Abstract
Overgrowth of Staphylococcus aureus (S. aureus) on the skin is associated with the exacerbation of inflammatory skin diseases such as atopic and seborrheic dermatitis. Previously, we used turbidity (OD600) measurments to show that a cationic peptide (Peptiskin, a peptide mixture composed of arginine and lysine) inhibits S. aureus growth and promotes Staphylococcus epidermidis (S. epidermidis) growth in monoculture. To clarify the selective effect of Peptiskin under co-culture conditions where there is bacterial competition between S. aureus and S. epidermidis, we evaluated the selective effect by plating the cultured bacteria on a mannitol-salt agar medium (red medium) and counting colony numbers. S. aureus and S. epidermidis were co-cultured at initial OD600 ratios of 1:1 or 1:17. In both co-cultures, S. aureus outgrew S. epidermidis in the Peptiskin-free groups. In contrast, Peptiskin significantly inhibited S. aureus growth and only S. epidermidis growth was observed. Furthermore, we evaluated a mixture of Peptiskin and maltotetraose-containing oligosaccharide (MTO), which has been previously identified to effectively inhibit S. aureus and promote S. epidermidis growth in monoculture turbidity assays. The mixture significantly inhibited the growth of S. aureus but not that of S. epidermidis. In addition, the mixture significantly promoted the growth of S. epidermidis compared to using Peptiskin alone. The selective effects of using Peptiskin alone or in combination with MTO demonstrate the potential of Peptiskin to regulate the balance of resident skin bacteria. These results suggest the potential of Peptiskin for improving inflammatory skin diseases and its excellent applicability in skincare products such as shampoos, facial cleansers, and moisturizers.
