Identification of heparin-binding proteins expressed on Trichosporon asahii cell surface.

Trichosporon asahii is a pathogenic yeast that cause trichosporonosis. T. asahii exhibits several colony morphologies, such as white (W)- or off-white (O)-type, which may affect virulence. In this study, we compared the expression pattern of heparin-binding proteins in various colony morphologies and identified heparin-binding protein in T. asahii. Surface plasmon resonance analysis revealed that cell surface molecules attached more strongly to heparin in W- than O-type cells. We purified and identified a heparin-binding protein strongly expressed in W-type cells using heparin-Sepharose beads, named it heparin-binding protein 1 (HepBP1), and expressed Flag-tagged HepBP1 in mammalian cells. The heparin-binding ability of Flag-tagged HepBP1 was confirmed by pulldown assay using heparin-Sepharose beads. Thus, HepBP1 is a heparin-binding protein on T. asahii cell surface. These results suggest that several T. asahii cell surface proteins interact with glycosaminoglycans; therefore, they could contribute to infection.

Unveiling Trichosporon austroamericanum sp. nov.: A Novel Emerging Opportunistic Basidiomycetous Yeast Species.

During an epidemiological survey, a potential novel species within the basidiomycetous yeast genus Trichosporon was observed. The clinical strain was obtained from a urine sample taken from a Brazilian kidney transplant recipient. The strain was molecularly identified using the intergenic spacer (IGS1) ribosomal DNA locus and a subsequent phylogenetic analysis showed that multiple strains that were previously reported by other studies shared an identical IGS1-genotype most closely related to that of Trichosporon inkin. However, none of these studies provided an in-depth characterization of the involved strains to describe it as a new taxon. Here, we present the novel clinically relevant yeast for which we propose the name Trichosporon austroamericanum sp. nov. (holotype CBS H-24937). T. austroamericanum can be distinguished from other siblings in the genus Trichosporon using morphological, physiological, and phylogenetic characters.

Aspects related to biofilm production and antifungal susceptibility of clinically relevant yeasts of the genus Trichosporon.

Trichosporonosis corresponds to a systemic fungal disease that leads to high mortality rates and is frequently associated with medical devices. It affects immunosuppressed patients in particular and is strongly linked to acquired human immunodeficiency, organ and tissue transplants, and malignant hematologic diseases such as leukemia and lymphomas. Trichosporon infections have been increasingly reported worldwide; however, little information is available either about their characteristics or the causative microorganism. Thus, the aims of the present study were: to investigate 59 yeasts of the genus Trichosporon by verifying the biofilm formation capacity of isolates; to analyze the susceptibility patterns of planktonic cells against the antifungals fluconazole, itraconazole, amphotericin-B, voriconazole, and caspofungin by comparing European Committee for Antimicrobial Susceptibility Testing (EUCAST) broth microdilution technique with the commercial method Etest; and to assess the susceptibility patterns of biofilm cells (sessile) against the same antifungals through broth microdilution. The ability to form biofilm on the surface of polystyrene plates was noted for all isolates, and 54.3% of samples were considered strong producers. Comparison between the antifungal susceptibility techniques evidenced that Etest showed higher and discordant minimum inhibitory concentrations (MICs) from those obtained by the microdilution method, especially for fluconazole, itraconazole, and caspofungin. Considering the susceptibility of biofilms, most species had high MIC50 and MIC90 against the tested antifungals, showing 4-to-66-fold higher concentrations for amphotericin B and 2-to-33-fold greater concentrations for caspofungin. These results highlight the importance of further studies with Trichosporon spp. for comparison between laboratory findings and in vivo response, considering both the susceptibility tests and the behavior of biofilm cells against drugs.

This study investigated 59 isolates of the medically important yeast Trichosporon in relation to their ability to form biofilms and the susceptibility of biofilms to antifungal agents. All isolates were able to produce biofilms and biofilms showed lower antifungal susceptibility.

Tacrolimus inhibits stress responses and hyphal formation via the calcineurin signaling pathway in Trichosporon asahii.

The pathogenic fungus Trichosporon asahii causes fatal deep-seated mycosis in immunocompromised patients. Calcineurin, which is widely conserved in eukaryotes, regulates cell growth and various stress responses in fungi. Tacrolimus (FK506), a calcineurin inhibitor, induces sensitivity to compounds that cause stress on the cell membrane and cell wall integrity. In this study, we demonstrated that FK506 affects stress responses and hyphal formation in T. asahii. In silico structural analysis revealed that amino acid residues in the binding site of the calcineurin-FKBP12 complex that interact with FK506 are conserved in T. asahii. The growth of T. asahii was delayed by FK506 in the presence of SDS or Congo red but not in the presence of calcium chloride. FK506 also inhibited hyphal formation in T. asahii. A mutant deficient of the cnb gene, which encodes the regulatory subunit B of calcineurin, exhibited stress sensitivities on exposure to SDS and Congo red and reduced the hyphal forming ability of T. asahii. In the cnb-deficient mutant, FK506 did not increase the stress sensitivity or reduce hyphal forming ability. These results suggest that FK506 affects stress responses and hyphal formation in T. asahii via the calcineurin signaling pathway.

Differences of clinical characteristics and outcome in proven invasive Trichosporon infections caused by asahii and non-asahii species.

BACKGROUND: Trichosporon is an emerging yeast that causes invasive infections in immunocompromised patients experiencing prolonged hospitalisation, indwelling venous catheters and neutropenia. METHODS: This retrospective observational cohort study analysed invasive Trichosporon infections (ITIs) occurring between January 2005 and December 2022 at three tertiary hospitals and compared the clinical characteristics and prognostic factors of ITIs caused by Trichosporon asahii and non-T. asahii spp. After evaluating 1067 clinical isolates, we identified 46 patients with proven ITIs, defined as cases in which Trichosporon was isolated from blood, cerebrospinal fluid, or sterile tissues. RESULTS: The patients were separated into T. asahii and non-T. asahii groups containing 25 and 21 patients, respectively, all of which except one were immunocompromised. During this period, both the number of clinical isolates and patients with ITIs (mainly T. asahii) increased; whereas, cases involving non-T. asahii spp. decreased. Compared with the non-T. asahii group, the T. asahii group had more patients with multiple catheters (84% vs. 33%, p = .001) and those receiving renal replacement therapy (48% vs. 14%, p = .005). The all-cause 28-day mortality rate after ITI in the T. asahii group (44%) was significantly higher than in the non-T. asahii group (10%, Log-rank p = .014). The multivariate Cox regression model revealed that T. asahii (reference, non-T. asahii spp.; aHR = 4.3; 95% CI = 1.2-15.2, p = .024) and neutropenia for 5 days or more (aHR = 2.2, 95% CI = 1.5-3.6, p = .035) were independent factors in the 28-day mortality after ITI. CONCLUSION: The proven ITIs due to T. asahii produced more unfavourable outcomes compared with ITIs caused by non-T. asahii spp.

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.

Identification of Clinical Trichosporon asteroides Strains by MALDI-TOF Mass Spectrometry: Evaluation of the Bruker Daltonics Commercial System and an In-House Developed Library.

Trichosporon asteroides is an emerging yeast-like pathogen commonly misidentified by commercial biochemical identification systems. We evaluated the performance of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the identification of 21 clinical T. asteroides strains using the Bruker Daltonics database (BDAL) and an in-house developed library. Mass spectra were obtained by the FlexControl system v.3.4, and characterizations were performed in the Biotyper BDAL database v.4.1 and the developed in-house library. Species identification for T. asteroides failed as all 21 strains were misidentified as T. japonicum (log-scores 1.89-2.19). Extending the existing database was crucial to achieving 100% correct species-level identification and accurate distinction between species. Our results indicate that the commercial BDAL database has no discriminatory power to distinguish between T. japonicum and T. asteroides. Whereas improvement of the current BDAL database is pending, we strongly advise system users not to exclude the possibility of the failure to report T. asteroides.

EQUAL Trichosporon Score 2022: an ECMM score to measure QUALity of the clinical management of invasive Trichosporon infections.

BACKGROUND: Invasive infections due to Trichosporon spp. are life-threatening opportunistic fungal infections that require complex clinical management. Guidelines assist clinicians but can be challenging to comply with. OBJECTIVES: To develop a scoring tool to facilitate and quantify adherence to current guideline recommendations for invasive trichosporonosis. METHODS: We reviewed the current guideline for managing rare yeast infections (ECMM, ISHAM and ASM). The most important recommendations for diagnosis, treatment and follow-up were assembled and weighted according to their strength of recommendation and level of evidence. Additional items considered highly relevant for clinical management were also included. RESULTS: The resulting EQUAL Trichosporon Score 2022 comprises 18 items, with a maximum score of 39 points. For diagnostics, seven or eight items, depending on whether organ involvement is present or not, apply, resulting in a maximum of 18 or 21 points. Recommendations on diagnostics include imaging, infectious diseases expert consultation, culture, microscopy, molecular techniques, histopathology, and susceptibility testing. For treatment, six recommendations with a maximum of ten points were identified, with two additional points for organ involvement and one point for second-line treatment in uncontrolled disease. Treatment recommendations include immediate initiation, source control, pharmacological treatment, therapeutic drug monitoring, treatment duration and surgical intervention. Follow-up comprises two items with five points maximum, covering follow-up blood cultures and imaging. CONCLUSIONS: The EQUAL Trichosporon Score weighs and aggregates factors recommended for optimal management of Trichosporon infections. It provides a tool for antifungal stewardship as well as for measuring guideline adherence, but remains to be correlated with patient outcomes.

Orthopedic infections due to Trichosporon species: Case series and literature review.

Reports of orthopedic fungal infections caused by Trichosporon species are extremely scarce, thus we aimed to describe a case series and review the cases published in the literature. Patients were retrospectively included if a previous culture of bone, joint, or soft tissues had resulted positive for Trichosporon species along with a clinical diagnosis of an orthopedic infection. Eight patients were included with diverse orthopedic conditions, most of them cases of osteomyelitis. The main isolated species was Trichosporon asahii. All patients were treated with antifungals, mainly voriconazole, and surgical management, resulting in high rates of clinical improvement and low associated mortality.

Reports of orthopedic infections caused by Trichosporon species are scarce. We described a case series of orthopedic infections caused by Trichosporon species and reviewed the previous published cases in the literature. We observed a high rate of clinical improvement and a low associated mortality.

Breakthrough Trichosporon asahii in a Patient With New Diagnosis B-ALL on Echinocandin Prophylaxis: A Case Report.

Invasive fungal disease is a difficult to diagnose complication of therapy in patients with hematologic malignancy. Antifungal prophylaxis is recommended in high-risk populations, but its use in other populations is less clear. This brief report describes a patient with Trisomy 21 on caspofungin prophylaxis who died of disseminated Trichosporon asahii during induction therapy for new diagnosis low-risk B-cell acute lymphoblastic leukemia, accompanied by a review of similar cases in the literature. Her case highlights the utility of relatively novel diagnostic modalities and reinforces the need for caution in placing patients on antifungal prophylaxis.

Genotyping, antifungal susceptibility testing, and biofilm formation of Trichosporon spp. isolated from urine samples in a University Hospital in Bangkok, Thailand.

The basidiomycetes yeast Trichosporon is widespread in the natural environment, but can cause disease, mainly in immunocompromised patients. However, there have been only few studies about this infection in Thailand. In this study, we characterized 53 Trichosporon spp. isolated from urine samples from patients admitted to a single hospital in Bangkok, Thailand over a one-year period from 2019 to 2020. The strains were identified using colony morphology, microscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and nucleotide sequence analysis of intergenic spacer 1 (IGS1). Fifty-one isolates were Trichosporon asahii, and the remaining isolates were Trichosporon inkin and other Trichosporon species. Three genotypes of IGS1-1, 3, and 7 were observed among T. asahii. The sensitivity of the yeasts to the antifungal drugs amphotericin B, fluconazole, and voriconazole ranged from 0.25 to >16 µg ml-1, 0.5-8 µg ml-1, and 0.01-0.25 µg ml-1, respectively. We investigated biofilm formation by the isolates, and no biofilm production was found in one isolate, low biofilm production in forty-four isolates, and medium biofilm production in six isolates. T. inkin produced biofilms at low levels, and Trichosporon spp. produced biofilms at medium levels. This research increases our understanding of the molecular epidemiology of Trichosporon spp. isolated from one university hospital in Bangkok, Thailand, and reveals their genetic diversity, antifungal susceptibility profiles, and capacity for in vitro biofilm production.

[A CASE OF SUMMER-TYPE HYPERSENSITIVITY PNEUMONITIS DURING IMMUNOSUPPRESSIVE TREATMENT FOR SYSTEMIC SCLEROSIS].

A 70-year-old woman undergoing long-term treatment for systemic scleroderma and secondary Sjögren syndrome developed fever during tapering of steroids. Chest CT showed centrilobular granular shadow and ground glass opacities. The pathology of transbronchial lung biopsy and the findings of bronchoalveolar lavage fluid were consistent with hypersensitivity pneumonitis and positive for anti-Trichosporon asahii antibody. Because her symptoms and imaging findings improved after house cleaning, she was diagnosed with summertype hypersensitivity pneumonitis. When lung lesions are found in patients with collagen disease, it is necessary to distinguish various diseases. In particular, allergic diseases can be difficult to diagnose by steroid therapy. In order to make an accurate diagnosis, medical history and image interpretation should be performed carefully and histologically searched as much as possible.

Correlation of Trichosporon asahii Genotypes with Anatomical Sites and Antifungal Susceptibility Profiles: Data Analyses from 284 Isolates Collected in the Last 22 Years across 24 Medical Centers.

Trichosporon asahii is an opportunistic fungal pathogen that can cause severe infections with high mortality rates. Azole derivatives are the best-targeted therapy for T. asahii invasive infections, but azole-resistant isolates have been reported. To investigate peculiarities in the antifungal susceptibility profile (ASP) of T. asahii clinical isolates, we analyzed the genotype distribution, isolation sources, and ASP of 284 strains collected from 1997 to 2019 in different Brazilian medical centers. Species identification and genotype characterization were performed by analysis of the intergenic spacer (IGS1) region of the ribosomal DNA (rDNA). Antifungal susceptibility testing (AST) for amphotericin B and azoles was with the CLSI M27, 4th edition, microdilution broth method. Trends in the ASP of Brazilian T. asahii isolates were investigated using epidemiological cutoff values. Five different genotypes were found among the 284 isolates tested (G1, 76%; G3, 10%; G4, 3%; G5, 7%; and G7, 4%). The isolates were collected mainly from urine (55%) and blood/catheter tip samples (25%) where G1 was the most frequent genotype found (P < 0.05). The G7 isolates exhibited the highest MIC90 values for azoles compared to those for the other genotypes (P < 0.05). Genotype 7 isolates also contributed to the increasing rates of voriconazole non-wild-type isolates found in recent years (P = 0.02). No significant differences were found among the AST results generated by isolates cultured from different anatomical sites. Monitoring T. asahii genotype distributions and antifungal susceptibility profiles is warranted to prevent the spread of azole-resistant isolates.

Multidrug-resistant Trichosporon species: underestimated fungal pathogens posing imminent threats in clinical settings.

Species of Trichosporon and related genera are widely used in biotechnology and, hence, many species have their genome sequenced. Importantly, yeasts of the genus Trichosporon have been increasingly identified as a cause of life-threatening invasive trichosporonosis (IT) in humans and are associated with an exceptionally high mortality rate. Trichosporon spp. are intrinsically resistant to frontline antifungal agents, which accounts for numerous reports of therapeutic failure when echinocandins are used to treat IT. Moreover, these fungi have low sensitivity to polyenes and azoles and, therefore, are potentially regarded as multidrug-resistant pathogens. However, despite the clinical importance of Trichosporon spp., our understanding of their antifungal resistance mechanisms is quite limited. Furthermore, antifungal susceptibility testing is not standardized, and there is a lack of interpretive epidemiological cut-off values for minimal inhibitory concentrations to distinguish non-wild type Trichosporon isolates. The route of infection remains obscure and detailed clinical and environmental studies are required to determine whether the Trichosporon infections are endogenous or exogenous in nature. Although our knowledge on effective IT treatments is rather limited and future randomized clinical trials are required to identify the best antifungal agent, the current paradigm advocates the use of voriconazole, removal of central venous catheters and recovery from neutropenia.

Comparison of the characteristics of patients with invasive infections and noninvasive infections caused by Trichosporon asahii.

We performed retrospective study to identify the characteristics of invasive Trichosporon asahii infection. A total of 102 patients with T. asahii were identified including 18 (18%) with invasive infection. Invasive infection was associated with indwelling central venous catheter (94% vs 54%, P = .001), prior antifungal agent use (50% vs 18%, P = .01), hematologic malignancy (33% vs 7%, P = .006), and end-stage renal disease (28% vs 7%, P = .02). Patients with invasive infections had higher in-hospital mortality than patients with noninvasive infections (61% vs 27%, P = .006). Those with the above risk factors should be monitored for the development of invasive T. asahii infection. LAY SUMMARY: Patients with indwelling central venous catheter, prior antifungal agent use, hematologic malignancy, and end-stage renal disease were associated with invasive Trichosporon asahii infection. Patients with invasive infections had higher in-hospital mortality than patients without invasive infection.

Complicated Trichosporon asahii mastoiditis in immunocompetent child.

BACKGROUND: Trichosporon asahii is an opportunistic fungus that causes infections in immunosuppressed patients. It is rarely seen in children and immunocompetent hosts. The mortality rates are still high despite early treatment with proper antifungal drugs. Trichosporon asahii mastoiditis in an immunocompetent child makes this case challenging. CASE PRESENTATION: This report presents a case of Trichosporon asahii mastoiditis which was complicated by transverse sinus thrombosis, in an otherwise healthy 21-month-old girl, and successfully treated with voriconazole. Trichosporon asahii was isolated, in three different occasions, from ear discharge of an immunocompetent healthy child, who presented with prolonged history of fever and received appropriate dosages of multiple types of antimicrobials as an outpatient but without improvement. After 48 h of starting the Voriconzole; post auricular swelling and ear discharge improved significantly. CONCLUSION: A high index of clinical and microbiological suspicion is needed for optimal diagnosis of Trichosporon infection. Trichosporon asahii can also cause infection in immunocompetent individual even without previous history of hospitalization or intervention. We emphasize the importance of early pediatric infectious evaluation and intervention.

Combinatory Effect of ALA-PDT and Itraconazole Treatment for Trichosporon asahii.

BACKGROUND AND OBJECTIVES: Trichosporiosis is an opportunistic infection that includes superficial infections, white piedra, hypersensitivity pneumonitis, and invasive trichosporonosis. The effect of antifungal agents against these infections is largely weakened by drug resistance and biofilms-related virulence. Photodynamic therapy (PDT) is a new therapeutic approach developed not only to combat cancerous lesions but also to treat infectious diseases such as fungal infections. However, there are few studies on the antimicrobial mechanism of 5-aminolevulinic acid PDT (ALA-PDT) in treating Trichosporon. In this work, we explored the possibility of combining ALA-PDT with an antifungal agent to enhance the therapeutic efficacy of Trichosporon asahii (T. asahii) in a clinical setting and in vitro. STUDY DESIGN/MATERIALS AND METHODS: The biofilms of T. asahii were constructed by a 96-well plate-based method in vitro. The planktonic and adherent T. asahii were exposed to different concentrations of photosensitizers and different light doses. After PDT treatment, counting colony-forming units and tetrazolium (XTT) reduction assay were used to estimate the antifungal efficacy. The minimal inhibitory concentration of itraconazole before and after PDT treatment was determined by the broth dilution method, and XTT viability assay was used to detect and evaluate the synergistic potential of ALA-PDT and itraconazole combinations in inhibiting biofilms. Scanning electron microscopy (SEM) was performed to assess the disruption of biofilms. RESULTS: Using combination therapy, we have successfully treated a patient who had a T. asahii skin infection. Further in vitro studies showed that the antifungal effect of ALA-PDT on planktonic and adherent T. asahii was dependent on the concentration of ALA and light dosages used. We also found that the sensitivity of both planktonic and biofilm cells to itraconazole were increased after ALA-PDT. Synergistic effect were observed for biofilms in ALA-PDT and itraconazole-combined treatment. The disruption of biofilms was confirmed by SEM, suggesting that ALA-PDT effectively damaged the biofilms and the destruction was further enhanced by ALA-PDT combination of antifungal agents. CONCLUSIONS: In conclusion, these data suggest that ALA-PDT could be an alternative strategy for controlling infections caused by Trichosporon. The combination therapy of ALA-PDT with itraconazole could result in increased elimination of planktonic cells and biofilms compared with single therapy. All these findings indicate that it could be a promising treatment against trichosporonosis. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Role of arthroconidia in biofilm formation by Trichosporon asahii.

BACKGROUND: Trichosporon asahii is the major causative agent of disseminated and deep-seated trichosporonosis. It is capable of forming biofilms on surfaces, leading to medical device-related infection.Trichosporon asahii may be present as yeast form, hyphae and/or arthroconidia; however, the relationship between its biofilm-forming ability and its morphological transition is unclear. OBJECTIVES: We investigated whether the T. asahii morphological transition contributes to its biofilm formation. We also determined the conditions required to induce each of the morphologies. METHODS: Three high- and three low-biofilm-producing strains (HBS and LBS, respectively) were selected using a biofilm formation assay, and the cell surface hydrophobicity of these six strains was measured. For each strain, the morphology was observed and the number of each morphological form (yeast form, hypha and arthroconidium) was counted to calculate the ratio. Finally, the ability of cells each morphological type to adhere to the polystyrene substrate was evaluated. RESULTS: The HBS exhibited abundant arthroconidia and hyphae; in contrast, the LBS produced mainly hyphae with few or no arthroconidia. The production of hyphae was increased by nitrogen-containing medium, and the production of arthroconidia was increased by nitrogen-deficient medium. Cells incubated under nitrogen-deficient conditions showed higher adherence to a polystyrene surface than those incubated in the presence of nitrogen. CONCLUSION: Arthroconidia of T. asahii play a key role in biofilm formation by promoting cellular adhesion.

MALDI-TOF MS characterisation, genetic diversity and antifungal susceptibility of Trichosporon species from Iranian clinical samples.

BACKGROUND: Trichosporonosis is an emerging fungal infection caused by Trichosporon species, a genus of yeast-like fungi, which are frequently encountered in human infections ranging from mild cutaneous lesions to fungemia in immunocompromised patients. The incidence of trichosporonosis has increased in recent years, owing to higher numbers of individuals at risk for this infection. Although amphotericin B, posaconazole and isavuconazole are generally effective against Trichosporon species, some isolates may have variable susceptibility to these antifungals. OBJECTIVES: Herein, we evaluated the species distribution, genetic diversity and antifungal susceptibility profiles of Trichosporon isolates in Iran. METHODS: The yeasts were identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Phylogenetic analysis was performed based on amplified fragment length polymorphism (AFLP). The in vitro susceptibilities of eight antifungal agents were analysed using the Clinical and Laboratory Standards Institute broth microdilution methods. RESULTS: The isolates belonged to the species T asahii (n = 20), T japonicum (n = 4) and T faecale (n = 3). A dendrogram of the AFLP analysis demonstrated that T asahii and non-asahii Trichosporon strains (T japonicum and T faecale) are phylogenetically distinct. While voriconazole was the most active agent (GM MIC = 0.075 µg/ml), high fluconazole MICs (8 µg/ml) were observed for a quarter of Trichosporon isolates. The GM MIC value of amphotericin B for T asahii and non-asahii Trichosporon species was 0.9 µg/ml. CONCLUSIONS: The distribution and antifungal susceptibility patterns of the identified Trichosporon species could inform therapeutic choices for treating these emerging life-threatening fungi.

Specific microRNA/mRNA expression profiles and novel immune regulation mechanisms are induced in THP-1 macrophages by in vitro exposure to Trichosporon asahii.

BACKGROUND: Trichosporon asahii is considered the most prominent species associated with invasive trichosporonosis, but little is known about the pathogenesis of T. asahii infection in the host. MicroRNAs (miRNAs) are a class of noncoding endogenous small RNAs that play vital roles by manipulating immune responses against pathogenic microorganisms. Nevertheless, the exact functions of miRNAs in T. asahii infection are still unknown. OBJECTIVE: To investigate the interactions involved in the miRNA immune response in THP-1 macrophages following in vitro exposure to T. asahii. METHODS: We utilized next-generation sequencing to detect differentially expressed (DE) miRNAs and mRNAs in THP-1 cells after 24 h of in vitro exposure to T. asahii. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to verify the sequencing results. The miRNA-mRNA regulatory network was constructed with the DE miRNAs and DE mRNAs. We performed Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis of the predicted targeting mRNAs in the miRNA-mRNA network. A dual-luciferase reporter assay and enzyme-linked immunosorbent assay (ELISA) were utilized to demonstrate the reliability of the miR-342-3p/Dectin-1 pair. RESULTS: A total of 120 DE miRNAs and 588 DE mRNAs were identified after 24 h of in vitro exposure to T. asahii. The miRNA-mRNA regulatory network was constructed with 39 DE miRNAs and 228 DE mRNAs. KEGG pathway analysis revealed that the up-regulated DE mRNAs in the complex interaction network were mainly involved in immune-related pathways. In addition, we verified the target relationship between miR-342-3p and Dectin-1 and found that miR-342-3p could promote the expression of TNF-α and IL-6 by negatively regulating Dectin-1. CONCLUSIONS: This study evaluated the expression profiles of miRNA/mRNA and revealed the immunological consequences of THP-1 macrophages in response to T. asahii exposure. Moreover, our data suggest that miR-342-3p can indirectly promote inflammatory responses and may be a potential therapeutic target against trichosporonosis.