Colon non tumor
Infectious colitis (specific microorganisms)
Escherichia coli

Author: Nalini Bansal, M.D., D.N.B., PDCC, MNAMS (see Authors page)
Editorial Board Member Review: Raul S. Gonzalez, M.D.

Revised: 27 June 2017, last major update May 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed search: Escherichia coli [title] colon NOT tumor

Related topics: Enteroaggregative, Enterohemorrhagic, Enteroinvasive, Enteropathogenic, Enterotoxigenic
Cite this page: Escherichia coli. PathologyOutlines.com website. http://pathologyoutlines.com/topic/colonecoli.html. Accessed November 17th, 2017.
Definition / general
Essential features
  • Most cases cause self limiting disease
  • Treatment is supportive
Terminology
  • Enterohemorrhagic E. coli, verocytotoxin producing E. coli, Shigatoxigenic Escherichia coli (STEC)
ICD-10 coding
  • B96.20 Infection due to Escherichia coli
Epidemiology
  • In USA most outbreaks have been reported in Minnesota, followed by Washington
  • Route of transmission is foodborne; mainly by undercooked ground beef in EHEC
 (Emerg Infect Dis 2005;11:603
  • ETEC organisms are the principal cause of traveler's diarrhea and spread via contaminated food or water
  • EIEC / EAEC organisms are bacteriologically similar to Shigella and are transmitted via food, water or by person to person contact
Sites
  • Colon and rectum

Pathophysiology
  • Depends on the strain of pathogenic E. coli
    1. Enteroaggregative E. coli
      • EAEC adhere to epithelial cells
      • EAEC attach to enterocytes via adherence fimbriae and are aided by dispersin, a bacterial surface protein that neutralizes the negative surface charge of lipopolysaccharide
      • They also produce enterotoxins similar to Shigella enterotoxin and ETEC ST toxin
    2. Enterohemorrhagic E. coli
      • EHEC are classified as E. coli O157:H7 and non O157:H7 serotypes
      • Both serotypes produce Shiga-like toxins
      • Hemolytic uremic syndrome (HUS) is caused by Shiga-like toxin which is absorbed by inflamed gastrointestinal mucosa into the circulation, where it alters endothelial cell function leading to platelet activation and aggregation
      • Children and the elderly are at highest risk
    3. Enteroinvasive E. coli
      • EIEC do not produce toxins, they invade epithelial cells and cause acute self limited colitis
    4. Enterotoxigenic E. coli
      • ETEC produce heat labile toxin (LT) and heat stable toxin (ST)
      • Both induce chloride and water secretion while inhibiting intestinal fluid absorption
      • The LT toxin activates adenylate cyclase and stimulates chloride secretion and simultaneously inhibits absorption
      • ST toxins bind to guanylate cyclase and stimulate chloride secretion
Etiology
  • Contaminated food and water
Clinical features
  • EAEC organisms cause nonbloody diarrhea that may be prolonged in AIDS patients
  • EHEC cause symptoms similar to S. dysenteriae
    • They cause large outbreaks of bloody diarrhea and HUS
    • HUS includes microangiopathic hemolytic anemia and thrombocytopenia but no neurologic symptoms and no acute renal failure
  • EIEC is common among young children in developing countries
    • Also causes traveler's diarrhea and diarrhea in both children and adults
  • ETEC causes traveler’s diarrhea commonly in underdeveloped regions and children younger than 2 years of age are particularly susceptible
    • Secretory, noninflammatory diarrhea, vomiting, dehydration and in severe cases, shock
  • Diagnosis
    • Typically made by clinical findings and history of ingestion of contaminated food like undercooked meat
    Laboratory
    • A stool culture on sorbitol MacConkey agar (SMAC) or the variant cefixime potassium tellurite sorbitol MacConkey agar (CT-SMAC)
    • Colonies appear clear on SMAC due to their inability to ferment sorbitol, while sorbitol fermenting colonies of E. coli serotypes appear red
    • E. coli DNA extraction method: DNA probes plus PCR techniques for detecting verocytotoxin
    Radiology description
    • CT usually preferred modality for radiological assessment (AJR Am J Roentgenol 2001;177:619)
    • Shows severe diffuse colonic wall thickening, often with a target sign and pericolic stranding
    • Involvement of bowel can be segmental or diffuse
    Radiology images

    Images hosted on other servers:

    CT scan showing
    thickened colon
    with target sign
    (solid arrows)

           

    CECT showing pancolitis with
    thickened colon with target sign
    (Solid arrows); Open arrows pericolic
    inflammation and stranding

    Prognostic factors
    • Disease is usually self limiting, and patients recover on supportive therapy
    Treatment
    Gross description
    • EHEC: colonic mucosa is edematous and erythematous with multiple erosions
    • Erosion may show adherent blood clots
    Microscopic (histologic) description
    • EAEC, EIEC, ETEC:
      • No significant microscopic changes
    • EHEC:
      • Foci of epithelial cell damage / necrosis with pyknotic nuclei, vacuolated cytoplasm 

      • Areas of hemorrhage within lamina propria 

      • Gram negative bacterial rods could be found on the apical surfaces of mucosal epithelial cells
    Microscopic (histologic) images
    Images hosted on other servers:

    Various images

    A: Epithelial damage with hemorrhage
    B: Leukocyte infiltration
    C: Epithelial damage with no significant inflammation
    D: TEM showing pyknotic nuclei, damaged membranes and cytoplasmic vacuolization

    Positive stains
    • E. coli are gram negative bacilli
    Electron microscopy description
    • TEM, in cases of EHEC, shows pyknotic nuclei, damaged membranes and cytoplasmic vacuolization of colonic epithelial cells
    Differential diagnosis
    • Ischemic Colitis: negative culture for E. coli; no significant history 

    • Other infective colitis: negative culture for E. coli
    Additional references
    Board review question #1
    Different pathogenic strains of E. coli are:

    1. Enteroaggregative E. coli
    2. Enterohemorrhagic E. coli
    3. Enteroinvasive E. coli
    4. Enterotoxigenic E. coli
    5. All of the above
    Board review answer #1
    E. All of the above
    Board review question #2
    Traveler’s diarrhea is mostly caused by which strain?

    1. Enteroaggregative E. coli
    2. Enterohemorrhagic E. coli
    3. Enteroinvasive E. coli
    4. Enterotoxigenic E. coli
    Board review answer #2
    D. Enterotoxigenic E. coli
    Board review question #3
    Which E. coli strain cause symptoms similar to S. dysenteriae?

    1. Enteroaggregative E. coli
    2. Enterohemorrhagic E. coli
    3. Enteroinvasive E. coli
    4. Enterotoxigenic E. coli
    Board review answer #3
    B. Enterohemorrhagic E. coli
    Board review question #4
    Hemolytic uremic syndrome (HUS) is caused by which E. coli strain?

    1. Enteroaggregative E. coli
    2. Enterohemorrhagic E. coli O157:H7
    3. Enteroinvasive E. coli
    4. Enterotoxigenic E. coli
    Board review answer #4
    B. Enterohemorrhagic serotype E. coli O157:H7
    Board review question #5
    What are clinical features of HUS?

    1. Microangiopathic hemolytic anemia
    2. Occurs usually in children
    3. Thrombocytopenia
    4. All of the above
    Board review answer #5
    D. All of the above