Pathogenesis Flashcards
What is Virulence?
the relative ability of a pathogen to cause disease
can be high or low
What is Pathogenecity?
the ability to cause disease
can either have or not
no high or low
How do you measure Virulence?
use LD50 and/or ID
What is ID?
Infectious Dose
of microbes required to cause a set of symptoms
What is LD50?
Lethal Dose - 50%
of microbes it takes to kill 50% of the host’s cell population
What is a possible course of infection for a extracellular pathogen?
Exposure -> Adherence -> Colonization and Growth -> (Invasion -> Dissemination) or Toxicity -> Tissue Damage/Disease/Transmission
What is a possible course of infection for an intracellular pathogen?
Exposure -> Adherence -> (Invasion -> Dissemination) or Toxicity -> Tissue Damage/Disease/Transmission
What are the 3 types of Specificity?
Host Specificity
Genetic Specificity
Tissue Specificity
What is Adherence to host cells mediated by?
by adhesins
Non-specific = generally sticky (capsule)
Specific = ligand binding
How do intracellular pathogens invade host tissues?
they invade directly into host cells
get taken up by vacuoles
manipulate vacuoles do either disintegrate or don’t fuse w/ lysosomes
How do extracellular pathogens invade host tissues?
the penetrate in btwn host cells
break the tight junctions and celular cements that bind epithelial layers
What are 3 possible mechanisms for intracellular invasion of host cells?
Zipper mechanism
Trigger mechanism
Coiling phagocytosis
What is the zipper mechanism?
used for invasion of host cell
bacterium “sinks” into cell
pathogen gives signal to host and host lets it in = gentle
What is the Trigger mechanism?
used for invasion into host cell
major rearrangments of host membranes
host bursts open and swallows pahtogen up = brutal
What is coiling phagocytosis?
used for invasion of host cell
long coiling psuedopod to come out of host and coil around pahtogen and bring it in
What are 4 examples of spreading factors?
Hyaluronidase, Collagenase, Neuraminidase, and Hemolysin
What does the spreading factor, Hyaluronidase, do?
attacks the interstitial cement of connective tissue by depolymerizing hyaluronic acid
What does the spreading factor, collagenase, do?
breaks down collagen
What does the spreading factor, neuraminidase, do?
degrades neuraminic acid and intercellular cement of the epithelial cells of the intestinal mucosa
What does the spreading factor, hemolysin, do?
proteins that destroy red blood cells by lysis
forms rings and pokes holes in red blood cells
What is Dissemination?
the spreading of pathogens through the body systems (blood, CSF, or lymphatic)
What is Endotoxin?
the toxic heat-stable lipopolysaccharide (LPS) present only in the outer membrane of Gram-negative bacteria
released form cell due to shedding or lysis
What are the 3 types of Exotoxin?
- Type I = superantigens - staph aureus toxic shock syndrome toxin
- Type II = exotoxins that damage host cell membranes
- Type III = A/B multisubunit toxins that interfere w/ host cel fxn
Which pathogen causes chlamydia?
Chlamydia trachomatis
What type of pathogen is Chlamydia trachomatis?
obligate intracellular pathogen
What are the 2 life forms of Chlamydia trachomatis?
Elementary Body (EB) and Reticulate Body (RB)
What is the difference between the EB and the RB of Chlamydia trachomatis?
EB = elementary body = non-replicating infectious article = dispersal form = dormant cell
RB = reticulate body = replicating, non infectious = vegetative cell
What type of pathogen is Salmonella enterica spp. enterica?
Extracellular, facultative anaerobe, gram negative bacteria
What are the virulence factors of Salmonella?
Type II Secretion System that secretes effectors
2 Type III Secretion Systems = one for entering host cell, one for escaping vacuole
What are the steps that Salmonella takes to invade host cells?
- salmonella adheres to host cell wall
- salmonella uses Type III secretion system to inject host cell and inject effectors
- causes host cel to engulf salmonella into vacuole (SCV)
- salmonella prevents lysosome binding to vacuole using Type III secretion system
- salmonella then begins replicating and eventually escapes vacuole and spreads
