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Introduction
  • Bacterial virulence
    • intrinsic characteristics that influence the bacterium’s ability to infect a host
    • endotoxins are a type of bacterial virulence factor
  • Endotoxins
    • a lipopolysaccharide found in the cell walls of gram-negative organisms
      • heat-stable
    • release into the body
      • via cell lysis or detachment from the bacteria
      • not actively secreted (unlike exotoxins)
      • bacterial lysis due to antibiotic treatment can cause a large release of endotoxins
    • components
      • O antigen
      • core polysaccharide
      • lipid A
    • causes shock, sepsis, DIC, and death
    • effects from lipid A component
      • macrophage activation
        • release of IL-1 and IL-6
          • fever
        • release of TNF-alpha
          • fever and hypotension
        • release of nitric oxide
          • hypotension
      • complement activation
        • C3a
          • histamine release, causing hypotension and edema
        • C5a
          • neutrophil chemotaxis
      • tissue factor activation
        • activates coagulation cascade
          • results in disseminated intravascular coagulation
 
Exotoxins vs Endotoxins
  Exotoxin
Endotoxin
Species that produce the toxin
  • Some species of gram-positive and gram-negative organisms
  • Gram-negative organisms
  • Listeria
Method of release
  • Actively secreted
  • Bacterial cell lysis or fragmentation
Gene location
  • Plasmid or bacteriophage
  • Bacterial chromosome
Toxicity level
  • High toxicity
  • Low toxicity
Vaccines
  • Available for some toxins in the form of toxoids
  • No vaccines available
Properties
  • Heat-labile
  • Heat-stable
Examples
  • Vibrio cholera
  • Diphtheria
  • Salmonella
  • Shigella
  • Clostridium tetani
  • Clostridium botulinum
  • Neisseria meningitidis
  • Escherichia coli
  • Pseudomonas
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