Biofilm Propensity of Staphylococcus Aureus Skin Isolates Is Associated With Increased Atopic Dermatitis Severity and Barrier Dysfunction in the MPAACH Pediatric Cohort

Background Atopic dermatitis (AD) patients are often colonized withStaphylococcus aureus,and staphylococcal biofilms have been reported on adult AD skin lesions. The commensalS epidermidiscan antagonizeS aureus, although its role in AD is unclear. We sought to characterizeS aureusandS epidermidiscolonization and biofilm propensity and determine their associations with AD severity, barrier function, and epidermal gene expression in the first US early-life cohort of children with AD, the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children (MPAACH). Methods The biofilm propensity of staphylococcal isolates was assessed by crystal violet assays. Gene expression of filaggrin and antimicrobial alarminsS100A8andS100A9was measured in keratinocyte RNA extracted from skin tape strips. Staphylococcal biofilms sampled from MPAACH skin were visualized using scanning electron microscopy. Results Sixty-two percent of staphylococcal isolates (sampled from 400 subjects) formed moderate/strong biofilms. Sixty-eight percent of subjects co-colonized with both staphylococcal species exhibited strains that formed cooperative mixed-species biofilms. Scanning electron microscopy verified the presence of staphylococcal biofilms on the skin of MPAACH children.Staphylococcus aureusstrains showing higher relative biofilm propensity compared withS epidermidiswere associated with increased AD severity (P = .03) and increased lesional and nonlesional transepidermal water loss (P = .01,P = .03). Conclusions Our data suggest a pathogenic role forS aureusbiofilms in AD. We found that strain-level variation in staphylococcal isolates governs the interactions betweenS epidermidisandS aureusand that the balance between these two species, and their biofilm propensity, has important implications for AD.