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GI Exam 2 > Intestinal Infections > Flashcards

Intestinal Infections Flashcards

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?

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

C. jejuni reservoir and transmission?

A
  • gut of cattle, sheep, fowl

- fecally contaminated water, milk, poultry, meat

23
Q

When do C. jejuni infections peak?

A

peaks in summer, fall

24
Q

Carriers of Yersinia? Morphology?

A
  • GNR, enterobacteriaceae = Y. enterolitica
  • grows in refrigerator (like Listeria)
  • farm, wild, pet animals = ZOONOSIS
25
Q

Who gets Yersiniosis in the US?

A

pediatric cases - children in day care centers (young, elderly, IC in other countries)

26
Q

Pathogenesis of Yersiniosis?

A
  • intially facultative intracellular

- extracellular after first round of growth (inhibits phago, cytokines)

27
Q

How does Y. enterolitica cause watery diarrhea?

A

ST-like exotoxin (like ETEC)

28
Q

Where does Yersinia invade?

A

M cells of terminal ileum

29
Q

Different age group manifestations of Yersinia?

A
  • 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
Q

What Yersinia condition mimics appendicitis?

A

mesenteric lymphadenitis + terminal ileitis

31
Q

Where is Y. pseudotuberculosis found?

A

northern Europe and Japan

32
Q

Who gets Y. pseudoTB? Presentation?

A
  • youths 5-20 yo
  • no enterotoxin = no diarrhea
  • more invasive than enterolitica = mesenteric lymphadenitis, enteric fever
33
Q

Morphology of Shigella? Presentation?

A
  • GNR (enterbacteriaceae)
  • ACID resistant
  • febrile non-bloody diarrhea and bacillary dysentery
34
Q

Most virulent species of Shigella? Most common species in US?

A
  • S. dysenteriae

- S. sonnei (least virulent)

35
Q

Reservoir of Shigella? Transmission?

A

Colon of HUMANS - LOW infective dose w/ fecal-oral transmission

36
Q

Pathogenesis of Shigella?

A

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
Q

How does the human immune response enhance Shigella infection?

A
  • 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
Q

Three virulence factors of Shigella?

A
  • enterotoxins (watery diarrhea)
  • Ipa = invasion plasmid antigen
  • Ics = intercellular spread
39
Q

What other organism exhibits Stx?

A

EHEC (requires Stx1 and Stx2 bacteriophages - don’t Tx with anti-motiles or AB)

40
Q

What Shigella organism exhibits Stx?

A

S. dysenteriae type 1 strain - hemorrhagic colitis - HUS (glomerular endo cells - ER disruption due to inhibition of protein synthesis = coagulopathy)

41
Q

What two Shigella organisms can progress from watery diarrhea to dysentery?

A
  • S. flexneri, dysenteriae

- presents as biphasic disease (watery diarrhea - scant stools/abdominal cramps/tenesmus)

42
Q

What protozoan causes ‘flask-like’ ulcers in the colon?

A

Entamoeba histolytica (ulcers with narrow mucosal neck and spreading base in lamina propria)

43
Q

Invasive form of E. histolytica?

A
  • TROPH – VERY invasive - contact lysis invades to muscularis mucosa then invades laterally, DESTROYS PMNs
  • cyst - 90% are asymp and shed cysts
44
Q

Complications of amebic colitics (E. histolytica)?

A
  • 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
Q

What two C. diff toxins cause diarrhea, necrosis, inflammation and lesions covered with pseudomembrane?

A

TcdA and TcdB - work synergystically (A is responsible for diarrhea, B is a potent cytotoxin = nec/inf)

46
Q

C. diff morphology?

A

Gram + anaerobic spore-forming rod (spores are very hard to kill - soap, not germex)

47
Q

Two main AB for C. diff? Newer, more specific drug? Recurrence rate?

A
  • metro and vanc
  • fidaxomicin (not absorbed systemically)
  • 20-30%
48
Q

What % of C. diff cases are CA vs. HA?

A

20% (increasing)

49
Q

What causes tissue injury in C. jejuni infections?

A
  • cytolethal distending toxin (CDT)

- acute inflammatory reaction

50
Q

What is Guillain-Barre syndrome?

A

autoimmune disease of peripheral nervous system (C. jejuni) = flaccid paralysis

51
Q

Occurence and prognosis of GB syndrome?

A
  • 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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