Atopic dermatitis (AD) is a chronic inflammatory skin condition known for its complex etiology and frequent flare-ups. Traditionally, research into AD has focused on the epidermal microbiota, especially the dominance of Staphylococcus aureus and loss of beneficial skin commensals. However, this superficial view overlooks the dermal compartment, which harbors a more stable and host-interactive microbial community. This study by Bay et al. shifts the focus inward—investigating whether the dermal microbiota can more accurately differentiate between AD and healthy skin and thus provide a more refined lens for understanding disease pathogenesis and developing targeted treatments.
Methods
The study recruited 37 AD patients and 37 healthy controls, collecting skin biopsies and tape strips from dry, moist, and sebaceous areas. Skin samples were separated into epidermal and dermal compartments. A multi-modal analysis approach was employed—combining cultivation, MALDI-TOF mass spectrometry, confocal microscopy, and 16S rRNA sequencing—to evaluate both microbial composition and functional profiles in these skin layers.
Key Findings
- Layer-Specific Differences: The dermis exhibited a more conserved and distinct microbial profile compared to the more variable epidermis.
- Taxonomic Shifts: AD skin showed an increase in Staphylococcus and Streptococcus, with a concurrent decrease in Cutibacterium, particularly in dermal layers.
- Unique Dermal Signatures: Genera like Prevotella and Mitsuokella varied significantly only in the dermis between AD and healthy skin.
- Functional Differences: In AD skin, gene pathways related to menaquinone biosynthesis, lactose/galactose degradation, and NAD biosynthesis were significantly altered—especially in the dermis.
- Stable Community Despite Flare-ups: Microbial composition remained largely consistent between lesional and non-lesional skin in AD patients, suggesting a chronic microbial shift rather than transient changes.
- Improved Diagnostic Potential: Dermal sampling revealed clearer differentiation between AD and healthy skin than epidermal analyses, highlighting its potential as a biomarker source.
This study presents a compelling case for moving beyond the surface in skin microbiome research. By focusing on the dermal layer, the authors reveal a stable, host-interactive bacterial community that better reflects AD status than the superficial microbiota. The novelty of this research lies in its dual-compartment analysis and the discovery of dermal-specific taxonomic and functional markers for AD. Looking ahead, incorporating dermal microbiome profiling could redefine how we diagnose, monitor, and personalize treatment for atopic dermatitis, offering a more precise and enduring path to therapeutic development.
Link to the study: https://journals.asm.org/doi/epub/10.1128/msphere.00156-25
