Trichosporon dohaense, a rare pathogen of human invasive infections, and literature review

Shu-Ying Yu,1–3 Li-Na Guo,1,3 Meng Xiao,1,3 Timothy Kudinha,4,5 Fanrong Kong,4 He Wang,1,3 Jing-Wei Cheng,1–3 Meng-Lan Zhou,1–3 Hui Xu,6 Ying-Chun Xu1–3 1Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China; 2Graduate School, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China; 3Beijing Key Laboratory for Mechanisms Research and Precision Diagnosis of Invasive Fungal Diseases, Beijing, China; 4Centre for Infectious Diseases and Microbiology Laboratory Services, ICPMR – Pathology West, University of Sydney, Westmead Hospital, Westmead, NSW, Australia; 5Centre for Infectious Diseases and Microbiology Laboratory Services, Westmead Hospital, Westmead, NSW, Australia; 6Department of Clinical Laboratory, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China Background: Trichosporon dohaense is a rare fungal species that has not been described in human invasive infections. Patients and methods: In this study, we investigated two T. dohaense isolates from patients with invasive infections in two hospitals in China, as part of the China Hospital Invasive Fungal Surveillance Net (CHIF-NET) program. Both patients were under immunocompromised conditions. Results: On chromogenic agar, T. dohaense isolates were dark blue, similar to the color of Candida. tropicalis, but the characteristic moist colony appearance was quite different from that of T. asahii. The two isolates were misidentified as T. asahii and T. inkin by the VITEK 2 YST system. The rDNA internal transcribed spacer (ITS) region and the D1/D2 domain sequences of the two T. dohaense isolates were 100% identical to T. dohaense type strain CBS10761T. The sequence of the intergenic spacer region-1 also clearly distinguished the species. Of the three matrix-assisted laser desorption/ionization time-of-flight mass spectrometry systems, Bruker Biotyper and Autobio MS correctly identified the two isolates to species level, whereas Vitek MS systems misidentified them as T. ovoides or T. asteroides. Echinocandins exhibited no in vitro activities against the two T. dohaense isolates. In addition, the isolates exhibited intermediate susceptibility to fluconazole (with minimal inhibitory concentrations [MICs] of 8 and 16 µg/mL) and itraconazole, voriconazole, and posaconazole (MICs of 0.25–1 µg/mL). T. dohaense demonstrated susceptibility to amphotericin B with MIC of 1 µg/mL. The MICs of fluconazole and voriconazole in our study were higher than the MIC50 of 62 for T. asahii isolates (4 and 0.064 µg/mL) in the CHIF-NET program. Conclusion: This case study points to a possible emergence of T. dohaense as an opportunistic human invasive fungal pathogen, and the reduced susceptibility should be noted. Keywords: Trichosporon dohaense, invasive infection, emerging pathogen, identification, reduced susceptibilit