anaerobe, grow best at 35–37 °C

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28
Q

Aeromonas species colony morphology

A

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

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29
Q

Plesiomonas shigelloides biochemical reactions

A

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

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30
Q

Plesiomonas shigelloides gram stain

A

GNRs

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31
Q

Plesiomonas shigelloides growth requirements

A

aerobic and facultative anaerobe, grow best at 35–37 °C

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32
Q

Plesiomonas shigelloides colony morphology

A

clear and colorless on MacConkey, CIN, and XLD agars, clear and
green on Hektoen agar

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33
Q

DIRECT AND MOLECULAR TECHNIQUES FOR DETECTING CLOSTRIDIUM DIFFICILE- AND SHIGA TOXIN-
PRODUCING ORGANISMS

A

PCR and nucleic acid amplification testing molecular methods
Direct immunochromatographic C. diff testing

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34
Q

Due to their ability to cause life-threatening infections, the rapid detection of

A

C. difficile- and Shiga
toxin-producing E. coli organisms is pertinent for prompt patient care.

35
Q

Direct immunochromatographic C. difficile testing methods simultaneously target the

A

glutamate
dehydrogenase (GDH) antigen and toxins A and B produced by toxigenic strains

36
Q

Rapid tests for Shiga toxins 1 and 2 use

A

antibody-labeled assays to determine the presence or absence of
toxigenic strains of E. coli

37
Q

C. difficile evaluation

A

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
Q

Shiga toxin (ST1 and ST2): evaluation

A

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
Q

PCR and nucleic acid amplification testing molecular methods provide a definitive rule-out or
supportive diagnosis of

A

toxigenic infections

40
Q

Nucleic acid amplification testing targets genes specific
to toxigenic C. difficile strains including

A

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
Q

SEROTYPING E. COLI, SALMONELLA, AND SHIGELLA ORGANISMS

A

allows for the differentiation of species and subspecies of organisms that otherwise
have indistinguishable physical and biochemical properties

42
Q

Determining the serotype of enteric
pathogens allows for

A

further insight on disease manifestations and proper treatment methods

43
Q

Serotyping can be completed using the following test methodologies:

A

bacterial, latex, or
coagglutination, and fluorescent or enzyme-labeled immunoassay

44
Q

E. coli, Salmonella, and Shigella species and subspecies are differentiated from one another by

A

antigenic properties of their O, K, and H antigen

45
Q

Present in the outermost layer of the bacterial cell
wall, the

A

O antigen is a polymer of immunogenic repeating oligosaccharides.

46
Q

The K antigen is
present in

A

the capsular polysaccharides

47
Q

threadlike structure portion of the flagella in motile
organisms contains the

A

H antigen

48
Q

More than 2,000 Salmonella serotypes have been detected and
are determined by their

A

individual expression of the O and H antigens

49
Q

Shigella organisms are organized into four main species, or serogroups:

A

A (S. dysenteriae)
B (S. flexneri)
C (S. boydii)
D (S. sonnei)

50
Q

E. coli subspecies are differentiated based on the

A

composition and immunogenic
properties of the O, K, and H antigens

51
Q

E. coli O157:H7 is the extremely dangerous
subspecies that produces a

A

Shigella-like toxin that causes an enterohemorrhagic response

52
Q

MAJOR GASTROINTESTINAL PATHOGENS

A

Salmonella
Shigella
P. shigelloides
Aeromonas species
Y. enterocolitica
Campylobacter species
E. coli
Vibrio species

53
Q

Gastrointestinal infections occur from

A

humans ingesting bacteria present in raw, undercooked, or
unpasteurized products or human to human via the fecal–oral route

54
Q

Salmonella reservoir

A

Poultry

55
Q

Salmonella virulence factors

A

Lipopolysaccharide endotoxin: intracellular survival
O and H antigens: immunogenic, motility
Adhesion, colonization, and antiphagocytic properties
Type III secretion system for survival in macrophages

56
Q

Shigella reservoir

A

Human

57
Q

Shigella virulence factors

A

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
Q

P. shigelloides reservoir

A

soil
water
seafood

59
Q

Aeromonas species reservoir

A

Amphibians, reptiles,
fish; more prevalent
during warm-
weather months

60
Q

P. shigelloides virulence factors

A

Lophotrichous flagella: motility
Various toxins, proteases, hemolysins, lipases,
adhesins, and agglutinins

61
Q

Y. enterocolitica reservoir

A

Swine

62
Q

Y. enterocolitica virulence factors

A

Lipopolysaccharide endotoxin
Protein capsular antigen: protects against
phagocytosis
Proteins to promote adhesion and invasion

63
Q

Campylobacter species reservoir

A

poultry
cattle
sheep

64
Q

Campylobacter species virulence factors

A

Lipopolysaccharide endotoxin and exotoxins
Superoxide dismutase: harmful to cells’ DNA or
membrane factors
Siderophores: iron sequestering

65
Q

E. coli reservoir

A

cattle

66
Q

E. coli virulence factors

A

O, K, and H antigens: immunogenic, encapsulation,
motility
K1: inhibits phagocytosis, resists serum antibody
activity
O157:H7: hemorrhagic effects

67
Q

Vibrio species reservoir

A

water
oysters
seafood

68
Q

Vibrio species virulence factors

A

Adhesion factor, pili: colonization, mucosa adherence
Hemagglutination protease: intestinal inflammation
and degradation
Cholera toxin: quickly causes severe dehydration
Siderophores

69
Q

DETECTION METHODS FOR HELICOBACTER PYLORI

A

Serological tests
urea breath test
histological identification
culture
rapid urease test
PCR

70
Q

Serological tests using monoclonal IgG H. pylori antibodies or polyclonal H. pylori antibodies can

A

used to screen for a past or present infection

71
Q

Antigens produced by the presence of H. pylori can
be detected in

A

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
Q

The urea breath test is a

A

confirmatory method used for the detection of an active H. pylori
infection or to monitor the efficacy of treatment

73
Q

H. pylori rapidly metabolizes urea, and it is
excreted as

A

carbon molecules in the breath

74
Q

For this method, patients

A

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
Q

Breath samples are qualitatively analyzed for

A

the
presence or absence of the radioactive labeled carbon molecules

76
Q

Direct detection of H. pylori can be determined from

A

gastric or duodenal biopsy specimens via
microscopy, culture, or molecular methods

77
Q

Histological identification of the organism observed in Gram-stained smears or imprints of
biopsy samples yields the

A

presence of curved Gram-negative bacilli.

78
Q

Culture of these specimens is
required if

A

antibiotic susceptibility testing is needed for treatment options.

79
Q

rapid urease test

A

placing a biopsy specimen
in agar or on a reaction strip containing urea, a buffer, and a pH indicator.

80
Q

Urease from H. pylori will

A

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
Q

Results can be determined in

A

1-24 hours

82
Q

Polymerase chain reaction (PCR) testing is

A

highly specific and is more sensitive for H. pylori
detection than other methods.

83
Q
A

ASCP M Mometrix (18 decks)

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