RESUMEN
Accurate diagnosis of onychomycosis is based on clinical findings, direct microscopic investigation and mycological culture. If the diagnosis is not confirmed by culture and improvement does not occur, it is impossible to tell whether this represents treatment failure or an initial incorrect diagnosis. The aim of this study was to identify the major organisms involved in onychomycosis with emphasis on the importance of culture in treating onychomycosis. The study was performed at the Lebanese University, Beirut, Lebanon over a 5-year period (2000-2004). Clinically suspected patients were referred to our mycology laboratory for KOH test and culture. The study included 772 patients (520 women, 252 men). Cultures were positive in 54.3% of cases (predominantly male). The ratio of onychomycosis in toenails/fingernails was 1.9. In toenails, dermatophytes were found in 77.1% of cases, Candida in 18.9% and moulds in 4%. In fingernails, Candida was found in 81% of cases, dermatophytes in 18.1% and moulds in 0.9%. The most commonly isolated dermatophytes were Trichophyton mentagrophytes (36%), T. rubrum (27.5%) and T. tonsurans (26%). Pathogens involved in onychomycosis change according to each geographical area. Therefore, treatments should be based on studies carried out in the same region.