Escherichia coli

Escherichia coli

Updated: 01/30/2024

© Jun Wang, MD, PhD

 

General features

  • Anaerobic G- bacteria, part of normal intestinal flora
  • Most common cause of bacterial diarrhea worldwide
  • Infections due to disruption of the mucosa
  • Most ferment sorbitol (dark pink colonies), except EHEC O157:H7 (white colonies), on MacConkey agar
  • 5 commonly seen diarrhea-associated groups
    • ETEC: Enterotoxigenic E coli, watery diarrhea
    • EIEC: Enteroinvasive E coli, dysentery
    • EHEC: Enterohemorrhagic E coli, hemorrhagic colitis and hemolytic uremic syndrome
    • EPEC: Enteropathogenic E coli, infantile diarrhea
    • EAEC: Enteroaggregative E coli, persistent diarrhea in children and patients infected with HIV

Enterotoxigenic E. coli

  • Major cause of “traveler’s diarrhea” and diarrhea in <3-year-olds in developing countries
  • Bind to small intestine epithelium through colonization factors (CFs)
  • Capsule resistant to phagocytosis
  • Two enterotoxins, detectable by immunoassay, etc
    • LT: heat-labile, activates adenylate cyclase, ↑cAMP, watery diarrhea due to outflow of chloride and water in small intestine
    • ST: heat-stable, diarrhea by stimulating guanylate cyclase
  • Usually 4-14 days after infection
  • Nausea, watery diarrhea, but usually NO vomiting
  • Diagnosis: molecular detection of the genes for LT or ST

Enteroinvasive E. coli

  • Large bowel invasion, similar to shigellosis, including the formation of actin “jet trails”
  • May have fever >101°F and tenesmus
  • Watery diarrhea and excess of leukocytes
  • Approximately 10% cases develop dysentery

Enterohemorrhagic E. coli

  • AKA verotoxin-producing E. coli (VTEC)
  • Most common serotype: O157:H7
  • Transmitted through products contaminated with bovine feces
  • Non-invasive, NO persistent fever
  • Presentations vary, mild diarrhea to hemorrhagic colitis
  • May cause hemolytic uremic syndrome (HUS)
 

Diagnostic approaches

  • Culture: Colorless (white) colonies on sorbitol MacConkey
  • Shiga toxin enzyme immunoassay following culture
  • Molecular testing: Shiga-toxin genes

Managements

  • Reduce risk of HUS
  • Management of fluid loss, pain (NO opioid), HUS, etc
  • Antibiotics NOT recommended: Not needed, or may increase toxin release
  • Antibiotics for severe cases NOT associated with Shiga-toxin producing e coli

 

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