1 / 21

Host Defenses, Microbial Evasion & Virulence Factors

Host Defenses, Microbial Evasion & Virulence Factors. Overview. Host Defenses Microbial Virulence Factors Host Evasion Tactics. Host Defenses. **. Bacteria vs Antibacterial Agents 2003 Mascaretti OA (editor). ** No bacteria can penetrate intact skin.

yana
Download Presentation

Host Defenses, Microbial Evasion & Virulence Factors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Host Defenses, Microbial Evasion & Virulence Factors

  2. Overview • Host Defenses • Microbial Virulence Factors • Host Evasion Tactics

  3. Host Defenses ** Bacteria vs Antibacterial Agents 2003 Mascaretti OA (editor) **No bacteria can penetrate intact skin

  4. Toll-like receptors: Innate immune system Pattern recognition receptors (PRR); produce lymphokines when stimulated Microbial Pathogenesis and the Intestinal Epithelial Cell 2003 Hecht GA (Editor)

  5. Classes of Lymphocytes Antigen recognition Effector functions Antibody Secretion B lymphocyte Activation of B & T cells Macrophage activation Helper T lymphocyte(CD4) Inflammation Target cell lysis Cytolytic T lymphocyte (CTL) (CD8) Target cell lysis Natural Killer cell (NK) Bacteria vs Antibacterial Agents MascarettiOA (ed) 2003

  6. Superantigens - S.pyogenes - S.aureus

  7. Prokaryotic and Eukaryotic Interactions Eukaryotic Cell Prokaryotic Cell Pili or adhesins Intracellular Control of virulence factors:(Pilin, capsule, invasins, toxins etc) Virulent Bacteria Adherence blockers Receptor

  8. Prokaryotic and Eukaryotic Interactions Eukaryotic Cell Prokaryotic Cell Pili or adhesins Intracellular Control of virulence factors:(Pilin, capsule, invasins, toxins etc) Virulent Bacteria Adherence blockers Receptor COLONIZATION

  9. Prokaryotic and Eukaryotic Interactions Eukaryotic Cell Prokaryotic Cell Pili or adhesins Intracellular Control of virulence factors:(Pilin, capsule, invasins, toxins etc) Virulent Bacteria Adherence blockers Receptor INVASION COLONIZATION

  10. Bacterial Invasion: Conserved macromolecular systems • Adherence (attachment) • Entry into body • Avoidance of host immune defense • Damage (tissue or functionality) • Resist antibacterial agents

  11. Adhesion • Pilus: Chaperone-usher pathway- E.coli • Non-pilus Adhesins- invasin (Y.pseudotuberculosis)- intimin (enteropathogenic E.coli)

  12. Chaperone-Usher Pathway Adhesin: binds Gal(α1-4)Gal A A Tip Fibrillum A A Pilus Shaft A A Usher C H C Gm(-) Bacterial Periplasm A Cytoplasmic membrane A H A D Chaperone Pilus tip Fibrillum subunits Pilus assembly machinery Pilussubunit I B A H C D J K E F G Regulation Anchor Usher Chaperone

  13. Nonpilus Adhesin Intimin (Enteropathogenic E.coli) Microbial Pathogenesis and the Intestinal Epithelial Cell 2003 Hecht GA (Editor)

  14. Toxins Listeriolysin O Superantigens:e.g. Spe, TSST1 Bacteria vs Antibacterial Agents 2003 Mascaretti OA (editor)

  15. Exotoxins: Proteins • Clostridium tetani; Tetanus toxin (neurotoxin) • Clostridium botulinum; Botulinum toxin (neurotoxin) • Clostridium perfringens: Clostidial toxin (phospholipase activation) • Clostridium difficile; Toxin A (enterotoxin), Toxin B (cytotoxin) • Streptococcus pyogenes; Erythrogenic toxin (vasodilation) • Staphylococcus aureus; Toxic shock syndrome toxin TSST1 (hypotension, superantigen) • Bordetella pertussis; pertussis toxin (ADP-ribosylation of G proteins) • Corynebacterium diphtheriae; Diphtheria toxin (protein synthesis inhibitor) Endotoxin: LPS in cell wall of Gram (-)

  16. Capsule • Network of polymers (polysaccharide or protein) covering bacterial surface- S.pyogenes capsule: hyaluronic acid- S.pneumonia capsule: polysaccharide • Prevent C3 convertase formation by failing to bind serum protein B (no complement activation) • Antibody formation to capsule can be protective (vaccine)

  17. Pathogenicity Islands • Different G+C content from host genome • Mobile genes associated with tRNA and/or insertion sequence (IS) elements • Carry multiple virulence factors • Large size

  18. Host Evasion: • Adherence • sIgA Protease • Iron Acquisition mechanisms • Intracellular residence:- vacuole- free in cytoplasm • Survive phagocytosis • Capsule; prevents phagocytosis • Evade antibody response:- Antigenic variation (pili, LPS, capsule)- Capsule that mimics host antigens • Prevent migration of phagocytes

  19. Prevention • Vaccine to interfere with critical mechanism of host evasion- adherence mechanism- toxin • Antibacterial agents • Probiotics/Prebiotics

  20. Overview • Host Defenses • Microbial Virulence Factors • Host Evasion Tactics

More Related