The Species-Selective Activity of Peptiskin Is Associated with Cell Wall Affinity and Extracellular DNA Binding in Staphylococcus aureus and Staphylococcus epidermidis

Skin health depends on the balance of the commensal microbiota. Excessive proliferation of Staphylococcus aureus contributes to inflammatory skin diseases, such as atopic dermatitis, whereas Staphylococcus epidermidis helps maintain skin homeostasis. We previously reported that Peptiskin, a mixture of short-chain cationic oligopeptides containing arginine and lysine, selectively suppresses S. aureus while promoting S. epidermidis growth, although the underlying mechanism remains unclear. We investigated this mechanism by evaluating Peptiskin’s effects on pH, nutrient utilization, extracellular DNA (eDNA), membrane damage, cell wall binding, antibacterial activity, bacteriostatic activity, and intracellular gene expression. The species-specific effects were not fully explained by changes in pH or nutrient availability. In S. aureus, Peptiskin induced substantial membrane damage, as indicated by ~66% lactate dehydrogenase release, stronger cell wall binding, higher antibacterial activity, and reduced ATP synthase-related gene expression, consistent with bactericidal and bacteriostatic effects. Conversely, membrane damage was minimal in S. epidermidis, whereas Peptiskin showed distinct interactions with eDNA, and extracellular interactions may contribute to the distinct growth response. The species-specific activity of Peptiskin was associated with differences in cell wall affinity, eDNA interactions, membrane susceptibility, and intrinsic physiological responses, providing a potential strategy for selectively modulating the skin microbiota while suppressing S. aureus-dominant conditions.