A multicenter study was conducted to define the most suitable testing conditions for antifungal susceptibility of dermatophytes. Broth microdilution MICs of clotrimazole, itraconazole, and terbinafine were determined in three centers against 60 strains of dermatophytes. The effects of inoculum density (ca. 10 3 and 10 4 CFU/ml), incubation time (3, 7, and 14 days), endpoint criteria for MIC determination (complete [MIC-0] and prominent [MIC-2] growth inhibition), and incubation temperature (28 and 37°C) on intra-and interlaboratory agreement were analyzed. The optimal testing conditions identified were an inoculum of 10 4 CFU/ml, a temperature of incubation of 28°C, an incubation period of 7 days, and MIC-0.Dermatophytes are a group of morphologically and physiologically related molds that cause well-defined infections in vertebrates. The incidence of dermatophytoses has increased over recent years, particularly in immunocompromised patients (29,30,32,33). The choice of the proper treatment is determined by the site and extent of the infection and the species involved, as well as by the efficacy, safety profile, and kinetics of the available drugs. For localized nonextensive lesions, topical therapies with clotrimazole (CLT) are generally used. For tinea unguium, scalp ringworm, extensive infections, or skin lesions with folliculitis, systemic antifungal treatment is necessary (1,4,23,26). Oral drugs such as itraconazole (ITC) and terbinafine (TRB) are the antifungal agents currently most used to treat severe infections (4, 23). Some novel compounds, such as UR-9825, posaconazole, voriconazole, or ravuconazole, also appear to be promising candidates for the treatment of dermatophytosis (2,10,28).In the in vitro method proposed by the National Committee for Clinical Laboratory Standards (NCCLS) for testing molds (25), the dermatophytes were not included. Therefore, it is necessary to develop a reproducible standardized method for these important fungi that would lead to protocols for proper treatment. In recent years, some authors, possibly encouraged by the development of the above-mentioned reference method, have published various articles wherein several species of dermatophytes have been tested (11,27,28,34). In these works, different adaptations or modifications of the NCCLS methods have been assayed, although other techniques have also been used (3,12,15). The results obtained have been clearly contradictory in some aspects, which makes evident the need for standardization and the development of reference methods. Recently, we evaluated the activity of 11 antifungal drugs against an important number of strains of dermatophytes (n ϭ 508) by using a microdilution method (10). In that study the testing conditions adopted were an inoculum size of 10 4 CFU/ml, a temperature and time of incubation of 28°C and 7 days, respectively, and the MIC endpoint determination was 50% growth inhibition for azoles and 100% for the rest. It is unknown whether varying the conditions would have changed the results significantly....

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C. metapsilosis and C. orthopsilosis are associated with human disease and show a different antifungal susceptibility profile compared with C. parapsilosis sensu stricto.

The strict nutritional requirements of Malassezia species make it difficult to test the antifungal susceptibility. Treatments of the chronic and recurrent infections associated with Malassezia spp. are usually ineffective. The objective of this study was to obtain in vitro susceptibility profile of 76 clinical isolates of Malassezia species against 16 antifungal drugs used for topical or systemic treatment. Isolates were identified by restriction fragment length polymorphism. Minimal inhibitory concentrations (MIC) were obtained by a modified microdilution method based on the Clinical Laboratory Standards Institute reference document M27-A3. The modifications allowed a good growth of all tested species. High in vitro antifungal activity of most tested drugs was observed, especially triazole derivatives, except for fluconazole which presented the highest MICs and widest range of concentrations. Ketoconazole and itraconazole demonstrated a great activity. Higher MICs values were obtained with Malassezia furfur indicating a low susceptibility to most of the antifungal agents tested. Malassezia sympodialis and Malassezia pachydermatis were found to be more-susceptible species than M. furfur, Malassezia globosa, Malassezia slooffiae and Malassezia restricta. Topical substances were also active but provide higher MICs than the compounds for systemic use. The differences observed in the antifungals activity and interspecies variability demonstrated the importance to studying the susceptibility profile of each species to obtain reliable information for defining an effective treatment regimen.