principles of antibiotics Flashcards
what is an antibiotic
agents produced by micro organisms that kill or inhibit the growth of other micro organisms in high dilution
how do antibiotics re
by binding a target site on a bacteria
how to define the class of an antibiotic
the location where the antibiotic binds to the target site on the bacteria will tell you the class
what are antimicrobial
semi synthetic derivatives of antibiotics
examples of antimicrobial
anti fungal
anti bacterial
antihelminthic
antiprotozoal
antiviral agents
what do beta lactam antibiotics do
disrupt peptidoglycan production
by binding covalently and irreversibly to the penicillin binding proteins
cell wall is disrupted and lysis occurs
results in a hypo osmotic or iso osmotic environment
what are beta lactam antibiotics active against
active only against rapidly multiplying organisms
in order to bind to the penicillin binding proteins what must the beta lactam antibiotics do first
diffuse through the bacterial cell wall
what do gram negative organisms have that decreases antibiotic penetration
an additional lipopolysaccharide layer
which bacteria are more suspectible to B lactam
gram positive are more susceptible than gram negative
what causes differences in the spectrum and activity of b LACTAM antibiotic
due to their relative affinity for diff penicillin binding sites
why are beta lactams ineffective in the treatment of intracellular pathogens
because the penicillins poorly penetrate mammalian cells
what are we trying to achieve with antibiotics
they give time and support for the immune system to deal with an infection
describe the bacterial agenda
- attack and enter
- local spread
- multiply
- evade host defences
- shed from body
consequences of bacteria
direct - destroy phagocytes or cells in which bacteria replicate
toxins - exotoxin (protein production), endotoxin (gram negative)
indirect - inflammation, immune pathology
diarrhoea
describe bactericidial antibiotics
the agent kills the bacteria
they are antibiotics that inhibit cell wall synthesis
when are bactericidal antibiotics useful
- if poor penetration (endocarditis)
- difficult to treat infections
- need to eradicate infection quickly (meningitis)
describe bacteriostatic antibiotics
prevent growth of bacteria - inhibitory to growth
antibiotics that inhibit protein synthesis, dna replication or metabolism
reduce toxin production and endotoxin surge less likely
what is MBC/MIC
a ratio of minimum bactericidal concentration to minimum inhibitory concentration
what must the antibiotic do to work effectively
it should remain at the binding site for a suffficient period of time in order for the metabolic processes of the bacteria to be sufficiently inhibited
what is related to concentration within the microorganisms
the drug must not only attach to its binding target but also must occupy an adequate number of binding sites
what are the 2 major determinants of anti bacterial effects
the concentration
and the time
that the antibiotic remains on these binding sites
what is time dependent killing
key parameter isn’t he time that serum concentrations remain above the MIC during the dosing interval
what is concentration dependent killing
key parameter is how high the concentration is above MIC
