Levels of (1→3)-β-D-glucan, Candida mannan and Candida DNA in serum samples of pediatric cancer patients colonized with Candida species

Performance of Multiplex PCR and β-1,3-D-Glucan Testing for the Diagnosis of Candidemia

Bloodstream infections caused by Candida yeasts (candidemia) are associated with high morbidity and mortality. Diagnosis remains challenging, with the current gold standard—isolation from blood culture (BC)—being limited by low sensitivity and long turnaround time. This study evaluated the performance of two nonculture methods: PCR and β-1,3-D-glucan (BDG) testing. The sera of 103 patients with BC-proven candidemia and of 46 controls were analyzed with the Fungiplex Candida Real-Time PCR and the Wako β-Glucan Test. The BDG assay demonstrated higher sensitivity than the multiplex PCR (58% vs. 33%). This was particularly evident in ICU patients (60% vs. 28%) and in C. albicans candidemia (57% vs. 37%). The earlier prior to BC sampling the sera were obtained, the more the PCR sensitivity decreased (46% to 18% in the periods of 0−2 and 3−5 days before BC, respectively), while BDG testing was independent of the sampling date. No positive PCR results were obtained in sera sampled more than five days before BC. Specificities were 89% for BDG and 93% for PCR testing. In conclusion, BDG testing demonstrated several advantages over PCR testing for the diagnosis of candidemia, including higher sensitivity and earlier diagnosis. However, BC remains essential, as BDG does not allow for species differentiation.

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.

Reinvestigation of Carbohydrate Specificity of EBCA-1 Monoclonal Antibody Used for the Detection of Candida Mannan

Monoclonal antibody EBCA-1 is used in the sandwich immune assay for the detection of circulating Candida mannan in blood sera samples for the diagnosis of invasive candidiasis. To reinvestigate carbohydrate specificity of EBCA-1, a panel of biotinylated oligosaccharides structurally related to distinct fragments of Candida mannan were loaded onto a streptavidin-coated plate to form a glycoarray. Its use demonstrated that EBCA-1 recognizes the trisaccharide β-Man-(1→2)-α-Man-(1→2)-α-Man and not homo-α-(1→2)-linked pentamannoside, as was reported previously.

Diagnostic Mycology: Xtreme Challenges

Developing any diagnostic assay that receives United States Food and Drug Administration (FDA) approval can be a slow and difficult process. FDA-approved assays for fungal diagnosis are generally few in number and are focused mainly on diagnosing candidiasis, which is caused by several species of Candida, in addition to a limited number of systemic mycotic agents. While all microbial diagnostic assays face challenges before they are FDA approved and reach the market, there are a number of challenges to fungal diagnostic assay development that have been difficult hurdles to overcome. These hurdles include template preparation, fungal morphology, how many fungi should be identified in a single assay (scope), taxonomy and nomenclature, discriminating colonizers from invasive infection, combining identification with antifungal susceptibility, and navigating the administrative hurdles required to integrate an assay into a clinical laboratory. Some of these challenges are easier to overcome than others, but all seem to be particularly difficult for fungal diagnostic assays.

Colonic mucosa-associated candida assessed by biopsy culture is associated with disease severity in ulcerative colitis: A prospective study

OBJECTIVE

To evaluate the relationship of mucosa-associated candida (MAC) and disease severity in patients with ulcerative colitis (UC).

METHODS

We prospectively investigated the presence, nature, and quantification of MAC in patients with UC and its relationship with disease severity. Consecutive patients with UC were assessed for clinical, endoscopic, histological features and serum markers of disease severity. All patients underwent mucosal brushing cytology, brushing culture, and biopsy culture for candida growth. MAC was considered present if mucosal biopsy culture grew candida. Candida spp. identification was performed by matrix-assisted laser desorption/ionization. Serum β-D-glucan was measured with a Fungitell assay. Patients with irritable bowel syndrome who had undergone similar investigations were included as controls.

RESULTS

Ninety-six patients with UC showed evidence of MAC more often than the controls (n = 20) based on biopsy culture (33.3% vs 5.0%, P = 0.011), brush cytology (30.2% vs 5.0%, P = 0.019), and brush culture (36.5% vs 10.0%, P = 0.021). Patients with UC had higher candida colony counts (≥10³ CFU/mL) than controls (34.4% vs 5.0%, P = 0.007). Median β-D-glucan values were higher in patients with UC than in controls (103.26 pg/mL vs 66.51 pg/mL, P = 0.011). The UC group with MAC had a higher median total Mayo score, C-reactive protein, fecal calprotectin, β-D-glucan, and histological activity than those without MAC.

CONCLUSIONS

Patients with UC more often show evidence of MAC and a higher candida colony count than controls. The presence of MAC is associated with high disease severity in patients with UC.

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.

Fungal infections in pediatric neurosurgery

INTRODUCTION

Invasive mycosis of the central nervous system represent a diverse group of diseases that have gradually emerged as not only opportunistic infections in patients with immune susceptibility due to congenital and acquired deficiency, immunomodulation, solid organ and stem cell transplantation, hematological malignancies, and chronic steroid use but also in selected risk populations such as low weight preterm infants, patients with shunted hydrocephalus and external ventricular drainages, skull base surgery, and head injury.

OBJECTIVES

The purpose of this review is to familiarize the pediatric neurosurgeon with the most common mycosis and their clinical scenarios which can be encountered in the clinical practice, with special emphasis on clinical, radiological, and laboratory diagnosis beyond classical microorganism cultures as well as options in medical and surgical treatment given the high incidence of morbidity and mortality associated with these challenging entities.

METHODS

We conducted an online database review (Ovid, PubMed) gathering relevant English language literature published in the last 20 years with special emphasis on recent breakthroughs in the diagnosis and treatment of invasive mycosis of the CNS as well as reported cases within the pediatric neurosurgical literature and their surgical management.

RESULTS

Fungal agents capable of invading the CNS can behave as aggressive entities with rapid progression manifesting as overwhelming meningoencephalitis with vascular compromise or can lead to space-occupying lesions with abscess formation which require prompt diagnosis by either laboratory identification of the components of these biological agents and their host response or by obtaining tissue specimens for microbiological identification which may not be straightforward due to prolonged culture time.

CONCLUSION

Following a high degree of suspicion with prompt initiation of antifungal agents and reversal of potential immunosuppressant therapies along with neurosurgical evacuation of intracranial collections or removal of infected hardware (CSF shunts) can lead to more optimistic outcomes of these complex clinical scenarios.

Evaluation of the (1,3)-β-D-glucan assay for the diagnosis of neonatal invasive yeast infections

Most newborns in the neonatal intensive care unit (NICU) are premature and at risk of invasive fungal infections (IFIs). Invasive yeast infections (IYIs) are the most common fungal infections in this population. These infections are difficult to diagnose because symptoms are nonspecific, and the sensitivity of blood cultures is low. The serum (1,3)-β-D-glucan (BDG) assay provides a reliable marker for the diagnosis of IFIs in adults with haematological malignancies. We assessed the diagnostic performance of this test in neonatal IYIs and its contribution to the monitoring of antifungal treatment. A retrospective study was performed in the NICU of the French University Hospital of Amiens from February 2012 to February 2014. Forty-seven neonates (33 males, 14 females) with a median gestational age of 30 weeks (IQR: 27-31) and median birth weight of 1200 g (IQR: 968-1700) were included and divided into three groups: 21 control neonates (CTRL), 20 neonates with probable IYI (PB), and six with proven IYI (PV). Median BDG levels were significantly higher in the global IYI group (PB + PV): 149 pg/ml (IQR: 85-364) vs. CTRL group: 39 pg/ml (IQR: 20-94) (P < .001). The optimal cut-off was 106 pg/ml (sensitivity 61.5%; specificity 81%). BDG levels decreased with antifungal treatment. BDG was detectable in cerebrospinal fluid, but the interest of this for diagnostic purposes remains unclear. Our results suggest that the BDG assay may be useful for the early identification of IYIs in neonates and for monitoring antifungal therapy efficacy.

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.

Role of Molecular Biomarkers in the Diagnosis of Invasive Fungal Diseases in Children

Invasive fungal diseases are important clinical problems that are often complicated by severe illness and therefore the inability to use invasive measures to definitively diagnose the disease. Tests for a range of fungal biomarkers that do not require an invasive sample-collection procedure have been incorporated into adult clinical practice, but pediatric data and pediatric-specific recommendations for some of these diagnostic tools are lacking. In this review, we summarize the published literature and contemporary strategies for using the biomarkers galactomannan, (1→3)-β-d-glucan, Candida mannan antigen and anti-mannan antibody, and fungal polymerase chain reaction for diagnosing invasive fungal disease in children. Data on biomarker use in neonates and children with cancer, history of hematopoietic stem cell transplant, or primary immunodeficiency are included. Fungal biomarker tests performed on blood, other body fluids, or tissue specimens represent promising adjuncts to the diagnostic armamentarium in populations with a high prevalence of invasive fungal disease, but substantial gaps exist in the correct use and interpretation of these diagnostic tools in pediatric patients.

Performance of 1,3-β-D-glucan for diagnosing invasive fungal diseases in children

Plasma 1,3-β-D-glucan (BDG) is indicated as a tool for early diagnosis of invasive fungal diseases (IFD). However, data on its diagnostic value are scarce in children. Therefore, definition of BDG test performance in paediatrics is needed. BDG was evaluated in children admitted to "Istituto Giannina Gaslini," Genoa, Italy, who developed clinical conditions at risk for IFD. Results were analysed for sensitivity, specificity, predictive values, likelihood ratios, accuracy, informedness and probability of missing one case by a negative test. A total of 1577 BDG determinations were performed on 255 patients (49% males, median age 5.4 years). Overall 46 IFD were diagnosed, 72% proven/probable. The test performance was evaluated for 80 pg/mL, 120 pg/mL, 200 pg/mL, 350 pg/mL, 400 pg/mL cut offs. Sensitivity was always <0.80 and specificity > 0.90 only for cut offs ≥200 pg/mL. Negative predictive value was ≥0.90 for all the cut offs evaluated, while positive predictive value resulted barely 0.50 (8% IFD prevalence). Accuracy was never >0.90, and informedness was at best 0.50. The risk of missing one IFD by a negative result was < 10%. Analyses in haemato-oncological or newborn patients did not show major differences. Detection of serum BDG does not appear a valuable adjunctive diagnostic tool for IFD in paediatrics.

Performance of a Quantitative PCR-Based Assay and Beta-d-Glucan Detection for Diagnosis of Invasive Candidiasis in Very-Low-Birth-Weight Preterm Neonatal Patients (CANDINEO Study)

An epidemiological, multicenter, noninterventional, observational case-control study was conducted to describe the performance of serum beta-d-glucan (BDG) and Candida PCR in blood, serum, and sterile samples for the diagnosis of invasive candidiasis (IC) in very-low-birth-weight (VLBW) preterm neonates and to compare these techniques with culture of samples from blood and other sterile sites. Seventeen centers participated in the study, and the number of episodes analyzed was 159. A total of 9 episodes of IC from 9 patients (7 confirmed and 2 probable) and 150 episodes of suspected sepsis from 117 controls were identified. The prevalence of IC was 5.7% (95% confidence interval [95% CI], 2.1 to 9.3). The mortality was significantly higher in episodes of IC (44.4%) than in the non-IC episodes (11.1%, P < 0.01). The sensitivity and specificity of the PCR performed on blood/serum samples were 87.5% and 81.6%, respectively. The sensitivity and specificity of the BDG results were lower (75.0% and 64.6%). For cases with negative culture results, the PCR and the BDG results were positive in 27 (17.4%) and 52 (33.5%) episodes, respectively. The presence of multiorgan failure, improvement with empirical antifungal therapy, thrombocytopenia, and Candida colonization were significantly associated (P < 0.01) with PCR or BDG positivity regardless of the results of the cultures. Serum BDG analysis and Candida PCR could be used as complementary diagnostic techniques to detect IC in VLBW neonates.

Progress in the Diagnosis of Invasive Fungal Disease in Children

PURPOSE OF REVIEW

This review summarizes the fungal diagnostic measures currently available for use in paediatric patients at high risk for developing invasive fungal disease (IFD) and those suspected of having an IFD. The clinical utility of each test is described based on reported performances of individual tests in specific paediatric populations.

RECENT FINDINGS

Available studies in the paediatric population are scarce and are characterized by a huge heterogeneity in underlying diseases (e.g. different risk for IFD), different study objectives and management strategies (screening versus diagnostic) used.

SUMMARY

A final valuation of paediatric studies on fungal diagnostic tools is limited. While the galactomannan and fungal PCR assays are useful to exclude the presence of IFD, it is unclear if mannan, mannan antibodies and β-D-glucan are of benefit due to a lack of studies or validation of the cut-off, respectively. Well-designed multicentre paediatric studies are urgently needed to improve the outcome of IFD.

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.

Pediatric Invasive Aspergillosis

Invasive aspergillosis (IA) is a disease of increasing importance in pediatrics due to growth of the immunocompromised populations at risk and improvements in long-term survival for many of these groups. While general principles of diagnosis and therapy apply similarly across the age spectrum, there are unique considerations for clinicians who care for children and adolescents with IA. This review will highlight important differences in the epidemiology, clinical manifestations, diagnosis, and therapy of pediatric IA.

Pediatric Invasive Candidiasis: Epidemiology and Diagnosis in Children

Pediatric patients present with differing underlying conditions and cytotoxic therapeutic protocols, so the differing epidemiology of invasive candidiasis in children versus adults is not surprising. Understanding the Candida species epidemiology is critical, as we often begin empiric therapy or therapy before antifungal susceptibilities are known. Reports with newer molecular diagnostic assays for invasive candidiasis are rare and require more study to develop firm pediatric-specific guidance. Antifungal treatment of pediatric candidiasis is reviewed in the context of larger epidemiologic studies and the few trials completed to date.

β-D-Glucan Screening for Detection of Invasive Fungal Disease in Children Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

While the assessment of β-D-glucan (BDG) levels in adults improves the early diagnosis of invasive fungal disease (IFD), data on BDG levels in children are limited. We therefore assessed in a prospective cohort study the value of serial BDG screening for early detection of IFD in children undergoing allogeneic hematopoietic stem cell transplantation (HSCT). IFD was defined according to the revised European Organization for Research and Treatment of Cancer/Mycosis Study Group (EORTC/MSG) criteria, with the necessary modification that BDG was not included as a microbiological criterion. For the analysis, a total of 702 serum samples were obtained in 34 pediatric HSCT recipients. Proven IFD occurred in two patients (fusariosis and Candida sepsis, respectively), and probable invasive aspergillosis was diagnosed in four patients. Analyses including different cutoff values for BDG levels and different definitions of the onset of IFD demonstrated that the BDG assay has a relatively high sensitivity and good negative predictive value, whereas the positive predictive value has major limitations (<30%). Receiver operating characteristic analyses suggested an optimal cutoff between 60 and 70 pg/ml for different definitions of the onset of IFD. Our data show that BDG screening in pediatric HSCT recipients has a low positive predictive value and is therefore of limited usefulness.

The epidemiology and diagnosis of invasive candidiasis among premature infants

Invasive candidiasis is a leading infectious cause of morbidity and mortality in premature infants. Improved recognition of modifiable risk factors and antifungal prophylaxis has contributed to the recent decline in the incidence of this infection among infants. Invasive candidiasis typically occurs in the first 6 weeks of life and presents with nonspecific signs of sepsis. Definitive diagnosis relies on the growth of Candida in blood culture or cultures from other normally sterile sites, but this may identify fewer than half of cases. Improved diagnostics are needed to guide the initiation of antifungal therapy in premature infants.

Mannosylation in Candida albicans: role in cell wall function and immune recognition

The fungal cell wall is a dynamic organelle required for cell shape, protection against the environment and, in pathogenic species, recognition by the innate immune system. The outer layer of the cell wall is comprised of glycosylated mannoproteins with the majority of these post‐translational modifications being the addition of O‐ and N‐linked mannosides. These polysaccharides are exposed on the outer surface of the fungal cell wall and are, therefore, the first point of contact between the fungus and the host immune system. This review focuses on O‐ and N‐linked mannan biosynthesis in the fungal pathogen Candida albicans and highlights new insights gained from the characterization of mannosylation mutants into the role of these cell wall components in host–fungus interactions. In addition, we discuss the use of fungal mannan as a diagnostic marker of fungal disease.

(1-3)-β-D-glucan levels in candidiasis infections in the critically ill neonate

INTRODUCTION

The diagnosis of neonatal invasive Candida infections (ICIs) is problematic because the clinical signs are not specific and blood cultures are rarely positive. Hence, new diagnostic markers are needed.

OBJECTIVE

To assess the contribution of serum (1-3)-β-d-glucan (BDG) levels to the diagnosis of neonatal ICIs and to analyse the change in this parameter during antifungal therapy.

METHODS

This retrospective study (December 2010-March 2012) was performed at Amiens University Medical Center (Amiens, France). We included newborns in whom a BDG assay was performed for a suspected ICI and classified as infected (n = 18) or non-infected (n = 43).

RESULTS

Sixty-one patients (median (IQR) gestational age: 28.5 weeks (26.7-30.6); birth weight: 1000 g (910-1440)) were included. The BDG level was higher in the infected group (364 pg/ml (131-976) vs. 89 pg/ml (30-127); p < 0.001). The optimal BDG cut-off for distinguishing between non-infected and infected patients was 125 pg/ml (Se = 84%, Sp = 75%). The BDG level fell over the course of antifungal therapy.

CONCLUSION

Our study results suggest that BDG levels were increased in neonatal invasive Candida infections (cut-off for BDG positivity > 125 pg/ml). The change in the serum BDG levels may be of value in evaluating the efficacy of antifungal therapy.

Polymerase chain reaction-based assays for the diagnosis of invasive fungal infections

Currently accepted fungal diagnostic techniques, such as culture, biopsy, and serology, lack rapidity and efficiency. Newer diagnostic methods, such as polymerase chain reaction (PCR)-based assays, have the potential to improve fungal diagnostics in a faster, more sensitive, and specific manner. Preliminary data indicate that, when PCR-based fungal diagnostic assays guide antifungal therapy, they may lower patient mortality and decrease unnecessary antifungal treatment, improving treatment-associated costs and avoiding toxicity. Moreover, newer PCR techniques can identify antifungal resistance DNA loci, but the clinical correlation between those loci and clinical failure has to be studied further. In addition, future studies need to focus on the implementation of PCR techniques in clinical decision making and on combining them with other diagnostic tests. A consensus on the standardization of PCR techniques, along with validation from large prospective studies, is necessary to allow widespread adoption of these assays.

Diagnostic performance of 1→3-β-d-glucan in neonatal and pediatric patients with Candidemia

Fungal sepsis is one of the major problems in neonatal and pediatric care unit settings. The availability of new diagnostic techniques could allow medical practitioners to rapidly identify septic patients and to improve their outcome. The aim of this study was to evaluate the performance of the 1→3-β-d-glucan (BDG), individually and in comparison with the Candida mannan (CM) antigen, in ten preterm infants and five onco-haematological pediatric patients with Candida bloodstream infections already proven by positive culture. The serum levels of BDG were >80 pg/mL on the same day as a positive blood culture in all examined patients, while CM antigen was negative in the patients with C. parapsilosis fungemia and in one further case due to C. albicans. These results suggest that a regular monitoring of serum circulating antigens (i.e., 1→3-β-d-glucan) combined with other microbiological and clinical information, may allow earlier and accurate diagnosis. However, further studies are necessary to confirm its usefulness in routine clinical practice.

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.