Pathogenicity Flashcards
a symbiont that harms or lives at the expense of its
host
Parasitic organism
lives on surface of host
ectoparasite
lives within host
endoparasite
host on (or in) which parasite either gains sexual maturity or reproduces
final host
serves as temporary but essential environment for
some stage of parasite’s development
intermediate host
is not necessary for development but serves as
vehicle for reaching final host
transfer host
nonhuman organism infected with a parasite that
can also infect humans
reservoir host
growth and multiplication of parasite on or within
host
infection
disease resulting from infection
infectious disease
any parasitic organism that causes infectious
disease
pathogen
ability of pathogen to cause disease
pathogenicity
Measure of the degree or intensity of pathogenicity
virulence
Determined by three characteristics of the pathogen
virulence
what are the three characteristics that determine virulence
infectivity, invasiveness, and pathogenic potential
ability to establish focal point of infection
infectivity
ability to spread to adjacent cells or other
tissues
invasiveness
degree to which pathogen can cause damage
to host
pathogenic potential
what is the major aspect of pathogenic potential
toxigenicity
what is virulence correlated to
mode of transmission and survival in external environment
what often control expression of
virulence genes
environmental factors
number of pathogens that will kill 50% of an
experimental group of hosts
lethal dose 50
number of pathogens required to infect 50% of an
experimental group of hosts
infectious dose 50
All bacterial pathogens must have at least one
reservoir
examples of direct contact
coughing, sneezing, body contact
living organisms that transmit pathogen
vectors
inanimate objects that harbor and transmit
pathogens
fomites
attachment is mediated by special molecules
or structures
adhesins or ligands
what do adhesins bind to
receptors on host cells
Establishment of a site of microbial reproduction on or
within host
colonization
presence of viable bacteria in blood
bacteremia
presence of bacteria or their
toxins in bloodstream
septicemia
what are the steps of a pathogen entering a host
colonization, invasion, growth/multiplication, and leave
diseases that result from entry of a specific preformed
toxin into host
Intoxications
substance that alters the normal
metabolism of host cells with negative effects on
host
toxin
two types of toxins of bacteria
endotoxins and exotoxins
soluble, heat liable proteins that are
usually released into the surroundings as the bacteria
grow
exotoxins
the LPS of gram negative bacteria
endotoxins
Synthesized by specific bacteria
Heat liable proteins
Among the most lethal substances known
Easily inactivated by chemicals
exotoxins
types of exotoxins
Neurotoxins, Enterotoxins, and Cytotoxins
Usually ingested as preformed toxins
target nerve tissue
neurotoxins
target intestinal mucosa
elicit profuse fluid secretion
enterotoxins
Specific toxic action on cells/tissues of specific
organs
cytotoxins
what is the A subunit of AB exotoxins responsible for
for toxic effect
what is the B subunit of AB exotoxins do
binds to target cell
kill phagocytic leukocytes
leukocidins
kill erythrocytes, leukocytes, and many other cells
hemolysins
Removes charged head of phospholipid
Destabilizes the membrane
Phospholipases
Nonspecifically stimulate T-cells
Cause release of massive quantities of cytokines
Results in systemic toxicity in host
Suppression of specific immune response
Superantigens
Toxic portion of LPS is Lipid A Heat stable Toxic only at high doses Weakly immunogenic produce systematic effects
Endotoxins
bring about effects indirectly
interacts with host molecules and cells,
activating host systems
endotoxins
series of proteins circulating in blood and fluids
circulate in inactive form
over 30 proteins known
complement system
complement system destroys microbes via
inflammation, cytolysis, phagocytosis
Evade the complement system by
capsules, lengthened O chains, and serum resistance
