Antimicrobials

Question 1

What is a bacteriostatic antibiotic?

Answer 1

BACTERIOSTATIC antibiotics inhibit the growth and replication of bacteria (non-lethal)
Eg. inhibitors of folate synthesis, quinolones

Question 2

What is a bactericidal antibiotic?

Answer 2

BACTERICIDAL antibiotics kill bacteria (lethal), but note that at low concentration these antibiotics may only be bacteriostatic
Eg. penicillin, aminoglycosides

Question 3

What is the mechanism of action for penicillin antibiotics?

Answer 3

Inhibition of cell wall synthesis

Question 4

What is the mechanism of action for cephalosporin antibiotics?

Answer 4

Inhibition of cell wall synthesis

Question 5

What is the mechanism of action for carbapenem antibiotics?

Answer 5

Inhibition of cell wall synthesis

Question 6

What is the mechanism of action for glycopeptide antibiotics?

Answer 6

Inhibition of cell wall synthesis

Question 7

What are the main antibiotic classes that work by the inhibition of bacterial cell wall synthesis?

Answer 7

β-lactam antibiotics:

• Penicillins
• Cephalosporins
• Carbapenems
• Monobactams

Glycopeptides

Polymyxins

Question 8

What is the mechanism of action for quinolone antibiotics?

Answer 8

Inhibition of DNA gyrase

Question 9

What is the mechanism of action for rifamycin antibiotics?

Answer 9

Inhibition of RNA polymerase

Question 10

What are the main antibiotic classes that work by the inhibition of bacterial nucleic acid synthesis?

Answer 10

Folate antagonists
Quinolones
Rifamyins

Question 11

What are the main antibiotic classes that work by the inhibition of bacterial protein synthesis?

Answer 11

50S subunit:
Macrolides
Lincosamide (Clindamycin)
Oxazolidinones (Linezolid)
Chloramphenicol (Chloramphenicol)

30S subunit:
Tetracyclines
Aminoglycosides

Question 12

What is mechanism of action for macrolide antibiotics?

Answer 12

Inhibition of the 50S ribosomal subunit

Question 13

What is mechanism of action for tetracycline antibiotics?

Answer 13

Inhibition of the 30S ribosomal subunit

Question 14

What is mechanism of action for aminoglycoside antibiotics?

Answer 14

Inhibition of the 30S ribosomal subunit

Question 15

What is the Minimum Inhibitory Concentration (MIC) of a bacterial colony?

Answer 15

MINIMUM INHIBITORY CONCENTRATION (MIC) is the minimum in vitro concentration which an antibiotic can inhibit growth

Question 16

What is the Minimum Bactericidal Concentration (MBC) of a bacterial colony?

Answer 16

MINIMUM BACTERICIDAL CONCENTRATION (MBC) is the minimum in vitro concentration which an antibiotic can kill bacteria

Question 17

Antimicrobials that are potent CYP3A4 inducers

Answer 17

Rifampicin

Question 18

Antimicrobials that are potent CYP3A4 inhibitors

Answer 18

Ketoconazole

Clarithromycin

Question 19

What is meant by an antibiotic with concentration-dependent killing?

Answer 19

CONCENTRATION dependent killing (Cmax/MIC ratio) means drug PK needs to reach high drug concentration above the MIC

Question 20

What is meant by an antibiotic with time-dependent killing?

Answer 20

TIME dependent killing (AUC/MIC ratio) means drug PK needs to spend time above the MIC

Question 21

3 common mechanisms of antimicrobial resistance (AMR)

Answer 21

1. Production of enzymes
2. Changes to target sites or metabolic pathways
3. Efflux pumps