the mechanism and action of antibiotics Flashcards
bet-lactam and cephalosporin:
TARGET?
example?
target = penicillin binding proteins
examples= penicillin G, flucloxacillin, Tazobactam
what are the 3 central principles of antibiotics?
1) they target processes that humans do not posses
2) they target processes that humans posses but the bacterial versions are sufficiently different
3) the toxicity of antibacterials is greater to bacteria than it is to humans
glycopeptide:
target?
example?
target = C-terminal D-Ala-D-Ala
example = vancomycin, teicoplanin
Cyclic Peptide:
target?
example?
target = C 55-isopropyl pyrophosphate
example = Bacitracin, Polymyxin
phosphoric acid:
target?
example?
target = murA protein
example = fosphomycin
lipopeptides:
target?
example?
target = cell wall stress stimulon
example = daptomycin
what are the 3 main classes of cell wall inhibitors?
1) B-lactams (penicillins and cephalosporin)
2) Vancomycin
3) bacitracin
describe the action of the bacterial cell wall inhibitors?
inhibiting the bacterial cell wall synthesis normally leads to the death of the bacteria
it appears that imbalance in the cell wall architecture triggers bacterial autolysis that kill the cell.
mechanism of action of the glycopeptides?
mechanism of action of peptidoglycan?
glycopeptides -inhibit synthesis of peptidoglycan
peptidoglycan cross linking
what 3 things will penicillin be used to treat?
Gram positive and gram negative cocci
Gram positive Rods (tetanus)
Spirochaetes (syphillis)
what are the 3 types of penicillin?
B-lacatmase resistant penicillin
broad spectrum
extended spectrum
examples of B-lactamase-resitant penicillins?
methicillin
oxacillin
nafcillin
cloxacillin
dicloxacilin
what are examples of broad spectrum penicillins?
Ampicillin and amoxicillin
examples of extended spectrum antibiotics?
Carbenicilin
Ticaracillin
Axlocillin
Piperacillin
describe the structure and function of Carbapenems?
- borad spectrum
- much broader than other B lactams
- generally resistant to the typical beta-lactamases
- carbapenems bing PBPs permentantly acylating them.
- active againstboth gram positive and gram negative
they will not be active against becateria with no cell wall
what are peptidoglycans?
what are they made from?
what gives it its strength?
- the bacterial cell walls are made of various strands of peptidoglycans which are not present in eukaryotes
- they are made multiple amino sugars such as NAG and NAMA
- the cross linking gives it its strength
how do meta lactase function?
what does this lead to?
what is this called?
- they prevent cross linking between side chains of NAMA, meaning that peptide cross-linking can’t occur.
- this leads to the bacterial cell loosing all its strength and being killed.
- this is called bactericidal anti-biotic.
What effect does the penicillin nucleus have?
How can we modify it?
what is this called?
the penicillin nucleus is not active by itself
- by adding things to it, we generate antibiotics.
- this is called semi-synthetic revolution.
what bacteria will penicillin G and v work on?
- staphylococcus
- streptococcus
- enterococcus
- pneumonococcus
- neisseria gonorrhoea
- neisseria menigiditis
what are the 4 mechanisms of actions of bacterial resistance to B-lactam antibiotics?
1) destruction by B-lactamase
2) failure to reach target enzyme- changes to out membrane porins and polysaccharide components of gram negative organisms
3) failure to bind to the trans peptides
4) inhibition of release of autolysins
what are the 4 classes of B-lactamse inhibitors?
A B C D
ACD= uses serine to hydrolyse
B= uses zinc ions to hydrolyse
what compounds are inhibitors of B-lactamse inhibitor for class A?
What is an alternative to B-lactamase resistant antibiotics?
the B-lactam compounds CLAVULANIC acid and SULBACTAM act as strong inhibitors of class A but not C and D.
Co-administration of B-lactamase inhibitors with a B-lactam antibiotic is an alternative approach to the use of B-lactamase-resistant antibiotics