MICR_040913 Ecoli

Question 1

Enteric E. coli serves these purposes:

Answer 1

vitamin K production and protection against other pathogens

Question 2

How do some enteric E. coli become pathogenic?

Answer 2

it acquired virulence genes via horizontal gene transfer

Question 3

What are the diarrhegenic E. coli?

Answer 3

EPEC, EAEC, EIEC, ETEC (think: PATI)

Question 4

What are the shiga-producing E. coli?

Answer 4

EHEC

Question 5

What does EPEC stand for?

Answer 5

enteroPATHOGENIC e. coli

Question 6

What does EAEC stand for?

Answer 6

enteroAGGREGATIVE e. coli

Question 7

What does EIEC stand for?

Answer 7

enteroINVASIVE e. coli

Question 8

What does ETEC stand for?

Answer 8

enteroTOXIGENIC e. coli

Question 9

What does EHEC stand for?

Answer 9

enteroHEMORRHAGIC e. coli

Question 10

What is the main serogroup for EHEC?

Answer 10

O157:H7

Question 11

How is EHEC spread?

Answer 11

via contaminated foods and person:person contact

Question 12

What are the symptoms of EHEC?

Answer 12

abdominal pain, bloody diarrhea, hemolytic uremic syndrome (HUS)

Question 13

What is HUS characterized by?

Answer 13

Hemolytic Uremic Syndrome; due to Shiga-like toxin. Causes hemolytic anemia, low platelet count, and may lead to renal failure

Question 14

T/F EHEC spreads via blood.

Answer 14

False. It does not spread through blood (no bacteremia)

Question 15

What is the LEE pathogenicity island? (7)

Answer 15

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)

Question 16

What is the LEE pathogenicity island ultimately cause?

Answer 16

attachment/effacing lesions “A/E lesions”

Question 17

What is T3SS?

Answer 17

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)

Question 18

What is Intimin/Tir?

Answer 18

recruits host proteins that lead to actin polymerization; ultimately casuses destruction of host cell microvilli (EFFACEMENT)

Question 19

What is Shiga-like toxin? What is it also known as?

Answer 19

aka Verotoxin - affects protein synthesis (A) and cytoskeletal integrity (B). Causes HUS

Question 20

What is hemolysin?

Answer 20

pore-forming protein

Question 21

Why is it that cattle can carry EHEC without getting sick, while humans can’t?

Answer 21

Shiga-toxin B subunit binds to a protein Gb3/CD77 on host cells and this is not present in cattle

Question 22

Which E. coli affects the LARGE intestines?

Answer 22

EHEC, EIEC (think HI - love getting BIG hellos)

Question 23

Which E. coli affects the SMALL intestines?

Answer 23

EPEC, EAEC, ETEC (think: PAT - pattie cakes are small)

Question 24

What E. coli is responsible for the leading cause of death in developing countries?

Answer 24

EPEC

Question 25

EPEC produces these virulence factors:

Answer 25

T3SS, Tir/intimin, bundle forming Pili (BFP)

Question 26

What is Bundle Forming Pili (BFP)?

Answer 26

produced by EPEC, required for localized adherence to epithelial cells and auto-aggregation

Question 27

Which two E. coli strains produce A/E lesions?

Answer 27

EHEC and EPEC (think HP is a big printer company that can cause a lot of damage if it falters)

Question 28

Which E. coli strain causes travelers and infants diarrhea in developing countries?

Answer 28

ETEC

Question 29

ETEC produces these 3 key virulence factors:

Answer 29

1) fimbrae (for colonization), 2) Heat Labile Toxin (increases cAMP), 3) Heat Stable Toxin (increases cGMP)

Question 30

What is heat-labile toxin (LT)? Who produces them?

Answer 30

produced by ETEC; increases cAMP, which increases Cl- secretion, thereby decreasing Na+ uptake. Leads to a net fluid of fluid and electrolytes (watery diarrhea)

Question 31

What is heat-stable toxin (ST)? Who produces them?

Answer 31

produced by ETEC; increases cGMP, which result in similar outcomes to heat-labile toxins

Question 32

What strain of E. coli produce persistent diarrheas that can lead to weight loss?

Answer 32

EAEC (think: the gunner E. coli is type "A" because it must produce the worst diarrheas possible to be successful)

Question 33

Why is it that EAEC causes more persistent diarrheas?

Answer 33

it is more aggressive due to higher affinity colonization factors

Question 34

T/F EHEC, EAEC, and EPEC produce A/E lesions.

Answer 34

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)

Question 35

EAEC produces these 2 key virulence factors:

Answer 35

1) Enteroaggressive stable toxin (EAST), and 2) hemolysin

Question 36

Which E. coli is most common in developing countries?

Answer 36

EIEC (think I for international)

Question 37

What is the pathogenesis of EIEC?

Answer 37

attaches and invades mucosal cells in the colon via non-fimbrial adhesions (highly invasive)

Question 38

What are the symptoms of EIEC?

Answer 38

watery diarrhea with blood and mucous (like Shigella dysentery)

Question 39

What is DAEC?

Answer 39

Diffuse-Adhering E. Coli - causes diarrhea in developing countries, but is poorly characterized

Question 40

What are some diagnostics that you can use to determine different strains of E. coli?

Answer 40

PCR for virulence factors, immunoassays for toxins, serology for surface antigens

Question 41

What is a diagnostic that you can use to determine between commensel and pathogenic E. coli?

Answer 41

Sorbitol MacConkey Agar: pathogenic O157:H7 = no growth/sorbitol (-); COMMENAL = growth/sorbitol (+)