Current status of fungal cell wall components in the immunodiagnostics of invasive fungal infections in humans: galactomannan, mannan and (1-->3)-beta-D-glucan antigens

False-positive Elevation of Beta-D-glucan and Aspergillus Galactomannan Levels Due to Mendelson's Syndrome after Rice Aspiration

Both 1,3-beta-D-glucan (BDG) and galactomannan (GM) are polysaccharide components of the fungal cell wall. Although elevated levels of serum BDG and Aspergillus GM suggest invasive fungal infection or Pneumocystis pneumonia and aspergillosis, respectively, it is also necessary to consider the possibility of false-positives. We herein report a 68-year-old man with marked elevation in serum BDG and GM levels accompanied by Mendelson's syndrome after rice aspiration. With the improvement of Mendelson's syndrome, his serum BDG and GM levels decreased. The false-positive serum BDG and GM findings may have been due to his aspiration of food containing them. It is important to take a detailed history of aspiration in addition to making a conventional differential diagnosis in patients with pneumonia with elevated serum BDG and GM levels.

Evaluation of Vitreous Galactomannan and (1, 3) β-D-Glucan Levels in the Diagnosis of Fungal Endophthalmitis in Southern India

PURPOSE

To evaluate vitreous Galactomannan(GM) and 1,3 β-D-Glucan (BDG) levels in the diagnosis of fungal endophthalmitis, with emphasis on culture-negative cases.

METHODS

Vitreous from 31 clinically suspected fungal endophthalmitis patients and 11 controls were evaluated for GM and BDG using ELISA Kits. The Receiver Operating Characteristic (ROC) curves and diagnostic significance was calculated.

RESULTS

The median vitreous GM in culture-positive (60.83pg/ml) and culture-negative (59.9pg/ml) samples were higher than the (51.2pg/ml) control group. The median vitreous BDG in culture-positive (1.47pg/ml) and culture-negative (1.52pg/ml) samples were also similar, and higher than the control group (1.18pg/ml). ROC analysis showed that at a cut-off of 51.35pg/ml, the sensitivity and specificity for GM were 0.88 and 0.73.Similarly, for BDG at a cut-off of 1.18pg/ml, the sensitivity and specificity were 0.94 and 0.82 respectively.

CONCLUSION

Vitreous GM and BDG above the indicated threshold level could suggest a fungal infection, even when cultures are negative.

Diagnostic Performance of (1→3)-β-D-Glucan Alone and in Combination with Aspergillus PCR and Galactomannan in Serum of Pediatric Patients after Allogeneic Hematopoietic Stem Cell Transplantation

Data on biomarker-assisted diagnosis of invasive aspergillosis (IA) in pediatric patients is scarce. Therefore, we conducted a cohort study over two years including 404 serum specimens of 26 pediatric patients after allogeneic hematopoietic stem cell transplantation (alloSCT). Sera were tested prospectively twice weekly for Aspergillus-specific DNA, galactomannan (GM), and retrospectively for (1→3)-β-D-glucan (BDG). Three probable IA and two possible invasive fungal disease (IFD) cases were identified using the European Organization for Research and Treatment of Cancer and the Mycoses Study Group (EORTC/MSGERC) 2019 consensus definitions. Sensitivity and specificity for diagnosis of probable IA and possible IFD was 80% (95% confidential interval (CI): 28–99%) and 55% (95% CI: 32–77%) for BDG, 40% (95% CI: 5–85%) and 100% (95% CI: 83–100%) for GM, and 60% (95% CI: 15–95%) and 95% (95% CI: 75–100%) for Aspergillus-specific real-time PCR. However, sensitivities have to be interpreted with great caution due to the limited number of IA cases. Interestingly, the low specificity of BDG was largely caused by false-positive BDG results that clustered around the date of alloSCT. The following strategies were able to increase BDG specificity: two consecutive positive BDG tests for diagnosis (specificity 80% (95% CI: 56–94%)); using an optimized cutoff value of 306 pg/mL (specificity 90% (95% CI: 68–99%)) and testing BDG only after the acute posttransplant phase. In summary, BDG can help to diagnose IA in pediatric alloSCT recipients. However, due to the poor specificity either an increased cutoff value should be utilized or BDG results should be confirmed by an alternative Aspergillus assay.

The putative polysaccharide synthase AfCps1 regulates Aspergillus fumigatus morphogenesis and conidia immune response in mouse bone marrow-derived macrophages

Aspergillus fumigatus is a well-known opportunistic pathogen that causes invasive aspergillosis (IA) infections with high mortality in immunosuppressed individuals. Morphogenesis, including hyphal growth, conidiation, and cell wall biosynthesis is crucial in A. fumigatus pathogenesis. Based on a previous random insertional mutagenesis library, we identified the putative polysaccharide synthase gene Afcps1 and its para-log Afcps2. Homologs of the cps gene are commonly found in the genomes of most fungal and some bacterial pathogens. Afcps1/cpsA is important in sporulation, cell wall composition, and virulence. However, the precise regulation patterns of cell wall integrity by Afcps1/cpsA and further effects on the immune response are poorly understood. Specifically, our in-depth study revealed that Afcps1 affects cell-wall stability, showing an increased resistance of ΔAfcps1 to the chitinmicrofibril destabilizing compound calcofluor white (CFW) and susceptibility of ΔAfcps1 to the β-(1,3)-glucan synthase inhibitor echinocandin caspofungin (CS). Additionally, deletion of Afcps2 had a normal sporulation phenotype but caused hypersensitivity to Na⁺ stress, CFW, and Congo red (CR). Specifically, quantitative analysis of cell wall composition using high-performance anion exchange chromatography-pulsed amperometric detector (HPAEC-PAD) analysis revealed that depletion of Afcps1 reduced cell wall glucan and chitin contents, which was consistent with the down-regulation of expression of the corresponding biosynthesis genes. Moreover, an elevated immune response stimulated by conidia of the ΔAfcps1 mutant in marrow-derived macrophages (BMMs) during phagocytosis was observed. Thus, our study provided new insights into the function of polysaccharide synthase Cps1, which is necessary for the maintenance of cell wall stability and the adaptation of conidia to the immune response of macrophages in A. fumigatus.

Simultaneous detection of fungal (1,3)-β-d-glucan and procalcitonin using a dual-label time-resolved fluorescence immunoassay

Neonatal infectious diseases are a serious threat to the health of newborns. The aim was to establish a new detection method for the simultaneous measurement of (1,3)-β-d-glucan and procalcitonin in serum for the early screening and efficacy testing of neonatal infectious diseases. We established a sandwich dual-label time-resolved fluorescence immunoassay (TRFIA): anti-(1,3)-β-d-glucan/procalcitonin antibodies immobilized on 96-well plates captured (1,3)-β-d-glucan/procalcitonin antigens and then banded together with the detection antibodies labeled with europium(III) (Eu³⁺ )/samarium(III) (Sm³⁺ ) chelates. Finally, time-resolved fluorometry was used to measure the fluorescence intensity. The linear correlation coefficient (R² ) of the (1,3)-β-d-glucan standard curve was 0.9913, and the R² of the procalcitonin standard curve was 0.9911. The detection sensitivity for (1,3)-β-d-glucan was 0.4 pg/mL (dynamic range: 0.6-90 pg/mL), and the average recovery was 101.55%. The detection sensitivity for procalcitonin was 0.02 ng/mL (dynamic range: 0.05-95 ng/mL), and the average recovery was 104.61%. There was a high R² between the present TRFIA method and a commercially available assay (R²  = 0.9829 for (1,3)-β-d-glucan and R²  = 0.9704 for procalcitonin). Additionally, the cutoff values for (1,3)-β-d-glucan and procalcitonin were 23.95 pg/mL and 0.055 ng/mL, respectively. The present TRFIA method has high sensitivity, accuracy, and specificity and is an effective method for early screening and efficient testing of neonatal invasive fungal infection.

Mannan detecting C-type lectin receptor probes recognise immune epitopes with diverse chemical, spatial and phylogenetic heterogeneity in fungal cell walls

During the course of fungal infection, pathogen recognition by the innate immune system is critical to initiate efficient protective immune responses. The primary event that triggers immune responses is the binding of Pattern Recognition Receptors (PRRs), which are expressed at the surface of host immune cells, to Pathogen-Associated Molecular Patterns (PAMPs) located predominantly in the fungal cell wall. Most fungi have mannosylated PAMPs in their cell walls and these are recognized by a range of C-type lectin receptors (CTLs). However, the precise spatial distribution of the ligands that induce immune responses within the cell walls of fungi are not well defined. We used recombinant IgG Fc-CTLs fusions of three murine mannan detecting CTLs, including dectin-2, the mannose receptor (MR) carbohydrate recognition domains (CRDs) 4–7 (CRD4-7), and human DC-SIGN (hDC-SIGN) and of the β-1,3 glucan-binding lectin dectin-1 to map PRR ligands in the fungal cell wall of fungi grown in vitro in rich and minimal media. We show that epitopes of mannan-specific CTL receptors can be clustered or diffuse, superficial or buried in the inner cell wall. We demonstrate that PRR ligands do not correlate well with phylogenetic relationships between fungi, and that Fc-lectin binding discriminated between mannosides expressed on different cell morphologies of the same fungus. We also demonstrate CTL epitope differentiation during different phases of the growth cycle of Candida albicans and that MR and DC-SIGN labelled outer chain N-mannans whilst dectin-2 labelled core N-mannans displayed deeper in the cell wall. These immune receptor maps of fungal walls of in vitro grown cells therefore reveal remarkable spatial, temporal and chemical diversity, indicating that the triggering of immune recognition events originates from multiple physical origins at the fungal cell surface.

Invasive fungal infections remain an important health problem in immunocompromised patients. Immune recognition of fungal pathogens involves binding of specific cell wall components by pathogen recognition receptors (PRRs) and subsequent activation of immune defences. Some cell wall components are conserved among fungal species while other components are species-specific and phenotypically diverse. The fungal cell wall is dynamic and capable of changing its composition and organization when adapting to different growth niches and environmental stresses. Differences in the composition of the cell wall lead to differential immune recognition by the host. Understanding how changes in the cell wall composition affect recognition by PRRs is likely to be of major diagnostic and clinical relevance. Here we address this fundamental question using four soluble immune receptor-probes which recognize mannans and β-glucan in the cell wall. We use this novel methodology to demonstrate that mannan epitopes are differentially distributed in the inner and outer layers of fungal cell wall in a clustered or diffuse manner. Immune reactivity of fungal cell surfaces was not correlated with relatedness of different fungal species, and mannan-detecting receptor-probes discriminated between cell surface mannans generated by the same fungus growing under different conditions. These studies demonstrate that mannan-epitopes on fungal cell surfaces are differentially distributed within and between the cell walls of fungal pathogens.

Diagnosis of invasive fungal disease in children: a narrative review

Introduction: Invasive fungal diseases (IFD) represent important causes of morbidity and mortality in pediatrics. Early diagnosis and treatment of IFD is associated with better outcome and this entails the need to use fast and highly sensitive and specific methods that can support clinicians in the management of IFD.Areas covered: A narrative review was performed on conventional diagnostic methods such as culture, microscopy and histopathology are still gold standard but are burdened by a lack of sensitivity and specificity; on the other hand, imaging and noninvasive antigen-based such as beta-D-glucan, galactomannan and molecular biomarkers are the most convenient nonculture methods for diagnosis and monitoring effects of therapy. Aim of the present review is to summarize what is available in these fields at end of the second decade of the third millennium and look for future perspectives.Expert opinion: Promising and useful diagnostic methods have been applied in infectious disease diagnosis in clinical practice or in designing platforms. Unfortunately, most of them are not standardized or validated in pediatric population. However, clinicians should be aware of all innovative diagnostic tools to use in combination with conventional diagnostic methods for a better management of pathology and patient.

Role of serum (1,3)-β-d-glucan assay in early diagnosis of invasive fungal infections in a neonatal intensive care unit

OBJECTIVES

To study the microbiological pattern of late onset neonatal sepsis cultures and to assess the diagnostic performance of serum (1,3)-β-d-glucan level for early diagnosis of invasive fungemia in high-risk infants admitted to a neonatal intensive care unit.

METHODS

A prospective multicenter clinical trial conducted on infants at high risk for invasive fungal infections, with suspected late onset sepsis, admitted to a neonatal intensive care unit at Mansoura University Children's Hospital and Mansoura General Hospital between March 2014 and February 2016.

RESULTS

A total of 77 newborn infants with high risk of invasive fungal infection were classified based on blood culture into three groups: no fungemia (41 neonates with proven bacterial sepsis), suspected fungemia (25 neonates with negative blood culture), and definite fungemia group (11 neonates with culture-proven Candida). The growing organisms were Klebsiella spp. (14/54); Escherichia coli (12/54); Staphylococcus spp. (12/54; coagulase-negative Staphylococcus [9/54]; Staphylococcus aureus [3/54]); Pseudomonas aerouginosa (3/54); and Proteus spp. (2/54). Moreover, 11/54 presented Candida. Serum (1,3)-β-d-glucan concentration was significantly lower in the no fungemia group when compared with the definite fungemia group. The best cut-off value of (1,3)-β-d-glucan was 99pg/mL with sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 63.6%, 95.1%, 77.8%, 90.7%, and 88.5%, respectively.

CONCLUSION

(1,3)-β-d-glucan assay has a limited sensitivity with excellent specificity and negative predictive value, which allow its use as an aid in exclusion of invasive neonatal fungal infection. Accurate diagnosis and therapeutic decisions should be based on combining (1,3)-β-d-glucan assay with other clinical, radiological, and microbiological findings.

False-positive elevation of 1,3-beta-D-glucan caused by continuous administration of penicillin G

The 1,3-beta-D-Glucan (BDG) assay is widely used for the diagnosis of fungal infections, especially in patients with hematologic malignancies. Some antimicrobials have been reported to cause false-positive results for BDG, but there has been no report on the effect of penicillin G (PCG) on BDG levels. We experienced a patient who developed false-positive BDG elevation during the administration of PCG for osteomyelitis due to Streptococcus pneumoniae infection. The serum BDG level increased up to 81.0 pg/ml during the continuous administration of PCG at 24 million units per day. However, chest and paranasal CT scan showed no evidence of fungal infection. The BDG level decreased to 38.0 pg/ml at 14 hours after the discontinuation of PCG. The amount of BDG in one vial of PCG inferred from these serum BDG levels is very similar to the actual BDG concentration in a vial of PCG. Therefore, during the administration of PCG, elevated BDG levels should be interpreted with caution, as they may be false-positive results.

The diagnostic performance of the beta-glucan assay in the detection of intra-amniotic infection with Candida species

INTRODUCTION

A bioassay based on the detection of beta-glucan, a constituent of the cell wall of fungi, has been successfully used to diagnose fungal infections in a variety of biological fluids but not yet in the amniotic fluid.

OBJECTIVE

To determine the diagnostic performance of a beta-glucan bioassay in the detection of Candida species in the amniotic fluid of women who either did or did not have an intrauterine contraceptive device (IUD) in place during an episode of spontaneous preterm parturition.

METHODS

The study population comprised women who had a singleton pregnancy without congenital or chromosomal abnormalities, who experienced preterm labor or preterm prelabor rupture of the fetal membranes, and who underwent a transabdominal amniocentesis for clinical indications. Samples of amniotic fluid were cultured for aerobic and anaerobic bacteria, genital mycoplasmas, and Candida species, and assayed for beta-glucan, using the (1→3)-beta-d-glucan-specific Limulus amebocyte lysate test (beta-glucan assay) in all cases. Amniotic fluid interleukin (IL)-6 assay results were also available for all cases. The beta-glucan assay takes about 1 hour to run: a concentration >80 pg/mL was considered positive for fungi. Sterile intra-amniotic inflammation of the amniotic cavity was defined by the presence of an amniotic fluid IL-6 concentration ≥2.6 ng/mL and a negative amniotic fluid culture.

RESULTS

(1) One hundred ninety-seven (197) women met the study criteria, of whom 58 (29.4%) had an IUD in place; (2) 20 (10.2%) women had a culture of proven intra-amniotic Candida species-related infection, 19 of whom had a positive beta-glucan assay [sensitivity, 95% (19/20; 95% confidence interval (CI): 75.1-99.9%)]; and (3) the specificity of the beta-glucan assay was 75.1% [133/177; 95% CI: 68.1-99.9%]. It was affected by the presence of nonfungal intra-amniotic infections and an IUD, but not by the presence of sterile intra-amniotic inflammation, and there was a significant interaction between the presence of an IUD and nonfungal intra-amniotic infections (estimated for the interaction effect = 2.1923, p value =.026). The assay's specificity was reduced when nonfungal intra-amniotic infections were diagnosed but only in women who did not have an IUD. Among women without an IUD, the assay's specificity was 91.4% (117/128); it was 93% (106/114) for those without intra-amniotic infection, and 78.6% (11/14) for those with a nonfungal intra-amniotic infection; the difference was not significant (p = .09). Among women with an IUD, the assay's specificity was 32.7% (16/49); 42.9% (9/21) for those with a nonfungal intra-amniotic infection; and 25% (7/28) for those without intra-amniotic infection; and the difference was significant (p = .03).

CONCLUSIONS

The beta-glucan assay is a sensitive, rapid, point-of-care test used to diagnose intra-amniotic Candida species-related infection, and it has a high specificity in pregnant women who did not have an IUD in place.

Evaluation of the diagnostic performance of panfungal polymerase chain reaction assay in invasive fungal diseases

Timely diagnosis of invasive fungal diseases (IFDs) is important, as delays in treatment initiation are associated with increased mortality rates. However, early diagnosis of IFDs in immunocompromised patients remains difficult. The conventional diagnostic methods currently used for IFDs are not sufficiently effective. Molecular tests, such as polymerase chain reaction (PCR)-based assays, have great potential to improve the early diagnosis of IFDs due to their sensitivity and specificity. In the present study, the diagnostic performance of panfungal PCR assays in IFD patients who received bone marrow transplantation was evaluated. The results suggested that panfungal PCR assay offered a quick and convenient guide for clinical decision-making by identifying higher numbers of fungal species in comparison with the conventional blood culture method. Furthermore, panfungal PCR assay exhibited a sensitivity of 93% and a specificity of 71% in the diagnosis of IFD patients based on the EORTC/MSG criteria. Thus, the present study concluded that the reported PCR-based method was effective and sensitive in early IFD diagnosis and should be integrated into clinical decision-making for the treatment of IFDs in the future.

Voriconazole-refractory invasive aspergillosis

Invasive aspergillosis (IA) is one of the most common life-threatening complications in immunocompromised patients. Voriconazole is currently the drug of choice for IA treatment. However, some patients with IA suffer clinical deterioration despite voriconazole therapy. Management of voriconazole-refractory IA remains challenging; no useful recommendations have yet been made. Voriconazole-refractory IA can be further categorized as disease attributable to misdiagnosis or co-infection with another mold; inadequate blood voriconazole blood; inadequate tissue drug concentrations attributable to angioinvasion; immune reconstitution inflammatory syndrome; or infection with voriconazole-resistant Aspergillus. Hence, when encountering a case of voriconazole-refractory IA, it is necessary to schedule sequential tests to decide whether medical treatment or surgical intervention is appropriate; to adjust the voriconazole dose via drug monitoring; to seek CYP2C19 polymorphisms; to monitor serum galactomannan levels; and to examine the drug susceptibility of the causative Aspergillus species.

Persistent spontaneous fungal peritonitis secondary to Candida albicans in a patient with alcoholic cirrhosis and review of the literature

Candida albicans is a common human pathogen. Occasionally, it can cause peritonitis in immunocompromised and postsurgical patients. We report a case of a male patient who presented with abdominal pain and distention. He had a history of end-stage liver disease secondary to alcoholism. His peritoneal fluid culture revealed C albicans, and (1-3)-β-d glucan (BDG) level was elevated. His hospital course was complicated by sepsis and renal failure. He was treated with antifungals for spontaneous fungal peritonitis. Fungal peritonitis should be suspected in patients with chronic liver disease particularly with elevated BDG levels.

Diagnosis of invasive fungal diseases in pediatric patients

INTRODUCTION

The optimal management of invasive fungal infections (IFIs) in children requires prompt and precise diagnosis that enables timely implementation of appropriate antifungal therapy and decreased use of unnecessary toxic antifungals. Areas covered: Traditional approaches such as culture, microscopy and histopathology remain the gold standard but are often not sufficiently sensitive and specific. These limitations have led to the development of alternative non-invasive diagnostic methods that in most cases detect fungal components, such as antigens or nucleic acids. To date, galactomannan and 1,3 β-D-glucan assays are the most efficient non-culture methods for diagnosis and monitoring of antifungal therapy. New technologies from nano-sciences are applied, like T2Candida assay. However, these are not standardized or validated in children. Herein, we focus on IFI diagnosis emphasizing current perspectives, interpretation difficulties, and need for further evaluation in pediatrics. Expert commentary: The new diagnostic tools may enhance diagnostic capacity in combination with traditional methods.

Evaluation of serum (1 → 3)-β-D-glucan clinical performance: kinetic assessment, comparison with galactomannan and evaluation of confounding factors

PURPOSE

We investigated the clinical performance of (1 → 3)-β-D-glucan (BG), as an early marker of invasive fungal infections (IFI), in different clinical settings.

METHODS

BG serum levels were assessed by Fungitell (Associates of Cape Cod, Inc), in parallel with galactomannan (GM) when requested by clinicians. By a prospective monocentric study, 270 episodes at risk or with suspect of IFI were enrolled, namely 58 proven-probable invasive aspergillosis (IA), 27 proven invasive candidiasis (IC), 11 possible IC, 16 P.jirovecii pneumonia (PJP), 4 episodes of other IFI and 154 non-IFI controls.

RESULTS

We found that (a) the BG overall sensitivity, specificity, positive predictive value and negative predictive value (NPV) were 87.9, 80.5, 76.7 and 89.9 %, respectively; (b) the highest sensitivity was found in the IC groups, followed by PJP, IA and other IFI groups; (c) an association was observed between BG kinetics and patients outcome; (d) in the IA episodes, the combination of BG or GM vs GM alone increased sensitivity from 60.0 to 83.3 % in the haematological patients; (e) false-positive BG results were related to Gram-negative infections or infusion of polyclonal IgM-enriched immunoglobulins, where high levels of BG were indeed detected.

CONCLUSION

Besides strengthening its overall good clinical performance, we provide evidence that serum BG correlates with clinical outcome and that, once used in combination with GM, BG allows to enhance IFI diagnosis rate. The high sensitivity and NPV, observed in the Intensive Care Unit setting, open to BG validation as a marker for assessment of antifungal treatment.

The Screening Performance of Serum 1,3-Beta-D-Glucan in Patients with Invasive Fungal Diseases: A Meta-Analysis of Prospective Cohort Studies

The serum 1,3-beta-D-glucan (BG) assay aids in the early diagnosis of invasive fungal diseases (IFDs) and has been approved for their diagnosis. However, reports on the screening performance of BG are scarce. We performed a meta-analysis of data extracted from only prospective cohort studies to evaluate the screening performance of the BG assay in the diagnosis of IFDs. We specifically searched 4 databases (the PubMed, Web of Science, Elsevier, and Cochrane Collaboration databases) according to EORTC-MSG criteria. A total of 1068 patients in 11 studies were analyzed. Deeks’ funnel plot asymmetry test suggested a low likelihood of publication bias for the included studies (p = 0.055). The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the summary receiver operating characteristic curve, with 95% confidence intervals, were 0.75(0.63,0.84), 0.87(0.81,0.92), 5.85(3.96,8.63), 0.30(0.20,0.45), 19.53(11.16,34.18), and 0.89(0.86,0.91), respectively. The findings of this meta-analysis suggest that the BG assay is a useful screening tool with high sensitivity and specificity for discriminating between patients with and without IFDs. In clinical practice, BG assay results should be evaluated together with clinical and microbiological findings.

Reliability of serum 1,3-beta-D-glucan assay in patients undergoing renal replacement therapy: a review of the literature

The serum 1,3-beta-D-glucan (BDG) test is a pan-fungal serum marker considered to detect the majority of pathogenic fungi, including Aspergillus spp. and Candida spp. For this review we searched for publications dealing with serum BDG levels in patients undergoing renal replacement therapy (RRT). The influence of various different membrane materials used for RRTs in these publications on serum BDG has been reviewed. We found that unmodified cellulose containing membranes increased the serum BDG levels highly, whereas conflicting results have been observed for modified cellulose containing materials. Synthetic materials (e.g. polysuflone) had no influence on serum BDG levels in the majority of the reviewed publications.

Routine Use of a Protease Zymogen-Based Colorimetric Assay for the Detection of Beta-Glucan and its Role in Clinical Practice

The detection of Aspergillus antigen (galactomannan) is considered a reliable marker for the diagnosis of invasive aspergillosis (IA), yet the sensibility and specificity of the assays commonly employed in routine are not optimal. The aim of the present study was to investigate whether the detection of another panfungal antigen, the (1,3)-b-D-glucan could have an auxiliary role in the identification of patients with IA. The study was carried out on 63 sera belonging to patients who had been screened for galactomannan, according to the clinical suspect of IA. Our data show that the positive galactomannan results were not confirmed by positive (1,3)-b-D-glucan results in patients receiving therapy with beta-lactam antibiotics associated with tazobactam, whereas in all the other cases, with the exception of four, the results of the (1,3)-b-D-glucan test were confirmatory of the galactomannan results.

Prospective observational multicenter study to define a diagnostic algorithm for biliary candidiasis

AIM: To develop an algorithm to improve the diagnosis and treatment of patients with biliary candidiasis.

METHODS: We performed a prospective study of 127 patients who underwent endoscopic retrograde cholangiopancreatography, for various biliary disorders, at 3 tertiary referral centers in Germany from July 2011 through July 2012 (ClinicalTrials.gov: NCT01109550). Bile, buccal, and stool samples were collected. When indicated, endoscopic transpapillary bile duct biopsies were performed to clarify the etiology of bile duct strictures and to prove invasive fungal infections.

RESULTS: Candida species were detected in 38 of the 127 bile samples (29.9%). By multivariate analysis patients’ age and previous endoscopic sphincterotomy were independent risk factors for biliary candidiasis (P < 0.05). Patients with immunosuppression (P = 0.058) and recent long-term antibiotic therapy (> 7 d) (P = 0.089) tend to be at risk for biliary candidiasis. One patient was negative in mycological culture of bile fluid but invasive biliary candidiasis was diagnosed histologically. Of Candida subspecies detected, 36.7% were azole-resistant, such as C glabrata. Eight patients received anti-mycotic therapy, based on our algorithm. Of these, 3 had cancer with biliary tract involvement, 2 had secondary sclerosing cholangitis, 1 had retroperitoneal fibrosis, and 5 had septicemia. In all patients contamination was ruled out by smears of the endoscope channel.

CONCLUSION: Gastroenterologists should be aware of frequent candida colonization in patients with cholangitis and biliary disorders. Our suggested algorithm facilitates the further clinical management.

Serum 1,3-beta-d-glucan for antifungal treatment stratification at the intensive care unit and the influence of surgery

The purpose of this study was to evaluate a preemptive approach with serum 1,3-beta-d-glucan (BDG) as a marker for treatment stratification of systemic antifungal (AF) therapy in patients with clinical suspected invasive fungal infections (IFI) at intensive care units (ICU), and the impact of surgical procedures. A total of 66 ICU patients with clinical suspected IFI were included in this retrospective analysis. Serum BDG testing was performed prior to initiation of AF treatment and in addition to routine diagnostic measures. Based on the BDG results the initial clinical decision whether or not to start systemic AF therapy was re-evaluated. Impact of surgical procedures on clinical utility of serum BDG was evaluated in a sub-group of 25 patients who had undergone surgical procedures prior to BDG evaluation. BDG test results led to discontinuation of AF therapy in 13 patients, and initiation of AF therapy in seven patients. In 46 patients the clinical decision was confirmed by BDG. The majority of suspected, probable and proven IFI cases (10/13, 77%) was predicted by the test. BDG testing turned out positive in 9/25 (36%) of patients that had undergone recent surgery and levels correlated with clinical findings. Serum BDG evaluation seems to be a promising tool to guide AF therapy in ICU patients even after recent surgical procedures.

Experimental murine acremoniosis: an emerging opportunistic human infection

Acremonium is an emerging fungal pathogen causing severe infections. We evaluated the virulence of three clinically relevant species within the genus, i.e., Acremonium kiliense (currently Sarocladium kiliense), Acremonium sclerotigenum-A. egyptiacum complex and Acremonium implicatum in a murine model of disseminated infection. Both immunocompetent and immunosuppresssed mice were infected with two inocula concentrations (2 × 10(6) and 2 × 10(8) conidia/animal) of two strains of each species. Tissue burden, mortality rate, histopathology and levels of (1→3)-β-D-glucan were used as virulence markers. None of the species of Acremonium tested was able to cause infection in immunocompetent mice. Conversely, severe infections were produced in immunocompromised mice, the spleen being the most affected organ. In general, the virulence of the Acremonium species tested was low, S. kiliense being the most virulent species.

Invasive candidiasis serological diagnosis in solid organ transplant recipients

Solid organ transplant recipients are at high risk of fungal infections, because of ongoing immunosuppressive treatment. There are three post organ transplant phases: early, intermediate, and late, all of them at risk of Candida infections. Since conventional tests are insufficient, specific secondary diagnostic tests are still being explored. Serological tests are currently the most common choice. The present study was to determine the usefulness of mannan antigen and anti-mannan antibody detection in diagnosing invasive candidiasis in liver or kidney transplant recipients. The levels of mannan and anti-mannan antibodies were assessed with Platelia Candida Ag Plus, and Platelia Candida Ab Plus (Biorad, Marne-la-Coquette, France) commercial tests, according to manufacturer's guidelines. Sixty six serum samples were obtained from 25 patients (9 liver transplant recipients, 7 kidney transplant recipients, and 9 patients prepared for a kidney transplant), 29 serum samples from 15 patients tested positive for mannan antigen. Serum samples were obtained from 14 patients tested positive for anti- mannan antibodies. Fungal antigen detection in blood serum in patients under immunosuppression, especially with neutropenia, suggests that antifungal treatment should be administered. Serological tests, especially mannan and anti-mannan ones, are very useful for confirmation or exclusion of invasive candidiasis in high-risk patients.

Evaluation of the efficacies of Amphotericin B, Posaconazole, Voriconazole, and Anidulafungin in a murine disseminated infection by the emerging opportunistic Fungus Sarocladium (Acremonium) kiliense

We evaluated and compared the efficacies of different antifungal drugs against Sarocladium kiliense (formerly Acremonium kiliense), a clinically relevant opportunistic fungus, in a murine model of systemic infection. Three clinical strains of this fungus were tested, and the therapy administered was as follows: posaconazole at 20 mg/kg of body weight (twice daily), voriconazole at 40 mg/kg, anidulafungin at 10 mg/kg, or amphotericin B at 0.8 mg/kg. The efficacy was evaluated by prolonged animal survival, tissue burden reduction, and (1→3)-β-d-glucan serum levels. In general, the four antifungal drugs showed high MICs and poor in vitro activity. The efficacy of the different treatments was only modest, since survival rates were never higher than 40% and no drug was able to reduce fungal load in all the organs for the three strains tested. Posaconazole, in spite of its high MICs (≥16 μg/ml), showed the highest efficacy. The (1→3)-β-d-glucan serum levels were equally reduced by all drugs evaluated.

Adjuvant effect of zymosan after pulmonary treatment in a mouse ovalbumin allergy model

An association has been observed between indoor mold contamination and lung allergy and asthma. This relationship is not fully understood. 1→3-β-Glucan is the major cell wall component of fungi and a good marker of fungi exposure. The objective was to evaluate the adjuvant effect of zymosan, a crude yeast cell wall preparation of 1→3-β-glucan, during ovalbumin (OVA) sensitization in an allergy model. BALB/c mice were sensitized by pharyngeal aspiration with saline, 50 μg of OVA, or OVA with 1, 10, 50, or 75 μg of zymosan on days 0, 7, and 14. One week after sensitization, each sensitized animal group was challenged with an aspiration dose of 50 μg of OVA once a week for 2 weeks. At 1 day after the last aspiration, bronchoalveolar lavage fluid and blood was collected, and markers of lung allergy and inflammation were assessed. An adjuvant effect of zymosan on OVA allergy during sensitization was observed as indicated by significant elevations in lung eosinophils, serum OVA-specific IgE, and lung IL-5 in the groups sensitized with zymosan and OVA. Pulmonary treatment with zymosan also amplified lung inflammation. Elevations were observed in lung neutrophils, TNF-α, and parameters of lung injury in the groups primed with both zymosan and OVA. In nearly all parameters, a non-linear dose-response relationship was observed in the groups primed with OVA and zymosan. The optimum adjuvant dose of zymosan was 10 μg. This study demonstrated an adjuvant effect of zymosan when exposures occurred during the sensitization phase in an OVA-induced allergy model in BALB/c mice.

Reactivity of the 1,3-β-D-glucan assay during bacteraemia: limited evidence from a prospective study

There are discrepancies in the retrospective studies published in literature of whether or not bacteraemia could lead to false positivity of 1,3-β-D (BG) glucan assay. We performed, for the first time, a prospective study evaluating the role of bacterial bloodstream infection to the reactivity of BG assay. Twenty-six episodes of bacteraemia that occurred in high-risk haematological patients were included in our study. Consecutive BG levels >80 pg ml(-1) were required for test positivity. Only 2 of 26 patients were BG positive - both with IFDs. Thus, we prospectively did not prove bacteraemia as the source of cross reactivity of BG assay in haematological patients.

Vaccination with mannan protects mice against systemic aspergillosis

Invasive aspergillosis is a major cause of mortality in immunocompromised patients and therapeutic options are often limited, thus a vaccine would be desirable. We presently studied acid-stable cell-wall mannan (α-1, 6-linked backbone highly branched with α-1, 2; α-1, 3; and β-1, 2-linked manno-oligomers) derived from C. albicans, with or without conjugation to bovine serum albumin (BSA), as a vaccine against systemic aspergillosis. Mice were vaccinated subcutaneously with mannan or mannan-BSA conjugate weekly 3 times, ending 2 weeks prior to infection with A. fumigatus conidia. Results showed that the protection induced by mannan is dose-dependent; 12 mg unconjugated mannan alone or > 0.3 mg mannan-BSA consistently enhanced survival (P < 0.05). Fungal burdens in brains and kidneys were reduced after > 0.3 mg of mannan-BSA (all P < 0.05). Mannan-induced protection was improved about 40-fold by conjugation of BSA to mannan. Mannan-BSA (500 kDa) was more protective than 40 kDa mannan-BSA. Mannan is a candidate for a cross-protective conjugate fungal vaccine.

What should be the optimal cut-off of serum 1,3-β-D-glucan for the detection of invasive pulmonary aspergillosis in patients with haematological malignancies?

BACKGROUND

The detection of 1,3-β-d-glucan (BDG), a cell wall component of several medically important fungi, is a promising tool for the diagnosis of invasive pulmonary aspergillosis. The aim of this study was to evaluate the diagnostic accuracy of the BDG test in invasive pulmonary aspergillosis (IPA) by focusing on the optimal cut-off value.

METHODS

The records of the Infection Control Committee were reviewed to identify patients with haematological malignancies and stem cell transplantation who had at least 1 BDG (Fungitell kit) measurement during the period January 2008 through April 2011. The European Organization for Research and Treatment of Cancer and the Mycoses Study Group (EORTC/MSG) criteria (independent of BDG results) were used to categorize the patients with IPA. Patients with possible IPA were not included in the study.

RESULTS

A total of 128 patients (50 with proven or probable IPA) were included in the study. At the manufacturer's recommended cut-off value of 80 pg/ml, the sensitivity of BDG was 66% (95% CI 51.2-78.7), specificity 75.6% (95% CI 64.6-84.5), positive predictive value (PPV) 63.4%, and negative predictive value (NPV) 77.6%. A receiver operating characteristic (ROC) curve was constructed to define the optimum serum BDG cut-off for the diagnosis of IPA. At a cut-off value of 181 pg/ml, the sensitivity was 52% (95% CI 37.4-66.3), specificity 94.8% (95% CI 87.4-98.6), PPV 86.7%, and NPV 75.5%.

CONCLUSIONS

Although higher cut-off levels increased the specificity of the BDG test, sensitivity decreased to an unacceptable level; the commercially recommended cut-off value appears to be appropriate for screening purposes.

Diagnostic accuracy of serum 1,3-β-D-glucan for pneumocystis jiroveci pneumonia, invasive candidiasis, and invasive aspergillosis: systematic review and meta-analysis

Serum 1,3-β-d-glucan (BG) assay may be helpful as a marker for the diagnosis of Pneumocystis jiroveci pneumonia (PJP) and invasive fungal infection (IFI). We conducted a systematic review to assess the diagnostic accuracy of this assay. We searched MEDLINE, Web of Science, Cochrane Collaboration databases, Ichushi-Web, reference lists of retrieved studies, and review articles. Our search included studies of serum BG assay that used (i) positive cytological or direct microscopic examination of sputum or bronchoalveolar lavage fluid for PJP and (ii) European Organization for Research and Treatment of Cancer or similar criteria for IFI as a reference standard and provided data to calculate sensitivity and specificity. Only major fungal infections such as invasive candidiasis and invasive aspergillosis were included in the IFI group. Twelve studies for PJP and 31 studies for IFI were included from January 1966 to November 2010. The pooled sensitivity, specificity, diagnostic odds ratio (DOR), and area under the summary receiver operating characteristic curve (AUC-SROC) for PJP were 96% (95% confidence interval [95% CI], 92% to 98%), 84% (95% CI, 83% to 86%), 102.3 (95% CI, 59.2 to 176.6) and 0.96 (95% CI, 0.94 to 0.99), respectively. No heterogeneity was found. For IFI, the values were 80% (95% CI, 77% to 82%), 82% (95% CI, 81% to 83%), 25.7 (95% CI, 15.0 to 44.1), and 0.88 (95% CI, 0.82 to 0.93). Heterogeneity was significant. The diagnostic accuracy of the BG assay is high for PJP and moderate for IFI. Because the sensitivity for PJP is particularly high, the BG assay can be used as a screening tool for PJP.

Does ampicillin-sulbactam cause false positivity of (1,3)-beta-D-glucan assay? A prospective evaluation of 15 patients without invasive fungal infections

The purpose of this study was to investigate the interaction between intravenous ampicillin-sulbactam treatment and (1,3)-beta-D-glucan (BDG) assay. Fifteen patients with a median age of 60 (16-81) without known risk factors for invasive fungal infections who received a daily dose of 3×2g ampicillin-sulbactam monotherapy from different batches were included in the study. Thirteen patients had soft tissue infections. The 5 of 13 patients who went under surgery had surgical dressings. Serum samples were obtained both before and after antibiotic infusion on the first, third, seventh and tenth days of an ampicillin-sulbactam treatment course. BDG was assayed using the Fungitell kit (Associates of Cape Cod, East Falmouth, MA, USA) according to manufacturers' specifications. All serum samples were also tested for galactomannan (GM) antigenemia by Platelia Aspergillus ELISA (Bio-Rad Laboratories, Marnes-la-Coquette, France). A total of 37 of 117 serum samples were positive for BDG at a threshold of 80pg ml(-1) . Seven of 37 BDG positive serum samples had a GM index ≥0.5. When a cutoff value of ≥0.5 was used for GM positivity, 16 (13.3%) serum samples were positive. For a cutoff value of ≥0.7, eight (6.6%) serum samples were positive. There were no statistically significant differences in the median BDG levels (P=0.47) or median GM indices (P =0.28) of the various sampling times. None of the SAM vials tested positive for BDG or GM. After ruling out fungal infections and all known potential causes of false BDG positivity, environmental contamination remained possible cause of BDG reactivity. We did not observe any significant association of ampicillin-sulbactam administration and positive assays for BDG or GM.

Value of (1-3)-β-d-glucan, Candida mannan and Candida DNA detection in the diagnosis of candidaemia

This study determined the value of (1,3)-β-d-glucan (BDG), Candida mannan (MN) and Candida species-specific DNA as surrogates for diagnosis of candidaemia. Thirty-nine patients yielding Candida species in blood cultures were investigated for presence of BDG, MN and Candida species-specific DNA in serum samples. The Candida spp. bloodstream isolates included C. albicans (n = 16), C. tropicalis (n = 10), C. parapsilosis (n = 7), C. glabrata (n = 3) and C. dubliniensis (n = 3). Positivity of the three markers was as follows: Candida DNA for corresponding Candida species, 100%; BDG, 87%; MN, 59%. Despite varying sensitivities of these biomarkers, they provided a useful adjunct to the diagnosis of candidaemia.

Serum 1,3-βD-Glucan assay in the diagnosis of invasive fungal disease in neonates

Invasive fungal disease is a significant cause of morbidity and mortality in the neonate. The current study aims to assess the 1, 3-βD-Glucan (BG) assay in a prospective analysis in neonates with suspected fungaemia. A multicentre, prospective cohort study was conducted in Johannesburg, South Africa. The study included 72 neonates with clinically suspected late onset sepsis who were at high risk of fungaemia. A BG assay was performed on each patient and correlated with a sepsis classification based on the full blood count, C-reactive protein and blood culture results as no fungaemia, possible fungaemia, probable fungaemia or definite fungaemia. Sensitivity and specificity of the BG assay at levels of 60 pg/mL are 73.2% and 71.0% respectively and at levels of 80 pg/mL are 70.7% and 77.4% respectively. Positive and negative predictive values at 60 pg/mL are 76.9% and 66.7% respectively and at 80 pg/mL are 80.6% and 66.7% respectively. The area under the receiver operating curve is 0.753. The BG assay is a useful adjunct to the diagnosis of invasive fungal disease in neonates. It does, however, need to be considered in the context of the clinical picture and supplementary laboratory investigations.

Novel strategies for the prevention and treatment of Candida infections: the potential of immunotherapy

Infections caused by Candida spp. continue to be a substantial cause of disease burden, especially in immunocompromised patients. New approaches are needed to improve the outcome of patients suffering from Candida infections, because it seems unlikely that the established standard treatment will drastically lower the morbidity of mucocutaneous Candida infections and the high mortality associated with invasive candidiasis. New insights into the mechanisms of the anti-Candida host response have contributed to the design of novel immunotherapeutic approaches that have been proposed as adjuvant therapy in Candida infections. This review presents an overview of novel strategies in the prevention and treatment of Candida infections, with a special focus on adjuvant immunotherapy.

The use of mannan antigen and anti-mannan antibodies in the diagnosis of invasive candidiasis: recommendations from the Third European Conference on Infections in Leukemia

Introduction

Timely diagnosis of invasive candidiasis (IC) remains difficult as the clinical presentation is not specific and blood cultures lack sensitivity and need a long incubation time. Thus, non-culture-based methods for diagnosing IC have been developed. Mannan antigen (Mn) and anti-mannan antibodies (A-Mn) are present in patients with IC. On behalf of the Third European Conference on Infections in Leukemia, the performance of these tests was analysed and reviewed.

Methods

The literature was searched for studies using the commercially available sandwich enzyme-linked immunosorbent assays (Platelia™, Bio-Rad Laboratories, Marnes-la-Coquette, France) for detecting Mn and A-Mn in serum. The target condition of this review was IC defined according to 2008 European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria. Sensitivity, specificity and diagnostic odds ratios (DOR) were calculated for Mn, A-Mn and combined Mn/A-Mn testing.

Results

Overall, 14 studies that comprised 453 patients and 767 controls were reviewed. The patient populations included in the studies were mainly haematological and cancer cases in seven studies and mainly intensive care unit and surgery cases in the other seven studies. All studies but one were retrospective in design. Mn sensitivity was 58% (95% confidence interval [CI], 53-62); specificity, 93% (95% CI, 91-94) and DOR, 18 (95% CI 12-28). A-Mn sensitivity was 59% (95% CI, 54-65); specificity, 83% (95% CI, 79-97) and DOR, 12 (95% CI 7-21). Combined Mn/A-Mn sensitivity was 83% (95% CI, 79-87); specificity, 86% (95% CI, 82-90) and DOR, 58 (95% CI 27-122). Significant heterogeneity of the studies was detected. The sensitivity of both Mn and A-Mn varied for different Candida species, and it was the highest for C. albicans, followed by C. glabrata and C. tropicalis. In 73% of 45 patients with candidemia, at least one of the serological tests was positive before the culture results, with mean time advantage being 6 days for Mn and 7 days for A-Mn. In 21 patients with hepatosplenic IC, 18 (86%) had Mn or A-Mn positive test results at a median of 16 days before radiological detection of liver or spleen lesions.

Conclusions

Mn and A-Mn are useful for diagnosis of IC. The performance of combined Mn/A-Mn testing is superior to either Mn or A-Mn testing.

Invasive pulmonary aspergillosis due to Aspergillus terreus: value of DNA, galactomannan and (1→3)-β-d-glucan detection in serum samples as an adjunct to diagnosis

A case of invasive pulmonary aspergillosis caused by Aspergillus terreus is described. The diagnosis was based on demonstration of branched septate hyphae in a sputum specimen and isolation of the fungus in culture. The diagnosis was further supported by detection of A. terreus-specific DNA, galactomannan (GM) and (1→3)-β-d-glucan (BDG) in consecutive serum specimens. The patient was treated for about 10 weeks with voriconazole. The decreasing levels of GM and BDG in serum samples were accompanied by symptomatic and radiological improvement. The report highlights the value of surrogate markers in the diagnosis and for monitoring the course of invasive aspergillosis during therapy.

Difficulties in using 1,3-β-d-glucan as the screening test for the early diagnosis of invasive fungal infections in patients with haematological malignancies – high frequency of false-positive results and their analysis

We have evaluated the contribution of the 1,3-β-d-glucan (BG) assay for the screening of invasive fungal infections (IFIs) in patients with haematological malignancies. Serum samples from patients at risk of IFI were collected twice a week and retrospectively tested using the BG assay. BG screening was performed on 1143 samples from 91 patients during 104 anticancer treatment cycles. Proven and probable cases of IFI occurred in 9 (8.7 %) treatment cycles. Depending on the criterion of positivity used (1× >60 pg ml−1, 1× >80 pg ml−1, 2× >60 pg ml−1 or 2× >80 pg ml−1) the sensitivity and specificity were 89, 89, 67 and 44 %, and 20, 48, 33 and 56 %, respectively. Although the test was marked as positive in 82, 68, 54 and 45 % of all the treatment cycles, in the majority of cases, these positivities were probably false. The major limit of the BG test was an extremely low positive predictive value (10 to 12 %). We have analysed mucositis, candida colonization, bacteraemia, use of antimicrobials, erythrocyte and thrombocyte filtered blood products, collecting tubes or sampling via venous catheters. Even though no factor is a major source of BG, it could at least partially influence BG assay performance. Thus, BG detection has a limited usefulness as a screening method for IFIs in patients with haematological malignancies.

No interference of the 1,3-β-D-glucan containing nutritional supplement ImunixX with the 1,3-β-D-glucan serum test

The detection of 1,3-β-D-glucan serum levels may permit establishing the diagnosis of invasive fungal infections more early. We tested in six healthy volunteers whether the intake of a 1,3-β-D-glucan-containing nutritional supplement leads to false-positive 1,3-β-D-glucan levels. All levels were negative, even in two different dosing regimens.