E.Coli Flashcards
e.coli is what type of bacteria
enteric!
e.coli are part of
normal microflora (esp in newborns)
e.coli synthesizes
vitamin K
two types of strains of e.coli
shiga toxin producing (STEC)
diarrheagenic (the rest)
different enteropathogenic e.coli have different
virulence factors
main serogroup
O157:H7
other EHEC (enterohemorrhagic) serogroups
O111, O26, O157: H-
sources of infection
Food
Petting zoos
person to person contact
very low infectious dose
clinical syndrome of EHEC
abdominal pain
bloody diarrhea
hemolytic uremic syndrome
acute renal failure in severe cases
most cells of EHEC
remain extracellular ((some can invade mucosal) but does NOT become systemic
why does hemolytic uremia syndrome happen in HUS?
destruction of red blood cells and damage to lining of blood vessel walls
EHEC has what type of attachment
pili-mediated
T3SS induces
formation of attaching/effacing lesions
genes for T3SS are encoded…
LEE pathogenicity island (locus for enterocyte effacement)
encodes intimin and tir
Tir
t3SS secreted bacterial protein that is delivered to surface of epithelial cells to allow for e.coli attachment
intimin
Tir binding protein on surface of e.coli
other e.coli proteins..
recruit host cell actin–>causes altered morphology–>impacts signal transduction pathways in the host cell to form A/E lesions
Lesion can lead to
effacement (destruction of host cell microvilli)
Hemolytic uremia syndrome is due to activity of
shiga-like toxin
why are cow not suceptible to EHEC?
SHiga toxin binds Gb3/CD77 host glycolipid by the B subunit and this receptor is not present in cattle
hemolysin
pore forming protein that inserts into host cell membranes
common in the E.coli strains that cause meningitis
encoded by a plasmid
E.coli also have.. (3 things)
capsule (k-antigen)
LPS
nutrient aqusitions pathways
EPEC
diarrheagenic e.coli
EPEC is transmitted via
person to person contact
how is EPEC transmitted?
person to person contact
what does EPEC do?
forms A/E lesions
toxins in EPEC
not detected in stool of infected human volunteers
ETEC
enterotoxigenic E. coli
where/when is ETEC an issue?
traveler’s diarrhea
problematic in infants in the developing world
how does ETEC work?
fimbriae adhere to specific receptors on enterocytes in small intestine
Heat-labile toxin
targets adenylate cyclase –>increase cAMP–>excess chloride ion secretion–>blocked Na ion uptake
**net loss of fluid and electrolytes into lumen of gut and watery diarrhea
Heat stable toxin
alters cGMP levels–>net loss of fluid and electrolytes into lumen of gut and watery diarrhea
EAEC
enteroaggregative ecoli
EAEC logistics
childhood diarrhea similar to EPEC, common in developing countries
EAEC compared to EPEC
somewhat more aggressive due to different colonization factors that lead to more aggressive epithelial cell attachment
EAEC does not have
A/E lesions –>non invasive
what does EAEC contain?
heat stable-like toxin (EAST)
poorly characterized plasmid encoded toxin (PET)
hemolysin
EIEC
enteroinvasive
how does EIEC path work?
attaches to cells within the colon by non fimbrial adhesions–> invades mucosal cells–> multiplies within these cells
does not become systemic
clincal syndrome of EIEC
water diarrhea that can contan blood and mucous
genes for EIEC
genes for invasion, replication within host, and survival are encoded by a plasmid
what is different about EIEC?
they do NOT produce shiga toxin or LT
DAEC
diffuse adhereing ecoli
what does DAEC cause?
diarrhea in older children in many developing countries
E.coli and lac
lac+
O157:H7 and sorbital
sorbital negative, but other commensal E. coli strains are sorbitol-positive
prevention e.coli
grass fed cattle carry a lot, so we need to reduce carriage (hay feeding and probiotics)
hygene
