E Coli Flashcards
(26 cards)
what are some advantages of having E Coli in the gut?
produces vitamin K
protects against other pathogens
why are some E Coli such a problem?
they acquire virulence genes from salmonella and shingella
what are the two major categories of pathogenic E coli?
shiga toxin producing
diarrheagenic
what disease does E coli cause?
GI tract- kills w/ diarrhea
enterohemorrhagic E coli source of infection
STEC
undercooked food (meat, zoo)
person to person
zoos
more common in summer
STEC infectious dose
very low
STEC symptoms
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
STEC incubation period
3 days
virulence determinants in STEC
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
what does the E coli common pillus do?
provide relatively weak attachment
T3SS
formation of a “needle” that causes lesions by piercing both the bacteria and host membrane
Tir
gene delivered to epithelial cells to allow for E coli attachment
Intimin
Tir binding protein on surface of E coli
Shiga-like toxin
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
hemolysin
pore forming protein that inserts into how cells membrane
associated with meningitis
found on its own plasmid
enteropathogenic E Coli
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
enterotoxigenic e coli
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
enteroaggregative E coli
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
enteroinvasive E coli
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
diagnostic tools for e coli
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
diffusely adhering e coli
common in children in developing countries
CDC recommends looking for Shiga-toxins in diagnostics
ok
EHEC treatment
supportive care only
ETEC treatment
loperamide, azithromycin
