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Unit 16 - GI Tract Infections Flashcards

1
Q

What can diarrhea be caused by?

A 
E. coli
Salmonella
Campylobacter
Vibrio
Shigella
Listeria
Rotavirus
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2
Q

What is the difference between true food poisoning and food-associated infections?

A

True food poisoning:

  • Fast rxn
  • Ingestion of pre-formed toxin
  • Toxins survive cooking/heating

Food-associated infections:

  • Slow rxn
  • Food acts as a vehicle for the pathogen
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3
Q

Give two examples of food associated infection causes

A

campylobacter

salmonella

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4
Q

What are the 3 ways that GI infections can cause disease?

A

1) Fluid balance
- Change balance of water and electrolytes in small bowel - massive fluid secretion
2) Cell destruction & inflammation
- Invasion and/or cytotoxin production
3) Invasion
- Penetrate intestinal mucosa - spread and multiply outside the bowel

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5
Q

List some points about diarrhea

A
  • Increase in fluid and electrolyte loss in gut lumen (causes unformed or liquid feces)
  • Allows host to get rid of the pathogen
  • Allows pathogen to disseminate
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6
Q

How does diarrhea affect people in resource-poor regions vs people in resource-rich regions?

A

Resource-poor regions:
-Major cause of mortality in children

Resource-rich regions:
-Usually mild and self-limiting, except very young, elderly and immunocompromised

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7
Q

Diarrhea:

Is the identity of the pathogen usually determined?

A

No

  • Generally identity of the pathogen not determined
  • Difficult to distinguish based on symptoms
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8
Q

Diarrhea:

What is very important to ask about when a patient has diarrhea?

A
  • Food intake

- Travel

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9
Q

Diarrhea:

Macroscopic and microscopic examination of feces for ___ and ___

A

blood and pus

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10
Q

Diarrhea:

Precise diagnosis important in ______

A

outbreaks

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11
Q

List the 6 different groups of E. coli with different pathogenic mechanism

A 
EPEC - Enteropathogenic E. coli
ETEC - Enterotoxigenic E. coli
EHEC - Entertohaemorrhagic E. coli
EIEC - Enteroinvasive E. coli
EAEC - Enteroaggregative E. coli
DAEC - Diffuse - aggregative E. coli
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12
Q

Enteropathogenic E. coli (EPEC):

Affects who?

A

babies and young children

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13
Q

Enteropathogenic E. coli (EPEC):

What virulence factors does it have?

A

adhesions, bundle-forming pili and intimin

-allows for attachment to epithelial cells and microfilms

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14
Q

Enterotoxigenic E. coli (ETEC):

Affects who?

A

Children

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15
Q

Enterotoxigenic E. coli (ETEC):

Where does it bind to?

A

Binds to receptors on cell membrane of small intestine

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16
Q

Enterotoxigenic E. coli (ETEC): List the 2 plasmid-encoded toxins

A

1) Heat labile (LT) toxin

2) Heat stabile (ST) toxin

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17
Q

Enterotoxigenic E. coli (ETEC):

Describe the Heat labile (LT) toxin

A

similar mode of action as cholera toxin

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18
Q

Enterotoxigenic E. coli (ETEC):

Describe the Heat stable (ST) toxin

A
  • increases guanylate cyclase activity
  • increases cGMP
  • increases fluid secretion
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19
Q

Enterohaemorrhagic E. coli (EHEC):

List the 2 key points about this type of E. coli

A

Invasive

Makes Toxin

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20
Q

Enterohaemorrhagic E. coli (EHEC):

Describe the two toxins

A

Verotoxin 1 and 2 (VTEC)
AKA Shiga Like Toxin

SLT-1 and SLT-2

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21
Q

Enterohaemorrhagic E. coli (EHEC):

What do the two toxins do and cause?

A
  • Toxins damage large intestine
  • Inhibit protein synthesis
  • Cause ulceration and bleeding
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22
Q

Enterohaemorrhagic E. coli (EHEC):

Important serotype

A

Serotype O157:H7

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23
Q

Enterohaemorrhagic E. coli (EHEC):

What 2 things can EHEC cause?

A

HC - Hemorrhagic colitis

HUS - Hemolytic ureic syndrome

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24
Q

Enterohaemorrhagic E. coli (EHEC):

What is HC (hemorrhagic colitis)?

A

destruction of mucosa leads to hemorrhage and causes bloody diarrhea

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25
Q

Enterohaemorrhagic E. coli (EHEC):

What is HUS (hemolytic ureic syndrome)?

A
  • toxin gets into bloodstream
  • verotoxin receptors found on renal epithelium - may account for kidney damage

**KEY POINT THAT EHEC CAN CAUSE KIDNEY DAMAGE

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26
Q

Enterohaemorrhagic E. coli (EHEC):

Symptoms?

A
  • Anemia (fatigue, weakness, light-headedness) due to destruction of RBC
  • Low platelet count and sudden kidney damage

**AGAIN KEY POINT THAT A SYMPTOM OF EHEC IS KIDNEY DAMAGE

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27
Q

Enteroinvasive E. coli (EIEC):

Describe it’s mechanism of action

A
  • attaches to mucosa of large intestine
  • invade cells by endocytosis
  • multiply
  • spread to adjacent cells
  • tissue destruction
  • inflammation and ulceration
  • ulceration can result in blood and mucus in stool
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28
Q

Enteroaggregative E. coli (EAEC):

Has a _____ ____ appearance on tissue culture cells

A

stacked brick

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29
Q

Enteroaggregative E. coli (EAEC):

How does it aggregate?

A

plasmid-encoded fimbria

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30
Q

Enteroaggregative E. coli (EAEC):

Toxins produced but role in diarrheal disease _____

A

uncertain

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31
Q

Diffuse-aggregative E. coli (DAEC):

list one thing bout it

A

alpha-hemolysin and cytotoxic necrotizing factor 1

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32
Q

How do we diagnose E. coli?

A

There are specific tests to ID strains

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33
Q

What do we look for to determine that its EHEC?

A

shiga toxin genes

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34
Q

What do we look for to determine that its EIEC?

A

invasion of tissue culture cells or the presence of invasion associated genes

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35
Q

What is the treatment for E. coli diarrhea?

A
  • Fluid replacement

- Antibacterial therapy not indicated

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36
Q

Why aren’t antidiarrheal medications recommended?

A

They increase the contact time of pathogen with intestinal wall which increase the severity of disease.

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37
Q

____: Requires urgent treatment and may need dialysis

A

HUS (hemolytic uremic syndrome)

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38
Q

How do you prevent E. coli diarrhea?

A
  • clean water, pasteurization, proper cooking
  • “boil it, peel it, cook it, or forget it!!”
  • da fuck, get dis preppiness outta ma E. coli notes
39
Q

What can salmonella cause?

A
  • Gastroenteritis and Food Poisoning

- Enteric Fever

40
Q

Salmonella:

Sources?

A

meat, poultry, eggs, dairy products, farmed fishes

41
Q

Salmonella:

When do symptoms of nausea, vomiting and diarrhea start to appear?

A

6-28 hours after ingestion

42
Q

What causes typhoid fever?

A

Salmonella typhi

43
Q

How is Salmonella typhi spread?

A

fecal-contamination of food or water

44
Q

Initial symptoms of enteric fever?

A
  • headache
  • fever (OBVS KUMAR)
  • general malaise
  • abdominal tenderness
  • constipation
45
Q

Once S. typhi reaches gallbladder and Peyer patches, it reaches the ____ stage

46
Q

Enteric fever: list 3 points about it

A
  • gallbladder and biliary tree
  • persistent shedding
  • typhoid mary
47
Q

What is the most common cause of bacterial gastroenteritis?

A

Campylobacter

48
Q

Campylobacter:

High ___

A

ID50

*High ID50 means it is not that virulent

49
Q

Campylobacter:

____ sensitive

50
Q

Campylobacter:

When do symptoms appear?

51
Q

Campylobacter:

What symptoms appear?

A
  • diarrhea with blood and pus (2-3 days)

- abdominal pain longer lasting

52
Q

Campylobacter:

Causes a ____-______ disease

A

self-limited

53
Q

Campylobacter:

Sources?

A
  • poulty

- contaminated meat, water, unpasteurized milk

54
Q

Campylobacter:

Therapy?

A

Fluoroquinolones

Macrolides

55
Q

Vibrio Cholera is present where?

A

water environments, fish, shellfish

56
Q

What does Vibrio Cholera cause?

A
  • rapid dehydration

- rice water stools (many litres)

57
Q

Describe the pathogenesis of Vibrio cholera

A
  • Vibrio cholera ingested in large numbers
  • Sensitive to stomach acid so a large dose is needed to cause disease unless patient achlorhydria or taking antacids
  • Colonization of small intestine depends on motility (polar flagella) production of mucilage attachment to specific receptors
  • Toxin production
  • Massive loss of fluid and electrolytes
  • No damage to enterocytes, no blood or white blood cells in stool
58
Q

List the 4 Shigella species

A

S. sonnei
S. flexneri
S. dysenteriae
S. boydii

59
Q

Shigella species have a low ___

60
Q

_______ is easily transmitted, no animal reservoir

A

Shigellosis

61
Q

What toxin does Shigella produce?

A

Shiga toxin

  • cytotoxic
  • enterotoxic
  • neurotoxic

*Damages epithelial and kidney cells

62
Q

What is the treatment for Shigellosis?

A
  • Rehydration

- Antibiotics in severe cases

63
Q

Clostridium difficile is _____-associated diarrhea

A

antibiotic

*When given antibiotics, it kills some normal microflora. C. dif is not killed by antibiotics and therefore thrives when other normal microflora dies off when antibiotics have been administered.

64
Q

What does Clostridium difficile cause?

A
  • Mild-watery diarrhea to life-threatening toxic megacolon

- Can cause pseudomembranous colitis (neutrophils, fibrin, mucin, cellular debris)

65
Q

What toxins does C. dif produce?

A

TcdA (Toxin A)

TcdB (Toxin B)

66
Q

What is the emergent strain of C. dif?

A

C. difficile 027

67
Q

Why does C. difficile 027 produce more TcdA and TcdB?

A

Because there is a deletion of the regulatory gene (TcdC)

68
Q

Treatment for C. dif?

A
  • Antibiotics for serious infections

- Fecal transplant

69
Q

____ _____: consumption of preformed toxins in food

A

Food poisoning

70
Q

What can food poisoning be caused by? (2)

A
  • Staphylococcus aureus

- Clostridium botulinum

71
Q

S. aureus produces?

A

enterotoxins

72
Q

S. aureus is ____ stable

73
Q

S. aureus is resistant to ???

A

stomach/small intestine enzymes

74
Q

Mechanism of S. aureus?

A
  • Superantigen, bind to MHC class 2 molecules - T-cell stimulation
  • Effects CNS - causes severe vomiting within 3-6 hours after consumption
75
Q

Does S. aureus food poisoning cause diarrhea?

A

no way jose

76
Q

What causes Listeriosis?

A

Listeria monocytogenes

77
Q

Listeria monocytogenes is ____-borne

78
Q

Listeria monocytogenes can multiply at _____

A

4 degrees C

79
Q

Listeria monocytogenes has an infectious dose of _____

80
Q

Who is at enhanced risk of Listeriosis (caused by Listeria monocytogenes)?

A
  • pregnant women

- immunocompromised individuals

81
Q

Describe the life cycle of Listeria

A
  • Endocytosis
  • Then the organism can escape the phagosome
  • Divide in host cell
  • Organism can polymerize the actin pili
  • Form actin tail
  • Actin tail pushes bacteria into a pseudopod that is endocytosized by the new host cell
82
Q

______ are also a major causes of gastroenteritis

83
Q

_____ infants die from gastroenteritis each year

A

> 3 million

84
Q

2 viruses that cause gastroenteritis?

A

Rotavirus

Norovirus

85
Q

Rotavirus:

_______ transmission?

A

oral-fecal

86
Q

Rotavirus:

Symptoms

A
  • vomiting
  • diarrhea
  • fever
87
Q

Rotavirus:

Treatment?

A

fluid and salt replacement

88
Q

Rotavirus:

Vaccine?

89
Q

Norovirus:

Part of ____ family

A

calcivirus

90
Q

Norovirus:

causes ______

A

gastroenteritis

91
Q

Norovirus:

Incubation period

A

24-48 hours

92
Q

Norovirus:

Rate of infection ?

93
Q

Norovirus:

Is ______

A

unculturable

*must use electron microscopy or RT-PCR

Micro 3010 (20 decks)

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