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MMI 445 > Enterobacterales > Flashcards

Enterobacterales Flashcards

1
Q

What is the Gram stain of enterobacterales?

A

Gram-negative

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2
Q

What do enterobacterales refer to?

A

It is an order that contains 7 families

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3
Q

How do enterobacterales respond to an oxidase test?

A

It will be negative

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4
Q

What are the common characteristics of enterobacterales?

A

Inhabit human and animal GI tracts
Common in nature
Facultative anaerobes
Motility variable
Glucose fermenters
Oxidase-negative
Not fastidious

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5
Q

How do enterobacterales cultures look compared to Gram-positive cultures?

A

Enterobacterales colonies ted to be big while Gram-positive colonies are much smaller in comparison

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6
Q

What is the typical Gram stain morphology of enterobacterales?

A

Medium-sized Gram-negative bacteria with rounded ends
Some are short rods that resemble Gram-negative coccobacilli
Often stains better on the ends = bipolar staining

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7
Q

What are the relevant opportunistic enterobacterales pathogens?

A

Salmonella spp (non-Typhi)
E. coli

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8
Q

What are the relevant overt enterobacterales pathogens?

A

Salmonella Typhi
Shigella spp
E. coli

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9
Q

What are some infections caused by enterobacterales?

A

Neonatal meningitis
Bacteraemia
Liver abscesses
Abdominal wounds
Lower respiratory tract
Diarrhea
Urinary tract

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10
Q

How does E. coli colonize humans?

A

It colonizes infants at birth and exists in a mutually beneficial relationship with the host and remains confined to the intestinal lumen

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11
Q

How does E. coli cause disease?

A

It causes disease in immunocompromised patients or can be introduced via surgery/trauma

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12
Q

How is E. coli transmitted?

A

Endogenous, fecal-oral, person-to-person, contaminated food/water

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13
Q

What is enterotoxigenic E. coli?

A

Traveler’s diarrhea = watery stools
Virulence factors = heat labile and heat stable toxins

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14
Q

What is enteroinvasive E. coli?

A

It invades enterocytes; similar to Shigella
Causes dysentery in young children

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15
Q

What is enteropathogenic E. coli?

A

Causes diarrhea in infants and chronic diarrhea

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16
Q

What is enterohemorrhagic E. coli?

A

Produces Shiga toxin which targets endothelial cells in the GI tract and kidneys
Causes hemorrhagic colitis
Causes hemolytic-uremic syndrome

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17
Q

What is uropathogenic E. coli?

A

Causes extraintestinal infections (UTIs)
Community-acquired

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18
Q

What does enteroaggregative E. coli cause?

A

Watery diarrhea

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19
Q

What does Salmonella do?

A

Causes infections in humans and cold-blooded animals

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20
Q

What does non-typhoidal Salmonella cause?

A

Gastroenteritis = diarrhea, fever, cramps with a wide variety of serotypes

Bacteremia, extraintestinal infections = spread from GI tract, immunocompromised

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21
Q

What does typhoidal Salmonella cause?

A

Typhoid fever = prolonged fever, multisystem involvement
fecal-oral infection

22
Q

Which species of Salmonella causes infection in warm-blooded animals?

A

S. enterica

23
Q

When we refer to Typhi what do we mean?

A

It is a Salmonella serotype, not a genus

24
Q

What is the onset and symptoms of Salmonella infections?

A

Symptoms occur within 6-72 hours of exposure
Symptoms = fever, chills, diarrhea, abdominal cramps, headache, nausea, vomiting

25
Q

Who is most at risk for Salmonella infections?

A

Children younger than 5
Older adults
Pregnant women
Those who are immunocompromised

26
Q

How is Shigella transmitted?

A

Transmitted person-to-person and ingestion of contaminated food/water
Shigellosis is most common in situations where hygiene is compromised

27
Q

How is Shigellosis characterized?

A

By bloody diarrhea and non-bloody diarrhea

28
Q

How is Shigella different from E. coli and Salmonella?

A

It is not motile so it cannot easily access the bloodstream

29
Q

PulseNet Canada plays a vital role in what?

A

Active surveillance and investigation of foodborne outbreaks

30
Q

How do we serotype E. coli?

A

By its O antigen (186 types) and its H antigen (56 types)

31
Q

What is the most common Shiga toxin producer?

A

O157:H7

32
Q

How do we serotype Shigella?

A

4 subgroups (A-D) and many serotypes

33
Q

How do we serotype Salmonella?

A

Based on characterization of O, H, and Vi antigens

34
Q

How do we test for lactose fermentation?

A

Use MacConkey agar
If the plate turns red, that means that the bacteria produced acid
Bile salts and crystal violet inhibit most Gram-positives

35
Q

What are 4 lactose fermenters?

A

Citrobacter
E. coli
Enterobacter
Klebsiella

36
Q

What are non-lactose fermenters within Enterbacterales?

A

Salmonella
Shigella

37
Q

What is indole used for?

A

To determine if the organism can convert tryptophan to indole
It turns pink if indole is present

38
Q

What is a relevant enterobacterales that produces H2S

A

Salmonella

39
Q

What are the biochemical characteristics of E. coli?

A

Colony characteristics: LF, some beta-hemolysis
Indole = +
H2S = -
Motility = +

40
Q

What are the biochemical characteristics of Salmonella?

A

NLF, black on HE agar
Indole = -
H2S = +
Motility = +

41
Q

What are the biochemical characteristics of Shigella?

A

NLF, colorless on HE agar
Indole = variable
H2S = -
Motility = -

42
Q

What are some primary stool culture media?

A

Blood agar
MacConkey agar
MacConkey-Sorbitol agar
Hektoen agar
CIN agar
Campy-CVA or Campy CBF
TCBS

43
Q

What is the purpose of a blood agar media in stool tests?

A

Rules out Aeromonas and Plesiomonas
Sweep oxidase test and sub-culture
This is a non-selective test

44
Q

What is the purpose of MacConkey agar in stool tests?

A

Contains bile salts and crystal violet which inhibits Gram + bacteria
Tests for lactose fermentation
Selective and differential medium

45
Q

What is the purpose of MacSorb agar in stool tests?

A

Used to enhance isolation and differentiate E. coli O157:H7 from other E. coli because this serotype does not ferment sorbitol while others do

46
Q

What is the purpose of Chromogenic agar in stool tests?

A

Detects Shiga toxin-producing E. coli of all serotypes

47
Q

What is the purpose of Hektoen agar in stool tests?

A

Selects for stool pathogens by inhibiting normal flora of the gI tract

48
Q

What is the purpose of CIN agar in stool tests?

A

Used to isolate Yersinia spp

49
Q

What is the purpose of Campy-CVA agar in stool tests?

A

Isolation of Campylobacter spp

50
Q

What is the purpose of TCBS agar in stool tests?

A

Selective and differential for Vibrio species

51
Q

What are the advantages of molecular testing for GI pathogens?

A

Fast, tests a broad range of organisms

52
Q

What are the disadvantages of molecular testing for GI pathogens?

A

Sensitivity, limited to the panel targets, can be expensive

MMI 445 (9 decks)

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