Cutaneotrichosporon

The genus Cutaneotrichosporon was proposed based on the analyses of the DNA sequences coding for seven genes (SSU rRNA, D1/D2 domain of the LSU rRNA, ITS, two subunits of RNA polymerase II, translation elongation factor 1-α, and mitochondrial cytochrome (Liu et al 2015).

Fifteen species were initially assigned to the new genus, however four species reassigned from the genus Trichosporon, namely Cutaneotrichosporon cutaneum, C. dermatis, C. jirovecii and C. mucoides are the most common clinical isolates.

Cutaneotrichosporon species are urease-positive, non-encapsulated basidiomycetous yeasts characterised by the development of hyaline, septate hyphae that fragment into oval or rectangular arthroconidia.  Some blastoconidia may be seen.  The colonies are usually raised and have a waxy appearance, which develop radial furrows and irregular folds.

Cutaneotrichosporon species are often isolated from human and animal sources as well as clinical specimens, some of them being associated with opportunistic infections. It is also worth mentioning that their ability to grow at 37 C is variable. Importantly, all species are resistant to echinocandins and other classes of antifungal agents (Arendrup et al. 2014).

Note: Genus identification is mandatory for clinical management and should be performed and provided in a timely manner. Species identification remains difficult and requires molecular analysis or MALDI-TOF-MS (with an extensive database) (Arendrup et al. 2015).

Molecular identification:  Species identification requires sequence analysis of the D1/D2 domains and the ITS 1 + 2 regions of the rDNA (Sugita et al. 1999, Arendrup et al. 2015).

MALDI-TOF-MS:  appears to be a promising identification tool (with an extensive database) (Kolecka et al. 2013).

References:  Kurtzman and Fell (1988), Gueho et al. (1992), de Hoog et al. (2000), Rodriguez-Tudela et al.(2005), Chagas-Neto et al. (2008), Guo et al. (2011), Xiao et al. (2013), Liu et al. (2015).

Species descriptions

  • Cutaneotrichosporon cutaneum

    Synonymy: Trichosporon cutaneum

    RG-2 organism.

    Morphological description: 
    Colonies are cream-coloured, cerebriform, glabrous, with radial furrows and irregular folds. Budding cells abundant in primary cultures; hyphae developing in older cultures. Arthroconidia are cylindrical to ellipsoidal. Appressoria absent. This species assimilates melibiose; not tolerant to 0.1% (variable tolerance to 0.01%) cycloheximide. No growth at 37C. Uncommon species usually associated with superficial infections.

    Physiological Tests: + Positive, - Negative, v Variable, w Weak, s Slow, nd No Data
    Glucose + Melibiose + L-Rhamnose + D-Glucitol +
    Galactose + Raffinose + D-Glucosamime v 𝝰-M-D-Glucoside +
    L-Sorbose v Melezitose + N-A-D-glucosamine + D-Gluconate +
    Sucrose + Soluble Starch + Glycerol + DL-Lactate +
    Maltose + D-Xylose + Erythritol + myo-Inositol +
    Cellobiose + L-Arabinose + Ribitol + Nitrate -
    Trehalose + D-Arabinose v Galactitol - 2-K-D-Gluconate +
    Lactose + D-Ribose + D-Mannitol + D-Glucuronate +

  • Cutaneotrichosporon dermatis

    Synonymy: Trichosporon dermatis

    Morphological description: 
    Colonies (SDA) are yellowish-white, semi-shiny, butyrous and wrinkled, and have a fringed margin.  Yeast cells are ovoid, ellipsoidal or elongate, and occur singly or in pairs.  Hyphae disarticulate into cylindrical arthroconidia.  This species cannot be distinguished reliably from C. mucoides using standard carbon assimilation characteristics.  Growth at 37C.  Uncommon species usually associated with human skin and hypersensitivity pneumonitis. 

    RG-1 organism.

    Physiological Tests: + Positive, - Negative, v Variable, w Weak, s Slow, nd No Data
    Glucose + Melibiose + L-Rhamnose + D-Glucitol +
    Galactose + Raffinose + D-Glucosamime + 𝝰-M-D-Glucoside +
    L-Sorbose + Melezitose + N-A-D-glucosamine nd D-Gluconate +
    Sucrose + Soluble Starch + Glycerol + DL-Lactate +
    Maltose + D-Xylose + Erythritol + myo-Inositol +
    Cellobiose + L-Arabinose + Ribitol + Nitrate -
    Trehalose + D-Arabinose + Galactitol + 2-K-D-Gluconate +
    Lactose + D-Ribose + D-Mannitol + D-Glucuronate +

  • Cutaneotrichosporon jirovecii

    Synonymy: Trichosporon jirovecii

    Morphological description: 
    Colonies (SDA) are whitish to pale yellow, semi-shiny, smooth, slightly cerebriform near the bottom, and has a fringed margin.  Yeast cells are ovoid, ellipsoidal or elongate, and occur singly, in pairs or in clusters.  Lateral globose conidia develop on hyphae.  Arthroconidia are cylindrical and form lateral globose blastoconidia.  This species is unable to assimilate ribitol.  No growth at 37C.  Originally isolated from human nails, rarely isolated from clinical specimens such as skin or urine.  

    RG-1 organism.

    Physiological Tests: + Positive, - Negative, v Variable, w Weak, s Slow, nd No Data
    Glucose + Melibiose + L-Rhamnose v D-Glucitol +
    Galactose + Raffinose + D-Glucosamime - 𝝰-M-D-Glucoside +
    L-Sorbose v Melezitose + N-A-D-glucosamine nd D-Gluconate +
    Sucrose + Soluble Starch + Glycerol + DL-Lactate +
    Maltose + D-Xylose + Erythritol + myo-Inositol +
    Cellobiose + L-Arabinose + Ribitol - Nitrate -
    Trehalose + D-Arabinose - Galactitol + 2-K-D-Gluconate +
    Lactose + D-Ribose + D-Mannitol + D-Glucuronate +

  • Cutaneotrichosporon mucoides

    Synonymy: Trichosporon mucoides

    Morphological description: 
    Colonies are moist and glabrous, white, cerebriform, heaped and folded. Budding cells present in primary cultures. Broadly clavate, terminal or lateral blastoconidia often present, becoming thick-walled with age. Arthroconidia are barrel-shaped. Appressoria absent. This species assimilates melibiose and is tolerant to 0.01% (variable tolerance to 0.1%) cycloheximide. Growth at 37C. Common species associated with superficial infections, white piedra and onychomycosis.

    RG-2 organism. 

    Physiological Tests: + Positive, - Negative, v Variable, w Weak, s Slow, nd No Data
    Glucose + Melibiose + L-Rhamnose + D-Glucitol +
    Galactose + Raffinose + D-Glucosamime + 𝝰-M-D-Glucoside +
    L-Sorbose + Melezitose + N-A-D-glucosamine + D-Gluconate +
    Sucrose + Soluble Starch + Glycerol + DL-Lactate +
    Maltose + D-Xylose + Erythritol + myo-Inositol +
    Cellobiose + L-Arabinose + Ribitol + Nitrate -
    Trehalose + D-Arabinose + Galactitol + 2-K-D-Gluconate +
    Lactose + D-Ribose + D-Mannitol + D-Glucuronate +
     
    Antifungal susceptibility: Cutaneotrichosporon mucoides (Australian national data); MIC µg/mL.
      No ≤0.016 0.03 0.06 0.125 0.25 0.5 1 2 4 8 ≥16
    AmB 18           3 7 5 3    
    FLU 18           2 6 2 5   3
    VORI 18     5 5 1 4 2 1      
    POSA 18       3 6 6 3        
    ITRA 18       5 8 4 1