Susceptibility characterization of Scytalidium sp. clinical isolates to antifungi and photosensitizers

Abstract

The filamentous fungus Scytalidium sp. is a saprophytic and phytopathogenic microorganisms found in soil and vegetation of tropical and subtropical climate. Scytalidium sp. is among of the main non-dermatophytic filamentous agents causing the disease, together with the genera Scopulariopsis, Fusarium, Aspergillus and Onychocola. Species of Scytalidium sp. has been associated with nail primary pathogenesis, which the prevalence of infections has increased in recent decades, although few cases have been reported. There are reports of superficial and deep infections caused by the genus Scytalidium in immunocompetent and immunocompromised patients, including the central nervous system abscess, endophthalmitis, sinusitis, osteomyelitis, fungemia, subcutaneous infections, mycetoma, lymphangitis, lymphadenitis, tinea pedis, onychomycosis, among others. The Scytalidium dimidiatum has been associated with deep infections comparing with its hyaline variant, S. hyalinum. The hyaline variant preferably is involved in infections of skin and nail suggesting that the strain deficient in melanin may be less virulent than the pigmented. Few data are described in the literature about the sensitivity to antifungal drugs and there are no reports evaluating the use of photodynamic therapy for Scytalidium dimidiatum and Scytalidium hyalinum. Due to increased Scytalidium sp. resistance to some antifungal drugs compared to dermatophytes, the differential diagnosis is essential for successful treatment. Thus, the aim of this study is (i) the determination of possible polymorphisms among the clinical isolates of S. hyalinum and S. dimidiatum, (ii) the characterization of antifungal and photosensitizers susceptibility profile of S. dimidiatum and S. hyalinum strains isolated from clinical samples, as well as (iii) the investigation of factors that could justify the difference in antifungal drugs resistance and pathogenicity (tolerance to different pH, temperatures and differential expression of proteins). (AU)