22 Pathogenic interactions Flashcards
ability of microbe to cause disease
pathogenicity
quantitative measure of degree of pathogenicity, as indicated by mortality rate, disease severity, etc.
virulence
any microbial comp. that is required for/contributes to pathogenicity
virulence factor
how to quantitate virulence?
infect susceptible host with ^ higher doses of org, monitor progession of disease over time, determine LD50 (# orgs that will cause disease in 50% animals over specified time)
how determine whether particular microbe comp. is virulence factor?
create microbe deficient in particular comp and test ability cause disease
end in -emia mean?
microbe in bloodstream
steps that must be completed to successfully infect and cause disease?
1) be transmitted to, and enter into, a suitable host 2) avoid being removed after entry 3) migrate to a site within the host able to support growth 4) overcome host defenses and multiply at the preferred site 5) exit host and transfer to a new host to repeat cycle
most common portals of entry:
body tracts (resp, intestinal, uro-genital), conjunctival mes
orgs required to start infection
infectious dose
resp requires ____ infectious dose, ingestion requires ____ dose
lower; higher
strategies avoid removal after entry?
pili, cell surface proteins, capsular polysacc
strategies for migrate to other body sites?
bacterial tissue-degrading enzymes (hyaluronidase, collagenase)
to grow and survive in host, bacteria must:
obtain nutrients from host (hemolysins) and evade host immune sys (bacteria capsule, bacterial toxins)
strategies exit host?
mucus/saliva, feces, semen/vag discharge, pus/blood/urine–>exit much larger numbers than enter
how do pathogens damage host?
1) host immune response 2) direct result of pathogen actions (tissue degrading enzymes, bacterial toxins)
two types bacterial toxins?
endo and exo
lipid A portion of LPS (gram neg only) is ____
endotoxin
LPS cause:
immune sys ^ cytokine production, activation of blood coagulation pathway–>toxic shock
current limit in IV fluids and drugs is:
0.25 units/mL for IV
bio detection of endotoxin?
limulus amoebocyte lysate assay (WBC of horseshoe crab will clot when exposed to LPS)
LPS destroyed at ___ degrees for __ minutes
250; 30
immobilized resins that bind LPS
affinity matrixes
toxic proteins secreted by bacteria as grow; highly potent in very small amounts, act on eucaryotic cells to kill or alter metabolism
exotoxins
three general types of exotoxins?
cytotoxins (block protein synth), enterotoxin (cause hypersecretion of water from intestinal cells), neurotoxin (interfere neurotrans)
