Catheter-Related Trichosporon asahii Bloodstream Infection in a Neutropenic Patient with Myelodysplastic Syndrome

Update on therapeutic approaches for invasive fungal infections in adults

Invasive fungal infections are increasingly encountered with the expansion of iatrogenic immunosuppression, including not only solid organ and hematopoietic stem cell transplant recipients but also patients with malignancies or autoimmune diseases receiving immunomodulatory therapies, such as Bruton Tyrosine Kinase (BTK) inhibitor. Their attributable mortality remains elevated, part of which is a contribution from globally emerging resistance in both molds and yeasts. Because antifungal susceptibility test results are often unavailable or delayed, empiric and tailored antifungal approaches including choice of agent(s) and use of combination therapy are heterogeneous and often based on clinician experience with knowledge of host's net state of immunosuppression, prior antifungal exposure, antifungal side effects and interaction profile, clinical severity of disease including site(s) of infection and local resistance data. In this review, we aim to summarize previous recommendations and most recent literature on treatment of invasive mold and yeast infections in adults to guide optimal evidence-based therapeutic approaches. We review the recent data that support use of available antifungal agents, including the different triazoles that have now been studied in comparison to previously preferred agents. We discuss management of complex infections with specific emerging fungi such as Scedosporium spp., Fusarium spp., Trichosporon asahii, and Candida auris. We briefly explore newer antifungal agents or formulations that are now being investigated to overcome therapeutic pitfalls, including but not limited to olorofim, rezafungin, fosmanogepix, and encochleated Amphotericin B. We discuss the role of surgical resection or debridement, duration of treatment, follow-up modalities, and need for secondary prophylaxis, all of which remain challenging, especially in patients chronically immunocompromised or awaiting more immunosuppressive therapies.

Phenotypic and Genotypic Identification of Yeast Species Isolated from Diabetic Foot Patients in Al-Najaf Province, Iraq

Opportunistic yeasts, such as Trichosporon and Candida species (spp.), are reported to cause high rates of morbidity and mortality in immunocompromised and underlying patients. This study was conducted to investigate the phenotypic and genotypic identification of yeast spp. isolated from diabetic patients in Al-Najaf province, Iraq. Samples were collected from the depth of diabetic foot patients' wounds. They were then cultured on Sabouraud Dextrose Agar (SDA) and incubated at 30°C to 35°C for 5 to 7 days for the growth of yeast spp. The colonies were identified based on their microscopic features. Afterward, these yeast samples were cultured in CHROMagar for the isolation and identification of yeast spp. All collected samples were cultured on the SDA through the use of CHROMagar, which is considered a differential agar since the colonies obtained from Candida intermedia and Trichosporon asahii appear in different colors on this media. The Polymerase Chain Reaction assay was performed to amplify the internal transcribed spacer 1 (ITS1) and Internal transcribed spacer 4 (ITS4) sequences for the identification of the yeast spp. Furthermore, the products were sequenced by the Sanger method and compared to the reference global sequences in the national center for biotechnology information Gene Bank. The results showed different molecular sizes of the ITS regions of yeast spp. The primer pair was used for the same sample (i.e., ITS1-ITS4) and targeted the ITS regions. Yeast spp. can be considered the most common fungal agent of life-threatening invasive infections in patients with severe immunodeficiency or underlying diseases, and the treatment of these infections requires long stays in the intensive care units.

Detection of invasive Trichosporon asahii in patient blood by a fungal PCR array

Rare invasive fungal infections are increasingly emerging in hosts with predisposing factors such as immunodeficiency. Their timely diagnosis remains difficult, as their clinical picture may initially mimic infections with more common fungal species and species identification may be difficult with routine methods or may require time-consuming subcultures. This often results in ineffective drug administration and fatal outcomes. We report on a patient in their early twenties with mixed cellularity classical Hodgkin lymphoma with a disseminated Trichosporon asahii (T. asahii) infection. Even though pathogen detection and identification was possible via the standard procedure consisting of culture followed by matrix-assisted laser desorption ionisation–time of flight (MALDI-TOF) mass spectrometry, the patient passed away in the course of multi organ failure. Herein, we report on a retrospectively applied experimental diagnostic fungal PCR-analysis used on an EDTA blood sample and consisting of two pan-fungal reactions and seven branch-specific reactions. Regarding invasive T. asahii infection, this PCR array could considerably shorten time to diagnosis and switch to a targeted therapy with triazoles.

Trichosporon inkin fungemia case report: clinical and laboratory management

Trichosporon species are emerging as opportunistic pathogens that mainly affect immunocompromised patients. Patients with onco-hematological diseases usually present with fungemia by Trichosporon species, especially by T. asahii. Reports of this infection by other species of the genus are uncommon. Thus, in this paper, we present a case of T. inkin fungemia in a 39-year-old female patient with intestinal obstruction and absence of malignant hematological diseases. The late mycological diagnosis, the ineffective control of her pre-existing conditions and consequent failure to start antifungal therapy were the contributing factors for the patient's death.

Successful Treatment of Breakthrough Trichosporon asahii Fungemia by the Combination Therapy of Fluconazole and Liposomal Amphotericin B in a Patient with Follicular Lymphoma

Invasive trichosporonosis is a rare and lethal fungal infection that occurs in immunocompromised patients. Breakthrough trichosporonosis can occur in patients treated with echinocandins since Trichosporon spp. are resistant to these antifungal agents. We report a case of breakthrough Trichosporon asahii fungemia. A 62-year-old Japanese woman with relapsed follicular lymphoma was treated empirically with broad-spectrum antibiotics and micafungin due to an intermittent fever during reinduction chemotherapy. After four cycles of anti-cancer chemotherapy, she experienced a high neutropenic fever and T. asahii was subsequently detected from a blood culture. The patient was not given voriconazole due to the contraindication for use with carbamazepine, and she was successfully treated with fluconazole plus liposomal amphotericin B without any serious complications. The combined therapy of fluconazole and liposomal amphotericin B may therefore be useful in treating T. asahii fungemia, especially in patients receiving antiepileptic agents.

Introduction of a bead beating step improves fungal DNA extraction from selected patient specimens

In immunocompromised patients a colonisation with fungi carries the risk to develop serious invasive fungal infection. An early detection is therefore important, but not optimal hitherto. Fortunately, molecular genetic methods have increased the sensitivity of fungal detection and limited the time, until results are available. However, their success depends on an efficient extraction of genomic DNA from the fungal cell in the given diagnostic specimen. To improve the routine DNA preparation method for yeasts and moulds, the impact of bead beating on fungal DNA release was evaluated. PBS, blood and respiratory rinse were spiked with Candida glabrata or Aspergillus fumigatus. DNA was extracted by mechanical bead beating in addition to the different steps of the DNA preparation protocol, which comprised liquid nitrogen treatment, proteinase K digestion and DNA isolation using the EZ1 DNA Tissue Kit and Workstation. In every method variant tested, treatment with liquid nitrogen did not improve the DNA release. Bead beating once followed by proteinase K digestion and EZ1-work-up led to the highest DNA release from fungus, spiked in PBS, and increased the extracted DNA amount of C. glabrata about 100-fold and of A. fumigatus about 10-fold in relation to sole EZ1-work-up. In fungus-spiked respiratory rinse and blood, highest increase in DNA release was measured after triple bead beating with simultaneous proteinase K digestion. Fungal DNA release of C. glabrata increased for >100-fold in respiratory rinse and for >1000-fold in blood and of A. fumigatus for >10-fold in respiratory rinse and about 5- to 10-fold in blood. The data of this study clearly demonstrate that preparation of fungal DNA from human specimens is optimized by introduction of a bead beating step to the conventional DNA-preparation method without the necessity of a liquid nitrogen step.

N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine, a zinc chelator, inhibits biofilm and hyphal formation in Trichosporon asahii

Objective

Trichosporon asahii is the major causative fungus of disseminated or deep-seated trichosporonosis and forms a biofilm on medical devices. Biofilm formation leads to antifungal drug resistance, so biofilm-related infections are relatively difficult to treat and infected devices often require surgical removal. Therefore, prevention of biofilm formation is important in clinical settings. In this study, to identify metal cations that affect biofilm formation, we evaluated the effects of cation chelators on biofilm formation in T. asahii.

Results

We evaluated the effect of cation chelators on biofilm formation, since microorganisms must assimilate essential nutrients from their hosts to form and maintain biofilms. The inhibition by N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) was greater than those by other cation chelators, such as deferoxamine, triethylenetetramine, and ethylenediaminetetraacetic acid. The inhibitory effect of TPEN was suppressed by the addition of zinc. TPEN also inhibited T. asahii hyphal formation, which is related to biofilm formation, and the inhibition was suppressed by the addition of zinc. These results suggest that zinc is essential for biofilm formation and hyphal formation. Thus, zinc chelators have the potential to be developed into a new treatment for biofilm-related infection caused by T. asahii.

Disseminated Trichosporon asahii infection in a combined liver-kidney transplant recipient successfully treated with voriconazole

INTRODUCTION

Trichosporon asahii is an emerging cause of systemic fungal infection in an immunocompromised host. Several life threatening disseminated T. asahii infection in single solid organ (liver or kidney) transplant recipients, in neutropenic and hematological malignancy patients have been reported.

CASE PRESENTATION (METHODS AND RESULTS)

A 49-year old gentleman who underwent simultaneous living-donor liver transplantation (donor sister) and kidney transplant (donor wife) developed fever and subsegmental patchy consolidation with right sided pleural effusion on fourth postoperative day. Central line blood stream infection was suspected. Blood culture grew creamy white colonies of T. asahii on blood agar with characteristic dirty-green colonies on CHROMagar. Laboratory analysis of pleural fluid also revealed budding yeast cells identified as T. asahii. Microscopy of the isolates showed hyphae, arthroconidia, and blastospores. The isolates were identified as T. asahii by VITEK MS which uses matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) technology. Initially liposomal amphotericin B and micafungin was initiated, but due to lack of clinical and microbiological response, patient was switched to voriconazole. Simultaneously, tacrolimus doses were reduced to one-third in view of interaction with voriconazole. Subsequently, patient improved with resolution of fever and microbiological cure.

CONCLUSION

This is the first case report of disseminated T. asahii infection in a combined liver-kidney transplant recipient successfully treated with voriconazole. Azole antifungal are the promising drug of choice for systemic T. asahii infection. Drug interactions should be considered while using these antifungal agents.