Effect of Systemic Therapies on Skin Bacteriome in Patients with Atopic Dermatitis: A Pilot Prospective Study

Atopic dermatitis is a complex disease that requires treatments addressing skin barrier disruption, inflammation, and microbial imbalance. In this study, we aimed to investigate the effects of 4 different therapies on clinical outcomes and skin bacteriome in patients with atopic dermatitis, namely: Jak inhibitors, dupilumab, cyclosporine A, and topical corticosteroids (intermittently used methylprednisolone aceponate). Samples from 60 patients were collected before treatment and after 3 and 6 months, and their bacteriome diversity and composition were analyzed. All treatment groups showed significant improvement in disease severity after 3 months; however, only dupilumab resulted in a marked reduction in serum IgE levels and an almost complete depletion of Staphylococcus aureus. The relative abundance of this bacterium correlated with disease severity and remained significantly lower in patients receiving dupilumab than in those treated with cyclosporine A or topical corticosteroids. Although overall bacteriome alpha diversity remained unchanged, the ratio of Staphylococcus to Corynebacterium and Cutibacterium decreased significantly after Jak inhibitors as well as dupilumab treatment but remained stable with cyclosporine A and topical corticosteroids. These results indicate that addressing type 2 inflammation by targeted drugs alters the skin bacteriome toward a healthy balance, whereas traditional anti-inflammatory treatments have minimal impact on microbial composition.