Modulation of skin microbiome in acne patients by aminolevulinic acid-photodynamic therapy

Background: Aminolevulinic acid-photodynamic therapy (ALA-PDT) has been an effective treatment for moderate to severe acne. However, the effect of ALA-PDT on skin microbiome in acne patients should also be examined.. Aim: To examine the composition, diversity, and resilience of skin microbiome in acne patients before and after ALA-PDT. Method: A prospective study was conducted on five patients with moderate to severe acne. All patients underwent a 5% ALA-PDT at a two-week interval for four sessions. Epidermal and follicular samples of acne patients were acquired for 16S rRNA gene amplicon metasequencing at baseline and before the final session. Result: ALA-PDT inhibited Cutibacterium acnes of follicular microbiome in acne. Follicular residential bacteria, mainly Bacillus and Lactococcus, rose in abundance after PDT. ALA-PDT increased the diversity of skin microbiome in acne and clustered follicular microbiome toward epidermal microbiome, both taxonomically and functionally. Conclusion: ALA-PDT exerts its therapeutic effect on acne partially through inhibiting C. acnes and modulating the composition and potential function of skin microbiome in acne.