941 The Influence of skin commensal microbiota on the ultraviolet radiation-induced erythema response in human skin in vivo

The skin commensal microbiota is regularly exposed to ultraviolet radiation (UVR) in sunlight. Studies mice have demonstrated that the modulates inflammatory environment following UVR exposure. However, role of development UVR-induced inflammation (sunburn) has not been reported humans. We examined UVR-erythema dose-response human upper back (n=8, type I-III) presence and absence microbiota. One side was cleaned with 70% ethanol remove microbiota, then both sides were a geometric series 10 doses solar-simulated (erythemally-weighted, 7-80mJ/cm2). At 24h post-irradiation, minimal erythemal dose (MED; sunburn threshold) assessed visually erythema intensity quantified (CIE a*) assess through area under curve (AUC) analysis. There no significant difference (P=0.91) MED between un-cleaned sites (median 12 9 mJ/cm2 respectively). also (P=0.87) overall response (mean±SD 494±165 500±148 at maximum given (80mJ/cm2) significantly lower (P<0.05) (9.5±2.7) compared (10.8±2.7). Further studies will correlate tissue markers, but these data suggest potential for higher exposure vivo.