Staphylococcus Agr virulence is critical for epidermal colonization and associates with atopic dermatitis development.

Atopic dermatitis (AD) is commonly associated with colonization by Staphylococcus aureus in the affected skin. To understand the role of S. aureus in the development of AD, we performed whole-genome sequencing of S. aureus strains isolated from the cheek skin of 268 Japanese infants 1 and 6 months after birth. About 45% of infants were colonized with S. aureus at 1 month regardless of AD outcome. In contrast, skin colonization by S. aureus at 6 months of age increased the risk of developing AD. Acquisition of dysfunctional mutations in the S. aureus Agr quorum-sensing (QS) system was primarily observed in strains from 6-month-old infants who did not develop AD. Expression of a functional Agr system in S. aureus was required for epidermal colonization and the induction of AD-like inflammation in mice. Thus, retention of functional S. aureus agr virulence during infancy is associated with pathogen skin colonization and the development of AD.