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32 Cards in this Set
- Front
- Back
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Define toxin.
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A virulence factor that damages the host. It can directly harm tissue or trigger destructive biological activities.
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What is endotoxin?
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LPS.
(Specifically the Lipid A portion of LPS) |
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What are exotoxins?
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Secreted toxins or toxins that are localized in the cytoplasm and released at cell lysis.
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What are enterotoxins?
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Any toxin that causes diarrhea or vomiting.
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What is an A-B toxin?
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Toxin with separate enzymatic and binding moieties.
A = enzymatic moiety B = binding/translocating moiety |
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Which subunit of the A-B toxin determines the specificity of the toxin?
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The B moiety determines host cell specificity.
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How do A-B toxins cross the membrane?
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Translocation across the cell can be direct or by endocytosis.
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What is a common mechanism of A-B toxins?
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Many A-B toxins ADP-ribosylate a host cell protein.
*Toxic effect depends on the targeted protein. |
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What is the mechanism for membrane-disrupting toxins?
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Act by disorganizing and disrupting the integrity of the host cell membrane.
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What are some examples of membrane-disrupting toxins?
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hemolysins
phospholipases cytotoxins |
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What are the two types of membrane-disrupting toxins?
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1. Pore-forming (non-enzymatic)
cytoplasm leaks out; cell swells and ruptures 2. Phospholipases (enzymatic) removes charged head group from lipid portion of phospholipids = destabilize membrane |
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What are superantigens?
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Toxin that stimulates T cells to make massive amounts of cytokines that can cause fever, shock and possibly death!
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Name 2 bacterial capable of causing toxic shock syndrome.
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Staph aureus
GAS |
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What is one way to protect against diseases whose symptoms result solely from exotoxins?
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Antibodies that bind toxin can provide effective protection against the disease.
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What are toxoids?
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Chemically-denatured or inactive forms of a toxin that are non-toxic but are still capable of eliciting an immune response.
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Name some toxins that are produced in food.
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Staph entrerotoxin A (by S. aureus)
Botulinum toxin (C. botulinum) |
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Are antibiotics useful for toxin food poisoning?
Do the repsonsible bacteria persist? |
NO and NO
Bacteria taken in oral route do not persist. Antibiotics are not useful. The disease is self-limiting. |
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When bacteria colonize mucosal surfaces do they invade underlying tissue?
What is the role of the toxins they produce? |
NO.
Bacteria do not invade underlying tissue or enter the bloodstream. They produce toxins that either act locally or invade the bloodstream to reach target organs. |
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Give an example of bacteria that colonizes mucosal surfaces.
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V. cholerae = adheres to cells in small intestine and synthesizes cholera toxin that acts on mucosal cells.
C. diphtheriae colonizes the throat and makes diphtheria toxin which enters the bloodstream to attach the heart and other organs. |
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What do bacteria growing in wounds or abscesses use to cause local damage to tissue?
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EXOTOXINS.
Used to cause local damage or kill phagocytes in the infected area. *Toxin synthesis aids bacterial growth and facilitates bacterial spread in tissues. |
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What is an example of a toxin that causes gas gangrene in wound colonization?
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alpha toxin produced by Clostridium perfringens
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DESCRIBE THAT TOXIN GAME.
(Bacteria, Type of toxin, Effects) ANTHRAX TOXIN |
B. anthracis
Three separate proteins (EF, LF, PA) EF+PA = edema LF+PA = death |
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Bordatella adenylate cyclase toxin
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Bordatella sp.
A-B increase in target cell cAMP |
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Botulinum toxin
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Clostridium botulinum
A-B Decreases ACh release in PNS = flaccid paralysis |
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Cholera toxin
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Vibrio cholerae
A-5B Activate adenylate cyclase --> secretory diarrhea due to loss of ions |
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Diphtheria toxin
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Corynebacterium diphtheriae
A-B Inhibits protein synthesis by ADP-ribosylation of EF-2 |
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Heat-labile entereotoxins
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E. coli
Similar or identical to cholera toxin |
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Pertussis toxin
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Bordatella pertussis
A-5B Blocks signal transduction mediated by target G proteins |
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Pseudomonas exotoxin A
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Pseudomonas aeruginosa
A-B Similar or identical to diphtheria toxin but has different cell target |
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Shiga toxin
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Shigella dysenteriae
A-5B Inhibition of protein synthesis --> cell death |
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Shiga-like toxins
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Shigella sp. and E. coli
Similar or identical to Shiga toxin |
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Tetanus toxin
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Clostridium tetani
A-B Decrease in NT release from inhibitory neurons = spastic paralysis |
