Antibiotics - Protein Synthesis Inhibitors

Question 1

Name some of the important (general) protein synthesis inhibitors. (5)

Answer 1

• Aminoglycosides
• Tetracycline
• Chloramphenicol
• Macrolides
• Lincosamides

Question 2

List some specific aminoglycosides.

Answer 2

Streptomycin, neomycin, gentamycin, tobramycin, amikacin

Question 3

Mode of action for aminoglycosides?

Answer 3

Bind to 30S ribosome, block initiation by preventing attachment of tRNA

Question 4

Resistance to aminoglycosides?

Answer 4

Altered P12 ribosomal protein, aminoglycosides, altered permeability (Streptococci)

Question 5

Uses for aminoglycosides?

Answer 5

G- enterics (often in synergy with cephalosporins or penicillins - facilitate entry of the aminoglycosides)

Question 6

List some specific tetracyclines.

Answer 6

Doxycycline, tigecycline

Question 7

Mode of action of tetracyclines?

Answer 7

Inhibits binding of aa-tRNA to the A-site of the ribosome (30S)

Question 8

Resistance to tetracyclines?

Answer 8

Efflux pumps

Question 9

Uses for tetracyclines?

Answer 9

Treatment of rickettsia, chlamydia, mycoplasmas

Question 10

List some side effects of tetracyclines.

Answer 10

Toxicity, dizziness, ringing in ears, fluorescent teeth and possible bone damage in newborns, pregnancy class D (do not use!!!)

Question 11

Mode of action of chloramphenicol?

Answer 11

Inhibits peptidyl transferase reaction (50S)

Question 12

Resistance to chloramphenicol?

Answer 12

Chloramphenicol acetyl transferase (CAT)

Question 13

Uses for chloramphenicol?

Answer 13

No longer a drug of choice…resistance and toxicity have been established.

Question 14

List some examples of macrolides.

Answer 14

Erythromycin, clarithromycin, azithromycin

Question 15

Mode of action of macrolides?

Answer 15

Binds to rRNA and inhibits translocation (50S)

Question 16

Resistance to macrolides?

Answer 16

Methylation of rRNA

Question 17

Uses for macrolides?

Answer 17

G+ and some G-

Question 18

Side effects of macrolides?

Answer 18

Prolonged QT interval (Torsades de Pointes) and increased risk of cardiovascular death

Question 19

What is an example of a lincosamide?

Answer 19

Clindamycin

Question 20

What is the mode of action of lincosamides?

Answer 20

Same as macrolides! That was easy! (Binds to rRNA and inhibits translocation at 50S)

Question 21

Uses for lincosamides?

Answer 21

Anaerobes (Bacteroides) and anti-malarial

• Does NOT penetrate CNS
• Long-term clindamycin can be linked with C. diff colonization
• One-time use majorly disrupts native flora

Question 22

Other protein synthesis inhibitors:

Nitrofurantoin

Answer 22

Inhibits 30S, used vs. UTI and concentrated in urine

Question 23

Other protein synthesis inhibitors:

Mupirosin

Answer 23

Inhibits ile-tRNA synthase, used topically vs. G+

Question 24

Other protein synthesis inhibitors:

Streptogramins (Synercid)

Answer 24

Quinupristin + dalfopristin

Inhibits 50S, used to treat VRE and VRSA

Question 25

Other protein synthesis inhibitors:

Oxazolidinones (Linezolid)

Answer 25

Inhibits 50S, used to treat VRE and MRSA

Question 26

Other protein synthesis inhibitors:

Methenamine

Answer 26

Releases formaldehyde in acidified urine, used to treat UTI