Principles Of Antibiotics 28.11.23 Flashcards
Define antibiotics
agents produced by micro-organisms that kill or inhibit the growth of other micro-organisms in high-dilution.
Define antimicrobial, with an example.
Defined as points of biochemical reaction crucial to the survival of the bacterium e.g. penicillin-binding proteins in cell wall
Does the crucial binding site vary with antimicrobial class?
YES!
Slide 13
Beta lactams are less able to deal with gram negative or gram positive bacteria? Why?
Beta lactams are less able to deal with gram negative as gram negative organisms have an additional lipopolysaccharide layer that decreases antibiotic penetration
How did beta lactam antibiotics work?
Disrupt peptidoglycan production by binding convalently and irreversibly to the ‘penicillin binding proteins, cell wall is disrupted and lysis occurs, results in hypo-osmotic or iso-osmotic environment, active only against replicas multiplying organisms
What are the 2 ways antibiotics work?
Bactericidal Antibiotics - kills the bacteria
Bacteriostatic antibiotics - prevent growth of bacteria (tend to be the ones which stop DNA replication)
Slide 28
Does lowest MIC equal best antibiotic
No! drug must not only attach to its binding target but also must occupy an adequate number of binding sites, which is related to its concentration within the microorganism.
to work effectively, the antibiotic should remain at the binding site for a sufficient period of time in order for the metabolic processes of the bacteria to be sufficiently inhibited.
The two major determinants of anti bacterial effects are the concentration and the time that the antibiotic remains on these binding sites
What are time dependent killing antibiotics
Key parameter is the time that serum concentrations remain above the MIC during the dosing interval:
t>MIC
beta-lactams (penicillins, cephalosporins, carbapenems, monobactams),
clindamycin,
macrolides
oxazolidinones
What are concentration - dependant killing antibiotics
Key parameter is how high the concentration is above MIC
peak concentration/MIC ratio
aminoglycosides
quinolones
Why do bacteria develop intrinsic resistance?
All subpopulations of a species will be equally resistant
Why do bacteria develop acquired resistance?
A bacterium which was previously susceptible obtains the ability to resist the activity of a particular antibiotic
Only certain strains or subpopulations of a species will be resistant
