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Escherichia coli: Overview

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Escherichia coli Overview 

  • Characteristics
    • Gram negative rod
      • motile
    • Indole +
    • Lactose-fermenting
      • Grows on eosin methylene blue (EMB) agar, where lactose fermentation produces a blue-green color
      • Can also ferment glucose
    • Facultative anaerobic
  • Presentation
    • Over 100 strains cause disease
      • Each strain has different virulence factors, which determines disease
    • UTI
      • most common cause of UTI (>80%)
      • Mediated by pili/fimbriae
        • enable adhesion to uroepithelial surface
      • May present as cystitis, urethritis, or pyelonephritis
    • Diarrhea
      • ETEC causes watery diarrhea
      • EHEC causes bloody diarrhea
        • enteroinvasive E. coli (EIEC) strains are rare cause
    • Neonatal Meningitis
      • Mediated by K1 capsule
      • Prevents phagocytosis or complement activation
    • Sepsis
      • Most common cause of gram-negative sepsis
      • Mediated by LPS endotoxin
        • seen in all gram-negative bacteria
    • May be causative agent in a variety of other infections
      • osteomyelitis in sickle cell patients
      • intra-abdominal and lung abscesses
      • orchitis in older men
  • Treatment
    • Generally supportive, as antibiotics are rarely indicated