A six-year retrospective study on the causative agents of onychomycosis in China: the emergence of dematiaceous fungi.

Introduction: Onychomycosis, a common nail disease, is caused by a diverse range of pathogens worldwide. However, the epidemiology and pathogen profile of onychomycosis in China remain insufficiently characterized. This study aimed to investigate these aspects in a large Chinese hospital.

Methods: A six-year retrospective analysis was conducted at a tertiary hospital in China, where nail samples from 298 patients who were clinically suspected of onychomycosis were cultured and analyzed to identify causative agents and clinical features.

Results: Of the 298 samples, 51.00% (152) were positive for fungal infection. Young adults (18-30 years) comprised the majority of the patients, with a man-to-woman ratio of 1:1.45. Dermatophytes were the most prevalent causative agents (36.18%), followed by yeasts (28.29%) and non-dermatophyte molds (NDMs) (28.29%). Among dermatophytes, Trichophyton species (34.9%) were the most frequently identified, followed by Candida (21.7%) and dematiaceous fungi (8.6%). Dermatophytes were the predominant pathogens in the patients aged 18-50 years. The toenails (63.04%) were more commonly affected than the fingernails (36.96%), with bilateral toenail involvement (34.07%) being the most frequent.

Conclusion: While dermatophytes remain the leading cause of onychomycosis in China, non-dermatophyte molds, particularly dematiaceous fungi, are emerging as significant pathogens. These organisms present unique treatment challenges and warrant increased clinical attention.