Antimicrobials - Protein Synthesis Inhibitors

Question 1

Which antimicrobials bind to the 30S ribosome? Which bind to the 50S?

Answer 1

30S: aminoglycosides (gentamicin, tobramycin), tetracyclines (doxycycline)

50S: macrolides (azithromycin), linezolid

Question 2

Which antimicrobials interfere with formation of the initiation complex?

Answer 2

aminoglycosides - misreading of code and incorporation of wrong AA

linezolid

Question 3

Which antimicrobials interfere with amino-acid incorporation?

Answer 3

tetracyclines, dalfopristin/quinupristin

Question 4

Which antimicrobials interfere with formation of the peptide bond?

Answer 4

chloramphenicol

Question 5

Which antimicrobials interfere with translocation?

Answer 5

macrolides, clindamycin

Question 6

What is the bacterial spectrum of aminoglycosides?

Answer 6

bactericidal against aerobic or facultative aerobic G- rods (dependent on O2 mediated uptake)

Question 7

What is the mechanism of action of tetracyclines (doxycycline) and what pathogens are they useful for?

Answer 7

• blocks access of tRNA anticodon to codon (bacteriostatic)

- used for intracellular pathogens (Mycoplasma, Chlamydia, Legionella, Rickettsia)

Question 8

What is the mechanism of action of macrolides (erythromycin, azithromycin, clarithromycin) and what pathogens are they useful for?

Answer 8

• prevents translocation (bacteriostatic)

- used for intracellular pathogens, G+ cocci

Question 9

What is the mechanism of action and spectrum of linezolid?

Answer 9

• inhibits formation of initiation complex

- use: G+ organisms, VRSA, VRE, drug resistant pneumococci

Question 10

What is a side effect of using linezolid for greater than 2 weeks?

Answer 10

Agranulocytosis

Question 11

What is the mechanism and spectrum of clindamycin?

Answer 11

• inhibits incorporation of new AAs into growing peptide chain
• spectrum: G+ cocci and all anaerobes (except for C. difficile)