plasmid-mediated mechanisms of bacterial drug resistance

Question 1

Mechanism for penicillin resistance

Answer 1

• there are 2 components of the cell wall: NAG and NAM; PBP cross-links NAM residues, strengthening wall.
• penicillin is a β-lactam antibiotic; works by binding PBP and activating them
• production of β-lactamase –> cleavage of β-lactam rings = resistance to penicillins

Question 2

Mechanism for resistance to aminoglycosides

Answer 2

• production of acetyltransferase, adenosyltransferase or phosphotransferase –> inactivation of drug by acetylation, adenosylation or phosphorylation

Question 3

Mechanism for resistance to chloramphenicol

Answer 3

• production of acetyltransferase –> inactivation of drug by acetylation

Question 4

Mechanism for resistance to tetracyclines

Answer 4

increased efflux out of cell

Question 5

Mechanism for resistance to cephalosporins

Answer 5

• there are 2 components of the cell wall: NAG and NAM; PBP cross-links NAM residues, strengthening wall.
• cephalosporins are a β-lactam antibiotic; work by binding PBP and activating them
• production of β-lactamase –> cleavage of β-lactam rings = resistance to cephalosporins

Question 6

Mechanism for resistance to sulfonamides

Answer 6

• active export out of cell and lowered affinity of enzyme

Question 7

Mechanism for resistance to vanocomycin

Answer 7

• ligase produces cell wall pentapeptides that terminate in D-alanine-D-lactate, which will not bind to the drug –> vancomycin can’t work.