Antimicrobials - Cell Membrane Toxins

Question 1

What is the mechanism of action of daptomycin?

Answer 1

• insertion of lipophilic tail through teichoic acid backbone of the cell membrane of G+ bacteria, forming a channel for leakage of ions
• only effective against G+ bacteria!

Question 2

What is the antibacterial spectrum of daptomycin?

Answer 2

• vancomycin resistant enterococci (VRE)
• vancomycin resistant S. aureus (VRSA)
• in patients with allergies to vanco and lactams

Question 3

What is the mechanism of colistin?

Answer 3

• binds to lipopolysaccharides and causes disruption of outer cell membrane with leakage of ions
• only effective against G- bacteria!

Question 4

What are the adverse reactions you should watch out for when prescribing daptomycin?

Answer 4

• drug allergy

- risk of rhabdomyolysis (esp > 7 days)

Question 5

What are the adverse reactions to colistin?

Answer 5

• highly nephrotoxic

Question 6

When is use of colistin indicated?

Answer 6

• G- bacteria (usually Pseudomonas in CF) that is resistant to all other antibacterials