title: Identification, antifungal susceptibility and scanning electron microscopy of a keratinolytic strain of Rhodotorula mucilaginosa: a primary causative agent of onychomycosis.
abstract: Onychomycosis is a dermatological problem of high prevalence that mainly affects the hallux toenail. Onychomycosis caused by the yeast Rhodotorula mucilaginosa was identified using colony morphology, light microscopy, urease and carbohydrate metabolism in a 57-year-old immunocompetent patient from Rio de Janeiro, Brazil. High-resolution scanning electron microscopy of nail fragments, processed by a noncoating method, led to the observation with fine detail of the structures of both nail and fungus involved in the infection. Yeasts were mainly found inside grooves in the nail. Budding yeasts presented a spiral pattern of growth and blastoconidia were found in the nail groove region. Keratinase assays and keratin enzymography revealed that this isolate was highly capable of degrading keratin. Antifungal susceptibility tests showed that the fungus was susceptible to low concentrations of amphotericin B and 5-flucytosine and resistant to high concentrations of fluconazole, itraconazole, voriconazole and terbinafine. These findings showed data for the first time concerning the interaction of R. mucilaginosa in toenail infection and suggest that this emerging yeast should also be considered an opportunistic primary causative agent of onychomycosis.
authors.affiliation: Laboratório de Biologia Celular de Fungos, Instituto de Biofísica Carlos Chagas Filho-UFRJ, Cidade Universitária, Rio de Janeiro, Brazil.
authors.forename: Marcel M L
authors.initials: MM
authors.lastname: da Cunha
authors.forename: Luana P B
authors.initials: LP
authors.lastname: dos Santos
authors.forename: Marcos
authors.initials: M
authors.lastname: Dornelas-Ribeiro
authors.forename: Alane B
authors.initials: AB
authors.lastname: Vermelho
authors.forename: Sonia
authors.initials: S
authors.lastname: Rozental
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D001938:Brazil; D025141:Drug Resistance, Fungal; D006801:Humans; D007633:Keratins / Q000378:metabolism; D008297:Male; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D016533:Mycological Typing Techniques; D014009:Onychomycosis / Q000382:microbiology*; D012248:Rhodotorula / Q000187:drug effects* / Q000302:isolation & purification / Q000648:ultrastructure*
chemical_list: D000935:Antifungal Agents; D007633:Keratins