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

Adhesion and biofilm formation by two clinical isolates of Trichosporon Cutaneum in various environmental conditions

Trichosporon spp. is an emerging opportunistic pathogen and a common cause of both superficial and invasive infections. Although Trichosporon asahii is the most frequently isolated species, Trichosporon cutaneum is also widely observed, as it is the predominant agent in cases of white Piedra and onychomycosis. Trichosporon spp. is a known to produce biofilms, which serve as one of its virulence mechanisms, however, there is limited data available on biofilms formed by T. cutaneum. Thus, the aim of this study was to assess the adhesion and biofilm formation of two clinical isolates of T. cutaneum under various environmental conditions (including temperature, nutrient availability, and carbon source), as well as their tolerance to fluconazole. Adhesion was tested on common abiotic substrates (such as silicone, glass, and stainless steel), revealing that T. cutaneum readily adhered to all surfaces tested. CV staining was applied for the evaluation of the environment influence on biofilm efficiency and it was proved that the nutrient availability has a major impact. Additionaly, fluorescent staining was employed to visualize the morphology of T. cutaneum biofilm and its survival in the presence of fluconazole. Hyphae production was shown to play a role in elevated biofilm production in minimal medium and increased tolerance to fluconazole.

Genome-Wide Identification and Characterization of the Medium-Chain Dehydrogenase/Reductase Superfamily of Trichosporon asahii and Its Involvement in the Regulation of Fluconazole Resistance

The medium-chain dehydrogenase/reductase (MDR) superfamily contains many members that are widely present in organisms and play important roles in growth, metabolism, and stress resistance but have not been studied in Trichosporon asahii. In this study, bioinformatics and RNA sequencing methods were used to analyze the MDR superfamily of T. asahii and its regulatory effect on fluconazole resistance. A phylogenetic tree was constructed using Saccharomyces cerevisiae, Candida albicans, Cryptococcus neoformans, and T. asahii, and 73 MDRs were identified, all of which contained NADPH-binding motifs. T. asahii contained 20 MDRs that were unevenly distributed across six chromosomes. T. asahii MDRs (TaMDRs) had similar 3D structures but varied greatly in their genetic evolution at different phylum levels. RNA-seq and gene expression analyses revealed that the fluconazole-resistant T. asahii strain upregulates xylitol dehydrogenase, and downregulated alcohol dehydrogenase and sorbitol dehydrogenase concluded that the fluconazole-resistant T. asahii strain was less selective toward carbon sources and had higher adaptability to the environment. Overall, our study contributes to our understanding of TaMDRs, providing a basis for further analysis of the genes associated with drug resistance in T. asahii.

Mycotic aneurysms due to Trichosporon asahii in a patient with ulcerative colitis under immunosuppression

Yeast fungi of the genus Trichosporon spp. can colonize the gastrointestinal tract in humans. In recent decades, the pathogenic role of Trichosporon asahii has been increasingly acknowledged especially in the setting of neutropenic patients with hematological malignancies. However, non-neutropenic patients who are immunosuppressed for other reasons are also at risk of developing invasive forms of this mycosis. We present the case of a 62-year-old male, with a history of ulcerative colitis under immunosuppressive treatment and previous exposure to antibiotics for various bacterial infections, who was admitted to the emergency department with a mycotic aneurysm of the abdominal aorta and left common iliac secondary to T. asahii infection. A multidisciplinary approach of the case (both early medical and surgical interventions) allowed the patient's favorable outcome. The patient was followed for more than two years with no evidence of relapse. We postulate that the diagnosis of invasive Trichosporonosis should be considered in patients with inflammatory bowel disease (IBD) under immunosuppressive treatment and with prior exposure to antibiotics.

In vitro activity of isavuconazole against clinically relevant Trichosporon species: a comparative evaluation of EUCAST broth microdilution and MIC Test Strip methods

OBJECTIVES

To evaluate the in vitro activity of isavuconazole on 154 clinical and reference strains of Trichosporon asahii, Trichosporon asteroides, Trichosporon coremiiforme, Trichosporon faecale and Trichosporon inkin by using the EUCAST broth microdilution method (BMD) and Liofilchem MIC Test Strips (MTS).

METHODS

Antifungal susceptibility testing for isavuconazole, fluconazole, voriconazole and posaconazole was assessed by EUCAST E.DEF 7.3.2. MIC values of isavuconazole obtained by BMD after 48 h of incubation were compared with MTS MICs after 24 and 48 h of incubation.

RESULTS

T. asahii and T. asteroides showed the highest isavuconazole MIC90 values (0.5 mg/L). In clinical isolates, T. asahii exhibited the highest MIC90 values (0.5 mg/L) compared with non-T. asahii (0.06-0.25 mg/L). The five non-WT T. asahii isolates for fluconazole, voriconazole and posaconazole also exhibited high MICs of isavuconazole (≥0.5 mg/L). A better correlation between MTS and BMD MICs was observed after 24 h incubation for all species tested. MTS measurements performed at 48 h increased by at least 122% the number of isolates with >2 dilutions compared with the standard method.

CONCLUSIONS

Isavuconazole exhibited variable in vitro activity among the Trichosporon species tested, showing higher or equal MICs than the other azoles. The five non-WT T. asahii clinical isolates tested also exhibited high isavuconazole MICs, suggesting the occurrence of triazole cross-resistance. Our MTS data indicate that there is no advantage in extended reading time for MTS from 24 to 48 h for Trichosporon yeasts.

Promethazine inhibits efflux, enhances antifungal susceptibility and disrupts biofilm structure and functioning in Trichosporon

Trichosporon spp. are emerging opportunistic fungi associated with invasive infections, especially in patients with haematological malignancies. The present study investigated the in vitro inhibition of efflux pumps by promethazine (PMZ) as a strategy to control T. asahii and T. inkin. Planktonic cells were evaluated for antifungal susceptibility to PMZ, as well as inhibition of efflux. The effect of PMZ was also studied in Trichosporon biofilms. PMZ inhibited T. asahii and T. inkin planktonic cells at concentrations ranging from 32 to 256 μg ml^-1. Subinhibitory concentrations of PMZ inhibited efflux activity in Trichosporon. Biofilms were completely eradicated by PMZ. PMZ potentiated the action of antifungals, affected the morphology, changed the amount of carbohydrates and proteins and reduced the amount of persister cells inside biofilms. The results showed indirect evidences of the occurrence of efflux pumps in Trichosporon and opens a perspective for the use of this target in the control of trichosporonosis.

ERG11 Analysis among Clinical Isolates of Trichosporon asahii with Different Azole Susceptibility Profiles

We analyzed a cohort of Trichosporon asahii strains with different MICs of fluconazole and voriconazole and evaluated the presence of ERG11 mutations. ERG11 mutation conferring an amino acid change was found and its resistance potential was evaluated by cloning into Saccharomyces cerevisiae susceptible host strain. Transformants were not resistant to either fluconazole nor voriconazole. Our results suggest that ERG11 variants exist among T. asahii isolates, but are not responsible for resistance phenotypes.

Hospital Trichosporon asahii isolates with simple architecture biofilms and high resistance to antifungals routinely used in clinical practice

Infections by Trichosporon spp. are increasing worldwide and its treatment remains a challenge. Colonization of medical devices has been considered as a predisposing factor for trichosporonosis, which is related to fungal biofilm production. Thus, this study aimed to evaluate the ability of six hospital T. asahii isolates to form biofilm on abiotic surface, as well as to investigate the impact of three classic antifungals on both planktonic and biofilm forms. The fungal identification was based on macro and micromorphological characteristics, biochemical tests and confirmation by mass spectrometry assisted by the flight time desorption/ionization matrix (MALDI-TOF MS). Antifungal susceptibility assay of planktonic cells showed inhibitory and fungicidal concentrations ranging from 2.5 to 10 µg/mL for voriconazole, 2 to 8 µg/mL for fluconazole, and 1 to 4 µg/mL for amphotericin B. All T. asahii strains were able to form biofilms on the polystyrene microplates surface within 24 h, showing a simple architecture when compared with Candida spp. biofilm. On the other hand, the same antifungals did not show action in neither the inhibition of biofilm formation nor on the formed biofilm. Concluding, the present study reinforced the relevance of the MALDI-TOF MS methodology for a safe identification of T. asahii. Classic antifungals were active on the planktonic form, but not on the biofilms. All isolates formed biofilms on the polystyrene microplates and showed a simple architecture.

JMM Profile: Trichosporon yeasts: from superficial pathogen to threat for haematological-neutropenic patients

Trichosporon yeasts are classical agents of superficial mycoses, and they are ranked as the first to second predominant basidiomycetous yeast able to cause invasive infections. The clinical presentation of Trichosporon infections varies with the affected anatomical site, with fungaemia present in the majority of invasive trichosporonosis cases. Only a limited number of antifungal compounds can be used to treat Trichosporon infections. Azoles are the first choice due to their intrinsic resistance to echinocandins. Better laboratory methods and up-to-date databases of commercial platforms are required to improve identification, susceptibility testing and surveillance of this potentially threating infection.

Molecular identification, antifungal susceptibility, and resistance mechanisms of pathogenic yeasts from the China antifungal resistance surveillance trial (CARST-fungi) study

To have a comprehensive understanding of epidemiology and antifungal susceptibilities in pathogenic yeasts, the China Antifungal Resistance Surveillance Trial (CARST-fungi) study was conducted. All yeast isolates were identified by ribosomal DNA sequencing. Antifungal susceptibilities were performed using CLSI M27-A4 broth microdilution method. Sequence and expression level of resistant-related genes in resistant/non-wide-type (NWT) Candida isolates were analyzed. Totally 269 nonduplicate yeast isolates from 261 patients were collected. About half of the yeast isolates (127, 47.2%) were recovered from blood, followed by ascetic fluid (46, 17.1%). C. albicans remained the most prevalent (120, 44.6%), followed by C. parapsilosis complex (50, 18.6%), C. tropicalis (40, 14.9%), and C. glabrata (36, 13.4%). Fourteen (11.7%) C. albicans isolates and 1 (2.0%) C. parapsilosis isolate were resistant/NWT to triazoles. Only 42.5% (17/40) C. tropicalis were susceptible/WT to all the triazoles, with 19 (47.5%) isolates NWT to posaconazole and 8 (20%) cross-resistant to triazoles. Among C. glabrata, 20 (55.6%) and 8 (22.2%) isolates were resistant/NWT to voriconazole and posaconazole, respectively, and 4 (10.3%) isolates were cross-resistant to triazoles. Isavuconazole was the most active triazole against common Candida isolates. Except for 2 isolates of C. glabrata cross-resistant to echinocandins which were also NWT to POS and defined as multidrug-resistant, echinocandins exhibit good activity against common Candida species. All isolates were WT to AMB. For less common species, Rhodotorula mucilaginosa exhibited high MICs to echinocandins and FLC, and 1 isolate of Trichosporon asahii showed high MICs to all the antifungals except AMB. Among triazole-resistant Candida isolates, ERG11 mutations were detected in 10/14 C. albicans and 6/23 C. tropicalis, while 21/23 C. tropicalis showed MDR1 overexpression. Overexpression of CDR1, CDR2, and SNQ2 exhibited in 14, 13, and 8 of 25 triazole-resistant C. glabrata isolates, with 5 isolates harboring PDR1 mutations and 2 echinocandins-resistant isolates harboring S663P mutation in FKS2. Overall, the CARST-fungi study demonstrated that although C. albicans remain the most predominant species, non-C. albicans species accounted for a high proportion. Triazole-resistance is notable among C. tropicalis and C. glabrata. Multidrug-resistant isolates of C. glabrata and less common yeast have been emerging.

Comparative Biophysical and Ultrastructural Analysis of Melanins Produced by Clinical Strains of Different Species From the Trichosporonaceae Family

Melanin is one of the most studied virulence factors in pathogenic fungi. This pigment protects them from a series of both environmental and host stressors. Among basidiomycetes, Cryptococcus neoformans and Trichosporon asahii are known to produce melanin in the presence of phenolic precursors. Other species from the Trichosporonaceae family also produce this pigment, but the extent to this production among the clinically relevant species is unknown. For this reason, the aim of this study was to verify the production of melanin by different Trichosporonaceae species of clinical interest and to compare their pigments with the ones from C. neoformans and T. asahii, which are more prevalent in human infections. Melanin was produced in a minimal medium supplemented with 1 mM L-dihydroxyphenylalanine (L-DOPA). Pigment was evaluated using scanning electron microscopy, Zeta potential measurements, and energy-dispersive X-ray spectroscopy. It was found that, besides C. neoformans and T. asahii, Trichosporon japonicum, Apiotrichum montevideense, Trichosporon inkin, Trichosporon faecale, Cutaneotrichosporon debeurmannianum, and Cutaneotrichosporon arboriformis also produce melanin-like particles in the presence of L-DOPA. Melanin particles have negative charge and are smaller than original cells. Variations in color, fluorescence, and chemical composition was noticed between the studied strains. All melanins presented carbon, oxygen, sodium, and potassium in their composition. Melanins from the most pathogenic species also presented iron, zinc, and copper, which are important during parasitism. Biophysical properties of these melanins can confer to the Trichosporonaceae adaptive advantages to both parasitic and environmental conditions of fungal growth.

An emerging chemical fumigant: two-sided effects of dazomet on soil microbial environment and plant response

Methyl bromide has been banned worldwide because it causes damage to the ozone layer and the environment. To find a substitute for methyl bromide, the relationships among fumigation, plant growth, and the microbial community in replant soil require further study. We performed pot and field experiments to investigate the effects of dazomet fumigation on soil properties and plant performance. Changes in soil microbial community structure and diversity were assessed using high-throughput sequencing, and plant physiological performance and soil physicochemical properties were also measured. Dazomet fumigation enhanced photosynthesis and promoted plant growth in replant soil; it altered soil physical and chemical properties and reduced soil enzyme activities, although these parameters gradually recovered over time. After dazomet fumigation, the dominant soil phyla changed, microbial diversity decreased significantly, the relative abundance of biocontrol bacteria such as Mortierella increased, and the relative abundance of pathogenic bacteria such as Fusarium decreased. Over the course of the experiment, the soil microbial flora changed dynamically, and soil enzyme activities and other physical and chemical properties also recovered to a certain extent. This result suggested that the effect of dazomet on soil microorganisms was temporary. However, fumigation also led to an increase in some resistant pathogens, such as Trichosporon, that affect soil function and health. Therefore, it is necessary to consider potential negative impacts of dazomet on the soil environment and to perform active environmental risk management in China.

Trichosporon asahii Urinary Tract Infection in a Patient with Severe COVID-19

Trichosporon asahii is a yeast-like basidiomycete that is an emerging opportunistic infection in immunocompromised patients. Urinary tract infections due to T. asahii are rarely reported in the literature and typically seen only in immunocompromised patients. In addition to being immunocompromised, critically ill COVID-19 patients often have prolonged exposure to antibiotics, corticosteroids, and Foley catheters, which further increases their susceptibility to infection with T. asahii. There are limited case reports documenting successful treatment of T. asahii among hospitalized patients, particularly among COVID-19 patients, in the literature. Therefore, it is important that successful treatment regimens be reported. Here, we report a case of T. asahii urinary tract infection successfully treated with fluconazole and voriconazole in a 73-year-old male recovering from COVID-19. Urinary tract infections with T. asahii should be considered in persistently febrile COVID-19 patients with fungal urinary tract infections since prompt recognition and treatment can reduce the risk of disseminated disease and early mortality.

Insight into the antifungals used to address human infection due to Trichosporon spp.: a scoping review

Trichosporonosis infections have been increasing worldwide. Providing adequate treatment for these infections remains a challenge. This scoping review contains information about potential antifungals to treat this pathology. Using online databases, we found 76 articles published between 2010 and 2020 related to this topic. Classic antifungals, molecules and biomolecules, repositioned drugs and natural products have been tested against species of Trichosporon. Experimental research has lacked depth or was limited to in vitro and in vivo tests, so there are no promising new candidates for the clinical treatment of patients with trichosporonosis. Furthermore, most studies did not present appropriate scientific criteria for drug tests, compromising their quality.

Proteomic analysis of serial isolates of Trichosporon asahii identifies host-specific adaptations using the TMT/MRM approach

The opportunistic fungal pathogen Trichosporon asahii (T. asahii) is an important causal agent of mortality in immunocompromised patients and associated with frequent relapses, even with sufficient antifungal treatment. Investigating the proteomes of initial and recurrent isolates may help to identify within-host adaptive changes. In this study, using tandem mass tag (TMT)-labeling combined with liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) technology, we analyzed the proteomes of two T. asahii strains that were isolated 15 years apart from the same patient who suffered initial and recurrent episodes of systemic disseminated trichosporonosis. A total of 597 differentially expressed proteins were identified. Functional analysis showed that the increased proteins were primarily concentrated on peptide/protein/energy/drug metabolism and translation. Most of the results were determined to be consistent with the findings of phenotypic assays, such as tests for drug susceptibility, temperature growth, biofilm formation, melanization and paromomycin assays. Moreover, we performed multiple reaction monitoring (MRM) mass spectrometry to verify 27 candidate proteins, and the results of this experiment were also highly consistent with the results of the TMT analysis. Therefore, to the best of our knowledge, these data provide the first molecular evidence of how the T. asahii proteome changes related to host-specific adaptation during human infection. SIGNIFICANCE: Systemic infection with Trichosporon asahii (T. asahii) has recently been recognized as an important causal agent of mortality in immunocompromised patients. Although triazole treatment usually works efficiently in the early phase of infection, many patients relapse. Hence, comparative analyses of the proteomics of initial and recurrent isolates may reveal evidence of adaptive changes within the host. Our study demonstrates that the recurrent strain has undergone proteomic changes using tandem mass tag (TMT)-labeling combined with liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Moreover, the results of phenotypic assays, including drug susceptibility, temperature growth, biofilm formation, melanization and paromomycin assays, were highly consistent with the proteomic changes, and multiple reaction monitoring (MRM) verification also showed similar trends to the TMT results. In summary, our study is the first to investigate the adaptation of T. asahii under pressure from antifungal chemotherapy and host immune responses.

Species Diversity and Antifungal Susceptibilities of Oral Yeasts from Patients with Head and Neck Cancer

Purpose

To investigate the colonization and susceptibility to antifungal drugs of oral yeasts in head and neck cancer patients in Hainan, China.

Methods

Oral mucosa samples from 211 head and neck cancer patients were collected. Oral yeasts were isolated and identified to species by rDNA ITS sequencing. The susceptibilities of all yeasts to amphotericin B, fluconazole, fluorocytosine, itraconazole, and ketoconazole were determined.

Results

Yeasts were isolated from 124 of the 211 oral swabs. The 124 yeast isolates were classified into following 10 species, from the most frequent to the least frequent, Candida albicans (53.2%), Candida tropicalis (22.6%), Candida krusei (6.5%), Kodamaea ohmeri (5.6%), Candida parapsilosis (4.8%), Hanseniaspora opuntiae (2.4%), Candida metapsilosis (1.6%), Pichia terricola (1.6%), Pichia norvegensis (0.8%), and Trichosporon asahii (0.8%). The overall frequencies of resistance among the yeasts to amphotericin B, fluconazole, flucytosine, itraconazole, and ketoconazole were 4.8%, 8.1%, 16.1%, 9.7%, and 9.7%, respectively. One C. albicans strain and one C. tropicalis strain were tolerant/resistant to all five drugs.

Conclusion

Given the high prevalence of oral yeast colonization in head and neck cancer patients and the observed resistance of certain yeast isolates to the five antifungal drugs, our results suggest that rapid identification and susceptibility testing should be implemented before antifungal treatment is applied among patients with head and neck cancer in Hainan.

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.

Production of Secreted Carbohydrates that Present Immunologic Similarities with the Cryptococcus Glucuronoxylomannan by Members of the Trichosporonaceae Family: A Comparative Study Among Species of Clinical Interest

Glucuronoxylomannan (GXM) participates in several immunoregulatory mechanisms, which makes it an important Cryptococcus virulence factor that is essential for the disease. Trichosporon asahii and Trichosporon mucoides share with Cryptococcus species the ability to produce GXM. To check whether other opportunistic species in the Trichosporonaceae family produce GXM-like polysaccharides, extracts from 28 strains were produced from solid cultures and their carbohydrate content evaluated by the sulfuric acid / phenol method. Moreover, extracts were assessed for cryptococcal GXM cross-reactivity through latex agglutination and lateral flow assay methods. Cryptococcus neoformans and Saccharomyces cerevisiae were used as positive and negative controls, respectively. In addition to T. asahii, the species Trichosporon inkin, Apiotrichum montevideense, Trichosporon japonicum, Trichosporon faecale, Trichosporon ovoides, Cutaneotrichosporon debeurmannianum, and Cutaneotrichosporon arboriformis are also producers of a polysaccharide immunologically similar to the GXM produced by human pathogenic Cryptococcus species. The carbohydrate concentration of the extracts presented a positive correlation with the GXM contents determined by titration of both methodologies. These results add several species to the list of fungal pathogens that produce glycans of the GXM type and bring information about the origin of potential false-positive results on immunological tests for diagnosis of cryptococcosis based on GXM detection.

Trichosporon asahii and Trichosporon inkin Biofilms Produce Antifungal-Tolerant Persister Cells

Persister cells are metabolically inactive dormant cells that lie within microbial biofilms. They are phenotypic variants highly tolerant to antimicrobials and, therefore, associated with recalcitrant infections. In the present study, we investigated if Trichosporon asahii and T. inkin are able to produce persister cells. Trichosporon spp. are ubiquitous fungi, commonly found as commensals of the human skin and gut microbiota, and have been increasingly reported as agents of fungemia in immunocompromised patients. Biofilms derived from clinical strains of T asahii (n=5) and T. inkin (n=7) were formed in flat-bottomed microtiter plates and incubated at 35°C for 48 h, treated with 100 μg/ml amphotericin B (AMB) and incubated at 35°C for additional 24 h. Biofilms were scraped from the wells and persister cells were assayed for susceptibility to AMB. Additionally, we investigated if these persister cells were able to generate new biofilms and studied their ultrastructure and AMB susceptibility. Persister cells were detected in both T asahii and T. inkin biofilms and showed tolerance to high doses of AMB (up to 256 times higher than the minimum inhibitory concentration). Persister cells were able to generate biofilms, however they presented reduced biomass and metabolic activity, and reduced tolerance to AMB, in comparison to biofilm growth control. The present study describes the occurrence of persister cells in Trichosporon spp. and suggests their role in the reduced AMB susceptibility of T. asahii and T. inkin biofilms.

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.

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.

Urinary Tract Infections Caused by Fluconazole-Resistant Trichosporon japonicum in 2 Kidney Transplant Patients and Analysis of Their Homology

Trichosporon spp. are emerging opportunistic agents that cause systemic diseases and life-threatening disseminated disease in immunocompromised hosts. Trichosporon japonicum is a highly rare cause of invasive trichosporonosis. In this study, we describe 2 cases of urinary tract infection caused by Trichosporon japonicum in kidney transplant patients. Culturing of urine samples yielded bluish-green colonies of T. japonicum on Candida chromogenic fungal medium. The isolates were identified as T. japonicum by matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI TOF-MS; Autof MS 1000). The identification of T. japonicum was further confirmed by 18S rRNA gene sequencing. In vitro drug susceptibility testing showed that the 2 strains of T. japonicum were resistant to 5-flucytosine, fluconazole, and caspofungin, with dose-dependent sensitivity to itraconazole and voriconazole but sensitivity to amphotericin B. The homology of the 2 T. japonicum strains, as determined by cluster analysis and principal component analysis of MALDI-TOF MS, was ~85%, suggesting a common nosocomial origin. The first 2 case reports of fluconazole-resistant T. japonicum urinary infection in kidney transplant recipients are presented.