6. Exotoxins and their classifcation according to their mechanism of action and a site of effect

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excalibolg
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6. Exotoxins and their classifcation according to their mechanism of action and a site of effect
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2015-10-07 13:36:45
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microbiology
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I. General Microbiology
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  1. Exotoxins - Overview
    • - are proteins released from G -/+
    • - Neurotoxins
    • - Enterotoxins
    • - Pyrogenic Exotoxins
    • - Tissue invasive exotoxins
    • - Miscellaneous Exotoxins
  2. Neurotoxins - Function - Organism -  Mechanism - Result - Note
    • Function: 
    • - act on nerves or motor end plates causing paralysis
    • A. Clostridium tetani
    • - Tetanus Toxins
    • - H - subunit: binds to neuronal gangliosides
    • - L - subunit:blocks release of inhibitory NT
    • *Tetanus: continous motor neuron activity/ uncontrolled muscle contraction
    • * Vaccine: formalin

    • B. Clostridium Botulinum
    • - Botulinum Toxin
    • - inhibits acetylcholine release from motor end plates
    • *Botulism: Flaccid paralysis of resp. m.
  3. Enterotoxins - Definition - Symptomps - example bacs - Mechanism
    • Definiton: act on GIT causing diarrhea 
    • - inhibit NaCl resorbtion, activate NaCl secretion or kill int. ep. cells
    • --> Result: osm. pull of fluid into intestine

    • 1) Infectious Diarrhea: 
    • - Bacs colonize and bind to GOT  - cont. releasing enterotoxins
    • (patient can die by dehydration if bacs arent killed). 
    • - eg: E.coli, Vibrio Cholera(cholera = increased cAMP increase intraluminal NaCl & change osmotic pressure), Campylobacter jejuni, Shigella dysenteriae

    • 2) Food Poisining: 
    • - bacs grow in food and release enterotoxins in food
    • - person digests this food and vomits or diarrhea in less than 24 h
    • - examples:  Bacillus cereus and Staph. aureus
  4. Pyrogenic Exotoxins - definition - examples - mechanism
    • Definition: 
    • stimulates the release of cytokines and can cause: 
    • a) Strep. pyogenes: Scarlet fever/ rush 
    • b) Staphyl. aureus: Toxic shock syndrome (Fever,rash)
  5. Tissue Invasive exotosin - Defintion - Examples - Symptomps
    • Function: 
    • - allows bac to destroy and tunnel through tissue 
    • - includes enzymes that destroy DNA, collagen, NAD, RBC & WBC
    • Examples:
    • a) Strept. pyrogenes: Hemolysins, DNAase, Hyalurinadase (s. Q50)
    • b) Staphylo. aureus (s. Q54): lipase, penecillinase, Leukocidin
    • --> hydrolyzes lipids, activates plasminogen, lyses WBC
    • c) Clostridium perfringens

    Symptomps: Skin infections, Abscesses, Systemic infection
  6. Miscellaneous Exotoxins - Definition- examples - Symptomps
    • Definition: 
    • - a virulance factor
    • a) Bacillus antracis: edema factor - stops phagocytosis by increasing the cAMP to deactivate Macrophage (s. Q80)
    • b) Corynebacterium diptheriae: myocarditis, Peripheral nerve palsies (Q. 62)
    • c) Berdetella pertussis (Q 59): whooping cough

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