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pathogenicity
ch 15
87
Microbiology
Undergraduate 3
07/31/2012

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Term
parasitic organism
Definition
a symbiont that harms or lives at the expense of its host
Term
what are the two types of parasites
Definition
1. ectoparasite - lives on the host
2. endoparasite- lives within the host
Term
what are the four types of hosts
Definition
1. final host
2. intermediate host
3. transfer host
4. reservior host
Term
final host
Definition
host on ( or in) which parasite either gains sexual maturity or reproduces
Term
intermediate host
Definition
serves as a temporary but essential enviroment for some stages of parasites development
Term
transfer host
Definition
is not necessary for development but serves as a vehicle to the final host
Term
reservior host
Definition
nonhuman organism infected with a parasite that can also infect humans
Term
infection
Definition
growth and multiplication of parasite on or within host
Term
infectious disease
Definition
disease resulting from infection
Term
pathogen
Definition
a parasite organism that causes infectious disease
Term
pathogenicity
Definition
the ability for a pathogen to cause disease
Term
the outcome of a host-pathogen relationship depends on
Definition
the number of pathogen organisms present
virulence of pathogen
host's defense or degree or resistance
Term
virulence
Definition
measures the degree or intensity of pathogenicity
Term
3 things virulence depends on
Definition
1. infectivity- the ability to establish a focal poitn of infection
2. invasivness- abuility to spread to adjecent cells or other tissue
3. pathogenic potential - the degree to which pathogens can cause damage to host the major aspect is toxgenicity ( the ability to prodeuce toxins)
Term
lethal dose 50 (LD50)
Definition
the number of pathogens that will kill 50% of an experimental group of hosts
Term
infectious dose 50 (ID50)
Definition
number of pathogens that will infect 50% of an experimental group of host
Term
a successful basterial pathogen must be 7 things
Definition
1. maintain a reservior - place to live before and after infection
2. be transported to host
3. adhere to, coloinze, and or/ invade host
4. multiply or complete life cycle on or in hsot
5. initially evade host defenses
6. damage host
7. leave host ( return to reservior or enter new host
Term
all bacterial pathogens must have at least one reservior?
Definition
true
Term
for human pathogens what are three reserviors
Definition
other humans
animals
enviroment
Term
what are two types of contact between hosts
Definition
direct contact- coughing, sneezing, body contact
indirect contact- vehicles ( soil, air, water,food), vectors ( living organisms that transmit pathogens), fomites ( inanimate objects that harbor and tranmit pathogens)
Term
attachment of a parasite to a host is mediated by special molecules or structures called
Definition
adhesins or ligands which help bind to the receptors of the host cells
Term
common adhesins or ligands that help the parasite bind to the receptors of the host are
Definition
fimbriae or pili, glycocalyx or capsule, slime layer, M protein, techoic and liotechoic acids
Term
what is colonization
Definition
establishment of a site of microbial reproduction on or within host
Term
colonization depends on
Definition
ability of the pathogen to compete
Term
is the result of colonization necessarily tissue invasion and or damage?
Definition
no
Term
what can the invasion of the bacterial pathogen be
Definition
can be active penetration of hosts mucous membrane or epithelium via lytic substance that alter host tissue
Term
in what three steps does the invasion os a bacterial pathogen accomplish penetration
Definition
1. attack the ground substance and basement membranes of integuments and intestinial lining
2. degrade protein-carbohydrate complexes between cells
3. disrupt the cell surface
Term
passive penetration of invasion of the bacterial pathogen can be
Definition
skin or mucous lesions, insect bites, damage by other organism, wounds or abrasions, phagocytosis, endocytosis
Term
once below mucous membrane bacterium can spread into deeper tissue
Definition
true
Term
when bacterium spreads into deeper tissue what might result
Definition
may involve production or specific products and or enzymes that promote spreading
may enter small terminal lymphatic capillaries
once the circulatory system is reached the pathogen has access throughout the host.
Term
when does the pathogen have access throughout the host?
Definition
once the pathogen has reached the circulatory system
Term
when does growth and multiplication of the pathogen occur
Definition
once the pathogen finds the appropriate enviroment within the host
Term
do some pathogens actively grow in the blood plasma?
Definition
yes
Term
bacteremia
Definition
presences of viable bacteria in blood
Term
septicemia
Definition
presence of bacteria or of their toxins in the bloodstream
Term
the pathogen must leave the cell is it is going to be perpetuated
Definition
true
Term
the pathogen leaves the hoat and either moves to -- or to --
Definition
another host or into a reservior
Term
most pathogenic bacteria leave by passive mechanisms for example
Definition
feces, droplets, saliva,desquamated cells
Term
virulence factors
Definition
products or structural components that contribute to virulence or pathogenicity
Term
example of virulence factors
Definition
adhesins, capsules, lytic subastances, products promoting spread
Term
often enviromental factors control expression of virulence factors
Definition
true
Term
3 examples of regulation of virulence factors which are coontroled often by enviromental factors
Definition
1. gene for diptheria toxin regulated by iron
2. expression of virulence genes increased by body temperature
3. expression of cholera toxin regulated by PH, temperature osmolarity and available amino acids
Term
intoxications
Definition
disease that results from entry of a specific preformed toxin into host
Term
toxin
Definition
a substance that alters the normal metabolism of host cells with negative effects on the host
Term
towins of bacteria are two types
Definition
exotoxins and endotoxins
Term
exotoxins
Definition
soluble, heat liable proteins that are usually released into the surrounding as the bacteria grow
Term
endotoxins
Definition
the LPS of the gram negative bacteria
Term
exotoxins are specialized by specific bacteria ( often with plasmid or prophage containing toxic genes)
Definition
yes
Term
are exotixins heat liable proteins which are inactivated at 60-80 degrees celcius?
Definition
yes
Term
what are among the most lethal substances known
Definition
exotins
Term
exotoxins are not associated with a specific disease and have no specific mechanism of action
Definition
false they are associated with a specific disease and have a specific mechanism of action
Term
highly immunogenic ( antitoxin antibodies are formed for endotoxins or exotoxins?
Definition
exotoxins
Term
are endotoxons or exotoxins easily inactivated by chemicals?
Definition
exotoxins,
Term
formaldehyde and iodine form immunogenic toxiod are examples of chemicals which inactivate endo or exo toxins?
Definition
exotoxins
Term
AB exotoxins are composed of two subunits
Definition
A subunit- responsible for toxic affect
B subunit - binds to the target cell
Term
examples of AB exotoxins entry
Definition
diptheria toxin
Term
can AB toxins be specific host site exotoxins?
Definition
yes
Term
spcific host site exotoxins may include
Definition
neurotoxins
enterotoxins
cytotoxins
AB toxins
Term
neurotoxins
Definition
usually ingested as preformed toxins target nerve tissue
Term
enterotoxins
Definition
target intestinal mucosa
elicit profuse fluid secretion
Term
cytotoxins
Definition
specific toxic action on cells/tissues of specific organs
Term
membrane disrupting exotoxins
Definition
lyses the cell by disrupting the integrity of the membrane they produce pore forming exotoxins which bind to the cholesterol portion of the membrane and insert itself in the membrane
Term
phospholipases are a type of --- that do what ---
Definition
are a type of membrane disrupting exotoxins that remove charged heads of phospholipids and destabilizes the membrane
Term
leukocidins
Definition
a type of pore forming exotoxin that kills phagocytic leukocytes
Term
hemolysins
Definition
are a type of pore-forming exotoxin that kills erythrocytes, leukocytes and many other cells
Term
streptolysin O
Definition
a type of hemolysin that is oxygen sensative
Term
streptolysin S
Definition
a type of hemolysin that is oxygen stable
Term
superantigens
Definition
nonspecifically stimulate T-cells, and cause a massive release of cytokines
Term
what do superantigens result in
Definition
systematic toxicity in host and supression of specific immune response
Term
what are two prime examples of superanitgens
Definition
1. staphylococcal enterotoxins that cause food poisioning and the toxin that causes toxic shock syndrome
Term
with endotoxins what is the toxic portion of the LPS
Definition
the lipid A, not a singel macromolecular structure seems to be a complex array of lipid residues
Term
is endotoxins heat stable
Definition
yes
Term
when are endotoxins toxic?
Definition
only at high doses
Term
are endotoxins highlt immunogenic?
Definition
no weakly
Term
endotoxins are usually capable of producing general systematic effect like
Definition
fever
shock
blood coagulation
weakness
diarea
inflamation
intestinal hemmorage
fibrinolysis
Term
endotoxins bring about effect indirectly by interacting with host molecules and cell activating host systems
Definition
true
Term
when endotoxins interact with macrophages they release
Definition
endogenous pyrogen
Term
when endotoxins bind to the LPS binding protein they release
Definition
cytokines
Term
exotoxins are ---- whereas endotoxins are
Definition
proteins.. lipopolysaccharides
Term
endotoxins are released when
Definition
gram-negative bacteria die and their cell walls undergoe lysis
Term
what three things on the envasion of a bacteria help the bacteria stay away from the comliment system
Definition
capsules, lengthened O-chanin, serum restance
Term
what is serum resistance
Definition
modifies lipoolingosacharides interfere with formation of membrane attack system
Term
what is the compliment system
Definition
The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism
Term
what helps bacteria resist phagosytosis of the host cell
Definition
1.capsules
2.specialized surface proteins -that block adherence of phagocyctes of bacterium
3.production of leukocidins
4. proteases production- that cleave compliment factor C5a (phagocyte chemoattractant)
Term
how do bacteria pathognes survive inside phagocytic cells?
Definition
escape from phagosome before fusion with lysosome
prevents fusion of lysosome with phagosome
resistance to toxic products of phagolysosome
Term
how do bacteria pathogens invade the immune responce
Definition
capsules, genetic variation of surface antigens
production of IgA proteases
production of proteins that interfere with antibody-mediated opsonization ( the process of targeting an antigen)
Term
exotoxins are ---- whereas endotoxins are
Definition
proteins.. lipopolysaccharides
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