Identification of Trichosporon spp. strains by sequencing D1/D2 region and sub-typing by sequencing ribosomal intergenic spacer region of ribosomal DNA

Metabolic and phenotypic plasticity may contribute for the higher virulence of Trichosporon asahii over other Trichosporonaceae members

BACKGROUND

The Trichosporonaceae family comprises a large number of basidiomycetes widely distributed in nature. Some of its members, especially Trichosporon asahii, have the ability to cause human infections. This ability is related to a series of virulence factors, which include lytic enzymes production, biofilm formation, resistance to oxidising agents, melanin and glucuronoxylomannan in the cell wall, metabolic plasticity and phenotypic switching. The last two are poorly addressed within human pathogenic Trichosporonaceae.

OBJECTIVE

These factors were herein studied to contribute with the knowledge of these emerging pathogens and to uncover mechanisms that would explain the higher frequency of T. asahii in human infections.

METHODS

We included 79 clinical isolates phenotypically identified as Trichosporon spp. and performed their molecular identification. Lactate and N-acetyl glucosamine were the carbon sources of metabolic plasticity studies. Morphologically altered colonies after subcultures and incubation at 37°C indicated phenotypic switching.

RESULTS AND CONCLUSION

The predominant species was T. asahii (n = 65), followed by Trichosporon inkin (n = 4), Apiotrichum montevideense (n = 3), Trichosporon japonicum (n = 2), Trichosporon faecale (n = 2), Cutaneotrichosporon debeurmannianum (n = 1), Trichosporon ovoides (n = 1) and Cutaneotrichosporon arboriforme (n = 1). T. asahii isolates had statistically higher growth on lactate and N-acetylglucosamine and on glucose during the first 72 h of culture. T. asahii, T. inkin and T. japonicum isolates were able to perform phenotypic switching. These results expand the virulence knowledge of Trichosporonaceae members and point for a role for metabolic plasticity and phenotypic switching on the trichosporonosis pathogenesis.

Molecular Identification, Genotyping, Phenotyping, and Antifungal Susceptibilities of Medically Important Trichosporon, Apiotrichum, and Cutaneotrichosporon Species

Recently, Trichosporon taxonomy has been reevaluated and new genera of the Trichosporonaceae family have been described. Here, 26 clinical isolates were submitted for identification via sequencing of the intergenic space 1 (IGS1) region, genotyping, and investigation of virulence factors. Antifungal susceptibility was determined using the CLSI broth microdilution method for fluconazole (FLC), itraconazole (ITC), and amphotericin B (AMB). Of these, 24 isolates were identified, including 12 T. asahii, 4 T. inkin, 3 T. faecale, 1 T. coremiiforme, 1 T. japonicum, 2 Cutaneotrichosporon dermatis (formerly T. dermatis), and 1 Apiotrichum mycotoxinivorans (formerly T. mycotoxinivorans). Species-level identification of 2 isolates was not successful; they were described as Trichosporon sp. We observed optimal colonial development at 35-40 °C. Lipase was the major extracellular enzyme produced (100%); caseinase was not produced (0%). Biofilms were produced by all isolates (classified as low). High AMB minimum inhibitory concentration (MIC) was observed, with all strains resistant. Fluconazole was the most active drug among the antifungals tested. However, high MICs for FLC were observed in C. dermatis and A. mycotoxinivorans species, which also showed resistance to ITC and AMB. This study, conducted in the Northern region of Brazil, identified 5 Trichosporon species along with C. dermatis and A. mycotoxinivorans and demonstrated their pathogenic potential through their ability to produce important virulence factors. This may contribute to our understanding of the epidemiology and factors related to the pathogeneses of species in the Trichosporonaceae family.

Sequence-based identification, genotyping and virulence factors of Trichosporon asahii strains isolated from urine samples of hospitalized patients (2011-2016)

INTRODUCTION

Trichosporon asahii is the most common species that causes trichosporonosis.

MATERIALS AND METHODS

In the present study, a collection of 68T. asahii strains recovered from hospitalized patients urine samples between 2011 and 2016 was examined. T. asahii strains were identified by sequencing the intergenic spacer 1 region (IGS1) and genotyped. In addition, proteinase, phospholipase, esterase, haemolytic activity, and biofilm formation of a total of T. asahii strains were investigated.

RESULTS

The predominant genotype was 1 (79.3%) and followed by 5 (8%), 3 (6.9%), 6 (3.4%), 4 (1.1%), 9 (1.1%). In none of the 68 strains, proteinase and phospholipase activities could be detected, while all were found to be esterase positive. Biofilm production and hemolytic activity were detected in 23.5 and 97% respectively.

DISCUSSION

Our results indicated that six genotypes were (1, 5, 3, 6, 4, 9) present among T. asahii strains and no property was found to associate with a genotype, in terms of virulence factors.

Performance and cost analysis of matrix-assisted laser desorption ionization-time of flight mass spectrometry for routine identification of yeast

Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry was compared to phenotypic testing for yeast identification. MALDI-TOF mass spectrometry yielded 96.3% and 84.5% accurate species level identifications (spectral scores, ≥ 1.8) for 138 common and 103 archived strains of yeast. MALDI-TOF mass spectrometry is accurate, rapid (5.1 min of hands-on time/identification), and cost-effective ($0.50/sample) for yeast identification in the clinical laboratory.