antibiotics symposium 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 work?
by binding a target site on a bacteria
this crucial binding site will vary with the antibiotic class
what are antimicrobials?
semi-synthetic derivatives of antibiotics
Defined as points of biochemical reaction crucial to the survival of the bacterium
HOWEVER IN PRACTISE
ANTIBIOTIC= ANTIBRACTERIAL
give examples of antimicrobials
antifungal, antibacterial, antihelminthic,
antiprotozoal and antiviral agents
what do beta lactam antibiotics do ?
disrupt peptidoglycan production by binding convalently and irreversibly to the penicillin binding proteins- causing cell Wass to disrupt-lysis occurs- resulting in hypo-osmotic or iso-osmotic environment
what are beta lactic antibodies active against?
only rapidly multiplying organisms
in order to bind to the penicillin binding proteins, what must the beta lactam antibodies do first?
diffuse through the bacterial wall
what do gram negative organisms have that decreases antibiotic penetration?
an additional lipopolysaccharide layer
what are the differences in the activity of beta lactam antibodies due to?
their relative affinity for different Penicillin Binding Proteins
why are beta lactams innefective in the treatment of intracellular pathogens?
because penicillins poorly penetrate mamlilan cells
describe the bacterial agenda
- attach and enter
- local spread
- multiply
- evade host defences
- shed from body
what are the direct consequences of bacteria?
destroy phagocytes or cells in which bacteria replicate
what are the indirect consequences of bacteria?
inflammation- e.g necrotic cells
immune-pathology- e.g antibody
what are the toxin related consequences of bacteria?
Exotoxin - Protein production
Endotoxin - Gram negative
what are bactericidal antibiotics?
agents that kill the bacteria
are antibiotics that inhibit cell wall synthesis
when are bactericidal antibiotics useful?
Useful if poor penetration (Endocarditis),
when it is difficult to treat infections or need to eradicate infection quickly (meningitis)
define bacteriostatic antibodies
defined as a ratio of Minimum Bactericidal Concentration (MBC) to Minimum inhibitory Concentration (MIC) of > 4
Antibiotics that Inhibit protein synthesis, DNA replication or metabolism
what do bacteriostatic antibodies do?
Reduce toxin production and Endotoxin surge less likely
they prevent growth of bacteria
what are the two major detriments of anti bacterial effects?
concentration
time
( that the antibiotic remains on these binding sites
what does the antibiotic drug do?
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.
in order to work effectively what does the antibiotic have to do?
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.
describe time dependent killing
Key parameter is the time that serum concentrations remain above the MIC during the dosing interval
t>MIC
describe concentration dependant killing
Key parameter is how high the concentration is above MIC
peak concentration/MIC ratio
what is the antibiotic dependant on?
pharmokinetics- The movement of a drug from its administration site to the place of its pharmacologic activity and then its elimination from the body
