Prospective evaluation of mannan and anti-mannan antibodies for diagnosis of invasive Candida infections in patients with neutropenic fever

Detailed β-(1→3)-D-glucan and mannan antigen kinetics in patients with candidemia

Fungal antigens such as β-(1→3)-D-glucan (BDG) or mannan (Mn) are useful for detection of candidemia. However, detailed data on serum levels before diagnosis and during treatment are scarce. We conducted a prospective study at two German tertiary care centers for 36 months. Sera from adult patients with candidemia were tested for BDG (Fungitell assay) and Mn (Platelia Candida Ag-Plus assay). For each patient, the clinical course and biomarker kinetics were closely followed and compared. 1,243 sera from 131 candidemia episodes and 15 relapses were tested. In 35% of episodes, empirical therapy included an antifungal drug. Before blood culture sampling, BDG and Mn levels were elevated in 62.4% and 30.8% of patients, respectively. Sensitivity at blood culture sampling was 78.6% (BDG) and 35.1% (Mn). BDG levels of non-survivors were significantly higher than those of survivors. During follow-up, a therapeutic response was associated with decreasing BDG and Mn levels in 84.3% or 70.5% of episodes, respectively. A median increase of 513 pg BDG/mL and 390 pg Mn/mL indicated a relapse of candidemia with a sensitivity of 80% or 46.7%, respectively. In 72.9% and 46.8% of patients, increasing BDG or Mn levels were associated with a fatal outcome. Prior to discharge, BDG and Mn levels had dropped or normalized in 65.7% or 82.1% of patients, respectively. Summarising, in patients with candidemia, biomarker positivity usually precedes culture positivity. Relapses are mostly accompanied by secondary biomarker increases. Rising concentrations of BDG and Mn predict lethality, whereas decreasing levels suggest a favorable outcome in the majority of patients.

β-(1→3)-D-glucan- and mannan-guided early termination of antifungal therapy in ICU patients: a randomized controlled study

Candida spp. are frequently encountered in specimens from ICUs. However, most of these detections represent colonization. Nevertheless, clinical practice shows that a considerable proportion of these patients will receive antifungal therapy (AT). β-(1→3)-D-glucan (BDG) and mannan are fungal biomarkers with high negative predictive values. We aimed to examine whether biomarker-guided discontinuation of AT can reduce the antifungal consumption. Therefore, we conducted a prospective, randomized intervention study between 1 April 2019 and 31 March 2020. All adult ICU patients with a newly started systemic AT but without fungal infection were eligible for inclusion. Enrolled patients were randomized into an intervention and a control group. In both groups, serum BDG and mannan were determined on days 1 and 2 of AT. If all measurements were negative, AT was discontinued in the intervention group. The primary endpoint was antifungal use. The study was terminated after 12 months. Until this time-point, 41 patients had been included. In the intervention group (n = 19), AT was stopped in only two patients because all others showed either positive BDG and/or mannan levels. One of these two patients developed candidemia and AT had to be restarted. There was no significant difference in the primary and secondary endpoints. In summary, the strategy of using two negative BDG and mannan levels to stop AT failed to reduce antifungal consumption in our cohort. Indeed, there will inevitably be patients with invasive candidiasis in whom necessary AT is discontinued. The optimal patient population, biomarker set, and termination criteria are critical to the success of biomarker-based termination strategies.

Invasive fungal infections in hemato-oncology

BACKGROUND

Patients with hematologic malignancies (HM) carries a significant risk of developing invasive fungal infection (IFI) and are associated with a high risk of attributable morbidity and mortality.

OBJECTIVES

This review has highlighted the importance of diagnosis and management of invasive fungal infections in highly immunocompromised Hemato-Oncology patients.

CONTENT

IFI continues to be a therapeutic issue in immunocompromised HM patients despite of many advancements in the field of fungal diagnosis and therapies. Non-specific and often overlapping signs and symptoms render fungal infections clinically undifferentiated from bacterial infections. Definite diagnosis requires microbiological diagnostic procedures in addition to imaging techniques. Many international committees have formulated definitions to aid in the diagnosis of IFI in immunocompromised patients and assigned 3 levels of probability to the diagnosis "proven," "probable," and "possible" IFI. Early specific risk-based antifungal strategies such as prophylaxis, pre-emptive and empirical therapies, are common practices in HM patients. For low-risk patients, fluconazole is recommended as primary prophylaxis, while, posaconazole and voriconazole are recommended for high-risk patients. Emerging antifungal-resistant IFIs and breakthrough fungal infections are the new threat to these heavily immunosuppressed patients. Antifungal agents such as azoles have variable pharmacokinetics leading to uncertainty in the drug dose-exposure relationship, especially in the initiation phase. TDM (therapeutic drug monitoring) of voriconazole is strongly recommended.

Hepatosplenic candidiasis in patients with hematological malignancies: a 13-year retrospective cohort study

Background

Hepatosplenic candidiasis (HSC) used to be reported in patients with acute myeloid leukemia (AML) without antifungal prophylaxis. The aim was to describe the clinical features and outcomes of HSC over the last 13 years in a single French hematology center.

Methods

All patients diagnosed with HSC between 2008 and 2020 were included in a single-center retrospective cohort study. Data were collected from patient charts, and HSC was classified according to the 2020 European Organisation for Research and Treatment of Cancer/Mycoses Study Group definitions.

Results

Sixty patients were included, with 18.3% proven, 3.3% probable, and 78.3% possible HSC according to the 2020 European Organization for Research and Treatment of Cancer Mycoses Study Group classification. Among them, 19 patients were treated for acute myeloid leukemia (AML), 21 for lymphomas, and 14 for acute lymphoblastic leukemia. HSC occurred in 13 patients after autologous stem cell transplantation for lymphoma. At HSC diagnosis, 13 patients were receiving antifungal prophylaxis. Candida colonization was present in 84.2%, with prior candidemia in 36.7% of cases. β-D-glucans was positive in 55.8%, and 45.8% of tissue biopsies were contributive. First-line antifungal therapy was azoles in 61.7%, and steroids were associated in 45% of cases. At 3 months of follow-up, partial response to antifungal therapy was 94.2%. At last follow-up (mean, 22.6 months), 41 patients (68.3%) presented a complete hematological remission and 22 patients were deceased, none because of HSC.

Conclusions

The epidemiology of HSC has changed in the last decade, with fewer cases occurring in the AML setting. A better identification of patients at risk could lead to specific prophylaxis and improved diagnosis.

EORTC/MSGERC Definitions of Invasive Fungal Diseases: Summary of Activities of the Intensive Care Unit Working Group

The EORTC/MSGERC recently revised and updated the consensus definitions of invasive fungal disease (IFD). These definitions primarily focus on patients with cancer and stem cell or solid-organ transplant patients. They may therefore not be suitable for intensive care unit (ICU) patients. More in detail, while the definition of proven IFD applies to a broad range of hosts, the categories of probable and possible IFD were primarily designed for classical immunocompromised hosts and may therefore not be ideal for other populations. Moreover, the scope of the possible category of IFD has been diminished in the recently revised definitions for classically immunocompromised hosts. Diagnosis of IFD in the ICU presents many challenges, which are different for invasive candidiasis and for invasive aspergillosis. The aim of this article is to review progresses made in recent years and difficulties remaining in the development of definitions applicable in the ICU setting.

Clinical value of (1,3)-β-D-glucan, mannan, antimannan IgG and IgM antibodies in diagnosis of invasive candidiasis

Diagnosis of invasive candidiasis (IC) is still challenging due to absence of specific clinical signs and symptoms. In this study we investigate the clinical value of (1,3)-β-D-glucan (BDG), mannan (MN), antimannan immunoglobulin G (AM-IgG), and antimannan immunoglobulin M (AM-IgM) assay in diagnosis of IC. During 2016 to 2018 serum samples from 71 patients with IC and 185 patients without IC were collected. Serum samples from 41 patients with bacteremia were also enrolled as additional control. Significant differences in mean serum biomarkers levels between IC and control group were observed. At low cutoff threshold the sensitivity and specificity of BDG (70 pg/ml), MN (50 pg/ml), AM-IgG (80 AU/ml), and AM-IgM (80 AU/ml) assay were 64.8% and 90.8%, 64.8 and 89.2%,74.6% and 87.0%, 57.7% and 60.0%, respectively. Combined use of BDG/MN, BDG/AM-IgG and MN/AM-IgG improved the sensitivity and specificity to 85.9% and 81.1%, 85.9% and 80.0%, 81.7% and 81.6%, respectively. The combination of BDG/MN, BDG/AM-IgG, or MN/AM-IgG may provide an encouraging approach for diagnosis of IC.

Understanding Pathogenesis and Care Challenges of Immune Reconstitution Inflammatory Syndrome in Fungal Infections

Immune deficiency of diverse etiology, including human immunodeficiency virus (HIV), antineoplastic agents, immunosuppressive agents used in solid organ recipients, immunomodulatory therapy, and other biologics, all promote invasive fungal infections. Subsequent voluntary or unintended immune recovery may induce an exaggerated inflammatory response defining immune reconstitution inflammatory syndrome (IRIS), which causes significant mortality and morbidity. Fungal-associated IRIS raises several diagnostic and management issues. Mostly studied with Cryptococcus, it has also been described with other major fungi implicated in human invasive fungal infections, such as Pneumocystis, Aspergillus, Candida, and Histoplasma. Furthermore, the understanding of IRIS pathogenesis remains in its infancy. This review summarizes current knowledge regarding the clinical characteristics of IRIS depending on fungal species and existing strategies to predict, prevent, and treat IRIS in this patient population, and tries to propose a common immunological background to fungal IRIS.

Pre-clinical Imaging of Invasive Candidiasis Using ImmunoPET/MR

The human commensal yeast Candida is the fourth most common cause of hospital-acquired bloodstream infections, with Candida albicans accounting for the majority of the >400,000 life-threatening infections annually. Diagnosis of invasive candidiasis (IC), a disease encompassing candidemia (blood-borne yeast infection) and deep-seated organ infections, is a major challenge since clinical manifestations of the disease are indistinguishable from viral, bacterial and other fungal diseases, and diagnostic tests for biomarkers in the bloodstream such as PCR, ELISA, and pan-fungal β-D-glucan lack either standardization, sensitivity, or specificity. Blood culture remains the gold standard for diagnosis, but test sensitivity is poor and turn-around time slow. Furthermore, cultures can only be obtained when the yeast resides in the bloodstream, with samples recovered from hematogenous infections often yielding negative results. Consequently, there is a pressing need for a diagnostic test that allows the identification of metastatic foci in deep-seated Candida infections, without the need for invasive biopsy. Here, we report the development of a highly specific mouse IgG3 monoclonal antibody (MC3) that binds to a putative β-1,2-mannan epitope present in high molecular weight mannoproteins and phospholipomannans on the surface of yeast and hyphal morphotypes of C. albicans, and its use as a [⁶⁴Cu]NODAGA-labeled tracer for whole-body pre-clinical imaging of deep-seated C. albicans infections using antibody-guided positron emission tomography and magnetic resonance imaging (immunoPET/MRI). When used in a mouse intravenous (i.v.) challenge model that faithfully mimics disseminated C. albicans infections in humans, the [⁶⁴Cu]NODAGA-MC3 tracer accurately detects infections of the kidney, the principal site of blood-borne candidiasis in this model. Using a strain of the emerging human pathogen Candida auris that reacts with MC3 in vitro, but which is non-infective in i.v. challenged mice, we demonstrate the accuracy of the tracer in diagnosing invasive infections in vivo. This pre-clinical study demonstrates the principle of using antibody-guided molecular imaging for detection of deep organ infections in IC, without the need for invasive tissue biopsy.

A Retrospective Assessment of Four Antigen Assays for the Detection of Invasive Candidiasis Among High-Risk Hospitalized Patients

Because of their high mortality rates and non-specific symptoms, invasive Candida infections pose a huge diagnostic and therapeutic challenge. In this study, we evaluated the three mannan antigen assays Platelia, Platelia Plus and Serion, and the (1-3)-β-D-glucan assay Fungitell in a group of high-risk (hematological and surgical) patients. Test results of 305 patients hospitalized at the Vienna General Hospital and the University Hospital of Innsbruck were retrospectively analyzed. We assessed the test accuracy by means of descriptive statistics. Nine (2.95%) patients were affected by invasive candidiasis (IC), and 25 (8.2%) patients had a probable/possible infection. The majority of patients (271; 88.9%) showed no signs of infection. The Platelia and Serion mannan assays had a low sensitivity (65% and 52%, respectively), but high specificity (98% for both tests). The newer version of the Platelia assay, the Platelia Plus, had a higher sensitivity (85%) but a lower specificity (89%). The sensitivity of the Fungitell assay was high (100%), while its specificity was low (58%). The positive predictive values were 0.48 for the Platelia and 0.41 for the Serion assay, 0.26 for the Platelia Plus and 0.09 for the Fungitell assay. Our limited, retrospective study suggests the efficacy of mannan assays as screening (Platelia Plus) and confirmatory (Serion) tests, while the Fungitell assay can be used to exclude invasive Candida infections.

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.

Diagnostic performance of 1,3-beta-D-glucan serum screening in patients receiving hematopoietic stem cell transplantation

BACKGROUND

The polysaccharide cell wall component, 1,3-beta-D-glucan (BDG), is used as a serum biomarker for invasive fungal infection (IFI). Patients receiving hematopoietic stem cell transplantation (HSCT) are considered a highly vulnerable group for IFI development. We evaluated the diagnostic performance of serum BDG screening in HSCT recipients.

METHODS

HSCT recipients were prospectively enrolled in this study between September 2014 and August 2015. Routine serum BDG screening was performed 2-3 times weekly by using the Fungitell(®) assay. All samples were classified according to the 2008 EORTC/MSG criteria, with serum BDG results not being considered for classification. The diagnostic performance of BDG testing for IFI was calculated. BDG values ≥80 pg/mL were considered positive.

RESULTS

A total of 308 serum samples were collected in 45 patients. The majority of 172 samples (55.8%) were obtained at the early phase (within 30 days) after allogeneic HSCT. BDG levels were significantly higher in 16 possible/probable IFI samples when compared to no evidence for IFI samples (median 170 pg/mL, interquartile range [IQR] 100-274 pg/mL vs. median 15 pg/mL, IQR 15-15 pg/mL; P < 0.001, Mann-Whitney U-test). Diagnostic performance of serum BDG screening for possible IFI/probable invasive pulmonary aspergillosis vs. no evidence for IFI was as follows: sensitivity 81%, specificity 98%, positive predictive value 65%, negative predictive value (NPV) 99%, and diagnostic odds ratio 176 (95% confidence interval 41-761).

CONCLUSIONS

Our data suggest that serum BDG testing in HSCT patients may be highly specific and associated with a very high NPV of >99%. Therefore, serum BDG may be a helpful tool to rule out IFI in HSCT patients.

Case report: false positive elevated serum-galactomannan levels after autologous hematopoietic stem cell transplantation caused by oral nutritional supplements

Positive galactomannan tests in patients who underwent chemotherapy without any clinical signs of a fungal infection should lead the clinician to consideration of a false‐positive test result. Oral nutritional supplements may be a cause, especially in the case of concomitant disturbance of the gastrointestinal mucosal barrier because of mucositis.

Diagnosis of Invasive Fungal Diseases in Hematological Malignancies: A Critical Review of Evidence and Turkish Expert Opinion (TEO-2)

One of the most problematic issues in hematological malignancies is the diagnosis of invasive fungal diseases. Especially, the difficulty of mycological diagnosis and the necessity of immediate intervention in molds have led to the adoption of “surrogate markers” that do not verify but rather strongly suggest fungal infection. The markers commonly used are galactomannan (GM), beta-glucan, and imaging methods. Although there are numerous studies on these diagnostic approaches, none of these markers serve as a support for the clinician, as is the case in human immunodeficiency virus (HIV) or cytomegalovirus (CMV) infections. This paper has been prepared to explain the diagnostic tests. As molecular tests have not been standardized and are not used routinely in the clinics, they will not be mentioned here.

Molecular and nonmolecular diagnostic methods for invasive fungal infections

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

Candida colonization index and subsequent infection in critically ill surgical patients: 20 years later

Introduction

For decades, clinicians dealing with immunocompromised and critically ill patients have perceived a link between Candida colonization and subsequent infection. However, the pathophysiological progression from colonization to infection was clearly established only through the formal description of the colonization index (CI) in critically ill patients. Unfortunately, the literature reflects intense confusion about the pathophysiology of invasive candidiasis and specific associated risk factors.

Methods

We review the contribution of the CI in the field of Candida infection and its development in the 20 years following its original description in 1994. The development of the CI enabled an improved understanding of the pathogenesis of invasive candidiasis and the use of targeted empirical antifungal therapy in subgroups of patients at increased risk for infection.

Results

The recognition of specific characteristics among underlying conditions, such as neutropenia, solid organ transplantation, and surgical and nonsurgical critical illness, has enabled the description of distinct epidemiological patterns in the development of invasive candidiasis.

Conclusions

Despite its limited bedside practicality and before confirmation of potentially more accurate predictors, such as specific biomarkers, the CI remains an important way to characterize the dynamics of colonization, which increases early in patients who develop invasive candidiasis.

Procalcitonin as a marker of Candida species detection by blood culture and polymerase chain reaction in septic patients

Background

The aim of our study is to test procalcitonin (PCT) as surrogate marker of identification of Candida spp. by blood culture (BC) and real-time-polymerase chain reaction (PCR), whether alone or in association with bacteria, in septic patients.

Methods

We performed a single-centre retrospective study. We reviewed the clinical charts of patients with a diagnosis of severe sepsis or septic shock treated at our general intensive care unit from March 2009 to March 2013. We analysed all diagnostic episodes consisting of BC, real-time PCR assay and dosage of PCT. We registered age, sex, white blood count, sequential organ failure assessment score and type of admission between medical or surgical. When inclusion criteria were met more than once, we registered the new diagnostic episode as subsequent diagnostic episode. The diagnostic performance of PCT to predict Candida spp. identification alone or in mixed infections by either BC or PCR was tested using the receiver-operative characteristic curve. Logistic regression was constructed using presence of Candida spp. as the dependent variable.

Results

A total of 260 diagnostic episodes met the inclusion criteria. According to BC results classification, a significantly lower value of PCT was observed in Candida spp. BSI (0.99 ng/ml, 0.86 - 1.34) than in BSI caused by bacteria (16.7 ng/ml, 7.65 - 50.2) or in mixed infections (4.76 ng/ml, 2.98 - 6.08). Similar findings were observed considering PCR results. A cut-off of ≤ 6.08 ng/ml for PCT yielded a sensitivity of 86.8%, a specificity of 87.4%, a positive predictive value of 63.9%, a negative predictive value (NPV) of 96.3% and an area under the curve of 0.93 for Candida spp. identification by BC. A similar high NPV for a cut-off ≤ 6.78 ng/ml was observed considering the classification of diagnostic episodes according to PCR results, with an AUC of 0.85. A subsequent diagnostic episode was independently associated with Candida spp. detection either by BC or PCR.

Conclusion

PCT could represent a useful diagnostic tool to exclude the detection of Candida spp. by BC and PCR in septic patients.

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.

An Italian consensus for invasive candidiasis management (ITALIC)

INTRODUCTION

Invasive candidiasis (IC) has primarily been studied in intensive care unit (ICU) patients, although, in reality, a vast majority of these infections occur outside of the ICU. The recent publication of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) guidelines also deal with the non-ICU population, but many uncertainties remain on the management of IC, particularly in non-critically ill patients.

METHODS

The Italian Society of Antimicrobial Therapy, Società Italiana di Terapia Antimicrobica (SITA), produced practical, hospital-wide recommendations on the management of Candida infection in non-immunocompromised patients in the hospital ward.

RESULTS AND DISCUSSION

Our focus is on patient stratification in terms of risk factors for IC and of clinical severity, emphasising a high index of suspicion to ensure early diagnosis, early treatment and de-escalation when a patient is clinically stable, in order to optimise resource allocation.

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.

Management of candidaemia and invasive candidiasis in critically ill patients

Critically ill patients in the intensive care unit (ICU) are at increased risk of encountering bloodstream infections (BSIs) with Candida spp., associated with an elevated crude mortality rate. This supports the significance of early detection of infection and identification of the most effective management approach. A review of the various antifungal treatments and an evaluation of the diverse management approaches for invasive candidiasis in critically ill patients is necessary for guiding evidence-based decision-making. Different early detection schemes for invasive candidiasis are well documented in the literature. Other than the common use of blood cultures, new methods entail the use of risk prediction scores and biomarker tests. Regarding management strategies, different options are currently supported. These include prophylaxis, empirical therapy, pre-emptive therapy, and treatment of culture-documented infections. The choice of treatment is greatly dependent on several factors related to the patient and/or to the surrounding environment. Attention needs to be given to previous exposure to azoles, epidemiological data on dominant Candida spp. in local ICUs, severity of illness and associated morbidities. This paper summarises the most recent literature as well as the guidelines issued by the Infectious Diseases Society of America. The objective is to identify the best diagnosis and management approaches for serious Candida infections in critically ill patients. In addition, this article addresses an important aspect associated with managing candidaemia in critically ill patients pertaining to the decision for intravenous catheter removal.

Early diagnosis of sepsis using serum biomarkers

Sepsis, an innate immunological response of systemic inflammation to infection, is a growing problem worldwide with a relatively high mortality rate. Immediate treatment is required, necessitating quick, early and accurate diagnosis. Rapid molecular-based tests have been developed to address this need, but still suffer some disadvantages. The most commonly studied biomarkers of sepsis are reviewed for their current uses and diagnostic accuracies, including C-reactive protein, procalcitonin, serum amyloid A, mannan and IFN-γ-inducible protein 10, as well as other potentially useful biomarkers. A singular ideal biomarker has not yet been identified; an alternative approach is to shift research focus to determine the diagnostic relevancy of multiple biomarkers when used in concert. Challenges facing biomarker research, including lack of methodology standardization and assays with better detection limits, are discussed. The ongoing efforts in the development of a multiplex point-of-care testing kit, enabling quick and reliable detection of serum biomarkers, may have great potential for early diagnosis of sepsis.

Invasive mycoses: diagnostic challenges

Despite the availability of newer antifungal drugs, outcomes for patients with invasive fungal infections (IFIs) continue to be poor, in large part due to delayed diagnosis and initiation of appropriate antifungal therapy. Standard histopathologic diagnostic techniques are often untenable in at-risk patients, and culture-based diagnostics typically are too insensitive or nonspecific, or provide results after too long a delay for optimal IFI management. Newer surrogate markers of IFIs with improved sensitivity and specificity are needed to enable earlier diagnosis and, ideally, to provide prognostic information and/or permit therapeutic monitoring. Surrogate assays should also be accessible and easy to implement in the hospital. Several nonculture-based assays of newer surrogates are making their way into the medical setting or are currently under investigation. These new or up-and-coming surrogates include antigens/antibodies (mannan and antimannan antibodies) or fungal metabolites (d-arabinitol) for detection of invasive candidiasis, the Aspergillus cell wall component galactomannan used to detect invasive aspergillosis, or the fungal cell wall component and panfungal marker β-glucan. In addition, progress continues with use of polymerase chain reaction- or other nucleic acid- or molecular-based assays for diagnosis of either specific or generic IFIs, although the various methods must be better standardized before any of these approaches can be more fully implemented into the medical setting. Investigators are also beginning to explore the possibility of combining newer surrogate markers with each other or with more standard diagnostic approaches to improve sensitivity, specificity, and capacity for earlier diagnosis, at a time when fungal burden is still relatively low and more responsive to antifungal therapy.

Candida colonization index in patients admitted to an ICU

Multiple-site colonization with Candida spp. is commonly recognized as a risk factor for invasive fungal infection in critically ill patients. We carried out a study to determine the relationship between Candida colonization and invasive infection in neurological patients admitted to an ICU. At admission (T0) and every three days for two weeks, different samples (pharynx swab, tracheal secretions, stomach contents, etc.) were collected for mycological surveillance. Candida mannan antigen and Candida anti-mannan antibodies were assayed. The Colonization Index (CI) and Corrected Colonization Index were calculated for each time point. Of all patients 70% was already colonized by Candida spp. at T0 and six of them had CI ≥ 0.5. Three patients developed candidemia; they had CI ≥ 0.5 before infection. Positive values of Candida mannan antigen and anti-mannan antibodies were found only in the patients with candidemia. The sensitivity and specificity of the Candida mannan test were 66.6% and 100%, respectively, while the sensitivity and specificity of the anti-mannan antibody test were 100%. In accordance with other authors, we find the surveillance cultures are useful to monitor the Candida colonization in ICU patients. In addition, the sequential observation of anti-mannan antibodies could contribute to early diagnosis of candidiasis more than Candida mannan antigen in immunocompetent patients.

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.

New molecular and surrogate biomarker-based tests in the diagnosis of bacterial and fungal infection in febrile neutropenic patients

PURPOSE OF REVIEW

Prompt diagnosis of infection in febrile neutropenia hosts with hematological malignancy is essential in directing therapy. We highlight experience using modern molecular and biomarker-based methods to diagnose bacterial and fungal bloodstream infections and invasive aspergillosis in these patients.

RECENT FINDINGS

Nucleic acid amplification-based strategies are used to detect and identify pathogens from blood cultures or from blood/clinical specimens; the latter are more likely to influence clinical management. Advances in DNA extraction include standardization of isolation of Aspergillus DNA from blood. Broad-range and/or multiplex PCR generally have greater clinical utility than pathogen-specific assays. However, Aspergillus-PCR assays are useful in confirming/excluding disease and monitoring high-risk patients for invasive aspergillosis. Commercial real-time PCR/peptide nucleic acid fluorescent in-situ hybridization systems, used as adjuncts to blood cultures, to detect bacteria and fungi in blood cultures (or blood), are as sensitive as culture and enable earlier institution of targeted therapy. Yet there are no data indicating that molecular detection of bacterial/fungal pathogens influences patient outcomes. Positive serum Aspergillus galactomannan and 1,3-β-D-glucan tests are useful biomarkers in the diagnosis/screening of fungal infection, and have potential as measures of response to antifungal therapy. Serum procalcitonin levels can help differentiate infectious, from noninfectious, fever. Combined molecular and nonmolecular testing likely offers optimal diagnostic accuracy.

SUMMARY

Numerous PCR-based and biomarker tools are available for the diagnosis and screening of infection in febrile neutropenia hosts. The optimal approach remains to be resolved by prospective studies examining the impact of one or more of tests on patient outcomes.

Invasive Candida infections in solid organ transplant recipient children

Solid organ transplantation (SOT) is now an accepted therapy for many end-stage organ disorders and fungal infections are the principal cause of infection-related mortality in SOT recipients. Among invasive fungal infections, Candida species are the most common pathogens identified, associated with high mortality rates. The epidemiology and clinical manifestations of Candida infections vary with the type of organ transplantation. This article reviews invasive Candida infections in pediatric SOT recipients.

[The Spanish Society of Paediatric Infectious Diseases (SEIP) recommendations on the diagnosis and management of invasive candidiasis]

Candida yeasts are ubiquitous commensals, which can cause opportunistic infection in any location of the body. The source of infection may be both endogenous and exogenous. Invasive candidiasis encompasses different entities ranging from invasive candidiasis to disseminated multiorgan infection. Invasive candidiasis is the third leading cause of nosocomial bloodstream infection and the fourth of all nosocomial infections. It is also the most common invasive fungal infection in non-neutropenic critically ill patients, with a remarkable increase in the last 20 years owing to the increased survival of these patients and to more complex diagnostic, therapeutic and surgical procedures. Its incidence in infants, according to recent reviews, stands at 38.8 cases/100,000 children younger than 1 year. Candida albicans remains the most frequent isolate in invasive infections, although infections caused by other species have risen in the last years, such as C. kruzsei, C. glabrata and C. parapsilosis; the latter causing invasive candidiasis mainly associated with central venous catheter management, especially in neonatal units. The overall mortality of invasive candidiasis is high, with 30-day mortality reaching 20-44% in some series involving paediatric patients. This report provides an update on incidence, epidemiology, clinical presentation, diagnosis, treatment and outcome of invasive infection by Candida spp. in the paediatric patient.

Invasive candidiasis in non-hematological patients

Candida is one of the most frequent pathogens isolated in bloodstream infections, and is associated with significant morbidity and mortality. In addition to haematological patients, there are several other populations with a substantial risk of developing invasive candidiasis (IC). These include patients undergoing prolonged hospitalisation with the use of broad-spectrum antibiotics, those fitted with intravascular catheters, admitted to both adult and neonate intensive care units (ICU) or gastrointestinal surgery wards and subjects with solid tumours undergoing cytotoxic chemotherapy. As a general rule, every immunocompromised patient might be at risk of Candida infection, including, for example, diabetic patients.

The epidemiology of species responsible for IC has been changing, both at local and worldwide level, shifting from C. albicans to non-albicans species, that can be intrinsically resistant to fluconazole (C. krusei and, to some extent, C. glabrata), difficult to eradicate because of biofilm production (C. parapsilosis) or than might acquire resistance to azole during therapy.

Delaying the specific therapy has been shown to increase morbidity and mortality, but traditional microbiological diagnosis is poorly sensitive and slow. Thus, culture-based treatment may result in therapy started too late. In order to reduce the mortality in IC, several management strategies have been developed: prophylaxis, empirical and pre-emptive therapy. Compared to prophylaxis, the latter approaches allow to reduce the use of antifungals by targeting only patients at very high risk of IC. Non-invasive serological markers and scores based on clinical prediction rules such as the presence of risk factors or Candida colonisation, have been developed with the aim of allowing prompt initiation of treatment. Although the use of these diagnostic tools in pre-emptive strategies is promising, the performance and cost-effectiveness should be tested in large trials.

Agents recommended for initial treatment of candidemia in severely ill patients include echinocandins and lipid formulations of amphotericin B, while stable patients without risk factors for azole-resistance might be treated with fluconazole.

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.

New nonculture-based methods for the diagnosis of invasive candidiasis

PURPOSE OF REVIEW

Invasive candidiasis is a severe infectious complication occurring mostly in onco-hematologic and surgical patients. Its conventional diagnosis is insensitive and often late, leading to a delayed treatment and a high mortality. The purpose of this article is to review recent contributions in the nonconventional diagnostic approaches of invasive candidiasis, both for the detection of the epidose and the characterization of the etiologic agent.

RECENT FINDINGS

Antigen-based tests to detect invasive candidiasis comprise a specific test, mannan, as well as a nonspecific test, beta-D-glucan. Both have a moderate sensitivity and a high specificity, and cannot be recommended alone as a negative screening tool or a positive syndrome driven diagnostic tool. Molecular-based tests still have not reached the stage of rapid, easy to use, standardized tests ideally complementing blood culture at the time of blood sampling. New tests (fluorescence in-situ hybridization or mass spectrometry) significantly reduce the delay of identification of Candida at the species level in positive blood cultures, and should have a positive impact on earlier appropriate antifungal therapy and possibly on outcome.

SUMMARY

Both antigen-based and molecular tests appear as promising new tools to complement and accelerate the conventional diagnosis of invasive candidiasis with an expected significant impact on earlier and more focused treatment and on prognosis.

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.

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

BACKGROUND

Surveillance cultures may be helpful in identifying patients at increased risk of developing invasive candidiasis. However, only scant information exists on the effect of Candida colonization on serum levels of diagnostic biomarkers. This prospective surveillance study determined the extent of Candida colonization among pediatric cancer patients and its possible impact on serum levels of (1-3)-β-D-glucan (BDG), Candida mannan and Candida DNA.

METHODS

A total of 1075 swabs originating from oropharynx (n = 294), nostrils (n = 600), rectum (n = 28), groin (n = 50), ear (n = 54), and axilla (n = 49) of 63 pediatric cancer patients were cultured for the isolation of Candida spp. Patients yielding Candida spp. from any sites were considered as colonized. Serum samples were collected from patients at the time of first surveillance culture for detection of BDG by Fungitell kit and Candida mannan by Platelia Candida Ag. Candida DNA was detected by using panfungal primers and identification was carried out by using species-specific primers and DNA sequencing.

RESULTS

Seventy-five (7.6%) swab cultures from 35 (55.5%) patients yielded Candida spp. These isolates included C. albicans (n = 62), C. dubliniensis (n = 8), C. glabrata and C. tropicalis (n = 2 each) and C. krusei (n = 1). Eleven patients were colonized at three or more sites. Eight of 36 serum samples from 6 colonized patients yielded BDG values higher than the currently recommended cut-off value of ≥80 pg/ml. However, none of the serum samples yielded Candida mannan levels ≥0.5 ng/ml and PCR test for Candida DNA was also negative in all the serum samples of colonized patients. During the study period, only two colonized patients subsequently developed candidemia due to C. tropicalis. Besides positive blood cultures, C. tropicalis DNA, BDG and Candida mannan were also detected in serum samples of both the patients.

CONCLUSIONS

The present study demonstrates that while mucosal colonization with Candida species in pediatric cancer patients is common, it does not give rise to diagnostically significant levels of Candida mannan or Candida DNA in serum specimens. However, BDG values may be higher than the cut-off value in some pediatric patients without clinical evidence of invasive Candida infection. The study suggests the utility of Candida mannan or Candida DNA in the diagnosis of invasive candidiasis, however, the BDG levels in pediatric cancer subjects should be interpreted with caution.

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.