Laboratory identification and in vitro analysis of antifungal susceptibility of Trichosporon asahii and Stephanoascus ciferrii

LIN Sijia; YUAN Kaixuan

doi:10.3969/j.issn.1673-3827.2024.02.008

Abstract：Objective To investigate the laboratory identification and in vitro antifungal susceptibility of T.asahii and S.ciferrii,so as to provide evidence for clinical treatment,laboratory identification and epidemiological study.Methods Two rare yeast-like fungi were collected from Guangdong Provincial People's Hospital from January 2017 to September 2022,54 strains of T.asahii and 23 strains of S.ciferrii were revived and identified by morphology,physiology,biochemistry,and MALDI-TOF MS.The minimum inhibitory concentrations of 5-flucytosine,amphotericin B,fluconazole,itraconazole and voriconazole to all strains were tested by FUNGUS-3 MIC method.Results T.asahii mainly infected people aged above 65 years old(46.30% ),with wound area(27.78% )and urinary tract(22.22% )being the main sites of infection.These patients are mainly distributed in surgery(35.19% )and medicine(35.19% ).However,The patients with S.ciferrii infec-tion were mainly aged 18-40 years old(39.13% )and 41-65 years old(47.83% ).The infection site was mainly in the ear ca-nal(78.26% ),which was distributed in the otorhinolaryngological surgery area(60.87% )and the otorhinolaryngological clinic(26.09% ).In terms of morphological identification,both fungi were white raised colonies,embedded on the surface of the medium,T.asahii growth faster than S.ciferrii.After Gram staining of T.asahii,arthrospore,articular hyphae,eu-hyphae,pseudohyphae and blastospore were observed under microscope.In contrast,in S.ciferrii,branching septate hyphae and unicellular,oval blastophores were seen.In terms of biochemical identification,T.asahii urease was positive and could hydrolyze heptagenin,assimilating multiple carbohydrate compounds,while S.ciferrii urease was negative and does not hydrolyze heptagenin,but could assimilate multiple carbohydrates.In terms of mass spectrometry identification,the identification rates of T.asahii and S.ciferrii were 96.30% and 91.30% ,respectively,with good identification results.In vitro susceptibility results of both fungi showed high MIC values to 5-flucytosine,and 54 strains(100% )of T.asahii had MIC value≥4 μg/mL.The MIC values of 23 strains(100% )of S.ciferrii to 5-flucytosine were ≥4 μg/mL.At the same time,high MIC values of fluconazole against the two fungi should be warned.The MIC values of 7 strains(12.97% )of T.asahii were≥4 μg/mL,and 16 strains(69.56% )of S.ciferrii had MIC values≥16 μg/mL.Amphotericin B,itraconazole and voriconazole showed lower MIC values(≤2 μg/mL)and better in vitro activity.Conclusions There are different char-acteristics in laboratory identification and drug susceptibility results of T.asahii and S.ciferrii.The accurate identification and the development of antifungal susceptibility test in vitro are of great significance for the rational use of antibiotics in clin-ical practice,and can also provide reference for clinical treatment,laboratory identification process and epidemiological study.