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EPEC
Enteropathogenic
Infant diarrhea
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ETEC
Enterotoxigenic
- Traveler's diarrhea
- Infant diarrhea
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EHEC
Enterohemorrhagic
- Bloody diarrhea
- Hemorrhagic colitis
- HUS
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EIEC
Enteroinvasive
Bacillary Dysentary
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EAEC
Enteroaggregative
- Infant Diarrhea
- Traveler's Diarrhea
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EPEC attaches to epithelial cells of __________
small intestine
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Major histological characteristic of EPEC is?
Effacement (destruction) of microvilli in small intestine (attachment/effacement [A/E] pathology)
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Which strand of E. coli causes A/E pathology?
EPEC, EHEC
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E. coli genes involved in A/E are encoded on a ______
pathogenicity island
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What type of pili do EPEC have? What type of attachment is this?
Bfp pili, allow for loose attachment
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What type of secretion system does EPEC use to secrete Tir?
Type III Secretion System
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Type III Secretion System of EPEC secretes?
Tir (Translocated intimin receptor)
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What type of E. coli secretes Tir and what does this do?
- EPEC secretes Tir (translocated intimin receptor).
- Tir goes into host cell dimerizes and then localized to the membrane where it serves as a receptor for intimin (which is on E. coli surface). This is a TIGHT attachment!
- Then this causes a cascade which causes rearrangment of host actin and loss of microvilli.
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What two proteins produced by EPEC mediate host cell apoptosis?
Tir and ESPF
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Main cause of traveler's diarrhea?
ETEC
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How do you acquire ETEC?
Consumption of fecally contaminated water or food
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Name the 3 virulence factors of ETEC.
- CFA: Colonization factor antigens
- ST: Heat-stable toxins
- LT: Heat-labile enterotoxins
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Unlike EPEC, ETEC has _______
No inflammation or histological changes to the mucosa
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ETEC presents clinically with?
Watery diarrhea
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ETEC: Heat-Labile Toxin (LT-1)
1) What type of toxin?
2) Endocytosed to?
3) Which subunit detaches? Where does it go?
4) What does it do?
5) Phosphorylated GS regulates? Leads to?
6) _____ secretion increases and ____ absorption decreases.
7) Result?
- 1) A-B toxin (1A, 5B subunits)
- A= active
- B= binding
- 2) ER/ GA
- 3) A subunit detaches and leaves the compartment.
- 4) Transfers the ADP-ribose from NAD to GDP subunit of Gs.
- 5) Adenylyl cyclase --> Increase in intracellular cAMP.
- 6) Chloride increases, sodium decreases
- 7) Results in watery diarrhea
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What toxin from what strain of E. coli is similar to cholera toxin in that they both have the same # of subunits?
LT-1 from ETEC (1A, 5B subunits)
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What ETEC virulence factor allows attachment of bacteria to epithelial cells?
CFA (colonization factor antigens)
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ETEC: Heat-Stable toxin (STa)
1) What type of toxin?
2) Secreted and binds to?
3) Activated guanylyl cyclase catalyzes _____ to _____.
4) Stimulates secretion of _____
5) Result
- 1) Small monomeric toxin
- 2) Binds to host guanylyl cyclase
- 3) GTP --> cGMP
- 4) chloride
- 5) watery diarrhea
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Labile in the Air, Stable on the Ground
- ETEC
- Heat labile toxin = Adenylyl Cyclase
- Heat stable toxin = Guanylyl Cyclase
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ETEC: Heat labile or heat stable?
1) Which one leads to increased chloride secretion and decreased sodium absorption?
2) Which one leads to increased chloride secretion?
- 1) Heat-labile toxin (LT-1)
- 2) Heat-stable toxin (STa)
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ETEC:
Chloride secretion is done by the ?
CFTR
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E. coli 0157:H7 is what type of E. coli?
EHEC
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What virotype of E. coli is the most common to produce diseases in developed countries?
EHEC (0157:H7)
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HUS is what type of E. coli virotype?
EHEC
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Name the main toxin of EHEC.
Shiga (Stx-1, Stx-2, or both)
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What EHEC toxin is identical to the Shigella dysenteriae toxin? How much in common is the other one?
Stx-1 is identical. Stx-2 is 60% homologous.
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How are Stx-1 & Stx-2 viruses acquired by EHEC?
Bacteriophages
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Describe the structure of Stx-1 and Stx-2 toxins on EHEC.
Both are A-B toxins (1A, 5B)
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What two types of E. coli have a Type III Secretion System?
EPEC, EHEC
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Describe pathogenesis of EHEC.
1) Express ____ secretion system, ____, and _____ for binding
2) Secretes ___which crosses the epithelium and is carried by the blood
3) The _____ subunits of Stx bind to host__________, also known as____.
4) After endocytosis of Stx, the ____ subunit leaves the compartment and binds to/ cleaves the _____ of the ____ subunit.
5) This disrupts ______
6) Endothelial cell death occurs and can lead to coagulation in the microvasculature, platelet consumption, red cell fragmentation, decreased glomerular filtration, and renal failure
- 1) Type III SS, Tir, intimin (A/E phenotype on epi.)
- 2) Stx
- 3) B subunit, Globotriaosylceramide, GB3
- 4) A subunit, 28S rRNA, 60S
- 5) Protein synthesis
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Which E. coli is rare in the US and uncommon in developing countries?
EIEC
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Name the 3 pathogenic strains of EIEC.
Invade and destroy colonic epithelium
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O124, O143, O164 are virulent strains of what E. coli virotype? They are very closely related to?
- EIEC
- Very closely related to Shigella
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EIEC's strains are characterized by invasion and destruction of what?
colonic epithelium
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EIEC causes dysentary. What does that consist of?
Fever, abdominal cramps, blood and pus in stool
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EIEC becomes internalized within a phagocytic-like vacuole, escapes into the cytoplasm, replicates, and spreads to adjacent cells via ______
host actin tails
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Which E. coli virotype spreads to other cells via host actin tails?
EIEC
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What carries the genes for EIEC's invation into epithelial cells?
Large plasmid (invasion plasmid antigens- ipa)
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Causes diarrhea in adults in both developing and developed countries.
Chronic diarrhea in children in developing countries is associated with____
EAEC
Growth retardation
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EAEC auto-agglutinate into a "stacked-brick" arrangement mediated by__________
bundle-forming fimbriae (aggregative adherence fimbriae I and II)
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EAEC stimulates _______, which traps the bacteria ina biofilm on the epithelium of the small intestine.
mucous secretion
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Which E. coli virotype stimulates mucus secretion?
EAEC
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How does hemorrhage occur in EAEC?
Microvilli become shortened, mononuclear cells infiltrate, and hemorrhage can occur
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Characterized by a uniform but diffuse attachment of the bacteria to the epithelium; mediated by a Dr-like fimbrial adhesion.
Associated with Brazilian children
DAEC
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