Tinea unguium onychomycosis caused by dermatophytes: A ten-year (2005–2014) retrospective study in a tertiary hospital in Singapore

Abstract

INTRODUCTION Tinea unguium is a common nail infection. We conducted a retrospective ten-year study of the patient demographics and species distribution of dermatophytes causing tinea unguium in a tertiary hospital from Singapore. METHODS Results of fungal nail cultures were retrieved from our hospital’s microbiology department. Samples from nail scrapings and clippings were inoculated onto agar plates (Sabouraud dextrose agar with chloramphenicol and Mycosel agar). Nail specimens that grew dermatophytes were included in the study. RESULTS Overall, 229 (male: n = 164, 71.6%; female: n = 65, 28.4%) nail specimens grew dermatophytes. Mean patient age was 58 (range 18–93) years. A majority of specimens came from patients aged over 50 years (n = 162, 70.7%) and 60–79 years (n = 100, 43.7%). Ethnically, 160 (69.9%) patients were Chinese, 36 (15.7%) Indian, 18 (7.9%) Malay and 15 (6.6%) of other ethnicities. Among dermatophytes isolated were Trichophyton rubrum (n = 93, 40.6%), Trichophyton mentagrophytes (n = 60, 26.2%), unidentified Trichophyton spp. (n = 57, 24.9%), Trichophyton tonsurans (n = 10, 4.4%), Epidermophyton floccosum (n = 5, 2.2%), Trichophyton verrucosum (n = 2, 0.9%), Trichophyton soudanense (n = 1, 0.4%) and Trichophyton violaceum (n = 1, 0.4%). CONCLUSION A majority of isolates were from elderly patients. Compared to Singapore’s general population, patients of Indian and other ethnicities were over-represented for tinea unguium when compared to Chinese and Malay patients. Trichophyton rubrum was the most common dermatophyte isolated, while Trichophyton verrucosum, Trichophyton violaceum and Trichophyton soudanense were rare causes of tinea unguium.