A unique presentation of subcutaneous Cutaneotrichosporon debeurmannianum infection: A case report of a diagnostic challenge

Introduction

Cutaneotrichosporon debeurmannianum is a yeast-like anamorphic rare fungus commonly found in tropical areas. This case report is the first one located in South America.

Case report

A 67-year-old patient presented with a 5-year history of right foot pain attributed to foot trauma while at sea 5 years prior. During surgical exploration, an impressive whitish cerebriform-like cyst was encountered. Genetic analysis using the genes ITS1, ITS4, LSU-R, and LSU-F was performed, and a phylogenetic tree identified C. debeurmannianum.

Conclusion

A complete characterization of this fungus which causes human disease has not yet been achieved and more research is needed.

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.

Intergenic spacer (IGS-1) region sequence-based identification, genotypic analysis, and antifungal susceptibility of clinical Trichosporon species

OBJECTIVES

Molecular genotyping of Trichosporon species using intergenic spacer region (IGS-1) sequencing and antifungal drug susceptibility testing of T. asahii clinical isolates from Indian patients.

MATERIALS AND METHODS

Fifty-five Trichosporon strains were characterized using IGS-1 sequencing from 2006 to 2018 and tested against 5 antifungals using CLSI M27-A3 guidelines.

RESULTS

In this study, broad-spectrum antibiotics with steroids, catheters, and ICU stays were major underlying risk factors. These cases were most commonly associated with diabetes (type-2), chronic obstructive pulmonary disease, and hypertension. Out of fifty-five isolates, 47 (85%) were identified as T. asahii, and the remaining 6 were T. inkin (11%) and 2 were Cutaneotrichosporon dermatis (3.6%). The most common genotype of T. asahii was G3 (22; 49%) subsequently G4 (12; 23%), G1 (8; 17%), and G7 (2; 4%). One new genotype of T asahii was found in addition to the fifteen already known genotypes. Indian T. asahii isolates showed a low level of amphotericin B (range 0.06-4 ​mg/l) resistance but relatively higher in fluconazole (range 0.25-64 ​mg/l). Although, comparatively low MIC ranges were found in the case of voriconazole (0.03-1 ​mg/l), posaconazole (0.06-1 ​mg/l) and itraconazole (0.06-1 ​mg/l). Voriconazole appeared to be the most active drug in T. asahii isolates. The MICs for all the drugs were comparatively lower in the case of non-Trichosporon asahii strains.

CONCLUSION

T. asahii was the most common Trichosporon isolate. Speciation is necessary for optimal antifungal therapy. Voriconazole-based treatment, Steroids, removal of catheters and control of underlying conditions results in positive outcomes.

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.

Faster and accurate identification of clinically important Trichosporon using MALDI TOF MS

PURPOSE

Trichosporon species are emerging human pathogens, accounting for the second most common cause of non-candidal mycosis. Rapid and reliable identification of these agents allows a better understanding of their epidemiology and therapeutic management. The Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) technique has the potential to be precise, fast and cost-effective. However, the precision of identification totally depends upon the type of protein extraction method used and embedded database in the system. Our objectives were to standardize the protein extraction technique and expand the present Bruker database by creating an in-house database and validating it with diverse clinical Trichosporon species of Indian origin.

METHODS

Two different protein extraction protocols (on-plate and off-plate) were evaluated. The off-plate protocol was finalized for the identification. MALDI TOF MS with the existing Bruker database was evaluated for its ability to identify a total of 79 intergenic spacer 1 (IGS1) gene sequence confirmed clinical isolates of 5 different Trichosporon species.

RESULTS

As outcome, off plate protocol yielded higher accuracy (73% on the species level and 95% on the genus level) than on-plate (25% on the genus level) in terms of log scores. The existing database for Trichosporon species was enriched with 28 sequence confirmed isolates, which improved accuracy from 73% to 100% and were identified up to species level with a log score >2.3.

CONCLUSIONS

Used with standardized protein-extraction protocol along with an expanded database, MALDI-TOF MS could be a rapid and reliable approach to identify clinical Trichosporon species routinely in the laboratory.

Strain Typing of Trichosporon asahii Clinical Isolates by Random Amplification of Polymorphic DNA (RAPD) Analysis

Objective The aim of this study was to identify and isolate Trichosporon asahii ( T. asahii ) from clinical samples and to assess the genetic relatedness of the most frequently isolated strains of T. asahii using random amplification of polymorphic DNA (RAPD) primers GAC-1 and M13.

Methods All the clinical samples that grew Trichosporon species, identified and confirmed by polymerase chain reaction (PCR) using Trichosporon genus-specific primers, were considered for the study. Confirmation of the species T. asahii was carried out by T. asahii- specific PCR. Fingerprinting of the most frequently isolated T. asahii isolates was carried out by RAPD using random primers GAC-1 and M13.

Results Among the 72 clinical isolates of Trichosporon sp. confirmed by Trichosporon -specific PCR, 65 were found to be T. asahii as identified by T. asahii- specific PCR. Fingerprinting of the 65 isolates confirmed as T. asahii using GAC-1 RAPD primer yielded 11 different patterns, whereas that of M13 primer produced only 5 patterns. The pattern I was found to be the most predominant type (29.2%) followed by pattern III (16.9%) by GAC-1 primer.

Conclusions This study being the first of its kind in India on strain typing of T. asahii isolates by adopting RAPD analysis throws light on genetic diversity among the T. asahii isolates from clinical samples. Fingerprinting by RAPD primer GAC-1 identified more heterogeneity among the T. asahii isolates than M13.

Epidemiological profile and antifungal susceptibility pattern of Trichosporon species in a tertiary care hospital in Chandigarh, India

Background and Purpose

Trichosporon species are ubiquitous in nature which are associated with fatal opportunistic invasive infections, especially in immunocompromised patients. The present study aimed to evaluate the epidemiological and clinical details, as well as the antifungal susceptibility pattern of the patients with Trichosporon infections.

Materials and Methods

In total, 50 clinical isolates of Trichosporon species from various samples were included in this study. The samples were isolated over a period of 18 months from patients in a tertiary hospital in North India. The isolates were characterised phenotypically with Vitek MS (bioMérieux, France). Trichosporon spp. were isolated from urine (30%), nail (30%), tissue (16%), pleural fluid (14%), and sputum (5%). In total, majority of the isolates were of Trichosporon asahii (92%), followed by Trichosporon mucoides (6%), and Trichosporon ovoides (2%). It is noteworthy that most of the reported cases were from intensive care unit (34%).

Results

Intravenous catheters, antibiotics, and antifungal uptake were significantly associated risk factors with Trichosporon infection. All invasive isolates were observed to be resistant in vitro to caspofungin and exhibited high minimum inhibitory concentration (MIC) values against amphotericin B, fluconazole, and 5-flucytosine. The MICs for voriconazole and posaconazole were low.

Conclusion

Trichosporonosis is being increasingly reported all around the world, including India. The results of this study highlighted the importance of early detection and treatment for this emerging yeast and also added to the ongoing surveillance for the antifungal susuceptibility pattern for this fungus.

A Comprehensive Review of Trichosporon spp.: An Invasive and Emerging Fungus

Trichosporon species are basidiomycetous yeast-like organisms found ubiquitous in nature. They are increasingly been recognized as opportunistic pathogens capable of causing life-threatening invasive diseases (trichosporonosis), especially in immuno-suppressed patients and rarely in immuno-competent patients too. Earlier multiple members of the genus Trichosporon were clubbed together as T. beigelli but after the advent of molecular techniques, more than 50 different subspecies and around 16 different strains causing human diseases are reported. It is known to cause a wide range of diseases, from superficial to probable and proven invasive diseases to summer hypersensitivity. The ability of Trichosporon strains to form biofilms on implanted devices, glucuronoxylomannan in their cell walls, and production of proteases and lipases lead to the virulence of this genus. This ubiquitous fungus exhibits intrinsic resistance to echinocandins, variable minimum inhibitory concentrations (MIC) for amphotericin B, and moderate susceptibility to fluconazole and Itraconazole, which are the commonly used anti-fungal agents for any invasive fungal infections which lead to the re-emergence of this notorious yet neglected pathogen and hence the reports of breakthrough infections among patients receiving these antifungals. This review is to understand the epidemiological, clinical details, and antifungal susceptibility pattern of various Trichosporon infections and it highlights the importance of early detection and treatment for this emerging yeast and also will add to the ongoing surveillance for the anti-fungal susceptibility pattern for this fungus.

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.

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.

Implication of efflux pumps and ERG11 genes in resistance of clinical Trichosporon asahii isolates to fluconazole

Introduction. Trichosporon asahii has been recognized as an opportunistic agent having a limited sensitivity to antifungal treatment.Hypothesis/Gap Statement. Molecular mechanisms of azole resistance have been rarely reported for Trichosproron asahii. Similar to other fungi, we hypothesized that both ERG11 gene mutation and efflux pumps genes hyper-expression were implicated.Aim. The current work aimed to study the sensitivity of clinical T. asahii isolates to different antifungal agents and to explore their resistance mechanisms by molecular methods including real-time PCR and gene sequencing.Methods. The sensitivity of T. asahii isolates to fluconazole, amphotericin B and voriconazole was estimated by the Etest method. Real-time PCR was used to measure the relative expression of Pdr11, Mdr and ERG11 genes via the ACT1 housekeeping gene. Three pairs of primers were also chosen to sequence the ERG11 gene. This exploration was followed by statistical study including the receiver operating characteristic (ROC) curve analysis to identify a relationship between gene mean expression and the sensitivity of isolates.Results. In 31 clinical isolates, the resistance frequencies were 87, 16.1 and 3.2 %, respectively, for amphotericin B, fluconazole and voriconazole. Quantitative real-time PCR demonstrated that only Mdr over-expression was significantly associated with FCZ resistance confirmed by univariate statistical study and the ROC curve analysis (P <0.05). The ERG11 sequencing revealed two mutations H380G and S381A in TN325U11 (MIC FCZ=8 µg ml^-1) and H437R in TN114U09 (MIC FCZ=256 µg ml^-1) in highly conserved regions (close to the haem-binding domain) but their involvement in the resistance mechanism has not yet been assigned.Conclusion. T. asahii FCZ resistance mechanisms are proven to be much more complex and gene alteration sequence and/or expression can be involved. Only Mdr gene over-expression was significantly associated with FCZ resistance and no good correlation was observed between FCZ and VCZ MIC values and relative gene expression. ERG11 sequence alteration seems to play a major role in T. asahii FCZ resistance mechanism but their involvement needs further confirmation.

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.

Physiological characterization and molecular identification of some rare yeast species causing onychomycosis

INTRODUCTION

Onychomycosis are infections with a variety of etiological agents. Although dermatophytes are responsible for most infections, yeasts are gaining importance as agents of these pathologies. The use of antifungals has increased the incidence of what had been considered rare or novel pathogens. We reidentify three rare yeasts from a culture collection of onychomycosis agents by matrix-assisted laser desorption/ionization time of flight/mass spectrometry (MALDI-TOF/MS) and sequencing the internal transcribed spacer (ITS) regions or the intergenic spacer (IGS) 1 region of ribosomal DNA (rDNA), and present their enzymatic and antifungal susceptibility profiles.

MATERIAL AND METHODS

We performed a phenotypical characterization and molecular identification of five yeast isolates. We tested the urease, gelatinase, DNase, phospholipase, protease, and esterase activities, as well as the hemolytic activity. We evaluated the antifungal susceptibility to amphotericin B, fluconazole, anidulafungin and caspofungin.

RESULTS

Phenotypic methods could not identify the isolates. MALDI-TOF/MS was able to properly identify Candida duobushameulonii. The five isolates were successfully identified by sequence analysis as Candida duobushaemulonii, Meyerozyma caribbica and Cutaneotrichosporon dermatis. Candida duobushameulonii showed hemolytic, phospholipase, and protease activities. Meyerozyma caribbica was positive for gelatinase and protease activities. All antifungals exhibited minimum inhibitory concentrations (MICs) ≤2μg/mL against both species. The three isolates of Cutaneotrichosporon dermatis showed urease, DNase, and esterase activities, and resistance to echinocandins (MICs ≥8μg/mL), while amphotericin B and fluconazole exhibited low MICs against these isolates (0.50-2μg/mL).

DISCUSSION

Sequencing of the ITS or IGS1 regions of rDNA remains the best method for identifying cryptic species over other commercially available systems. More reports are needed to define the enzymatic and antifungal profiles for these species. This is the first report of Meyerozyma caribbica and Cutaneotrichosporon dermatis as etiological agents of onychomycosis.

The epidemiology, genotypes, antifungal susceptibility of Trichosporon species, and the impact of voriconazole on Trichosporon fungemia patients

BACKGROUND/PURPOSE

Invasive Trichosporon infections are emerging, but association of different therapeutic management of Trichosporon fungemia and clinical outcomes were rarely reported. This study investigates the epidemiology, species distribution and genotypes of trichosporonosis in Taiwan, and identified the predictors of clinical outcomes in patients with Trichosporon fungemia.

METHODS

Strains collected from four medical centers in Taiwan, during 2010-2018. Species identification was confirmed by sequencing of IGS1 region, and antifungal susceptibility was performed using Sensititre YeastOne panel.

RESULTS

Among 115 isolates, Trichosporon asahii was the leading species (73.0%), followed by Trichosporon dermatis (11.3%), Trichosporon faecales (6.1%), and Trichosporon montevideense (5.2%). Of the 84 T. asahii isolates, genotype 1 was the predominant (41.7%). High fluconazole minimal inhibitory concentration (MICs,≧8 μg/mL) were observed for 70.2% T. asahii isolates and 16.1% non-asahii Trichosporon isolates. Posaconazole and voriconazole possess the most potent antifungal activity against all Trichosporon isolates, with geometric mean values of 0.251 μg/mL and 0.111 μg/mL, respectively. Fifty-three isolates collected from blood cultures, and 42 patients with fungemia enrolled for the Kaplan-Meier plot which revealed that voriconazole treatment had a significantly better survival rate compared with those without (p = 0.042). In multivariate analysis, source control (odds ratio [OR]: 0.13 95%CI [confidence interval]: 0.02-0.83, p = 0.031) and voriconazole use (OR: 0.11 95%CI: 0.02-0.74, p = 0.023) are independent predictors of 14-day mortality.

CONCLUSION

This is the largest series of Trichosporon fungemia up till the present moment. Voriconazole therapy and source control play important roles in 14-day mortality.

Epidemiology and Antifungal Susceptibility of Infections Caused by Trichosporon Species: An Emerging Non-Candida and Non-Cryptococcus Yeast Worldwide

Introduction

Over the past four decades, there has been an increase in the number of fatal opportunistic invasive trichosporonosis cases especially in immunocompromised hosts.

Objective

The objective of the study is to evaluate the epidemiological, clinical details and antifungal susceptibility pattern of the patients with Trichosporon infections.

Materials and Methods

Twenty-four clinical isolates of Trichosporon species isolated from blood, samples, pleural fluid and nail were included in this study, over a period of 12 years (2005-2016) in a tertiary hospital in North India. The isolates were characterised phenotypically and few representative isolates were sequenced also. The minimum inhibitory concentration (MIC) was determined as per Clinical and Laboratory Standards Institute, 2012.

Results

Trichosporon spp. from blood culture (57.78%), nail (37.5%) and pleural fluid (4.17%). On phenotypic tests, 79.16% of the isolates were Trichosporon asahii, followed by Trichosporon dermatis (8.33%), Trichosporon japonicum (4.17%), Trichosporon ovoides (4.17%) and Trichosporon mucoides (4.17%). The MIC range of Trichosporon species from invasive infections were fluconazole (0.06-256 μg/ml), amphotericin B (0.125-16 μg/ml), voriconazole (0.0616-8 μg/ml), posaconazole (0.0616-32 μg/ml) and caspofungin (8-32 μg/ml). The isolates from superficial infection were resistant to fluconazole (0.06-256 μg/ml) and itraconazole (0.125-32 μg/ml), all were susceptible to ketoconazole and while only two were resistant to voriconazole (0.25-4 μg/ml).

Conclusion

T. asahii was the most common isolate. Disseminated trichosporonosis is being increasingly reported worldwide including India and represents a challenge for both diagnosis and species identification. Prognosis is limited, and antifungal regimens containing triazoles appear to be the best therapeutic approach. In addition, accurate identification, removal of central venous lines and voriconazole-based treatment along with control of underlying conditions were associated with favourable outcomes.

Exploring the resistance mechanisms in Trichosporon asahii: Triazoles as the last defense for invasive trichosporonosis

Trichosporon asahii has recently been recognized as an emergent fungal pathogen able to cause invasive infections in neutropenic cancer patients as well as in critically ill patients submitted to invasive medical procedures and broad-spectrum antibiotic therapy. T. asahii is the main pathogen associated with invasive trichosporonosis worldwide. Treatment of patients with invasive trichosporonosis remains a controversial issue, but triazoles are mentioned by most authors as the best first-line antifungal therapy. There is mounting evidence supporting the claim that fluconazole (FLC) resistance in T. asahii is emerging worldwide. Since 2000, 15 publications involving large collections of T. asahii isolates described non-wild type isolates for FLC and/or voriconazole. However, very few papers have addressed the epidemiology and molecular mechanism of antifungal resistance in Trichosporon spp. Data available suggest that continuous exposure to azoles can induce mutations in the ERG11 gene, resulting in resistance to this class of antifungal drugs. A recent report characterizing T. asahii azole-resistant strains found several genes differentially expressed and highly mutated, including genes related to the Target of Rapamycin (TOR) pathway, indicating that evolutionary modifications on this pathway induced by FLC stress may be involved in developing azole resistance. Finally, we provided new data suggesting that hyperactive efflux pumps may play a role as drug transporters in FLC resistant T. asahii strains.

Invasive Infections Due to Trichosporon: Species Distribution, Genotyping, and Antifungal Susceptibilities from a Multicenter Study in China

A total of 133 clinical Trichosporon isolates were collected in the National China Hospital Invasive Fungal Surveillance Net (CHIF-NET) program in 2009 to 2016. Accurate identification was performed by sequencing of the intergenic spacer 1 (IGS1) region. Among these isolates, Trichosporon asahii (108 isolates [81.2%]) was the leading species, followed by Trichosporon dermatis (7 isolates [5.3%]), Trichosporon asteroides (5 isolates [3.8%]), Trichosporon inkin (5 isolates [3.8%]), Trichosporon dohaense (3 isolates [2.3%]), and 1 isolate (0.7%) each of Trichosporon faecale, Trichosporon jirovecii, Trichosporon mucoides, Trichosporon coremiiforme, and Trichosporon montevideense Both the Vitek mass spectrometry (MS) (bioMérieux, Marcy l'Etoile, France) and Bruker Biotyper MS (Bruker Daltonics GmbH, Germany) platforms gave high levels (>97.5%) of correct identification when the species were present in the database. The geometric mean (GM) of amphotericin B MICs for T. asahii was 2-fold higher than that for non-asahii Trichosporon High fluconazole MICs (≥8 μg/ml) were observed for 25% of T. asahii isolates (27/108 isolates) and 16% of non-asahii Trichosporon (4/25 isolates) isolates. Itraconazole MICs were ≤0.5 μg/ml for 89.5% of the isolates. Voriconazole was the most potent antifungal agent in vitro, with a GM of 0.09 μg/ml. Genotyping of the isolates using IGS1 sequence alignment revealed that genotype 1 was most common (41.7%), followed by genotype 4 (31.5%), genotype 3 (23.1%), genotype 5 (0.9%), genotype 6 (0.9%), and genotype 7 (1.8%). Our data on species distribution, genotypes, and antifungal susceptibilities may contribute to a better understanding of the epidemiology of invasive Trichosporon infections throughout China.

Epidemiology of antifungal susceptibility: Review of literature

Fungal infections are a major cause of morbidity and mortality despite the latest developments of diagnostic tools and therapeutic options. Early initiation of the appropriate antifungal therapy has been demonstrated to have a direct impact on the patient's outcome. Antifungal susceptibility testing methods are available to detect antifungal resistance and to determine the best treatment for a specific fungus. American and European standards have been developed, as well as equivalent commercial systems, which are more appropriate for clinical laboratories. These studies have allowed the development of interpretative breakpoints against the most frequent agents of fungal infections in the world. Surveillance of antifungal susceptibility patterns can provide the local drug resistance data to the clinicians, which can further aid better management of patients. Antifungal susceptibility tests have become essential tools to identify resistance to antifungals, to know the local and global disease epidemiology and to guide the treatment of fungal diseases. The distribution of species and the prevalence of antifungal resistance in fungi isolates varied among different areas. Here we summarize the epidemiology of antifungal susceptibility pattern of different fungal species.

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

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 CBS10761^T. 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.

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.

Rare fungal infectious agents: a lurking enemy

In the expanding population of immunocompromised patients and those treated in intensive care units, rare fungal infectious agents have emerged as important pathogens, causing invasive infections associated with high morbidity and mortality. These infections may present either as de novo or as breakthrough invasive infections in high-risk patients with hematologic malignancies receiving prophylactic or empirical antifungal therapy or in patients with central venous catheters. Diagnosis and treatment are challenging. Physicians should have a high index of suspicion because early diagnosis is of paramount importance. Conventional diagnostic methods such as cultures and histopathology are still essential, but rapid and more specific molecular techniques for both detection and identification of the infecting pathogens are being developed and hopefully will lead to early targeted treatment. The management of invasive fungal infections is multimodal. Reversal of risk factors, if feasible, should be attempted. Surgical debridement is recommended in localized mold infections. The efficacy of various antifungal drugs is not uniform. Amphotericin B is active against most yeasts, except Trichosporon, as well as against Mucorales, Fusarium, and some species of Paecilomyces and dimorphic fungi. The use of voriconazole is suggested for the treatment of trichosporonosis and scedosporiosis. Combination treatment, though recommended as salvage therapy in some infections, is controversial in most cases. Despite the use of available antifungals, mortality remains high. The optimization of molecular-based techniques, with expansion of reference libraries and the possibility for direct detection of resistance mechanisms, is awaited with great interest in the near future. Further research is necessary, however, in order to find the best ways to confront and destroy these lurking enemies.