Allergen-specific immunotherapy (AIT) has shown beneficial effects against atopic dermatitis (AD); however, the mechanisms and parameters underlying the efficacy of AIT remain unclear. Here, we report that the community structure and function of the oral and gut microbiota are changed in patients with AD undergoing AIT. Transplantation of fecal microbiota from patients who respond well to AIT improves AD-like dermatitis in mice. The abundance of Brevundimonas vesicularis in the gut of AD patients has been found to be positively correlated with disease severity and is decreased following AIT. Furthermore, we find that B. vesicularis from the oral cavity might ectopically colonize the gut of AD patients. In AD model mice, meanwhile, B. vesicularis promotes the skewing of the Treg/Th17 balance toward Th17 polarization and attenuates the efficacy of ovalbumin-specific immunotherapy. Our findings provide potential strategies for the optimization of AIT for AD via the modulation of the gut microbiota.

Malassezia globosa is a major member of the human skin mycobiota and is associated with several cutaneous disorders, yet it remains unclear whether its in vitro azole susceptibility varies with disease status or anatomical site. We evaluated 55 M. globosa isolates obtained from five healthy controls, five patients with atopic dermatitis (AD), and five patients with pityriasis versicolor (PV). Isolates were collected from the forehead, posterior neck, and antecubital fossa in all participants, with additional lesional isolates from AD and PV. Minimum inhibitory concentrations (MICs) were determined for fluconazole, ketoconazole, itraconazole, posaconazole, voriconazole, and isavuconazole. Fluconazole showed the broadest MIC range (0.5–64 μg/mL), whereas posaconazole and voriconazole showed lower ranges (0.00375–0.5 μg/mL). Mixed-effects analyses of the three shared non-lesional sites detected no significant disease-group, site, or disease-by-site effects for any drug (all p > 0.05). Repeated-measures analyses within AD and PV likewise found no significant overall site effect when lesional skin was included. These exploratory data indicate substantial inter-isolate heterogeneity but no consistent association between M. globosa azole susceptibility and clinical group, anatomical site, or lesional status. Larger standardized and strain-resolved studies are warranted.