# Skin Microbiome Under Topical and Systemic Therapeutics in Atopic Dermatitis, a Cross‐Sectional Analysis From ProRaD

## TL;DR

This study explores how different treatments for atopic dermatitis affect the skin microbiome, finding that systemic treatments reduce Staphylococcus aureus levels compared to topical treatments.

## Contribution

The study reveals that systemic immunomodulatory treatment in moderate AD reduces S. aureus abundance compared to topical treatment.

## Key findings

- Systemic therapy in moderate AD is associated with lower S. aureus abundance compared to local treatment.
- AD severity strongly correlates with S. aureus abundance in lesional skin.
- Dupilumab treatment tends to reduce S. aureus abundance compared to conventional immunosuppressive treatments.

## Abstract

Atopic dermatitis is a common and chronically relapsing inflammatory skin disease. Long‐term management of the heterogeneous disease entity challenges patients and physicians globally. In our exploratory cross‐sectional study, we investigated the correlation of local and systemic therapies with skin microbial changes in patients with atopic dermatitis (AD). We cross‐sectionally evaluated the ProRaD cohort's study data between 2017 and 2019 at the Augsburg and Bonn study centres. Our analysis encompassed lesional skin microbiome swabs and medication data from 464 participants between 0 and 84 years of age. For comparative analysis, patients were grouped by disease severity. Categorisation of treatment levels was performed based on the treatment guideline for atopic dermatitis. In moderate AD, we found systemic therapy associated with a significantly lower relative abundance of
S. aureus
compared with patients receiving local treatment. However, skin microbial diversity did not significantly differ between therapeutic regimens. Furthermore, we observed a strong correlation between AD severity and relative
S. aureus
abundance in lesional skin swabs. Treatment choice, however, did not always align with disease severity, with substantial proportions of severely affected individuals receiving basic treatment only. Across all disease severities, patients receiving dupilumab tended to show a reduced
S. aureus
abundance compared to those receiving conventional immunosuppressive treatment and systemic glucocorticoids. Our findings align with recent research indicating reduced
S. aureus
abundance after systemic treatment with dupilumab, while topical anti‐inflammatory treatment alone does not seem to affect skin microbial composition. Further research is needed to elucidate the microbial–immunological interactions and their implications for AD treatment.

Therapeutically induced skin microbiome modulation in moderate to severe atopic dermatitis. Our anaysis from the ProRaD cohort (n = 464) showed that patients under systemic immunomodulatory treatment and moderate atopic dermatitis (AD) posses less Staphylococcus aureus relative abundance on lesional skin compared to topically treated patients. We could additionally reveal a strong correlation between disease severity (SCORAD) and S. aureus abundance. Our findings support the microbiome modulating effect of systemic immunomodulatory treatment in moderate‐to‐severe AD.