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50 Cards in this Set
- Front
- Back
What are the three main categories of exotoxin?
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cytolytic toxins
neurotoxins enterotoxins |
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What are the two types of toxin?
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endotoxin
exotoxin |
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What do cytolytic toxins do? Give an example.
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attack cell components causing lysis. Staphylococcus aureus hemolysin lyses red blood cells.
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What do neurotoxins do? Give an example.
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interfere with nerve cell function. tetanus toxin.
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What do enterotoxins do? Give an example.
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affect cells lining intestinal tract. eg cholera toxin
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Define exotoxin
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a secreted protein made by Gram-positive and negative bacteria
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Are exotoxins immunogenic?
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yes
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Are exotoxins heat labile (sensitive)?
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yes
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What is the most common endotoxin produced by Gram(-) bacteria?
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LPS
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What is the most common endotoxin produced by Gram(+) bacteria?
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lipoteichoic acid
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Define endotoxin
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non-protein toxin molecule
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Are endotoxins immunogenic?
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not really
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___toxins are proteins excreted by bacteria, and are generally heat labile
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exo
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___toxins are LPS-lipoprotein complexes released on cell lysis as part of the outer membrane of Gram(-) bacteria
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endo
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___toxins are extremely heat stable
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endo
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___toxins act specifically
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exo
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cytotoxins, enterotoxins, and neurotoxins are all ___toxins
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exo
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___toxins are highly toxic, often fatal, whereas ___toxins are weak and rarely fatal
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exo, endo
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___toxins are relatively poor immunogens, whereas ___toxins are very good immunogens and stimulate productionf of neutralizing antibodies
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endo, exo
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toxoids cannot be made from ___toxins
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endo
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treatment of ___toxins with formaldehyde or heat yields a toxoid
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exo
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___toxins do not produce fever in host
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exo
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___toxins often produce fever in host
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endo
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Vibrio cholerae uses a ___toxin to damage its host
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enterotoxin
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Describe the Vibrio cholerae morphology
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motile
Gram(-) curved rod single, polar flagellum |
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Where can Vibrio cholerae survive?
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fresh or brackish water
small intestine of humans |
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What is Vibrio cholerae host range?
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only humans
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Vibrio cholerae strains are serotyped based on thier ___ antigen
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LPS O antigen
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Two serogroups known as __ and __ are responsible for cholera outbreaks
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O1 and O139
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Vibrio cholerae has three major virulence factors. What are they?
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cholera toxin
Tcp pili flagellum |
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How is cholera spread?
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fecal contamination of water and food
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Cholera occurs usually in ___
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epidemics
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What are the cholera symptoms?
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Massive diarrhea (rice water stool containing 10^8 vibrios), resulting in electrolye loss, dehydration, anuria, acidosis, and shock
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Describe the structure of cholera toxin
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multimeric protein complex composed of five identical binding (B) subunits and an A (enzymatic) subunit
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one of the B subunits of CT binds to a ___ receptor, causing the ___ to be cleaved
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glycolipid. A subunit
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After cleavage, the A1 portion of the A subunit enters into ___
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the cytosol of the intestinal epithelial cell
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___ activates the host cell's adenylate cyclase enzyme, which does what?
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A1. It converts ATP into cAMP.
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What does cAMP do?
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stimulates the secretion of large amounts of Cl ions from cell into lumen of intestine
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The loss of chlorine ions from intestinal epithelial cells results in what?
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An electrical gradient that pulls sodium, potassium and other ions from cells, causing new electrolyes to be pulled from blood
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What is the overall effect of cholera toxin on cells?
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It turns them into pumps for water and electrolytes
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How is cholera spread?
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fecal-oral route
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Is Vibrio cholerae acid sensitive?
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yes
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Why is a large dose of Vibrio cholerae required to produce disease?
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A lot of the Vibrio cholerae die because of gastric acidity
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Vibrio cholerae are well adapted to survive in what part of the GI tract?
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small intestine
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How does Vibrio cholerae withstant propulsive gut activity?
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by swimming
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Vibrio cholerae lacking TCP pili are still pathogenic (T/F)
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F
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What does Vibrio cholerae TCP pili do?
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causes bacteria to aggregate
facilitates adherence to the intestinal mucosa |
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What is the treatment for cholera?
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rapid replacement of fluids and electrolytes through Gatorade-like solution
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Describe the current cholera vaccine. What serogroups is it effective against?
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CVD 103-HgR is an oral, live, attenuated cholera vaccine effective only against O1 serogroup
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Recurrent infections of cholera are rare (T/F). Why?
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T. Antibodies are developed during first infection.
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