Identification, antifungal susceptibility and scanning electron microscopy of a keratinolytic strain of Rhodotorula mucilaginosa: a primary causative agent of onychomycosis

• Published in: FEMS immunology and medical microbiology Vol. 55; no. 3; pp. 396 - 403
• Main Authors: da Cunha, Marcel M.L, dos Santos, Luana P.B, Dornelas-Ribeiro, Marcos, Vermelho, Alane B, Rozental, Sonia
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.04.2009; Blackwell Publishing Ltd; Blackwell; Oxford University Press
• Subjects: Amphotericin B; Antifungal Agents - pharmacology; Biological and medical sciences; Brazil; Carbohydrate metabolism; Carbohydrates; Drug Resistance, Fungal; Electron microscopes; electron microscopy; Fluconazole; Flucytosine; Fundamental and applied biological sciences. Psychology; Fungi; Fungicides; Grooves; Human mycoses; Humans; Infectious diseases; Itraconazole; Keratin; Keratinase; Keratinocytes; Keratins - metabolism; Light microscopy; Low concentrations; Male; Medical sciences; Microbial Sensitivity Tests; Microbiology; Microscopy, Electron, Scanning; Middle Aged; Miscellaneous; Morphology; Mycological Typing Techniques; Mycology; Mycoses; Mycoses of the skin; Onychomycosis; Onychomycosis - microbiology; Rhodotorula - drug effects; Rhodotorula - isolation & purification; Rhodotorula - ultrastructure; Rhodotorula mucilaginosa; Rhodotorula rubra; Saccharomyces cerevisiae; Scanning electron microscopy; Terbinafine; Toenail; Urease; Voriconazole; Yeast; Yeasts; Brazil; onychomycosis; electron microscopy; keratinase; Skin disease; Yeast; Mycosis; Microbiology; Identification; Electron microscopy; Onychomycosis; Strain; Fungi; Infection; Antifungal agent; Sensitivity; Immunology; Rhodotorula mucilaginosa; Nail disease; Fungi Imperfecti; Rhodotorula rubra
• ISSN: 0928-8244; 1574-695X; 2049-632X
• DOI: 10.1111/j.1574-695X.2009.00534.x

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.