Current knowledge of Trichosporon spp. and Trichosporonosis

Abstract

Trichosporon spp. are basidiomycetous yeast-like fungi found widely in nature. Clinical isolates are generally related to superficial infections. However, this fungus has been recognized as an opportunistic agent of invasive infections, mostly in cancer patients and those exposed to invasive medical procedures. It is possible that the ability of Trichosporon strains to form biofilms on implanted devices, the presence of glucuronoxylomannan in their cell walls, and the ability to produce proteases and lipases are all factors likely related to the virulence of this genus and therefore may account for the progress of invasive trichosporonosis. Disseminated trichosporonosis has been increasingly reported worldwide and represents a challenge for both diagnosis and species identification. Phenotypic identification methods are useful for Trichosporon sp. screening, but only molecular methods, such as IGS region sequencing, allow the complete identification of Trichosporon isolates at the species level. Methods for the diagnosis of invasive trichosporonosis include PCR-based methods, Luminex xMAP technology, and, more recently, proteomics. Treating patients with trichosporonosis remains a challenge because of limited data on the in vitro and in vivo activities of antifungal drugs against clinically relevant species of the genus. Despite the mentioned limitations, the use of antifungal regimens containing triazoles appears to be the best therapeutic approach.

Fig. 1.

Schematic structure of the rRNA gene of Trichosporon spp. ITS, internal transcribed spacer; IGS, intergenic spacer region. The total length of the rDNA locus is approximately 7,850 bp, and the IGS1 region comprises 485 bp.

Fig. 2.

Distribution of T. asahii genotypes, based on IGS1 sequences of clinical isolates, in the United States, Spain, Brazil, Thailand, Japan, and Turkey (25, 89, 119, 152, 169, 172).