E. Coli

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  1. Organism
    • Pili=virulence factor
    • Type 1 pili bind to D mannose
    • Special pili = CFA (enterocyte), BFP (enterocyte), p (uroepithelium)
  2. Toxins
    • Alpha hemolysin - pore forming toxin
    • Shiga toxin: NOT ADP-R toxin; blocks protein synthesis via 28s ribosomal RNA
    • Labile toxin: A-B ADP-R toxin; stimulate G protein regulated Cl secretion
    • Stable toxin: Increase cGMP which causes a net secretion of fluid
  3. E. Coli UTI
    • Bladder cystits, pyelonephritis
    • Frequency, dysuria
    • Epi: 90% of UTIs; intestinal e. coli
    • Pathogenesis: Sex; bacteria in bladder; P pili able to adhere to epithelial cells more readily; Type 1 pili also attach to uroepithelial pili; urinary catheters, BPH also increase risk
  4. ETEC
    • Epi: traveler's diarrhea; fecal-oral; high infecting dose
    • Pathogenesis: Strains produce LT, ST in small intestine; CFA pili adhere to surface microvilli; ST, LT, and CFA are borne in plasmids
    • Watery diarrhea
  5. EPEC
    • Epi: major source of diarrheal illness in kids
    • Pathogenesis: BFP attach to enterocytes, creaing microcolonies; effacement of microvilli, production of pedestals; A/E lesion, controlled via pathogenicity island, intimin=major attachment protein; E. coli secretion proteins injected into cell, including receptor to intimin; modifications in cytoskeleton
    • Watery diarrhea, non-invasive
  6. EHEC
    • Epi: O157:H7; low infecting dose (100-200); common in industrialized societies, unpasteruized juices/milk
    • Pathogenesis: Stx and A/E lesions; attacks colon; produces HUS via circulating Stx which binds to renal tissues
  7. EIEC
    • Pretty much identical to shigella
    • Kids under 5 in developing countries
    • High infecting dose
  8. Manifestations
    • OIs: dysuria, urinary frequency; fever and flank pain in pyelonephritis
    • Intestinal infections: mild watery diarrhea 2-4 days post infection
    • ETEC, EPEC: remains watery, self limiting
    • EHEC: followed by intense abd pain, bloody diarrhea, no fever, resolution in 3-10 days
    • HUS in 10% of EHEC cases, generally under 10 YO; oliguria, edema and pallor -> hemolytic anemia, renal failure
  9. Diagnosis
    • Isolated in culture
    • O157:H7 fails to ferment sorbitol, confirmed with antisera
  10. Treatment
    • Rehydration
    • EHEC + HUS includes heroic supportive measures i.e. hemodialysis
    • No antimicrobial therapy in EHEC
    • Prevention: TMP-SMX for people at high risk who are immunocompromised
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E. Coli
2011-11-18 03:25:13

E. Coli
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