Reduction in the colonization of Staphylococcus aureus on the skin surface under calcium-/magnesium-depleted...

Excessive expansion of Staphylococcus aureus is associated with several skin diseases, including atopic dermatitis (AD). Recently, we have demonstrated that washing skins with ultra-pure soft water containing little bivalent metal ions improved skin conditions of atopic subjects. In this study, we investigated the roles of calcium or magnesium on the proliferation of S. aureus both in vitro and in vivo. Depletion of calcium and magnesium in the culture medium significantly suppressed the expansion of S. aureus growth. When S. aureus, diluted with water containing calcium/magnesium at the concentration of medium-hard water (83·0 mg l^-1 as CaCO₃ ) or the one that contains little calcium/magnesium, was applied onto the tape-stripped skin of Hos:HR-1 mice, growth of S. aureus in water without those minerals on the skin was suppressed. These results suggest that depletion of both calcium and magnesium abrogate the proliferation of S. aureus not only in the culture system but also on the skin surface of mice. Since colonization of S. aureus on the skin is well-known to exacerbate AD symptoms, usage of ultra-pure soft water containing less calcium and magnesium may improve the skin condition through the suppression of S. aureus growth on the skin of patients with skin problems.

This study demonstrates the importance of calcium and magnesium for the colonization and growth of Staphylococcus aureus by using both in vitro culture systems and in vivo experiments on the murine skin. Our results indicate that the removal of these metal ions is probably beneficial for protecting the skin from S. aureus. Thus, using ultra-pure soft water without metal ions may improve the skin condition of patients with skin problems through the protection from S. aureus colonization.