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21 Cards in this Set
- Front
- Back
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When was EColi 1st isolated?
What was the largest outbreak? |
1982: McDonald's contaminated hamburgers
Largest US: Jack in the Box - ground beef (and shortly after that declared an adulterant) Largest ever: Japan, apple jiuce |
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What is the EColi hot spot of the world?
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Bizarrly, Scotland
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What does O157:H7 refer to?
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O antigen = outermembrane lipopolysaccharide
H antigen = flagella (K antigen would be third, for capsule, but this one has no capsule) The numbers refer to which specific antigen # |
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What is the difference between acid tolerance and acid resistance?
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Resistance: increased ability of organism to tolerate exposure to very low pH for short periods of time
Tolerance: down to ~3 Resistant: down to ~2 Salmonella Typhi is tolerant; Ecoli is resistance |
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What does constitutive mean?
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Constitutive means a gene that is always expressed.
Inducable means expression under under certain conditions |
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What implications does being acid resistant have?
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It can survive transit through the gut; it can survive in lower-pH foods (apple cider) and in fermented foods (salami).
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Infectious dose?
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Low because of it's ability to survive gut transit - 1 to 100 CFU/g - one of the lowest
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Symptoms?
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Both GI and systemic:
GI = Hemorrhagic colitis" Bloody diarrhea, cramps, vomiting Systemic: -Hemolytic Uremic Syndrome (kids) -Thrombocytopenic Thrombotic Purpura ("TTP") in ederly |
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Incubation Time?
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1-8 days
(2-5 for Camp; 8 to 72 hours for Salmonellosis) |
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Describe the systemic complication from EColi in children
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Hemolytic Uremic Syndrome:
- Acute kidney faiure - 8% - DUE TO SHIGA TOXINS!!! --> toxico-infection!!!!!!! |
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Why don't adults get Hemolyic Uremic Syndrome?
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We don't have as many GB3 glycolipid receptors --> this is what the Shiga toxin binds to.
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What is the mechanism in which Ecoli infects?
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It's not intercellular like Samonella/Camp:
1. Attach 2. Formation of pedestal (effacement of villi) 3. Toxins through enterocyte and into bloodstream |
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What are the virulence factors of Ecoli?
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Main: Shiga Toxins! Two types: Stx 1 and Stx 2. Very Important.
Other: LEE - proteins involved in attachement and effacment of enterocytes |
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What are the two groups of the Shiga Toxins?
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Stx1 - just like Shigella's
Stx2 - 2, 2c, 2d, 2e ***ENCODED IN DORMANT PHAGES*** |
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What is significant of the Shiga toxin?
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***ENCODED IN DORMANT PHAGES***
--> located on bacteriophages integrated into chromosome of bacteria |
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What are the "subunits" of the Shiga toxin?
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B, A1 and A2
B --> the part the Binds to glycolipid receptor, gb3 A1 --> inhibits cellular protein synthesis and causes cellular death |
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What do Shiga toxins do?
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The inhibit protein synthesis, resulting in cell death
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What is the prevalance of EColi O157:H7 in ground beef?
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0.9%
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What are the steps in the detection of EColi O157:H7
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1. Homogenization
2. Selective enrichment 3. IMS (immunomagnectic separation) 4. Selective Plating - Sorbitol MacConkey agar 5. Confirmation: other immunoassays/PCR |
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KEY: What characteristics are used to detect EColi?
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Antibody affinities - ie w/IMS
Tolerance to certain compounds (used in selective plating/enrichment) |
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How can we differentiate between E.Coli and E.Coli O157:h7?
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- O157 cannot digest sorbitol
- Lack of b-glucuronidase |
