Epidemiology and fungal species distribution of onychomycosis and other superficial mycoses in the coastal city of Ningbo, China.

Abstract

Background: Superficial fungal infections (SFIs) are among the most common skin diseases worldwide; however, the pathogenic species of SFIs vary among geographical areas. The purpose of this study was to evaluate the epidemiologic profile of superficial fungal infections with a focus on onychomycosis in the Department of Laboratory Medicine of Ningbo First Hospital.

Methods: A total of 1309 patients with superficial mycoses who visited our hospital between March 2023 and October 2024 were selected. Scraping of the lesion was performed via a sterilization scraper. A portion of each sample was used for direct examination, and the other portion was used for cultivation. For the culture results, microscopic morphology and automatic rapid microbial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used as a routine examination. For fungi that routine examinations couldn't identify, further sequencing of the rDNA-ITS region was carried out for atypical strains to the species level.

Results: Patients were between 1 year and 93 years old, and the peak incidence was in the 21-30 years age group. More superficial mycoses were found in women (63.94%) than in men (36.06%). The causative agents identified were: dermatophytes (32.85%), yeasts (49.20%) and non-dermatophyte molds (NDM) (17.95%). Positive cultures of dermatophytes were obtained from 430 patients: Trichophyton spp. (89.07%) was predominant, followed by Microsporum spp. (10.93%). Yeasts were isolated from 644 patients, and Candida spp. (93.01%) were the major pathogens, followed by Trichosporon spp. (6.99%). Among the 1309 patients, nails were the largest source of SFIs (81.67%), followed by glabrous skin (6.04%) and feet (4.20%). Candida spp. were the most prevalent species in cases of onychomycosis (47.05%), followed by Trichophyton spp. (29.09%) and Aspergillus spp. (16.65%).

Conclusion: Our study revealed that nails constituted the largest source of SFIs in Ningbo, and women were more likely to have onychomycosis than men were. Moreover, we found that Candida spp. was the most prevalent species in cases of onychomycosis, and Trichophyton rubrum was responsible for the majority of dermatophyte-associated infections.