Elevated Kocuria rhizophila contributing to repair of skin barrier function in patients with atopic dermatitis.

Background: Recent findings suggest skin microbiota is closely linked to the aggravation of atopic dermatitis (AD) and skin barrier dysfunction.

Methods: This prospective cross-sectional study included 52 children: 35 with AD flare (F) and non-flare (NF), and 17 without AD (non-AD). Microbes in the skin samples from the three groups were analyzed using 16S rRNA amplicon sequencing. We estimated the anti-virulence of Kocuria rhizophila in the skin microbiome of children. The effects of K. rhizophila were evaluated in human skin cell models with AD-like damage caused by Staphylococcus aureus secretory toxins, including protein A (PA), lipoteichoic acid, and protease V8.

Results: Taxonomic classification revealed significant phylum-level differences among the three groups. Alpha-diversity indices tended to decrease in the AD-F group compared with the non-AD group but were higher in the AD-NF group. The AD group had a high relative abundance of S. aureus, but S. aureus was almost absent in the non-AD group and exhibited a marked decrease in the AD-NF group; K. rhizophila was negatively correlated with AD severity. Heat-killed K. rhizophila (HKKR) treatment upregulated gene expression of the tight junction protein zonula occludens-1 and critical components of the cornified cell envelope, involucrin and filaggrin, while downregulating the expression of the pro-inflammatory cytokines interleukin (IL)-1b and IL-6. Transcriptomic analysis revealed that HKKR treatment was associated with skin barrier functions, cell-cell junctions, and immune responses.

Conclusions: K. rhizophila may be associated with the mitigation of skin barrier dysfunction and inflammation in S. aureus infection, highlighting its potential for AD treatment.