Laboratory diagnosis of invasive aspergillosis

Fungal infections of the gastrointestinal tract in the immunocompromised host: an update

Fungal infections are one of the most significant causes of morbidity and mortality in immunocompromised patients. The incidence of invasive fungal infections, including those of the gastrointestinal tract, has increased significantly as numbers of immunocompromised patients have increased. The diagnosis of fungal infections in immunocompromised patients may be particularly problematic as these patients may present with atypical clinical features. Although Candida and Aspergillus species represent the majority of fungi diagnosed in the immunocompromised patient population, other fungi are emerging as increasingly common pathogens, and this review will focus on several important emerging fungal infections in immunocompromised patients.

Distinct innate immune phagocyte responses to Aspergillus fumigatus conidia and hyphae in zebrafish larvae

Aspergillus fumigatus is the most common filamentous fungal pathogen of immunocompromised hosts, resulting in invasive aspergillosis (IA) and high mortality rates. Innate immunity is known to be the predominant host defense against A. fumigatus; however, innate phagocyte responses to A. fumigatus in an intact host and their contributions to host survival remain unclear. Here, we describe a larval zebrafish A. fumigatus infection model amenable to real-time imaging of host-fungal interactions in live animals. Following infection with A. fumigatus, innate phagocyte populations exhibit clear preferences for different fungal morphologies: macrophages rapidly phagocytose conidia and form aggregates around hyphae, while the neutrophil response is dependent upon the presence of hyphae. Depletion of macrophages rendered host larvae susceptible to invasive disease. Moreover, a zebrafish model of human leukocyte adhesion deficiency with impaired neutrophil function also resulted in invasive disease and impaired host survival. In contrast, macrophage-deficient but not neutrophil-deficient larvae exhibited attenuated disease following challenge with a less virulent (ΔlaeA) strain of A. fumigatus, which has defects in secondary metabolite production. Taking these results together, we have established a new vertebrate model for studying innate immune responses to A. fumigatus that reveals distinct roles for neutrophils and macrophages in mediating host defense against IA.

Use and limits of (1-3)-β-d-glucan assay (Fungitell), compared to galactomannan determination (Platelia Aspergillus), for diagnosis of invasive aspergillosis

This study was undertaken to examine the performance of the Fungitell β-glucan (BG) assay, to compare it with that of the galactomannan (GM) test for the diagnosis of invasive aspergillosis (IA) in patients with hematological malignancies, and to examine the rates of false-positive BG and GM test results due to β-lactam antibiotics among sera of patients with Gram-positive or Gram-negative bacteremia and selected sera with false-positive results from the GM test. Serum samples from 105 patients with proven (n = 14) or probable (n = 91) IA, 97 hematology patients at risk for invasive fungal infections, 50 healthy blood donors, and 60 patients with bacteremia were used to study the sensitivities and specificities of the assays. The GM test was more specific than the BG assay (97% versus 82%, respectively; P = 0.0001) and the BG assay was more sensitive than the GM test (81% versus 49%, respectively; P < 0.0001) for IA diagnosis. The study of 49 separate batches of β-lactam antibiotics showed high and very similar rates of false-positive results for the GM and BG assays (29 and 33%, respectively; P = 0.82) but with an almost complete lack of concordance between the 2 assays. For patients with bacteremia, the rate of false-positive results was much higher with the BG test than with the GM test (37% versus 2%, respectively; P < 0.0001), with no significant difference between Gram-positive and Gram-negative bacteremia. In conclusion, the BG test may be useful for the diagnosis of IA because of its high sensitivity in comparison with the GM test, but the overall benefit of this assay remains limited because of its inadequate specificity and its cost.

Invasive candidiasis in intensive care unit; consensus statement from an Iranian panel of experts, July 2013

Invasive candidiasis (IC) is associated with high mortality in intensive care unit (ICU) patients. Timely diagnosis of this potentially fatal condition remains a challenge; on the other hand, the criteria for initiating empirical antifungal therapy in critically ill patients are not well defined in different patient population and ICU settings. Alongside the international guidelines, reaching regional and local consensus on diagnosis and management of IC in ICU setting is essential. This report summarizes our present status of IC management in ICU, considered by a group of Iranian experts in the fields of intensive care and infectious diseases. A round table of 17 experts was held to review the available data and discuss the optimal treatment strategies for IC in critical care setting. Comparative published data on the management of IC were analytically reviewed and the commonly asked questions about the management of IC in ICU were isolated. These questions were interactively discussed by the panel and audience responses were taken to consolidate point-to-point agreement with the panel arriving at consensus in many instances. The responses indicated that patients’ risk stratification, clinical discretion, fungal diagnostic techniques and the empirical therapy for IC are likely to save more patients. Treatment options were recommended to be based on the disease severity, prior azole exposure, and the presence of suspected azole-resistant Candida species. This report was reviewed, edited and discussed by all participants to include further evidence-based insights. The panel expects such endorsed recommendations to be soon formulated for implementation across the country.

Earlier diagnosis of invasive fusariosis with Aspergillus serum galactomannan testing

Cross-reactivity of Fusarium species with serum galactomannan antigen (GMI) test has been observed. We sought to evaluate if GMI could help to early diagnose invasive fusariosis and to monitor treatment response. We reviewed the records of all patients with invasive fusariosis between 2008 and 2012 in three Brazilian hospitals. We selected patients who had at least 1 GMI test within 2 days before or after the date of the first clinical manifestation of fusariosis, and analyzed the temporal relationship between the first positive GMI test and the date of the diagnosis of invasive fusariosis, and the kinetics of GMI in relation to patients' response to treatment. We also selected 18 controls to determine the sensitivity and specificity of the test. Among 18 patients, 15 (83%) had at least one positive GMI (median 4, range 1–15). The sensitivity and specificity of was 83% and 67%, respectively. GMI was positive before the diagnosis of invasive fusariosis in 11 of the 15 cases (73%), at a median of 10 days (range 3–39), and after the diagnosis in 4 cases. GMI became negative in 8 of the 15 patients; 3 of these 8 patients (37.5%) were alive 90 days after the diagnosis of fusariosis compared with 2 of 7 (29%) who did not normalize GMI (p = 1.0). GMI is frequently positive in invasive fusariosis, and becomes positive before diagnosis in most patients. These findings may have important implications for the choice of antifungal therapy in settings with high prevalence of invasive fusariosis.

Galactomannan antigen assay from bronchoalveolar lavage fluid in diagnosis of invasive pulmonary aspergillosis in intensive care units patients

Background:

Invasive pulmonary aspergillosis (IPA) is an important infection in critically ill patients including patients of intensive care units (ICU). Different diagnostic tools are available and since its mortality is high, it is vital to start the antifungal therapy as soon as possible. Knowing the epidemiology of this disease in each ICU and area will help to better and more rapid management of such patients. The aim of this study is to determine the frequency of IPA based on the level of galactomannan in bronchoalveolar lavage fluid in ICU of Al-Zahra hospital, Isfahan, Iran.

Materials and Methods:

This was a cross sectional study, which was conducted in Al-Zahra hospital, Isfahan, Iran, between 2010 to 2011. The study population was all the patients admitted to ICU and were suspected to have invasive Aspergillus spp pneumonia. The level of galactomannan in bronchoalveolar lavage was measured and demographic data were gathered by the questionnaire.

Results:

The frequency of IPA in this study was calculated as 2.43% while galactomannan level in bronchoalveolar lavage fluid of this patient (2.50) was significantly higher than others (0.03 ± 0.02).

Conclusion:

Larger studies are required to determine the exact frequency of IPA and the best antifungal therapy for it.

Equine pulmonary aspergillosis with encephalitic, myocardial, and renal dissemination

The cause of the death of a 16-month-old Brasileiro-de-Hipismo filly and a 3-year-old male Paint Horse with clinical manifestations of anemia and apathy from southern Brazil was investigated. These horses were maintained at the same stable; received hay as part of their diet and were submitted for routine necropsy evaluations. Significant gross findings included several nodules randomly distributed throughout the pulmonary lobes of both horses, and the kidneys, myocardium, and the frontal lobes of the cerebrum of the filly. Histopathological evaluation revealed pyogranulomatous bronchopneumonia in both horses; granulomatous interstitial nephritis, myocarditis, and encephalitis were observed in the filly. All lesions contained vasculitis and thrombosis associated with myriads of intralesional, branching, septate fungi consistent with Aspergillus spp.; intralesional fungi were more easily identified by the Grocott methenamine silver stain. Mycological culture of fresh pulmonary sections from both horses and the brain of the filly revealed pure growths of A. fumigatus. These findings confirmed the participation of A. fumigatus in the etiopathogenesis of the lesions observed in the lungs of both horses, and the cerebrum, myocardium and kidneys of the filly and might represent the first description of A. fumigatus-induced encephalitis in horses. Additionally, we believe that infection occurred during the ingestion of contaminated hay or by inhalation of spores within contaminated bedding that resulted in transient nasal mycosis, which progressed to pyogranulomatous bronchopneumonia in both horses with embolic encephalitic, myocardial, and renal dissemination of A. fumigatus occurring only in the filly.

Aspergillus collagen-like genes (acl): identification, sequence polymorphism, and assessment for PCR-based pathogen detection

The genus Aspergillus is a burden to public health due to its ubiquitous presence in the environment, its production of allergens, and wide demographic susceptibility among cystic fibrosis, asthmatic, and immunosuppressed patients. Current methods of detection of Aspergillus colonization and infection rely on lengthy morphological characterization or nonstandardized serological assays that are restricted to identifying a fungal etiology. Collagen-like genes have been shown to exhibit species-specific conservation across the noncollagenous regions as well as strain-specific polymorphism in the collagen-like regions. Here we assess the conserved region of the Aspergillus collagen-like (acl) genes and explore the application of PCR amplicon size-based discrimination among the five most common etiologic species of the Aspergillus genus, including Aspergillus fumigatus, A. flavus, A. nidulans, A. niger, and A. terreus. Genetic polymorphism and phylogenetic analysis of the aclF1 gene were additionally examined among the available strains. Furthermore, the applicability of the PCR-based assay to identification of these five species in cultures derived from sputum and bronchoalveolar fluid from 19 clinical samples was explored. Application of capillary electrophoresis on nanogels was additionally demonstrated to improve the discrimination between Aspergillus species. Overall, this study demonstrated that Aspergillus acl genes could be used as PCR targets to discriminate between clinically relevant Aspergillus species. Future studies aim to utilize the detection of Aspergillus acl genes in PCR and microfluidic applications to determine the sensitivity and specificity for the identification of Aspergillus colonization and invasive aspergillosis in immunocompromised subjects.

Pulmonary mycoses diagnosed using exfoliative cytology: infection or colonization?

OBJECTIVES

Flexible bronchoscopy with exfoliative cytology is an important tool for the diagnosis of pulmonary fungal infections. The question of colonization versus true fungal infection is of critical importance.

STUDY DESIGN

A 5-year retrospective analysis of all cases of pulmonary fungal infection diagnosed using exfoliative cytology was performed. Clinical, radiological, bronchoscopy and histopathology findings were recorded.

RESULTS

A total of 69 cases of mycoses were retrieved. The most common fungal organism identified was Aspergillus followed by Candida and Pneumocystis. Most cases of Aspergillus and Candida in cytological specimens presented as a pulmonary mass or endobronchial growth and were diagnosed as carcinomas in biopsy specimens, thus representing colonization. All cases of Pneumocystis with bilateral ground glass infiltrates and cryptococcosis with parenchymal mass lesion in radiology represented true infection. Histoplasma was identified in pleural fluid from a known case of lung carcinoma.

CONCLUSION

Aspergillus and Candida species are the most common fungal organisms. Most of these represent colonization of malignant growths. However, true fungal infections may also present as mass lesions and may masquerade malignancy clinically. Fluid cytological examination is an important diagnostic modality for pulmonary mycoses; however, it is important to correlate results with clinical, bronchoscopy and biopsy findings for accurate diagnosis and appropriate management.

Serum galactomannan assay for diagnosis of probable invasive Aspergillosis in acute leukemia and hematopoietic stem cell transplantation

Background:

Invasive aspergillosis (IA) is a leading cause of mortality in acute leukemia and hematopoietic stem cell transplantation (HSCT).

Aims:

To determine the yield of galactomannan (GM) assay for the diagnosis of probable IA, its temporal relationship with the computed tomography (CT) scans and correlation with mortality in AL and HSCT.

Patients and Methods:

Consecutive neutropenic episodes (n=150) among inpatients aged ≥15 years with AL or recipients of HSCT were prospectively evaluated over 1½ years. All patients underwent weekly serum GM assay and optical density index >0.5 for ≥2 samples was defined as positive. IA was diagnosed according to EORTC 2008 guidelines.

Results:

Of the 150 episodes enrolled, 43 (28.7%) were diagnosed with IA: possible 25 (16.7%), probable 17 (11.3%) and proven 1 (0.7%). The yield of GM assay in diagnosing probable IA was 17/42 (40.5%). In 88.2% of probable IA episodes, GM was positive before high-resolution CT at a median of 10 days (range 1-16). In the episodes with ≥2 samples tested, fatality was higher in those ≥2 values positive for GM, compared to the rest (31% vs. 13.2%, odd ratio 2.96, 95% CI 1.09-8.00; P=0.04).

Conclusions:

In AL and HSCT, GM assay could identify patients with probable IA earlier than CT chest and also predicted a higher risk of death.

Diagnosis of invasive pulmonary aspergillosis in children with bronchoalveolar lavage galactomannan

BACKGROUND

Invasive pulmonary aspergillosis (IPA) is a life-threatening complication in immunocompromised patients. Early diagnosis and therapy improves outcome. Assessment of galactomannan (GM) in bronchoalveolar lavage (BAL) fluid is a proposed tool to diagnose IPA. Little is known about the diagnostic value of BAL GM in children.

MATERIALS AND METHODS

Retrospectively, 72 bronchoscopies were analyzed for GM in patients fulfilling the host factor criteria as defined by the EORTC/MSG. A cut-off index value GM of ≥0.5 was used. Clinical data, results of chest CT-scans and BAL cultures were collected.

RESULTS

Sensitivity, specificity, PPV, and NPV of BAL GM for a diagnosis of proven and probable IPA (n = 41) were 82.4%, 87.5%, 82.4%, and 87.5% respectively. A significant relation was found for BAL GM and abnormal chest CT (P = 0.01). No significant relationship was observed between BAL Aspergillus sp. culture and chest CT (n = 47). BAL GM and serum GM correlated significantly. In 9 out of 12 patients classified as possible IPA, antifungal therapy was continued or started, despite a negative BAL GM.

CONCLUSIONS

BAL GM test had good diagnostic value in children suspected of IPA. However, the decision to continue or start antifungal therapy was mainly determined by the clinical suspicion of IPA based on chest CT-outcome, serum GM index values and failure of antibiotic therapy.

Volume dependency for culture of fungi from respiratory secretions and increased sensitivity of Aspergillus quantitative PCR

Diagnosis of aspergillosis is often difficult. We compared fungal yields from respiratory specimens using the Health Protection Agency standard culture method (BSOP57), a higher volume undiluted culture method Mycology Reference Centre Manchester (MRCM) and Aspergillus quantitative real time polymerase chain reaction (qPCR). Sputum, bronchial aspirate and bronchoalveolar lavage (BAL) samples (total 23) were collected from aspergillosis patients. One fraction of all samples was cultured using the MRCM method, one BSOP57 and one was used for qPCR. The recovery rate for fungi was significantly higher by MRCM (87%) than by BSOP57 (8.7%) from all 23 specimens. Sputum samples were 44% positive by MRCM compared to no fungi isolated (0%) by BSOP57. Bronchial aspirates were 75% positive by MRCM and 0% by BSOP57. BAL samples were positive in 20% by MRCM and 10% by BSOP57. qPCR was always more sensitive than culture (95.6%) from all samples. In general, over 100 mould colonies (81 Aspergillus fumigatus) were grown using the MRCM method compared with only one colony from BSOP57. This study provides a reference point for standardisation of respiratory sample processing in diagnostic laboratories. Culture from higher volume undiluted respiratory specimens has a much higher yield for Aspergillus than BSOP57. qPCR is much more sensitive than culture and the current UK method requires revision.

Insights into fungal communities in composts revealed by 454-pyrosequencing: implications for human health and safety

Fungal community composition in composts of lignocellulosic wastes was assessed via 454-pyrosequencing of ITS1 libraries derived from the three major composting phases. Ascomycota represented most (93%) of the 27,987 fungal sequences. A total of 102 genera, 120 species, and 222 operational taxonomic units (OTUs; >97% similarity) were identified. Thirty genera predominated (ca. 94% of the sequences), and at the species level, sequences matching Chaetomium funicola and Fusarium oxysporum were the most abundant (26 and 12%, respectively). In all composts, fungal diversity in the mature phase exceeded that of the mesophilic phase, but there was no consistent pattern in diversity changes occurring in the thermophilic phase. Fifteen species of human pathogens were identified, eight of which have not been previously identified in composts. This study demonstrated that deep sequencing can elucidate fungal community diversity in composts, and that this information can have important implications for compost use and human health.

Combined use of nonculture-based lab techniques in the diagnosis and management of critically ill patients with invasive fungal infections

Invasive fungal infections are associated with high morbidity and mortality in critically ill patients due, in part, to diagnostic difficulties in the early stages. Nonculture-based techniques such as (1,3)-β-d-glucan, galactomannan, mannan and antimannan antibodies, Candida albicans germ tube-specific antibodies or fungal DNA are required for earlier diagnosis, prognostic information and monitoring outcome. A decision-tree algorithm based on the combination of nonculture-based techniques is suggested to optimize the diagnosis and evolution of critically ill patients at risk of invasive mycoses. The use of (1,3)-β-d-glucan and blood cultures twice a week is proposed; if positive, treatment initiation is recommended alongside the performance of the nonculture-based microbiological tool depending on suspected mycoses and the availability of techniques.

Novel immunologic classification of aspergillosis in adult cystic fibrosis

BACKGROUND

Patients with cystic fibrosis (CF) demonstrate a wide range of hypersensitivity responses to Aspergillus, beyond allergic bronchopulmonary aspergillosis, which require classification.

OBJECTIVE

This study integrated 2 new methods of Aspergillus detection-sputum galactomannan (GM) and real-time PCR-alongside established serologic markers, to reclassify aspergillosis in CF.

METHODS

A total of 146 adult patients with CF had serologic tests (ImmunoCap total IgE, specific Aspergillus fumigatus IgE, and specific A fumigatus IgG), sputum real-time Aspergillus PCR, and sputum GM. Patients were classified by using latent class analysis.

RESULTS

Both RT-PCR and GM were more sensitive than culture in detecting Aspergillus in sputum (culture 37%, RT-PCR 74%, and GM 46%). Intraassay and interassay reproducibility of PCR and GM was excellent. Latent class analysis of triazole-naive patients identified a nondiseased group and 3 disease classes: class 1 (n = 49, 37.7%) represented patients with or without positive RT-PCR but no immunologic response to A fumigatus and negative GM (nondiseased); class 2 (n = 23, 17.7%) represented patients with positive RT-PCR, elevated total and specific A fumigatus IgE/IgG, and positive GM (serologic allergic bronchopulmonary aspergillosis); class 3 (n = 19, 14.6%) represented patients with or without positive RT-PCR, elevated A fumigatus IgE (not IgG), and negative GM (Aspergillus sensitized); and class 4 (n = 39, 30%) represented patients with positive RT-PCR, elevated A fumigatus IgG (not IgE), and positive GM (Aspergillus bronchitis).

CONCLUSIONS

Three distinct classes of aspergillosis in CF were identified by latent class analysis by using serologic, RT-PCR, and GM data. This novel classification will facilitate improved phenotyping, pathogenesis studies, and management evaluations.

Diagnostic methods for invasive fungal diseases in patients with hematologic malignancies

Invasive fungal disease is associated with increased morbidity and mortality in hematologic malignancy patients and hematopoietic stem cell transplant recipients. Timely recognition and treatment of invasive fungal diseases in these patients are essential and decrease mortality. However, conventional definitive diagnostic methods are difficult and time consuming. While conventional microbiological and histopathological methods are still needed for a definitive diagnosis of invasive fungal disease, new noninvasive diagnostic methods including serologic and molecular biomarkers are now available. These new diagnostic methods facilitate an early diagnosis of invasive fungal disease and allow for utilization of a pre-emptive treatment approach, which may ultimately lead to improved treatment outcomes and reduced toxicity.

Evaluation of MycAssay™ Aspergillus for diagnosis of invasive pulmonary aspergillosis in patients without hematological cancer

Methods based on real-time polymerase chain reaction (PCR) can speed up the diagnosis of invasive aspergillosis but are limited by a lack of standardization. We evaluated the commercially available MycAssay™ Aspergillus test for the diagnosis of invasive aspergillosis in patients without hematological cancer. We prospectively collected 322 lower respiratory tract samples (November 2009-January 2011) from 175 patients with lower respiratory tract infection and the following predisposing conditions: solid cancer (16.8%), cirrhosis (16.8%), corticosteroid therapy (71.7%), HIV infection (15.6%), chronic obstructive pulmonary disease (COPD, 52.6%), solid organ transplantation (kidney [1.2%], heart [3%], liver [4.6%]), or none (3.5%). Specimens were obtained when clinically indicated and analyzed in the microbiology laboratory. Aspergillus DNA was extracted and amplified by means of MycXtra® and MycAssay™ Aspergillus. Aspergillus spp. was isolated from 65 samples (31 patients). According to the European Organization for Research and Treatment of Cancer and Bulpa's criteria (for patients with COPD), 15 had probable invasive aspergillosis. MycAssay™ Aspergillus results were negative (n = 254), positive (n = 54), or indeterminate (n = 14). The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic odds ratio of the MycAssay™ (first sample/any sample) were 86.7/93, 87.6/82.4, 34.1/34.1, 92.2/100, and 48/68.75. The differences between the proportion of samples with positive PCR determinations (63%) and the proportion of samples with Aspergillus spp. isolation (75%) did not reach statistical significance (P = 0.112). The median time from sample culture to visualization of fungal growth was 3 days, compared with ∼4 hours for MycAssay™ Aspergillus PCR. MycAssay™ Aspergillus showed high sensitivity for the diagnosis of invasive aspergillosis in patients without hematological cancer. Sensitivity increased when multiple samples were used. Compared with fungal culture, PCR significantly reduced the time to diagnosis.

Bronchoalveolar lavage fluid galactomannan detection for diagnosis of invasive pulmonary aspergillosis in chronic obstructive pulmonary disease

Invasive pulmonary aspergillosis (IPA) is difficult to diagnose in chronic obstructive pulmonary disease (COPD). The aim of this study was to evaluate whether detection of galactomannan (GM) in bronchoalveolar lavage fluid (BALF) might be a useful means of making the diagnosis. Patients with COPD and new pulmonary infiltrates were enrolled. BALF was collected for culture and detection of GM. Venous blood was also sampled for GM detection. Biopsy samples were obtained whenever possible. Eleven cases of IPA were diagnosed (three proven and eight probable); 80 controls without IPA diagnosed were recruited. At a GM cut-off of 0.5, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for diagnosing IPA were 90.9, 66.3, 27.0 and 98.1% in serum, and 90.9, 62.5, 25.0 and 98.0% in BALF, respectively. At a cut-off of 1.0, the specificity, PPV and NPV in BALF increased to 95.0, 71.4 and 98.7%; the sensitivity remained 90.9%. The sensitivity in serum was substantially lower than BALF (45.5% versus 90.9%). Receiver operating characteristic curve analysis identified an optimal BALF GM cut-off value of 1.25, with a sensitivity of 90.9% and a specificity of 96.3% for diagnosing IPA. At a relatively high cut-off value, BALF GM detection is a useful tool for the diagnosis of IPA in COPD. Besides piperacillin-tazobactam and amoxicillin-clavulanate, many other factors may also cause false-positive of GM detection in patients without IPA. Further work is needed to identify factors that might lead to false-positive or false-negative results.

Utility of galactomannan antigen detection in bronchoalveolar lavage fluid in immunocompromised patients

Diagnosis of invasive pulmonary aspergillosis (IPA) is a challenging process in immunocompromised patients. Galactomannan (GM) antigen detection in bronchoalveolar lavage (BAL) fluid is a method to detect IPA with improved sensitivity over conventional studies. We sought to determine the diagnostic yield of BAL GM assay in a diverse population of immunocompromised patients. A retrospective review of 150 fiberoptic bronchoscopy (FOB) with BAL for newly diagnosed pulmonary infiltrate in immunocompromised patients was performed. Patient information, procedural details and laboratory studies were collected. BAL and serum samples were evaluated for GM using enzyme-linked immunoassay. Of 150 separate FOB with BAL, BAL GM was obtained in 143 samples. There were 31 positive BAL GM assays. In those 31 positive tests, 13 were confirmed as IPA, giving a positive predictive value of 41.9%. There was one false negative BAL GM. Of the 18 false positive BAL GM, 4 were receiving piperacillin-tazobactam and 11 were receiving an alternative beta-lactam antibiotic. BAL GM assay shows excellent sensitivity for diagnosing IPA. There was a significant number of false positive BAL GM assays and several of those patients were receiving beta-lactam antibiotics at the time of bronchoscopy.

Quantitative detection of Aspergillus spp. by real-time nucleic acid sequence-based amplification

Rapid and quantitative detection of Aspergillus from clinical samples may facilitate an early diagnosis of invasive pulmonary aspergillosis (IPA). As nucleic acid-based detection is a viable option, we demonstrate that Aspergillus burdens can be rapidly and accurately detected by a novel real-time nucleic acid assay other than qPCR by using the combination of nucleic acid sequence-based amplification (NASBA) and the molecular beacon (MB) technology. Here, we detail a real-time NASBA assay to determine quantitative Aspergillus burdens in lungs and bronchoalveolar lavage (BAL) fluids of rats with experimental IPA.

Evaluation and Management of Bacterial and Fungal Infections Occurring in Patients with a Hematological Malignancy: A 2011 Update

Patients with a hematological malignancy are a heterogeneous patient population who are afflicted with diseases that range from rapidly fatal acute leukemia to indolent lymphoma or chronic leukemia. Treatment options for these patients range from observation to hematopoietic stem cell transplantation (HSCT), but all patients are more susceptible to infection. The problem of infection is dynamic with continued shifts in pathogenic organisms and microbial susceptibilities, new treatment regimens that further diminish immune function, and patients receiving treatment who are now older and frailer. The classic patterns of immunodeficiency for patients with a hematological malignancy include: periods of profound neutropenia, increased iatrogenic risks (i.e., central vascular catheters), and cellular immune suppression that affects HSCT recipients, patients with lymphoid malignancies, and those receiving treatment with corticosteroids or agents like alemtuzumab [1–4]. Recent advances in antimicrobial drug development, new technology, clinical trial results, and further clinical experience have enhanced the database on which to make infection prophylaxis and treatment decisions. However, the practicing clinician must remember that the majority of basic infection management principles for patients who are neutropenic remain unchanged.

Evaluation of serum galactomannan detection for diagnosis of feline upper respiratory tract aspergillosis

Measurement of serum galactomannan (GM), a polysaccharide fungal cell-wall component, is a non-invasive test for early diagnosis of invasive aspergillosis in humans. Feline upper respiratory tract (URT) aspergillosis is an emerging infectious disease in cats. Diagnosis requires biopsy for procurement of tissue specimens for cytological or histological detection of fungal hyphae and for fungal culture. The aim of this study was to evaluate serum GM measurement as a non-invasive diagnostic test for URT aspergillosis in cats. A one-stage, immunoenzymatic sandwich ELISA was used to detect serum GM in 4 groups of cats; Group 1 (URT aspergillosis) - confirmed URT aspergillosis (n=13, sinonasal aspergillosis (SNA) n=6 and sino-orbital aspergillosis (SOA) n=7), Group 2 (URT other) - other URT diseases (n=15), Group 3 (β-lactam) - cats treated with β-lactam antibiotics for non-respiratory tract disease (n=14), Group 4a - healthy young cats (≤ 1 y of age, n=28), Group 4b - healthy adult cats (>1 y of age, n=16). One cat with SNA and two cats with SOA caused by an Aspergillus fumigatus-mimetic species, tested positive for serum GM. For a cut-off optical density index of 1.5, the overall sensitivity and specificity of the assay was 23% and 78% respectively. False positive results occurred in 29% of cats in Group 3 and 32% of cats in Group 4a. Specificity increased to 90% when Groups 3 and 4a were excluded from the analysis. Overall, serum GM measurement has a poor sensitivity but is a moderately specific, non-invasive screening test to rule out infection in patients with suspected feline upper respiratory tract aspergillosis.

Invasive fungal infections in solid organ transplant recipients

Invasive fungal infections are a major problem in solid organ transplant (SOT) recipients. Overall, the most common fungal infection in SOT is candidiasis, followed by aspergillosis and cryptococcosis, except in lung transplant recipients, where aspergillosis is most common. Development of invasive disease hinges on the interplay between host factors (e.g., integrity of anatomical barriers, innate and acquired immunity) and fungal factors (e.g., exposure, virulence and resistance to prophylaxis). In this article, we describe the epidemiology and clinical features of the most common fungal infections in organ transplantation. Within this context, we review recent advances in diagnostic modalities and antifungal chemotherapy, and their impact on evolving prophylaxis and treatment paradigms.

Between-laboratory quality control of automated analysis of IgG antibodies against Aspergillus fumigatus

Measurement of IgG antibodies against Aspergillus fumigatus is an important criterion for the diagnosis of aspergilloma, allergic bronchopulmonary aspergillosis, and extrinsic allergic alveolitis. In the present study, we compared IgG antibody analysis against A. fumigatus using 2 widely used automated immunochemistry systems. In a between-laboratory quality control program, good agreement was found between the results from laboratories that used the ImmunoCAP system; however, a laboratory that used the Immulite 2000 system found approx. 2-fold higher antibody levels in the quality control samples than did the ImmunoCAP system. Measurements of IgG against A. fumigatus in patient sera were significantly correlated (r(s) = 0.77, P < 0.0001). These results demonstrate that analysis of IgG antibodies against A. fumigatus with these 2 systems has reached a level of standardization that allows for direct comparison of quantitative results from different laboratories. For longitudinal analysis of IgG against A. fumigatus, reagents from the same manufacturer should be used.

Systematic review and meta-analysis of detecting galactomannan in bronchoalveolar lavage fluid for diagnosing invasive aspergillosis

BACKGROUND

Bronchoalveolar lavage (BAL) galactomannan (GM) assay has been used for diagnosing invasive aspergillosis (IA). We aimed to derive a definitive estimate of the overall accuracy of BAL-GM for diagnosing IA.

METHODS AND RESULTS

We undertook a systematic review of thirty diagnostic studies that evaluated the BAL-GM assay for diagnosing IA. PubMed and CBM (China Biological Medicine Database) databases were searched for relevant studies published in all languages up until Feb 2012. The pooled diagnostic odds ratio (DOR) and summary receiver operating characteristic (SROC) were constructed for each cutoff value. Additionally, pooled sensitivity (SEN), specificity (SPE), and positive and negative likelihood ratios (PLR and NLR, respectively) were calculated for summarizing overall test performance. Thirty studies were included in this meta-analysis. The summary estimates of pooled DOR, SEN, SPE, PLR, and NLR of the BAL-GM assay (cutoff value 0.5) for proven or probable IA were 52.7 (95% confidence interval (CI) 31.8-87.3), 0.87 (95% CI 0.79-0.92), 0.89 (95% CI 0.85-0.92), 8.0 (95% CI 5.7-11.1) and 0.15 (95% CI 0.10-0.23) respectively. The SROC was 0.94 (95% CI 0.92-0.96). Compared with cutoff value of 0.5, it has higher DOR, SPE and PLR, and similar SEN and NLR with cutoff value of 1.0, which indicated the optimal cutoff value might be 1.0. Compared with BAL-GM, serum GM has a lower SEN and higher SPE, while PCR displays a lower SEN and a similar SPE.

CONCLUSION

With the optimal cutoff value of 1.0, the BAL-GM assay has higher SEN compared to PCR and serum GM test. It is a useful adjunct in the diagnosis of proven and probable IA.

Preclinical evaluation of two 68Ga-siderophores as potential radiopharmaceuticals for Aspergillus fumigatus infection imaging

Purpose

Invasive pulmonary aspergillosis is mainly caused by Aspergillus fumigatus, and is one of the major causes of morbidity and mortality in immunocompromised patients. The mortality associated with invasive pulmonary aspergillosis remains high, mainly due to the difficulties and limitations in diagnosis. We have shown that siderophores can be labelled with ⁶⁸Ga and can be used for PET imaging of A. fumigatus infection in rats. Here we report on the further evaluation of the most promising ⁶⁸Ga-siderophore candidates, triacetylfusarinine (TAFC) and ferrioxamine E (FOXE).

Methods

Siderophores were labelled with ⁶⁸Ga using acetate buffer. Log P, protein binding and stability values were determined. Uptake by A. fumigatus was studied in vitro in cultures with high and low iron loads. In vivo biodistribution was determined in normal mice and an infection model was established using neutropenic rats inoculated with A. fumigatus. Static and dynamic μPET imaging was performed and correlated with CT images, and lung infection was evaluated ex vivo.

Results

⁶⁸Ga-siderophores were labelled with high radiochemical purity and specific activity. ⁶⁸Ga-TAFC and ⁶⁸Ga-FOXE showed high uptake by A. fumigatus in iron-deficient cultures. In normal mice, ⁶⁸Ga-TAFC and ⁶⁸Ga-FOXE showed rapid renal excretion with high metabolic stability. In the rat infection model focal lung uptake was detected by μPET with both compounds and increased with severity of the infection, correlating with abnormal CT images.

Conclusion

⁶⁸Ga-TAFC and ⁶⁸Ga-FOXE displayed excellent in vitro stability and high uptake by A. fumigatus. Both compounds showed excellent pharmacokinetics, highly selective accumulation in infected lung tissue and good correlation with severity of disease in a rat infection model, which makes them promising agents for A. fumigatus infection imaging.

Electronic supplementary material

The online version of this article (doi:10.1007/s00259-012-2110-3) contains supplementary material, which is available to authorized users.

MALDI-TOF MS proteomic phenotyping of filamentous and other fungi from clinical origin

Major changes in medical, intensive care and organ transplantation practices are drastically increasing the risk of fungal opportunistic infections. We designed and set-up a MALDI-TOF MS-based assay to identify the most isolated and emerging therapy-refractory/uncommon fungi from cystic fibrosis (CF) and immunocompromised patients. Two-hundred and thirty isolates from 10 different genera (Aspergillus, Emericella, Fusarium, Geosmithia, Neosartorya, Penicillium, Pseudallescheria, Scedosporium, Talaromyces, Fomitopsis), investigated during routine diagnostic efforts, were correlated to 22 laboratory-adapted reference MALDI-TOF MS "proteomic phenotypes". A growth time-course at 30°C on Sabouraud agar medium was performed for the 22 "phenotypes" at 48, 72, 96 and 120h points. The best peptide extraction conditions for full recovery of conidia- or asci-producing multihyphal morph structures and the highest intra- and inter-class profiling correlation were identified for the 120h point spectra dataset, from which an engineered library derived (pre-analytical phase). Fingerprinting classifiers, selected by Wilcoxon/Kruskal-Wallis algorithm, were computed by Genetic Algorithm, Support Vector Machine, Supervised Neuronal Network and Quick Classifier model construction. MS identification (ID) of clinical isolates was referred to genotyping (GT) and, retrospectively, compared to routine morphotyping (MT) IDs (analytical phase). Proteomic phenotyping is revolutionizing diagnostic mycology as fully reflecting species/morph varieties but often overcoming taxonomic hindrance.

Detection of galactomannan in bronchoalveolar lavage fluid samples of patients at risk for invasive pulmonary aspergillosis: analytical and clinical validity

Invasive pulmonary aspergillosis (IPA) is frequent and often fatal in immunosuppressed patients. Timely diagnosis of IPA improves survival but is difficult to make. We examined the analytical and clinical validity of galactomannan (GM) testing of bronchoalveolar lavage (BAL) fluid in diagnosing IPA in a mixed population by retrospectively reviewing records of 251 consecutive at-risk patients for whom BAL fluid GM testing was ordered. The performance of the enzyme immunoassay was evaluated by using a range of index cutoffs to define positivity. Three samples were associated with proven IPA, 56 were associated with probable IPA, 63 were associated with possible invasive fungal disease (IFD), and 129 were associated with no IFD. Using a BAL fluid GM index of ≥0.8 (optimal optical density [OD] index cutoff identified by a receiver operating characteristic curve), the sensitivity in diagnosing proven and probable IPA was 86.4%, and the specificity was 90.7%. At this cutoff, positive and negative predictive values were 81% and 93.6%, respectively. However, an OD index value of ≥3.0 corresponded to a 100% specificity, thus ruling the disease in, irrespective of the pretest probability. Conversely, an OD index cutoff of <0.5 corresponded to a high sensitivity, virtually always ruling the disease out. For all values in between, the posttest probability of IPA depends largely on the prevalence of disease in the at-risk population and the likelihood ratio of the OD index value. Detection of GM in BAL fluid samples of patients at risk of IPA has an excellent diagnostic accuracy provided results are interpreted in parallel with clinico-radiological findings and pretest probabilities.