Genetic and phenotypic profiling of Staphylococcus aureus colonizing the skin microbiota of adult patients with severe atopic dermatitis.

Staphylococcus aureus is a primary skin colonizer during atopic dermatitis (AD) flare-ups. While host genetic factors primarily drive AD onset, S. aureus exacerbates the disease's severity. This study compared the skin microbiome of lesional (LE) and non-lesional (NL) sites from the forearm of 16 individuals with severe AD against healthy subjects (HS). Moreover, the genotypic and phenotypic traits of S. aureus isolates were also characterized. Results showed significant differences between AD patients and HS in transepidermal water loss (TEWL), stratum corneum hydration, and microbiome composition. Cutibacterium granulosum was more abundant in HS, while S. aureus and S. lugdunensis were significantly enriched in AD patients' LE skin. From the forearms of AD patients, 15 S. aureus strains were isolated, each displaying a significant genetic diversity within the species. Despite their varied genetic background, these strains shared phenotypic traits crucial for persistence, such as adhesion, biofilm formation, desiccation resistance, and hemolytic activity, with notable covariance in biofilm matrix components. The study suggests that AD-related skin barrier impairment is associated with a distinctive microbial imbalance characterized by an enrichment of genetically diverse S. aureus strains that share biofilm-forming phenotypic traits. These insights may guide the development of strategies to counteract S. aureus colonization, potentially reducing AD severity.