Experimental proof of contamination of blood components by (1?3)-?-D-glucan caused by filtration with cellulose filters in the manufacturing process

Biosafety consideration of nanocellulose in biomedical applications: A review

Nanocellulose-based biomaterials have gained significant attention in various fields, especially in medical and pharmaceutical areas, due to their unique properties, including non-toxicity, high specific surface area, biodegradability, biocompatibility, and abundant feasible and sophisticated strategies for functional modification. The biosafety of nanocellulose itself is a prerequisite to ensure the safe and effective application of biomaterials as they interact with living cells, tissues, and organs at the nanoscale. Potential residual endogenous impurities and exogenous contaminants could lead to the failure of the intended functionalities or even serious health complications if they are not adequately removed and assessed before use. This review summarizes the sources of impurities in nanocellulose that may pose potential hazards to their biosafety, including endogenous impurities that co-exist in the cellulosic raw materials themselves and exogenous contaminants caused by external exposure. Strategies to reduce or completely remove these impurities are outlined and classified as chemical, physical, biological, and combined methods. Additionally, key points that require careful consideration in the interpretation of the biosafety evaluation outcomes were discussed to ensure the safety and effectiveness of the nanocellulose-based biomaterials in medical applications.

Challenges with Utilizing the 1,3-Beta-d-Glucan and Galactomannan Assays To Diagnose Invasive Mold Infections in Immunocompromised Children

Establishing the diagnosis of invasive mold infections (IMI) in immunocompromised children is challenging due to nonspecific clinical presentations and the limited sensitivity of traditional culture-based methods. Rapid non-culture-based diagnostics such as the 1,3-beta-d-glucan and galactomannan assays have emerged as promising adjuncts to conventional diagnostic tests in adults. Available data suggest that 1,3-beta-d-glucan has limited accuracy in the pediatric population and is not recommended to be used for the diagnosis of IMI in children. On the other hand, the diagnostic performance of the serum and bronchoalveolar lavage galactomannan in immunocompromised children is comparable to results observed in adults and can be used as a screening tool in children at high risk of developing invasive aspergillosis (IA) who are not receiving mold-active antifungal prophylaxis and as a diagnostic tool in symptomatic children suspected of having IA. Herein, we summarize the available evidence for the use of these rapid non-culture-based diagnostics in immunocompromised children. We also summarize potential causes of false positivity for the 1,3-beta-d-glucan and galactomannan assays.

Plasma 1,3-β-d-glucan levels predict adverse clinical outcomes in critical illness

BACKGROUNDThe fungal cell wall constituent 1,3-β-d-glucan (BDG) is a pathogen-associated molecular pattern that can stimulate innate immunity. We hypothesized that BDG from colonizing fungi in critically ill patients may translocate into the systemic circulation and be associated with host inflammation and outcomes.METHODSWe enrolled 453 mechanically ventilated patients with acute respiratory failure (ARF) without invasive fungal infection and measured BDG, innate immunity, and epithelial permeability biomarkers in serially collected plasma samples.RESULTSCompared with healthy controls, patients with ARF had significantly higher BDG levels (median [IQR], 26 pg/mL [15-49 pg/mL], P < 0.001), whereas patients with ARF with high BDG levels (≥40 pg/mL, 31%) had higher odds for assignment to the prognostically adverse hyperinflammatory subphenotype (OR [CI], 2.88 [1.83-4.54], P < 0.001). Baseline BDG levels were predictive of fewer ventilator-free days and worse 30-day survival (adjusted P < 0.05). Integrative analyses of fungal colonization and epithelial barrier disruption suggested that BDG may translocate from either the lung or gut compartment. We validated the associations between plasma BDG and host inflammatory responses in 97 hospitalized patients with COVID-19.CONCLUSIONBDG measurements offered prognostic information in critically ill patients without fungal infections. Further research in the mechanisms of translocation and innate immunity recognition and stimulation may offer new therapeutic opportunities in critical illness.FUNDINGUniversity of Pittsburgh Clinical and Translational Science Institute, COVID-19 Pilot Award and NIH grants (K23 HL139987, U01 HL098962, P01 HL114453, R01 HL097376, K24 HL123342, U01 HL137159, R01 LM012087, K08HK144820, F32 HL142172, K23 GM122069).

Development of a Highly Sensitive β-Glucan Detection System Using Scanning Single-Molecule Counting Method

To overcome the limitations of the Limulus amebocyte lysate (LAL) assay method for the diagnosis of invasive fungal infection, we applied a reaction system combining recombinant β-glucan binding proteins and a scanning single-molecule counting (SSMC) method. A novel (1→3)-β-D-glucan recognition protein (S-BGRP) and a (1→6)-β-glucanase mutant protein were prepared and tested for the binding of (1→6)-branched (1→3)-β-D-glucan from fungi. S-BGRP and (1→6)-β-glucanase mutant proteins reacted with β-glucan from Candida and Aspergillus spp. Although LAL cross-reacted with plant-derived β-glucans, the new detection system using the SSMC method showed low sensitivity to plant (1→3)-β-D-glucan, which significantly improved the appearance of false positives, a recognized problem with the LAL method. Measurement of β-glucan levels by the SSMC method using recombinant β-glucan-binding proteins may be useful for the diagnosis of fungal infections. This study shows that this detection system could be a new alternative diagnostic method to the LAL method.

Efficacy of Cerebrospinal Fluid Beta-d-Glucan Diagnostic Testing for Fungal Meningitis: a Systematic Review

Several case reports and cohort studies have examined the use of (1,3)-beta-d-glucan measurement with cerebrospinal fluid to diagnose fungal meningitis. This systematic review aims to characterize the evidence regarding cerebrospinal fluid (1,3)-beta-d-glucan measurement to detect fungal meningitis. We searched PubMed for (1,3)-beta-d-glucan and each of several distinct fungi, cerebrospinal fluid, and meningitis. Summary data including diagnostic performance (where applicable) were recorded. A total of 939 records were examined via a PubMed search. One hundred eighteen records remained after duplicates were removed, and 104 records were excluded, as they did not examine cerebrospinal fluid, included animals, or focused on nonfungal infections. Fourteen studies were included in this systematic review. A variety of fungi, including species of Candida, Aspergillus, Exserohilum, Cryptococcus, Histoplasma, and Coccidioides, were studied, although most were case reports. Diagnostic accuracy was examined in 5 studies. Cerebrospinal fluid (CSF) (1,3)-beta-d-glucan measurement showed >95% sensitivity in the corticosteroid injection-related outbreak of Exserohilum rostratum One study in Histoplasma meningitis found 53% (53/87) sensitivity and 87% (133/153) specificity, while another study of Cryptococcus meningitis found 89% (69/78) sensitivity and 85% (33/39) specificity. CSF (1,3)-beta-d-glucan testing may be useful, primarily as a nonspecific marker of fungal meningitis. Although the FDA black box warning states that Cryptococcus spp. do not make (1,3)-beta-d-glucan, the current evidence shows that (1,3)-beta-d-glucan is detectable in cryptococcal meningitis. Organism-specific testing should be used in conjunction with (1,3)-beta-d-glucan measurement.

Point-Counterpoint: Should Serum β-d-Glucan Testing Be Used for the Diagnosis of Pneumocystis jirovecii Pneumonia?

INTRODUCTIONDespite the widespread use of prophylactic antibiotics in high-risk individuals, Pneumocystis jirovecii remains an important cause of pneumonia in immunocompromised patients. During the peak of the AIDS epidemic, many hospitals and outpatient clinics were very proficient at collecting induced sputum specimens for the diagnosis of Pneumocystis jirovecii pneumonia (PJP). With the dramatic reduction in the occurrence PJP in the current era of highly effective antiretroviral therapy, many centers no longer collect induced sputum samples. Thus, the diagnosis of PJP requires bronchoalveolar lavage (BAL) specimens or a decision to treat the patient empirically without a definitive diagnosis. Sputum or BAL specimens are tested for P. jirovecii using special stains or molecular assays, which require highly trained staff that may not be available with a rapid turnaround time. Given the invasive nature of collecting BAL specimens and the expertise needed for interpreting PJP test results, there is interest in using serum 1,3-β-d-glucan (BDG) testing for the diagnosis of PJP. In this point-counterpoint, Luis Ostrosky-Zeichner and Gabriela Corsi-Vasquez discuss the pro view of using BDG testing for the diagnosis of PJP, while Paul E. Sax and Edward F. Pilkington III present the con view of using BDG testing for the diagnosis of PJP.

Potentially Immunogenic Contaminants in Wood-Based and Bacterial Nanocellulose: Assessment of Endotoxin and (1,3)-β-d-Glucan Levels

Knowledge gaps in the biosafety data of the nanocellulose (NC) for biomedical use through various routes of administration call for closer look at health and exposure evaluation. This work evaluated the potentially immunogenic contaminants levels, for example, endotoxin and (1,3)-β-d-glucan, in four representative NCs, that is, wood-based NCs and bacterial cellulose (BC). The hot-water extracts were analyzed with ELISA assays, HPSEC-MALLS, GC, and NMR analysis. Varying levels of endotoxin and (1,3)-β-d-glucan contaminats were found in these widely used NCs. Although the β-(1,3)-d-glucan was not detected from the NMR spectra due to the small extract samples amount (2-7 mg), the anomerics and highly diastereotopic 6-CH₂ signals may suggest the presence of β-(1,4)-linkages with β-(1,6) branching in the polysaccharides of NCs' hot-water extracts, which were otherwise not detectable in the enzymatic assay. In all, the article highlights the importance of monitoring various water-soluble potentially immunogenic contaminants in NC for biomedical use.

Use of 1,3-β-D-glucan in invasive fungal diseases in hematology patients

INTRODUCTION

Invasive fungal diseases (IFD) remain a leading cause of morbidity and mortality in hematology patients. Within a diagnostic-driven approach, the use of the serum (1,3)-ß-D-glucan (BDG) test represents a valid tool for the early diagnosis and treatment of IFD. Areas covered: The available literature on the use of BDG in hematology patients was systematically retrieved. Then, it was reviewed and discussed, to identify key issues pertaining to a clinically-oriented narrative presentation of the topic. Expert commentary: The use of BDG in hematology patients at risk for invasive aspergillosis (IA) is secondary to the use of galactomannan. However, since BDG is not specific for IA, it offers an advantage of diagnosing also other IFD, such as candidiasis and pneumocystosis. The limitations of BDG include high costs and lower sensitivity in hematology patients compared to other cohorts. The risk of false positive results is possibly lower in real life than in theory, since glucan-free equipment is available and modern dialysis membranes and blood products usually do not release BDG. Thus, in experienced hands and selected clinical situations, BDG is a useful diagnostic tool, particularly due to short turnover time to results and versatility in diagnosing different IFD.

On importance of impurities, potential leachables and extractables in algal nanocellulose for biomedical use

Nanocellulose-based biomaterials for biomedical and pharmaceutical applications have been extensively explored. However, studies on different levels of impurities in the nanocellulose and their potential risks are lacking. This article is the most comprehensive to date survey of the importance and characterization of possible leachables and extractables in nanocellulose for biomedical use. In particular, the (1,3)-β-d-glucan interference in endotoxin detection in algal nanocellulose was addressed. Potential lipophilic and hydrophilic leachables, toxic heavy metals, and microbial contaminants are also monitored. As a model system, nanocellulose from Cladophora sp. algae is investigated. The leachable (1,3)-β-d-glucan and endotoxin, which possess strong immunogenic potential, from the cellulose were minimized to clinically insignificant levels of 4.7μg/g and 2.5EU/g, respectively. The levels of various impurities in the Cladophora cellulose are acceptable for future biomedical applications. The presented approach could be considered as a guideline for other types of nanocellulose.

Comparison of quality of human serum albumin preparations in two pharmaceutical products

Aim

Human serum albumin (HSA) is known for its multiple functions, such as maintenance of colloid osmotic pressure, transport of endogenous and exogenous substances, and antioxidation. The aim of this study was to measure the redox state and concentrations of β‐d‐glucan and endotoxin to compare the quality of 5% HSA preparations from two different manufacturers.

Methods

The quality of 5% HSA preparations in two different pharmaceutical products (groups A and B) was compared in terms of the percentage of reduced and oxidized albumin and the contaminant level of β‐d‐glucan and endotoxin.

Results

The percentage of human mercaptoalbumin in group A was significantly higher than that in group B (P < 0.01), whereas that of human non‐mercaptoalbumin‐2 in group A was significantly lower (P < 0.01). The concentration of β‐d‐glucan in group A was significantly lower than in group B (P < 0.01).

Conclusions

The present findings indicate the need for quality control of HSA preparations in applications involving the use of large volumes.

Usage of 1,3-β-D-Glucan for Early Detection of Invasive Mycoses and Outcome Parameter in Immunocompromised Critically Ill Patients

INTRODUCTION

Invasive fungal disease (IFD) remains a significant cause of morbidity and mortality in critically ill patients.

METHODS

Examination of 1,3-β-D-glucan (BDG) for IFD and as outcome parameter in immunocompromised critically ill patients with septic shock.

RESULTS

Thirty-two (69 %) out of 46 included patients had BDG beyond the cutoff of >80 pg/ml (mean 320 pg/ml). Twelve (37 %) had findings of Aspergillus spp. in BAL (mean BDG 413 pg/ml). EORTC/MSG guidelines classified these as probable invasive aspergillosis (IA)/IFD. Five (16 %) had candidaemia (mean BDG level 361 pg/ml). Sensitivity of 78 % (95 % CI 58-88 %) and specificity of 68 % (95 % CI 52-77 %) for IFD were found on the BDG Fungitell assay. In detail, a sensitivity of 73 % (95 % 58-84 %) and specificity of 83 % (95 % CI 68-93 %) for IA and a sensitivity of 77 % (CI 95 % 62-87 %) and specificity 53 % (95 % CI 37-73 %) for candidaemia were found. APACHE II, SOFA score and mortality rate were in the elevated BDG group significantly altered (26 vs. 21, p < 0.003; 15 vs. 13, p < 0.006; 72 vs. 50 %, p < 0.004).

CONCLUSION

1,3-β-D-glucan assay is helpful for early detection of IFD; moreover, elevated BDG levels can be used as a predictor for outcome in immunocompromised critically ill patients as presented in our study.

β-Glucans in standardized allergen extracts

Background: Allergen extracts contain variable quantities of bacterial endotoxin. Recent studies have suggested that (1→3)-β-D-glucans (β-glucans), also microbial cell wall components, may have adjuvant properties that could affect allergen immunotherapy.

Objective: To determine the quantities of β-glucans in standardized allergen extracts.

Materials and Methods : Ninety-four lots of 13 standardized allergen extracts were tested for β-glucan content by Glucatell assay, and for endotoxin content by a specific, chromogenic formulation of the Limulus amebocyte lysate test.

Results: Standardized allergen extracts contain variable quantities of endotoxins and β-glucans. As in our previous work, endotoxin activity was greatest in cat pelt and Dermatophagoides farinae, and least in the pollens. There was no correlation between endotoxin and β-glucan levels ( r = 0.1887; P = 0.07). β-Glucan content was highest for grass pollen (median content, 10.6 ng/ml; range, 0.4—41.8 ng/ml), ragweed pollen (32.9 ng/ml; range, 6.5—41.2 ng/ml), and cat pelt (25.5 ng/ml; range, 16.7—41.1 ng/ml), and lowest for cat hair (4.9 ng/ml; range, 1.2—10.3 ng/ml), D. farinae (1.2 ng/ml; range, 0.4—5.2 ng/ml) and Dermatophagoides pteronyssinus (1.8 ng/ml; range, 0.4—6.7 ng/ml).

Conclusions: β-Glucans are present in standardized allergen extracts. The effects of these quantities of β-glucans on allergen immunotherapy and allergen skin testing require further study.

Comparison of 1,3-β-d-glucan with galactomannan in serum and bronchoalveolar fluid for the detection of Aspergillus species in immunosuppressed mechanical ventilated critically ill patients

PURPOSE

Invasive pulmonary aspergillosis (IPA) is an important cause of morbidity/mortality in immunocompromised critically ill patients. New diagnostic strategies for early detection of IPA include the noninvasive biomarkers 1,3-β-d-glucan (BDG), serum, and bronchoalveolar (BAL) fluid galactomannan (GM). The aim of this study was to compare these markers for early detection of IPA in immunosuppressed critically ill patients.

METHODS

Between December 2014 and December 2015, 49 immunosuppressed patients with respiratory failure were treated at our intensive care unit (ICU). We compared the BDG Fungitell assay with GM Platelia assay in serum and BAL for early detection of IPA. All tests were performed initially after admission at the ICU.

RESULTS

In our study with 49 patients, 13 (26%) had probable IPA. These patients had a higher Acute Physiology And Chronic Health Evaluation II score (28 vs 23, P<.001), Sequential Organ Failure Assessment score (16 vs 14, P<.001), more neutropenia (77% vs 30%, P<.001), worse Horowitz Index (99 vs 73 P<.020), a longer ICU stay (26 vs 17 days, P<.044), and a higher mortality rate (77% vs 58%, P<.001) as compared with patients without probable IPA. The used biomarker BDG presented in patients with probable IPA showed significantly higher levels as compared with patients without probable IPA (375 [103-1000 pg/mL; P<.001] vs 64 [30-105 pg/mL; P < .001]). Comparison of BDG with GM showed that positive serum GM could be detected in only 4 (30%), whereas positive BAL GM could be detected in 12 (92%; mean optical density index, 3.7) of 13 probable IPA cases. These results can be expressed as an overall sensitivity of 88% and a specificity of 82% for probable IPA using the BDG Fungitell assay, a sensitivity of 35% and a specificity of 70% using the serum GM Platelia assay, and a sensitivity of 70% and a specificity of 94% using the BAL GM Platelia assay. The negative predictive values of the used tests were 94% for the BDG Fungitell assay, 94% for the serum GM Platelia assay, and 90% for the BAL GM Platelia assay.

CONCLUSION

1,3-β-d-Glucan may be a useful marker for patients under surveillance at risk for IPA. In critically ill patients with immunosuppression, early diagnosis of IPA may be improved by BDG as compared with serum GM. However, diagnostic performance and accuracy increase when BDG is run in parallel with GM from BAL; moreover, the association of the 2 parameters has also the advantage of detecting early and reliable IPA.

Soluble β-(1,3)-glucans enhance LPS-induced response in the monocyte activation test, but inhibit LPS-mediated febrile response in rabbits: Implications for pyrogenicity tests

In the present study, we aimed to determine the influence of β-(1,3)-d-glucans on the LPS-induced pro-inflammatory cytokine response in the Monocyte Activation Test (MAT) for pyrogens, and on the LPS-induced febrile response in the Rabbit Pyrogen Test (RPT), thus evaluating the resulting effect in the outcome of each test. It was found that β-(1,3)-d-glucans elicited the production of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α, also known as endogenous pyrogens, but not enough to classify them as pyrogenic according to MAT. The same β-(1,3)-d-glucans samples were non-pyrogenic by RPT. However, β-(1,3)-d-glucans significantly enhanced the LPS-induced pro-inflammatory cytokines response in MAT, insomuch that samples containing non-pyrogenic concentrations of LPS become pyrogenic. On the other hand, β-(1,3)-d-glucans had no effect on sub-pyrogenic LPS doses in the RPT, but surprisingly, inhibited the LPS-induced febrile response of pyrogenic LPS concentrations. Thus, while β-(1,3)-d-glucans could mask the LPS pyrogenic activity in the RPT, they exerted an overstimulation of pro-inflammatory cytokines in the MAT. Hence, MAT provides higher safety since it evidences an unwanted biological response, which is not completely controlled and is overlooked by the RPT.

Combination of Candida biomarkers in patients receiving empirical antifungal therapy in a Spanish tertiary hospital: a potential role in reducing the duration of treatment

OBJECTIVES

Initiation of empirical antifungal therapy for invasive candidiasis (IC) is usually based on clinical suspicion. Serological biomarkers have not yet been studied as a means of ruling out IC. We evaluated the potential role of two combined biomarkers in stopping unnecessary antifungals in patients at risk of IC in the ICU and in other wards.

METHODS

This was a prospective observational study including adults starting empirical antifungal treatment for suspected IC, at Gregorio Marañón Hospital, Madrid (Spain). Patients were stratified according to admission department (ICU or other wards) and final diagnosis (no IC or proven or probable IC). Type of candidiasis (candidaemia or deep-seated candidiasis) was also considered. The Candida albicans germ tube antibody (CAGTA) test and the β-d-glucan (BDG) test were performed on serum samples collected by venepuncture on days 0, 3 and 5 after starting empirical antifungal therapy.

RESULTS

Sixty-three ICU patients and 37 non-ICU patients were included. High-risk gastrointestinal surgery and sepsis in non-surgical patients were the main indications for empirical treatment (30% each). Patients had no IC (58%), proven IC (30%) or probable IC (12%). Overall, sensitivity and negative predictive value of the combination of both the CAGTA test and the BDG test were 97% for the entire population. The best performance was observed in ICU patients (sensitivity and negative predictive value of 100%). Among patients without IC, all biomarkers were negative in 31 patients.

CONCLUSIONS

Serial determination of CAGTA/BDG during empirical antifungal therapy has a high sensitivity and negative predictive value. If properly confirmed, this strategy could be used to discontinue antifungal treatment in at least 31% of patients as a complementary tool in antifungal stewardship programmes.

How to interpret serum levels of beta-glucan for the diagnosis of invasive fungal infections in adult high-risk hematology patients: optimal cut-off levels and confounding factors

Detection of the fungal cell wall component beta-glucan (BG) in serum is increasingly used to diagnose invasive fungal infections (IFI), but its optimal use in hematology patients with high risk of IFI is not well defined. We retrospectively analyzed the diagnostic accuracy, optimal cut-off level, and potential confounding factors of BG reactivity. The inclusion criteria were: adult patients with hematologic disease who were admitted to the hematology ward during the 2-year study period and who had two or more consecutive BG assays performed. In total, 127 patients were enrolled. Thirteen patients with proven or probable IFI, as defined by the 2008 European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) criteria, were identified. Receiver operating characteristic (ROC) curve analysis showed a high overall diagnostic performance (area under the ROC curve = 0.98) and suggested an optimal cut-off level of 158 pg/ml, with a sensitivity and a specificity of 92 % and 96 %, respectively. Multiway analysis of variance indicated that treatment with pegylated asparaginase (p < 0.001), admission to the intensive care unit (ICU; p = 0.0007), and treatment with albumin, plasma, or coagulation factors (p = 0.01) are potential confounding factors of BG reactivity. We propose that a higher cut-off level than that recommended by the manufacturer should be used to monitor adult hematology patients at high risk for IFI. Our results also suggest that elevated BG levels in patients treated with pegylated asparaginase, albumin, plasma, or coagulation factors, or those admitted to the ICU should be interpreted with caution.

(1,3)-β-d-glucan in cerebrospinal fluid for diagnosis of fungal meningitis associated with contaminated methylprednisolone injections

Prompt diagnosis and treatment of fungal meningitis are critical, but culture is insensitive. (1,3)-β-d-Glucan (BDG) testing is FDA approved for serological diagnosis of invasive fungal disease; however, BDG testing is not approved for cerebrospinal fluid (CSF), and the appropriate cutoff value is unknown. We aimed to validate the diagnostic accuracy of CSF BDG measurements for fungal meningitis among patients exposed to contaminated methylprednisolone acetate (MPA). A retrospective observational study was conducted at St. Joseph Mercy Hospital and Vanderbilt University from November 2013 to February 2014. Patients were included if they had received a contaminated MPA injection. Cases were classified as probable or proven meningitis according to Centers for Disease Control and Prevention guidelines. CSF BDG testing was performed according to the package insert instructions for serum samples, and results were validated using Clinical and Laboratory Standards Institute procedures (MiraVista Diagnostics). Of 233 patients, 45 had meningitis (28 proven cases), 53 had spinal/paraspinal infections (19 proven cases), and 135 did not develop disease. Using the manufacturer's cutoff value (≥80 pg/ml), the sensitivity and specificity were 96% and 95%, respectively, for proven meningitis and 84% and 95% for probable or proven meningitis. Receiver operating characteristic analysis identified the optimal cutoff value for proven meningitis to be 66 pg/ml (sensitivity, 100%; specificity, 94%) and that for probable or proven meningitis to be 66 pg/ml (sensitivity, 91%; specificity, 92%). Our results suggest that CSF BDG measurements are highly sensitive and specific for the diagnosis of fungal meningitis associated with contaminated MPA injections. Further study on the utility of CSF BDG testing for other types of fungal meningitis is needed.

Cross-reactivity of Nocardia spp. in the fungal (1-3)-β-d-glucan assay performed on cerebral spinal fluid

Cerebral spinal fluid from a patient affected by a brain abscess caused by Nocardia abscessus gave a positive result for (1-3)-β-d-glucan (BG) assay, in absence of any fungal infection. This study aimed to assess whether Nocardia spp. show cross-reactivity with BG assay. All Nocardia spp. analyzed provided positive reactions.

Interference of confounding factors on the use of (1,3)-beta-D-glucan in the diagnosis of invasive candidiasis in the intensive care unit

Invasive fungal infections (IFIs) are an increasing problem in intensive care units (ICUs), and conventional diagnostic methods are not always reliable or timely enough to deliver appropriate antimicrobial therapy. The dosage of fungal antigens in serum is a promising diagnostic technique, but several confounding factors, such as treatment with immunoglobulins (Ig), albumin, or antifungals, could interfere with the correct interpretation of the (1,3)-beta-D-glucan (BG) assay. This study assessed the reliability of the BG assay and the influence of timing and dosage of major confounding factors on circulating levels of IFI biomarkers. 267 ICU patients who underwent a BG assay were retrospectively studied. The timing and dosage of albumin, use of azole treatment, and infusions of intravenous IgG, red blood cells, concentrated platelets, and frozen plasma were analyzed to find possible correlations with the BG results. The sensitivity and specificity of the BG assay were calculated. The BG test in serum showed high sensitivity (82.9 %) but low specificity (56.7 %). The optimal cut-off for the test was 95.9 pg/mL. The mean BG level in proven invasive candidiasis was around 400 pg/mL. The only factor that was found to significantly confound (p < 0.05) the diagnostic performance of the BG assay was the administration of more than 30 g of albumin within 2 days prior to BG testing. The BG assay remains a useful diagnostic test in ICU patients and the levels of BG are useful in evaluating the positive predictive value of this biomarker. The only confounding factor in our study was the use of albumin.

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

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

What is the role of the (1→3)-β-D-glucan assay in the screening of patients undergoing autologous haematopoietic stem-cell transplantation?

The aim of this study is to determine the clinical contribution of (1→3)-β-d-glucan (BDG) screening in the case of patients undergoing autologous haematopoietic stem-cell transplantation (HSCT). The records at our stem-cell transplantation centre were reviewed to identify the patients who underwent autologous HSCT between April 2009 and December 2010. Patients were classified as having proven invasive aspergillosis (IA), probable IA, or possible IA on the basis of the criteria established by the European Organization for Research and Treatment of Cancer and Mycoses Study Group (independent of the BDG results). During the study period, the patients were screened for BDG twice a week from transplant (day 0) until engraftment. Three patients were diagnosed with probable IA and five were diagnosed with possible IA. A total of 354 serum samples from 79 patients who met the study inclusion criteria were used for statistical analysis. At the cut-off value of 80 pg ml(-1) , the sensitivity was 27.2% [95% confidence interval (CI); 7.3-60.6]; specificity, 94.4% (95% CI; 91.3-96.5); positive predictive value, 6.2%; and negative predictive, 93.7%. The clinical contribution of the BDG assay as a screening test was relatively limited in this cohort of patients undergoing autologous HSCT.

β-D-glucan surveillance with preemptive anidulafungin for invasive candidiasis in intensive care unit patients: a randomized pilot study

BACKGROUND

Invasive candidiasis (IC) is a devastating disease. While prompt antifungal therapy improves outcomes, empiric treatment based on the presence of fever has little clinical impact. Β-D-Glucan (BDG) is a fungal cell wall component detectable in the serum of patients with early invasive fungal infection (IFI). We evaluated the utility of BDG surveillance as a guide for preemptive antifungal therapy in at-risk intensive care unit (ICU) patients.

METHODS

Patients admitted to the ICU for ≥ 3 days and expected to require at least 2 additional days of intensive care were enrolled. Subjects were randomized in 3:1 fashion to receive twice weekly BDG surveillance with preemptive anidulafungin in response to a positive test or empiric antifungal treatment based on physician preference.

RESULTS

Sixty-four subjects were enrolled, with 1 proven and 5 probable cases of IC identified over a 2.5 year period. BDG levels were higher in subjects with proven/probable IC as compared to those without an IFI (117 pg/ml vs. 28 pg/ml; p<0.001). Optimal assay performance required 2 sequential BDG determinations of ≥ 80 pg/ml to define a positive test (sensitivity 100%, specificity 75%, positive predictive value 30%, negative predictive value 100%). In all, 21 preemptive and 5 empiric subjects received systemic antifungal therapy. Receipt of preemptive antifungal treatment had a significant effect on BDG concentrations (p< 0.001). Preemptive anidulafungin was safe and generally well tolerated with excellent outcome.

CONCLUSIONS

BDG monitoring may be useful for identifying ICU patients at highest risk to develop an IFI as well as for monitoring treatment response. Preemptive strategies based on fungal biomarkers warrant further study.

TRIAL REGISTRATION

Clinical Trials.gov NCT00672841.

Early treatment of candidemia in adults: a review

Invasive candidiasis is associated with high mortality, particularly in adults. Retrospective studies show that shorter times to treatment are correlated with a lower risk of death. A number of factors can be used to predict which patients would benefit from antifungal prophylaxis or early (pre-emptive or empirical) therapy. Detection of the fungal cell wall component (1→3)-β-D-glucan (BDG) shows promise as an early biomarker of invasive fungal infection and may be useful in identifying patients who would benefit from early antifungal treatment. To date, no consistent early treatment strategy has evolved. Proof-of-concept studies are needed to assess the role of pre-emptive and empirical therapy in ICU patients and the relevance of BDG as an early marker of infection.

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.

Measurement of (1-3)-beta-D-glucan derived from different gauze types

(1-3)-beta-D-glucan (BDG) is a cell-wall polysaccharide component found in most fungi. The measurement of BDG is a useful diagnostic marker for invasive fungal infections. However, it is well known that interfering substances can result in false positive reactions. We encountered a patient who underwent lung transplantation and presented with highly elevated BDG values, despite having no evidence of invasive fungal infection. We therefore hypothesized that elevated BDG values were originated from the gauze products used during surgery. While it is known that gauze products contain BDG, there have been no previous reports to quantitatively correlate amount of gauze usage and BDG levels. In this study, we extracted BDG from various gauze products and measured BDG to better understand the degree of which gauze contributes to elevated BDG values. Six types of commonly used surgical gauze products were selected for our study. Each of the surgical gauze was immersed in sterile, purified water for up to 120 minutes. At set intervals, BDG values in the water extracts were measured. Purified water samples without gauze were used as negative controls (< 4 pg/ml). After 120-minute extraction, BDG levels varied greatly depending on gauze products, ranging from 11.7 pg/ml to 6612 pg/ml. The gauze made of lyocell, which is a fiber produced from wood pulp cellulose, yielded the lowest levels of BDG, and probably would not cause false positive for fungal infections. There is a need for the development of a gauze product that does not contribute to elevated BDG values.

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

Early diagnosis of fungal infections and the implementation of appropriate treatment represent major issues for clinicians, nowadays. Histopathological demonstration of microorganisms in tissue specimens or growth of fungal agents in culture media is still considered the "gold standard", but obtaining such specimens may be difficult. Several groups have investigated serological assays for cell wall elements unique to fungal organisms in serum or other body fluids to improve diagnostics in patients with haematological malignancies or undergoing haematopoietic stem-cell transplantation. In this review we have concentrated on the currently available assays allowing for detection of highly immunogenic components of fungal cell wall: galactomannan, mannan, and also (1-->3)-beta-D-glucan. Rapid serological tests appear to be useful for screening high-risk haematological patients, since they allow for the early diagnosis of invasive fungal infections, including infections with the most common pathogens such as Aspergillus and Candida. Based on current literature, factors increasing the probability of obtaining false-positive or false-negative results detected by each test were also analysed and tabulated.

Potentiation of Toll-like receptor-induced cytokine production by (1-->3)-beta-D-glucans: implications for the monocyte activation test

The monocyte activation test (MAT) has been introduced as an alternative for the detection of pyrogens in pharmaceuticals with the rabbit pyrogen test or the Limulus amebocyte lysate (LAL) test. The basis of the MAT is that pyrogens, via Toll-like receptors (TLRs) expressed on monocytes, stimulate cytokine production. Here, we report that, at concentrations that did not induce whole blood cytokine production when tested separately, (1-->3)-beta-D-glucans powerfully co-stimulated cytokine production (IL-6/IL-8) induced by ligands for TLR1/2, TLR2/6, TLR4, and TLR5. Experiments were performed to investigate the involvement of particular (1-->3)-beta-D-glucan receptors such as dectin-1. Spleen tyrosine kinase (Syk) inhibition attenuated the potentiating effects of (1-->3)-beta-D-glucans on TLR-induced cytokine production, suggesting that dectin-1 was involved. However, experiments with low molecular (1-->3)-beta-D-glucans such as laminarin argued against the involvement of dectin-1 in the co-stimulatory effects of (1-->3)-beta-D-glucans. Thus, although the receptors involved in the co-stimulatory actions of (1-->3)-beta-D-glucans on TLR-induced cytokine production are yet to be elucidated, it is clear that (1-->3)-beta-D-glucans may greatly affect MAT results and, when undetected in pharmaceuticals, may give rise to serious side-effects in patients co-exposed to other elicitors of innate immunity, such as during infections.

Reactivity of (1-->3)-beta-d-glucan assay with commonly used intravenous antimicrobials

Forty-four intravenous antimicrobials were tested for the presence of (1-->3)-beta-d-glucan (BG). Colistin, ertapenem, cefazolin, trimethoprim-sulfamethoxazole, cefotaxime, cefepime, and ampicillin-sulbactam tested positive for BG at reconstituted-vial concentrations but not when diluted to usual maximum plasma concentrations. False-positive BG assays may occur when some antimicrobials are administered; however, this needs to be confirmed.