Microbial Mechanisms of Pathogenicity Flashcards
Define pathogens
Disease causing microorganism
Define pathogenicity
ability to cause disease
Define virulence
degree of pathogenicity
Define infection
when body is invaded by a harmful microorganism
Define disease
when the health of the human body is affected by an infection
What are 3 portals of entry
1) mucous membrane
2) skin
3) parenteral route
What us the easiest and most common entry
respiratory tract ( mucous membrane)
Define ID50
infectious dose for 50% of a sample population
measures virulence of a microbes
Define LD50
lethal dose for 50% of a sample population
measures potency of a toxin
What are 2 ways of adherence of microorganisms to Host cells
1) Surface molecules on the pathogens
2) bind to complementary surface receptors of host cell
Describe surface molecules on the pathogens
adhesins or ligands
located on glycocalyx or fimbraie or pili
glycoproteins or lipoproteins
Define bind to compementary surface receptors of host cell
mannose-sugar
What are 4 ways pathogens pentrate host defenses
1) capsules
2) cell wall components
3) enzymes
4) antigenic variation
Describe capsules as a way to penetrate host defenses
glycocalyx around the cell wall
impair phagocytosis ( streptococcus pneumoniae, haemophilus influenza,bacillus anthracis)
have capsule increased virulence
body can create antibodies against capsules
Describe cell wall components to penetrate host defenses
1) M protein resists phagocytosis
2) Opa protein
3) waxy lipid ( mycolic acid) resists digestion
Describe how M protein resists phagocytosis
streptococcus pyogenes
produce heat resistence and resistent proteins
Describe Opa protein as away to penetrates host defenses
Neisseria gohorrhoeae
attach to host cell
use fimbrae and outer membrane protein
inhibit T helper cell
Describe waxy lipid as a wayof penetrating host defenses
resists digestion
ex: mycobacterium tuberculosis
has ability to divide in microphage
What are 5 enzymes used to penetrate host defenses
1) Coagulases
2) Kinases
3) Hyaluronidase
4) Collagenase
5) IgA proteases
Describe the enzyme coagulases
coagulate fibrinogen
helps with formation of clot. so when infection bacteria form a blood clot,form a wall, and prevent bloodflow to infection site so immune system cells can’t get to site
ex. staphylococcus
Describe kinases as a way to penetrate host defenses
digest fibrin clots
bacteria will destroy the clotthat host body creates to defend itself so that infection can spread
ex. streptococcous
Describe hyaluronidase as a way to penetrate host defenses
digests polysaccharides that hold cells together
produced by streptococcus
ex.gasgrene
Describe collagenase as a enzyme to penetrate host defenses
breaks down collagen
Describe IgA proteases as a way to penetrate host defenses
destroy IgA antibodies
Describe antigenic variation as a way of penetrate hoat defenses
pathogens alter their surface antigens
evade destruction by host antibodies
ex. neisseria,influenza virus
Describe invasins as a way to penetrate into host cell cytoskeleton
surface proteins produced by bacteria
rearrange actin filaments of the cytoskeleton
cause membrane ruffling
ex. salmonella typhi
use actin to move from 1 cell to the next ( shigella and listeria)
What are 3 ways that bacterial pathogens damage host cells
1) by using the host’s nutrients
2) direct damage
3) production of toxins
How do using host’s nutrients a way bacterial pathogens damage host cells ( example of one way is the answer)
siderophores-proteins secreted by pathogens
binds iron more tightly than host cells
siderophores has higher affinity for iron then hemoglobin
Describe 4 direct damage as a bacterial pathogens damage host cell
disrupts host cell function
uses host cell nutrients
produces waste products
multiples in host cells and cause ruptures
Define toxins
poisonous substance produced by microorganisms
produce fever,cardiovascular problem,diarrhea,shock
Define toxigenicity
ability of a microorganism to produce a toxin
Describe toxemia
presence of toxin in the host’s blood
What are the 2 types of toxins
exotoxins
endotoxins
Describe exotoxins
proteins produced and secreted by bacteria
soluble in body fluids,destroy host cells and inhibit metabolic functions
ex. hemolysins ( released by beta hemolytic streptococci)
ex. botulinum toxin ( neurotoxin, release by clostridium botulinum)
ex. tetanus toxin ( neurotoxin) released by clostridium tetanu
Exotoxins Sources? Relation to microbe? Chemistry? Fever? Neutralized by antitoxin? LD50
mostly gram + by-products of growing cell protein no yes small
Describe enterotoxins
exotoxins whose activity affects the small intestine
cause are massive secretion of fluid into intestinal lumen and vomiting and diarrhea
ex. vibrio enterotoxin and shiga toxin
Describe endotoxins
bacteria type?
2 examples of bacteria that have this toxin?
Lipid A portion of lipopolysaccharides ( LPS) OF GRAM NEGATIVE BACTERIA
released when the bacteria die
ex. salmonella typhi and proteus vulgaris
Endotoxin Source relation to microbes chemistry fever neutralized by antitoxin ld50
gram - outer membrane lipid A yes no relatively large
Describe 5 portals of exit
1) Respiratory tract
2) gastrointestinal tract
3) genitourinary tract
4) skin
5) blood
