MICR_040913 Ecoli Flashcards
Enteric E. coli serves these purposes:
vitamin K production and protection against other pathogens
How do some enteric E. coli become pathogenic?
it acquired virulence genes via horizontal gene transfer
What are the diarrhegenic E. coli?
EPEC, EAEC, EIEC, ETEC (think: PATI)
What are the shiga-producing E. coli?
EHEC
What does EPEC stand for?
enteroPATHOGENIC e. coli
What does EAEC stand for?
enteroAGGREGATIVE e. coli
What does EIEC stand for?
enteroINVASIVE e. coli
What does ETEC stand for?
enteroTOXIGENIC e. coli
What does EHEC stand for?
enteroHEMORRHAGIC e. coli
What is the main serogroup for EHEC?
O157:H7
How is EHEC spread?
via contaminated foods and person:person contact
What are the symptoms of EHEC?
abdominal pain, bloody diarrhea, hemolytic uremic syndrome (HUS)
What is HUS characterized by?
Hemolytic Uremic Syndrome; due to Shiga-like toxin. Causes hemolytic anemia, low platelet count, and may lead to renal failure
T/F EHEC spreads via blood.
False. It does not spread through blood (no bacteremia)
What is the LEE pathogenicity island? (7)
genes that cause attachment/effacing lesions: 1) T3SS, 2) Intimin/Tir, 3) Shiga like toxin, 4) hemolysin, 5) capsule (K antigen), 6) LPS (endotoxin), and 7) nutrient acquisition pathways (ie siderophores)
What is the LEE pathogenicity island ultimately cause?
attachment/effacing lesions “A/E lesions”
What is T3SS?
system that enhances host cell attachment via EspA and EspB/D. (EspA = “needle” for espB/D to pass, ESPB/D = forms a pore on host membrane)
What is Intimin/Tir?
recruits host proteins that lead to actin polymerization; ultimately casuses destruction of host cell microvilli (EFFACEMENT)
What is Shiga-like toxin? What is it also known as?
aka Verotoxin - affects protein synthesis (A) and cytoskeletal integrity (B). Causes HUS
What is hemolysin?
pore-forming protein
Why is it that cattle can carry EHEC without getting sick, while humans can’t?
Shiga-toxin B subunit binds to a protein Gb3/CD77 on host cells and this is not present in cattle
Which E. coli affects the LARGE intestines?
EHEC, EIEC (think HI - love getting BIG hellos)
Which E. coli affects the SMALL intestines?
EPEC, EAEC, ETEC (think: PAT - pattie cakes are small)
What E. coli is responsible for the leading cause of death in developing countries?
EPEC
EPEC produces these virulence factors:
T3SS, Tir/intimin, bundle forming Pili (BFP)
What is Bundle Forming Pili (BFP)?
produced by EPEC, required for localized adherence to epithelial cells and auto-aggregation
Which two E. coli strains produce A/E lesions?
EHEC and EPEC (think HP is a big printer company that can cause a lot of damage if it falters)
Which E. coli strain causes travelers and infants diarrhea in developing countries?
ETEC
ETEC produces these 3 key virulence factors:
1) fimbrae (for colonization), 2) Heat Labile Toxin (increases cAMP), 3) Heat Stable Toxin (increases cGMP)
What is heat-labile toxin (LT)? Who produces them?
produced by ETEC; increases cAMP, which increases Cl- secretion, thereby decreasing Na+ uptake. Leads to a net fluid of fluid and electrolytes (watery diarrhea)
What is heat-stable toxin (ST)? Who produces them?
produced by ETEC; increases cGMP, which result in similar outcomes to heat-labile toxins
What strain of E. coli produce persistent diarrheas that can lead to weight loss?
EAEC (think: the gunner E. coli is type “A” because it must produce the worst diarrheas possible to be successful)
Why is it that EAEC causes more persistent diarrheas?
it is more aggressive due to higher affinity colonization factors
T/F EHEC, EAEC, and EPEC produce A/E lesions.
False! Only EHEC and EPEC produces A/E lesions (think HP is a big printer company that can cause a lot of damage if it falters)
EAEC produces these 2 key virulence factors:
1) Enteroaggressive stable toxin (EAST), and 2) hemolysin
Which E. coli is most common in developing countries?
EIEC (think I for international)
What is the pathogenesis of EIEC?
attaches and invades mucosal cells in the colon via non-fimbrial adhesions (highly invasive)
What are the symptoms of EIEC?
watery diarrhea with blood and mucous (like Shigella dysentery)
What is DAEC?
Diffuse-Adhering E. Coli - causes diarrhea in developing countries, but is poorly characterized
What are some diagnostics that you can use to determine different strains of E. coli?
PCR for virulence factors, immunoassays for toxins, serology for surface antigens
What is a diagnostic that you can use to determine between commensel and pathogenic E. coli?
Sorbitol MacConkey Agar: pathogenic O157:H7 = no growth/sorbitol (-); COMMENAL = growth/sorbitol (+)
