Antibiotics - Mechanism of Action

Question 1

What antibiotics prevent peptidoglycans cross linking to form the bacteria cell wall

Answer 1

Penicillins
Cephalosporins
Carbapenems

Question 2

What antibiotic affects peptidoglycan synthesis?

Answer 2

Glycopeptides (e.g. vancomycin)

Question 3

What antibiotics act on the 30S subunit in the ribosome to prevent protein synthesis in bacteria?

Answer 3

Aminoglycosides
Tetracyclines

Question 4

What antibiotics act on the 50S subunit in the ribosome to prevent protein synthesis in bacteria?

Answer 4

Macrolides
Chloramphenicol
Clindamycin
Linezolid

Question 5

What antibiotics target the folic acid synthesis pathway? What enzymes do they target?

Answer 5

Trimethoprim - Dihydrofolate reductase
Sulphonamides - Dihydropteroate synthase

Question 6

What enzyme does Rifampicin target?

Answer 6

RNA polymerase

Question 7

What enzyme do Quinolones target?

Answer 7

DNA Topoisomerase
=> inhibits DNA synthesis

Question 8

What is the mechanism of action of Metronidazole?

Answer 8

Damages DNA

Question 9

Mechnism of action of macrolides

Answer 9

inhibit bacterial protein synthesis by blocking translocation

(technically bacteriostatic)

Question 10

Adverse effects of macrolides

Answer 10

QT prolongation
GI side-effects
cholestatic jaundice
P450 enzyme inhibitor

azithromycin is associated with hearing loss and tinnitus

Question 11

What drug should be stopped whilst taking a macrolide

Answer 11

Statins

• Macrolides inhibit CYP3A4 that metabolises statins
• increases the risk of myopathy and rhabdomyolysis.

Question 12

Mechnism of action of quinolones (e.g. Ciprofloxacin/levofloxacin)

Answer 12

inhibiting DNA synthesis (bactericidal)
- inhibit topoisomerase II (DNA gyrase) and topoisomerase IV

Question 13

Adverse effects of quinolones

Answer 13

• lower seizure threshold
• tendon damage/ rupture
• lengthens QT interval

Question 14

When should quinolones be avoided?

Answer 14

• women who are pregnant or breastfeeding
• G6PD