PCR-based detection of Aspergillus fumigatus Cyp51A mutations on bronchoalveolar lavage: a multicentre validation of the AsperGenius assay® in 201 patients with haematological disease suspected for invasive aspergillosis

The Utility of Real-time PCR, Metagenomic Next-generation Sequencing, and Culture in Bronchoalveolar Lavage Fluid for Diagnosis of Pulmonary Aspergillosis

Timely detection of Aspergillus infection is crucial given the high mortality rate of pulmonary aspergillosis (PA). Here, the diagnostic performances for PA of mycological culture, Aspergillus real-time Polymerase Chain Reaction (RT-PCR), and metagenomic next-generation sequencing (mNGS) assay from bronchoalveolar lavage fluid (BALF), were evaluated. Totally 139 patients with suspected fungal pneumonia were enrolled between December 2021 and July 2023, collecting 139 BALF samples for RT-PCR and culture, with 87 undergoing mNGS assay. The sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve (AUC) with 95% confidence intervals of these assays for PA were as follows: 35.3% (14.2-61.7%), 100.0% (94.0-100.0%), 100.0% (54.1-100.0%), 84.5% (79.3-88.6%), and 0.676 (0.560-0.779) for culture; 82.4% (56.6-96.2%), 98.3% (91.1-100.0%), 93.3% (66.4-99.0%), 95.2% (87.6-98.2%) and 0.903 (0.815-0.959) for same diagnostic performance of RT-PCR and mNGS; and 94.1% (71.3-99.9%), 96.7% (88.5-99.6%), 88.9% (67.1-96.9%), 98.3% (89.6-99.7%), 0.954 (0.880-0.989) for RT-PCR combining mNGS; RT-PCR, mNGS, and their combination significantly improved in AUC values over culture (p <0.001), but RT-PCR testing and mNGS had no significant difference with each other and their combination. Overall, the performance of culture was limited by low sensitivity, both RT-PCR and mNGS assays as single diagnostic tests are promising compared to culture and combined tests.

Aspergillus fumigatus-a systematic review to inform the World Health Organization priority list of fungal pathogens

Recognizing the growing global burden of fungal infections, the World Health Organization established a process to develop a priority list of fungal pathogens (FPPL). In this systematic review, we aimed to evaluate the epidemiology and impact of invasive infections caused by Aspergillus fumigatus to inform the first FPPL. The pre-specified criteria of mortality, inpatient care, complications and sequelae, antifungal susceptibility, risk factors, preventability, annual incidence, global distribution, and emergence were used to search for relevant articles between 1 January 2016 and 10 June 2021. Overall, 49 studies were eligible for inclusion. Azole antifungal susceptibility varied according to geographical regions. Voriconazole susceptibility rates of 22.2% were reported from the Netherlands, whereas in Brazil, Korea, India, China, and the UK, voriconazole susceptibility rates were 76%, 94.7%, 96.9%, 98.6%, and 99.7%, respectively. Cross-resistance was common with 85%, 92.8%, and 100% of voriconazole-resistant A. fumigatus isolates also resistant to itraconazole, posaconazole, and isavuconazole, respectively. The incidence of invasive aspergillosis (IA) in patients with acute leukemia was estimated at 5.84/100 patients. Six-week mortality rates in IA cases ranged from 31% to 36%. Azole resistance and hematological malignancy were poor prognostic factors. Twelve-week mortality rates were significantly higher in voriconazole-resistant than in voriconazole-susceptible IA cases (12/22 [54.5%] vs. 27/88 [30.7%]; P = .035), and hematology patients with IA had significantly higher mortality rates compared with solid-malignancy cases who had IA (65/217 [30%] vs. 14/78 [18%]; P = .04). Carefully designed surveillance studies linking laboratory and clinical data are required to better inform future FPPL.

First detection of triazole-resistant aspergillus fumigatus harbouring the TR34/L98H Cyp51A mutation in Burkina Faso

BACKGROUND

Triazole-resistant Aspergillus fumigatus (TRAF) isolates are a growing public health problem with worldwide distribution. Epidemiological data on TRAF is limited in Africa, particularly in West Africa.

OBJECTIVES

This study aimed to screen for the environmental presence of TRAF isolates in the indoor air of two hospitals in Burkina Faso.

MATERIALS AND METHODS

Air samples were collected in wards housing patients at risk for invasive aspergillosis, namely infectious diseases ward, internal medicine ward, nephrology ward, pulmonology ward, medical emergency ward and paediatric ward. Sabouraud Dextrose Agar supplemented with triazoles was used to screen the suspected TRAF isolates and EUCAST method to confirm the resistance of suspected isolates. Sequencing of cyp51A gene was used to identify the resistance mechanism of confirmed TRAF isolates.

RESULTS

Of the 198 samples collected and analysed, 67 showed growth of A. fumigatus isolates. The prevalence of TRAF isolates was 3.23% (4/124). One TRAF isolate exhibited a pan-triazole resistance. Sequencing of cyp51A gene identified the TR34/L98H mutation for this pan-triazole resistant isolate. This study showed for the first time the circulation of the pan-azole resistant isolate harbouring the TR34/L98H mutation in Burkina Faso.

CONCLUSIONS

These findings emphasise the need to map these TRAF isolates in all parts of Burkina Faso and to establish local and national continuous surveillance of environmental and clinical TRAF isolates in this country.

Acute Invasive Pulmonary Aspergillosis: Clinical Presentation and Treatment

Among all clinical manifestations of pulmonary aspergillosis, invasive pulmonary aspergillosis (IPA) is the most acute presentation. IPA is caused by Aspergillus hyphae invading the pulmonary tissue, causing either tracheobronchitis and/or bronchopneumonia. The degree of fungal invasion into the respiratory tissue can be seen as a spectrum, going from colonization to deep tissue penetration with angio-invasion, and largely depends on the host's immune status. Patients with prolonged, severe neutropenia and patients with graft-versus-host disease are at particularly high risk. However, IPA also occurs in other groups of immunocompromised and nonimmunocompromised patients, like solid organ transplant recipients or critically ill patients with severe viral disease. While a diagnosis of proven IPA is challenging and often warranted by safety and feasibility, physicians must rely on a combination of clinical, radiological, and mycological features to assess the likelihood for the presence of IPA. Triazoles are the first-choice regimen, and the choice of the drug should be made on an individual basis. Adjunctive therapy such as immunomodulatory treatment should also be taken into account. Despite an improving and evolving diagnostic and therapeutic armamentarium, the burden and mortality of IPA still remains high. This review aims to give a comprehensive and didactic overview of the current knowledge and best practices regarding the epidemiology, clinical presentation, diagnosis, and treatment of acute IPA.

Clinical Implementation of β-Tubulin Gene-Based Aspergillus Polymerase Chain Reaction for Enhanced Aspergillus Diagnosis in Patients with Hematologic Diseases: A Prospective Observational Study

The β-tubulin (benA) gene is a promising target for the identification of Aspergillus species. Assessment of the clinical implementation and performance of benA gene-based Aspergillus polymerase chain reaction (PCR) remains warranted. In this study, we assessed the analytical performance of the BenA probe PCR in comparison with the Aspergenius kit. We prospectively collected bronchoalveolar lavage (BAL) fluid via diagnostic bronchoscopy from adult patients with hematologic diseases. BenA gene-based multiplex real-time PCR and sequential melting temperature analysis were performed to detect the azole resistance of Aspergillus fumigatus. In total, 76 BAL fluids in 75 patients suspicious of invasive pulmonary aspergillosis (IPA) were collected. Before the application of PCR, the prevalence of proven and probable IPA was 32.9%. However, after implementing the benA gene-based PCR, 15.8% (12 out of 76) of potential IPA cases were reclassified as probable IPA. The analytical performance of the BenA probe PCR in BAL samples was comparable to that of the Aspergenius kit. The diagnostic performance was as follows: sensitivity, 52.0%; specificity, 64.7%; positive predictive value, 41.9%; negative predictive value, 73.3%; positive likelihood ratio, 1.473; and negative likelihood ratio, 0.741. Moreover, benA gene-based Aspergillus PCR discriminated all major sections of Aspergillus, including cryptic species such as Aspergillus tubingensis. Sequential melting temperature analysis successfully detected 2 isolates (15.4%) of A. fumigatus carrying resistant mutations. BenA gene-based Aspergillus PCR with melting temperature analysis enhances diagnostic accuracy and detects not only cryptic species but also resistant mutations of A. fumigatus. It shows promise for clinical applications in the diagnosis of IPA.

The rapid emergence of antifungal-resistant human-pathogenic fungi

During recent decades, the emergence of pathogenic fungi has posed an increasing public health threat, particularly given the limited number of antifungal drugs available to treat invasive infections. In this Review, we discuss the global emergence and spread of three emerging antifungal-resistant fungi: Candida auris, driven by global health-care transmission and possibly facilitated by climate change; azole-resistant Aspergillus fumigatus, driven by the selection facilitated by azole fungicide use in agricultural and other settings; and Trichophyton indotineae, driven by the under-regulated use of over-the-counter high-potency corticosteroid-containing antifungal creams. The diversity of the fungi themselves and the drivers of their emergence make it clear that we cannot predict what might emerge next. Therefore, vigilance is critical to monitoring fungal emergence, as well as the rise in overall antifungal resistance.

Performances of disk diffusion method for determining triazole susceptibility of Aspergillus species: Systematic review

The therapeutic management of invasive aspergillosis should be guided by antifungal susceptibility testing (AFST). The disk diffusion (DD) method due to its simplicity and low cost could be an appropriate alternative to the reference methods (CLSI, EUCAST) which are not suitable for AFST in routine clinical microbiology laboratories, particularly in resource-constrained settings. This review summarizes the available data on the performance of the DD method in determining triazole susceptibility profile of Aspergillus species. The published articles on the performance of DD method for determining triazole susceptibility of Aspergillus spp. were systematically searched on major medical databases and Google Scholar. We identified 2725 articles of which 13 met the inclusion criteria. The overall average agreement value obtained between DD and CLSI broth microdilution (CLSI-BMD) methods for the itraconazole 10 µg disk (70.75%) was low especially when the medium used was not Mueller-Hinton (MH) agar. In contrast average agreement for the voriconazole 1 µg disk and the posaconazole 5 µg disk were > 94% regardless of media used. The correlation coefficient values between the DD and CLSI-BMD methods on MH agar were acceptable (≥ 0.71) for the itraconazole 10 µg disk and posaconazole 5 µg disk and good (≥ 0.80) for the voriconazole 1 and 10 µg disk. The reproducibility of the DD method regardless to the medium used was ≥ 82%. This systematic review shows that the disk diffusion method could be a real alternative for triazole antifungals susceptibility testing of Aspergillus spp.

Emerging Diagnostics and Therapeutics for Invasive Fungal Infections

Recently, there have been significant advances in the diagnosis and management of invasive fungal infections. Compared with traditional fungal diagnostics, molecular assays promise improved sensitivity and specificity, the ability to test a range of samples (including noninvasive samples, ie, blood), the detection of genetic mutations associated with antifungal resistance, and the potential for a faster turnaround time. Antifungals in late-stage clinical development include agents with novel mechanisms of action (olorofim and fosmanogepix) and new members of existing classes with distinct advantages over existing antifungals in toxicity, drug-drug interactions, and dosing convenience (oteseconazole, opelconazole, rezafungin, ibrexafungerp, encochleated amphotericin B).

Clinical Impact of Polymerase Chain Reaction-Based Aspergillus and Azole Resistance Detection in Invasive Aspergillosis: A Prospective Multicenter Study

BACKGROUND

Invasive aspergillosis (IA) by a triazole-resistant Aspergillus fumigatus is associated with high mortality. Real-time resistance detection will result in earlier initiation of appropriate therapy.

METHODS

In a prospective study, we evaluated the clinical value of the AsperGenius polymerase chain reaction (PCR) assay in hematology patients from 12 centers. This PCR assay detects the most frequent cyp51A mutations in A. fumigatus conferring azole resistance. Patients were included when a computed tomography scan showed a pulmonary infiltrate and bronchoalveolar fluid (BALf) sampling was performed. The primary end point was antifungal treatment failure in patients with azole-resistant IA.

RESULTS

Of 323 patients enrolled, complete mycological and radiological information was available for 276 (94%), and probable IA was diagnosed in 99/276 (36%). Sufficient BALf for PCR testing was available for 293/323 (91%). Aspergillus DNA was detected in 116/293 (40%) and A. fumigatus DNA in 89/293 (30%). The resistance PCR was conclusive in 58/89 (65%) and resistance detected in 8/58 (14%). Two had a mixed azole-susceptible/azole-resistant infection. In the 6 remaining patients, treatment failure was observed in 1. Galactomannan positivity was associated with mortality (P = .004) while an isolated positive Aspergillus PCR was not (P = .83).

CONCLUSIONS

Real-time PCR-based resistance testing may help to limit the clinical impact of triazole resistance. In contrast, the clinical impact of an isolated positive Aspergillus PCR on BALf seems limited. The interpretation of the EORTC/MSGERC PCR criterion for BALf may need further specification (eg, minimum cycle threshold value and/or PCR positive on >1 BALf sample).

Diagnosis of invasive fungal infections: challenges and recent developments

BACKGROUND

The global burden of invasive fungal infections (IFIs) has shown an upsurge in recent years due to the higher load of immunocompromised patients suffering from various diseases. The role of early and accurate diagnosis in the aggressive containment of the fungal infection at the initial stages becomes crucial thus, preventing the development of a life-threatening situation. With the changing demands of clinical mycology, the field of fungal diagnostics has evolved and come a long way from traditional methods of microscopy and culturing to more advanced non-culture-based tools. With the advent of more powerful approaches such as novel PCR assays, T2 Candida, microfluidic chip technology, next generation sequencing, new generation biosensors, nanotechnology-based tools, artificial intelligence-based models, the face of fungal diagnostics is constantly changing for the better. All these advances have been reviewed here giving the latest update to our readers in the most orderly flow.

MAIN TEXT

A detailed literature survey was conducted by the team followed by data collection, pertinent data extraction, in-depth analysis, and composing the various sub-sections and the final review. The review is unique in its kind as it discusses the advances in molecular methods; advances in serology-based methods; advances in biosensor technology; and advances in machine learning-based models, all under one roof. To the best of our knowledge, there has been no review covering all of these fields (especially biosensor technology and machine learning using artificial intelligence) with relevance to invasive fungal infections.

CONCLUSION

The review will undoubtedly assist in updating the scientific community's understanding of the most recent advancements that are on the horizon and that may be implemented as adjuncts to the traditional diagnostic algorithms.

Retrospective Multicenter Evaluation of the VirClia Galactomannan Antigen Assay for the Diagnosis of Pulmonary Aspergillosis with Bronchoalveolar Lavage Fluid Samples from Patients with Hematological Disease

Galactomannan (GM) testing of bronchoalveolar lavage (BAL) fluid samples has become an essential tool to diagnose invasive pulmonary aspergillosis (IPA) and is part of diagnostic guidelines. Enzyme-linked immunosorbent assays (ELISAs) (enzyme immunoassays [EIAs]) are commonly used, but they have a long turnaround time. In this study, we evaluated the performance of an automated chemiluminescence immunoassay (CLIA) with BAL fluid samples. This was a multicenter retrospective study in the Netherlands and Belgium. BAL fluid samples were collected from patients with underlying hematological diseases with a suspected invasive fungal infection. Diagnosis of IPA was based on the 2020 European Organisation for Research and Treatment of Cancer (EORTC)/Mycoses Study Group Education and Research Consortium (MSGERC) consensus definitions. GM results were reported as optical density index (ODI) values. ODI cutoff values for positive results that were evaluated were 0.5, 0.8, and 1.0 for the EIA and 0.16, 0.18, and 0.20 for the CLIA. Probable IPA cases were compared with two control groups, one with no evidence of IPA and another with no IPA or possible IPA. Qualitative agreement was analyzed using Cohen's κ, and quantitative agreement was analyzed by Spearman's correlation. We analyzed 141 BAL fluid samples from 141 patients; 66 patients (47%) had probable IPA, and 56 cases remained probable IPA when the EIA GM result was excluded as a criterion, because they also had positive culture and/or duplicate positive PCR results. Sixty-three patients (45%) had possible IPA and 12 (8%) had no IPA. The sensitivity and specificity of the two tests were quite comparable, and the overall qualitative agreement between EIA and CLIA results was 81 to 89%. The correlation of the actual CLIA and EIA values was strong at 0.72 (95% confidence interval, 0.63 to 0.80). CLIA has similar performance, compared to the gold-standard EIA, with the benefits of faster turnaround because batching is not required. Therefore, CLIA can be used as an alternative GM assay for BAL fluid samples.

Aspergillosis: an Update on Clinical Spectrum, Diagnostic Schemes, and Management

Purpose of Review

This review gives an overview of the diseases caused by Aspergillus, including a description of the species involved and the infected clinical systems. We provide insight into the various diagnostic methods available for diagnosing aspergillosis, particularly invasive aspergillosis (IA), including the role of radiology, bronchoscopy, culture, and non-culture-based microbiological methods. We also discuss the available diagnostic algorithms for the different disease conditions. This review also summarizes the main aspects of managing infections due to Aspergillus spp., such as antifungal resistance, choice of antifungals, therapeutic drug monitoring, and new antifungal alternatives.

Recent Findings

The risk factors for this infection continue to evolve with the development of many biological agents that target the immune system and the increase of viral illnesses such as coronavirus disease. Due to the limitations of present mycological test methods, establishing a fast diagnosis is frequently difficult, and reports of developing antifungal resistance further complicate the management of aspergillosis. Many commercial assays, like AsperGenius®, MycAssay Aspergillus®, and MycoGENIE®, have the advantage of better species-level identification and concomitant resistance-associated mutations. Fosmanogepix, ibrexafungerp, rezafungin, and olorofim are newer antifungal agents in the pipeline exhibiting remarkable activity against Aspergillus spp.

Summary

The fungus Aspergillus is found ubiquitously around the world and can cause various infections, from harmless saprophytic colonization to severe IA. Understanding the diagnostic criteria to be used in different patient groups and the local epidemiological data and antifungal susceptibility profile is critical for optimal patient management.

Invasive Aspergillosis and the Impact of Azole-resistance

Purpose of Review

IA (invasive aspergillosis) caused by azole-resistant strains has been associated with higher clinical burden and mortality rates. We review the current epidemiology, diagnostic, and therapeutic strategies of this clinical entity, with a special focus on patients with hematologic malignancies.

Recent Findings

There is an increase of azole resistance in Aspergillus spp. worldwide, probably due to environmental pressure and the increase of long-term azole prophylaxis and treatment in immunocompromised patients (e.g., in hematopoietic stem cell transplant recipients). The therapeutic approaches are challenging, due to multidrug-resistant strains, drug interactions, side effects, and patient-related conditions.

Summary

Rapid recognition of resistant Aspergillus spp. strains is fundamental to initiate an appropriate antifungal regimen, above all for allogeneic hematopoietic cell transplantation recipients. Clearly, more studies are needed in order to better understand the resistance mechanisms and optimize the diagnostic methods to identify Aspergillus spp. resistance to the existing antifungal agents/classes. More data on the susceptibility profile of Aspergillus spp. against the new classes of antifungal agents may allow for better treatment options and improved clinical outcomes in the coming years. In the meantime, continuous surveillance studies to monitor the prevalence of environmental and patient prevalence of azole resistance among Aspergillus spp. is absolutely crucial.

A systematic review of epidemiology, risk factors, diagnosis, antifungal resistance, and management of invasive aspergillosis in Africa

Invasive aspergillosis (IA) affects more than 300,000 people annually worldwide with a case fatality rate reaching 80%. However, in Africa despite the presence of risk factors for the development of IA, the burden of these fungal infections remained unknown. This systematic review aimed to update the available information on the epidemiology and the therapeutic management of IA in Africa. The published papers were systematically searched on major medical databases from September 20 to October 10, 2021. The list of references of eligible articles and the Google scholar database were also checked in order to search for possible eligible articles. Results were reported following the Preferred Reporting Items for Systematic and Meta-analyses (PRISMA) guidelines. The search yielded 1864 articles of which 29 met the inclusion criteria. This systematic review showed the existence of IA in Africa. The prevalence of IA can reach 27% with a fatality rate of more than 60%. The most common clinical form of IA found was invasive pulmonary aspergillosis. The main predisposing conditions identified were neutropenia, HIV/AIDS, renal transplant recipients, and renal failure. Aspergillus section Flavi and Nigri were the main Aspergillus species identified and Aspergillus section Fumigati was uncommon. The main management strategy for IA cases was to start antifungal therapy only after a failure of broad-spectrum antibiotic therapy. This review provided evidence of the existence of invasive aspergillosis in Africa and especially a high rate of undiagnosed invasive aspergillosis cases.

Molecular detection of Aspergillus in respiratory samples collected from patients at higher risk of chronic pulmonary aspergillosis

OBJECTIVE

Aspergillosis diagnosis depends on the detection of Aspergillus in biological samples ─ usually using cultural and immunoenzyme techniques ─ but their sensitivity and specificity varies. We aimed to study the prevalence of Aspergillus in patients at higher risk of chronic pulmonary aspergillosis (i.e., HIV-infected patients and individuals with active or previous tuberculosis), and to determine the potential role of molecular approaches to increase detection of Aspergillus in respiratory samples.

METHODS

The DNA extracted from 43 respiratory samples that had been previously analyzed by immunoenzyme and/or cultural techniques was amplified by real-time multiplex PCR, and the results of these methods were compared. We also sequenced the ITS1 region and the calmodulin gene in 10 respiratory samples to perform a pilot metagenomic study to understand the ability of this methodology to detect potential pathogenic fungi in the lung mycobiome.

RESULTS

Real-time Aspergillus PCR test exhibited a higher positivity rate than the conventional techniques used for aspergillosis diagnosis, particularly in individuals at risk for chronic pulmonary aspergillosis. The metagenomic analysis allowed for the detection of various potentially pathogenic fungi.

CONCLUSIONS

Molecular techniques, including metagenomics, have great ability to detect potentially pathogenic fungi rapidly and efficiently in human biological samples.

Bronchoalveolar lavage fluid polymerase chain reaction for invasive pulmonary aspergillosis among high-risk patients: a diagnostic meta-analysis

BACKGROUND

Polymerase chain reaction (PCR) assays are perceived to facilitate the diagnosis of fungal infections. However, due to lack of standardization, the value of bronchoalveolar lavage (BAL) fluid PCR in diagnosis of invasive pulmonary aspergillosis (IPA) remains unclear.

METHODS

We conducted a systematic meta-analysis to evaluate the accuracy of BAL fluid PCR in IPA diagnosis among high-risk patients. All studies involving patients at risk for IPA were included. The sensitivity, specificity, positive and negative likelihood ratios of BAL fluid PCR were summarized for diagnosis of proven/probable IPA, or proven IPA only. Potential heterogeneity was assessed by subgroup analyses and meta-regression.

RESULTS

Forty-one studies involving 5668 patients were analyzed. The summary sensitivity, specificity, positive and negative likelihood ratios of BAL fluid PCR for proven/probable IPA were 0.75 (95% CI = 0.67-0.81), 0.94 (95% CI = 0.90-0.96), 11.8 (95% CI = 7.7-18.1) and 0.27 (95% CI = 0.20-0.36), respectively. Whereas for proven IPA only, sensitivity and specificity were 0.91 (95% CI = 0.68-0.98) and 0.80 (95% CI = 0.74-0.85) in fourteen studies involving 2061 patients. Significant heterogeneity was present due to the underlying disease, antifungal treatment and differences in DNA extraction techniques and choice of PCR assay. Compared to patients with hematological malignancies (HM) and hematopoietic stem cell/solid organ transplantation (HSCT/SOT), sensitivity was higher in the population with disease such as chronic obstructive pulmonary disease, solid tumor, autoimmune disease with prolonged use of corticosteroids, etc. (0.88 vs. 0.68, P < 0.001), which was related to the concurrent use of antifungal prophylaxis among patients with HM and HSCT/SOT.

CONCLUSION

BAL fluid PCR is a useful diagnostic tool for IPA in immunocompromised patients and is also effective for diagnosing IPA in patients without HM and HSCT/SOT. Furthermore, standard protocols for DNA extraction and PCR assays should be focused on to improve the diagnostic accuracy. Trial registration PROSPERO, registration number CRD42021239028.

Tackling the emerging threat of antifungal resistance to human health

Invasive fungal infections pose an important threat to public health and are an under-recognized component of antimicrobial resistance, an emerging crisis worldwide. Across a period of profound global environmental change and expanding at-risk populations, human-infecting pathogenic fungi are evolving resistance to all licensed systemic antifungal drugs. In this Review, we highlight the main mechanisms of antifungal resistance and explore the similarities and differences between bacterial and fungal resistance to antimicrobial control. We discuss the research and innovation topics that are needed for risk reduction strategies aimed at minimizing the emergence of resistance in pathogenic fungi. These topics include links between the environment and One Health, surveillance, diagnostics, routes of transmission, novel therapeutics and methods to mitigate hotspots for fungal adaptation. We emphasize the global efforts required to steward our existing antifungal armamentarium, and to direct the research and development of future therapies and interventions.

Optimization of a Quantitative PCR Methodology for Detection of Aspergillus spp. and Rhizopus arrhizus

Introduction

Multiplex quantitative polymerase chain reaction (qPCR) methods for the detection of Aspergillus spp. based only on SYBR Green and melting curve analysis of PCR products are difficult to develop because most targets are located within ITS regions. The aim of this study was to adapt our previously developed methodology based on a multiplex PCR assay coupled with GeneScan analysis to provide a qPCR method.

Methods

A SYBR Green-based real-time PCR assay was optimized to detect A. fumigatus, A. flavus, A. niger, A. terreus, and R. arrhizus in a multiplex assay and applied to cultured fungi and spiked plasma.

Results

Different melting temperatures allowed identification of all five pathogens and discrimination between them, even in samples with low amounts of fungal gDNA (from 1.3 to 33.0 pg/μL), which has been reported previously as problematic. No false-positive results were obtained for non-target species, including bacteria and human DNA. This method allowed detection of fungal pathogens in human plasma spiked with fungal DNA and in coinfections of A. niger/R. arrhizus.

Discussion

This work provides evidence for the use of a qPCR multiplex method based on SYBR Green and melting curve analysis of PCR products for the detection of A. fumigatus, A. flavus, A. niger, A. terreus, and R. arrhizus. The proposed method is simpler and less expensive than available kits based on fluorescent probes and can be used for aiding diagnosis of the most relevant invasive filamentous fungi, particularly in low-income health care institutions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40291-022-00595-1.

Aspergillus-PCR in bronchoalveolar lavage diagnostic accuracy for invasive pulmonary aspergillosis in critically ill patients

BACKGROUND

Diagnosis of invasive pulmonary aspergillosis (IPA) in intensive care unit (ICU) patients is challenging and the role of Aspergillus-PCR in bronchoalveolar lavage (BAL) is unknown.

OBJECTIVES

This study evaluated diagnostic accuracy of Aspergillus-PCR in BAL in IPA in three different cohorts: ICU-admitted patients with COVID-19, ICU-admitted patients without COVID-19 and immunocompromised patients.

METHODS

All stored available BAL samples collected from three patient groups were tested with Aspergillus-PCR (AsperGenius®). IPA was diagnosed according to appropriate criteria for each patient group.

RESULTS

We included 111 BAL samples from 101 patients: 52 (51%) patients admitted to ICU for COVID-19, 24 (24%) admitted to ICU for other reasons and 25 (25%) immunocompromised. There were 31 cases of IPA (28%). Aspergillus-PCR sensitivity was 64% (95%CI 47-79), specificity 99% (95%CI 93-100). Aspergillus-PCR sensitivity was 40% (95%CI 19-64) in ICU COVID-19, 67% (95%CI 21-93) in non-COVID-19 ICU patients and 92% (95%CI 67-98) in the immunocompromised. The concordance between positive BAL-GM and BAL-PCR in patients with and without IPA was significantly lower in ICU patients (32%; 43% in COVID-19, 18% in non-COVID-19) than in the immunocompromised (92%), p<0.001.

CONCLUSIONS

Aspergillus-PCR in BAL improves the diagnostic accuracy of BAL-GM in ICU patients.

An overview of using fungal DNA for the diagnosis of invasive mycoses

INTRODUCTION

Fungal PCR has undergone considerable standardization and together with the availability of commercial assays, external quality assessment schemes and extensive performance validation data, is ready for widespread use for the screening and diagnosis of invasive fungal disease (IFD).

AREAS COVERED

Drawing on the experience and knowledge of the leads of the various working parties of the Fungal PCR initiative, this review will address general considerations concerning the use of molecular tests for the diagnosis of IFD, before focussing specifically on the technical and clinical aspects of molecular testing for the main causes of IFD and recent technological developments.

EXPERT OPINION

For infections caused by Aspergillus, Candida and Pneumocystis jirovecii, PCR testing is recommended, combination with serological testing will likely enhance the diagnosis of these diseases. For other IFD (e.g. Mucormycosis) molecular diagnostics, represent the only non-classical mycological approach towards diagnoses and continued performance validation and standardization has improved confidence in such testing. The emergence of antifungal resistance can be diagnosed, in part, through molecular testing. Next-generation sequencing has the potential to significantly improve our understanding of fungal phylogeny, epidemiology, pathogenesis, mycobiome/microbiome and interactions with the host, while identifying novel and existing mechanisms of antifungal resistance and novel diagnostic/therapeutic targets.

OUP accepted manuscript

The increasing incidence and changing epidemiology of invasive fungal infections continue to present many challenges to their effective management. The repertoire of antifungal drugs available for treatment is still limited although there are new antifungals on the horizon. Successful treatment of invasive mycoses is dependent on a mix of pathogen-, host- and antifungal drug-related factors. Laboratories need to be adept at detection of fungal pathogens in clinical samples in order to effectively guide treatment by identifying isolates with acquired drug resistance. While there are international guidelines on how to conduct in vitro antifungal susceptibility testing, these are not performed as widely as for bacterial pathogens. Furthermore, fungi generally are recovered in cultures more slowly than bacteria, and often cannot be cultured in the laboratory. Therefore, non-culture-based methods, including molecular tests, to detect fungi in clinical specimens are increasingly important in patient management and are becoming more reliable as technology improves. Molecular methods can also be used for detection of target gene mutations or other mechanisms that predict antifungal drug resistance. This review addresses acquired antifungal drug resistance in the principal human fungal pathogens and describes known resistance mechanisms and what in-house and commercial tools are available for their detection. It is emphasized that this approach should be complementary to culture-based susceptibility testing, given the range of mutations, resistance mechanisms and target genes that may be present in clinical isolates, but may not be included in current molecular assays.

Fungal infections diagnosis - Past, present and future

Despite the scientific advances observed in the recent decades and the emergence of new methodologies, the diagnosis of systemic fungal infections persists as a problematic issue. Fungal cultivation, the standard method that allows a proven diagnosis, has numerous disadvantages, as low sensitivity (only 50% of the patients present positive fungal cultures), and long growth time. These are factors that delay the patient's treatment and, consequently, lead to higher hospital costs. To improve the accuracy and quickness of fungal infections diagnosis, several new methodologies attempt to be implemented in clinical microbiology laboratories. Most of these innovative methods are independent of pathogen isolation, which means that the diagnosis goes from being considered proven to probable. In spite of the advantage of being culture-independent, the majority of the methods lack standardization. PCR-based methods are becoming more and more commonly used, which has earned them an important place in hospital laboratories. This can be perceived now, as PCR-based methodologies have proved to be an essential tool fighting against the COVID-19 pandemic. This review aims to go through the main steps of the diagnosis for systemic fungal infection, from diagnostic classifications, through methodologies considered as "gold standard", to the molecular methods currently used, and finally mentioning some of the more futuristic approaches.

Implementation of a clinical decision rule for selecting empiric treatment for invasive aspergillosis in a setting with high triazole resistance

World-wide, emerging triazole resistance increasingly complicates treatment of invasive aspergillosis (IA). In settings with substantial (>10%) prevalence of triazole resistance, empiric combination therapy with both a triazole and liposomal amphotericin B (LAmB) can be considered because of the low yields of susceptibility testing. To avoid toxicity while optimizing outcome, a strategy with monotherapy would be preferable. A newly designed treatment algorithm based on literature and expert consensus provided guidance for empiric monotherapy with either voriconazole or LAmB. Over a four and a half year period, all adult patients in our hospital treated for IA were included and patient data were collected. An independent committee reviewed the attributability of death to IA for each patient. Primary outcomes were 30- and 100-day crude mortality and attributable mortality. In total, 110 patients were treated according to the treatment algorithm. Fifty-six patients (51%) were initially treated with voriconazole and 54 patients (49%) with LAmB. Combined attributable and contributable mortality was 13% within 30 days and 20% within 100 days. Treatment switch to LAmB was made in 24/56 (43%) of patients who were initially treated with voriconazole. Combined contributable and attributable 100-day mortality in this subgroup was 21% and was not increased when compared with patients initially treated with LAmB (P = 0.38). By applying a comprehensive clinical decision algorithm, an antifungal-sparing regime was successfully introduced. Further research is warranted to explore antifungal treatment strategies that account for triazole-resistance.

LAY SUMMARY

Due to resistance of Aspergillus against triazoles, combination therapy with liposomal amphotericin B (LAmB) is applied more often as primary therapy against invasive aspergillosis. This study presents the results of a decision tool which differentiated between triazole or LAmB monotherapy.

Early oseltamivir reduces risk for influenza-associated aspergillosis in a double-hit murine model

Invasive pulmonary aspergillosis (IPA) is a life-threatening fungal infection occurring mainly in immunocompromised patients. We recently identified IPA as an emerging co-infection with high mortality in critically ill, but otherwise immunocompetent influenza patients. The neuraminidase inhibitor oseltamivir is the current standard-of-care treatment in hospitalized influenza patients; however, its efficacy in influenza-associated pulmonary aspergillosis (IAPA) is not known. Therefore, we have established an imaging-supported double-hit mouse model to investigate the therapeutic effect of oseltamivir on the development of IAPA. Immunocompetent mice received intranasal instillation influenza A or PBS followed by orotracheal inoculation with Aspergillus fumigatus 4 days later. Oseltamivir treatment or placebo was started at day 0, day 2, or day 4. Daily monitoring included micro-computed tomography and bioluminescence imaging of pneumonia and fungal burden. Non-invasive biomarkers were complemented with imaging, molecular, immunological, and pathological analysis. Influenza virus-infected immunocompetent mice developed proven airway IPA upon co-infection with Aspergillus fumigatus, whereas non-influenza-infected mice fully cleared Aspergillus, confirming influenza as a risk factor for developing IPA. Longitudinal micro-CT showed pulmonary lesions after influenza infection worsening after Aspergillus co-infection, congruent with bioluminescence imaging and histology confirming Aspergillus pneumonia. Early oseltamivir treatment prevented severe influenza pneumonia and mitigated the development of IPA and associated mortality. A time-dependent treatment effect was consistently observed with imaging, molecular, and pathological analyses. Hence, our findings underscore the importance of initiating oseltamivir as soon as possible, to suppress influenza infection and mitigate the risk of potentially lethal IAPA disease.

When to change treatment of acute invasive aspergillosis: an expert viewpoint

Invasive aspergillosis (IA) is an acute infection affecting patients who are immunocompromised, as a result of receiving chemotherapy for malignancy, or immunosuppressant agents for transplantation or autoimmune disease. Whilst criteria exist to define the probability of infection for clinical trials, there is little evidence in the literature or clinical guidelines on when to change antifungal treatment in patients who are receiving prophylaxis or treatment for IA. To try and address this significant gap, an advisory board of experts was convened to develop criteria for the management of IA for use in designing clinical trials, which could also be used in clinical practice. For primary treatment failure, a change in antifungal therapy should be made: (i) when mycological susceptibility testing identifies an organism from a confirmed site of infection, which is resistant to the antifungal given for primary therapy, or a resistance mutation is identified by molecular testing; (ii) at, or after, 8 days of primary antifungal treatment if there is increasing serum galactomannan, or galactomannan positivity in serum, or bronchoalveolar lavage fluid when the antigen was previously undetectable, or there is sudden clinical deterioration, or a new clearly distinct site of infection is detected; and (iii) at, or after, 15 days of primary antifungal treatment if the patient is clinically stable but with ≥2 serum galactomannan measurements persistently elevated compared with baseline or increasing, or if the original lesions on CT or other imaging, show progression by >25% in size in the context of no apparent change in immune status.

Aspergillus fumigatus and aspergillosis: From basics to clinics

The airborne fungus Aspergillus fumigatus poses a serious health threat to humans by causing numerous invasive infections and a notable mortality in humans, especially in immunocompromised patients. Mould-active azoles are the frontline therapeutics employed to treat aspergillosis. The global emergence of azole-resistant A. fumigatus isolates in clinic and environment, however, notoriously limits the therapeutic options of mould-active antifungals and potentially can be attributed to a mortality rate reaching up to 100 %. Although specific mutations in CYP 51A are the main cause of azole resistance, there is a new wave of azole-resistant isolates with wild-type CYP 51A genotype challenging the efficacy of the current diagnostic tools. Therefore, applications of whole-genome sequencing are increasingly gaining popularity to overcome such challenges. Prominent echinocandin tolerance, as well as liver and kidney toxicity posed by amphotericin B, necessitate a continuous quest for novel antifungal drugs to combat emerging azole-resistant A. fumigatus isolates. Animal models and the tools used for genetic engineering require further refinement to facilitate a better understanding about the resistance mechanisms, virulence, and immune reactions orchestrated against A. fumigatus. This review paper comprehensively discusses the current clinical challenges caused by A. fumigatus and provides insights on how to address them.

Future challenges and chances in the diagnosis and management of invasive mould infections in cancer patients

Diagnosis, treatment, and management of invasive mould infections (IMI) are challenged by several risk factors, including local epidemiological characteristics, the emergence of fungal resistance and the innate resistance of emerging pathogens, the use of new immunosuppressants, as well as off-target effects of new oncological drugs. The presence of specific host genetic variants and the patient's immune system status may also influence the establishment of an IMI and the outcome of its therapy. Immunological components can thus be expected to play a pivotal role not only in the risk assessment and diagnosis, but also in the treatment of IMI. Cytokines could improve the reliability of an invasive aspergillosis diagnosis by serving as biomarkers as do serological and molecular assays, since they can be easily measured, and the turnaround time is short. The use of immunological markers in the assessment of treatment response could be helpful to reduce overtreatment in high risk patients and allow prompt escalation of antifungal treatment. Mould-active prophylaxis could be better targeted to individual host needs, leading to a targeted prophylaxis in patients with known immunological profiles associated with high susceptibility for IMI, in particular invasive aspergillosis. The alteration of cellular antifungal immune response through oncological drugs and immunosuppressants heavily influences the outcome and may be even more important than the choice of the antifungal treatment. There is a need for the development of new antifungal strategies, including individualized approaches for prevention and treatment of IMI that consider genetic traits of the patients.

Lay Abstract

Anticancer and immunosuppressive drugs may alter the ability of the immune system to fight invasive mould infections and may be more important than the choice of the antifungal treatment. Individualized approaches for prevention and treatment of invasive mold infections are needed.

Update on Non-Culture-Based Diagnostics for Invasive Fungal Disease

Diagnostic tests for fungi provide the mycological evidence to strengthen diagnosis of invasive fungal disease. Conventional microbiology and histopathology have their limitations. Recognizing this, there have been attempts at developing new methods to improve yield of diagnosing invasive fungal disease (IFD). The recent focus has been on non-culture-based antigen detection and molecular methods. The use of antigen detection of IFD through 1,3-β-D-glucan and galactomannan assay have been expanded, followed by development of lateral flow assays, and in combination with other diagnostic modalities to further increase diagnostic yield. The molecular diagnostic front has seen initiatives to standardize polymerase chain reaction methodologies to detect fungi and anti-fungal resistance, new platforms such as the T2Candida Biosystems and foray into fungal metagenomics. As these newer assays undergo stringent validation before incorporation into the diagnostic algorithm, the clinician needs to be mindful of their bedside utility as well as their limitation.

Paradoxal Trends in Azole-Resistant Aspergillus fumigatus in a National Multicenter Surveillance Program, the Netherlands, 2013-2018

We investigated the prevalence of azole resistance of Aspergillus fumigatus isolates in the Netherlands by screening clinical A. fumigatus isolates for azole resistance during 2013-2018. We analyzed azole-resistant isolates phenotypically by in vitro susceptibility testing and for the presence of resistance mutations in the Cyp51A gene. Over the 6-year period, 508 (11%) of 4,496 culture-positive patients harbored an azole-resistant isolate. Resistance frequency increased from 7.6% (95% CI 5.9%-9.8%) in 2013 (58/760 patients) to 14.7% (95% CI 12.3%-17.4%) in 2018 (112/764 patients) (p = 0.0001). TR₃₄/L98H (69%) and TR₄₆/Y121F/T289A (17%) accounted for 86% of Cyp51A mutations. However, the mean voriconazole MIC of TR₃₄/L98H isolates decreased from 8 mg/L (2013) to 2 mg/L (2018), and the voriconazole-resistance frequency was 34% lower in 2018 than in 2013 (p = 0.0001). Our survey showed changing azole phenotypes in TR₃₄/L98H isolates, which hampers the use of current PCR-based resistance tests.

Aspergillus Polymerase Chain Reaction-An Update on Technical Recommendations, Clinical Applications, and Justification for Inclusion in the Second Revision of the EORTC/MSGERC Definitions of Invasive Fungal Disease

Aspergillus polymerase chain reaction testing of blood and respiratory samples has recently been included in the second revision of the EORTC/MSGERC definitions for classifying invasive fungal disease. This is a result of considerable efforts to standardize methodology, the availability of commercial assays and external quality control programs, and additional clinical validation. This supporting article provides both clinical and technical justifications for its inclusion while also summarizing recent advances and likely future developments in the molecular diagnosis of invasive aspergillosis.

Invasive aspergillosis in solid organ transplant patients: diagnosis, prophylaxis, treatment, and assessment of response

BACKGROUND

Invasive aspergillosis (IA) is a rare complication in solid organ transplant (SOT) recipients. Although IA has significant implications on graft and patient survival, data on diagnosis and management of this infection in SOT recipients are still limited.

METHODS

Discussion of current practices and limitations in the diagnosis, prophylaxis, and treatment of IA and proposal of means of assessing treatment response in SOT recipients.

RESULTS

Liver, lung, heart or kidney transplant recipients have common as well as different risk factors to the development of IA, thus each category needs a separate evaluation. Diagnosis of IA in SOT recipients requires a high degree of awareness, because established diagnostic tools may not provide the same sensitivity and specificity observed in the neutropenic population. IA treatment relies primarily on mold-active triazoles, but potential interactions with immunosuppressants and other concomitant therapies need special attention.

CONCLUSIONS

Criteria to assess response have not been sufficiently evaluated in the SOT population and CT lesion dynamics, and serologic markers may be influenced by the underlying disease and type and severity of immunosuppression. There is a need for well-orchestrated efforts to study IA diagnosis and management in SOT recipients and to develop comprehensive guidelines for this population.

Respiratory Mycoses in COPD and Bronchiectasis

Chronic obstructive pulmonary disease (COPD) and bronchiectasis represent chronic airway diseases associated with significant morbidity and mortality. Bacteria and viruses are commonly implicated in acute exacerbations; however the significance of fungi in these airways remains poorly defined. While COPD and bronchiectasis remain recognized risk factors for the occurrence of Aspergillus-associated disease including chronic and invasive aspergillosis, underlying mechanisms that lead to the progression from colonization to invasive disease remain uncertain. Nonetheless, advances in molecular technologies have improved our detection, identification and understanding of resident fungi characterizing these airways. Mycobiome sequencing has revealed the complex varied and myriad profile of airway fungi in COPD and bronchiectasis, including their association with disease presentation, progression, and mortality. In this review, we outline the emerging evidence for the clinical importance of fungi in COPD and bronchiectasis, available diagnostic modalities, mycobiome sequencing approaches and association with clinical outcomes.

Molecular Markers of Antifungal Resistance: Potential Uses in Routine Practice and Future Perspectives

Antifungal susceptibility testing (AST) has come to establish itself as a mandatory routine in clinical practice. At the same time, the mycological diagnosis seems to have headed in the direction of non-culture-based methodologies. The downside of these developments is that the strains that cause these infections are not able to be studied for their sensitivity to antifungals. Therefore, at present, the mycological diagnosis is correctly based on laboratory evidence, but the antifungal treatment is undergoing a growing tendency to revert back to being empirical, as it was in the last century. One of the explored options to circumvent these problems is to couple non-cultured based diagnostics with molecular-based detection of intrinsically resistant organisms and the identification of molecular mechanisms of resistance (secondary resistance). The aim of this work is to review the available molecular tools for antifungal resistance detection, their limitations, and their advantages. A comprehensive description of commercially available and in-house methods is included. In addition, gaps in the development of these molecular technologies are discussed.

Evaluation of Three Commercial PCR Assays for the Detection of Azole-Resistant Aspergillus fumigatus from Respiratory Samples of Immunocompromised Patients

This is the first study comparing three commercially available PCR assays for the detection of Aspergillus DNA from respiratory specimen of immunocompromised patients and the presence of cyp51A gene mutations. Bronchoalveolar lavages (BALs, N = 103) from patients with haematological/oncological underlying diseases were retrospectively investigated. The performance of three PCR assays, namely MycoGENIE^®Aspergillus fumigatus Real-Time PCR Kit (Adamtech), Fungiplex^®Aspergillus Azole-R IVD Real-Time PCR Kit (Bruker Daltonik GmbH) and AsperGenius^® (PathoNostics B.V.), were evaluated. All patients were categorised following current EORTC/MSG criteria, with exclusion of the PCR-results. From the 11 invasive pulmonary aspergillosis (IPA) probable samples, eight were detected with MycoGENIE^®, resulting in a sensitivity of 80% and a specificity of 73%. Furthermore, Fungiplex^® resulted in six positive BALs with a sensitivity of 60% and a specificity of 91% and AsperGenius^® in seven positive BAL samples, with a sensitivity of 64% and a specificity of 97%. No proven IPA was detected. One isolate showed phenotypically an azole-resistance, which was also detected in each of the tested PCR assays with the mutation in TR34. The here tested PCR assays were capable of reliably detecting A. fumigatus DNA, as well as differentiation of the common cyp51A gene mutations. However, evaluation on the AsperGenius^® assay revealed a low risk of false positive results.

Role and Interpretation of Antifungal Susceptibility Testing for the Management of Invasive Fungal Infections

Invasive fungal infections (IFIs) are associated with high mortality rates and timely appropriate antifungal therapy is essential for good outcomes. Emerging antifungal resistance among Candida and Aspergillus spp., the major causes of IFI, is concerning and has led to the increasing incorporation of in vitro antifungal susceptibility testing (AST) to guide clinical decisions. However, the interpretation of AST results and their contribution to management of IFIs remains a matter of debate. Specifically, the utility of AST is limited by the delay in obtaining results and the lack of pharmacodynamic correlation between minimal inhibitory concentration (MIC) values and clinical outcome, particularly for molds. Clinical breakpoints for Candida spp. have been substantially revised over time and appear to be reliable for the detection of azole and echinocandin resistance and for outcome prediction, especially for non-neutropenic patients with candidemia. However, data are lacking for neutropenic patients with invasive candidiasis and some non-albicans Candida spp. (notably emerging Candida auris). For Aspergillus spp., AST is not routinely performed, but may be indicated according to the epidemiological context in the setting of emerging azole resistance among A. fumigatus. For non-Aspergillus molds (e.g., Mucorales, Fusarium or Scedosporium spp.), AST is not routinely recommended as interpretive criteria are lacking and many confounders, mainly host factors, seem to play a predominant role in responses to antifungal therapy. This review provides an overview of the pre-clinical and clinical pharmacodynamic data, which constitute the rationale for the use and interpretation of AST testing of yeasts and molds in clinical practice.

Updated EUCAST Clinical Breakpoints against Aspergillus, Implications for the Clinical Microbiology Laboratory

Azole resistance poses a problem for the management of patients with invasive aspergillosis. Former species are in fact groups of closely related species (or complexes); cryptic species frequently show high antifungal resistance. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) EUCAST Definitive Document (E.Def) 9.3.2 includes guidelines for antifungal susceptibility testing on Aspergillus spp. and clinical breakpoints for amphotericin B, itraconazole, voriconazole, posaconazole, and isavuconazole against A. flavus, A. fumigatus, A. nidulans, A. niger, and A. terreus. New clinical breakpoints were released in February 2020 and one of the most relevant modifications was the definition of the new "susceptible, increased exposure" (formerly "intermediate") category. Another relevant change was the adoption of the concept of area of technical uncertainty (ATU) that refers to problematic areas which involve uncertainty of susceptibility categorisation (e.g., when minimum inhibitory concentrations (MICs) for susceptible and resistant organisms overlap). To accommodate both the new "susceptible, increased exposure" category and the concept of ATU, MICs of azoles and amphotericin B that fall in the former "intermediate" category have been automatically categorized as either R (amphotericin B) or ATU (triazoles). Finally, EUCAST-AFST (Antifungal Susceptibility Testing) decided to adopt new breakpoints for less common species provided that the epidemiological cut-off value (ECOFF) is below or comparable to the breakpoint for the type species (A. fumigatus).

Emerging Microbiology Diagnostics for Transplant Infections: On the Cusp of a Paradigm Shift

In light of the heightened risk for infection associated with solid organ and hematopoietic stem cell transplantation, rapid and accurate microbiology diagnostics are essential to the practice of transplant clinicians, including infectious diseases specialists. In the last decade, diagnostic microbiology has seen a shift toward culture-independent techniques including single-target and multiplexed molecular testing, mass-spectrometry, and magnetic resonance-based methods which have together greatly expanded the array of pathogens identified, increased processing speed and throughput, allowed for detection of resistance determinants, and ultimately improved the outcomes of infected transplant recipients. More recently, a newer generation of diagnostics with immense potential has emerged, including multiplexed molecular panels directly applicable to blood and blood culture specimens, next-generation metagenomics, and gas chromatography mass spectrometry. Though these methods have some recognized drawbacks, many have already demonstrated improved sensitivity and a positive impact on clinical outcomes in transplant and immunocompromised patients.

Azole resistance survey on clinical Aspergillus fumigatus isolates in Spain

OBJECTIVES

We aimed to assess the percentage of azole resistance in Aspergillus fumigatus in Spain.

METHODS

Thirty participating Spanish hospitals stored all morphologically identified A. fumigatus sensu lato clinical isolates-regardless their clinical significance-from 15 February to 14 May 2019. Isolates showing azole resistance according to the EUCAST 9.3.2 methodology were molecularly identified and the cyp51A gene was studied in A. fumigatus sensu stricto isolates.

RESULTS

Eight hundred and forty-seven isolates from 725 patients were collected in 29 hospitals (A. fumigatus sensu stricto (n = 828) and cryptic species (n = 19)). Isolates were mostly from the lower respiratory tract (94.0%; 797/847). Only cryptic species were amphotericin B resistant. Sixty-three (7.4%) out of the 847 isolates were resistant to ≥1 azole(s). Azole resistance was higher in cryptic species than in A. fumigatus sensu stricto (95%, 18/19 vs. 5.5%, 45/828); isavuconazole was associated to the lowest number of non-wild type isolates. The dominant mechanism of resistance was the presence of TR₃₄-L98H substitutions (n = 24 out of 63). Out of the 725 patients, 48 (6.6%) carried either cryptic species (n = 14) or A. fumigatus sensu stricto (n = 34; 4.7%) resistant isolates. Aspergillus fumigatus sensu stricto harbouring either the TR₃₄-L98H (n = 19) or TR₄₆/Y121F/T289A (n = 1) mutations were detected in patients in hospitals located at 7/24 studied cities.

DISCUSSION

Of the patients, 6.6% carry azole-resistant A. fumigatus sensu lato isolates in Spain. TR₃₄-L98H is the dominant cyp51A gene substitutions, although its presence is not widespread.

Performance of the AsperGenius® PCR assay for detecting azole resistant Aspergillus fumigatus in BAL fluids from allogeneic HSCT recipients: A prospective cohort study from Essen, West Germany

In this study a commercially available multiplex real-time PCR (AsperGenius®) was evaluated for its efficacy in detecting Aspergillus fumigatus and azole resistance markers in comparison with conventional culture methods and galactomannan (GM) testing from BAL fluids in allogeneic HSCT recipients. Between January 2015 and May 2017 100 allogeneic HSCT recipients with pulmonary infiltrates and suspicion of invasive fungal infection were recruited to the study from a tertiary care center in Germany. BAL fluid was routinely assessed using the following diagnostic tests: AsperGenius® PCR assay, GM testing (cut-off: 1.0) and conventional culture. Susceptibility testing of azoles was performed by using Etest and, in case presenting elevated MICs, PCR for mutations in the cyp51A gene was carried out. Criteria of EORTC/MSG were used to classify the patients for invasive fungal disease. According to the EORTC/MSG criteria 23 patients presented with probable invasive aspergillosis (IA). Aspergillus PCR showed a sensitivity of 65% for probable IA cases. A combination of PCR and GM results in BAL displayed a sensitivity of 96% (22/23) and 100% specificity. Mutations in the cyp51A gene were detected by PCR in three cases (3/23; 13%) which were also found resistant with the culture method. In one case a Y121F/T289A mutation and in two cases a L98H were found. The combination of a commercial Aspergillus PCR assay and GM testing from BAL demonstrated a high sensitivity and specificity for diagnosing IA in allogeneic HSCT recipients. The Aspergillus PCR assay was not superior in detecting azole resistant A. fumigatus compared to culture.

Prevalence of voriconazole-resistant invasive aspergillosis and its impact on mortality in haematology patients

BACKGROUND

Increasing resistance of Aspergillus fumigatus to triazoles in high-risk populations is a concern. Its impact on mortality is not well understood, but rates from 50% to 100% have been reported.

OBJECTIVES

To determine the prevalence of voriconazole-resistant A. fumigatus invasive aspergillosis (IA) and its associated mortality in a large multicentre cohort of haematology patients with culture-positive IA.

METHODS

We performed a multicentre retrospective study, in which outcomes of culture-positive haematology patients with proven/probable IA were analysed. Patients were stratified based on the voriconazole susceptibility of their isolates (EUCAST broth microdilution test). Mycological and clinical data were compared, along with survival at 6 and 12 weeks.

RESULTS

We identified 129 A. fumigatus culture-positive proven or probable IA cases; 103 were voriconazole susceptible (79.8%) and 26 were voriconazole resistant (20.2%). All but one resistant case harboured environment-associated resistance mutations in the cyp51A gene: TR34/L98H (13 cases) and TR46/Y121F/T289A (12 cases). Triazole monotherapy was started in 75.0% (97/129) of patients. Mortality at 6 and 12 weeks was higher in voriconazole-resistant cases in all patients (42.3% versus 28.2%, P = 0.20; and 57.7% versus 36.9%, P = 0.064) and in non-ICU patients (36.4% versus 21.6%, P = 0.16; and 54.4% versus 30.7%; P = 0.035), compared with susceptible ones. ICU patient mortality at 6 and 12 weeks was very high regardless of triazole susceptibility (75.0% versus 66.7%, P = 0.99; and 75.0% versus 73.3%, P = 0.99).

CONCLUSIONS

A very high prevalence of voriconazole resistance among culture-positive IA haematology patients was observed. The overall mortality at 12 weeks was significantly higher in non-ICU patients with voriconazole-resistant IA compared with voriconazole-susceptible IA.

Voriconazole Resistance and Mortality in Invasive Aspergillosis: A Multicenter Retrospective Cohort Study

BACKGROUND

Triazole resistance is an increasing problem in invasive aspergillosis (IA). Small case series show mortality rates of 50%-100% in patients infected with a triazole-resistant Aspergillus fumigatus, but a direct comparison with triazole-susceptible IA is lacking.

METHODS

A 5-year retrospective cohort study (2011-2015) was conducted to compare mortality in patients with voriconazole-susceptible and voriconazole-resistant IA. Aspergillus fumigatus culture-positive patients were investigated to identify patients with proven, probable, and putative IA. Clinical characteristics, day 42 and day 90 mortality, triazole-resistance profiles, and antifungal treatments were investigated.

RESULTS

Of 196 patients with IA, 37 (19%) harbored a voriconazole-resistant infection. Hematological malignancy was the underlying disease in 103 (53%) patients, and 154 (79%) patients were started on voriconazole. Compared with voriconazole-susceptible cases, voriconazole resistance was associated with an increase in overall mortality of 21% on day 42 (49% vs 28%; P = .017) and 25% on day 90 (62% vs 37%; P = .0038). In non-intensive care unit patients, a 19% lower survival rate was observed in voriconazole-resistant cases at day 42 (P = .045). The mortality in patients who received appropriate initial voriconazole therapy was 24% compared with 47% in those who received inappropriate therapy (P = .016), despite switching to appropriate antifungal therapy after a median of 10 days.

CONCLUSIONS

Voriconazole resistance was associated with an excess overall mortality of 21% at day 42 and 25% at day 90 in patients with IA. A delay in the initiation of appropriate antifungal therapy was associated with increased overall mortality.

High-Frequency Direct Detection of Triazole Resistance in Aspergillus fumigatus from Patients with Chronic Pulmonary Fungal Diseases in India

Aspergillosis due to azole-resistant Aspergillus fumigatus is a worldwide problem with major therapeutic implications. In patients with invasive aspergillosis, a low yield of fungal cultures results in underestimation of azole resistance. To detect azole resistance in A. fumigatus, we applied the AsperGenius^® Resistance multiplex real-time polymerase chain reaction (PCR) assay to detect TR₃₄/L98H, and TR₄₆/T289A/Y121F mutations and the AsperGenius^® G54/M220 RUO PCR assay to detect G54/M220 mutations directly in bronchoalveolar lavage (BAL) samples of 160 patients with chronic respiratory diseases in Delhi, India. Only 23% of samples were culture-positive compared to 83% positivity by A. fumigatus species PCR highlighting concerns about the low yield of cultures. Notably, 25% of BAL samples (33/160 patients) had azole resistance-associated mutation by direct detection using PCR assay. Detection of resistance-associated mutations was found mainly in 59% and 43% patients with chronic pulmonary aspergillosis (CPA) and allergic bronchopulmonary aspergillosis (ABPA), respectively. Overall, a G54 mutation, conferring itraconazole resistance, was the predominant finding in 87.5% and 67% of patients with CPA and ABPA, respectively. In culture-negative, PCR-positive samples, we detected azole-resistant mutations in 34% of BAL samples. Azole resistance in chronic Aspergillus diseases remains undiagnosed, warranting standardization of respiratory culture and inclusion of rapid techniques to detect resistance markers directly in respiratory samples.

Management of cerebral azole-resistant Aspergillus fumigatus infection: A role for intraventricular liposomal-amphotericin B

OBJECTIVES

In the pre-azole era, central nervous system (CNS) infections with Aspergillus had a dismal outcome. Survival improved with voriconazole but CNS infections caused by azole-resistant Aspergillus fumigatus preclude its use. Intravenous liposomal-amphotericin B (L-AmB) is the preferred treatment option for azole-resistant CNS infections but has suboptimal brain concentrations.

METHODS

We describe three patients with biopsy-proven CNS aspergillosis where intraventricular L-AmB was added to systemic therapy. Two patients with azole-resistant aspergillosis and one patient with azole-susceptible CNS aspergillosis were treated with intraventricular L-AmB at a dose of 1mg weekly.

RESULTS

We describe three patients successfully treated with a combination of intravenous and intraventricular L-AmB. All three patients survived but one patient developed serious headaches, most likely not related to this treatment.

CONCLUSIONS

Intraventricular L-AmB may have a role in the treatment of therapy-refractory CNS aspergillosis when added to systemic therapy.

Blood Aspergillus PCR: The Good, the Bad, and the Ugly

Invasive Aspergillosis (IA) is one of the most common invasive fungal diseases and is accompanied by high morbidity and mortality. In order to maximize patient outcomes and survival, early and rapid diagnosis has been shown to be pivotal. Hence, diagnostic tools aiding and improving the diagnostic process are ambitiously searched for. In this context, polymerase chain reaction (PCR) may represent a potential candidate. Its additional value and benefits in diagnosis have been demonstrated and are scientifically established. Nevertheless, standardized and widespread usage is sparse because several factors influence diagnostic quality and need to be considered in order to optimize diagnostic performance and outcome. In the following review, the current role of PCR in the diagnosis of IA is explored, with special focus on the strengths and limitations of PCR in different settings.

Detecting Azole-Antifungal Resistance in Aspergillus fumigatus by Pyrosequencing

Guidelines on the diagnosis and management of Aspergillus disease recommend a multi-test approach including CT scans, culture, fungal biomarker tests, microscopy and fungal PCR. The first-line treatment of confirmed invasive aspergillosis (IA) consists of drugs in the azole family; however, the emergence of azole-resistant isolates has negatively impacted the management of IA. Failure to detect azole-resistance dramatically increases the mortality rates of azole-treated patients. Despite drug susceptibility tests not being routinely performed currently, we suggest including resistance testing whilst diagnosing Aspergillus disease. Multiple tools, including DNA sequencing, are available to screen for drug-resistant Aspergillus in clinical samples. This is particularly beneficial as a large proportion of IA samples are culture negative, consequently impeding susceptibility testing through conventional methods. Pyrosequencing is a promising in-house DNA sequencing method that can rapidly screen for genetic hotspots associated with antifungal resistance. Pyrosequencing outperforms other susceptibility testing methods due to its fast turnaround time, accurate detection of polymorphisms within critical genes, including simultaneous detection of wild type and mutated sequences, and—most importantly—it is not limited to specific genes nor fungal species. Here we review current diagnostic methods and highlight the potential of pyrosequencing to aid in a diagnosis complete with a resistance profile to improve clinical outcomes.

High-dose posaconazole for azole-resistant aspergillosis and other difficult-to-treat mould infections

Background

Oral follow‐up therapy is problematic in moulds with reduced azole‐susceptibility, such as azole‐resistant Aspergillus fumigatus infection. Currently, only intravenous liposomal amphotericin B (L‐AmB) is advocated by guidelines for the treatment of azole‐resistant aspergillosis infections. Preclinical research indicates that high‐dose posaconazole (HD‐POS) might be a feasible option provided that high drug exposure (ie POS serum through levels >3 mg/L) can be achieved and is safe.

Objectives

To describe our experience with the use of oral HD‐POS as treatment strategies for patients infected with pathogens with a POS MIC close to the clinical breakpoint.

Patients/Methods

We review evidence supporting the use of HD‐POS and describe our experience on safety and efficacy in 16 patients. In addition, we describe the adverse events (AE) observed in 25 patients with POS concentrations at the higher end of the population distribution during treatment with the licensed dose.

Results

Sixteen patients were treated intentionally with HD‐POS for voriconazole‐resistant invasive aspergillosis (7/16), mucormycosis (4/16), salvage therapy for IA (4/16) and IA at a sanctuary site (spondylodiscitis) in 1. Grade 3‐4 AEs were observed in 6, and all of them were considered at least possibly related. Grade 3‐4 AEs were observed in 5 of the 25 patients with spontaneous high POS serum through levels considered at least possibly related using Naranjo scale.

Conclusions

High‐dose posaconazole is a treatment option if strict monitoring for both exposure and for AE is possible.

Detection of the 'Big Five' mold killers of humans: Aspergillus, Fusarium, Lomentospora, Scedosporium and Mucormycetes

Fungi are an important but frequently overlooked cause of morbidity and mortality in humans. Life-threatening fungal infections mainly occur in immunocompromised patients, and are typically caused by environmental opportunists that take advantage of a weakened immune system. The filamentous fungus Aspergillus fumigatus is the most important and well-documented mold pathogen of humans, causing a number of complex respiratory diseases, including invasive pulmonary aspergillosis, an often fatal disease in patients with acute leukemia or in immunosuppressed bone marrow or solid organ transplant recipients. However, non-Aspergillus molds are increasingly reported as agents of disseminated diseases, with Fusarium, Scedosporium, Lomentospora and mucormycete species now firmly established as pathogens of immunosuppressed and immunocompetent individuals. Despite well-documented risk factors for invasive fungal diseases, and increased awareness of the risk factors for life-threatening infections, the number of deaths attributable to molds is likely to be severely underestimated driven, to a large extent, by the lack of readily accessible, cheap, and accurate tests that allow detection and differentiation of infecting species. Early diagnosis is critical to patient survival but, unlike Aspergillus diseases, where a number of CE-marked or FDA-approved biomarker tests are now available for clinical diagnosis, similar tests for fusariosis, scedosporiosis and mucormycosis remain experimental, with detection reliant on insensitive and slow culture of pathogens from invasive bronchoalveolar lavage fluid, tissue biopsy, or from blood. This review examines the ecology, epidemiology, and contemporary methods of detection of these mold pathogens, and the obstacles to diagnostic test development and translation of novel biomarkers to the clinical setting.

Recent advances and novel approaches in laboratory-based diagnostic mycology

The field of diagnostic mycology represents much more than culture and microscopy and is rapidly embracing novel techniques and strategies to help overcome the limitations of conventional approaches. Commercial molecular assays increase the applicability of PCR testing and may identify markers of antifungal resistance, which are of great clinical concern. Lateral flow assays simplify testing and turn-around time, with potential for point of care testing, while proximity ligation assays embrace the sensitivity of molecular testing with the specificity of antibody detection. The first evidence of patient risk stratification is being described and together with the era of next generation sequencing represents an exciting time in mycology.