Bacterial Virulence
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This document discusses bacterial virulence factors. It defines virulence as the ability of an infectious agent to cause disease. Virulence factors help bacteria invade hosts, cause disease, and evade host defenses. These include attachment via adhesins, colonization, invasiveness through toxins/enzymes, and inhibition of phagocytosis. Specific virulence factors that promote these abilities include pili/fimbriae, adhesins, biofilms, hyaluronidase, coagulase, streptokinase, toxins like neurotoxins and enterotoxins, enzymes, and mechanisms to avoid or survive phagocytes.
Bacterial Virulence
- 1. Bacterial Virulence Factors Prof. Nesrene Salah Omar
- 2. Objectives • Microbial Mechanisms of Pathogenic • Microbes and humans • Virulence factors • Host - parasite Interaction • Bacterial Virulence Factors
- 3. Microbial Mechanisms of Pathogenic
- 4. Microbes and humans Very few microbes are always pathogenic Many microbes are potentially pathogenic Most microbes are never pathogenic
- 5. Host - parasite Interaction Eukaryotic Cell Pili or adhesins Prokaryotic Cell Intracellular Control of virulence factors: Virulent Bacteria (Pilin, capsule, invasins, toxins etc) Adherence blockers Receptor
- 6. Prokaryotic and Eukaryotic Interactions Eukaryotic Cell Pili or adhesins Prokaryotic Cell Intracellular Control of virulence factors: Virulent Bacteria (Pilin, capsule, invasins, toxins etc) Adherence blockers Receptor COLONIZATION
- 7. Prokaryotic and Eukaryotic Interactions Eukaryotic Cell Pili or adhesins Prokaryotic Cell Intracellular Control of virulence factors: Virulent Bacteria (Pilin, capsule, invasins, toxins etc) Adherence blockers Receptor COLONIZATION INVASION
- 8. Virulence The 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.
- 10. Virulence factors help bacteria • invade the host • cause disease • evade host defenses. Include: 7. Attachment (via adhesins) 8. Colonization 9. Invasiveness 10. Toxins & Enzymes 11. Inhibition of Phagocytosis
- 11. (Attachment (via adhesins-1 They allow bacteria to bind to host cells : Cilia - motion • fimbriae • some bacterial cell walls • capsules These adhesins bind to specific epithelium receptors or they are able to maintain even closer contact. Flagellum - motion
- 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. 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. Virulence Factors that Promote Bacterial Colonization: 3. Using Pili (fimbriae) to Adhere to Host Cells 4. Using Adhesins to Adhere to Host Cells 5. Using Biofilms to Adhere to Host Cells
- 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. Invasiveness • Hyaluronidase • Coagulase • Streptokinase (dissolves Clots)
- 17. 4-Toxins &Enzymes Toxins • They are products of a pathogen that destroy/ damage/ • inactivate one or more vital component of the host. • Classes of toxins Neurotoxins Enterotoxins Cytotoxins
- 20. Enzymes Excretion 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.
- 22. Inhibition of Phagocytosis • Ability of Pathogens to Avoid or Overcome Phagocytes • Avoiding Contact with Phagocytes • Inhibition of Phagocytic Engulfment • Survival Inside of Cells
- 25. Thank you