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Organism
- Pili=virulence factor
- Type 1 pili bind to D mannose
- Special pili = CFA (enterocyte), BFP (enterocyte), p (uroepithelium)
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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
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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
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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
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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
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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
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EIEC
- Pretty much identical to shigella
- Kids under 5 in developing countries
- High infecting dose
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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
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Diagnosis
- Isolated in culture
- O157:H7 fails to ferment sorbitol, confirmed with antisera
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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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