Process of Pathogenesis (bacterial)


  • Pathogens are transmitted by airborne droplet nuclei, via food or water, contact, fomites or living vectors.
  • Bacteria enter the skin by penetrating the skin or mucous membrane, being inhaled or digested.
  • Adhere to the host cells using pili, fimbriae or adhesins (chemicals that make attachment easier)
  • Bacteria then colonise the host tissues and begin to grow. In order to survive they must grow faster than the host tissues replenish themselves.
  • Often use agressins in order to invade the host tissues, these are usually proteolytic or lipolytic.
  • Evade host defenses by hiding from the immune system in capsules or by living in the phagosome.
  • Toxins damage cells, inhibit proteins, interfere with signaling, inhibit neurotransmitter release and activate immune responses.
  • Endotoxins are the lipid A component of gram neg walls
  • Exotoxins are soluble proteins secreted by gram pos bacs. They are less potent and less specific in their actions but are more heat stable than endotoxins. Can be neurotoxins, cytotoxins or endotoxins.

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