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MICROM 442 > Exam 3 Lecture 20 > Flashcards

Exam 3 Lecture 20 Flashcards

1
Q

Where can pathogenic E. coli come from?

A

Ingesting undercooked or contaminated meat; contaminated sprouts

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2
Q

True or false: pathogenic E. coli frequently causes disease in both cows and humans

A

False: not usually in cows

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3
Q

Which Enterobacteriacae spp are found as normal microbiota? (5)

A
  1. E. coli non-pathogenic species
  2. Klebsiella
  3. Enterobacter
  4. Proteus
  5. Serratia
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4
Q

Examples of E. coli non-pathogenic species + what do they produce

A

E. coli K12, E. coli B; produce vitamin K, which is important for production of RBC

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5
Q

What Enterobacteriacae spp are not part of normal human microbiota? (4)

A
  1. Salmonella
  2. Shigella
  3. Yersinia
  4. Pathogenic E. coli
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6
Q

What kinds of diseases can pathogenic Enterobacteriacae cause?

A

endotoxic shock, UTI, diarrhea, hemolytic uremic syndrome

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7
Q

Describe gram stain of E. coli

A

gram negative bacilli

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8
Q

E. coli can ferment ___ and are ___-positive

A

lactose; indole

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9
Q

True or false: E. coli is the most common Enterobacteriacae in normal colonic flora

A

true

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10
Q

What infections can pathogenic E. coli cause?

A

UTI, gastroenteritis, septicemia, neonatal meningitis

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11
Q

True or false: shigatoxin must be present to cause UTI and gastroenteritis

A

false; these can be caused by E. coli in our microbiota

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12
Q

E. coli is usually grown on ____ ___

A

MacConkey agar

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13
Q

MacConkey agar characteristics

A

phenol agar, sugars, lactose, salts

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14
Q

On a MacConkey agar, if able to produce ___-______, the bacteria will metabolize ____, causing the medium to turn ___ in color.

A

beta-galactosidase; lactose; pink

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15
Q

What are the 6 types of pathogenic E. coli?

A
  1. Enterotoxigenic E. coli (ETEC)
  2. Enteropathogenic E. coli (EPEC)
  3. Enteroinvasive E. coli (EIEC)
  4. Enterohemmorhagic E. coli (EHEC)
  5. Enteroaggregative E. coli (EAEC)
  6. Diffuse Aggregative E. coli (DAEC)
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16
Q

True or false: 6 types of pathogenic E. coli are easily distinguishable by appearance and biochemical tests

A

false - not easily distinguishable

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17
Q

Name some surface structures of E. coli

A

cell wall, K antigen capsule, pili (lots of dif types), H antigen flagella

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18
Q

BFP Pili

A

bundle forming pili found in EPEC strains

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19
Q

CFA Pili

A

colonization factor antigen; pili used by ETEC strains for binding to host cells

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20
Q

Type I pili

A

common pili binds via FimA to mannose residues on epithelial cells

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21
Q

What do O and H refer to in E. coli O157:H7?

A 
O = O antigen in LPS
H = flagellar antigen
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22
Q

True or false: all 6 pathogenic strains of E. coli have similar mechanisms of infection

A

false; they are different

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23
Q

EPEC mechanism of diarrheal disease

A

BFP pili used to form cluster of cells, injects effector proteins, causes pedestal formation

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24
Q

EHEC mechanism of diarrheal disease

A

causes pedestal formation and injects Stx-shiga toxin into the cells

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25
Q

ETEC mechanism of diarrheal disease

A

uses CFA pili to bind and then secretes two types of enterotoxins - ST (heat stable) and LT (heat labile)

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26
Q

EAEC mechanism of diarrheal disease

A

forms a biofilm on the surface of the cells, produces cytotoxins and enterotoxins to cause diarrhea

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27
Q

EIEC mechanism of diarrheal disease

A

binds and invades cells, then escapes into the cytoplasm similar to Shigella

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28
Q

DAEC mechanism of diarrheal disease

A

binds as single cells

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29
Q

Which E. coli is one of the major causes of UTIs?

A

UPEC (uropathogenic E. coli)

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30
Q

UPEC is responsible for ____% of the ____ cases of UTIs and ____ cases of pylonephritis (kidney infection)

A

70-90%; 7 million; 250,000

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31
Q

How does UPEC infection start?

A

spread of UPEC bacteria from the colon to the bladder

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32
Q

True or false: UPEC strains are often nosocomial acquired

A

false; more so community acquired (sexual transmission), but unclear what the mechanism of pickup is

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33
Q

The presence of _-___ in UPEC is associated with pyelonephritis

A

P-pili

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34
Q

Pyelonephritis

A

kidney infection caused by spreading of UTI from urethra/bladder to the kidneys

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35
Q

What is FimH?

A

protein at tip of P-pili which is responsible for the binding of the pilus to the host cell via mannose receptor

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36
Q

True or false: Pili and FimH mutants do not adhere well to bladder cells

A

True

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37
Q

What did researchers find in the UPEC low flow/high flow rate experiment?

A

The faster the flow rate, the more tightly FimH binds to mannose, suggesting that the bacteria have found a way to prevent from being excluded during fecal/urinary flow

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38
Q

Where is ETEC most prevelent?

A

developing world

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39
Q

ETEC is a major cause of ____ ___ and ____ ____

A

traveller’s diarrhea; infantile diarrhea

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40
Q

How does ETEC spread?

A

through contaminated food (fecal/oral route)

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41
Q

True or false: low inoculum of ETEC is sufficient to cause disease

A

false - requires high inoculum

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42
Q

ETEC attacks the ___ ___, which causes watery diarrhea

A

small bowel (part of small intestine)

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43
Q

True or false: ETEC does not cause histological or inflammatory changes of the GI tract

A

true

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44
Q

ETEC treatment

A

hydration

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45
Q

ETEC toxins are found on ……

A

plasmid

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46
Q

ETEC enterotoxins include:

A
  1. LT (heat labile toxin)
  2. ST (heat stable toxin)

** good mnemonic ** (LT = heat LABILE; ST = heat STABLE)

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47
Q

Features of ETEC LT1

A

similarity to cholera toxin, causes cAMP mediated osmotic disruption of the cell

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48
Q 
Which of these ETEC enterotoxins have a known mechanism of disease?
A. LT1
B. LT2
C. STa
D. STb
A

A and C

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49
Q

Where is EPEC most prevalent?

A

developing world

50
Q

EPEC attacks ___ ___

A

small bowel

51
Q

EPEC causes:

A

severe watery diarrhea, nausea, vomiting, dehydration

52
Q

EPEC treatment

A

hydration

53
Q

EPEC initially adheres to host cell via ___ ___. This forms an intimate attachment and allows ___ ____ and ____ _____.

A

BFP pili; actin condensation; microvillous effacement

54
Q

EPEC attaches to enterocytes, causing loss of_____.

A

microvilli

55
Q

What type of secretion system does EPEC use? What does EPEC secrete and why?

A

Type III SS; secretes effector proteins in order to rearrange host actin and form pedestal

56
Q

EPEC causes “_____ __ ____” lesions along with pedestal formation to allow close association to host cell

A

attaching and effacing lesions

57
Q

Once EPEC adheres to host cell, it injects ___, which is a needle complex that serves as a translocation tube.

A

EspA

58
Q

What protein does EPEC secrete via EspA?

A

Tir

59
Q

When Tir protein is injected into host cell, Tir is translocated into the ____ and then reappears on ____ of the host cell

A

cytoplasm; surface

60
Q

____ binds to Tir protein to form a tight complex between EPEC and host cell.

A

Intimin (EaeA)

61
Q

Mechanism of EPEC induced diarrhea (more specific in terms of cellular response)

A
  1. EPEC binds via BFP pili, causing loss of absorptive surfaces (malabsorption)
  2. alters Cl- or HCO3- ion secretion
  3. decreases the integrity of tight junctions
  4. neutrophil recruitment leads to more tissue damage
  5. more water flow out due to decreased resistance
62
Q

EHEC is the cause of ____ diarrhea

A

bloody

63
Q

EHEC can cause ____ ____ ____

A

hemolytic uremic syndrome (HUS)

64
Q

True or false: regarding EHEC, ~100 organisms is enough to cause infection

A

True

65
Q

EHEC is very resistant to ___

A

acid (thus can survive acidity of stomach)

66
Q

What are the two major virulence factors of EHEC?

A
  1. adhesins

2. Shiga Toxins

67
Q

EHEC adhesins are encoded on:

A

LEE plasmid (pathogenicity island)

68
Q

EHEC Shiga-like toxins can enter the _____ and cause microvascular damage in the ___ and ___

A

bloodstream; brain and kidney

69
Q

EHEC produces Shiga-like toxins are called:

A

Stx-1 and Stx-2

70
Q

True or false: Stx-1 and Stx-2 are encoded on a bacteriophage and undergo lysogenic/lytic phases

A

True

71
Q

What induces lysogenic to lytic transition of EHEC Shiga-like toxins?

A

Antibiotics or DNA damage

72
Q

True or false: EHEC causes attaching and effacing lesions and has Intimin

A

True

73
Q

True or false: Antibiotics and DNA damage can induce horizontal gene transfer (conjugation) in EHEC

A

True

74
Q

Shiga-like toxins block ___ ___, which leads to cell death of the ______ ____ in the kidney.

A

protein synthesis; microvascular system

75
Q

Stx-2 has a role in the development of ___

A

HUS

76
Q

Most common source of EHEC in the US:

A

cattle

77
Q

True or false: almost all cattle in feed lots are positive for EHEC-contamination of ground beef

A

True (99%!!)

78
Q

How do we diagnose EHEC?

A

detection of Shiga-like toxin and enrichment culture (this can be tough, but PCR is available)

79
Q

True or false: important treatment of EHEC is via antibiotics

A

False!! (super false omg)

-antibiotics induce lysogenic to lytic phase, causing more shiga-like toxin to be produced

80
Q

True or false: EAEC makes a biofilm on top of cells

A

true

81
Q

EAEC causes ___ diarrhea via attacking the ___ ___

A

watery; small bowel

82
Q

In immunocompromised patients, EAEC causes:

A

chronic persistent diarrhea

83
Q

What is unique about EIEC in how it interacts with the host cell and causes disease? (3)

A
  1. invades intestinal cell
  2. multiples within the cell
  3. spreads to adjacent cells
84
Q

Where is EIEC most common?

A

developing world

85
Q

EIEC attacks:

A

large bowel

86
Q

True or false: EIEC causes watery diarrhea that progresses to bloody diarrhea

A

True

87
Q

EIEC causes disease similar to ___, but it is usually ___

A

Shigella; milder

88
Q

True or false: some suggest that shigella and EIEC are the same organism, just different LPS

A

true

89
Q

___ and Shigella use the same set of genes for invasion

A

EIEC

90
Q

EIEC causes ____ ____ ____, then ___ and becomes intracellular

A

attaching + effacing lesions; invades

91
Q

When EIEC invades and it becomes intracellular, it is trapped inside a ____. In order for EIEC to spread to adjacent cell, EIEC must:

A

phagosome; EIEC must lyse vacuole to allow intracellular movement

92
Q

Shigella reservoir

A

human gastrointestinal tract

93
Q

Shigella causes ____ cases/year of diarrhea

A

more than 200 million

94
Q

Shigella is highly ____. Less than ___ organisms are sufficient to cause infectious disease.

A

contagious; 10

95
Q

What are the 4 serogroups of Shigella?

A

Group A: Shigella dysenteriae
Group B: Shigella flexneri
Group C: Shigella boydii
Group D: Shigella sonnei

96
Q

How do we diagnose Shigella?

A

detection of antigen

97
Q

True or false: Groups A, B, and C of Shigella cannot be distinguished physically.

A

False: biochemically

98
Q

Shigella and Salmonella are grown on:

A

Hektoen Enteric Agar

99
Q

Shigella appears ___ on agar, whereas Salmonella appears ___.

A

light; black

100
Q

Severity of Shigella disease depends on ____

A

serogroup

101
Q

Which Shigella spp cause more severe disease?

A

S. dysenteriae and S. flexnari

Groups A & B

102
Q

Which Shigella spp causes milder disease? What are the symptoms?

A

S. sonnei; watery diarrhea instead of dysentery (bloody diarrhea)

103
Q

True or false: Shigella can survive well in blood and macrophages

A

False - rare to find bacteria in the blood

104
Q

Shigella can be shed via stool for up to _ ___ after infection while you are asymptomatic

A

6 weeks

105
Q

What complication can follow Shigella infection?

A

Hemolytic Uremic Syndrome (HUS)

106
Q

Most Shigella cases occur in:

A

children (especially in institutions or day cares)

107
Q

Is there a vaccine available for Shigella?

A

No

108
Q

Shigella can tolerate:

A

acid

109
Q

Shigella invades ____ ___ and leads to ____ and ____

A

large bowel; ulceration and abscesses

110
Q

True or false: Shigella has a virulence plasmid

A

True

111
Q

Shigella virulence plasmid includes:

A

invasion loci and T3SS

112
Q

True or false: Shigella maintains its plasmid when grown in culture

A

False: somehow plasmid is lost when grown in culture

113
Q

All strains of Shigella produce ____

A

enterotoxins (minor contributors to disease except for S. dysenteriae which produces Shiga toxin)

114
Q

Shiga toxin is present in:

A

S. dysenteriae and on a phage

115
Q

Shiga toxin is similar to the Shiga-like toxin of ___

A

EHEC

116
Q

True or false: Shiga toxin is necessary for invasion

A

false

117
Q

Shiga toxin can cause disease from a ____

A

distance

118
Q

What kind of toxin is the Shiga toxin? (hint: what are its components)

A

bipartite (A-B toxin)

119
Q

Mechanism of Shiga toxin

A
  1. A-B toxin secreted by Shigella and binds to Gb3 glycolipid
  2. Shiga toxin is internalized and transported to the golgi
  3. A-subunit is released into the cytoplasm
  4. A-subunit binds to A-site of ribosome and blocks tRNA binding
120
Q

Regarding Shiga Toxin, inhibition of protein synthesis causes damage in:

A

kidney, brain, intestine

121
Q

Shiga toxin can infect kidney cells, which may cause damage in the ____ ____ of the kidneys. This can cause ___ to adhere to ____ deposits at the site of damage, which reduces kidney function.

A

filtration apparatus; platelets; fibrin

122
Q

True or false: Shigella can kill macrophages

A

True

MICROM 442 (26 decks)

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