Colonization, Invasion, and Clinical Disease Flashcards
who benefits (microbe or host) and who is harmed in the following symbiosis?
what is the symbiosis of normal microbiota?
mutualists and commensals
what does it mean for a member of the normal microbiota to be an opportunistic pathogen?
it can cause disease under the right conditions
define pathogenicity
ability of microbe to damage a host
define virulence
relative capacity of microbe to cause damage in a host
define transmissibility
relative ease with which an infectious agent spreads between hosts
define infectivity
capacity of a microbe to become established in a host
define virulence factor
traits that enhance pathogenicity
what are the major categories of virulence factors in bateria?
adhesins, capsules, toxins
what does the attachment specificity in adhesins help bring out?
tissue tropism
host specificity
what do capsules do to increase virulence?
mediate adherence and biofilm formation
what do toxins do to increase virulence?
damage host cell and tissues
what are the two major types of toxins?
exotoxins and endotoxins
Difference between exotoxins and endotoxins
exotoxins - secreted by bacterial cell
endotoxins - come from cell wall
what is an important endotoxin that produces a systemic inflammatory response in gram negative bacteria?
lipid A portion of LPS
what can exotoxins be inactivated with and what is the purpose of this?
inactivated with formaldehyde
resulting toxoid used for vx
what are the 3 basic steps in pathogenesis?
colonization, invasion, damage
define colonization
establishment of pathogen at appropriate portal of entry
Portal of entry examples
mucous membranes, skin, direct deposition beneath skin/mm
At what step of pathogenesis are adhesins used?
colonization
what are the 3 main portals of entry?
gastrointestinal tract
respiratory tract
urogenital tract
what is an example of bacteria co-opting hosts nutrients in colonization?
siderophores - steal iron from iron-binding proteins
how are biofilms helpful in colonization?
facilitate quorum sensing - bio film inhabitants can coordinate cellular activities ex. exotoxin production
what are invasins?
enzymes that cause local damage to host cells and extracellular matrix
what are the two routes of invasion?
paracellular route
transcellular route
define paracellular route
passage between epithelial cells
define transcellular route
passage through epithelial cells themselves
how do pathogens damage the host?
-use host nutrients
-cause direct damage at sites of colonization/invasion
-produce toxins damage sites away from invasion site
-collateral damage from host inflammatory or immune rxns
define subclinical infection
infection not leading to disease
define acute disease
develops rapidly but lasts a short time
define chronic disease
develops slowly is likely to recur for long periods
define carriers
no signs/symptoms of disease but are infected and can transmit
what are the 4 types of carriers?
passive, incubatory, convalescent, and active
what type of carrier would this be - nasal discharge from equine strangles?
active carrier
define passive carrier
carry/transmit a pathogen w/o having had the disease
define incubatory carrier
transmit a pathogen during the incubation period of the disease when there are no overt signs/symptoms in the carrier
define convalescent carrier
harbor/transmit a pathogen while recovering from the disease
define active carrier
are completely recovered from the disease but still harbor/transmit the pathogen
