Skin microbiota of first cousins affected by psoriasis and atopic dermatitis

Background: Psoriasis and atopic dermatitis (AD) are chronic inflammatory skin diseases, which negatively influence the quality of life. In the last years, several evidences highlighted the pivotal role of skin bacteria in worsening the symptomatology of AD and psoriasis. In the present study we evaluated the skin microbiota composition in accurately selected subjects affected by (AD) and psoriasis. Methods: Three first cousins were chosen for the study according to strict selection of criteria. One subject was affected by moderate AD, one had psoriasis and the last one was included as healthy control. Two lesional skin samples and two non-lesional skin samples (for AD and psoriatic subjects) from an area of 2cm2 behind the left ear were withdrawn by mean of a curette. For the healthy control, two skin samples from an area of 2cm2 behind the left ear were withdrawn by mean of a curette. DNA was extracted and sequencing was completed on the Ion Torrent PGM platform. Culturing of Staphylococcus aureus from skin samples was also performed. Results: The psoriatic subject showed a decrease in Firmicutes abundance and an increase in Proteobacteria abundance. Moreover, an increase in Streptococcaceae, Rhodobacteraceae, Campylobacteraceae and Moraxellaceae has been observed in psoriatic subject, if compared with AD individual and control. Finally, AD individual showed a larger abundance of S. aureus than psoriatic and healthy subjects. Moreover, the microbiota composition of non-lesional skin samples belonging to AD and psoriatic individuals was very similar to the bacterial composition of skin sample belonging to the healthy control. Conclusion: Significant differences between the skin microbiota of psoriatic individual and healthy and AD subjects were observed.