Final > Molecular Basis of Infection Flashcards
Define pathogenicity.
The ability to cause disease.
Define virulence.
The degree of pathogenicity (ability to cause disease).
What are the 3 main portals of entry for microorganisms to enter a host?
- Mucous membranes
- Skin
- Parenteral route (cut)
What is meant by ID₅₀?
A measure of the infectious dose necessary to infect 50% of the population. (virulence)
What is meant by LD₅₀?
A measure of the lethal dose necessary to kill 50% of the population. (potency)
What can have an effect on the ID₅₀ of a microorganism?
Environmental/chemical factors. Ex: lime increases the infectivity of Cryptosporidium parvum.
By what process do pathogens attach to host tissues?
By adherence (adhesion), where adhesins (ligands) on the pathogen bind to receptors on the host cell.
What is a glycocalyx?
A carbohydrate coating on the outside of many bacteria.
What is the function of M protein on the surface of a microorganism?
To resist phagocytosis by the host immune system.
What is the function of OPA protein on the surface of a microorganism?
To allow attachment to the host cells.
What is the function of waxy lipid (mycolic acid) on the surface of a microorganism?
To resist digestion.
How can antigenic variation help microorganisms survive in the host?
The microorganism alters its surface antigens, rendering antibodies ineffective.
What is the purpose of an invasin? In what 2 ways can it help a microorganism
A bacterial surface protein
- Rearranges actin cytoskeleton to allow entry into host
- Rearranges actin to allow transmission to new hosts
What is a siderophore?
A protein secreted by a pathogen which can bind iron more tightly than the host cell can, making it available for the pathogen.
What part of the antigen does IgA target? What is characteristic of this region?
Targets the middle region of the antigen which is rich in proline.
What is an example of a bacterial siderophore?
Enterobactin.
In what 4 main ways can pathogens cause direct damage to a host cell?
- Disrupt host cell function
- Use up host cell nutrients
- Produce waste products
- Multiply and lyse host cell