25. Mode of Action of Antimicrobials

Question 1

What is the purpose of therapeutic drug monitoring?

Answer 1

Ensures drug is effective but not excessively toxic

Question 2

Why are antimicrobials that affect the cell wall much more effective in gram + bacteria?

Answer 2

Gram - have an outer membrane and a much thinner cell wall

Question 3

What is the name of the enzyme that builds peptidoglycan chains?

Answer 3

Transpeptidase

Question 4

What is the mechanism of action of B lactams?

Answer 4

Target transpeptidase to prevent cross-linking of peptidoglycans

Question 5

What is the mechanism of action of glycopeptides?

Answer 5

Bind to side chains and prevent cross-linking

Question 6

What methods of resistance are there to B lactams?

Answer 6

Bacteria can produce enzymes that destroy the B lactam ring
EBSL can destroy B lactam of different antibiotic structures
Cabapenemases can destroy B lactam ring of carbapenems

Question 7

What is the function of a B-lactamase inhibitor?

Give an example

Answer 7

Mop up B lactamase to ensure the antibiotic still works

Eg. Co-amoxiclav

Question 8

What is the mechanism of action of quinolones in gram - bacteria?

Answer 8

Inhibits DNA gyrase which inhibits DNA replication

Question 9

What is the mechanism of action of quinolones in gram + bacteria?

Answer 9

Targets topoisomerase 4 to inhibit DNA replication

Question 10

What is the mechanism of action of rifampicin?

Answer 10

Binds to RNA polymerase to stop translation

Question 11

Why does rifampicin have no gram - activity?

Answer 11

Rifampicin is hydrophobic

Question 12

What is the mechanism of action of anti-metabolites?

Answer 12

Inhibit enzymes which are used to make folic acid

Nucleotides and therefore DNA can’t be produced

Question 13

Name 2 classes of protein synthesis inhibitors

Answer 13

Aminoglycosidases

Tetracyclines

Question 14

What is the mechanism of action of gentamicin and doxycycline?

Answer 14

Inhibit binding of tRNA to the 30s ribosome

Question 15

What is the mechanism of action of chloramphenicol?

Answer 15

Inhibit binding of tRNA to 50s ribosome

Question 16

What is the mechanism of action of macrolides?

Answer 16

Inhibit RNA-dependent protein synthesis at 50s

Question 17

What is the mechanism of action of linezolid?

Answer 17

Bind to 50s ribosome

Question 18

What is the mechanism of action of daptomycin?

Answer 18

Binds to bacterial membranes and causes depolarisation of membrane potential
This inhibits the production of protein, DNA and RNA

Question 19

What side effect is associated with rifampicin?

Answer 19

oral contraceptive failure

Question 20

What side effect is associated with clarithromycin?

Answer 20

Increases digoxin levels (used for atrial fib)

Question 21

Which antibiotics interact with warfarin to increase coagulation?

Answer 21

Ciprofloxacin
Metronidazole
Clarithromycin

Question 22

Which antibiotic interacts with warfarin to decrease coagulation?

Answer 22

Rifampicin

Question 23

Which class has nephrotoxic effects with amphotericin B?

Answer 23

Aminoglycosides

Question 24

What antibiotic interacts with antacids?

Answer 24

Rifampicin

Question 25

What antibiotic is associated with pneumonitis?

Answer 25

Nitrofurantoin

Question 26

What side effect is associated with isoniazid?

Answer 26

Hepatitis

Question 27

What side effects are associated with aminoglycosides?

Answer 27

Ototoxicity

Nephrotoxicity

Question 28

What side effect is associated with chloramphenicol?

Answer 28

Bone marrow suppression