Clindamycin, Tetracyclines & Quinolone

Question 1

What is the mechanism of action of clindamycin?

Answer 1

inhibits protein synthesis by binding to the bacterial 50S ribosome

Question 2

What does clindamycin cover?

Answer 2

Gram + cocci
Gram - bacilli
can be topical, vaginal cream

Question 3

What adverse effects are of concern in clindamycin?

Answer 3

pseudomembranous colitis can cause clostridium difficile

Question 4

What makes a tetracycline susceptible to dehydration?

Answer 4

having a hydroxyl group on the C6 position

Question 5

what is the toxic metabolite that occurs due to dehydration & epimerization of tetracyclines?

Answer 5

4-epianhydrotetracycline

Question 6

What is mechanism of action of tetracyclines?

Answer 6

binds to the 30S ribosomal subunit and inhibits the codon-anticodon interaction via blocking the attachment of the aminoacyl-tRNA to the A site

Question 7

What adverse effects are of concern in Chloramphenicol?

Answer 7

aplastic anemia, occurs ~3-4 months after treatment

Question 8

What are the first generation quinolones and what do they cover?

Answer 8

oxolinic acid, nalidixic acid
-gram - organisms

Question 9

What are the second generation quinolones and what do they cover?

Answer 9

ciprofloxacin (most potent quinolone)
-gram - organisms

Question 10

What are the third and fourth generation quinolones and what do they cover?

Answer 10

levofloxacin, moxifloxacin
-most gram - but some gram +

Question 11

What is the mechanism of action of quinolones?

Answer 11

inhibits religation after a double strand DNA break (like topoisomerase II)
-creates a 4-base stagger causing the strands to physically be too far apart to be able to religate

Question 12

What are the mechanisms of resistance with fluoroquinolones?

Answer 12

-efflux pumps(prevents entrance into porins), decreased permeability, enzyme mutation (alters binding affinity)