Analytical and Clinical Evaluation of the PathoNostics AsperGenius Assay for Detection of Invasive Aspergillosis and Resistance to Azole Antifungal Drugs during Testing of Serum Samples

The Utility of Galactomannan and Polymerase Chain Reaction Assays in Bronchoalveolar Lavage for Diagnosis of Chronic Pulmonary Aspergillosis

The diagnosis of chronic pulmonary aspergillosis (CPA) is established by combined clinic-radio-microbiological criteria. Out of the different microbiological criteria, a positive serology for Aspergillus-specific IgG levels is the cornerstone of diagnosis. Alternatively, other microbiological evidence are sometimes sought viz., positive Aspergillus antigen (broncho-alveolar lavage fluid, i.e., BALF galactomannan ≥ 1.0), histopathological demonstration of the fungi following lung biopsy or resection, demonstration of hyaline septate hyphae in direct microscopy resembling Aspergillus spp. or its growth on a respiratory specimen. However, the exact roles of BALF- GM and the newer BALF-PCR have not been confirmed by studies till date. This study enrolled 210 patients with suspected CPA. Of the participants, 88 patients met the criteria for CPA, whereas 122 patients had an alternative diagnosis. The sensitivity-specificity of AsperGenius® PCR and "in-house" PCR were 52.27(36.69-67.54) %-33.78 (23.19-45.72) % and 36.36 (22.41-52.23) %-39.19 (28.04-51.23) % respectively. The sensitivity/specificity of BALF (> 1.0) and serum galactomannan (> 1.0) were 46.55% (33.34-60.13)/64.08% (54.03-73.3) and 29.82% (22.05-37.6)/86.84% (81.1-92.59) respectively. The optimal cut-off values for BALF-Galactomannan and serum galactomannan in diagnosing CPA were found to be 0.69 (sensitivity: 64%; specificity: 53%) and 0.458 (sensitivity: 67%; specificity: 64%) respectively. This results of this study suggests that Aspergillus PCR from BAL may not be a good "rule-in" test for diagnosing CPA. While the performances of GM in BAL and serum may be better than PCR, it should be best used in conjunction with other clinical, radiological, and other microbiological characteristics.

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).

Development of a Sensitive and Specific Novel qPCR Assay for Simultaneous Detection and Differentiation of Mucormycosis and Aspergillosis by Melting Curve Analysis

Molecular diagnostic assays can expedite the diagnosis of fungal infections, and subsequently help in early interventions and appropriate management of patients. The aim of this study was to develop a single set of primers for a real-time quantitative polymerase chain reaction (qPCR) assay to detect and identify commonly reported, clinically relevant molds i.e., Aspergillus spp, Mucorales and Fusarium spp., up to genus level by melting curve analysis. This assay was evaluated in whole blood from patients with suspected invasive aspergillosis (IA), and in tissue biopsy, bronchoalveolar lavage (BAL) fluid and other site-specific samples from patients with suspected invasive mucormycosis (IM). The limit of detection (LoD) was determined as 10 copies/μl for all three molds. The mean coefficient of variation (CV) across all sets of intra- and inter-assay data was 0.63% (ranging from 0.42 to 1.56%), showing high reproducibility of the assay. Sensitivity and specificity of the assay were 93.3 and 97.1% respectively for diagnosis of IA, and 99.29 and 83.84% respectively for diagnosis of IM. Fusarium was not detected in any of the clinical samples included and the few laboratory confirmed cases of fusariosis did not meet the inclusion criteria of the study. Hence no ROC curve or cutoff value could be generated for the same. This newly developed qPCR assay therefore appears to be a promising tool in detection of IA and IM.

Paving the Way to Overcome Antifungal Drug Resistance: Current Practices and Novel Developments for Rapid and Reliable Antifungal Susceptibility Testing

The past year has established the link between the COVID-19 pandemic and the global spread of severe fungal infections; thus, underscoring the critical need for rapid and realizable fungal disease diagnostics. While in recent years, health authorities, such as the Centers for Disease Control and Prevention, have reported the alarming emergence and spread of drug-resistant pathogenic fungi and warned against the devastating consequences, progress in the diagnosis and treatment of fungal infections is limited. Early diagnosis and patient-tailored therapy are established to be key in reducing morbidity and mortality associated with fungal (and cofungal) infections. As such, antifungal susceptibility testing (AFST) is crucial in revealing susceptibility or resistance of these pathogens and initiating correct antifungal therapy. Today, gold standard AFST methods require several days for completion, and thus this much delayed time for answer limits their clinical application. This review focuses on the advancements made in developing novel AFST techniques and discusses their implications in the context of the practiced clinical workflow. The aim of this work is to highlight the advantages and drawbacks of currently available methods and identify the main gaps hindering their progress toward clinical application.

Can We Improve Antifungal Susceptibility Testing?

Systemic antifungal agents are increasingly used for prevention or treatment of invasive fungal infections, whose prognosis remains poor. At the same time, emergence of resistant or even multi-resistant strains is of concern as the antifungal arsenal is limited. Antifungal susceptibility testing (AFST) is therefore of key importance for patient management and antifungal stewardship. Current AFST methods, including reference and commercial types, are based on growth inhibition in the presence of an antifungal, in liquid or solid media. They usually enable Minimal Inhibitory Concentrations (MIC) to be determined with direct clinical application. However, they are limited by a high turnaround time (TAT). Several innovative methods are currently under development to improve AFST. Techniques based on MALDI-TOF are promising with short TAT, but still need extensive clinical validation. Flow cytometry and computed imaging techniques detecting cellular responses to antifungal stress other than growth inhibition are also of interest. Finally, molecular detection of mutations associated with antifungal resistance is an intriguing alternative to standard AFST, already used in routine microbiology labs for detection of azole resistance in Aspergillus and even directly from samples. It is still restricted to known mutations. The development of Next Generation Sequencing (NGS) and whole-genome approaches may overcome this limitation in the near future. While promising approaches are under development, they are not perfect and the ideal AFST technique (user-friendly, reproducible, low-cost, fast and accurate) still needs to be set up routinely in clinical laboratories.

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.

Deciphering Aspergillus fumigatus cyp51A-mediated triazole resistance by pyrosequencing of respiratory specimens

Background

Infections caused by triazole drug-resistant Aspergillus fumigatus are an increasing problem. The sensitivity of standard culture is poor, abrogating susceptibility testing. Early detection of resistance can improve patient outcomes, yet tools for this purpose are limited.

Objectives

To develop and validate a pyrosequencing technique to detect resistance-conferring cyp51A polymorphisms from clinical respiratory specimens and A. fumigatus isolates.

Methods

Method validation was performed by Sanger sequencing and pyrosequencing of 50 A. fumigatus isolates with a spectrum of triazole susceptibility patterns. Then, 326 Aspergillus quantitative PCR (qPCR)-positive respiratory samples collected over a 27 month period (January 2017–March 2019) from 160 patients at the UK National Aspergillosis Centre were assessed by cyp51A pyrosequencing. The Sanger sequencing and pyrosequencing results were compared with those from high-volume culture and standard susceptibility testing.

Results

The cyp51A genotypes of the 50 isolates analysed by pyrosequencing and Sanger sequencing matched. Of the 326 Aspergillus qPCR-positive respiratory specimens, 71.2% were reported with no A. fumigatus growth. Of these, 56.9% (132/232) demonstrated a WT cyp51A genotype and 31.5% (73/232) a resistant genotype by pyrosequencing. Pyrosequencing identified the environmental TR34/L98H mutation in 18.7% (61/326) of the samples in contrast to 6.4% (21/326) pan-azole resistance detected by culture. Importantly, pyrosequencing detected resistance earlier than culture in 23.3% of specimens.

Conclusions

The pyrosequencing assay described could detect a wide range of cyp51A polymorphisms associated with triazole resistance, including those not identified by commercial assays. This method allowed prompt recognition of resistance and the selection of appropriate antifungal treatment when culture was negative.

Aspergillosis: Epidemiology, Diagnosis, and Treatment

The spectrum of disease produced by Aspergillus species ranges from allergic syndromes to chronic pulmonary conditions and invasive infections. Invasive aspergillosis is a major cause of morbidity and mortality in immunocompromised patients. Risk factors continue to evolve and include newer biological agents that target the immune system and postinfluenza infection; and it has been observed following COVID-19 infection. Diagnosis remains a challenge but non-culture-based methods are available. Antifungal resistance has emerged. Voriconazole remains the treatment of choice but isavuconazole and posaconazole have similar efficacy with less toxicity. Combination therapy is used with extensive infection and in severe immunosuppression.

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.

Recent Advances and Novel Approaches in Laboratory-Based Diagnostic Mycology

What was once just culture and microscopy the field of diagnostic mycology has significantly advanced in recent years and continues to incorporate novel assays and strategies to meet the changes in clinical demand. The emergence of widespread resistance to antifungal therapy has led to the development of a range of molecular tests that target mutations associated with phenotypic resistance, to complement classical susceptibility testing and initial applications of next-generation sequencing are being described. Lateral flow assays provide rapid results, with simplicity allowing the test to be performed outside specialist centres, potentially as point-of-care tests. Mycology has responded positively to an ever-diversifying patient population by rapidly identifying risk and developing diagnostic strategies to improve patient management. Nowadays, the diagnostic repertoire of the mycology laboratory employs classical, molecular and serological tests and should be keen to embrace diagnostic advancements that can improve diagnosis in this notoriously difficult field.

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.

Detection of Substitutions at 98th, 121st, and 289th Amino Acid Residues in Cyp51A using Cycling Probes

Azole-resistant Aspergillus fumigatus containing unique mutation(s) of cyp51A with tandem repeats in the promoter region has emerged and has become dispersed in environments worldwide. For this study, we designed primers and cycling probes to detect mutations associated with tandem repeats. Substitutions at the 293rd nucleotide (leucine or histidine at the 98th amino acid residue), at the 362nd nucleotide (tyrosine or phenylalanine at the 121st amino acid residue), and at the 865th nucleotide (threonine or alanine at the 289th amino acid residue) in cyp51A were detected using these primers and probes. These results suggest that the primer and probe sets are helpful in detecting these mutations and in differentiating the types of tandem repeats in cyp51A.

COVID-19 Associated Invasive Pulmonary Aspergillosis: Diagnostic and Therapeutic Challenges

Aspergillus co-infection in patients with severe coronavirus disease 2019 (COVID-19) pneumonia, leading to acute respiratory distress syndrome, has recently been reported. To date, 38 cases have been reported, with other cases most likely undiagnosed mainly due to a lack of clinical awareness and diagnostic screening. Importantly, there is currently no agreed case definition of COVID-19 associated invasive pulmonary aspergillosis (CAPA) that could aid in the early detection of this co-infection. Additionally, with the global emergence of triazole resistance, we emphasize the importance of antifungal susceptibility testing in order to ensure appropriate antifungal therapy. Herein is a review of 38 published CAPA cases, which highlights the diagnostic and therapeutic challenges posed by this novel fungal co-infection.

Is the COVID-19 Pandemic a Good Time to Include Aspergillus Molecular Detection to Categorize Aspergillosis in ICU Patients? A Monocentric Experience

(1) Background: The diagnosis of invasive aspergillosis (IA) in an intensive care unit (ICU) remains a challenge and the COVID-19 epidemic makes it even harder. Here, we evaluated Aspergillus PCR input to help classifying IA in SARS-CoV-2-infected patients. (2) Methods: 45 COVID-19 patients were prospectively monitored twice weekly for Aspergillus markers and anti-Aspergillus serology. We evaluated the concordance between (I) Aspergillus PCR and culture in respiratory samples, and (II) blood PCR and serum galactomannan. Patients were classified as putative/proven/colonized using AspICU algorithm and two other methods. (3) Results: The concordance of techniques applied on respiratory and blood samples was moderate (kappa = 0.58 and kappa = 0.63, respectively), with a higher sensitivity of PCR. According to AspICU, 9/45 patients were classified as putative IA. When incorporating PCR results, 15 were putative IA because they met all criteria, probably with a lack of specificity in the context of COVID-19. Using a modified AspICU algorithm, eight patients were classified as colonized and seven as putative IA. (4) Conclusion: An appreciation of the fungal burden using PCR and Aspergillus serology was added to propose a modified AspICU algorithm. This proof of concept seemed relevant, as it was in agreement with the outcome of patients, but will need validation in larger cohorts.

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.

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.

A Novel Broad Allele-Specific TaqMan Real-Time PCR Method To Detect Triazole-Resistant Strains of Aspergillus fumigatus, Even with a Very Low Percentage of Triazole-Resistant Cells Mixed with Triazole-Susceptible Cells

Invasive aspergillosis caused by triazole-resistant strains of Aspergillus fumigatus is a growing public health concern, as is the occurrence of mixed infections with triazole-resistant and -susceptible A. fumigatus strains. Therefore, it is crucial to develop robust methods to identify triazole-resistant strains of A. fumigatus, even in mixtures of triazole-resistant and -susceptible strains of A. fumigatus In this work, we developed a robust, highly selective, and broad-range allele-specific TaqMan real-time PCR platform consisting of 7 simultaneous assays that detect TR₃₄ (a 34-bp tandem repeat in the promoter region), TR₄₆, G54W (a change of G to W at position 54), G54R, L98H, Y121F, and M220I mutations in the cyp51A gene of A. fumigatus The method is based on the widely used TaqMan real-time PCR technology and combines allele-specific PCR with a blocking reagent (minor groove binder [MGB] oligonucleotide blocker) to suppress amplification of the wild-type cyp51A alleles. We used this method to detect triazole-resistant clinical strains of A. fumigatus with a variety of cyp51A gene mutations, as well as the triazole-resistant strains in mixtures of triazole-resistant and -susceptible strains of A. fumigatus The method had high efficiency and sensitivity (300 fg/well, corresponding to about 100 CFU per reaction mixture volume). It could promptly detect triazole resistance in a panel of 30 clinical strains of A. fumigatus within about 6 h. It could also detect cyp51A-associated resistance alleles, even in mixtures containing only 1% triazole-resistant A. fumigatus strains. These results suggest that this method is robustly able to detect cyp51A-associated resistance alleles even in mixtures of triazole-resistant and -susceptible strains of A. fumigatus and that it should have important clinical applications.

Invasive Aspergillosis in solid-organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated AST-IDCOP guidelines provide information on epidemiology, diagnosis, and management of Aspergillus after organ transplantation. Aspergillus is the most common invasive mold infection in solid-organ transplant (SOT) recipients, and it is the most common invasive fungal infection among lung transplant recipients. Time from transplant to diagnosis of invasive aspergillosis (IA) is variable, but most cases present within the first year post-transplant, with shortest time to onset among liver and heart transplant recipients. The overall 12-week mortality of IA in SOT exceeds 20%; prognosis is worse among those with central nervous system involvement or disseminated disease. Bronchoalveolar lavage galactomannan is preferred for the diagnosis of IA in lung and non-lung transplant recipients, in combination with other diagnostic modalities (eg, chest CT scan, culture). Voriconazole remains the drug of choice to treat IA, with isavuconazole and lipid formulations of amphotericin B regarded as alternative agents. The role of combination antifungals for primary therapy of IA remains controversial. Either universal prophylaxis or preemptive therapy is recommended in lung transplant recipients, whereas targeted prophylaxis is favored in liver and heart transplant recipients. In these guidelines, we also discuss newer antifungals and diagnostic tests, antifungal susceptibility testing, and special patient populations.

Why are so many cases of invasive aspergillosis missed?

Invasive aspergillosis (IA) incidence is increasing in several countries like France, and numerous cases are indeed missed and still only diagnosed at autopsy as evidenced by recently published data. Such missed diagnoses are obviously encountered when appropriate diagnostic tools are not available especially in low resource areas or when biologists have not been trained enough in medical mycology (i.e., microscopic examination and culture in most of those areas). Besides logistical issues, which are indeed critical, IA may not be recognized because clinicians failed to consider that risk factors are evolving with the IA burden now observed among patients with chronic lymphoid malignancies or receiving new biotherapies, with diabetes mellitus or liver cirrhosis and/or acute alcoholic hepatitis, with patients from the intensive care unit (ICU) and among patients with some predisposing primary immune deficiencies now reaching the adult's age. This is also the case for human immunodeficiency virus (HIV)-infected patients who failed to meet the classical definitions of IA. From the radiology perspective, new entities of IA have also emerged which absolutely need to be recognized especially bronchial-based-IA among allogeneic stem cell transplant recipients. Finally, from the laboratory side, contribution and limits of indirect blood biomarkers should be integrated to the clinical life in order not to miss IA cases. To conclude, several diagnostic tools should be combined and a constant dialog between laboratory and clinics is crucial to appropriately diagnose IA.

Diagnosis of aspergillosis by PCR: Clinical considerations and technical tips

Standardization of Aspergillus polymerase chain reaction (PCR) protocols has progressed, and analytical validity of blood-based assays has been formally established. It remains necessary to consider how the tests can be used in practice to maximize clinical utility. To determine the optimal diagnostic strategies and influence on patient management, several factors require consideration, including the patient population, incidence of invasive aspergillosis (and other fungal disease), and the local antifungal prescribing policy. Technical issues such as specimen type, ease of sampling, frequency of testing, access to testing centers, and time to reporting will also influence the use of PCR in clinical practice. Interpretation of all diagnostic tests is dependent on the clinical context and molecular assays are no exception, but with the proposal to incorporate Aspergillus PCR into the second revision of the consensus guidelines for defining invasive fungal disease the acceptance and understanding of molecular tests should improve.

Molecular diagnostics in medical mycology

Diagnosing fungal infections poses a number of unique problems, including a decline in expertise needed for identifying fungi, and a reduced number of instruments and assays specific for fungal identification compared to that of bacteria and viruses.These problems are exacerbated by the fact that patients with fungal infections are often immunosuppressed, which predisposes to infections from both commonly and rarely seen fungi. In this review, we discuss current and future molecular technologies used for fungal identification, and some of the problems associated with development and implementation of these technologies in today’s clinical microbiology laboratories.

Diagnosing fungal infections poses a number of unique problems. In this Review, Wickes and Wiederhold discuss molecular technologies used for fungal identification, and the problems associated with their development and implementation in today’s clinical microbiology laboratories.

The pathogenicity ofAspergillus fumigatus, drug resistance, and nanoparticle delivery

The genus Aspergillus includes fungal species that cause major health issues of significant economic importance. These microorganisms are also the culprit for production of carcinogenic aflatoxins in grain storages, contaminating crops, and economically straining the production process. Aspergillus fumigatus is a very important pathogenic species, being responsible for high human morbidity and mortality on a global basis. The prevalence of these infections in immunosuppressed individuals is on the rise, and physicians struggle with the diagnosis of these deadly pathogens. Several virulence determinants facilitate fungal invasion and evasion of the host immune response. Metabolic functions are also important for virulence and drug resistance, since they allow fungi to obtain nutrients for their own survival and growth. Following a positive diagnostic identification, mortality rates remain high due, in part, to emerging resistance to frequently used antifungal drugs. In this review, we discuss the role of the main virulence, drug target, and drug resistance determinants. We conclude with the review of new technologies being developed to treat aspergillosis. In particular, microsphere and nanoparticle delivery systems are discussed in the context of improving drug bioavailability. Aspergillus will likely continue to cause problematic infections in immunocompromised patients, so it is imperative to improve treatment options.

Overview of Commercially Available PCR Assays for the Detection of Aspergillus spp. DNA in Patient Samples

Invasive aspergillosis (IA) is a life-threatening infection in immunocompromised patients. Early diagnosis is essential to improve survival. Since the 1990s, attempts for PCR-based diagnosis of IA were made. Progress in the standardization of methods enabled the development of commercially available Aspergillus PCR assays in the last few years. Up to now, the clinical value of only a few commercial assays was investigated more extensively in large cohort studies. Most often, respiratory secretions such as bronchoalveolar lavage (BAL) were investigated, but some studies also included serum samples from high-risk patients. The data indicate that Aspergillus PCR, most likely in combination with galactomannan detection, has the potential for early and reliable diagnosis of IA including azole resistance markers. With the broad implementation of this technique in routine diagnosis and incorporation into patient care pathways, it is conceivable that an improvement in management of IA and subsequently patient outcome could occur.

Performance of Molecular Approaches for Aspergillus Detection and Azole Resistance Surveillance in Cystic Fibrosis

Aspergillus fumigatus triazole resistance is an emerging concern for treating chronically infected/colonized patients. This study sought to evaluate the performance of PCR assays to detect Aspergillus fungi together with azole resistance in sputum samples from cystic fibrosis (CF) patients. In total, 119 sputum samples from 87 CF patients were prospectively processed for Aspergillus detection by means of mycological culture and four qPCR assays, 2 in-house methods and two commercial multiplex real-time PCR assays simultaneously detecting Aspergillus and the most relevant cyp51A gene mutations (MycoGENIE^® and AsperGenius^®). Azole susceptibility of A. fumigatus isolates was assessed using Etest^® method and cyp51A gene mutation were characterized by sequencing. The overall rate of Aspergillus detection with the four qPCR assays ranged from 47.9 to 57.1%, contrasting with 42/119 (35.3%) positive cultures with A. fumigatus. The high sensitivity of PCR on sputum could then contribute to more effective grading of Aspergillus disease in CF patients. Five out of 41 isolated strains (12.2%) exhibited azole-resistant MIC patterns, three of which harbored cyp51A mutations and only 1/3 with the sequence TR₃₄/L98H. Combined with culture, PCR assay achieved high sensitivity Aspergillus screening in CF samples. However, cyp51A targeting was only moderately effective for azole resistance monitoring, while Aspergillus resistance remains of great concern.

Comparison of Two Molecular Assays for Detection and Characterization of Aspergillus fumigatus Triazole Resistance and Cyp51A Mutations in Clinical Isolates and Primary Clinical Samples of Immunocompromised Patients

In hematological patients, the incidence of invasive aspergillosis (IA) caused by azole resistant Aspergillus fumigatus (ARAf) is rising. As the diagnosis of IA is rarely based on positive culture in this group of patients, molecular detection of resistance mutations directly from clinical samples is crucial. In addition to the in-house azole resistance ARAf polymerase chain reaction (PCR) assays detecting the frequent mutation combinations TR34/L98H, TR46/Y121F/T289A, and M220 in the Aspergillus fumigatus (A. fumigatus) Cyp51A gene by subsequent DNA sequence analysis, we investigated in parallel the commercially available AsperGenius® real time PCR system in detecting the Cyp51A alterations TR34/L98H and Y121F/T289A directly from 52 clinical samples (15 biopsies, 22 bronchoalveolar lavage (BAL), 15 cerebrospinal fluid (CSF) samples) and ARAf isolates (n = 3) of immunocompromised patients. We analyzed DNA aliquots and compared both methods concerning amplification and detection of Aspergillus DNA and Cyp51A alterations. As positive control for the feasibility of our novel Y121F and T289A PCR assays, we used two A. fumigatus isolates with the TR46/Y121F/T289A mutation combination isolated from hematological patients with known Cyp51A alterations and a lung biopsy sample of a patient with acute myeloid leukemia (AML). The rate of positive ARAf PCR results plus successful sequencing using the ARAf PCR assays was 61% in biopsies, 29% in CSF, 67% in BAL samples and 100% in isolates. In comparison the amount of positive PCRs using the AsperGenius® assays was 47% in biopsies, 42% in CSF, 59% in BAL samples and 100% in isolates. Altogether 17 Cyp51A alterations were detected using our ARAf PCRs plus DNA sequencing and therefrom 10 alterations also by the AsperGenius® system. The comparative evaluation of our data revealed that our conventional PCR assays are more sensitive in detecting ARAf in BAL and biopsy samples, whereby differences were not significant. The advantage of the AsperGenius® system is the time saving aspect. We consider non-culture based molecular detection of Aspergillus triazole resistance to be of high epidemiological and clinical relevance in patients with hematological malignancies.

Diagnostic Approaches for Invasive Aspergillosis-Specific Considerations in the Pediatric Population

Invasive aspergillosis (IA) is a major cause of morbidity and mortality in children with hematological malignancies and those undergoing hematopoietic stem cell transplantation. Similar to immunocompromised adults, clinical signs, and symptoms of IA are unspecific in the pediatric patient population. As early diagnosis and prompt treatment of IA is associated with better outcome, imaging and non-invasive antigen-based such as galactomannan or ß-D-glucan and molecular biomarkers in peripheral blood may facilitate institution and choice of antifungal compounds and guide duration of therapy. In patients in whom imaging studies suggest IA or another mold infection, invasive diagnostics such as bronchoalveolar lavage and/or bioptic procedures should be considered. Here we review the current data of diagnostic approaches for IA in the pediatric setting and highlight the major differences of performance and clinical utility of the tests between children and adults.

Molecular Detection of Azole-Resistant Aspergillus fumigatus in Clinical Samples

Aspergillus diseases are often caused by Aspergillus fumigatus. Azoles are the mainstay of therapy, but the management of aspergillosis is hampered by the emergence of azole resistance. Rapid detection of azole resistance might benefit treatment outcome by early treatment modifications. However, the yield of fungal culture in invasive aspergillosis is low and susceptibility testing requires several days to be completed. To overcome the low yield of fungal cultures and slow detection of resistance, it is possible to use molecular tools directly on clinical specimens in order to rapidly detect molecular markers of azole resistance. Molecular tools to detect resistant markers in the Cyp51A gene can be expected to be less sensitive compared to molecular tools to detect Aspergillus DNA as the Cyp51A gene is a single copy gene and the target for Aspergillus DNA is often a multi-copy gene. In this mini-review, we summarize the current molecular tools for detection of azole-resistant A. fumigatus directly in clinical material. Several in-house PCR assays have been applied directly on clinical material. Furthermore, two assays are commercial available; the AsperGenius and MycoGENIE. The amplification of resistance markers was successful in 70–100% of samples that were positive for Aspergillus DNA in BAL samples using the AsperGenius assay. Despite using several samples per patient, amplification of resistance markers was only successful in 33–57% of patients with Aspergillus DNA in blood. Furthermore, several sequence based methods have been applied with the benefit of the ability to detect other Cyp51A gene alterations.

Clinical implications of globally emerging azole resistance in Aspergillus fumigatus

Aspergillus fungi are the cause of an array of diseases affecting humans, animals and plants. The triazole antifungal agents itraconazole, voriconazole, isavuconazole and posaconazole are treatment options against diseases caused by Aspergillus However, resistance to azoles has recently emerged as a new therapeutic challenge in six continents. Although de novo azole resistance occurs occasionally in patients during azole therapy, the main burden is the aquisition of resistance through the environment. In this setting, the evolution of resistance is attributed to the widespread use of azole-based fungicides. Although ubiquitously distributed, A. fumigatus is not a phytopathogen. However, agricultural fungicides deployed against plant pathogenic moulds such as Fusarium, Mycospaerella and A. flavus also show activity against A. fumigatus in the environment and exposure of non-target fungi is inevitable. Further, similarity in molecule structure between azole fungicides and antifungal drugs results in cross-resistance of A. fumigatus to medical azoles. Clinical studies have shown that two-thirds of patients with azole-resistant infections had no previous history of azole therapy and high mortality rates between 50% and 100% are reported in azole-resistant invasive aspergillosis. The resistance phenotype is associated with key mutations in the cyp51A gene, including TR₃₄/L98H, TR₅₃ and TR₄₆/Y121F/T289A resistance mechanisms. Early detection of resistance is of paramount importance and if demonstrated, either with susceptibility testing or through molecular analysis, azole monotherapy should be avoided. Liposomal amphotericin B or a combination of voriconazole and an echinocandin are recomended for azole-resistant aspergillosis.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'.

Development and Validation of a High-Resolution Melting Assay To Detect Azole Resistance in Aspergillus fumigatus

The global emergence of azole-resistant Aspergillus fumigatus strains is a growing public health concern. Different patterns of azole resistance are linked to mutations in cyp51A Therefore, accurate characterization of the mechanisms underlying azole resistance is critical to guide selection of the most appropriate antifungal agent for patients with aspergillosis. This study describes a new sequencing-free molecular screening tool for early detection of the most frequent mutations known to be associated with azole resistance in A. fumigatus PCRs targeting cyp51A mutations at positions G54, Y121, G448, and M220 and targeting different tandem repeats (TRs) in the promoter region were designed. All PCRs were performed simultaneously, using the same cycling conditions. Amplicons were then distinguished using a high-resolution melting assay. For standardization, 30 well-characterized azole-resistant A. fumigatus strains were used, yielding melting curve clusters for different resistance mechanisms for each target and allowing detection of the most frequent azole resistance mutations, i.e., G54E, G54V, G54R, G54W, Y121F, M220V, M220I, M220T, M220K, and G448S, and the tandem repeats TR₃₄, TR₄₆, and TR₅₃ Validation of the method was performed using a blind panel of 80 A. fumigatus azole-susceptible or azole-resistant strains. All strains included in the blind panel were properly classified as susceptible or resistant with the developed method. The implementation of this screening method can reduce the time needed for the detection of azole-resistant A. fumigatus isolates and therefore facilitate selection of the best antifungal therapy in patients with aspergillosis.

Molecular Tools for the Detection and Deduction of Azole Antifungal Drug Resistance Phenotypes in Aspergillus Species

The incidence of azole resistance in Aspergillus species has increased over the past years, most importantly for Aspergillus fumigatus. This is partially attributable to the global spread of only a few resistance alleles through the environment. Secondary resistance is a significant clinical concern, as invasive aspergillosis with drug-susceptible strains is already difficult to treat, and exclusion of azole-based antifungals from prophylaxis or first-line treatment of invasive aspergillosis in high-risk patients would dramatically limit drug choices, thus increasing mortality rates for immunocompromised patients. Management options for invasive aspergillosis caused by azole-resistant A. fumigatus strains were recently reevaluated by an international expert panel, which concluded that drug resistance testing of cultured isolates is highly indicated when antifungal therapy is intended. In geographical regions with a high environmental prevalence of azole-resistant strains, initial therapy should be guided by such analyses. More environmental and clinical screening studies are therefore needed to generate the local epidemiologic data if such measures are to be implemented on a sound basis. Here we propose a first workflow for evaluating isolates from screening studies, and we compile the MIC values correlating with individual amino acid substitutions in the products of cyp51 genes for interpretation of DNA sequencing data, especially in the absence of cultured isolates.

Future Research Priorities in Fungal Resistance

Improved understanding of basic mycological, pharmacological, and immunological processes has led to important advances in the diagnosis and treatment of invasive fungal infections. However, the rise of fungi that are resistant to existing antifungal agents poses a substantial threat to human health. Addressing this expanding problem is an urgent priority for the international research community. In this article, we highlight important diagnostic and therapeutic advances that address the rise of resistant fungi as well as new public health initiatives that warrant further investigation to help curb the spread of these potentially lethal organisms.

Molecular Diagnosis of Invasive Aspergillosis and Detection of Azole Resistance by a Newly Commercialized PCR Kit

Aspergillus fumigatus is the main species responsible for aspergillosis in humans. The diagnosis of aspergillosis remains difficult, and the rapid emergence of azole resistance in A. fumigatus is worrisome. The aim of this study was to validate the new MycoGENIE A. fumigatus real-time PCR kit and to evaluate its performance on clinical samples for the detection of A. fumigatus and its azole resistance. This multiplex assay detects DNA from the A. fumigatus species complex by targeting the multicopy 28S rRNA gene and specific TR₃₄ and L98H mutations in the single-copy-number cyp51A gene of A. fumigatus The specificity of cyp51A mutation detection was assessed by testing DNA samples from 25 wild-type or mutated clinical A. fumigatus isolates. Clinical validation was performed on 88 respiratory samples obtained from 62 patients and on 69 serum samples obtained from 16 patients with proven or probable aspergillosis and 13 patients without aspergillosis. The limit of detection was <1 copy for the Aspergillus 28S rRNA gene and 6 copies for the cyp51A gene harboring the TR₃₄ and L98H alterations. No cross-reactivity was detected with various fungi and bacteria. All isolates harboring the TR₃₄ and L98H mutations were accurately detected by quantitative PCR (qPCR) analysis. With respiratory samples, qPCR results showed a sensitivity and specificity of 92.9% and 90.1%, respectively, while with serum samples, the sensitivity and specificity were 100% and 84.6%, respectively. Our study demonstrated that this new real-time PCR kit enables sensitive and rapid detection of A. fumigatus DNA and azole resistance due to TR₃₄ and L98H mutations in clinical samples.

Early diagnosis of invasive mould infections and disease

Invasive mould infections (IMIs), such as invasive aspergillosis or mucormycosis, are a major cause of death in patients with haematological cancer and in patients receiving long-term immunosuppressive therapy. Early diagnosis and prompt initiation of antifungal therapy are crucial steps in the management of patients with IMI. The diagnosis of IMI remains a major challenge, with an increased spectrum of fungal pathogens and a diversity of clinical and radiological presentations within the expanding spectrum of immunocompromised hosts. Diagnosis is difficult to establish and is expressed on a scale of probability (proven, probable and possible). Imaging (CT scan), microbiological tools (direct examination, culture, PCR, fungal biomarkers) and histopathology are the pillars of the diagnostic work-up of IMI. None of the currently available diagnostic tests provides sufficient sensitivity and specificity alone, so the optimal approach relies on a combination of multiple diagnostic strategies, including imaging, fungal biomarkers (galactomannan and 1,3-β-d-glucan) and molecular tools. In recent years, the development of PCR for filamentous fungi (primarily Aspergillus or Mucorales) and the progress made in the standardization of fungal PCR technology, may lead to future advances in the field. The appropriate diagnostic approach for IMI should be individualized to each centre, taking into account the local epidemiology of IMI and the availability of diagnostic tests.

Analytical and Clinical Evaluation of the PathoNostics AsperGenius Assay for Detection of Invasive Aspergillosis and Resistance to Azole Antifungal Drugs Directly from Plasma Samples

With the proposal to include Aspergillus PCR in the revised European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) definitions for fungal disease, commercially manufactured assays may be required to provide standardization and accessibility. The PathoNostics AsperGenius assay represents one such test that has the ability to detect a range of Aspergillus species as well as azole resistance in Aspergillus fumigatus Its performance has been validated on bronchoalveolar lavage (BAL) fluid and serum specimens, but recent evidence suggests that testing of plasma may have enhanced sensitivity over that with serum. We decided to evaluate the analytical and clinical performances of the PathoNostics AsperGenius assay for testing of plasma. For the analytical evaluations, plasma was spiked with various concentrations of Aspergillus genomic DNA before extraction following international recommendations, using two automated platforms. For the clinical study, 211 samples from 10 proven/probable invasive aspergillosis (IA) and 2 possible IA cases and 27 controls were tested. The limits of detection for testing of DNA extracted using the bioMérieux EasyMag and Qiagen EZ1 extractors were 5 and 10 genomes/0.5-ml sample, respectively. In the clinical study, true positivity was significantly greater than false positivity (P < 0.0001). The sensitivity and specificity obtained using a single positive result as significant were 80% and 77.8%, respectively. If multiple samples were required to be positive, specificity was increased to 100%, albeit sensitivity was reduced to 50%. The AsperGenius assay provided good clinical performance, but the predicted improvement of testing with plasma was not seen, possibly as a result of target degradation attributed to sample storage. Prospective testing is required to determine the clinical utility of this assay, particularly for the diagnosis of azole-resistant disease.

Culture-Based Methods and Molecular Tools for Azole-Resistant Aspergillus fumigatus Detection in a Belgian University Hospital

Azole-resistant Aspergillus fumigatus is an increasing worldwide problem with major clinical implications. Surveillance is warranted to guide clinicians to provide optimal treatment to patients. To investigate azole resistance in clinical Aspergillus isolates in our institution, a Belgian university hospital, we conducted a laboratory-based surveillance between June 2015 and October 2016. Two different approaches were used: a prospective culture-based surveillance using VIPcheck on unselected A. fumigatus (n = 109 patients, including 19 patients with proven or probable invasive aspergillosis [IA]), followed by molecular detection of mutations conferring azole resistance, and a retrospective detection of azole-resistant A. fumigatus in bronchoalveolar lavage fluid using the commercially available AsperGenius PCR (n = 100 patients, including 29 patients with proven or probable IA). By VIPcheck, 25 azole-resistant A. fumigatus specimens were isolated from 14 patients (12.8%). Of these 14 patients, only 2 had proven or probable IA (10.5%). Mutations at the cyp51A gene were observed in 23 of the 25 A. fumigatus isolates; TR₃₄/L98H was the most prevalent mutation (46.7%), followed by TR₄₆/Y121F/T289A (26.7%). Twenty-seven (27%) patients were positive for the presence of Aspergillus species by AsperGenius PCR. A. fumigatus was detected by AsperGenius in 20 patients, and 3 of these patients carried cyp51A mutations. Two patients had proven or probable IA and cyp51A mutation (11.7%). Our study has shown that the detection of azole-resistant A. fumigatus in clinical isolates was a frequent finding in our institution. Hence, a rapid method for resistance detection may be useful to improve patient management. Centers that care for immunocompromised patients should perform routine surveillance to determine their local epidemiology.

Evaluating the use of PCR for diagnosing invasive aspergillosis

INTRODUCTION

Aspergillus species, primarily Aspergillus fumigatus, are still the most emerging fungal pathogens. Within recent years, novel molecular methods have been developed to improve the diagnosis of life-threatening invasive aspergillosis in high risk patients. Especially patients with malignant hematological diseases undergoing intensive chemotherapy are at risk and mortality rates are exceptionally high, in part due to difficulties and delays in establishing a microbiologic diagnosis. Early diagnosis and treatment are crucial for an adequate therapeutical management, but, however, are hardly achieved in the clinical setting because most of the current conventional diagnostic tools either lack specificity or acceptable sensitivity at the critical early phase of the infection. Areas covered: To review the clinical value, advantages and problems as well as drawbacks of molecular approaches, especially polymerase chain reaction (PCR)-based assays to detect genomic DNA of Aspergillus species in clinical samples of immunocompromised, especially hematological patients at high risk for IA, a comprehensive review of the literature was performed and expert opinion was expressed. Expert commentary: The results of numerous attempts to diagnose invasive aspergillosis by PCR-based detection of fungal genome in clinical samples highlight the potential of the PCR technique to improve early diagnosis of invasive aspergillosis in patients with hematological malignancies during intensive antineoplastic treatment, combined with imaging surveillance and serologic diagnostic tools. Further comparative validation of reliable assays in prospective multicenter studies is mandatory and urgently needed in order to establish a harmonization and standardization, so that 'gold standard assays' may be incorporated into diagnostic and therapeutic algorithms that improve the prognosis of patients with life-threatening infections caused by Aspergillus species.

Progress in the Diagnosis of Invasive Fungal Disease in Children

PURPOSE OF REVIEW

This review summarizes the fungal diagnostic measures currently available for use in paediatric patients at high risk for developing invasive fungal disease (IFD) and those suspected of having an IFD. The clinical utility of each test is described based on reported performances of individual tests in specific paediatric populations.

RECENT FINDINGS

Available studies in the paediatric population are scarce and are characterized by a huge heterogeneity in underlying diseases (e.g. different risk for IFD), different study objectives and management strategies (screening versus diagnostic) used.

SUMMARY

A final valuation of paediatric studies on fungal diagnostic tools is limited. While the galactomannan and fungal PCR assays are useful to exclude the presence of IFD, it is unclear if mannan, mannan antibodies and β-D-glucan are of benefit due to a lack of studies or validation of the cut-off, respectively. Well-designed multicentre paediatric studies are urgently needed to improve the outcome of IFD.

Emerging aspergillosis by azole-resistant Aspergillus fumigatus at an intensive care unit in the Netherlands, 2010 to 2013

The prevalence of invasive aspergillosis (IA) at the intensive care unit (ICU) is unknown and difficult to assess since IA also develops in patients lacking specific host factors. In the Netherlands, increasing azole-resistance in Aspergillus fumigatus complicates treatment of patients with IA. The aim of this study was to determine the prevalence of IA by azole-resistant A. fumigatus at the ICU among patients receiving antifungal treatment and to follow their clinical outcome and prognosis. A retrospective cohort study was conducted in a university hospital ICU from January 2010 to December 2013. From all patients who received antifungal treatment for suspected IA, relevant clinical and microbiological data were collected using a standardised questionnaire. Of 9,121 admitted ICU-patients, 136 had received antifungal treatment for suspected IA, of which 38 had a positive A. fumigatus culture. Ten of the 38 patients harboured at least one azole-resistant isolate. Resistance mechanisms consisted of alterations in the cyp51A gene, more specific TR34/L98H and TR46/T289A/Y121F. Microsatellite typing did not show clonal relatedness, though isolates from two patients were genetically related. The overall 90-day mortality of patients with IA by azole-resistant A. fumigatus and patients with suspicion of IA by azole-susceptible isolates in the ICU was 100% (10/10) vs 82% (23/28) respectively. We conclude that the changing pattern of IA in ICU patients requires appropriate criteria for recognition, diagnosis and rapid resistance tests. The increase in azole resistance rates also challenges a reconsideration of empirical antifungal therapy.

Isolation of Nucleic Acids for Fungal Diagnosis

PCR can aid in the diagnosis of invasive fungal disease (IFD). While the large number of "in-house" methodologies drives technological diversity, providing robustness, they make it difficult to identify optimal strategies, limiting standardization, and widespread acceptance. No matter how efficient, PCR utility will be limited by the quality of extracted nucleic acid. This chapter highlights benefits and limitations affecting the nucleic acid extraction process, before focusing on recent recommendations that through multicenter evaluation have provided optimal and standardized methodology.

Interspecies discrimination of A. fumigatus and siblings A. lentulus and A. felis of the Aspergillus section Fumigati using the AsperGenius® assay

The AsperGenius^® assay detects several Aspergillus species and the A. fumigatus Cyp51A mutations TR₃₄/L98H/T289A/Y121F that are associated with azole resistance. We evaluated its contribution in identifying A. lentulus and A. felis, 2 rare but intrinsically azole-resistant sibling species within the Aspergillus section Fumigati. Identification of these species with conventional culture techniques is difficult and time-consuming. The assay was tested on (i) 2 A. lentulus and A. felis strains obtained from biopsy proven invasive aspergillosis and (ii) control A. fumigatus (n=3), A. lentulus (n=6) and A. felis species complex (n=12) strains. The AsperGenius^® resistance PCR did not detect the TR₃₄ target in A. lentulus and A. felis in contrast to A. fumigatus. Melting peaks for L98H and Y121F markers differed and those of the Y121F marker were particularly suitable to discriminate the 3 species. In conclusion, the assay can be used to rapidly discriminate A. fumigatus, A. lentulus and A. felis.

Invasive Aspergillosis: Current Strategies for Diagnosis and Management

Aspergillosis remains a significant cause of morbidity and mortality in the immunocompromised population. The spectrum of disease is broad, ranging from severe and rapidly fatal infection to noninvasive disease. The diversity of patients and risk factors complicates diagnostic and therapeutic decision-making. Invasive procedures are often precluded by host status; noninvasive diagnostic tests vary in their sensitivity and specificity. Advancements in understanding the pathophysiology of invasive aspergillosis and host genetics in differential risk have also occurred. Future work may assist in therapeutic decision-making and patient prognosis. Voriconazole remains the preferred agent for treatment. Additional alternatives have emerged.

Performance evaluation of multiplex PCR including Aspergillus-not so simple!

Multiplex PCRs have been designed for including species other than Aspergillus fumigatus for the diagnosis of invasive aspergillosis, such as microarrays, liquid-phase array, and electrospray-ionization mass spectrometry (PCR/ESI MS). These methods are based on the selection of multiple primers to amplify different species with the specificity checked by hybridization to a probe or by base composition of the amplicon for the PCR/ESI MS. When testing complex samples such as respiratory specimens, some clinically relevant species can be missed. Indeed, it is impossible to design primers able to amplify all the known fungal species with the same efficiency. Therefore, the best amplified species may not be the most clinically relevant. Multiplex assays have also been proposed to detect A. fumigatus DNA and azole resistance. Since the gene responsible for azole resistance is single copy and the gene used for detection is multicopy, only the high fungal loads can be evaluated. Thus, although interesting for investigating mycobiome, the multiplex assays should be used with cautious for the diagnosis of IA or the detection of resistance. For the diagnosis of invasive aspergillosis, validated quantitative PCRs specifically targeting A. fumigatus or a limited set of species to increase sensitivity is a safer option.

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

OBJECTIVES

In patients with invasive aspergillosis (IA), fungal cultures are mostly negative. Consequently, azole resistance often remains undetected. The AsperGenius^® multiplex real-time PCR assay identifies clinically relevant Aspergillus species and four resistance-associated mutations (RAMs; TR34/L98H/T289A/Y121F) in the Cyp51A gene. This multicentre study evaluated the diagnostic performance of this assay on bronchoalveolar lavage (BAL) fluid and correlated the presence of RAMs with azole treatment failure and mortality.

METHODS

Stored BAL samples from patients with haematological diseases with suspected IA were used. BAL samples that were galactomannan/culture positive were considered positive controls for the presence of Aspergillus. Azole treatment failure and 6 week mortality were compared in patients with and without RAMs that had received ≥5 days of voriconazole monotherapy.

RESULTS

Two hundred and one patients each contributed one BAL sample, of which 88 were positive controls and 113 were negative controls. The optimal cycle threshold cut-off value for the Aspergillus species PCR was <38. With this cut-off, the PCR was positive in 74/88 positive controls. The sensitivity, specificity, positive predictive value and negative predictive value were 84%, 80%, 76% and 87%, respectively. 32/74 BAL samples were culture negative. Azole treatment failure was observed in 6/8 patients with a RAM compared with 12/45 patients without RAMs (P = 0.01). Six week mortality was 2.7 times higher in patients with RAMs (50.0% versus 18.6%; P = 0.07).

CONCLUSIONS

The AsperGenius^® assay had a good diagnostic performance on BAL and differentiated WT from Aspergillus fumigatus with RAMs, including in culture-negative BAL samples. Most importantly, detection of RAMs was associated with azole treatment failure.