Epicutaneous and nasal Staphylococcus aureus colonization augments cutaneous inflammation in patients with psoriasis vulgaris

Background Skin microbiota may augment psoriatic skin inflammation via induction of interleukin-36 alpha (IL-36 alpha). Objective To evaluate the prevalence of Staphylococcus aureus colonization in patients with psoriasis vulgaris and its relation to serum expression levels of inflammatory markers IL-36 alpha and IL-17A. Patients and methods This study included 24 patients with psoriasis vulgaris and 24 healthy controls. History taking, clinical examination, and psoriasis clinical severity assessment were performed. Expressions of IL-36 alpha and IL-17A were determined by real-time quantitative PCR for all patients. Epicutaneous S. aureus colonization was assessed in patients and controls by routine microbiological techniques. Results Psoriatic lesional skin was positive for S. aureus colonization in six (25%) patients versus none of the controls (P=0.022). The nasal mucosa was positive for Staphylococcus colonization in seven (29.2%) psoriatic patients versus only one (4.2%) control (P=0.048). Lesional skin was not different from nonlesional skin regarding S. aureus colonization (P=0.267). Mean IL-36 alpha and IL-17A expression levels were significantly higher in S. aureus-colonized patients versus noncolonized patients (P<0.001). Results of the linear regression analysis revealed that IL-36a was independently affected by lesional skin S. aureus colonization (P=0.009) and that IL-17A expression (P=0.005) was significantly associated with IL-36a expression after controlling for other factors. Conclusion Psoriatic skin is more susceptible to S. aureus colonization. S. aureus skin and nasal mucosa colonization may have a possible pathogenetic role in psoriasis via activating IL-36 alpha-IL-17A-associated pathway.