Characterization of the medically important yeast Trichosporon mucoides and its close sister Trichosporon dermatis by traditional and advanced technologies

Abstract

CorrespondenceSung-Oui Suh ssuh@atcc.org ATCC, 10801 University Blvd., Manassas, VA 20110, USA Trichosporon dermatis is a causative agent of several mycoses in immunocompromised patients but is often misidentified as Trichosporon mucoides due to their phenotypic resemblance. In order to evaluate the current identification keys for these species and to develop a rapid and reliable identification method, 11 strains of these yeasts were fully characterized in this study by traditional and advanced technologies. DNA sequences of the internal transcribed spacer (ITS), IGS1, and D1/D2 regions identified six of the yeasts as T. dermatis that were previously known as T. mucoides, including ATCC 204094 that has been used as the quality-control strain of T. mucoides for the VITEK 2 system and other commercial yeast identification kits. These two species could not be differentiated reliably by any previously known phenotypic keys for the species, such as growth patterns on ethylamine, phloroglucinol and tyramine, or by the VITEK 2 system. On the other hand, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) proved to be a rapid and reliable identification tool for the two closely related yeasts. With newly added superspectra from fully authenticated reference strains, the VITEK MS system using MALDI-TOF MS successfully separated strains of T. dermatis and T. mucoides at a similarity level of approximately 67 % for the mass spectra data, and could identify these strains at the species level with 100 % accuracy in repeated tests. Furthermore, the in vitro susceptibility results indicated that itraconazole, posaconazole and voriconazole were more effective against both T. mucoides and T. dermatis than the other antifungal agents tested in this study. INTRODUCTIONTrichosporon mucoides is a clinically important yeast species that causes disseminated infections (Boekhout & Guého, 2003; Guého et al., 1994). Since Guého et al. (1992) described the species to accommodate an atypical group of yeasts in Trichosporon beigelii, several studies have reported T. mucoides as a causative agent of white piedra and onychomycosis, as well as fungal septicaemia in humans (e.g. Capoor et al., 2013; Guého et al., 1994; de Hoog & Guého, 2005;Lacasse & Cleveland, 2009;Mayser et al., 1996). Trichosporon dermatis, a sibling species of T. mucoides, was recognized by Sugita et al. (2001a) from a yeast strain that was originally identified as Cryptococcus humicola but was later distinguished from the species sequence comparison of the D1/D2 region of the large subunit of the 28S rRNA gene. The yeast is often isolated from infected skin or the blood of immunocompromised patients (Fan et al., 2011; Hashino et al., 2013;Ruan et al., 2009; Sugita et al., 2001a) as well as from environmental samples, such as households with summer-type hypersensitivity pneumonitis patients or certain soils (Gujjari et al., 2011;Sugita, 2011; Sugita et al., 2001b). Both T. mucoides and T. dermatis are well recognized in the genus...

Prosthetic valve endocarditis by Trichosporon mucoides

“…However, the VITEK 2 system may be unreliable for the identification of Trichosporon species other than T asahii [ 25 ] ; therefore, MALDI-TOF may enable rapid identification of fungal species, as an alternative to polymerase chain reaction-based molecular methods. [ 26 ]…”

“…[ 27 ] However, echinocandins, which have a robust anti- Candida biofilm effect, are inadequate for Trichosporon endocarditis because of intrinsic resistance, as observed in our patient. [ 26 ] We applied liposomal amphotericin B plus voriconazole for 3 weeks, followed by voriconazole monotherapy for 3 months with surgery. T mucoides is more resistant to fluconazole in vitro, compared to other species.…”