bacterial virulence
DESCRIPTION
TRANSCRIPT
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 arealways pathogenic
Many microbes arepotentially pathogenic
Most microbes arenever pathogenic
Host - parasite Interaction
Intracellular
Eukaryotic Cell
Receptor
Virulent Bacteria
Prokaryotic Cell
Control of virulence factors:(Pilin, capsule, invasins, toxins etc)
Adherence blockers
Pili or adhesins
Prokaryotic and Eukaryotic Interactions
Intracellular
Eukaryotic Cell
Receptor
Virulent Bacteria
Prokaryotic Cell
Control of virulence factors:(Pilin, capsule, invasins, toxins etc)
COLONIZATION
Adherence blockers
Pili or adhesins
Prokaryotic and Eukaryotic Interactions
Intracellular
Eukaryotic Cell
Receptor
Virulent Bacteria
Prokaryotic Cell
Control of virulence factors:(Pilin, capsule, invasins, toxins etc)
COLONIZATION INVASION
Adherence blockers
Pili or adhesins
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.
Bacterial Virulence Factors
Virulence factors help bacteria • invade the host• cause disease• evade host defenses.
Include:1. Attachment (via adhesins)2. Colonization3. Invasiveness4. Toxins & Enzymes5. Inhibition of Phagocytosis
1-Attachment (via adhesins)
They allow bacteria to bind to host cells :
• fimbriae • some bacterial cell
walls • capsules
These adhesins bind to specific epithelium receptors or they are able to maintain even closer contact.
Cilia - motion
Flagellum - motion
A
B
DCell Parts
Flagellum - motion
Cell Wall – protection, invasion, evasion
Ribosome – production of toxins/attachment proteins on cell wall
Cilia - motion
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:
1. Using Pili (fimbriae) to Adhere to Host Cells
2. Using Adhesins to Adhere to Host Cells
3. Using Biofilms to Adhere to Host Cells
3-Invasiveness
• 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.
Invasiveness
• Hyaluronidase
• Coagulase
• Streptokinase
(dissolves Clots)
4-Toxins &EnzymesToxins• They are products of a
pathogen that destroy/damage/
• inactivate one or more vital component of the host.
• Classes of toxinsNeurotoxinsEnterotoxins Cytotoxins
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.
5-Inhibition 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
Summary Virulence factors
Thank you