Lecture 11: E. coli O157 Flashcards
1
Q
E. coli is a Gram-_____ commensal found in _____.
A
- negative
- the intestines of warm-blooded animals
2
Q
What are the 2 types of antigens on E. coli?
A
- O antigen
- 49 different sugars identified
- 187 O antigens defined - H antigen
- 53 H antigens defined
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
4
Q
What are the virulence factors of EHEC?
A
-
Shigella dysenteriae type 1/Shiga toxin 1 and/or Shiga toxin 2
- Cleaves ribosomal RNA and inhibits protein synthesis
- Activates platelets -
LEE pathogenicity island
- Encodes type III secretion system
5
Q
What diseases does E. coli cause?
A
- Hemorrhagic colitis (bloody diarrhea)
- Hemolytic-uremic syndrome (HUS)
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
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
8
Q
What did E. coli O157:H7 evolve from?
A
Most likely evolved from LEE-containing O55 EPEC strains
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