The skin microbiome in preadolescents with acne was more diverse than that of controls, and showed some differences from what is known about the microbiome in adults with acne, in a prospective pilot study.
The results have possible treatment implications, suggesting that preadolescents may require a different treatment approach than adults, although additional, larger studies are needed, according to Carrie C. Coughlin, MD, of the division of dermatology in the departments of medicine and pediatrics at Washington University in St. Louis, and her coauthors (Pediatr Dermatol. 2017 Oct 11. doi: 10.1111/pde.13261).
The study enrolled 13 children aged 7-10 years: 5 with acne (3 randomized to treatment with benzoyl peroxide 5% gel or cream and 2 to treatment with tretinoin 0.025% cream), treated for 7-10 weeks; and 8 controls, matched for sex and age.
At baseline, microbiome samples of facial and retroauricular skin among the controls with no acne showed that Streptococcus “was the genus present in highest relative abundance, followed by Propionibacterium,” the authors wrote. In addition to high levels of Streptococcus, those with acne also “had more Staphylococcus and Propionibacterium than controls at all sites before treatment.”
Among those with acne, average Comprehensive Acne Severity Scale values at baseline were 1.3-1.4, among those with acne, dropping to an average of 1 with treatment, which was not statistically significant at follow-up.
But among those with acne, the diversity of cutaneous bacteria decreased with both treatments, down to levels similar to controls, which was a significant effect (P less than .001). This was a “notable” finding, they wrote, “because benzoyl peroxide and tretinoin are known as comedolytic, but tretinoin is not typically thought of as having antibacterial properties like benzoyl peroxide.”
This observation “suggests that topical retinoids may have an effect on the local microbiome through alterations in the cutaneous microenvironment rather than having direct effects on resident microorganisms,” they added.
The authors also pointed out that in the microbiome of adults with acne, Propionibacterium has been found to be more prevalent, indicating that different treatments may be indicated in preadolescents.
The study was funded with a clinical research grant from the American Acne and Rosacea Society.