2.18 - Antimicrobials for Skin Infections

Question 1

Drug used for topical treatment of impetigo due to Staph. Aureus and Strep Pyo.

Answer 1

Mupirocin (Bactroban)

Question 2

Drug that is effective against MRSA (as well as a wide range of Gr+ and some Gr-) and can be used to eradicate carriage state with MRSA via nasal application (decolinzation)

Answer 2

Mupirocin (Bactroban)

Question 3

Drug used for non-purulent cellulitis “erysipelas”

- Note: What organism is responsible for erysipelas?

Answer 3

Drug of Choice = Penicillin

- Organism = Group A Strep (ex. Strep Pyo)

Question 4

Drug used for purulent cellulitis

- Note: What organism is responsible?

Answer 4

Drug of Choice: Oral and IV Vancomycin (Televancin = vancomycin derivative)
- Organism = MRSA

Question 5

If you want to treat both Group A strep and MRSA, what combinations do you give?

Answer 5

TMP/SMX (Sulfa), tetracycline WITH Beta-lactam antimicrobial

Question 6

What is the most commonly used topical antimicrobial agent in BURNS

Answer 6

Silver Sulfadiazine

Question 7

MOA of Bacitracin

Answer 7

MOA: Bacitracin inhibits the function of a lipid transport molecule in bacteria which carries the building blocks of the peptidoglycan bacterial cell wall outside the cell membrane for construction. Unique MOA

Question 8

Spectrum of Bacitracin

Answer 8

Spectrum: Gr+ bacteria (Staph; Strep; Clostridium)

Question 9

Bacitracin Toxicity

Answer 9

Toxicity: contact dermatitis from topical use;

nephrotoxicity from systemic use

Question 10

Bacitracin Uses

Answer 10

Uses:

topical application (combined w/ other antimicrobials that have Gr- activity—e.g. neomycin, polymyxin B);

used in surgical irrigation solutions (use not supported by medical literature à plain saline irrigation just as effective as soln w/ antimicrobial agents)

Question 11

Polymixin B, Colistin: MOA

Answer 11

They interact electrostatically with the outer membrane (like soap) of Gr- bacteria and competitively displace divalent cations from the membrane lipids, specifically calcium and magnesium. This disrupts the outer membrane and changes its permeability. The end result is leakage of cell content, cell lysis and death.

Question 12

Polymixin B, Colistin: Spectrum

Answer 12

G- Bacteria

Question 13

Bugs that are associated with beta-lactamase production (that were mentioned) + What is the treatment progression?

Answer 13

Enzymatic = β-lactamase production

1) ESBL (extended spectrum β-lactamases)
2) KPC (Klebsiella pneumoniae carbapenemases)
3) NDM (New Delhi Metallo-β-lactamases)

• First Carbapenem but if they produce carbapenemases, then we can give them tigecycline OR colistin!

Question 14

What are the 4 antivirals useful in HSV and VZ infection

Answer 14

Acyclovir
Famciclovir
Valacyclovir
Peniciclovir = only topical (cold sores)

Question 15

Drug used in the treatment of Tinea Unguium or Onychomycosis

Answer 15

Terbafine (Turban man).

- Note: can also give itraconazole

Question 16

MOA of Terbinafine

Answer 16

allylamine antifungal inhibits biosynthesis of ergosterol (essential component of fungal cell membrane) via inhibition of squalene epoxidase enzyme.

This results in fungal cell death primarily due to the increased membranepermeability mediated by the accumulation of high concentrations of squalene but not due to ergosterol deficiency.

Question 17

Toxicity associated with Terbinafine

Answer 17

Hepatoxocity: recommend that pts screened for preexisting liver dz. if liver damage, no Terbinafine