Resumo

The saprophytic and phytopathogenic filamentous fungus and melanin-Like producer Scytalidium dimidiatum, is among of the main non-dermatophytic agents causing superficial and nails primary mycosis, and deep infections in immunocompetent and immunocompromised patients. On the other hand, the melanin-Like deficient producer Scytalidium hyalinum is preferably involved in skin and nail infections suggesting that S.hyalinum is less virulent than the pigmented specie S.dimidiatum. Few data are described in the literature about the sensitivity to antifungal drugs for both, S.dimidiatum and S.hyalinum. Due to increased Scytalidium sp. resistance to some antifungal drugs compared to dermatophytes species, the differential diagnosis is essential for successful treatment. Thus, the aim of this study was the identification of S.hyalinum and S.dimidiatum from clinical samples of onychomycoses by classical (macro and micromorphology) and molecular techniques (ribosomal DNA Internal Transcribed spacer - ITS sequencing). BLAST method based on similarity was used to evaluate the identification capacity of the ITS2 region. Additionally, the antifungal susceptibility characterization of the identified strains was carried out by using the Clinical and Laboratory Standards Institute (CLSI) M38-A2 broth microdilution method. The ribosomal DNA ITS2 region sequence analyses of the clinical isolates have identified 35 strains with 100% DNA sequence identity to S.dimidiatum and S.hyalinum. Both species are identical in DNA sequence, differing only in melanin-Like pigment production. The antifungal susceptibility test have shown no significant minimum inhibitory concentrations (MICs) values differences between S.hyalinum and S.dimidiatum, for Amphotericin B, 5- Fluocitocina, Terbinafine and Caspofungin with 0.0625-0.5 µg/mL, 4-16 µg/mL, 0.25-2.0 µg/mL, 2-16 µg/mL as MICs values, respectively. Nonetheless, the MICs values for Ketoconazole, Fluconazole and Voriconazole were higher for S.dimidiatum clinical isolates than S.hyalinum clinical isolates. As described in the literature, the pathways involved in the oxidative stress response are activated by antifungal azole response. This suggests that reduced susceptibility to oxidative damage may contribute to azole antifungal resistance, which explains the increase susceptibility of S.hyalinum once this specie doesn’t produce melanin-Like that has broad antioxidant activity. Financial Support: FAPESP.