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42 Cards in this Set
- Front
- Back
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What is EPEC associated with?
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Infant diarrhea in developing countries
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What is the major histopathology seen in EPEC?
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Attaching and effacing lesions
(A/E) |
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What are the steps in creating A/E lesions?
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1. Effacement of microvilli
2. Intimate attachment of bug 3. Cytoskeletal changes 4. Pedestal like structures and actin polymerization |
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What is the diagnostic test for EPEC?
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FAS - flouresc actin staining
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What other strain of Ecoli shows similar A/E lesions?
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EHEC
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In what age group is EPEC mostly seen?
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Infants < 2yr old in developing countries
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What is the infectious dose of EPEC?
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high
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Where are outbreaks of EPEC most often seen in developed countries?
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Day cares
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Is EPEC extra or intracellular?
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Extracellular
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What is the 3 step model of EPEC pathogenesis?
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1. Local adherence
2. Signal transduction 3. Intimate adherence |
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What is local adherence of EPEC to intestinal cells mediated by?
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Plasmid Encoded Bundle Forming Pili (bfp)
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What does Signal transduction induced by EPEC bfps binding enterocytes result in?
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-Increased tight junction permeability
-Chemotaxis -Inflammation |
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What is intimate adherence of EPEC mediated by?
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Intimin on the bug's outer membrane
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What does the EPEC's Intimin bind to?
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Tir on the host enterocyte
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Is Tir a host protein?
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NO - it is encoded by EPEC!
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How does the Tir protein get expressed on a host cell, if it is encoded for by the EPEC?
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By a type III secretion system
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What is a way to differentiate EPEC infections from EHEC infections?
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Tir is phosphorylated in eukaryotic intestinal cells in EPEC, not in EHEC.
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What are 2 ways to identify EPEC strains based on genes?
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-EAF plasmid, LEE positive
-Shiga toxin negative |
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What does the EAF plasmid encode?
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The type III secretion system
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What is the easiest way to diagnose EHEC?
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By looking at the stools - diarrhea will be grossly bloody
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Is EHEC usually accompanied by a fever?
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No
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What mode of transmission is Hemorrhagic colitis associated with?
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Eating undercooked hamburgers
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What is the serotype of EHEC that causes hemorrhagic colitis?
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0157 H7
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What is the severe sequelae that can result from hemorrhagic colitis?
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HUS
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What are the 3 symptoms of HUS?
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-Renal failure
-Thrombocytopenia -Microangiopathic hemolytic anemia |
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What can the cytotoxicity associated with EHEC strains be neutralized with?
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Antibody to shiga toxin!
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What are the 3 defining characteristics of EHEC?
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1. Produces Stx
2. A/E lesions in tissue culture 3. Possesses a 60-MDa plasmid |
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What are the 4 histopathologic manifestations of EHEC?
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1. Hemorrhage and edema of lamina propria
2. Thumbprinting pattern on barium enema 3. Focal necrosis/infiltration of PMNs 4. A/E lesions early |
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What is the basic structure of the shiga toxins?
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AB5
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What is the activity of the A subunit?
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RNA N-glycosidase
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What is the cellular receptor for Stx on host cells?
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Gb3 (globotriaosylceramide)
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What is achieved by the RNA N-glycosidase activity of the shigatoxin?
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Removal of a single adenine residue from the 28S rRNA of eukaryotic ribosomes.
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What is the reservoir of EHEC?
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Cattle
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What is the infectious dose of EHEC?
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low
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What are 3 ways of transmitting EHEC?
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-contaminated food
-contaminated water -person to person |
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What strain of Ecoli is lactose negative?
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EIEC - invasive
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What does pathogenesis of EIEC resemble?
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Shigella - adhere, get into cell, break out can't stand vacuole, make actin tail, infect adjacent cells.
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What are the 5 steps in EIEC invasion?
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1. Epithelial cell penetration
2. Lysis of endosome 3. Intracellular multiplication 4. Movement thru cytoplasm 5. Invasion of adjacent cells |
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What is elicited by invasion of EIEC?
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A strong inflammatory response that causes ULCERATION of the colon mucosa
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What is the clinical picture of EIEC?
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-Water diarrhea initially
-Occasionally Scanty, bloody, mucoidy stools follow |
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What is EIEC generally mistaken for?
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Shigella
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How is EIEC identified?
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Based on its biochemical profile
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