Clinical evaluation of Aspergillus-PCR for detection of invasive aspergillosis in immunosuppressed patients

Successful treatment of vertebral osteomyelitis due to Aspergillus flavus in an immunocompetent patient

Aspergillus osteomyelitis (AO) is a rare and often lethal opportunistic infection in predominantly immunocompromised patients. Treatment has shifted from amphotericin therapy to voriconazole monotherapy due to increased effectiveness and less toxicity. We report a case of an immunocompetent woman with vertebral osteomyelitis due to Aspergillus flavus who was successfully treated with surgery (requiring hardware implantation) and monotherapy posaconazole (following intolerance and hepatitis due to voriconazole). She remained well at follow-up post cessation of 12 months of antifungal therapy. We provide an updated literature review examining the role of azole monotherapy as the gold standard of treatment for AO.

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

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

Molecular and nonmolecular diagnostic methods for invasive fungal infections

Invasive fungal infections constitute a serious threat to an ever-growing population of immunocompromised individuals and other individuals at risk. Traditional diagnostic methods, such as histopathology and culture, which are still considered the gold standards, have low sensitivity, which underscores the need for the development of new means of detecting fungal infectious agents. Indeed, novel serologic and molecular techniques have been developed and are currently under clinical evaluation. Tests like the galactomannan antigen test for aspergillosis and the β-glucan test for invasive Candida spp. and molds, as well as other antigen and antibody tests, for Cryptococcus spp., Pneumocystis spp., and dimorphic fungi, have already been established as important diagnostic approaches and are implemented in routine clinical practice. On the other hand, PCR and other molecular approaches, such as matrix-assisted laser desorption ionization (MALDI) and fluorescence in situ hybridization (FISH), have proved promising in clinical trials but still need to undergo standardization before their clinical use can become widespread. The purpose of this review is to highlight the different diagnostic approaches that are currently utilized or under development for invasive fungal infections and to identify their performance characteristics and the challenges associated with their use.

Fungal infections associated with long-term mechanical circulatory support-diagnosis and management

Left ventricular assist devices (LVADs) are increasingly used as a treatment option for advanced heart failure. Fungal infections present a serious concern given the high association with major adverse events including death in this group of patients. The objective of this review is to summarize the incidence, risk factors, method for diagnosis, complication rate, and outcomes in patients with VADs who develop fungal infections.

Fungal diagnosis: how do we do it and can we do better?

BACKGROUND

Morbidity and mortality remain high for patients with invasive fungal infections (IFIs) despite an increasing number of antifungals and other treatments. Many studies indicate that delayed or inaccurate diagnosis and treatment are major causes of poor outcomes in patients with IFIs.

OBJECTIVE

The aim of the current paper is to provide a review of traditional and newer approaches to the diagnosis of IFIs, with a particular focus on invasive candidiasis (IC) and aspergillosis (IA). Recent studies from the author's institution are highlighted, along with an advancement in cryptococcal meningitis diagnosis that should improve the care of AIDS and its opportunistic infection in many developing countries.

FINDINGS

Currently available tools for the diagnosis of IFIs include traditional methods like histopathology, culture, and radiology, and newer antigen- and PCR-based diagnostic assays. Attempts have also been made to predict IFIs based on colonization or other factors, including genetic polymorphisms impacting IFI susceptibility in high-risk patients. Biopsy with histopathologic analysis is often not possible in patients suspected of pulmonary aspergillosis due to increased bleeding risk, and blood cultures for IC, IA, or other IFIs are hindered by poor sensitivity and slow turnaround time which delays diagnosis. Radiology is often used to predict IFI but suffers from inability to differentiate certain pathogens and does not generally provide certainty of IFI diagnosis. Newer antigen-based diagnostics for early diagnosis include the β-glucan assay for IFIs, galactomannan assay for IA, and a recent variation on the traditional cryptococcal antigen (CRAG) test with a Lateral Flow Assay for invasive cryptococcosis. PCR-based diagnostics represent additional tools with high sensitivity for the rapid diagnosis of IFIs, although better standardization of these methods is still required for their routine clinical use.

CONCLUSION

Better understanding of the strengths and weaknesses of currently available diagnostic tools, and further devising linked strategies to best implement them either alone or in combination, would greatly improve early and accurate diagnosis of IFIs and improve their successful management.

Biopsy procedures for molecular tissue diagnosis of invasive fungal infections

The incidence of invasive fungal infections (IFI) has increased substantially and the epidemiology has changed dramatically in recent years. Candida albicans is still most important, but non-albicans species, Aspergillus species, Glomeromycota (formerly Zygomycetes) and Fusarium species are an increasing cause of IFIs. Due to this growing diversity, the identification of the causative organism to genus and species level is important to perform best and adequate treatment. The early, sensitive and specific detection of IFIs remains challenging and current conventional methods are limited. The golden standard for the definite diagnosis of proven pulmonary infection remains either histopathologic, cytopathologic or direct tissue examination. Invasive procedures are necessary to obtain reliable specimens and biopsies may be taken percutaneously, bronchoscopically, via open surgery or via video-assisted thorascopic surgery. Molecular methods, like PCR or in situ hybridization, are a promising diagnostic tool for rapid and reliable species identification and should be performed in addition to microscopic examination and culture to increase the sensitivity for the diagnosis of IFI. Combining culture, microscopy, serology, and PCR in lung tissues and/or bronchial samples will increase the diagnostic yield by 99%. Here, we give an overview of biopsy procedures for molecular tissue diagnosis of IFI.

Successful management of postpneumonectomy Aspergillus pleural empyema by combined surgical and anti-fungal treatment with voriconazole and caspofungin

Aspergillus pleural empyema is a rare but often fatal infection complicating thoracic surgery. Three men and one woman aged 23-47 years were diagnosed with Aspergillus pleural empyema after lung resection. Underlying diseases were lung cancer (n = 2), Hodgkin's disease (n = 1) and thoracic trauma (n = 1). The treatment protocol consisted of systemic anti-fungal treatment with caspofungin and voriconazole, intrapleural application of amphotericin B and surgical debridement with secondary closure of the leaking bronchial stump. Two patients with chronic Aspergillus pleural empyema had been pretreated with itraconazole and/or amphotericin B. Two patients were treated with a thoracostoma. Two patients had undergone pneumonectomy for previously diagnosed pulmonary aspergillosis. Caspofungin was given for 13-60 days, Voriconazole for up to 100 days. Surgical debridement was performed in all cases and in two cases the created thoracostoma was closed during a second surgical procedure. Aspergillus PCR using blood samples, bronchoalveolar lavage or aspiration fluid was used for monitoring. All four patients had complete clinical and microbiological remission. Our case series shows promising results and underscores the importance of a combined therapeutic approach for Aspergillus pleural empyema consisting of anti-fungal treatment and surgery. Voriconazole and caspofungin seem to be a suitable combination for this infection.

Aspergillus PCR formidable challenges and progress

Invasive aspergillosis (IA) is an important cause of morbidity and mortality in immuno-compromised patients, with an incidence of 4-10%, and with a mortality rate of 80-90%, such as in allogeneic stem cell transplant recipients. Conventional diagnostic tests, like blood culture, are not useful in the diagnosis of Aspergillus spp. fungemia. Furthermore, non-culture based techniques that have been used in the past have lacked sensitivity and specificity in immunocompromised patients. New rapid methods which can detect IA early in the course of disease with high sensitivity and specificity are needed since treating these infections at an early stage is often essential for favourable outcomes. In this regard, the polymerase chain reaction (PCR) offers great promise for the rapid diagnosis of fungal infections, including detection of fungi that do not grow in blood cultures such as Aspergillus spp. At Karolinska University Hospital we have established a diagnostic assay, using a combination of a manual extraction and a robot for automated extraction of Candida and Aspergillus DNA, together with real-time PCR. To asses its clinical applicability, a large number of samples from patients with suspected invasive fungal infection have been analyzed with real time PCR. Data will be presented with focus on Aspergillus R-T PCR results in immunocompromised patients. A range of different PCR assays have been developed, targeting different gene regions and including a variety of amplicon detection methods. These molecular assays provide high potential in terms of sensitivity and specificity, but vary widely in their feasibility and have not, until now, been standardized. Despite this progress, there are certain questions to be addressed using these assays, such as the frequency of prospective sampling, as well as the number of positive results of a PCR assay required to initiate antifungal therapy. Furthermore, there are only a few standardized assays that are commercially available. This particular challenge will be addressed by the Working Group 'EAPCRI' (European Aspergillus PCR Initiative) under the auspices of ISHAM. Twenty-four centres have started to establish a European standard for Aspergillus-PCR. The principal goal of this initiative is to achieve a standard for PCR that can be incorporated into the next revision of the EORTC/MSG definitions for IA. Future prospective studies evaluating the potential benefits of early therapy based on R-T PCR in patients at high risk for IA infections are needed.

Risk stratification for invasive aspergillosis: early assessment of host susceptibility

Outcomes of invasive aspergillosis are substantially improved with early initiation of therapy. Unfortunately, the diagnosis remains difficult to establish so that early suspicion of infection is imperative. Identification of high risk patients and use of non-culture-based diagnostics and radiographic studies can facilitate earlier recognition of infection. It is important to realize that the timing and spectrum of risk for invasive aspergillosis have expanded. While patients with hematological malignancies and hematopoietic stem cell transplants make up the highest risk groups, patients such as those receiving steroids and other immunosuppressive therapies are also at risk. Non-culture-based methods (including galactomannan, 1,3-beta-D-glucan, and PCR-based methods) are actively being pursued to improve early diagnosis. Thus, identifying patients at high risk for infection and utilizing non-culture-based methods and radiologic studies to assist in establishing a likely diagnosis of invasive aspergillosis will further enhance the role of new agents in the early, effective treatment and prophylaxis of invasive aspergillosis.

Clinical and laboratory signs as dengue markers during an outbreak in Rio de Janeiro

BACKGROUND

One of the main challenges for clinical research in dengue is the low validity of clinical diagnosis.

OBJECTIVE

To analyze clinical and laboratory data as predicitve factors of dengue diagnosis at Evandro Chagas Clinical Research Institute, Oswaldo Cruz Foundation, during the 2001-2002 dengue outbreak in Rio de Janeiro.

METHODS

Cross sectional study comparing clinical laboratory data collected from the National Information System for Compulsory Notification Diseases (SINAN) in two serologically confirmed groups: dengue D (N = 453) and non-dengue ND (N = 80).

RESULTS

Fever, exanthema, itching, mean platelet count < 150,000, WBC count < 4,000 and absence of vomiting and of abdominal pain help to distinguish D from ND groups. When considered individually, these signs and symptoms enhance diagnostic sensitivity and, when used in combination, improve specificity.

CONCLUSION

A combination of symptoms not necessarily considered indicative of dengue diagnosis could improve surveillance and medical decision-making in simple clinical settings.

Significant alterations in the epidemiology and treatment outcome of invasive fungal infections in patients with hematological malignancies

Invasive fungal infections (IFI) remain a leading cause of morbidity and mortality in immunocompromised patients. This retrospective single-center study analyzed incidence, treatment and outcome of invasive fungal infections in 1,095 patients with hematological malignancies receiving either cytoreductive chemotherapy or autologous or allogeneic hematopoietic stem cell transplantation at our institution between 1995 and 2004. IFI occurred in 167/1,095 (15%) patients with a significant increase over time (12.7% between 1995 and 2000 vs. 18.1% in the later IFI cohort, P = 0.0134). Fifty-four (32%) patients had proven, 70 (42%) patients had probable, and 43 (26%) patients suffered from possible IFI according to EORTC/MSG criteria. In 108/124 (87%) cases with proven or probable IFI, moulds were the causative pathogens. Both, Aspergillus fumigatus (n = 46) and Aspergillus terreus (n = 41) were predominant. Yeast infections (Candida spp.) were documented in 16/124 (10%) cases with proven or probable IFI. Median overall survival of the entire IFI cohort was 7 (3-17) months. Overall survival was significantly better in patients with probable or possible IFI (37 and 38%, respectively) compared with patients with proven IFI (28%, P = 0.019). In 35% of patients, IFI was the principal cause of death with a significant decrease over time (44% in time cohort 1995-2000 vs. 28% in the later IFI cohort, P = 0.018) accompanied by an increased use of novel antifungals. By multivariate analysis, only proven IFI was significantly predictive for death (HR 1.7, P = 0.018). A significant decrease in fungus-related deaths was observed despite a significant increase of IFI over time, probably due to improved diagnostic and therapeutic approaches.

Detection of Aspergillus DNA in cerebrospinal fluid from patients with cerebral aspergillosis by a nested PCR assay

Invasive aspergillosis (IA), a complication with high mortality rates, especially in disseminated IA with cerebral involvement, is difficult to diagnose. Biopsy of cerebral lesions is often not feasible, and culture of Aspergillus spp. from cerebrospinal fluid (CSF) is frequently negative. New molecular methods have emerged for diagnosing IA. So far, there are only few reports of Aspergillus DNA detection in CSF. After modifying the DNA extraction protocol, we detected Aspergillus DNA in CSF samples by a previously described nested PCR assay. In six patients with hematologic malignancy and cerebral aspergillosis, CSF samples were investigated for Aspergillus DNA. IA was classified according to the EORTC/MSG 2002 criteria. Two patients each had proven, probable, and possible IA. Thirty-five CSF samples were investigated for Aspergillus DNA by nested PCR. Samples with positive results in the nested PCR assay were quantified by LightCycler PCR assay. Fourteen CSF samples showed positive results in the nested PCR assay. Of these, six samples gave positive results in real-time PCR. The range of CFU per ml was 2,154 to 63,100,000. The highest number of CFU per ml was found in a CSF sample of a patient with acute lymphocytic leukemia and probable cerebral aspergillosis. Detection of Aspergillus DNA in CSF samples is thus possible and has the potential to improve diagnosis of cerebral aspergillosis. Further prospective studies with larger numbers of patients must be performed to evaluate the clinical significance of Aspergillus PCR with CSF samples.

Fungal respiratory disease

PURPOSE OF REVIEW

Fungal respiratory disease is associated with a high mortality in immunocompromised patients. This review aims to describe the recent advances in the aetiology, clinical presentation, diagnosis and management of fungal respiratory disease.

RECENT FINDINGS

Invasive aspergillosis is an uncommon complication of hematopoietic stem cell transplants and solid-organ transplants but continues to be associated with poor outcome. Isolation of Aspergillus spp. from respiratory samples preceded acute rejection in lung-transplantation recipients. Molecular typing suggested that there was a very weak correlation between the environmental and patient isolates of Aspergillus fumigatus in invasive pulmonary aspergillosis. Serological and molecular detection of Aspergillus antigens or fungal DNA may improve the diagnosis of pulmonary aspergillosis, but the sensitivity is variable and more studies are needed. Voriconazole and caspofungin are choice to Aspergillus and Candida infection, especially to azole-resistant Candida spp. Treatment combining amphotericin B preparations, early surgical resection of infected tissue and discontinuation of immunosuppressive treatment may improve prognosis of mucormycosis.

SUMMARY

Invasive filamentaous fungal infections of lung remain important causes of death in immunocompromised patients. Development of new early diagnostic tools and well-designed multicenter evaluations of diagnostic methods and therapeutic regimens available at present are the important work in the next 2-3 years.

Early diagnosis of invasive aspergillosis in infants and children

Effective management of invasive aspergillosis (IA) requires early and accurate diagnosis. Microscopy and culture of appropriate specimens remain the gold standard of mycological diagnosis. High-resolution computed tomography serially performed constitutes a sensitive mode of diagnosis of pulmonary IA in hematological patients, but similar data is lacking for children. While early diagnosis of IA has been improved with galactomannan assay in adults, its use is problematic in young infants due to specificity inferiority. Galactomannan testing also is characterized by low sensitivity in pediatric patients with primary immunodeficiencies including chronic granulomatous disease and Job's syndrome. Beta-D glucan assay has been studied in adult patients with fungal infections including IA. The high negative predictive value of the assay allows its use for excluding IA; no specific data, however, exist for children. Polymerase chain reaction (PCR) may be a powerful tool for early diagnosis of IA but has not been standardized for routine use yet. No studies address the issue in neonates, whereas in children PCR has not been specifically studied but is probably as good as in adults. A high degree of suspicion in immunodeficient pediatric hosts, suggestive clinical and radiological findings, as well as mycological data by application of multiple diagnostic methods including serology and molecular biology, are expected to enhance the capacity to diagnose IA in young patients.