Invasive aspergillosis: epidemiology, diagnosis and management in immunocompromised patients

Intracellular concentrations of anidulafungin in different compartments of the peripheral blood

Pharmacokinetic studies usually focus on serum concentrations, hence little is known about intracellular drug concentrations. In this study, we determined the concentration of anidulafungin within different cellular compartments of the peripheral blood. Blood samples (n=17) from patients receiving anidulafungin were collected and separated by double-discontinuous Ficoll-Hypaque density gradient centrifugation. Intracellular concentrations within the obtained cells, i.e. peripheral blood mononuclear cells (PBMCs), polymorphonuclear leucocytes (PMNs) and red blood cells (RBCs), were determined by liquid chromatography tandem mass spectrometry (LC-MS/MS). Within the PBMCs and PMNs, the intracellular concentration of anidulafungin was significantly increased compared with the plasma concentration (P<0.001). However, the concentration within RBCs did not significantly differ from the plasma concentration. Anidulafungin reaches high concentrations in human PBMCs and PMNs and is present in RBCs. In vitro data showed that intracellular uptake of anidulafungin by PBMCs depends on the albumin concentration of the surrounding medium, but only at low, i.e. non-physiological, protein concentrations.

Utility of PCR in diagnosis of invasive fungal infections: real-life data from a multicenter study

Prospective studies addressing the clinical value of broad-range PCR using the internal transcribed spacer region (ITS) for diagnosis of microscopy-negative fungal infections in nonselected patient populations are lacking. We first assessed the diagnostic performance of ITS rRNA gene PCR compared with that of routine microscopic immunofluorescence examination. Second, we addressed prospectively the impact and clinical value of broad-range PCR for the diagnosis of infections using samples that tested negative by routine microscopy; the corresponding patients' data were evaluated by detailed medical record reviews. Results from 371 specimens showed a high concordance of >80% for broad-range PCR and routine conventional methods, indicating that the diagnostic performance of PCR for fungal infections is comparable to that of microscopy, which is currently considered part of the "gold standard." In this prospective study, 206 specimens with a negative result on routine microscopy were analyzed with PCR, and patients' clinical data were reviewed according to the criteria of the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group. We found that broad-range PCR showed a sensitivity, specificity, positive predictive value, and negative predictive value of 57.1%, 97.0%, 80%, and 91.7%, respectively, for microscopy-negative fungal infections. This study defines a possible helpful role of broad-range PCR for diagnosis of microscopy-negative fungal infections in conjunction with other tests.

Current understanding of HOG-MAPK pathway in Aspergillus fumigatus

Aspergillus fumigatus is an important opportunistic fungal pathogen that causes lethal systemic invasive aspergillosis. It must be able to adapt to stress in the microenvironment during host invasion and systemic spread. The high-osmolarity glycerol (HOG) mitogen-activated protein kinase (MAPK) signaling pathway is a key element that controls adaptation to environmental stress. It plays a critical role in the virulence of several fungal pathogens. In this review, we summarize the current knowledge about the functions of different components of the HOG-MAPK pathway in A. fumigatus through mutant analysis or inferences from the genome annotation, focusing on their roles in adaptation to stress, regulation of infection-related morphogenesis, and effect on virulence. We also briefly compare the functions of the HOG pathway in A. fumigatus with those in the model fungi Saccharomyces cerevisiae and Aspergillus nidulans as well as several other human and plant pathogens including Candida albicans, Cryptococcus neoformans, and Magnaporthe oryzae. The genes described in this review mainly include tcsB, fos1, skn7, sho1, pbs2, and sakA whose deletion mutants have already been established in A. fumigatus. Among them, fos1 has been considered a virulence factor in A. fumigatus, indicating that components of the HOG pathway may be suitable as targets for developing new fungicides. However, quite a few of the genes of this pathway, such as sskA (ssk1), sskB, steC, and downstream regulator genes, are not well characterized. System biology approaches may contribute to a more comprehensive understanding of HOG pathway functions with dynamic details.

Invasive aspergillosis in a renal transplant recipient successfully treated with interferon-gamma

Invasive aspergillosis is a serious complication of solid organ transplantation. An early diagnosis is hampered by the lack of reliable serum markers and, even if appropriately diagnosed and treated with current antifungal agents, has a high mortality rate. We report a case of invasive pulmonary and cerebral aspergillosis in a renal transplant patient treated with IFN-γ in conjunction with combination anti-fungal therapy for six weeks in whom complete resolution of the fungal infection was achieved. Renal function remained intact throughout the treatment period. Surveillance CT scans of the chest and head showed resolution of prior disease but revealed a new left upper lobe mass four months after completion of treatment with IFN-γ. Biopsy of the lesion was positive for primary lung adenocarcinoma, for which she underwent left upper lobe resection. The pathology report confirmed clear surgical margins and lymph nodes and no evidence of fungal hyphae. IFN-γ should be considered early in the management of invasive aspergillosis in renal transplant patients. To date, allograft rejection has not been encountered.

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.

Bis(methyl)gliotoxin proves to be a more stable and reliable marker for invasive aspergillosis than gliotoxin and suitable for use in diagnosis

The virulence factor gliotoxin (GT) and its inactive derivative, bis(methylthio)gliotoxin (bmGT), are produced by pathogens of the genus Aspergillus. Here we report the detection of GT and bmGT in serum of humans at risk of invasive aspergillosis (IA) as well as in cultures of fungal isolates derived from patients with proven infection with A. fumigatus. Although both compounds are readily recoverable from spiked human serum or plasma, only bmGT is retained in whole blood, indicating that bmGT may be the better marker for in vivo detection. Accordingly, bmGT was found more frequently than GT in samples from patients at risk of IA and incultures of clinical isolates of A. fumigatus. In some cases, bmGT was detected before mycologic evidence ofinfection was gained. Importantly, neither GT nor bmGT was found in serum from healthy donors or from neutropenic patients without any sign of infection. Thus, bmGT presence might provide a more reliable indicator of A. fumigatus infections than GT. Due to its simplicity and sensitivity, a diagnostic technology based on this test could be easily adopted in clinical laboratories to help in the diagnosis of this often fatal fungal infection.

[Place of surgery in pulmonary aspergillosis and other pulmonary mycotic infections]

Surgery is part of the therapeutic strategy of aspergillosis and mucormycosis. The aspergilloma is defined as a rounded mass, developing in a cavity by the proliferation of spores of Aspergillus. The most common complication was haemoptysis reported in 50-95% of cases. The pleuropulmonary lesions predisposing are: tuberculosis, residual pleural space, emphysema and lung destroyed by fibrosis or radiotherapy or bronchiectasis. The indications for surgery depend on symptoms, respiratory function, the parenchyma and the type of aspergilloma (simple or complex). In a patient with an intrapulmonary aspergilloma, lung resection preceded by embolization is recommended based on respiratory function. For intrapleural aspergilloma, thoracoplasty is recommended according to the patient's general condition. The invasive pulmonary aspergillosis (IPA) is characterized by an invasion of lung tissue and blood vessels by hyphae in immunocompromised patients. The death rate of patients who have an API after treatment for leukemia or lymphoma was 30 to 40%, after bone marrow transplantation 60%, after solid organ transplantation from 50 to 60% and after any other cause of immunocompromising from 70 to 85%. The main cause of these deaths is massive hemoptysis. Surgery (lobectomy) is indicated for the prevention of hemoptysis when the mass is in contact with the pulmonary artery or one of its branches, and if it increases in size with the disappearance of border security between the mass and the vessel wall. The patient will be operated in an emergency before the white blood cells do not exceed the threshold of 1000 cells/μl. A persistent residual mass after antifungal treatment may justify a lung resection (lobectomy or wedge) before a new aggressive therapy. Mucormycosis affects patients following immunocompromising states--haematologic malignancy, diabetes mellitus, transplantation, burns and malnutrition. The treatment of pulmonary mucormycosis combines surgical and medical approach.

The strategy for the diagnosis of invasive pulmonary aspergillosis should depend on both the underlying condition and the leukocyte count of patients with hematologic malignancies

The identification of the causative organism in invasive pulmonary aspergillosis (IPA) is recommended. We investigated whether a mycologic diagnostic strategy could be optimized based on patient characteristics. Fifty-five patients were enrolled in a prospective study. The presence of Aspergillus in respiratory samples occurred more frequently in non-acute leukemia (AL) patients than in AL patients (P = .0003), and in patients with leukocyte counts more than 100/mm3 (P = .002). In a logistic regression model, these 2 factors appeared to be independent, with an adjusted odds ratio of 7.14 (95% confidence interval, 1.40-36.5) for non-AL patients and an adjusted odds ratio of 6.97 (95% confidence interval, 1.33-36.5) for patients with leukocyte counts more than 100/mm3. A positive mycologic result was also more frequent among patients with lung CT scan signs of airway-invasive disease than among other patients (P = .043). Airway-invasive signs were more frequent among non-AL patients (P = .049), whereas angioinvasive disease was more frequent among both AL patients (P = .01) and patients with leukocyte counts less than 100/mm3 (P = .001). A concomitant pulmonary infection was identified more frequently among non-AL patients (P = .005 vs allogeneic hematopoietic stem cell transplant and P = .048 vs others). Our results suggest that different strategies for diagnosing IPA should be considered based on the underlying condition.

Expression turnover profiling to monitor the antifungal activities of amphotericin B, voriconazole, and micafungin against Aspergillus fumigatus

Eight highly expressed candidate genes were selected for mRNA profiling to monitor the transcriptome kinetics of Aspergillus fumigatus strains exposed to antifungal drugs as potential biomarkers of live cells to assess treatment efficacy. Mycelia were treated with fungicidal drugs amphotericin B and voriconazole, as well as the fungistatic drug micafungin. Transcription was monitored at 0, 4, 8, and 24 h posttreatment. The expression turnover profile provides a possible tool to assess antifungal therapy effects.

Real-time nucleic acid sequence-based amplification to predict the clinical outcome of invasive aspergillosis

Monitoring the response to therapy for invasive aspergillosis (IA) is essential for the management of patients with hematologic diseases. We evaluated the correlation between the outcome of real-time nucleic acid sequence-based amplification (RTi-NASBA) for Aspergillus 18S rRNA and the clinical outcome of IA. A total of 157 serum samples from 29 patients with IA were tested for RTi-NASBA. The treatment response and mortality were compared with the NASBA outcome (whether the NASBA value was converted to negative or not) at 12 weeks after the start of antifungal therapy. At 12 weeks, there was a moderate correlation between the treatment failure and persistently positive NASBA (κ = 0.482; P = 0.019). Deaths attributable to IA were more prevalent in patients without negative conversion of NASBA than in those with negative conversion (50% vs 5%; P = 0.013). Significant factors of treatment failure at 12 weeks were the status of hematologic disease (nonremission; P = 0.041) and the NASBA outcome (failure of negative conversion; P = 0.024). Survival was significantly better in patients with negative conversion of NASBA than those with persistently positive values (P = 0.036). This study suggests that the serial monitoring of RTi-NASBA could be useful for prediction of the clinical outcome in hematologic patients with IA.

Tracheobronchial manifestations of Aspergillus infections

Human lungs are constantly exposed to a large number of Aspergillus spores which are present in ambient air. These spores are usually harmless to immunocompetent subjects but can produce a symptomatic disease in patients with impaired antifungal defense. In a small percentage of patients, the trachea and bronchi may be the main or even the sole site of Aspergillus infection. The clinical entities that may develop in tracheobronchial location include saprophytic, allergic and invasive diseases. Although this review is focused on invasive Aspergillus tracheobronchial infections, some aspects of allergic and saprophytic tracheobronchial diseases are also discussed in order to present the whole spectrum of tracheobronchial aspergillosis. To be consistent with clinical practice, an approach basing on specific conditions predisposing to invasive Aspergillus tracheobronchial infections is used to present the differences in the clinical course and prognosis of these infections. Thus, invasive or potentially invasive Aspergillus airway diseases are discussed separately in three groups of patients: (1) lung transplant recipients, (2) highly immunocompromised patients with hematologic malignancies and/or patients undergoing hematopoietic stem cell transplantation, and (3) the remaining, less severely immunocompromised patients or even immunocompetent subjects.

An observational efficacy and safety analysis of the treatment of acute invasive aspergillosis using voriconazole

The purpose of this study was to evaluate efficacy and safety of voriconazole in patients with acute invasive aspergillosis (IA) in a real-life, clinical setting. This was a multicenter observational study in adult patients treated with voriconazole for invasive mycosis. The study evaluated clinical response, mortality, use of other licensed antifungal therapy (OLAT), and treatment duration. This sub-analysis evaluated treatment and outcome data specifically from adult patients with proven/probable IA, while safety data were assessed in patients with proven/probable/possible IA. Of the 141 patients enrolled, 113 were adults with proven/probable IA and six had possible IA. Voriconazole treatment duration ranged from 1 to 183 days (median, 49.5 days). Voriconazole was used exclusively in 64% (72/113) of patients and in combination/sequentially with OLAT in 36%. Overall successful treatment response was 50% (57/113 patients). Twelve percent (14/113) of patients were switched to OLAT, either because of insufficient response (four patients) or for safety reasons (10 patients). Overall and attributable (entirely or partially due to fungal infection) mortality rates were 52% (59/113) and 17%, respectively. Treatment-related adverse events were reported for 18% (22/119) of patients. This observational study confirms the results of previous clinical trials demonstrating voriconazole as an effective and safe agent for treatment of confirmed acute IA.

The structure-function relationship of the Aspergillus fumigatuscyp51A L98H conversion by site-directed mutagenesis: the mechanism of L98H azole resistance

Since 1998, the rapid emergence of multi-azole-resistance (MAR) was observed in Aspergillus fumigatus in the Netherlands. Two dominant mutations were found in the cyp51A gene, a 34bp tandem repeat (TR) in the promoter region combined with a leucine to histidine substitution at codon 98 (L98H). In this study, we show that molecular dynamics simulations combined with site-directed mutagenesis of amino acid substitutions in the cyp51A gene, correlate to the structure-function relationship of the L98H substitution conferring to MAR in A. fumigatus. Because of a L98H directed change in the flexibility of the loops, that comprise a gate-like structure in the protein, the capacity of the two ligand entry channels is modified by narrowing the diameter and thereby binding of azoles is obstructed. Moreover, the L98H induced relocation of tyrosine 121 and tyrosine 107 seems to be related to the MAR phenotype, without affecting the biological activity of the CYP51A protein. Site-directed mutagenesis showed that both the 34bp TR and the L98H mutation are required to obtain the MAR phenotype. Furthermore, the amino acid leucine in codon 98 in A. fumigatus is highly conserved and important for maintaining the structure of the CYP51A protein that is essential for azole docking.

Voriconazole serum concentrations in prophylactically treated acute myelogenous leukaemia patients

Antifungal prophylaxis during first remission induction chemotherapy for acute myelogenous leukaemia requires broad spectrum azoles. In a clinical trial, therapeutic drug monitoring (TDM) of antifungal prophylaxis with voriconazole 200 mg bid was evaluated in a population of six patients. High pressure liquid chromatography was applied. Trough levels were obtained 24 h after the last voriconazole dose. Median time of voriconazole exposure prior to sample acquisition was 16 days (range 9-21). The mean voriconazole concentration was 486 μg l(-1) and ranged from 136 μg l(-1) to 1257 μg l(-1). Among possible or probable treatment-related adverse events, elevated liver function tests were the most frequent. Five of six patients developed fever during neutropenia, but none of them developed pulmonary infiltrates or other signs of invasive fungal infection while on voriconazole prophylaxis. Future investigations might aim at identifying drug level thresholds that allow for minimum toxicity and optimum efficacy of antifungal prophylaxis.

Pre-emptive diagnosis and treatment of fungal infections--evaluation of a single-centre policy

Invasive fungal disease (IFD) remains a significant cause of mortality in haematology patients. Management strategies range from empiric therapy to pre-emptive approaches. Prophylaxis with mould-active agents has been evaluated, but the optimal strategy remains unclear. We present here a retrospective analysis of the pre-emptive strategy implemented at our institution. We analysed 348 consecutive neutropenic episodes in 234 patients. The main elements of our pre-emptive strategy included twice-weekly Galactomannan testing and weekly computed tomography (CT) scan. Antifungal prophylaxis usually consisted of fluconazole (400 mg once weekly). Antifungal treatment was started if criteria for IFD (including possible) were fulfilled. Along with the incidence of antifungal treatment and IFD, we also analysed the adherence to the strategy. Adherence was good but suboptimal with 81% of CT scans having been performed at an interval of 10 days or less. Concerning antifungal treatment, in 56 episodes the patient was receiving a mould-active agent as secondary prophylaxis. Antifungal treatment was started during 39% of the remaining episodes. In all, 109 cases of IFD were diagnosed, 51 being probable or proven. Forty-nine patients died before day 100, IFD directly caused or contributed to death in six patients. Two cases of IFD were diagnosed post-mortem and were missed by our pre-emptive strategy. Our pre-emptive strategy is feasible and safe with an acceptable rate of IFD and associated mortality, while avoiding anti-fungal treatment in a significant proportion of patients. The exact role of pre-emptive treatment compared with systematic mould-active prophylaxis can only be determined in a well-designed randomized trial.

Posaconazole: a pharmacoeconomic review of its use in the prophylaxis of invasive fungal disease in immunocompromised hosts

Posaconazole (Noxafil®) is an oral, second-generation, extended-spectrum triazole whose approved indications include prophylaxis of invasive fungal disease (IFD) in immunocompromised patients. In pivotal head-to-head trials, posaconazole was significantly more effective in preventing IFD than standard azole therapy (i.e. oral fluconazole or itraconazole) in chemotherapy-induced neutropenic patients with acute myelogenous leukaemia (AML) or myelodysplastic syndromes (MDS) and was noninferior to treatment with fluconazole in patients with graft-versus-host disease (GVHD) who were receiving intensive immunosuppressive therapy following haematopoietic stem cell transplantation. In both indications, prophylactic posaconazole was associated with significantly lower rates of IFD-related mortality. The overall tolerability profile of posaconazole was generally similar to that of the other prophylactic treatments. The large body of modelled cost-effectiveness analyses from a healthcare payer perspective on the use of prophylactic posaconazole suggest that it is a dominant or cost-effective option relative to prophylaxis with standard azole therapy in neutropenic patients with AML/MDS, and fluconazole in patients with GVHD. Based on clinical trial data in these patient groups, antifungal prophylaxis with posaconazole was predicted to be a dominant or cost-effective option relative to prophylaxis with standard oral azoles, with regard to the incremental cost per QALY gained, life-year (LY) gained and/or other outcomes in cost-effectiveness analyses in numerous countries. In those analyses in which posaconazole did not dominate the comparator, posaconazole was considered cost effective, as the incremental cost per QALY or LY gained with posaconazole was lower than assumed willingness-to-pay thresholds. Sensitivity analyses consistently demonstrated that these results were robust to plausible changes in key model assumptions. In conclusion, prophylactic treatment with posaconazole is clinically effective in preventing IFD in neutropenic patients with AML/MDS and patients with GVHD. Available pharmacoeconomic data from several countries, despite some inherent limitations, support the use of posaconazole as a dominant or cost-effective prophylactic antifungal treatment relative to prophylaxis with standard oral azoles in these patient populations at high risk of developing IFD.

Azole resistance in Aspergillus fumigatus: a new challenge in the management of invasive aspergillosis?

Azole resistance is emerging in Aspergillus fumigatus isolates. The exact mechanism of evolution of azole resistance has not been fully elucidated yet but increasing evidence indicates a role for azole fungicide used in agriculture. Patients confronted with an invasive fungal infection from an azole-resistant A. fumigatus isolate will fail azole treatment. Azole resistance in A. fumigatus isolates impacts the management of invasive aspergillosis (IA) since the azoles are the primary agents used for prophylaxis and treatment. Because A. fumigatus will always be present in our environment and also in the close vicinity of patients at risk for IA, there is an urgent need to understand the evolution of the increasing azole resistance in A. fumigatus. Thereby, induction of azole resistance or its spread can possibly be prevented to allow future treatment of A. fumigatus IA.

Posaconazole prophylaxis in patients with acute myelogenous leukaemia--results from an observational study

Patients with acute myelogenous leukaemia (AML) and neutropenia after chemotherapy are at high risk for life-threatening invasive fungal disease (IFD), in particular, invasive aspergillosis (IA). The aim of the study was to evaluate data on characteristics, risk factors, complications and additional antifungal treatment of patients with AML receiving posaconazole prophylaxis (PP) after chemotherapy in an actual clinical setting. A retrospective single-centre observational study on 40 patients with AML, median age 66 years, was conducted. PP 200 mg three times daily was given routinely. After 76 cycles of remission induction chemotherapy followed by PP, median duration of 31 days (range 6-61 days), no fatal case occurred. The majority of patients had at least one additional risk factor for IFD and during 32 cycles (42.1%), three risk factors were present. During 40 therapy cycles (52.6%), fever of unknown origin occurred. Pneumonia was diagnosed after 23 cycles (30.3%), thereof one case of proven IA (1.3%). PP was interrupted in 25 cycles (32.9%) and was followed by systemic antifungal therapy with different agents, with a median duration 15 days (range: 6-32 days). PP appears to be an effective and well-tolerated protection against IFD for AML patients under natural clinical conditions.

Aspergillus viridinutans: an agent of adult chronic invasive aspergillosis

In contrast with the common hematogenous dissemination of invasive aspergillosis (IA), we present case with a protracted course through anatomical planes in an immunocompromised adult male. The unusual clinical features and laboratory findings led to fungal genotyping and identification of the mold as Aspergillus viridinutans. It appears to be the first described case of IA caused by this agent in an adult patient.

Invasive pulmonary aspergillosis in patients with HBV-related liver failure

Invasive pulmonary aspergillosis (IPA) has been increasingly frequent in severe liver disease. We aim to investigate the clinical presentation, predisposing factors, and treatment of IPA in patients with liver failure caused by hepatitis B virus (HBV) infection. Medical records from 798 patients with HBV-related liver failure were reviewed. A total of 43 patients with probable IPA were selected as the case group, another 43 patients with bacterial infection and 43 patients without any infections were selected, for whose age, sex, date of admission, and the disease onset were matched with the case group. We evaluated the risk factors, clinical manifestations, treatment, and subsequent outcome of IPA in patients with HBV-related liver failure. Multivariate logistic regression models were used to demonstrate risk factors associated with IPA. Compared with patients with bacterial infection and those without any infection, patients with probable IPA used more antibiotics and steroids, and had poorer conditions and the highest mortality (P < 0.0001). Multiple antibiotics use and frequent invasive procedures were independent factors associated with the occurrence of IPA in patients with HBV-related liver failure. Patients with HBV-related liver failure are predisposed to IPA and may have a more severe condition and poorer prognosis.

What makes Aspergillus fumigatus a successful pathogen? Genes and molecules involved in invasive aspergillosis

Aspergillus fumigatus is an opportunistic pathogen that causes 90% of invasive aspergillosis (IA) due to Aspergillus genus, with a 50-95% mortality rate. It has been postulated that certain virulence factors are characteristic of A. fumigatus, but the "non-classical" virulence factors seem to be highly variable. Overall, published studies have demonstrated that the virulence of this fungus is multifactorial, associated with its structure, its capacity for growth and adaptation to stress conditions, its mechanisms for evading the immune system and its ability to cause damage to the host. In this review we intend to give a general overview of the genes and molecules involved in the development of IA. The thermotolerance section focuses on five genes related with the capacity of the fungus to grow at temperatures above 30°C (thtA, cgrA, afpmt1, kre2/afmnt1, and hsp1/asp f 12). The following sections discuss molecules and genes related to interaction with the host and with the immune responses. These sections include β-glucan, α-glucan, chitin, galactomannan, galactomannoproteins (afmp1/asp f 17 and afmp2), hydrophobins (rodA/hyp1 and rodB), DHN-melanin, their respective synthases (fks1, rho1-4, ags1-3, chsA-G, och1-4, mnn9, van1, anp1, glfA, pksP/alb1, arp1, arp2, abr1, abr2, and ayg1), and modifying enzymes (gel1-7, bgt1, eng1, ecm33, afpigA, afpmt1-2, afpmt4, kre2/afmnt1, afmnt2-3, afcwh41 and pmi); several enzymes related to oxidative stress protection such as catalases (catA, cat1/catB, cat2/katG, catC, and catE), superoxide dismutases (sod1, sod2, sod3/asp f 6, and sod4), fatty acid oxygenases (ppoA-C), glutathione tranferases (gstA-E), and others (afyap1, skn7, and pes1); and efflux transporters (mdr1-4, atrF, abcA-E, and msfA-E). In addition, this review considers toxins and related genes, such as a diffusible toxic substance from conidia, gliotoxin (gliP and gliZ), mitogillin (res/mitF/asp f 1), hemolysin (aspHS), festuclavine and fumigaclavine A-C, fumitremorgin A-C, verruculogen, fumagillin, helvolic acid, aflatoxin B1 and G1, and laeA. Two sections cover genes and molecules related with nutrient uptake, signaling and metabolic regulations involved in virulence, including enzymes, such as serine proteases (alp/asp f 13, alp2, and asp f 18), metalloproteases (mep/asp f 5, mepB, and mep20), aspartic proteases (pep/asp f 10, pep2, and ctsD), dipeptidylpeptidases (dppIV and dppV), and phospholipases (plb1-3 and phospholipase C); siderophores and iron acquisition (sidA-G, sreA, ftrA, fetC, mirB-C, and amcA); zinc acquisition (zrfA-H, zafA, and pacC); amino acid biosynthesis, nitrogen uptake, and cross-pathways control (areA, rhbA, mcsA, lysF, cpcA/gcn4p, and cpcC/gcn2p); general biosynthetic pathway (pyrG, hcsA, and pabaA), trehalose biosynthesis (tpsA and tpsB), and other regulation pathways such as those of the MAP kinases (sakA/hogA, mpkA-C, ste7, pbs2, mkk2, steC/ste11, bck1, ssk2, and sho1), G-proteins (gpaA, sfaD, and cpgA), cAMP-PKA signaling (acyA, gpaB, pkaC1, and pkaR), His kinases (fos1 and tcsB), Ca(2+) signaling (calA/cnaA, crzA, gprC and gprD), and Ras family (rasA, rasB, and rhbA), and others (ace2, medA, and srbA). Finally, we also comment on the effect of A. fumigatus allergens (Asp f 1-Asp f 34) on IA. The data gathered generate a complex puzzle, the pieces representing virulence factors or the different activities of the fungus, and these need to be arranged to obtain a comprehensive vision of the virulence of A. fumigatus. The most recent gene expression studies using DNA-microarrays may be help us to understand this complex virulence, and to detect targets to develop rapid diagnostic methods and new antifungal agents.

Efficacy outcomes in a randomised trial of liposomal amphotericin B based on revised EORTC/MSG 2008 definitions of invasive mould disease

In 2008, the European Organisation for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) published revised definitions for diagnosing invasive fungal disease. A previous prospective trial of liposomal amphotericin B for invasive mould disease (AmBiLoad) used modified EORTC/MSG 2002 criteria. We wished to re-evaluate the response and survival based on the revised definitions to compare the outcomes of early vs. late treatment. Patients who had received an allogeneic haematopoietic stem cell transplant or who were neutropaenic (absolute neutrophil count <500 μl(-1) within 14 days of study entry) had been recruited on the basis of a halo or air crescent sign on chest computerised tomography. Originally classified as probable invasive mould disease, they were categorised as possible invasive mould disease using 2008 criteria. Patients had received liposomal amphotericin B at either 3 or 10 mg kg(-1) QD for 14 days, followed by 3 mg kg(-1) QD. Response at end of treatment and the 12-week survival were re-calculated according to 2008 definitions. Six-week survival was estimated by Kaplan-Meier analysis. Of 201 patients with invasive mould disease, 118 (59%) had a diagnosis based on halo signs (possible cases). Mycological evidence was present in 83 (41%) cases (probable/proven cases). Survival rates at 12 weeks for possible vs. probable/proven cases in the 3 mg kg(-1) QD group were 82% vs. 58% (P = 0.006), and 65% vs. 50% (P = 0.15) in the 10 mg kg(-1) QD group. At 6 weeks, rates were 87% vs. 69% in the 3 mg kg(-1) QD group (P = 0.009), and 75% vs. 61% in the 10 mg kg(-1) QD group (P = 0.01). Patients with possible invasive mould disease based on EORTC/MSG 2008 criteria had improved survival rates compared with those treated for probable/proven invasive mould disease. As possible invasive mould disease probably reflects an early-stage of disease, a better outcome might be expected when treatment with liposomal amphotericin B is started preemptively.

Aspergillus fumigatus AcuM regulates both iron acquisition and gluconeogenesis

Relatively few transcription factors that govern the virulence of Aspergillus fumigatus are known. We constructed 11 A. fumigatus transcription factor mutants and screened them for altered virulence in Galleria mellonella larvae. We discovered that the zinc cluster transcription factor, AcuM, is essential for maximal virulence in this model, as well as in murine models of haematogenously disseminated and invasive pulmonary aspergillosis. Transcriptional profiling experiments suggested that AcuM suppresses sreA and induces hapX to stimulate expression of genes involved in both reductive iron assimilation and siderophore-mediated iron uptake. Consistent with these results, a ΔacuM mutant had reduced iron incorporation, decreased extracellular siderophore production and impaired capacity to grow under iron-limited conditions. Interestingly, an Aspergillus nidulansΔacuM mutant had normal extracellular siderophore production and growth under iron-limited conditions, indicating that AcuM does not govern iron acquisition in this organism. A. fumigatus AcuM also regulated genes involved in gluconeogenesis, and the ΔacuM mutant had impaired growth on gluconeogenic carbon sources. Deletion of sreA in the ΔacuM mutant restored iron uptake, extracellular siderophore production and virulence, but not the defect in gluconeogenesis. Thus, AcuM represses SreA and thereby induces iron acquisition, a process that is essential for the maximal virulence of A. fumigatus.

Immunogenetics of invasive aspergillosis

Invasive aspergillosis is one of the most important infections in hematopoietic stem cell transplant recipients, with an incidence rate of 5-15% and an associated mortality of 30-60%. It remains unclear why certain patients develop invasive aspergillosis while others, undergoing identical transplant regimen and similar post transplant immunosuppression, do not. Over the last decade, pattern recognition receptors such as Toll-like receptors (TLRs) and the C-type lectin receptors (CLRs) have emerged as critical components of the innate immune system. By detecting specific molecular patterns from invading microbes and initiating inflammatory and subsequent adaptive immune responses, pattern recognition receptors are strategically located at the molecular interface of hosts and pathogens. Polymorphisms in pattern recognition receptors and downstream signaling molecules have been associated with increased or decreased susceptibility to infections, suggesting that their detection may have an increasing impact on the treatment and prevention of infectious diseases in the coming years. Infectious risk stratification may be particularly relevant for patients with hematologic malignancies, because of the high prevalence and severity of infections in this population. This review summarizes the innate immune mechanisms involved in Aspergillus fumigatus detection and the role of host genetic polymorphisms in susceptibility to invasive aspergillosis.

Augmenting the activity of antifungal agents against aspergilli using structural analogues of benzoic acid as chemosensitizing agents

A number of benzoic acid analogues showed antifungal activity against strains of Aspergillus flavus, Aspergillus fumigatus and Aspergillus terreus, causative agents of human aspergillosis, in in vitro bioassays. Structure-activity analysis revealed that antifungal activities of benzoic and gallic acids were increased by addition of a methyl, methoxyl or chloro group at position 4 of the aromatic ring, or by esterification of the carboxylic acid with an alkyl group, respectively. Thymol, a natural phenolic compound, was a potent chemosensitizing agent when co-applied with the antifungal azole drugs fluconazole and ketoconazole. The thymol-azole drug combination demonstrated complete inhibition of fungal growth at dosages far lower than the drugs alone. Co-application of thymol with amphotericin B had an additive effect on all strains of aspergilli tested with the exception of two of three strains of A. terreus, where there was an antagonistic effect. Use of two mitogen-activated protein kinase (MAPK) mutants of A. fumigatus, sakAΔ and mpkCΔ, having gene deletions in the oxidative stress response pathway, indicated antifungal and/or chemosensitization activity of the benzo analogues was by disruption of the oxidative stress response system. Results showed that both these genes play overlapping roles in the MAPK system in this fungus. The potential of safe, natural compounds or analogues to serve as chemosensitizing agents to enhance efficacy of commercial antifungal agents is discussed.

Factors associated with mortality in transplant patients with invasive aspergillosis

BACKGROUND

Invasive aspergillosis (IA) is an important cause of morbidity and mortality in hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients. The purpose of this study was to evaluate factors associated with mortality in transplant patients with IA.

METHODS

Transplant patients from 23 US centers were enrolled from March 2001 to October 2005 as part of the Transplant Associated Infection Surveillance Network. IA cases were identified prospectively in this cohort through March 2006, and data were collected. Factors associated with 12-week all-cause mortality were determined by logistic regression analysis and Cox proportional hazards regression.

RESULTS

Six-hundred forty-two cases of proven or probable IA were evaluated, of which 317 (49.4%) died by the study endpoint. All-cause mortality was greater in HSCT patients (239 [57.5%] of 415) than in SOT patients (78 [34.4%] of 227; P<.001). Independent poor prognostic factors in HSCT patients were neutropenia, renal insufficiency, hepatic insufficiency, early-onset IA, proven IA, and methylprednisolone use. In contrast, white race was associated with decreased risk of death. Among SOT patients, hepatic insufficiency, malnutrition, and central nervous system disease were poor prognostic indicators, whereas prednisone use was associated with decreased risk of death. Among HSCT or SOT patients who received antifungal therapy, use of an amphotericin B preparation as part of initial therapy was associated with increased risk of death.

CONCLUSIONS

There are multiple variables associated with survival in transplant patients with IA. Understanding these prognostic factors may assist in the development of treatment algorithms and clinical trials.

Primary antifungal prophylaxis in acute myeloblastic leukemia and myelodysplastic syndrome--still an open question?

In this review, we aim to compare different early treatment strategies of invasive fungal diseases in patients undergoing induction chemotherapy for acute myelogenous leukemia or myelodysplastic syndrome. Three treatment approaches--prophylactic, empiric, and preemptive treatment--are subject to continuous discussion among physicians treating patients at risk. Considering the available clinical basis of evidence, we opt for antifungal prophylaxis with posaconazole 200 mg tid po as our primary prophylactic strategy, while the employment of preemptive treatment should be delayed until more accurate diagnostic tools become available. In addition to antifungal prophylaxis, empiric treatment with caspofungin or L-AmB may be administered to patients with fever resistant to broad-spectrum antibiotic treatment and without radiographic findings typical of invasive fungal disease.