Mechanisms of Pathogenicity Flashcards
Define pathogenicity
The ability to cause disease
Define Virulence
The degree of pathogenicity
Define portal of entry
How a pathogen enters the host
- Mucous membranes
- Skin
- Parenteral Route (Deposited directly into tissues when barriers are penetrated)
Define ID50
Infectious dose for 50% of a sample population
-Measures virulence of a microbe
Define LD50
Lethal dose for 50% of a sample population
-Measures potency of a toxin
Define adherence
The process in which pathogens attach to host tissues
-aka adhesion
Define Biofilm
Microbial communities that share nutrients
Identify the portals of entry that pathogens use to gain entry into the body
- Mucous membranes
- Skin
- Parenteral route
Give examples of how pathogens adhere to host cells
Adhesins (ligands) on the pathogen bind to receptors on the host cells–Glycocalyx and fimbriae
How does M protein contribute to virulence?
Resists phagocytosis (Ex: Streptococcus pyogenes)
How does Opa protein contribute to virulence?
Allows attachment to host cells (Ex: Neisseria gonorrhoeae)
How does mycolic acid contribute to virulence?
Resists digestion (Ex: Mycobacterium tuberculosis)
How does coagulase contribute to virulence?
Coagulate fibrinogen
How do kinases contribute to virulence?
Digest fibrin clots(fibrinolysin/streptokinase)
How does hyaluronidase contribute to virulence?
Digests polysaccharides that hold cells together
How does collagenase contribute to virulence?
Breaks down collagen
How does IgA protease contribute to virulence?
Destroy IgA antibodies
How does antigenic variation contribute to virulence?
Pathogens alter their surface antigens rendering antibodies ineffective Body mounts an immune response to one antigen, pathogen changes antigen and evades immune response
How do invasins contribute to virulence?
Surface proteins produced by bacteria that rearrange actin filaments of the cytoskeleton
-Cause membrane ruffling and engulfing of bacteria
How do biofilms contribute to virulence?
- Play a role in evading phagocytes
* Biofilm bacteria more resistant to phagocytosis, shielded by extracellular polymeric substance(EPS) of biofilm
How do siderophores contribute to virulence?
- Iron is required for most pathogenic bacteria
* Siderophores are proteins secreted by pathogens that bind iron more tightly than host cells
Describe the ways in which pathogens cause direct damage to host cells.
- Disrupts host cell function
- Uses host cell nutrients
- Produces waste products
- Multiplies in host cells and causes ruptures
Define Toxin
Poisonous substances produced by microorganisms
-Produce fever, cardiovascular problems, diarrhea, and shock
Define toxigenicity
The ability of a microorganism to produce a toxin
