Dapsone acne treatment demonstrates antimicrobial activity

WASHINGTON — Topical dapsone gel showed in vitro activity against gram-positive cocci, according to data presented at the American Academy of Dermatology annual meeting.

“Topical dapsone gel is a sulfone antibiotic approved for acne treatment,” George G. Zhanel, PharmD, PhD, professor at Manitoba University College of Medicine, and colleagues wrote. “No microbiology studies were conducted during dapsone gel clinical trials, and it is unclear whether dapsone has antimicrobial activity with clinical relevance in dermatology [or] dapsone could affect the normal microbiome of facial skin where it is usually applied.”

George G. Zhanel

To assess in vitro activity of dapsone against gram-positive and gram-negative bacteria in the CANWARD study, the researchers used 15 medical centers in Canada to obtain 3,511 isolates from any wounds, blood, urine, and respiratory tract. They used the isolates to prepare minimum inhibitory concentration (MIC) panels.

The researchers found that dapsone had poor activity against gram-negative bacilli, as most MICs of 50% or 80% were 512 µg/mL or greater. However, they found that dapsone had good activity against gram-positive cocci; strains of Staphylococcus epidermis had MICs of 32 µg/mL and 64 µg/mL and strains of Enterococcus faecalis demonstrated MICs of 8 µg/mL, 16 µg/mL, 32 µg/mL, and 64 µg/mL. In addition, strains of Streptococcus agalactiae and Streptococcus pyogenes had MICs that ranged from 4 µg/mL to 64 µg/mL.

Previous data showed that dapsone remains at a very high concentration on the skin, a strength anticipated to affect the skin flora of an acne patient, the researchers wrote.

“Topically dapsone gel has antimicrobial activity and at the concentrations attained on the skin when it is used clinically, it is quite likely that it affects the normal microbiome on the face contributing to the development of antimicrobial resistance and bacterial selection,” Zhanel told Infectious Diseases in Children. – Will Offit

Reference:
Zhanel GG, et al. Abstract 3523. Presented at: American Academy of Dermatology Annual Meeting; March 4-8, 2016; Washington D.C.

Disclosure: Infectious Diseases in Children was unable to confirm relevant financial disclosures at the time of publication.