Atopic Dermatitis–like mouse model using early inoculation of patient-derived S. aureus together with MC903

<i>Staphylococcus aureus</i> (<i>S. aureus</i>) worsens atopic dermatitis (AD), but how individual strains differ in pathogenicity remains unclear. Mouse models that mimic AD and allow direct manipulation of <i>S. aureus</i> in early stages of disease are limited. Moreover, these models rarely incorporate clinical <i>S. aureus</i> strains isolated from patients with AD. In this study, we investigated the inflammatory potential of clinical <i>S. aureus</i> and <i>S. epidermidis</i> isolates from patients with AD in a mouse model. Clinical <i>S. aureus</i> strains showed significant variability in their ability to elicit inflammation. The inflammation was associated with differences in virulence factor expression and, to a lesser extent, with genomic variation. In contrast, <i>S. epidermidis</i> strains (taken from the same lesional skin sites of patients) induced only mild but consistent inflammation, with less variability at the strain level. Next, we examined the impact of a pathogenic clinical <i>S. aureus</i> strains in the presence of an MC903-induced type 2 immune environment. Under these conditions, <i>S. aureus</i> enhanced colonization; increased inflammation; and promoted type 1, type 2, and type 17/22 immune responses. These responses were less evident with either treatment alone. Our findings suggest that clinical <i>S. aureus</i> strains from patients with AD differ in their capacity to modulate skin inflammation, particularly within a type 2-skewed environment. These results highlight the potential value of incorporating clinically relevant <i>S. aureus</i> isolates into early-stage in vivo models to better understand AD immunopathology and to inform microbiome-targeted therapeutic strategies.