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Medical Microbiology > Lecture 16 and 17: GI Infections (!) > Flashcards

Lecture 16 and 17: GI Infections (!) Flashcards

1
Q

Which family of gram (-) facultative, anaerobic, rod-shaped bacteria are commonly found in the GI?

A

Enterobacteria

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2
Q

Three ways the GI infections can be transmitted?

A
  1. Fecal oral
  2. Fomites
  3. Food and water borne
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3
Q

What’s the difference between Diarrhea and Dysentery–both of which are symptoms of GI infections?

A
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4
Q

True or False: C. perfringes, B. cereus, and S. aureus are associated with food BORNE DIARRHEAS

A

True

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5
Q

V. cholerae and ETEC cause infection by adherence to ___ and release of ___
A. enterocytes; toxoid
B. intestinal mucosa; toxoid
C. intestinal mucosa; toxin

A

C. intestinal mucosa; toxin

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6
Q

C. dif and EHEC cause infection by adherence to ___ and release of toxin resulting in destruction of ___ or ___

A

intestinal mucosa
brush border/mucosa

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7
Q

___ is the only pathogen to cause infection via mucosal invasion and proliferation within enterocytes
A. Salmonella
B. C. dif
C. EHEC
D. Campylobacter
E. Shigella

A

E. Shigella

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8
Q

Which three pathogens cause diarrheal disease via: mucosal translocation + proliferation within lamina propria and lymph nodes?

A

Salmonella
C. jejuni
Yersinia enterocolitica

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9
Q

Which two viruses can cause infection + destruction of enterocytes, resulting in osmotic diarrhea?

A

Rotavirus
Norwalk Virus

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10
Q

Which pathogen causes Gastritis?

A

H. pylori

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11
Q

H. pylori is…
- Gram (+) or (-)?
- Shape?
- Acid Intolerant/Tolerant?

A
  • Gram (-)
  • Curved Rod
  • Motile
  • Acid Tolerant
  • Microaerophilic
  • Non-invasive
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12
Q

Which enzyme does H. pylori have that permits it to be acid tolerant?

A

Urease

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13
Q

___: Most common virulence factor of H. pylori, which damages gastric epithelial cells by inducing vacuoles + is responsible for gastric ulcers (!!!)
A. Vacuolating Cytotoxin
(Vac A)
B. Cytotoxin Associated Gene A (CagA)
C. Urease

A

A. Vacuolating Cytotoxin
(Vac A)

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14
Q

___ is not found in all strains of H. pylori and increases virulence. Further, it induces inflammation + destruction of mucosa + is responsible for gastric cancer
A. Vacuolating Cytotoxin
(Vac A)
B. Cytotoxin Associated Gene A (CagA)
C. Urease

A

B. Cytotoxin Associated Gene A (CagA)

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15
Q

Clinical significance of Urease?

A

Degrades Urea to Ammonia and Bicarbonate

NH3 raises stomach acid, making it more basic, so that H. pylori can grow!

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16
Q

How do diagnose H. pylori?

A
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17
Q

Which two pathogens can cause watery diarrhea but no fever (afebrile)
A. ETEC
B. V. cholerae
C. E. coli
D. Cutibacterium acnes

A

A. ETEC (Enterotoxigenic E. coli)
B. V. cholerae

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18
Q

True or False: ETEC/E.coli are leading cause of Traveler’s Diarrhea

A

True

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19
Q

Features of E. Coli?
- Gram (+)/(-)
- Shape
- Aerobe? Anaerobe?
- Coliform?

A

E.coli
- Gram (-)
- Rod
- Facultative anaerobe
- Coliform: ferments lactose, produces gas + acid

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20
Q

ETEC (Enterotoxigenic E. coli) causes afebrile state + watery diarrhea by attaching to SMALL INTESTINES and secreting which two enterotoxins?

A

1) Heat Labile (LT): Antigenic, activates adenylyl cyclase and increases cAMP

2) Heat Stable (ST): Non-antigenic, activates guanylyl cyclase and increases cGMP

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21
Q

True or False: Both the toxins secreted by ETEC and the Cholera Toxin (similar to LT) cause mucosal cells to secrete fluid and electrolytes

A

True

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22
Q

True or False: E.coli is lactose positive (+)

A

True

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23
Q

___ is a high dose organism/pathogen that causes watery diarrhea without fever that uses saltwater or contaminated food (e.g shellfish) as a vehicle
A. E.coli
B. ETEC
C. V. cholerae

A

C. V. cholerae

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24
Q

True or False: V. cholerae are halophilic, non-invasive, gram negative curved rods

A

True

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25
Q

V. cholerae produces _____ toxin – which is similar to _____ of ETEC – and causes mucosal cells to secrete fluids + electrolytes. This secretion is responsible for disease manifestation

A

Cholera Toxin (CT);
Heat Labile (LT)
electrolytes and fluids

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26
Q

True or False: Heat Labile Toxin (LT) of ETEC is encoded on a bacteriophage

A

False - Cholera Toxin of V. cholerae is!

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27
Q

True or False: Cholera Toxin (CT) is an AB5 toxin that is heat-labile, just like Heat Labile Toxin (LT) of ___

A

ETEC

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28
Q

Which subunit of the cholera toxin binds to ganglioside (GM1) on the intestinal epithelial cells
A. Alpha
B. B subunit
C. A subunit
D. Beta subunit

A

B. B subunit

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29
Q

How do you diagnose V. cholera?

A
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30
Q

Which three pathogens are food borne diseases associated with Afebrile watery diarrhea (intoxication)?

A
  1. S. aureus
  2. Bacillus cereus
  3. Clostridium perfringens (Type A)
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31
Q

What are four features that are shared by: S. aureus, Bacillus cereus, and C. perfringens have in common (food borne pathogens - associated w/afebrile watery diarrhea)?

A
  1. Abx don’t help
  2. No RBC/WBC in stool
  3. Cause: inadequate cooking, holding temp
  4. Not transmissible
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32
Q

True or False: In the staphylococcal and emetic forms of Bacillus cereus, the food borne diseases are pre-formed in food

A

True

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33
Q

The diarrheal forms of ___ and ___ (type A) are associated with toxin released in gut from ingested bacteria – in food borne disease commonalities

A

C. perfringens (type A) and B.cereus

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34
Q

True or False: The emetic form of B. cereus is a toxin released in the gut from ingested bacteria while the diarrheal form is preformed in food

A

False

1) Emetic form of B. cereus = preformed in food

2) Diarrheal form of B. cereus = toxin release in gut from ingested bacteria

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35
Q

Features of S. aureus?
- Gram (+) or (-)
- Shape?
- Coagulase (+) or (-)

A

Gram (+)
Cocci
Coagulase (+)

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36
Q

What is the toxin produced by some S. aureus known as? Features?

A

SET (staph entertoxin)
- heat stable
- acute emetic and diarrheal disease when toxin consumed via foods

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37
Q

Which of the following pathogens may be found in processed meats, canned foots, potato salads, or boston cremes :c ????
A. S. aureus
B. Bacillus cereus
C. C. perfringens

A

A. S. aureus

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38
Q

True or False: When S. aureus produces its enterotoxin, it is ingested, absorbed in the gut, and acts on the vomiting center in the CNS

A

True

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39
Q

___ is a gram (+), aerobic, spore forming rod that can lead to food borne disease, particular if one eats potatoes, rice, or veggies

A

Bacillus cereus

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40
Q

Bacillus cereus produces two enterotoxins: a heat stable (emetic) form and a heat labile (diarrheal) form – which is preformed in food? which proliferates in small intestines?

A

Emetic form
- heat stable
- pre-formed in food

diarrheal form
- organism proliferates in small intestine => heat labile enterotoxin => s/s

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41
Q

Which form of entertoxin, produced by Bacillus cereus, functions by stimulating adenylate cyclase (much like ETEC and CT)?
A. Heat Stable (vomit)
B. Heat Labile (diarrheal)

A

B. Heat Labile (diarrheal)

42
Q

Which of the following anaerobic, gram (+), spore forming rods may be found in meat, poultry????
A. S. aureus
B. Bacillus cereus
C. C. perfringens

A

C. C. perfringens

43
Q

What are two features of the entertoxin of Clostridium perfringes?
A. Heat labile; acid labile
B. Heat stable; acid labile
C. Heat labile; base labile

A

A. Heat labile; acid labile

44
Q

The enterotoxin made by C. perfringens (type A) functions by inhibiting ___ and ____ ion absorption

A

glucose; chloride

45
Q

True or False: C. perfringens proliferates in the small intestines, which leads to entertoxin production, which produces s/s

A

True

46
Q

How do you dx C. perfringens?

A

Detect spores in food or feces

47
Q

What is an example of a Shiga-like/Verotoxin-toxin (STEC/VTEC) E.coli?

A

Enterohemorrhagic E.coli (EHEC, O157:H7)

Note: O157:H7 = sorbitol negative fermenter (therefore: white)

48
Q

True or False: EHEC and STEC/VTEC are associated with diarrheas accompanied by a fever

A

False - w/ or w/o fever

49
Q

Virulence factor used by Enterohemorrhagic E.coli?
A. Pili
B. Shiga-like toxin
C. Sorbital toxin

A

B. Shiga-like toxin (aka: verocytotoxin)

50
Q

What are two effects of Shiga toxin?

A

1) GI Bleeds - hemorrhagic colitis
2) Hemolytic Uremic Syndromes - HUS

51
Q

____: A triad that consists of hemolytic anemia + acute kidney failures + low platelet count
A. HUS
B. Hemorrhagic Colitis

A

A. Hemolytic Uremic Syndromes (HUS)

52
Q

True or False: ETEC is a gram negative bacilli - most common serotype is O157:H7

A

False - EHEC

53
Q

Why is STEC/EHEC able to be spread person to person?
A. Poor hygiene and low dose organism
B. Poor hygiene and high dose organism

A

A. Poor hygiene and low dose organism

54
Q

True or False: Raw milk or apple juice could lead to STEC/EHEC

A

True

55
Q

Two virulence factors used by STEC/EHEC?

A
  1. Pilli (adherence in small intestines)
  2. Stx (toxemia)
56
Q

True or False: HUS is a bacteremia - not a toxemia

A

False - it is a TOXEMIA not a bacteriemia!

57
Q

Are abx’s an effective tx for STEC/EHEC?

A

No! They can increase amount of toxin produced, leading to poor outcomes

58
Q

Stx of the EHEC binds to the ___ receptors, which can be found in a renal and gut endothelial cells
A. Gb1
B. Gb2
C. Gb3

A

C. Gb3

59
Q

Diagnosing STEC/EHEC?

A
60
Q

C. dif and Clostridioides difficile-associated disease (CDAD) are associated with diarrheas that present:
A. without a fever
B. without or with fever
C. with a fever

A

C. with a fever

61
Q

___: Inflammation of large intestine

A

Colitis

62
Q

___ is a gram (+), anaerobic rod, spore-form, that mostly has toxigenic strains

A

C. dif

63
Q

C. dif can produce one or both of its toxins (Toxin _ or _)

How do these toxins function?

A

Toxin A/B
- Function as cytotoxins , disrupt protein synthesis within host cells

64
Q

What are two pre-disposing factors to acquiring C. dif?

A
  1. Hospitalization
  2. Abx therapy
65
Q

True or False: People on antacids or PPI have greater chance of developing C. Dif

A

True

66
Q

True or False: C. Dif should be suspected in any patient with diarrhea who has received abx within the past two months/who have had diarrhea began 72 hrs or more after hospitalization

A

True

67
Q

Febrile, Invasive Diarrheal Agents (Bacillary Dysentary) is associated with which pathogen?

A

Shigella

68
Q

True or False: Shigella is a facultative, intracellular gram negative rod, non-motile. It is a lactose fermenter.

A

False - it is NOT a lactose fermenter (non coliform)

69
Q

Bacillary dysentery (enterocolitis) –inflammation of small intestine and colon–is a clinical manifestation of ___

A

Shigella

70
Q

How is Shigella transmitted?

A

1) Oral Fecal
2) Contaminated food

71
Q

True or False: Shigella has very high infectious dose

A

False - very low infectious dose

72
Q

How is Shigella classified?

A

By O antigen (serogroups)

73
Q

S. dysenteriae, which is associated with HUS due to shiga toxin production, belongs to:
A. Group A
B. Group B
C. Group C
D. Group D

A

A. Group A

74
Q

Taxonomy of Shigella?

A
75
Q

True or False: Sheep and cows are the sole reservoir/host of Shigella

A

False - humans are sole reservoir/host

76
Q

What is the most communicable bacterial diarrheal agent?

A

Shigella

77
Q

What causes the inflammation, bleeding, abscess formation, and sloughing off of cells, as seen in Shigella?

A

Immune response

78
Q

True or False: Shigella goes to the small intestines (diarrhea) then colon, where it escapes phagocytosed by macrophages

A

True

79
Q

Shigella Virulence summary?

A
80
Q

Which three pathogens are febrile, invasive diarrheal agents?

A
  1. C. jejuni
  2. Yersinia
  3. Salmonella
81
Q

What three features do (C. jejuni, Yersinia, Salmonella – all of which are febrile, invasive diarrheal agents) have in common?

A
  1. Gram (-) and non-lactose fermenting
  2. Zoonosis
  3. Invasive (can cause bacteremia)
82
Q

True or False: Of C. jejuni, Yersinia, Salmonella – only Yersinia and C. jejuni can survive in macrophages (facultative intracellular)

A

False - Yersinia and Salmonella can survive in macrophages but not C. jejuni

83
Q

If a patient is infected with either: C. jejuni, Yersinia, or Salmonella and has a fever, what test should be done?

A

Blood culture to dx febrile, invasive diarrheal agents

84
Q

___ is a gram (-) , oxidase (+) comma shaped motile rod that is NF in GIT of dogs, livestock

A. C. jejuni
B. Yersinia
C. Salmonella

A

A. C. jejuni

85
Q

True or False: The virulence factor LT of C. jejuni is ~ to ETEC/CT

A

True

86
Q

True or False: C. jejuni can be transmitted via raw milk, undercooked chicken and is a high dose organism.

Person to person spread is not usual.

A

False - it is low dose organism

87
Q

True or False: C. jejuni is a intracellular pathogen that can cause inflammatory enteritis

A

False - extracellular pathogen that can cause inflammatory enteritis

88
Q

How can you dx C. jejuni?

A

Look for WBC in stool

89
Q

Which pathogen is an important cause of pseudoappendicitis?

A

Yersinia
- small motile rods
- safety pin

90
Q

What are two ways to transmit Yersinia?

A
  1. blood transfusion
  2. food
    - milk
    - meat (canned)
91
Q

Yersinia penetrates epithelial lining, specifically ___ and __.

Where does it live?

A

Ileum + Colon
Lives: lymphoid tissue

92
Q

For yersinia, the ___ render killing by macrophage

A

OMP’s

93
Q

True or False: Yersinia enterotoxin is similar to ST of ETEC

A

True

94
Q

Dx yersinia?

A

Special media + cold enrichment

95
Q

True or False: Salmonella is a non-lactose, fermenting, motile, gram (-) rod - non-coliform

A

True

96
Q

True or False: S. typhi causes typhoid (enter) fever

A

True

97
Q

True or False: Salmonella is a high dose organism that usually has animals as its reservoir – except in case of S. typhi (human host adapted)

A

True

98
Q

Can salmonella survive in macrophages or disseminate via circulation?

A

Yes - can do both

99
Q

Salmonella invades mucosa of which two organs?

A

Small Intestine and colon

100
Q

How does Salmonella result in diarrhea? inflammation?

A

Diarrhea = stimulates fluid secretion

Inflammation = penetrates epithelial cells to lamina propria

101
Q

True or False: Salmonella can cause toxemia

A

True

102
Q

True or False: Shigella is lactose negative while E.coli is lactose positive

A

True

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