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(J2) GI II Test 1 > Infectious Enterocolitis (Bacterial and Viral) > Flashcards

Infectious Enterocolitis (Bacterial and Viral) Flashcards

1
Q

What are the most common causes of traveler’s diarrhea?

A
  • ETEC
  • campylobacter jejuni
  • salmonella
  • shigella
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2
Q

Where does Vibrio cholerae come from?

(endemic areas/reservoirs and transmission)

A

endemic to India > Gulf of Mexico

reservoirs: shellfish

fecal-oral transmission:

-contaminated drinking water (think natural disasters)

-food

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3
Q

How are Vibrio cholerae infections typcially described?

A
  • comma shaped, gram-negative
  • oxidase-positive
  • single, polar flagella
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4
Q

How does Vibrio cholerae cause disease?

A

Cholera toxin:

  • enters cell via GM1
  • toxin activates Gs protien -> activates adenylate cylcase -> increased cAMP -> CFTR activation
  • increased in intraluminal chloride -> secretory diarrhea
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5
Q

What is the presentation of cholera?

(complications?)

A
  • diarrhea; “rice-water” stools
  • “fishy” smelling stool
  • fever
  • vomiting

Complications:

  • severe dehydration
  • hypotension/shock
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6
Q

How is cholera treated?

A

fluid replacement (typically sufficient w/o abx)

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7
Q

Where does Campylobacter jejuni come from?

(endemic areas/reservoirs and transmission)

A
  • livestock act as reservoir (especially chicken)
  • more pervalent in developed countries

Fecal-oral transmission:

  • infected animal products (especially poultry)
  • contaminated water
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8
Q

What is Campylobacter jejuni the most common cause of?

A
  • most common cause of bacterial enterocolitis in developed countries
  • common cause of “traveler’s diarrhea”
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9
Q

How are Campylobacter jejuni infections typcially described?

A
  • comma shaped, gram-negative
  • oxidase-positive
  • single, polar flagella
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10
Q

How does Campylobacter jejuni cause disease?

A

Specific mechanism unclear

Virulence properties:

  • toxin production (certain strains)
  • invasion (certain strains)
  • motility
  • adherence
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11
Q

What is the presentation of campylobacter enteritis?

(complications?)

A
  • influenza-like prodrome
  • watery diarrhea
  • bloody, inflammatory diarrhea (dysentery, associated with strains capable of mucosal invasion)

Complications:

  • reactive arthritis (associated with HLA-B27)
  • Guillian-Barré (0.1%; ascending, demylinating neuropathy -> parasthesia and weakness)
  • erythema nodosum
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12
Q

How is campylobacter enteritis treated?

A
  • self-limiting, treatment typically not needed
  • abx in severe cases
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13
Q

Where do Shigella spp. come from?

(endemic areas/reservoirs and transmission)

A
  • humans are only reservoir
  • more prevalent in underdeveloped countries

Fecal-oral transmission:

  • contaminated food
  • contaminated water
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14
Q

How are Shigella spp. infections typcially described?

A
  • gram-negative
  • unencapsulated
  • nonmotile
  • facultative anaerobe
  • green colonies (HE agar; vs. black colonies in similar appearing Salmonella)
  • preferentailly infect left colon followed by ileum
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15
Q

How do Shigella spp. cause disease?

A

Shiga toxin:

-affects 60S ribosomal subunit, inhibiting protein synthesis -> enterocyte damage

Invasion:

  • tropism for M cells
  • can survive intracellularly, evading immune system
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16
Q

What is the presentation of shigellosis?

(complications?)

A
  • watery diarrhea -> dysentery
  • fever
  • abdominal pain

Atypical presentatin:

-can mimic ulcerative colits in adults as waxing and waning diarrhea

Complications:

  • uncommon triad of reactive arthiritis, urethritis, and conjunctivitis (associated with HLA-B27)
  • HUS (associated with shiga toxin and EHEC shiga-like toxin)
  • toxic megacolon
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17
Q

How is shigellosis treated?

A
  • self-limiting (2-7 days), treatment typically not needed
  • abx in severe cases

**antidiarrheals contraindicated, prolong symptoms and delay clearance of Shigella**

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18
Q

What causes Salmonelosis and where does it come from?

(endemic areas/reservoirs and transmission)

A

non-typhoidal salmonella, Salmonella enteritidis

  • livestock act as reservoir (particularly chicken)
  • prominent worldwide

Fecal-oral transmission:

-contaminated animal products (particularly poultry)

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19
Q

How are Salmonella enteritidis infections typcially described?

A
  • gram-negative, w/ multiple flagella
  • obligate pathogen
  • acid-labile
  • do not ferment lactose
  • produces hyrdogen sulfide -> black colonies (HE agar; vs. green colonies in similar appearing Shigella)
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20
Q

How does Salmonella enteritidis cause disease?

A

Invasion:

  • tropism for M cells
  • can survive intracellularly, evading immune system
21
Q

What is the presentation of salmonellosis?

(complications?)

A

-severe watery diarrhea -> dysentery

-severe vomiting

  • fever
  • abdominal pain

Complications (related to systemic infection):

  • bacteremia/sepsis
  • reactive artritis
22
Q

How is salmonellosis treated?

A
  • self-limiting (3-7 days), treatment typically not needed
  • abx in systemic cases only as they prolong carrier state
23
Q

What causes Typhoid fever and where does it come from?

(endemic areas/reservoirs and transmission)

A
  • Salmonella enterica* (typhi/paratyphi)
  • endemic to India, Mexico, and the Phillipines
  • endemic populations tend to be infected with S. typhi
  • visitors to endemic regions tend to be infected with S. paratyphi
  • humans are only reservoir

Fecal-oral transmission:

  • contact
  • contaminated water
  • contaminated food
24
Q

How are Salmonella typhi/paratyphi infections typcially described?

A
  • gram-negative, w/ multiple flagella
  • obligate pathogen
  • produces hyrdogen sulfide
  • do not ferment lactose
  • enlarged Peyer patches in distal ileum

-typhoid nodules in the liver (macrophage aggregates)

25
Q

How do Salmonella typhi/paratyphi cause disease?

A

Invasion:

  • tropism for M cells
  • can survive intracellularly, evading immune system
  • capable of disseminateing via lymph and blood vessels (unlike non-typhoidal salmonella)
26
Q

What is the presentation of Typoid fever?

(complications?)

A

Initial infection:

  • bloody diarrhea (“pea soup” green)
  • N/V
  • abdominal pain/bloating

Febrile phase (preceeded by brief asymptomatic period):

  • fever
  • “rose spots” on chest and abdomen

Complications:

  • cholecystitis (chronic carriers)
  • encephoapathy
  • myocarditis
27
Q

How is typhoid fever treated?

A

antibiotics in all causes unlike non-typhoidal salmonella

28
Q

What causes Yersiniosis and where does it come from?

(endemic areas/reservoirs and transmission)

A

Yersinia enterocolitica and Yersinia pseudotuberculosis (not Y. pestis)

  • domestic animals (dogs/cats)
  • cows/pigs
  • endemic in northern and central Europe

Fecal-oral transmission:

  • dog/cat feces
  • consumption of raw pork or unpasturized milk
  • contaminated water
29
Q

How are Yersinia spp. infections typcially described?

A
  • gram-negative, rod-shaped
  • obligate pathogen
  • bipolar staining -> “safety pin” appearance
  • preferentially affects right side -> ileum, appendix, and right colon (mimics Crohn disease and appendicitis)
30
Q

How do Yersinia spp. cause disease?

A

Invasion:

-tropism for M cells

31
Q

What factor increases the virulence of Yersinia spp.?

A

-increased non-heme iron

32
Q

What is the presentation of yersiniosis?

(complications?)

A

-abdominal pain (can mimic appendicitis)

-N/V

  • fever
  • diarrhea (can be bloody)

Complications:

  • sepsis (associated with high non-heme iron)
  • reactive arthritis (associated with HLA-B27)
  • erythema nodosum
33
Q

How are E. coli infections typcially described?

A
  • gram-negative, baccili
  • flagellated
34
Q

What causes EHEC and how does it cause disease?

A

E. coli O157:H7

  • produces Shiga-like toxin -> HUS
  • widespread with many reservoirs; cattle are most notable
35
Q

What is the presentation of EHEC infection?

(complications?)

A
  • watery diarrhea -> bloody/dysentery
  • fever
  • abdominal pain

Complications:

-HUS (due to to Shiga-like toxin)

36
Q

How are EHEC infections treated?

A

antibiotic are contraindicated; increase release of shiga-like toxin increasing risk of HUS

37
Q

What causes pseudomembranous colitis and where does it come from?

(endemic areas/reservoirs and transmission)

A

Clostridioides difficile

-hospitals act as reservoirs

not so much transmitted as allowed to grow

many people are colonized but asymptomatic, antibiotic use/immune suppression allow for overgrowth

38
Q

How is pseudomembranous colitis typically described?

(bacteria and pseudomembrane)

A
  • gram-positive, bacillus
  • spore forming
  • toxin A/B (diagnostic)
  • obligate anaerobe
  • formation of pseudomembranes (not specific)
  • exudate eruption from crypts (pathognomonic)
39
Q

How does C. difficile cause disease?

A

Toxin A (enterotoxin):

-damages brush borders

Toxin B (cytotoxin):

  • disruption of cytoskeleton
  • loss of tight junctions
  • apoptosis
40
Q

What is the presentation of pseudomembranous colitis?

(complications?)

A
  • watery diarrhea (occsionally with leukocytes and blood)
  • fever
  • abdominal pain
  • leukocytosis

Complicaitons:

  • dehydration
  • protein loss -> hypoalbunemia
  • toxic megacolon
41
Q

How is pseudomembranous colitis treated?

A

metronidazole and vancomycin

42
Q

What causes Whipple disease and how does it cause disease?

A

Tropheryma whippelii

bacteria grow in macrophages which then accumulate in the lamina propria and LNs of the bowel -> obstruction of lymph flow -> fat malabsorption

43
Q

How is Whipple disease typically described?

A

-intracellular, gram-positive

PAS-positive foamy macrophages in the lamina propria (DDx intestinal tuberculosis; acid-fast stain differentiates, negative in T. whippelii)

44
Q

What is the presentation of Whipple disease?

A

Triad:

  • diarrhea (malabsorptive)
  • weight loss
  • arthralgia
45
Q

What are the viral causes of diarrhea?

A
  • norovirus
  • rotavirus
  • adenovirus
46
Q

What are important notes about norovirus?

(description, population, transmission)

A

-icosahedral, ssRNA virus

causes self-limited diarrhea in both adults and children

  • outbreaks associated with water contamination
  • sporadic cases associated with person-to-person transmission
47
Q

What are important notes about rotavirus?

(description, population)

A

encapsulated, segemented, dsRNA virus

  • severe diarrhea in children
  • significant cause of mortality in chidlren
48
Q

What are bacterial causes of secretory diarrhea?

A

(J2) GI II Test 1 (14 decks)

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