Bacterial Virulence Factors Prof. Nesrene Salah Omar
Objectives• Microbial Mechanisms of Pathogenic• Microbes and humans• Virulence factors• Host - parasite Interaction• Bacterial Virulence Factors
Microbial Mechanisms of Pathogenic
Microbes and humans Very few microbes are always pathogenic Many microbes arepotentially pathogenicMost microbes arenever pathogenic
Host - parasite InteractionEukaryotic Cell Pili or adhesins Prokaryotic Cell Intracellular Control of virulence factors: Virulent Bacteria (Pilin, capsule, invasins, toxins etc) Adherence blockers Receptor
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
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
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.
Bacterial Virulence Factors
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
(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
A Cell Wall –Flagellum - protection,motion invasion, evasion Cell Parts D B Ribosome – production of Cilia - motion toxins/attachment proteins on cell wall
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.
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
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.
4-Toxins &EnzymesToxins• They are products of a pathogen that destroy/ damage/• inactivate one or more vital component of the host.• Classes of toxinsNeurotoxinsEnterotoxinsCytotoxins
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.
-5Inhibition of PhagocytosisPhagocytosis
Inhibition of Phagocytosis• Ability of Pathogens to Avoid or Overcome Phagocytes• Avoiding Contact with Phagocytes• Inhibition of Phagocytic Engulfment• Survival Inside of Cells