Bacterial Virulence

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Bacterial Virulence

  1. 1. Bacterial Virulence Factors Prof. Nesrene Salah Omar
  2. 2. Objectives• Microbial Mechanisms of Pathogenic• Microbes and humans• Virulence factors• Host - parasite Interaction• Bacterial Virulence Factors
  3. 3. Microbial Mechanisms of Pathogenic
  4. 4. Microbes and humans Very few microbes are always pathogenic Many microbes arepotentially pathogenicMost microbes arenever pathogenic
  5. 5. Host - parasite InteractionEukaryotic Cell Pili or adhesins Prokaryotic Cell Intracellular Control of virulence factors: Virulent Bacteria (Pilin, capsule, invasins, toxins etc) Adherence blockers Receptor
  6. 6. Prokaryotic and Eukaryotic InteractionsEukaryotic Cell Pili or adhesins Prokaryotic Cell Intracellular Control of virulence factors: Virulent Bacteria (Pilin, capsule, invasins, toxins etc) Adherence blockers Receptor COLONIZATION
  7. 7. Prokaryotic and Eukaryotic InteractionsEukaryotic Cell Pili or adhesins Prokaryotic Cell Intracellular Control of virulence factors: Virulent Bacteria (Pilin, capsule, invasins, toxins etc) Adherence blockers Receptor COLONIZATION INVASION
  8. 8. VirulenceThe ability of an agent of infection to produce disease.The virulence of a microorganism is a measure of the severity of the disease it causes.
  9. 9. Bacterial Virulence Factors
  10. 10. Virulence factors help bacteria• invade the host• cause disease• evade host defenses.Include:7. Attachment (via adhesins)8. Colonization9. Invasiveness10. Toxins & Enzymes11. Inhibition of Phagocytosis
  11. 11. (Attachment (via adhesins-1They allow bacteria to bind to host cells : Cilia - motion• fimbriae• some bacterial cell walls• capsulesThese adhesins bind to specific epithelium receptors or they are able to maintain even closer contact. Flagellum - motion
  12. 12. A Cell Wall –Flagellum - protection,motion invasion, evasion Cell Parts D B Ribosome – production of Cilia - motion toxins/attachment proteins on cell wall
  13. 13. 2-Colonization• The Ability to Adhere to Host Cells and Resist Physical Removal or• the establishment of the pathogen at the appropriate portal of entry.• Pathogens usually colonize host tissues that are in contact with the external environment.
  14. 14. Virulence Factors that Promote Bacterial Colonization:3. Using Pili (fimbriae) to Adhere to Host Cells4. Using Adhesins to Adhere to Host Cells5. Using Biofilms to Adhere to Host Cells
  15. 15. Invasiveness-3• the ability of a pathogen to invade tissues.• Invasiveness encompasses(1) mechanisms for colonization (adherence and initial multiplication),(2) production of extracellular substances ("invasins"), that promote the immediate invasion of tissues(3) ability to bypass or overcome host defense mechanisms which facilitate the actual invasive process.
  16. 16. Invasiveness• Hyaluronidase• Coagulase• Streptokinase (dissolves Clots)
  17. 17. 4-Toxins &EnzymesToxins• They are products of a pathogen that destroy/ damage/• inactivate one or more vital component of the host.• Classes of toxinsNeurotoxinsEnterotoxinsCytotoxins
  18. 18. EnzymesExcretion of certain pathogens to assist them in establishing infection and producing a disease.There are virulence determinant enzymes that dissolve the glue between cells, thus allowing the bacteria to spread rapidly through the tissue.
  19. 19. -5Inhibition of PhagocytosisPhagocytosis
  20. 20. Inhibition of Phagocytosis• Ability of Pathogens to Avoid or Overcome Phagocytes• Avoiding Contact with Phagocytes• Inhibition of Phagocytic Engulfment• Survival Inside of Cells
  21. 21. SummaryVirulence factors
  22. 22. Thank you

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