Characterisation of the nail microbiome in psoriatic and nonpsoriatic patients with onychomycosis.

Background: Onychomycosis (OM) is the most common infectious nail disease, and it occurs frequently in patients with psoriasis. Microbial community shifts have been suggested to play a role in psoriasis and fungal infection occurrence.

Objectives: To investigate and compare nail microbial community compositions in psoriatic and nonpsoriatic patients with OM.

Methods: Toenail samples were collected from nonpsoriatic patients with OM, psoriatic patients with nail psoriasis (NP) and OM, patients with only NP and healthy controls. Bacterial and fungal community compositions were analysed by amplicon sequencing of the V3-V4 regions of the 16S rDNA gene and the ITS1 region, respectively.

Results: Psoriatic OM patients had higher bacterial and fungal alpha diversities. Taxonomic analysis revealed a significantly lower relative abundance of Trichophyton rubrum (32.88% vs 82.18%, p < .001) and an increased trend of the abundance of Candida in psoriatic patients with OM than in nonpsoriatic patients. Nonpsoriatic patients with OM had a higher abundance of Staphylococcus than healthy controls (59.66% vs 45.76%, p < .05). Trichophyton, Alternaria and Malassezia could accurately differentiate psoriatic and nonpsoriatic patients with OM, with an area under the curve (AUC) of 0.86. The severity of OM was positively correlated with the relative abundance of Trichophyton rubrum. Further, Trichophyton was positively correlated with Staphylococcus and negatively correlated with Corynebacterium, Anaerococcus, Malassezia and Alternaria.

Conclusions: The nail microbiome in psoriatic patients with OM has distinct bacterial and fungal signatures, suggesting that different dysbiosis is associated with the pathogenesis of OM in psoriatic and nonpsoriatic patients.