Publication details
Modulating the Skin Microbiome in Atopic Dermatitis: A Six-Month Comparative Study of JAK Inhibitors, Dupilumab, Cyclosporine A, and Topical Corticosteroids
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| Year of publication | 2026 |
| Type | Conference abstract |
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| Description | Introduction Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by epidermal barrier dysfunction, immune dysregulation, and alterations of the skin bacteriome. Overgrowth of Staphylococcus aureus is closely associated with disease severity and exacerbations. Although targeted systemic therapies have substantially improved AD outcomes, their differential effects on the skin bacteriome remain insufficiently characterized. This study aimed to compare the effects of targeted and conventional anti-inflammatory therapies on clinical severity and skin bacteriome composition over six months under standardized conditions. Materials and Methods This prospective pilot study included 60 patients with atopic dermatitis treated with Janus kinase (JAK) inhibitors, dupilumab, cyclosporine A, or topical corticosteroids (intermittently used methylprednisolone aceponate). Skin bacteriome samples were collected at baseline and after 3 and 6 months of therapy. Microbial composition was analyzed using 16S rRNA gene amplicon sequencing, and Staphylococcus aureus abundance was additionally quantified by quantitative PCR (qPCR). Changes in bacterial diversity and relative taxonomic abundance were evaluated and correlated with clinical disease severity and treatment modality. Results All treatment groups demonstrated clinical improvement within the first 3 months. Dupilumab induced an early and sustained reduction in Staphylococcus aureus, with near-complete depletion observed by month 3, accompanied by a significant decrease in the ratio of the genus Staphylococcus to the genera Corynebacterium and Cutibacterium. Treatment with JAK inhibitors was associated with clinical improvement and a later, less pronounced reduction in S. aureus, with a corresponding decrease in the established dysbiosis ratio observed at month 6. Analysis of the ratio at a higher taxonomic level (Firmicutes to Actinobacteria) yielded comparable results. In contrast, patients treated with cyclosporine A or topical corticosteroids showed clinical improvement without relevant or sustained changes in skin bacteriome composition. Overall bacterial alpha diversity remained unchanged across treatment groups. Conclusions These results indicate that anti-inflammatory therapies differ in their effects on the skin bacteriome in atopic dermatitis. Dupilumab was associated with a consistent reduction in Staphylococcus aureus, likely reflecting selective inhibition of IL-4 and IL-13 signaling and improvement of Th2-associated barrier dysfunction. JAK inhibitors also led to clinical improvement and a measurable reduction in S. aureus, although microbiome changes were less pronounced, possibly due to broader, less specific inhibition of multiple cytokines. In contrast, cyclosporine A and intermittent topical corticosteroids improved disease severity without substantial or sustained changes in bacterial composition. Overall, these findings suggest that targeting type 2 inflammation with biologic or small-molecule therapies can shift the skin bacteriome toward a healthier balance, whereas traditional anti-inflammatory treatments show limited effects. These observations are exploratory and underscore the need for larger, longitudinal studies to clarify which cytokines, pathways, and mechanisms are most important for modulating the skin microbiome in atopic dermatitis. |