Virulence factors are pathogen-produced extracellular enzymes or structural components of pathogens that aid in the colonization, multiplication, invasion, and evasion of host immune response.
Enzymes which acts as virulence factors
- Hyaluronidase: It promotes the spreading of the organisms in tissues by breaking down hyaluronic acid.
- Collagenase: It breaks down the collagen network supporting the tissues.
- Streptokinase: It is a fibrinolytic enzyme. Fibrin clots trap the microorganisms and limit their spread.
- Coagulase: It is a fibrin clotting enzyme and helps the organism to localize in a particular site, e.g., wounds.
- Hemolysins: Breakdown of RBCs.
- Lecithinases (or phospholipases): Help the organism to break down phospholipid-lecithin.
- Leukocidins: Kills white blood cells.
Toxins such as diphtheria toxin, cholera toxin, botulinum toxin, toxic shock syndrome toxin, tetanus toxin, botulinum toxin, etc., aids in the pathogenesis of respective pathogens.
- Capsule: Antiphagocytic
- Lipopolysaccharide layer: Endotoxin
- Teichoic acid: Endotoxin, etc.
You can get detailed information on the virulence factors of each pathogen with their functions in the below-mentioned blog posts.