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GI Exam 2 > Intestinal Infections > Flashcards

Intestinal Infections Flashcards

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1
Q

What organism is associated with Guillain-Barre syndrome in adults

A

Campylobacter jejuni - results from similarities between C. j oligosaccharide core of LPS and ganglioside on neural tissue

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2
Q

What two diseases can be caused by Salmonella?

A
  • gastroenteritis

- enteric fever (systemic disease initiating in gut, Typhoid fever)

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3
Q

What organism causes typhoid fever? Major virulence property?

A
  • Salmonella Typhi

- only S. with a capsule - very acid and bile resistant (pH 3-4)

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4
Q

What foods are Salmonella associated with?

A
  • raw chicken and eggs + contaminated produce
  • spring/summer prevalence
  • pet reptiles
  • convalescent human shedders (4-5 weeks)
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5
Q

Who is susceptible to low infective doses of Salmonella?

A

reduced gastric acidity (achlorhydria)

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6
Q

Who is at risk for Salmonellosis?

A
  • 60 but all ages

- infants, elderly, IC

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7
Q

What are the two main Salmonella pathogenicity islands? Function?

A
  • SPI-1 = cell invasion
  • SPI-2 = cell survival
    • BOTH form contact-dependent secretion-injection system
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8
Q

What other illness presentation’s looks very similar to Salmonellosis?

A

Campylobacteriosis

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9
Q

Role of antibiotics in Salmonella treatment?

A
  • do NOT reduce Sx, shorten duration or prevent arthritis

- BUT can prevent CHRONIC carriage

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10
Q

What two symptoms characterize Typhoid Fever?

A
  • high fever

- abdominal symptoms

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11
Q

Reservoir of S. Typhi?

A

HUMANS (Camp and Salmonella are basically zoonoses)

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12
Q

What disease is endemic to India, Africa, Central and South America?

A

Typhoid fever - uncommon in developed countries

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13
Q

Where does S. Typhi live in chronic carriers?

A

gallbladder - grows there

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14
Q

During the invasion phase, where dose S. Typhi do?

A

liver, spleen, bone marrow

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15
Q

Common Typhoid gut manifestation during invasive and serious disease phases?

A

constipation - swelling of ileocecal valve (or pea soup diarrhea in serious disease)

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16
Q

Salmon-colored, blanching, maculopapular rash seen in Typhoid?

A

Rose spot - contains organisms

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17
Q

Sequela that can appear in adults 1-4 weeks after invasive urogenital or enteric infections? Associated?

A
  • reactive arthritis

- HLA-B27

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18
Q

How does Listeria monocytogenes present in healthy people?

A

mild, self-limiting gastroenteritis with watery diarrhea

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19
Q

Growth characteristics of Listeria? Transmission?

A
  • opporunistic gram + rod - grows at 4 degrees, high salt, low and high pH
  • DELI FOODS
  • foodborne, vertical transmission
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20
Q

Most common cause of bacterial diarrheal illness worldwide and #1 cause of bacterial diarrhea in US?

A

Campylobacter jejuni

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21
Q

Morphology of C. jejuni?

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A
  • ‘gull shaped’ - GN, curved to spiral shaped rods
  • Microaerophilic
  • sensitive to acid, but very bile-resistant
22
Q

C. jejuni reservoir and transmission?

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A
  • gut of cattle, sheep, fowl

- fecally contaminated water, milk, poultry, meat

23
Q

When do C. jejuni infections peak?

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A

peaks in summer, fall

24
Q

Carriers of Yersinia? Morphology?

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A
  • GNR, enterobacteriaceae = Y. enterolitica
  • grows in refrigerator (like Listeria)
  • farm, wild, pet animals = ZOONOSIS
25
Who gets Yersiniosis in the US?
pediatric cases - children in day care centers (young, elderly, IC in other countries)
26
Pathogenesis of Yersiniosis?
- intially facultative intracellular | - extracellular after first round of growth (inhibits phago, cytokines)
27
How does Y. enterolitica cause watery diarrhea?
ST-like exotoxin (like ETEC)
28
Where does Yersinia invade?
M cells of terminal ileum
29
Different age group manifestations of Yersinia?
- kids stop at mucosal invasion = diarrhea and fever - youths/adults = invasion of mesenteric LN (watery diarrhea + terminal ileitis + mesenteric lymphadenitis - DDx of acute appendicitis) - elderly, IC = liver and spleen (enteric fever)
30
What Yersinia condition mimics appendicitis?
mesenteric lymphadenitis + terminal ileitis
31
Where is Y. pseudotuberculosis found?
northern Europe and Japan
32
Who gets Y. pseudoTB? Presentation?
- youths 5-20 yo - no enterotoxin = no diarrhea - more invasive than enterolitica = mesenteric lymphadenitis, enteric fever
33
Morphology of Shigella? Presentation?
- GNR (enterbacteriaceae) - ACID resistant - febrile non-bloody diarrhea and bacillary dysentery
34
Most virulent species of Shigella? Most common species in US?
- S. dysenteriae | - S. sonnei (least virulent)
35
Reservoir of Shigella? Transmission?
Colon of HUMANS - LOW infective dose w/ fecal-oral transmission
36
Pathogenesis of Shigella?
M cells in colon - infect and kill macrophages - BM membrane of epi cells - lyse endosome and grow in cytoplasm - recruit actin tails and spread cell to cell
37
How does the human immune response enhance Shigella infection?
- PMNs diapedese to luminal surface and disrupt tight junctions - more bacteria enter paracellular = more inflammation = ulceration (pus in stool) - BUT PMN's win and Shigella doesn't spread deeper
38
Three virulence factors of Shigella?
- enterotoxins (watery diarrhea) - Ipa = invasion plasmid antigen - Ics = intercellular spread
39
What other organism exhibits Stx?
EHEC (requires Stx1 and Stx2 bacteriophages - don't Tx with anti-motiles or AB)
40
What Shigella organism exhibits Stx?
S. dysenteriae type 1 strain - hemorrhagic colitis - HUS (glomerular endo cells - ER disruption due to inhibition of protein synthesis = coagulopathy)
41
What two Shigella organisms can progress from watery diarrhea to dysentery?
- S. flexneri, dysenteriae | - presents as biphasic disease (watery diarrhea - scant stools/abdominal cramps/tenesmus)
42
What protozoan causes 'flask-like' ulcers in the colon?
Entamoeba histolytica (ulcers with narrow mucosal neck and spreading base in lamina propria)
43
Invasive form of E. histolytica?
- TROPH -- VERY invasive - contact lysis invades to muscularis mucosa then invades laterally, DESTROYS PMNs - cyst - 90% are asymp and shed cysts
44
Complications of amebic colitics (E. histolytica)?
- 90% dysentery or bloody diarrhea w/out systemic Sx - gradual onset over 1-2 weeks - can become chronic (like IBD) - spread to other organs in males > females = LIVER, pleura, pericardium, brain
45
What two C. diff toxins cause diarrhea, necrosis, inflammation and lesions covered with pseudomembrane?
TcdA and TcdB - work synergystically (A is responsible for diarrhea, B is a potent cytotoxin = nec/inf)
46
C. diff morphology?
Gram + anaerobic spore-forming rod (spores are very hard to kill - soap, not germex)
47
Two main AB for C. diff? Newer, more specific drug? Recurrence rate?
- metro and vanc - fidaxomicin (not absorbed systemically) - 20-30%
48
What % of C. diff cases are CA vs. HA?
20% (increasing)
49
What causes tissue injury in C. jejuni infections?
- cytolethal distending toxin (CDT) | - acute inflammatory reaction
50
What is Guillain-Barre syndrome?
autoimmune disease of peripheral nervous system (C. jejuni) = flaccid paralysis
51
Occurence and prognosis of GB syndrome?
- 20-50% in USA 2-3 weeks following C. jejuni infection | - partial or complete recovery within 2-3 weeks to months

GI Exam 2 (3 decks)

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