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BackgroundThe treatment of psoriasis has been revolutionized by the development of biologic therapies. However, the pathogenesis of psoriasis, in particular the role of the cutaneous microbiome, remains incompletely understood. Moreover, skin microbiome studies have relied heavily on 16S rRNA sequencing data in the absence of bacterial culture.ObjectivesTo characterize and compare the cutaneous microbiome in 20 healthy controls and 23 patients with psoriasis using metagenomic analyses and to determine changes in the microbiome during treatment.MethodsSwabs from lesional and nonlesional skin from patients with psoriasis, and from controls matched for site and skin microenvironment, were analysed using both 16S rRNA sequencing and traditional culture combined with mass spectrometry (MALDI‐TOF) in a prospective study.ResultsPsoriasis was associated with an increased abundance of Firmicutes and a corresponding reduction in Actinobacteria, most marked in lesional skin, and at least partially reversed during systemic treatment. Shifts in bacterial community composition in lesional sites were reflected in similar changes in culturable bacteria, although changes in the microbiota over repeated swabbing were detectable only with sequencing. The composition of the microbial communities varied by skin site and microenvironment. Prevotella and Staphylococcus were significantly associated with lesional skin, and Anaerococcus and Propionibacterium with nonlesional skin. There were no significant differences in the amount of bacteria cultured from the skin of healthy controls and patients with psoriasis.ConclusionsShifts in the cutaneous microbiome in psoriasis, particularly during treatment, may shed new light on the pathogenesis of the disease and may be clinically exploited to predict treatment response. |