Sebum and Hydration Levels in Specific Regions of Human Face Significantly Predict the Nature and Diversity of Facial Skin Microbiome
These authors tested the hypothesis that inter-individual variation in facial skin microbiome can be significantly explained by variation in sebum and hydration levels in specific facial regions of humans.
They measured sebum and hydration from forehead and cheek regions of healthy female volunteers (n = 30). Metagenomic DNA from skin swabs were sequenced for V3-V5 regions of 16S rRNA gene.
Specifically, a cohort of 30 healthy female individuals was recruited (mean age: 29.5 ± 5.48 years) with written, informed consent for participation in the study from in and around Whitefield area of Bangalore city, India. No study participant had taken any antibiotic for the past 6 months. Each study participant was advised not to wash her face with soap or take a bath at least 12 hours before arrival in the sample collection site. On arrival, their faces were washed with sterile water (MilliQ) and they were put in a controlled environment at 24 °C and relative humidity of 45% for a minimum period of 4 hours before sample collection. This was done to provide sufficient time for the resident skin microflora and the levels of skin health parameters like sebum and hydration, to regain their individuality. Using Sebumeter (measures sebum content, Courage + Khazaka electronic GmbH) and Corneometer (measures hydration, Courage + Khazaka electronic GmbH), two readings on levels of sebum and hydration from forehead and two readings from the cheek regions were taken on each study participant for measuring sebum and hydration levels.
After a period of 14 days, the study participants were again recalled and the same protocol was implemented on each. During the 14-day period between the two phases of sample collection, each study participant was advised to use a specific marketed soap which does not have any antibacterial active in it. They were also advised not to use any skin care product on the facial regions for the 14-day period of time. Skin swabs were collected from facial regions, excluding lips and nose, using moistened sterile pads (2 × 2 cm) for 10 seconds each.
Altogether, 34 phyla were identified; predominantly Actinobacteria (66.3%), Firmicutes (17.7%), Proteobacteria (13.1%) and Bacteroidetes (1.4%).
About 1000 genera were identified; predominantly Propionibacterium (58.6%), Staphylococcus (8.6%), Streptococcus (4.0%), Corynebacterium (3.6%) and Paracoccus (3.3%).
A subset (n = 24) of individuals were sampled two months later. The skin microbiome was found to be stable over this interval.
Stepwise multiple regression analysis showed that cheek sebum level was the most significant predictor of microbiome composition and diversity followed by forehead hydration level; forehead sebum and cheek hydration levels were not.
With increase in cheek sebum, the prevalence of Actinobacteria (p = 0.001)/Propionibacterium (p = 0.002) increased, whereas microbiome diversity decreased (Shannon Index, p = 0.032); this was opposite for other phyla/genera.
These trends were reversed for forehead hydration levels. Therefore, the nature and diversity of facial skin microbiome is jointly determined by site-specific lipid and water levels in the stratum corneum.
Comment: While this study was performed on the faces of women from India, it may have relevance to the problem we face with Propionibacterium in the skin of those having shoulder surgery, especially male patients.
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