Lecture 11: E. coli O157 Flashcards

1
Q

E. coli is a Gram-_____ commensal found in _____.

A
  1. negative
  2. the intestines of warm-blooded animals
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2
Q

What are the 2 types of antigens on E. coli?

A
  1. O antigen
    - 49 different sugars identified
    - 187 O antigens defined
  2. H antigen
    - 53 H antigens defined
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3
Q

When was E. coli O157:H7 first identified?

A

1982
- Identified as the cause of bloody diarrhea from eating undercooked or raw hamburger meat

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4
Q

What are the virulence factors of EHEC?

A
  1. Shigella dysenteriae type 1/Shiga toxin 1 and/or Shiga toxin 2
    - Cleaves ribosomal RNA and inhibits protein synthesis
    - Activates platelets
  2. LEE pathogenicity island
    - Encodes type III secretion system
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5
Q

What diseases does E. coli cause?

A
  • Hemorrhagic colitis (bloody diarrhea)
  • Hemolytic-uremic syndrome (HUS)
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6
Q

How is E. coli transmitted?

A
  • Ground beef and produce are the most common vehicles for outbreaks
  • Cattle harboring the bacteria do not show disease because they do not have receptors for the toxins
  • Super shedders
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7
Q

What are the drivers of the emergence of E. coli?

A
  • Contamination of food sources: meat slaughtered and processed in large, centralized facilities
  • Pathogen evolution
  • Human behavior: i.e.medium rare vs well done burgers
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8
Q

What did E. coli O157:H7 evolve from?

A

Most likely evolved from LEE-containing O55 EPEC strains

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9
Q

What type of agar is E. coli grown on?

A

Sorbitol MacConkey agar
- Non-sorbitol fermenters (E. coli O157:H7) are colorless
- Sorbitol fermenters (almost all other E. coli) are pink

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