E Coli

Question 1

what are some advantages of having E Coli in the gut?

Answer 1

produces vitamin K

protects against other pathogens

Question 2

why are some E Coli such a problem?

Answer 2

they acquire virulence genes from salmonella and shingella

Question 3

what are the two major categories of pathogenic E coli?

Answer 3

shiga toxin producing

diarrheagenic

Question 4

what disease does E coli cause?

Answer 4

GI tract- kills w/ diarrhea

Question 5

enterohemorrhagic E coli source of infection

Answer 5

STEC

undercooked food (meat, zoo)
person to person
zoos

more common in summer

Question 6

STEC infectious dose

Answer 6

very low

Question 7

STEC symptoms

Answer 7

abdominal pain
bloody diarrhea
hemolytic uremic syndrome
acute renal failure (most common cause of kidney failure in kids)

bacteremia does not occur- stays in gut

Question 8

STEC incubation period

Answer 8

3 days

Question 9

virulence determinants in STEC

Answer 9

pillus-mediated attachment

LEE island- contains T3SS, Tir, and Intimin

proteins that recruit host actin and cause altered morphology

Shiga-like toxin

Hemolysin

Capsule/LPS/nutrient acquisitions

Question 10

what does the E coli common pillus do?

Answer 10

provide relatively weak attachment

Question 11

T3SS

Answer 11

formation of a “needle” that causes lesions by piercing both the bacteria and host membrane

Question 12

Tir

Answer 12

gene delivered to epithelial cells to allow for E coli attachment

Question 13

Intimin

Answer 13

Tir binding protein on surface of E coli

Question 14

Shiga-like toxin

Answer 14

disrupts eukaryotic protein synthesis and it cytotoxic. does this by cleaving RNA and impacting cytoskeleton

causes bloody diarrhea

attacks kidney, CNS
causes vascular damage
induces HUS
causes renal failure

Question 15

hemolysin

Answer 15

pore forming protein that inserts into how cells membrane

associated with meningitis

found on its own plasmid

Question 16

enteropathogenic E Coli

Answer 16

diarrheagenic EPEC - leading cause of childhood diarrhea in developing countries

caused by person to person contact

localized adherence by bundle forming pilli- multiple e coli attach to same cell

no toxins

Question 17

enterotoxigenic e coli

Answer 17

ETEC- diarrheagenic

“Travelers diarrhea”

fimbrae adhere to enterocytes in small intesting

Toxins:

heat-labile toxin- upregulate adenylate cyclase. causes Cl secretion and impaired Na uptake, causing watery stool

heat stable toxin- alters cGMP w/ similar outcomes to heat-labile toxins

Question 18

enteroaggregative E coli

Answer 18

EAEC- diarrheagenic

childhood diarrhea in developing world- causes persistent diarrhea

more aggressive than EPEC b/c more aggressive adherence

Toxins: EAST (heat stable-like), PET, hemolysin

Question 19

enteroinvasive E coli

Answer 19

EIEC

less common in industrialized nations

attachs w/ non-fimbrial adhesins in colon

invades mucosal cells but does not become systemic

causes bloody diarrhea and mucus in stool

invasion genes similar to shingella

no ST or LT toxins

Question 20

diagnostic tools for e coli

Answer 20

e coli is Lac+ = can be detecteed via EMB or MacConkey agar (shingella and salmonella are Lac-)

O157:H7

• cannot grow on sorbitol (can grow on MacConkey)
• serology agglutination tests

Immunoassay for shiga-like toxin

PCR/DNA probe for virulence genes

Tissue culture

Strain typing

Question 21

diffusely adhering e coli

Answer 21

common in children in developing countries

Question 22

CDC recommends looking for Shiga-toxins in diagnostics

Answer 22

ok

Question 23

EHEC treatment

Answer 23

supportive care only

Question 24

ETEC treatment

Answer 24

loperamide, azithromycin

Question 25

EPEC treatment

Answer 25

antibiotics using susceptibilty testing for severe cases

Question 26

EAEC treatment

Answer 26

fluoroquinolones