Dermatophyte and non-dermatophyte onychomycosis in Singapore

Onychomycosis is caused by dermatophytes, moulds and yeasts. It is important to identify the non-dermatophyte moulds as they are resistant to the usual anti-fungals. A prospective study was undertaken in the National Skin Centre, Singapore to study the pattern of dermatophyte and non-dermatophyte onychomycosis. 53 male and 47 female patients seen between June 1990 and June 1991 were entered into the study. Direct microscopy was done and the nail clippings were cultured. Toe and finger nails were equally infected. Dermatophytes were isolated from 21 patients namely, T. rubrum (12/21), T. interdigitale (5/21), T. mentagrophytes (3/21) and T. violaceum (1/21). Candida onychomycosis occurred in 39 patients and was caused by C. albicans (38/39) and C. parapsilosis (1/39). 37/39 patients had associated paronychia. 5 types of moulds were isolated from 12 patients, namely Fusarium species (6/12), Aspergillus species (3/12), S. brevicaulis (1/12), Aureobasilium species (1/12) and Penicillium species (1/12). Although the clinical pattern and microscopy may predict the type of organisms, in practice this is difficult. Only cultures were confirmatory. 28% (28/100) had negative cultures despite a positive microscopy, and moulds (12/100) grown might be contaminants rather than pathogens.