Classes of Antibiotics and Mechanisms of Resistance Flashcards
2 SDLs in one
How to cell wall targeting antibiotics work? Give examples
Inhibit the production of peptidoglycans that form cell walls.
e.g. prnicillins, cephalosporins and bacitracins
How do penicillins work
Penicillins Acts on cell walls of growing bacteria inhibiting the enzyme responsible for the cross-linking between layers of peptidoglycans
How do cephalosporins work
Cephalosporins similar activity to Penicillin
How do bacitracins work
Bacitracin Interacts with bacterial cell membrane to prevent transfer of structural cell wall units
Describe how membrane targeting antibiotics work and give examples
Damage the membrane (mostly gram –ve) resulting in loss of osmotic control = loss of K ions and eventually cell death.
e.g. polymyxins
How do Antimetabolites or substrate analogue antibiotics work ? Give examples
Compete with metabolites forming non functional products. This prevents the further growth of such bacteria that require these substances
e.g. Sulphonamides
As many of these metabolites are only required for growth this kind of antibiotic can only inhibit growth and not kill bacteria.
How do sulphonamides work?
Compete with Para-aminobenzoic acid (PABA) in the formation of folic acid .
How do protein synthesis inhibitors work and give examples?
Interact with ribosomes either binding to the larger 50S chain (inhibiting protein synthesis) or the smaller 30S subunit (causing mis-coding of proteins and inhibition of protein elongation)
30S Streptomycin, Neomycin, Gentomycin (all aminoglycosides and bacteriocidal)
50S Chloramphenicol and Erythromycin
How do streptomycin, neomycin and gentomycin work?
Causing mis-coding of proteins and inhibition of protein elongation
Describe how antimicrobials that interfere with DNA work and give examples
Interference with DNA will result in effects on protein synthesis and therefore functioning and growth of the cell leading to cell death.e.g. quinolones
How do quinolones work
e.g. enroflaxin inhibit DNA Gyrase enzyme leading to loose coiling of DNA around RNA core. This leads to degradation of DNA into loose non-functional fragments by the action of endonucleases
Would resistance to one ribosome binding drugs lead to resistance to another?
Yes see above for details of the 50S and 30S binding antibiotics resistance to any in each of these categories could have the potential to develop resistance in any number of others in these groups.
How can point mutations lead to resistance to an antibiotic?
• Results in the changing of the amino acids that form a protein and therefore potentially the proteins structure, this could prevent binding of the antibiotic to its target site resulting in prevention of the activity of the antibiotic.
Why could efflux systems lead to resistance to multiple antibiotics while an enzyme to degrade an antibiotic may only lead to resistance to that single group?
Efflux systems are able to remove all toxic substrates (antibiotics) from the cell preventing them from binding and acting on the cell regardless of their route of action.
Enzymes have to be more specific (specific size and shape of active site to fit with the antibiotic).
What is clavulanic acid?
Clavulanic acid is a beta lactam that functions as a beta lactamase inhibitor, it works well with penicillin with is normally inactivated by Beta lactamase.
