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21 Cards in this Set

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  • Back
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
What is the EColi hot spot of the world?
Bizarrly, Scotland
What does O157:H7 refer to?
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 #
What is the difference between acid tolerance and acid resistance?
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
What does constitutive mean?
Constitutive means a gene that is always expressed.

Inducable means expression under under certain conditions
What implications does being acid resistant have?
It can survive transit through the gut; it can survive in lower-pH foods (apple cider) and in fermented foods (salami).
Infectious dose?
Low because of it's ability to survive gut transit - 1 to 100 CFU/g - one of the lowest
Both GI and systemic:
GI = Hemorrhagic colitis"
Bloody diarrhea, cramps, vomiting
-Hemolytic Uremic Syndrome (kids)
-Thrombocytopenic Thrombotic Purpura ("TTP") in ederly
Incubation Time?
1-8 days
(2-5 for Camp; 8 to 72 hours for Salmonellosis)
Describe the systemic complication from EColi in children
Hemolytic Uremic Syndrome:
- Acute kidney faiure
- 8%
--> toxico-infection!!!!!!!
Why don't adults get Hemolyic Uremic Syndrome?
We don't have as many GB3 glycolipid receptors --> this is what the Shiga toxin binds to.
What is the mechanism in which Ecoli infects?
It's not intercellular like Samonella/Camp:
1. Attach
2. Formation of pedestal (effacement of villi)
3. Toxins through enterocyte and into bloodstream
What are the virulence factors of Ecoli?
Main: Shiga Toxins! Two types: Stx 1 and Stx 2. Very Important.

LEE - proteins involved in attachement and effacment of enterocytes
What are the two groups of the Shiga Toxins?
Stx1 - just like Shigella's
Stx2 - 2, 2c, 2d, 2e

What is significant of the Shiga toxin?
--> located on bacteriophages integrated into chromosome of bacteria
What are the "subunits" of the Shiga toxin?
B, A1 and A2
B --> the part the Binds to glycolipid receptor, gb3
A1 --> inhibits cellular protein synthesis and causes cellular death
What do Shiga toxins do?
The inhibit protein synthesis, resulting in cell death
What is the prevalance of EColi O157:H7 in ground beef?
What are the steps in the detection of EColi O157:H7
1. Homogenization
2. Selective enrichment
3. IMS (immunomagnectic separation)
4. Selective Plating - Sorbitol MacConkey agar
5. Confirmation: other immunoassays/PCR
KEY: What characteristics are used to detect EColi?
Antibody affinities - ie w/IMS
Tolerance to certain compounds (used in selective plating/enrichment)
How can we differentiate between E.Coli and E.Coli O157:h7?
- O157 cannot digest sorbitol
- Lack of b-glucuronidase