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Microbiology > GI Tract Infections > Flashcards

GI Tract Infections Flashcards

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1
Q

What is considered true food poisoning?

A
  • the consumption of preformed toxin within the food that may be chemical or bacterial in nature - the toxins survive cooking and heating
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2
Q

What is a toxin associated infection?

A
  • the food is simply the vehicle for the pathogen to grow and multiply to numbers large enough to cause infection
  • ex. Campylobacter and Salmonella
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3
Q

What are the three ways for GI infections to cause disease?

A
  • Fluid imbalance (changes balance of water and electrolytes in the small bowel, leading to a massive fluid secretion)
  • Cell destruction and inflammation (invasion/cytotoxin production)
  • Invasion (penetrate the intestinal mucosa -> spread and multiply outside the bowel)
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4
Q

Diarrhea is an increase in fluid and electrolyte loss in the ____

A

gut lumen

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5
Q

How many different groups of E.coli are there?

A

6

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6
Q

Describe enteropathogenic E.coli (EPEC)

A
  • affects babies and young children

- virulence factors: adhesins, bundle forming pili and intimin - attaches to epithelial cells and microvillus

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7
Q

Describe enterotoxigenic E.coli (ETEC)

A
  • affects children
  • binds to receptors on cell membrane of small intestine
  • plasmid encoded toxins
    • heat labile toxin (LT) - similar mode of action as cholera toxin
    • heat stable toxin (ST) - increase in guanylate cyclase activity -> increase cGMP -> increases fluid secretion
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8
Q

Describe enterohaemorrhagic E. coli (EHEC)

A
  • invasive AND makes toxins
  • verotoxins 1 and 2 (VTEC)
    • aka “shiga like toxin”
    • SLT-1 and SLT-2
  • toxins damage the large intestine (inhibit protein synthesis)
  • ulceration and bleeding
  • serotype O157:H7
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9
Q

What syndromes/ symptoms can be caused by enterohaemorrhagic E.col?i

A
  • hemorrhagic colitis (HC)- destruction of mucosa leads to hemorrhage
  • hemolytic uremic syndrome (HUS) - toxin gets absorbed in bloodstream. Verotoxin receptors found in renal epithelium- may account for kidney damage
  • causes symptoms of anemia due to destruction of RBCs and low platelet count and sudden kidney damage
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10
Q

Describe enteroinvasive E.coli (EIEC)?

A
  • attach to the mucosa of the large intestine
  • invade cells by endocytosis, multiply, spread to adjacent cells, cause tissue destruction and then inflammation and ulceration
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11
Q

Describe enteroaggregative E.coli? (EAEC)

A
  • stacked brick appearance on tissue culture cells
  • aggregation: plasmid encoded fimbria
  • toxins produced by role in diarrheal disease is uncertain
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12
Q

Describe diffuse aggregative E.coli (DAEC)

A

alpha hemolysin and cytotoxic necrotizing factor 1

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13
Q

What test could be done to identify the EHEC strain of E.coli?

A

testing for shiga toxins

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14
Q

What can be done to identify the EIEC strain of E.coli?

A

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

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15
Q

Do you have to use antibiotic therapy to treat diarrhea caused by E.coli?

A
  • no

- need to focus on fluid replacement

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16
Q

What is the consequence of using antidiarrheal medications?

A
  • increase the contact time of the pathogen with the intestinal wall - therefore this increases the disease severity
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17
Q

What is HUS and what is needed to treat it?

A
  • known as hemolytic uremic syndrome
  • is a complication of an E.coli infection and can cause kidney failure
  • need to undergo dialysis
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18
Q

What is the best method of prevention of an E.coli infection?

A
  • clean water, pasteurization, proper cooking

- boil it, peel it, cook it or forget it

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19
Q

Whittier the most common symptoms of salmonella poisoning?

A
  • meat, poultry, eggs, dairy products and farmed fish
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20
Q

When are the symptoms of salmonella noticeable after ingestion?

A
  • 6-48 hours after ingestion
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21
Q

What aret eh most common symptoms of salmonella poisoning?

A
  • nausea, vomiting and diarrhea
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22
Q

Salmonella may be excreted in ___ for several weeks post infection

A

feces

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23
Q

Food handlers that test positive for salmonella are excluded from work until ______

A

3 fecal specimens come back negative

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24
Q

What bacteria is known to cause typhoid fever?

A
  • S. typhi
25
Q

What is the general spread of typhoid fever?

A
  • fecal contamination of food or water
26
Q

What are the symptoms of typhoid fever?

A
  • headache
  • fever
  • malaise
  • abdominal tenderness
  • constipation
27
Q

Describe enteric fever

A

(aka typhoid fever)
- once you contract it, you are a chronic colonizer- it stays in the gallbladder and the biliary tree, causing persistent shedding that can last for years

28
Q

Campylobacter species are the most common cause of bacterial _____

A

gastroenteritis

29
Q

Campylobacter is a heat ___ bacteria

A

sensitive

30
Q

What are the most common symptoms of campylobacter infections?

A
  • diarrhea with blood and pus (2-3 days)
  • abdominal pain that is longer lasting
  • self-limiting disease
31
Q

How long after campylobacter infestation do symptoms typically arise?

A
  • within 2-5 days
32
Q

What are the sources of a campylobacter infection?

A

poultry

contaminated meat, water unpasteurized mill

33
Q

What are the main antibiotic therapies for a campylobacter infection?

A
  • fluoroquinolones

- macrolides

34
Q

What pathogen causes cholera?

A
  • Vibrio cholera
35
Q

Where does cholera have the most effect in the world?

A
  • SE Asia, parts of SA and Africa
36
Q

What spreads cholera infections?

A
  • cholera is spread by contaminated food and water - never spread by human contact
37
Q

What are the symptoms associated with a cholera infection?

A
  • severe watery, non bloody diarrhea that is known as rice water diarrhea due to its appearance
  • this is due to the presence of a enterotoxin in the GI tract
  • can be a loss of fluid up to 1 L an hour, which can cause dehydration, metabolic acidosis, hypokalaemia and hypovolaemic shock resulting in cardiac failure
38
Q

What is the pathogenesis of vibrio cholera?

A
  • vibrio cholerae is ingested in large numbers
  • sensitive to stomach acid, large doses needed to cause disease unless the patient is achlorhydria or taking antacids
  • colonization of the small intestine depends on the motility, production of mucinase or the attachment to specific receptors- this can
    all lead to toxin production
  • this in the end leads to a massive loss of fluid and electrolytes form the GI tract
39
Q

Shigella species have a ___ ID50 (or the amount of bacteria that produces an infection in 50% of individuals)

A

low

40
Q

Shigella species are ____ transmitted and have no____

A

easily

animal reservoir

41
Q

What is the pathogenesis of a shigella infection?

A
  • shigella attach to and invade the mucosal epithelium of the distal ileum and the colon, causing inflammation and ulceration
  • they produce a toxin that also can cause damage to the epithelial and kidney cells
42
Q

What is the treatment options for shigellosis?

A
  • rehydration

- antibiotics in severe cases

43
Q

C. diff infections cause what?

A

diarrhea (can be mild-watery) to life threatening toxic megacolon needing surgical intervention

44
Q

What is the characteristic sign of c. diff infections?

A
  • changing the pseudomembrane to pseudomembranous colitis

- caused by an influx of neutrophils, fibrin, mucin and cellular debris

45
Q

What is the treatment for C. diff infections?

A
  • antibiotics

- fecal transplants

46
Q

What is food poisoning caused by?

A
  • Staph aureus enterotoxin and Clotridium botulinum toxin (consumption of preformed toxins in food)
  • S. aureus enterotoxin
47
Q

Describe the S aureus enterotoxin

A
  • heat stable and resistance to stomach/small intestine enzymes
  • mechanism of action: super antigen, binds to MHC class 2 molecules -> T cell stimulation
  • effects on CNS - severe vomiting within 3-6 hours after consumption
  • no diarrhea
48
Q

What pathogen causes listeriosis?

A
  • liesteria monocytogenes
49
Q

Listeria is a ___ borne illness that can multiply at 4 degrees, with an infectious dose of under 1000

A

food

50
Q

Who is at an enhanced risk of listeriosis?

A
  • pregnant women

- immunocompromised individuals

51
Q

Rotavirus is spread via ____ transmission

A

oral-fecal

52
Q

What are the symptoms of a rotavirus infection?

A
  • vomiting
  • diarrhea
  • fever
53
Q

What is the treatment for a rotavirus infection?

A
  • fluid and salt replacement
54
Q

What virus family is norovirus from?

A
  • calcivirus family
55
Q

What does norovirus cause?

A
  • gastroenteritis
56
Q

What is the incubation of period of norovirus?

A
  • 24-48 hours
57
Q

What is the rate of infection of those coming into contact with norovirus?

A
  • 50%
58
Q

How is norovirus detected? Is it culturable?

A
  • NO -not culturable

- detected by electron microscopy or PCR

Microbiology (16 decks)

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