Ketoconazole 2% cream alters the skin fungal microbiome in seborrhoeic dermatitis: a cohort study.

Background: Seborrhoeic dermatitis (SD) is a common chronic inflammatory dermatosis. Current theories on the pathogenesis of SD highlight the role of microbes on the skin surface. Ketoconazole is commonly used for the treatment of SD; however, there are limited data focusing on the effects of ketoconazole in shaping the skin microbiome in patients with SD.

Aim: In this prospective cohort study, we used a high-throughput DNA sequencing method to characterize the cutaneous microbial communities of patients with SD before and after topical ketoconazole treatment.

Methods: In total, 30 patients with facial SD and 15 age- and sex-matched healthy controls (HCs) were enrolled in this study. Skin swabs were collected from SD lesional sites of the cheek at baseline, after ketoconazole treatment and 2 weeks post-treatment. DNA was extracted from skin samples. The bacterial 16S V3V4 rRNA and fungal internal transcribed spacer 1-5F regions were sequenced, and the microbial community compositions were analysed.

Results: Significantly lower bacterial and fungal diversities were detected at the lesional sites of facial SD compared with HCs. A decreased relative abundance of Cutibacterium and increased abundances of Malassezia and Staphylococcus were found in facial SD. Disease diversity was positively correlated with the relative abundances of Malassezia, Staphylococcus and Corynebacterium, while transepidermal water loss was negatively associated with the relative abundance of Cutibacterium. After ketoconazole treatment, fungal Shannon diversity and the relative abundances of Candida and Aspergillus were significantly increased at the lesional sites, and the relative abundance of Malassezia showed a decreasing trend. These changing trends were maintained until 2 weeks post-treatment.

Conclusion: Facial SD showed lower fungal diversity accompanied by increased relative abundances of Malassezia and Staphylococcus and decreased relative abundance of Cutibacterium. Ketoconazole treatment reduced Malassezia and increased fungal diversity to restore skin microbial communities.