Skin pH–dependent Staphylococcus aureus abundance as predictor for increasing atopic dermatitis severity. Issue 11 (6th July 2020) - Hülpüsch, Claudia
Abstract: Background: Atopic eczema (atopic dermatitis, AD) is characterized by disrupted skin barrier associated with elevated skin pH and skin microbiome dysbiosis, due to high Staphylococcus aureus loads, especially during flares. Since S aureus shows optimal growth at neutral pH, we investigated the longitudinal interplay between these factors and AD severity in a pilot study. Method: Emollient (with either basic pH 8.5 or pH 5.5) was applied double‐blinded twice daily to 6 AD patients and 6 healthy (HE) controls for 8 weeks. Weekly, skin swabs for microbiome analysis (deep sequencing) were taken, AD severity was assessed, and skin physiology (pH, hydration, transepidermal water loss) was measured. Results: Physiological, microbiome, and clinical results were not robustly related to the pH of applied emollient. In contrast to longitudinally stable microbiome in HE, S aureus frequency significantly increased in AD over 8 weeks. High S aureus abundance was associated with skin pH 5.7‐6.2. High baseline S aureus frequency predicted both increase in S aureus and in AD severity (EASI and local SCORAD) after 8 weeks. Conclusion: Skin pH is tightly regulated by intrinsic factors and limits the abundance of S aureus . High baseline S aureus abundance in turn predicts an increase in AD severity over the study period. This underlines the importance and potential of sustained intervention regarding the skin pH and urges for larger studies linking skin pH and skin S aureus abundance to understand driving factors of disease progression. Abstract : In healthy individuals, skin microbiome is stable over 8 weeks, but not in atopic dermatitis patients who show a significant increase in Staphylococcus aureus over time. Skin pH of 5.7‐6.2 allows the growth of S aureus in atopic dermatitis individuals. Higher S aureus abundance at baseline is a predictor for increased S aureus and AD severity at endpoint. Abbreviations: AD, atopic dermatitis; HE, healthy.