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8 Cards in this Set

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PATHOGEN
a microorganism capable of producing pathology in a percentage of normal individuals by avoiding or manipulating the innate immune system
VIRULENCE
quantitative measure of pathogenesis
Infectious Dose 50 (ID 50)
the dose that will infect 50% of normal individuals;

in lower doses, infection may result without overt disease (subclinical infection)
Lethal Dose 50 (LD 50)
dose required to kill 50% of the test animals
Determinant of Pathogenesis and Virulence Factors
components of the pathogen responsible for its ability to cause an infection;

often defined by mutations in virulence genes = lower virulence / ↑ LD50

- virulence genes: exist for the purpose of propagating in the host

pathogenesis usually involves numerous determinants of pathogenicity;

mutations which result in avirulence often pleiotropic in nature, mapping to a gene involved in reg'n of multiple virulence factors
Obligate Pathogens

(Intracellular Obligate Pathogens)
cannot be found anywhere but in association with its host

can only grow inside of host cells
Facultative Pathogens

(Intracellular Facultative Pathogens)
can grow or survive in the environment as well as in its host

can grow both inside or outside of cells
STAGES OF PATHOGENESIS
* Encounter: breathing, eating, normal body flora

* Entry: lots of body surfaces

* Colonization: pili for attachment

* Multiplication: become bacteria

* Invasion: Type III secretion

* Evasion:
- avoid being recognized
- kill immune cells
- live inside immune cells