lect 1 Flashcards
why did robert koch win a nobel prize
for his investigations and discoveries in relation to tuberculosis
what did koch work on
-anthrax, tuberculosis and cholera
establishing causality vs association is the key to….
is the key to bacterial pathogenesis at the whole cell and molecular/genetic (virulence factor) level
what are the 4 koch postulates
-The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms.
-The microorganism must be isolated from a diseased organism and grown in pure culture.
-The cultured microorganism should cause disease when introduced into a healthy organism.
-The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
what is the problem with this postulate:The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms.
-h pylori is present in more than 50% of the world population but only a small proportion of those develop stomach ulcers
-only 5% of those infected with tb become sick
-sometimes it is not the best for the pathogen to kill its host
true or false: host susceptibility plays a role in determining virulence
true
not all individuals respond equaly to infection
name an example of a bacteria that requires a shift in the host microbiota prior to causing disease
c difficile
what is the problem with this postulate:The microorganism must be isolated from a diseased organism and grown in pure culture.
some bacteria are just impossible to grow in culture
ex: leprae and treponema pallidum have never been cultivated as pure cultures in labs
what is the problem with this postulate: The cultured microorganism should cause disease when introduced into a healthy organism.
-it usually relies on the availability of good animal models of human disease
-some other species of bacteria can be used on animals because that specific one that causes disease in humans has no effect on animals
-ex: salmonela
who was stanley falkow
-origin of modern molecular bacterial pathogenesis
-pioneering work from the 60’s on plasmids, antibiotic resistance and molecular mechanisms of infection by e coli, salmonella and pestis
who identified a single genetic locus in the human pathogen yersinia pseudotuberculosus that accounted for the bacterium’s ability to infect cultured animal cells
stanley falkow
how to prove that a particualr gene/protein/lipid acts as a virulence factor
-genes should not be present in bacteria that are avirulent
-disrupting the gene in the virulent strain should attenuate its virulence
-reintroducing the wt gene should restaure virulence (complementation)
-or introducing the gene in an avirulent strain should render it virulent
what are the 3 main factors in bacterial pathogenesis
-bacterial strain variability
-host susceptibility
-enviromental/ecological factors
bacterial pathogenesus: get in
-adhesins
-invasisns
-pili
-flagella
-insect vector
-some bacteria are only pathogens after some type of bite
bacterial pathogenesis; stay in
-capsules
-siderophores, metabolic shifts, biofikm formation, quorum sensing, antibiotic resistance and imhibitors of phagosomal maturation
