Onychomycosis and Trichosporon beigelii in Korea

Background Onychomycosis is a common superficial fungal infection. Causative organisms in onychomycosis have been extensively studied, but the role of nondermatophytes is controversial. Trichosporon beigelii is a soil and water inhabiting yeast and is occasionally found in the flora normally associated with human skin. mouth, and nails. Several reports in the literature have suggested that T. beigelii is one of the pathogens in onychomycosis. Methods We performed a survey of the mycologic laboratory records of patients clinically suspected of having onychomycosis from July 1996 to December 1998. Results Out of a total of 2591 nail samples examined, 1222 (47.2%) were culture positive, including 262 cases (10.1%) with T. beigelii. The overall positive rate for the KOH mount examination was 58.8%, and in the cases with T. beigelii was 89.1%. Among the age groups, the incidence rate was highest in the fifth decade (26.6%). The most common causative organism of microscopy-positive onychomycosis was Trichophyton rubrum (61.4%); the others in decreasing frequency were T. beigelii (20.4%), Candida spp. (7.3%), Trichophyton mentagrophytes (4.1%), and mixed infection (2.9%). T. beigelii was repeatedly isolated in successive nail cultures from 10 of 20 patients selected from those with T. beigelii nail infection. Conclusions T. beigelii was the second most commonly isolated fungus in onychomycosis and had a high positive rate on KOH mount examination of the nails and successive repeated cultures. We suggest that T. beigelii might be a common pathogen of onychomycosis in Korea.