Fatal disseminated Rasamsonia infection in cystic fibrosis post-lung transplantation

Fungal Colonization of the Airways of Patients with Cystic Fibrosis: the Role of the Environmental Reservoirs

Filamentous fungi frequently colonize the airways of patients with cystic fibrosis and may cause severe diseases, such as the allergic bronchopulmonary aspergillosis. The most common filamentous fungi capable to chronically colonize the respiratory tract of the patients are Aspergillus fumigatus and Scedosporium species. Defining the treatment strategy may be challenging, the number of available drugs being limited and some of the causative agents being multiresistant microorganisms. The knowledge of the fungal niches in the outdoor and indoor environment is needed for understanding the origin of the contamination of the patients. In light of the abundance of some of the causative molds in compost, agricultural and flower fields, occupational activities related to such environments should be discouraged for patients with cystic fibrosis (CF). In addition, the microbiological monitoring of their indoor environment, including analysis of air and dust on surfaces, is essential to propose preventive measures aiming to reduce the exposure to environmental molds. Nevertheless, some specific niches were also identified in the indoor environment, in relation with humidity which favors the growth of thermotolerant molds. Potted plants were reported as indoor reservoirs for Scedosporium species. Likewise, Exophiala dermatitidis may be spread in the kitchen via dishwashers. However, genotype studies are still required to establish the link between dishwashers and colonization of the airways of CF patients by this black yeast. Moreover, as nothing is known regarding the other filamentous fungi associated with CF, further studies should be conducted to identify other potential specific niches in the habitat.

Clinical Relevance of Fungi in Cystic Fibrosis

In cystic fibrosis, a new era has started with the approval and use of highly effective cystic fibrosis transport regulator (CFTR) modulator therapy. As pulmonary function is increasing and exacerbation rate significantly decreases, the current meaning of fungal pulmonary diseases is questioned. During the past couple of decades, several studies have been conducted regarding fungal colonization and infection of the airways in people with cystic fibrosis. Although Aspergillus fumigatus for filamentous fungi and Candida albicans for yeasts remain by far the most common fungal species in patients with cystic fibrosis, the pattern of fungal species associated with cystic fibrosis has considerably diversified recently. Fungi such as Scedosporium apiospermum or Exophiala dermatitidis are recognized as pathogenic in cystic fibrosis and therefore need attention in clinical settings. In this article, current definitions are stated. Important diagnostic steps are described, and their usefulness discussed. Furthermore, clinical treatment strategies and recommendations are named and evaluated. In cystic fibrosis, fungal entities can be divided into different subgroups. Besides colonization, allergic bronchopulmonary aspergillosis, bronchitis, sensitization, pneumonia, and aspergilloma can occur as a fungal disease entity. For allergic bronchopulmonary aspergillosis, bronchitis, pneumonia, and aspergilloma, clear indications for therapy exist but this is not the case for sensitization or colonization. Different pulmonary fungal disease entities in people with cystic fibrosis will continue to occur also in an era of highly effective CFTR modulator therapy. Whether the percentage will decrease or not will be the task of future evaluations in studies and registry analysis. Using the established definition for different categories of fungal diseases is recommended and should be taken into account if patients are deteriorating without responding to antibiotic treatment. Drug-drug interactions, in particular when using azoles, should be recognized and therapies need to be adjusted accordingly.

Association between Cystic Fibrosis exacerbations, lung function, T2 inflammation and microbiological colonization

BACKGROUND

The Cystic Fibrosis Foundation Patient Registry (CFFPR) reports a high prevalence of asthma (34.6%) in people with Cystic Fibrosis (PwCF). While our current understanding of this relationship is limited, a type 2 inflammatory (T2) phenotype has often been identified in CF patients.

RESEARCH QUESTION

This study aimed to evaluate the relationship between the eosinophilic CF T2 inflammatory phenotype and CF-related pulmonary outcomes and microbiological data.

STUDY DESIGN AND METHODS

We conducted a retrospective chart review of adult patients with CF (18 and older; n = 93) receiving their care at University of Virginia Medical Center adult program from January, 2013 through December, 2018. Data collected included demographic data, CFTR (CF transmembrane conductance regulator) mutation, CF comorbidities, medications, Absolute Eosinophil Counts (AEC) in cells/µL and Immunoglobulin E (IgE) levels in IU/mL.

RESULTS

Of 93 patients screened for study eligibility, 74 were included in the final analysis; 19 patients were excluded due to lack of longitudinal data across the study timeline. Lung function decline correlated with increased AEC (p < 0.001) and IgE (p < 0.001) even when adjusting for covariates: age, gender, presence of Pseudomonas spp., MRSA, other bacterial spp., Aspergillus spp., and other fungi (p < 0.001). Univariate analysis demonstrated that people with CF who experienced more than 2 exacerbations requiring hospitalizations and/or intravenous antibiotics a year were more likely to have high AEC (p = 0.018). Logistic regression showed that as AEC increases, the probability that the measurement was taken during a CF exacerbation increases (p = 0.0039). A linear mixed model showed that each additional annual exacerbation event increased on average the log IgE by 0.04. (p = 0.015). This finding remained stable in a multivariate model (p = 0.0145). When adjusted for atopy, log IgE increases as the number of exacerbation events increases (p = 0.022). There was no association between AEC and IgE and microbiological colonization.

INTERPRETATION

This study has shown that in CF patients, T2 inflammation based on serum AEC and IgE correlated with pulmonary exacerbations requiring hospitalizations and/or intravenous antibiotics, independent of bacterial airway colonization. In addition, lung function decline correlated with increased IgE and AEC. Further studies are needed to explore these correlations and potential impact on treatment.

Non-Aspergillus Hyaline Molds: A Host-Based Perspective of Emerging Pathogenic Fungi Causing Sinopulmonary Diseases

The incidence of invasive sino-pulmonary diseases due to non-Aspergillus hyaline molds is increasing due to an enlarging and evolving population of immunosuppressed hosts as well as improvements in the capabilities of molecular-based diagnostics. Herein, we review the following opportunistic pathogens known to cause sinopulmonary disease, the most common manifestation of hyalohyphomycosis: Fusarium spp., Scedosporium spp., Lomentospora prolificans, Scopulariopsis spp., Trichoderma spp., Acremonium spp., Paecilomyces variotii, Purpureocillium lilacinum, Rasamsonia argillacea species complex, Arthrographis kalrae, and Penicillium species. To facilitate an understanding of the epidemiology and clinical features of sino-pulmonary hyalohyphomycoses in the context of host immune impairment, we utilized a host-based approach encompassing the following underlying conditions: neutropenia, hematologic malignancy, hematopoietic and solid organ transplantation, chronic granulomatous disease, acquired immunodeficiency syndrome, cystic fibrosis, and healthy individuals who sustain burns, trauma, or iatrogenic exposures. We further summarize the pre-clinical and clinical data informing antifungal management for each pathogen and consider the role of adjunctive surgery and/or immunomodulatory treatments to optimize patient outcome.

Diagnosis from Tissue: Histology and Identification

The diagnosis and initiation of appropriate treatment against invasive fungal infections depend upon accurate identification of pathogens by pathologists and clinical microbiologists. Histopathology is often critical in providing diagnostic insight in patients with suspected fungal infections, and such findings are incorporated into the definitions of proven or probable disease caused by certain pathogens. Such examinations can offer provisional identifications of fungal organisms, which can help guide initial therapy while laboratory results are pending. Common etiologic agents of invasive mycoses may be recognized based on morphologic characteristics observed in tissue and biologic fluids, such as those obtained from bronchoalveolar lavage and bronchial washings. However, care should be taken in the interpretation of these findings, as there may be a false sense of the ability to correctly categorize fungal organisms to the genus or species level by morphologic features alone. Studies have demonstrated discordant results between histopathology and laboratory results due to overlapping morphologic features, morphologic mimics, and sampling errors. Thus, histopathology plays an integral role in providing a differential of potential fungal pathogens but must be combined with results from laboratory studies, including cultures, antigen tests, serology, and molecular assays, in order to improve accuracy in the identification of etiologic agents of fungal infections. Inaccurate identification of the infecting organism can lead to inappropriate antifungal therapy and possibly poor clinical outcomes.

Emerging Fungal Infections: New Species, New Names, and Antifungal Resistance

Background

Infections caused by fungi can be important causes of morbidity and mortality in certain patient populations, including those who are highly immunocompromised or critically ill. Invasive mycoses can be caused by well-known species, as well as emerging pathogens, including those that are resistant to clinically available antifungals.

Content

This review highlights emerging fungal infections, including newly described species, such as Candida auris, and those that having undergone taxonomic classification and were previously known by other names, including Blastomyces and Emergomyces species, members of the Rasamsonia argillacea species complex, Sporothrix brasiliensis, and Trichophyton indotinae. Antifungal resistance also is highlighted in several of these emerging species, as well as in the well-known opportunistic pathogen Aspergillus fumigatus. Finally, the increased recognition and importance of fungal co-infections with respiratory pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is discussed.

Summary

Both clinicians and clinical microbiology laboratories should remain vigilant regarding emerging fungal infections. These may be difficult both to diagnose and treat due to the lack of experience of clinicians and laboratory personnel with these organisms and the infections they may cause. Many of these fungal infections have been associated with poor clinical outcomes, either due to inappropriate therapy or the development of antifungal resistance.

Antifungal Susceptibility Testing: A Primer for Clinicians

Clinicians treating patients with fungal infections may turn to susceptibility testing to obtain information regarding the activity of different antifungals against a specific fungus that has been cultured. These results may then be used to make decisions regarding a patient's therapy. However, for many fungal species that are capable of causing invasive infections, clinical breakpoints have not been established. Thus, interpretations of susceptible or resistant cannot be provided by clinical laboratories, and this is especially true for many molds capable of causing severe mycoses. The purpose of this review is to provide an overview of susceptibility testing for clinicians, including the methods used to perform these assays, their limitations, how clinical breakpoints are established, and how the results may be put into context in the absence of interpretive criteria. Examples of when susceptibility testing is not warranted are also provided.

Emerging Fungal Threats in Cystic Fibrosis

In the past three decades, fungal respiratory colonization and fungal respiratory infections increasingly raised concern in cystic fibrosis (CF). Reasons for this are a better knowledge of the pathogenicity of fungi, whereby detection is sought in more and more CF centers, but also improvement of detection methods. However, differences in fungal detection rates within and between geographical regions exist and indicate the need for standardization of mycological examination of respiratory secretions. The still existing lack of standardization also complicates the assessment of fungal pathogenicity, relevance of fungal detection and risk factors for fungal infections. Nevertheless, numerous studies have now been conducted on differences in detection methods, epidemiology, risk factors, pathogenicity and therapy of fungal diseases in CF. Meanwhile, some research groups now have classified fungal disease entities in CF and developed diagnostic criteria as well as therapeutic guidelines.The following review presents an overview on fungal species relevant in CF. Cultural detection methods with their respective success rates as well as susceptibility testing will be presented, and the problem of increasing azole resistance in Aspergillus fumigatus will be highlighted. Next, current data and conflicting evidence on the epidemiology and risk factors for fungal diseases in patients with CF will be discussed. Finally, an overview of fungal disease entities in CF with their current definitions, diagnostic criteria and therapeutic options will be presented.

Evaluation of ID Fungi Plates Medium for Identification of Molds by MALDI Biotyper

MALDI-TOF mass spectrometry (MS) identification of pathogenic filamentous fungi is often impaired by difficulties in harvesting hyphae embedded in the medium and long extraction protocols. The ID Fungi Plate (IDFP) is a novel culture method developed to address such difficulties and improve the identification of filamentous fungi by MALDI-TOF MS. We cultured 64 strains and 11 clinical samples on IDFP, Sabouraud agar-chloramphenicol (SAB), and ChromID Candida agar (CAN2). We then compared the three media for growth, ease of harvest, amount of material picked, and MALDI-TOF identification scores after either rapid direct transfer (DT) or a long ethanol-acetonitrile (EA) extraction protocol. Antifungal susceptibility testing and microscopic morphology after subculture on SAB and IDFP were also compared for ten molds. Growth rates and morphological aspects were similar for the three media. With IDFP, harvesting of fungal material for the extraction procedure was rapid and easy in 92.4% of cases, whereas it was tedious on SAB or CAN2 in 65.2% and 80.3% of cases, respectively. The proportion of scores above 1.7 (defined as acceptable identification) were comparable for both extraction protocols using IDFP (P = 0.256). Moreover, rates of acceptable identification after DT performed on IDFP (93.9%) were significantly higher than those obtained after EA extraction with SAB (69.7%) or CAN2 (71.2%) (P = <0.001 and P = 0.001, respectively). Morphological aspects and antifungal susceptibility testing were similar between IDFP and SAB. IDFP is a culture plate that facilitates and improves the identification of filamentous fungi, allowing accurate routine identification of molds with MALDI-TOF-MS using a rapid-extraction protocol.

Advances in understanding and managing Scedosporium respiratory infections in patients with cystic fibrosis

Introduction: Considered for a long time to be exclusively responsible for chronic localized infections, fungi of the genus Scedosporium have recently received a renewed interest because of their recognition as common colonizing agents of the respiratory tract of patients with cystic fibrosis, and of the description of severe disseminated infections in patients undergoing lung transplantation. Recently, several studies have been carried out on these opportunistic pathogens, which led to some advances in the understanding of their pathogenic mechanisms and in the biological diagnosis of the airway colonization/respiratory infections caused by these fungi.Areas covered: From a bibliographic search on the Pubmed database, we summarize the current knowledge about the taxonomy of Scedosporium species, the epidemiology of these fungi and their pathogenic mechanisms, and present the improvements in the detection of the airway colonization and diagnosis of Scedosporium respiratory infections, the difficulties in their therapeutic management, and the antifungal drugs in development.Expert opinion: As described in this review, many advances have been made regarding the taxonomy and ecology of Scedosporium species or the molecular determinants of their pathogenicity, but also in the management of Scedosporium infections, particularly by improving the biological diagnostic and publishing evidence for the efficacy of combined therapy.

Risk factors and mortality in invasive Rasamsonia spp. infection: Analysis of cases in the FungiScope® registry and from the literature

BACKGROUND

The new Rasamsonia spp. complex can develop invasive infection in immunosuppression or chronic pulmonary disease. It has potential to be misidentified as other genera due to morphological similarities. Nowadays, there is a gap of knowledge on this fungi.

OBJECTIVES

To provide knowledge base of risk factors and therapeutic decisions in invasive Rasamsonia spp. complex infection.

PATIENTS/METHODS

Cases of invasive infection due to Rasamsonia spp. (formerly Geosmithia/Penicillium spp.) from FungiScope^® registry and all reported cases from a literature were included.

RESULTS

We identified 23 invasive infections due to Rasamsonia spp., six (26.1%) in the FungiScope^® registry. Main risk factors were chronic granulomatous disease (n = 12, 52.2%), immunosuppressive treatment (n = 10, 43.5%), haematopoietic stem cell transplantation (n = 7, 30.4%), graft-versus-host disease and major surgery (n = 4, 17.4%, each). Predominantly affected organs were the lungs (n = 21, 91.3%), disease disseminated in seven cases (30.4%). Fungal misidentification occurred in 47.8% (n = 11), and sequencing was used in 69.6% of the patients (n = 16) to diagnose. Breakthrough infection occurred in 13 patients (56.5%). All patients received antifungal treatment, mostly posaconazole (n = 11), caspofungin (n = 10) or voriconazole (n = 9). Combination therapy was administered in 13 patients (56.5%). Susceptibility testing showed high minimum inhibitory concentrations for azoles and amphotericin B, but not for echinocandins. No preferable treatment influencing favourable outcome was identified. Overall mortality was 39% (n = 9).

CONCLUSION

Rasamsonia spp. are emerging fungi causing life-threatening infections, especially in immunocompromised and critically ill patients. Mortality is high. Treatment is challenging and clinicians dealing with this patient population should become aware of this infection constituting a medical emergency.

Respiratory Fungal Diseases in Adult Patients With Cystic Fibrosis

Clinical manifestations of respiratory fungal diseases in adult cystic fibrosis (CF) patients are very heterogeneous, ranging from asymptomatic colonization to chronic infections, allergic disorders, or invasive diseases in immunosuppressed CF patients after lung transplantation. In this narrative review, mainly addressed to clinicians without expertise in CF who may nonetheless encounter adult CF patients presenting with acute and chronic respiratory syndromes, we briefly summarize the most representative clinical aspects of respiratory fungal diseases in adult CF patients.

Rasamsonia sp: An emerging infection amongst chronic granulomatous disease patients. A case of disseminated infection by a putatively novel Rasamsonia argillacea species complex involving the heart

Chronic granulomatous disease (CGD) is a heterogeneous condition due to defects in NADPH oxidase characterized by granuloma formation and increased susceptibility to invasive infections, in particular moulds. The use of broad-spectrum, mould-active antifungal prophylaxis has improved mortality. However rare resistant moulds have emerged as important pathogens. Diagnosis of these rare fungi requires molecular techniques, and treatment data are limited. Herein, we present a case of with disseminated Rasamsonia infection involving the heart.

From the Clinical Mycology Laboratory: New Species and Changes in Fungal Taxonomy and Nomenclature

Fungal taxonomy is the branch of mycology by which we classify and group fungi based on similarities or differences. Historically, this was done by morphologic characteristics and other phenotypic traits. However, with the advent of the molecular age in mycology, phylogenetic analysis based on DNA sequences has replaced these classic means for grouping related species. This, along with the abandonment of the dual nomenclature system, has led to a marked increase in the number of new species and reclassification of known species. Although these evaluations and changes are necessary to move the field forward, there is concern among medical mycologists that the rapidity by which fungal nomenclature is changing could cause confusion in the clinical literature. Thus, there is a proposal to allow medical mycologists to adopt changes in taxonomy and nomenclature at a slower pace. In this review, changes in the taxonomy and nomenclature of medically relevant fungi will be discussed along with the impact this may have on clinicians and patient care. Specific examples of changes and current controversies will also be given.

Developing collaborative works for faster progress on fungal respiratory infections in cystic fibrosis

Cystic fibrosis (CF) is the major genetic inherited disease in Caucasian populations. The respiratory tract of CF patients displays a sticky viscous mucus, which allows for the entrapment of airborne bacteria and fungal spores and provides a suitable environment for growth of microorganisms, including numerous yeast and filamentous fungal species. As a consequence, respiratory infections are the major cause of morbidity and mortality in this clinical context. Although bacteria remain the most common agents of these infections, fungal respiratory infections have emerged as an important cause of disease. Therefore, the International Society for Human and Animal Mycology (ISHAM) has launched a working group on Fungal respiratory infections in Cystic Fibrosis (Fri-CF) in October 2006, which was subsequently approved by the European Confederation of Medical Mycology (ECMM). Meetings of this working group, comprising both clinicians and mycologists involved in the follow-up of CF patients, as well as basic scientists interested in the fungal species involved, provided the opportunity to initiate collaborative works aimed to improve our knowledge on these infections to assist clinicians in patient management. The current review highlights the outcomes of some of these collaborative works in clinical surveillance, pathogenesis and treatment, giving special emphasis to standardization of culture procedures, improvement of species identification methods including the development of nonculture-based diagnostic methods, microbiome studies and identification of new biological markers, and the description of genotyping studies aiming to differentiate transient carriage and chronic colonization of the airways. The review also reports on the breakthrough in sequencing the genomes of the main Scedosporium species as basis for a better understanding of the pathogenic mechanisms of these fungi, and discusses treatment options of infections caused by multidrug resistant microorganisms, such as Scedosporium and Lomentospora species and members of the Rasamsonia argillacea species complex.

Cystic Fibrosis: Emerging Understanding and Therapies

Cystic fibrosis (CF) is the most common life-limiting genetic disease in Caucasian patients. Continued advances have led to improved survival, and adults with CF now outnumber children. As our understanding of the disease improves, new therapies have emerged that improve the basic defect, enabling patient-specific treatment and improved outcomes. However, recurrent exacerbations continue to lead to morbidity and mortality, and new pathogens have been identified that may lead to worse outcomes. In addition, new complications, such as CF-related diabetes and increased risk of gastrointestinal cancers, are creating new challenges in management. For patients with end-stage disease, lung transplantation has remained one of the few treatment options, but challenges in identifying the most appropriate patients remain.

Unmet needs in cystic fibrosis: the next steps in improving outcomes

INTRODUCTION

Cystic fibrosis (CF) outcomes and survival have improved over the last century primarily due to advancements in antibiotics, nutritional, and pulmonary therapies. Reviewed here are the significant unmet needs that exist for individuals with CF. Areas covered: With the recent development of medications that address the underlying defect in the CF protein, there is hope that there will be continued improvement in CF outcomes. However, there remains a need to prevent or stop progression of CF-related complications, as the CF protein is important to several body systems. As end stage lung disease is the primary cause of mortality in CF, a need exists for advancements in pulmonary therapies to reduce time burden, identification of best practices for the treatment of pulmonary exacerbations, further development of anti-infective and anti-inflammatory therapies, and appropriately timed referral for lung transplantation at end-stage lung disease. Extra-pulmonary complications are increasingly recognized and better understanding of such problems as CF related liver disease is needed. Expert commentary: While CFTR modulators are available for the majority of CF patients, there remains a need for effective therapies to address infection, inflammation, irreversible lung disease, and extrapulmonary complications of CF.

Airway persistence by the emerging multi-azole-resistant Rasamsonia argillacea complex in cystic fibrosis

Infections caused by Rasamsonia argillacea complex have been reported in various clinical settings. Cystic fibrosis (CF) is one of the main underlying conditions. An observational cohort study of CF patients with Rasamsonia in respiratory samples was conducted. Eight isolates from 6 patients were identified as R. argillacea complex and tested for antifungal susceptibility. All isolates had high MICs to voriconazole and posaconazole and low MECs to echinocandins. Four patients experienced lung function decline in the year preceding first Rasamsonia isolation. This continued in the year following first isolation in 3 out of 4 cases. Antifungal therapy was initiated in 2 patients, to which only one exhibited a clinical response. Three out of 6 patients died within 3 years of isolating Rasamsonia. Genotyping suggests that similar genotypes of Rasamsonia can persist in CF airways. Consistent with other fungi in CF, the clinical impact of airway colonisation by Rasamsonia is variable. In certain patients, Rasamsonia may be able to drive clinical decline. In others, though a clear impact on lung function may be difficult to determine, the appearance of Rasamsonia acts as a marker of disease severity. In others it does not appear to have an obvious clinical impact on disease progression.

Fungus-Specific CD4 T Cells as Specific Sensors for Identification of Pulmonary Fungal Infections

Patients with cystic fibrosis (CF) suffer from chronic lung infections, caused by bacterial, viral or fungal pathogens, which determine morbidity and mortality. The contribution of individual pathogens to chronic disease and acute lung exacerbations is often difficult to determine due to the complex composition of the lung microbiome in CF. In particular, the relevance of fungal pathogens in CF airways remains poorly understood due to limitations of current diagnostics to identify the presence of fungal pathogens and to resolve the individual host-pathogen interaction status. T-lymphocytes play an essential role in host defense against pathogens, but also in inappropriate immune reactions such as allergies. They have the capacity to specifically recognize and discriminate the different pathogens and orchestrate a diverse array of effector functions. Thus, the analysis of the fungus-specific T cell status of an individual can in principle provide detailed information about the identity of the fungal pathogen(s) encountered and the actual fungus-host interaction status. This may allow to classify patients, according to appropriate (protective) or inappropriate (pathology-associated) immune reactions against individual fungal pathogens. However, T cell-based diagnostics are currently not part of the clinical routine. The identification and characterization of fungus-specific T cells in health and disease for diagnostic purposes are associated with significant challenges. Recent technological developments in the field of fungus-specific T helper cell detection provide new insights in the host T cell-fungus interaction. In this review, we will discuss basic principles and the potential of T cell-based diagnostics, as well as the perspectives and further needs for use of T cells for improved clinical diagnostics of fungal diseases.

Systemic Rasamsonia piperina infection in a German shepherd cross dog

Introduction. Infection with the Rasamsonia argillacea species complex represents an emerging problem in human and veterinary medicine with systemic mycoses presenting with significant clinical complications and being a cause of death.

Case presentation. In this report, a case of systemic Rasamsonia piperina infection discovered in a 3-year-old male neutered, German shepherd cross dog is described together with the clinical presentation, the course of the disease and diagnosis. This report describes the first case of veterinary mycosis due to R. piperina in Europe and the first case in humans or animals in the UK.

Conclusion. Although seemingly rare, R. argillacea species complex infection should be a differential diagnosis for dogs, especially German shepherds with the described presenting signs, and radiographic and ultrasonographic findings.

Fungal Pathogens in CF Airways: Leave or Treat?

Chronic airway infection plays an essential role in the progress of cystic fibrosis (CF) lung disease. In the past decades, mainly bacterial pathogens, such as Pseudomonas aeruginosa, have been the focus of researchers and clinicians. However, fungi are frequently detected in CF airways and there is an increasing body of evidence that fungal pathogens might play a role in CF lung disease. Several studies have shown an association of fungi, particularly Aspergillus fumigatus and Candida albicans, with the course of lung disease in CF patients. Mechanistically, in vitro and in vivo studies suggest that an impaired immune response to fungal pathogens in CF airways renders them more susceptible to fungi. However, it remains elusive whether fungi are actively involved in CF lung disease pathologies or whether they rather reflect a dysregulated airway colonization and act as microbial bystanders. A key issue for dissecting the role of fungi in CF lung disease is the distinction of dynamic fungal-host interaction entities, namely colonization, sensitization or infection. This review summarizes key findings on pathophysiological mechanisms and the clinical impact of fungi in CF lung disease.

Challenges in Laboratory Detection of Fungal Pathogens in the Airways of Cystic Fibrosis Patients

Study of the clinical significance of fungal colonization/infection in the airways of cystic fibrosis (CF) patients, especially by filamentous fungi, is challenged by the absence of standardized methodology for the detection and identification of an ever-broadening range of fungal pathogens. Culture-based methods remain the cornerstone diagnostic approaches, but current methods used in many clinical laboratories are insensitive and unstandardized, rendering comparative studies unfeasible. Guidelines for standardized processing of respiratory specimens and for their culture are urgently needed and should include recommendations for specific processing procedures, inoculum density, culture media, incubation temperature and duration of culture. Molecular techniques to detect fungi directly from clinical specimens include panfungal PCR assays, multiplex or pathogen-directed assays, real-time PCR, isothermal methods and probe-based assays. In general, these are used to complement culture. Fungal identification by DNA sequencing methods is often required to identify cultured isolates, but matrix-assisted laser desorption/ionization time-of-flight mass spectrometry is increasingly used as an alternative to DNA sequencing. Genotyping of isolates is undertaken to investigate relatedness between isolates, to pinpoint the infection source and to study the population structure. Methods range from PCR fingerprinting and amplified fragment length polymorphism analysis, to short tandem repeat typing, multilocus sequencing typing (MLST) and whole genome sequencing (WGS). MLST is the current preferred method, whilst WGS offers best case resolution but currently is understudied.