Potential role of Candida albicans germ tube antibody in the diagnosis of deep-seated candidemia

Invasive candidiasis

Invasive candidiasis is an important fungal disease caused by Candida albicans and, increasingly, non-albicans Candida pathogens. Invasive Candida infections originate most frequently from endogenous human reservoirs and are triggered by impaired host defences. Signs and symptoms of invasive candidiasis are non-specific; candidaemia is the most diagnosed manifestation, with disseminated candidiasis affecting single or multiple organs. Diagnosis poses many challenges, and conventional culture techniques are frequently supplemented by non-culture-based assays. The attributable mortality from candidaemia and disseminated infections is ~30%. Fluconazole resistance is a concern for Nakaseomyces glabratus, Candida parapsilosis, and Candida auris and less so in Candida tropicalis infection; acquired echinocandin resistance remains uncommon. The epidemiology of invasive candidiasis varies in different geographical areas and within various patient populations. Risk factors include intensive care unit stay, central venous catheter use, broad-spectrum antibiotics use, abdominal surgery and immune suppression. Early antifungal treatment and central venous catheter removal form the cornerstones to decrease mortality. The landscape of novel therapeutics is growing; however, the application of new drugs requires careful selection of eligible patients as the spectrum of activity is limited to a few fungal species. Unanswered questions and knowledge gaps define future research priorities and a personalized approach to diagnosis and treatment of invasive candidiasis is of paramount importance.

Comparison of β-1-3-D-Glucan and Candida Mannan Biomarker Assays with Serological Tests for the Diagnosis of Candidemia

Invasive candidiasis, including bloodstream infection (candidemia), encompasses the most severe forms of Candida infection. Several species-specific and non-specific serological assays are commercially available to aid in diagnosis. This study compared the performance of five such biomarker assays. Serum samples from 14 patients with proven or probable invasive candidiasis, and from 10 control patients, were included in the analysis. A total of 50 serum samples were tested using C. albicans germ tube antibody (CAGTA) assay (Vircell), C. albicans IgM, C. albicans IgG and Candida mannan assays (Dynamiker Biotechnology). Among these samples, the β-1-3-D-glucan (BDG) assay (Fungitell), a laboratory standard for the diagnosis of invasive candidiasis, was positive in 20 (40%), intermediate in five (10%) and negative in 25 (50%). In cases of proven or probable candidemia, the sensitivity and specificity of the BDG assay was 86% and 80%, respectively; the Candida mannan assay, 14% and 86%; the CAGTA test, 57% and 60%; the C. albicans IgM assay, 71% and 60%; and C. albicans IgG assay 29% and 90%. In 4/8 (50%) cases with multiple serum samples, C. albicans IgM was positive sooner than BDG. Thus, when used as a rule-out test for invasive candidiasis, our data suggest that the C. albicans IgM assay may assist antifungal stewardship (over serum BDG).

Invasive candidiasis: current clinical challenges and unmet needs in adult populations

Invasive candidiasis (IC) is a serious infection caused by several Candida species, and the most common fungal disease in hospitals in high-income countries. Despite overall improvements in health systems and ICU care in the last few decades, as well as the development of different antifungals and microbiological techniques, mortality rates in IC have not substantially improved. The aim of this review is to summarize the main issues underlying the management of adults affected by IC, focusing on specific forms of the infection: IC developed by ICU patients, IC observed in haematological patients, breakthrough candidaemia, sanctuary site candidiasis, intra-abdominal infections and other challenging infections. Several key challenges need to be tackled to improve the clinical management and outcomes of IC patients. These include the lack of global epidemiological data for IC, the limitations of the diagnostic tests and risk scoring tools currently available, the absence of standardized effectiveness outcomes and long-term data for IC, the timing for the initiation of antifungal therapy and the limited recommendations on the optimal step-down therapy from echinocandins to azoles or the total duration of therapy. The availability of new compounds may overcome some of the challenges identified and increase the existing options for management of chronic Candida infections and ambulant patient treatments. However, early identification of patients that require antifungal therapy and treatment of sanctuary site infections remain a challenge and will require further innovations.

Existing and emerging therapies for the treatment of invasive candidiasis and candidemia

INTRODUCTION

Invasive candidiasis or candidemia is a severe infection affecting more than 250,000 people worldwide every year. It is present in up to 16% of ICU patients. The prognosis of these infections is unfavorable, with global death estimated around 50,000 per year, which corresponds to up to 40% depending on patient severity and comorbidities. Therapeutic failure is not rare due to the emergence of multiresistant strains and of new species poorly responsive to current therapies like Candida auris.

AREAS COVERED

We first review the positioning of antifungal drugs used to treat candidiasis, namely polyenes, azoles, echinocandins and pyrimidine analogues. We then discuss the progresses brought by new formulations, new derivatives within these classes, compounds acting on new targets or repurposed drugs in terms of pharmacokinetic profile, spectrum of activity, potency, safety or risk of drug-drug interactions.

EXPERT OPINION

While new formulations (amphotericin B cochleate) improve oral bioavailability of the corresponding drugs, new azoles or echinocandins offer higher potency including against strains resistant to former generations of drugs. Repurposed drugs show synergism with current therapies in vitro. Results from ongoing and future clinical trials will be decisive to establish the interest for these drugs in our arsenal.

Similarities and Differences among Species Closely Related to Candida albicans: C. tropicalis, C. dubliniensis, and C. auris

Although Candida species are widespread commensals of the microflora of healthy individuals, they are also among the most important human fungal pathogens that under certain conditions can cause diseases (candidiases) of varying severity ranging from mild superficial infections of the mucous membranes to life-threatening systemic infections. So far, the vast majority of research aimed at understanding the molecular basis of pathogenesis has been focused on the most common species—Candida albicans. Meanwhile, other closely related species belonging to the CTG clade, namely, Candida tropicalis and Candida dubliniensis, are becoming more important in clinical practice, as well as a relatively newly identified species, Candida auris. Despite the close relationship of these microorganisms, it seems that in the course of evolution, they have developed distinct biochemical, metabolic, and physiological adaptations, which they use to fit to commensal niches and achieve full virulence. Therefore, in this review, we describe the current knowledge on C. tropicalis, C. dubliniensis, and C. auris virulence factors, the formation of a mixed species biofilm and mutual communication, the environmental stress response and related changes in fungal cell metabolism, and the effect of pathogens on host defense response and susceptibility to antifungal agents used, highlighting differences with respect to C. albicans. Special attention is paid to common diagnostic problems resulting from similarities between these species and the emergence of drug resistance mechanisms. Understanding the different strategies to achieve virulence, used by important opportunistic pathogens of the genus Candida, is essential for proper diagnosis and treatment.

Vaccines against candidiasis: Status, challenges and emerging opportunity

Candidiasis is a mycosis caused by opportunistic Candida species. The occurrence of fungal infections has considerably increased in the last few years primarily due to an increase in the number of immune-suppressed individuals. Alarming bloodstream infections due to Candida sp. are associated with a higher rate of morbidity and mortality, and are emerged as major healthcare concerns worldwide. Currently, chemotherapy is the sole available option for combating fungal diseases. Moreover, the emergence of resistance to these limited available anti-fungal drugs has further accentuated the concern and highlighted the need for early detection of fungal infections, identification of novel antifungal drug targets, and development of effective therapeutics and prophylactics. Thus, there is an increasing interest in developing safe and potent immune-based therapeutics to tackle fungal diseases. In this context, vaccine design and its development have a priority. Nonetheless, despite significant advances in immune and vaccine biology over time, a viable commercialized vaccine remains awaited against fungal infections. In this minireview, we enumerate various concerted efforts made till date towards the development of anti-Candida vaccines, an option with pan-fugal vaccine, vaccines in the clinical trial, challenges, and future opportunities.

The role of diagnostics-driven antifungal stewardship in the management of invasive fungal infections: a systematic literature review

Antifungal stewardship (AFS) programs are key to optimizing antifungal use and improving outcomes in patients with invasive fungal infections. Our systematic literature review evaluated the impact of diagnostics in AFS programs by assessing performance and clinical measures. Most eligible studies were from Europe and the United States (n = 12/17). Diagnostic approaches included serum β-1–3-D-glucan test (n/N studies, 7/17), galactomannan test (4/17), computed tomography scan (3/17), magnetic resonance (2/17), matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS; 2/17), polymerase chain reaction (1/17), peptide nucleic acid fluorescent in situ hybridization (PNA-FISH) assay (1/17), and other routine methods (9/17). Time to species identification decreased significantly using MALDI-TOF and PNA-FISH (n = 2). Time to targeted therapy and length of empiric therapy also decreased (n = 3). Antifungal consumption decreased by 11.6%–59.0% (7/13). Cost-savings ranged from 13.5% to 50.6% (5/10). Mortality rate (13/16) and length of stay (6/7) also decreased. No negative impact was reported on patient outcomes. Diagnostics-driven interventions can potentially improve AFS measures (antifungal consumption, cost, mortality, and length of stay); therefore, AFS implementation should be encouraged.

Faster infection diagnostics for intensive care unit (ICU) patients

INTRODUCTION

: The patient admitted to intensive care units (ICU) is critically ill, to some extent immunosuppressed, with a high risk of infection, sometimes by multidrug-resistant microorganisms. In this context, the intensivist expects from the microbiology service quick and understandable information so that appropriate antimicrobial treatment for that particular patient and infection can be initiated.

AREAS COVERED

: In this review of recent literature (2015-2021), we identified diagnostic methods for the most prevalent infections in these patients through a search of the databases Pubmed, evidence-based medicine online, York University reviewers group, Cochrane, MBE-Trip, and Sumsearch using the terms: adult, clinical laboratory techniques, critical care, early diagnosis, microbiology, molecular diagnostic techniques, spectrometry and metagenomics.

EXPERT OPINION

: There has been an exponential surge in diagnostic systems used directly on blood and other samples to expedite microbial identification and antimicrobial susceptibility testing of pathogens. Few studies have thus far assessed their clinical impact; final outcomes will also depend on preanalytical and post-analytical factors. Besides, many of the resistance mechanisms cannot yet be detected with molecular techniques, which impairs the prediction of the actual resistance phenotype.

Nonetheless, this is an exciting field with much yet to explore.

The Role of Candida albicans Virulence Factors in the Formation of Multispecies Biofilms With Bacterial Periodontal Pathogens

Periodontal disease depends on the presence of different microorganisms in the oral cavity that during the colonization of periodontal tissues form a multispecies biofilm community, thus allowing them to survive under adverse conditions or facilitate further colonization of host tissues. Not only numerous bacterial species participate in the development of biofilm complex structure but also fungi, especially Candida albicans, that often commensally inhabits the oral cavity. C. albicans employs an extensive armory of various virulence factors supporting its coexistence with bacteria resulting in successful host colonization and propagation of infection. In this article, we highlight various aspects of individual fungal virulence factors that may facilitate the collaboration with the associated bacterial representatives of the early colonizers of the oral cavity, the bridging species, and the late colonizers directly involved in the development of periodontitis, including the “red complex” species. In particular, we discuss the involvement of candidal cell surface proteins—typical fungal adhesins as well as originally cytosolic “moonlighting” proteins that perform a new function on the cell surface and are also present within the biofilm structures. Another group of virulence factors considered includes secreted aspartic proteases (Sap) and other secreted hydrolytic enzymes. The specific structure of the candidal cell wall, dynamically changing during morphological transitions of the fungus that favor the biofilm formation, is equally important and discussed. The non-protein biofilm-composing factors also show dynamic variability upon the contact with bacteria, and their biosynthesis processes could be involved in the stability of mixed biofilms. Biofilm-associated changes in the microbe communication system using different quorum sensing molecules of both fungal and bacterial cells are also emphasized in this review. All discussed virulence factors involved in the formation of mixed biofilm pose new challenges and influence the successful design of new diagnostic methods and the application of appropriate therapies in periodontal diseases.

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.

The Evolving Landscape of Fungal Diagnostics, Current and Emerging Microbiological Approaches

Invasive fungal infections are increasingly recognized in immunocompromised hosts. Current diagnostic techniques are limited by low sensitivity and prolonged turnaround times. We review emerging diagnostic technologies and platforms for diagnosing the clinically invasive disease caused by Candida, Aspergillus, and Mucorales.

Molecular Identification of Candida Species in the Oral Microbiota of Individuals with Down Syndrome: A Case-Control Study

Candida species are common in the human oral microbiota and may cause oral candidiasis (OC) when the microbiota equilibrium is disturbed. Immunosuppressed individuals are susceptible to oral infections as individuals with Down syndrome (IDS) due to particularities of their mouth morphoanatomy, saliva and comorbidities. This study aimed to analyze the molecular epidemiology of Candida spp. from the oral cavity of IDS and their relatives. A case-control study with 80 IDS and 80 non-syndromic (non-DS) was evaluated by oral swab collection for culture on Sabouraud dextrose agar, selection of yeast colonies to Gram staining and culturing on chromogenic media. DNA extraction was performed with the phenol/chloroform method for screening of 6 Candida species medically important in PCR, applying SPSS for statistics. We confirmed four species in 46 IDS without use of antimicrobials (57.54%), with a high prevalence of C. albicans/Ca (93.48%/43) and 3 C. glabrata/Cg (6.52%), being 25 of these IDS (31.25%) colonized by species other than C. albicans: Ca + Cg (16), Ca + C. tropicalis/Ct (7) and Ca + C. krusei/Ck (2). Only 10 non-DS were colonized by one species (11.25%): 6 C. albicans, 2 C. glabrata, 1 C. tropicalis and 1 C. krusei. Previous OC was reported by 39 IDS (48.75%), being 33 positives for Candida spp. (84.61%) and 17 with active OC (21.25%). Five non-DS reported OC previously and had no active lesions. Behavioral changes and buccal health programs directed to IDS may help prevent OC and its recurrence, providing information on oral hygiene for self-care.

Challenges and research priorities to progress the impact of antimicrobial stewardship

Antimicrobial stewardship programmes have been playing an important role in patient care and hospital policies. These programmes are now recognised as formal strategies for curbing the upward trend in antibiotic resistance and for improving the appropriate antimicrobial and antifungal use. The role of such programs in the era of antimicrobial resistance presents several unique challenges and opportunities, most notably in the diagnostic and therapeutic setting. Controversies remain regarding the most effective interventions and the appropriate design to evaluate their impact. In this review, based on rounds of discussion, we explain the most important challenges faced by antibiotic stewardship and antifungal stewardship programmes. We also try to suggest areas for further research.

Diagnostic surveillance by Candida albicans germ tube antibody in intensive care unit patients

BACKGROUND

The diagnosis of Invasive Candidiasis (IC) presents serious problems, mainly associated with the absence of pathognomonic symptoms of the disease and the difficulty of isolating the fungus in blood culture. Candida albicans germ tube antibody (CAGTA) provides a rapid and simple test for diagnosis of IC. The aim of this study was to evaluate the diagnostic role of the CAGTA in the monitoring of critically-ill patients at risk of developing IC.

METHODS

During diagnostic surveillance in the intensive care units (ICU) CAGTA was performed twice a week if predetermined risk factors were present and a positive result was considered when a serum titer ≥1/160 was detected in at least one sample.

RESULTS

Seventy critically ill patients were included in the study. Twenty-three patients with proven/probable IC were identified. The sensitivity, specificity, PPV, and NPV of CAGTA for the diagnosis of proven/probable IC in all 70 patients were 91.3%, 68.1%, 58.3%, and 94.1%, respectively. Statistically significant highest titers were found in patients with proven/probable IC as well as increasing titers more than 1/160.

CONCLUSIONS

Our results suggest that detection of CAGTA could be a useful biomarker for the diagnosis of proven and probable IC in critical patients during prolonged ICU stay. During the monitoring it is opportune to evaluate the titers kinetics since the clinical diagnosis of proven/probable IC coincided with increase titer from negative (<1/160) to more than 1/160.

Single human B cell-derived monoclonal anti-Candida antibodies enhance phagocytosis and protect against disseminated candidiasis

The high global burden of over one million annual lethal fungal infections reflects a lack of protective vaccines, late diagnosis and inadequate chemotherapy. Here, we have generated a unique set of fully human anti-Candida monoclonal antibodies (mAbs) with diagnostic and therapeutic potential by expressing recombinant antibodies from genes cloned from the B cells of patients suffering from candidiasis. Single class switched memory B cells isolated from donors serum-positive for anti-Candida IgG were differentiated in vitro and screened against recombinant Candida albicans Hyr1 cell wall protein and whole fungal cell wall preparations. Antibody genes from Candida-reactive B cell cultures were cloned and expressed in Expi293F human embryonic kidney cells to generate a panel of human recombinant anti-Candida mAbs that demonstrate morphology-specific, high avidity binding to the cell wall. The species-specific and pan-Candida mAbs generated through this technology display favourable properties for diagnostics, strong opsono-phagocytic activity of macrophages in vitro, and protection in a murine model of disseminated candidiasis.

Late diagnosis and ineffective treatment of fungal infections lead to high mortality. Here, Rudkin et al. generate anti-Candida human monoclonal antibodies with diagnostic and therapeutic potential, by expressing recombinant antibodies from genes cloned from B cells of patients suffering candidiasis.

Diagnostic accuracy of Candida albicans germ tube antibody for invasive candidiasis: systematic review and meta-analysis

BACKGROUND

Candida albicans germ tube antibody (CAGTA) may be helpful as a marker for the diagnosis of invasive candidiasis (IC). However, the performance has been variable. We conducted a meta-analysis to assess the diagnostic accuracy of this assay for diagnosing IC.

METHOD

We searched MEDLINE, EMBASE, Cochrane Collaboration databases, reference lists of retrieved studies, and review articles. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and a summary receiver-operating characteristic curve of CAGTA for diagnosing IC were pooled using meta-analysis.

RESULTS

A total of 976 patients (262 with proven or probable IC), included in 7 studies, were analyzed. The pooled sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratios and area under the curve were 66% (95% confidence interval [95% CI], 59% to 73%), 76% (95% CI, 58% to 88%), 2.8 (95% CI, 1.5 to 5.8), 0.44 (95% CI, 0.34 to 0.57), 6 (95% CI, 3 to 5), and 0.68 (95% CI, 0.64 to 0.72), respectively. Heterogeneity of specificity was significant.

CONCLUSION

The diagnostic accuracy of the CAGTA assay is moderate for IC. Since the CAGTA assay is not absolutely sensitive and specific for IC, the CAGTA results should be interpreted in parallel with other biomarkers and clinical findings.

Diagnosing Invasive Candidiasis

Cultures are negative in ∼50% of invasive candidiasis. Data are emerging for the performance of nonculture tests such as mannan/antimannan, Candida albicans germ tube antibody, 1,3-β-d-glucan, PCR, and the T2Candida panel in diagnosing both candidemia and deep-seated candidiasis. In most settings, positive predictive values of nonculture test are low, and negative predictive values are high. For tests to be useful, clinicians must understand the pretest likelihood of invasive candidiasis and test performance for the most common disease manifestation in a given patient. This paper reviews nonculture Candida diagnostics and discusses how they might be used effectively in patient care.

T2 Magnetic Resonance Assay: Overview of Available Data and Clinical Implications

Invasive candidiasis is a common healthcare-associated infection with a high mortality rate that can exceed 60% in cases of septic shock. Blood culture performance is far from ideal, due to the long time to positivity and suppression by antifungal agents. The T2 Magnetic Resonance (T2MR) assay is an FDA-approved qualitative molecular diagnostic method that can detect and speciate the 5 most common Candida spp.; namely, Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis, and Candida krusei, in approximately 5 h. In a multicenter clinical trial that included both a prospective and a contrived arm to represent the full range of clinically relevant concentrations of Candida spp., T2MR demonstrated a sensitivity and specificity of 91.1% and 98.1%, respectively. The utility of T2MR in candidemia depends on the prevalence of disease in each clinical setting. In intensive care units and other high-prevalence settings, the incorporation of T2MR in diagnostic algorithms is very appealing. T2MR is expected to allow timely initiation of antifungal therapy and help with anti-fungal stewardship. In low-prevalence settings, the positive predictive value of T2MR might not be enough to justify initiation of antifungal treatment in itself. The performance of T2MR has not been studied in cases of deep-seated candidiasis. Despite some promising evidence in published clinical trials, further studies are needed to determine the performance of T2MR in invasive candidiasis without candidemia. Overall, experience with T2MR in everyday clinical practice is evolving but, in the right setting, this technology is expected to provide “actionable information” for the management of patients evaluated for candidemia.

Non-Culture Diagnostics for Invasive Candidiasis: Promise and Unintended Consequences

Blood cultures are positive for Candida species in < 50% and < 20% of hematogenously disseminated and intra-abdominal candidiasis, respectively. Non-culture tests such as mannan, anti-mannan antibody, Candida albicans germ tube antibody (CAGTA), 1,3-β-d-glucan (BDG), the T2Candida nanodiagnostic panel, and polymerase chain reaction (PCR) are available for clinical use, but their roles in patient care are uncertain. Sensitivity/specificity of combined mannan/anti-mannan, BDG, T2Candida and PCR for candidemia are ~80%/80%, ~80%/80%, ~90%/98%, and ~90%/90%, respectively. Limited data for intra-abdominal candidiasis suggest CAGTA, BDG sensitivity/specificity of ~65%/75% and PCR sensitivity of ~85–90%. PCR specificity has varied widely for intra-abdominal candidiasis (33–97%), and T2Candida data are lacking. Tests will be useful if restricted to cases in which positive and negative predictive values (PPVs, NPVs) differ in a clinically meaningful way from the pre-test likelihood of invasive candidiasis. In some patients, PPVs are sufficient to justify antifungal treatment, even if blood cultures are negative. In most patients, NPVs of each test are excellent, which may support decisions to withhold antifungal therapy. If test results are not interpreted judiciously, non-culture diagnostics may have unintended consequences for stewardship and infection prevention programs. In particular, discrepant non-culture test-positive/culture-negative results may promote inappropriate antifungal treatment of patients who are unlikely to have candidiasis, and lead to spurious reporting of hospital-acquired infections. In conclusion, non-culture Candida diagnostics have potential to advance patient care, but this promise will be realized only if users understand tests’ strengths and limitations, and plan proactively for how best to employ them at their hospitals.

What has changed in the treatment of invasive candidiasis? A look at the past 10 years and ahead

The treatment of invasive candidiasis has changed greatly in the past decade and must continue to evolve if we are to improve outcomes in this serious infection. A review of recent history may provide insights for the future. The morbidity and mortality of invasive candidiasis remain difficult to measure despite an obvious clinical burden. Current treatment guidelines now recommend echinocandins as first-line empirical treatment, with fluconazole as an acceptable alternative for selected patients, reflecting the efficacy demonstrated by echinocandins and increasing resistance observed with fluconazole. The selection of antifungal therapy now must consider not only resistance but also the shift in predominance from Candida albicans to non-albicans species, notably Candida glabrata. The recent emergence of Candida auris has been met with great interest, although the longer-term implications of this phenomenon remain unclear. The broad goal of treatment continues to be administration of safe, efficacious antifungal therapy as soon as possible. Diagnostic methods beyond traditional blood culture present an opportunity to shorten the time to an accurate diagnosis, and earlier treatment initiation based on prophylactic and empirical or pre-emptive strategies seeks to ensure timely therapeutic intervention. In addition, there are novel agents in the antifungal pipeline. These developments, as well as ongoing studies of dosing, toxicity and resistance development, are important items on the current research agenda and may play a role in future changes to the treatment of invasive candidiasis.

Antibodies against a β-glucan-protein complex of Candida albicans and its potential as indicator of protective immunity in candidemic patients

Sera from candidemic and non-candidemic subjects were examined for antibodies against the cell wall β1,3- and β1,6-glucans, as well as the β-glucan-associated protein MP65 of Candida species. Although antibodies against each of the above components were detected in all subjects, candidemic patients had lower antibody titers against β1,3-glucan, but higher antibody titers against β1,6-glucan and MP65, than non-candidemic subjects. The elevated levels of anti-β1,6-glucan and -MP65 antibodies found in candidemic patients were independent on the patient risk category, APACHE II score, presence of co-morbidities, β1,3-glucanemia level, Candida isolate, and antifungal treatment. Interestingly, however, the anti-MP65, but not the anti-β1,6-glucan antibodies, of candidemic patients had higher titers in survivors than in non-survivors, particularly in those subject categories with the highest mortality (>65-years old, diabetic, or septic shock patients). Thus, candidemic patients are capable of boosting anti-Candida immune responses upon infection, and some of these responses might be associated to the generation of protective immunity in patients with candidemia.

Candida albicans Germ-Tube Antibody: Evaluation of a New Automatic Assay for Diagnosing Invasive Candidiasis in ICU Patients

Testing for Candida albicans germ-tube antibody IFA IgG assay (CAGTA) is used to detect invasive candidiasis infection. However, most suitable assays lack automation and rapid single-sample testing. The CAGTA assay was adapted in an automatic monotest system (invasive candidiasis [CAGTA] VirClia^® IgG monotest (VirClia^®), a chemiluminescence assay with ready-to-use reagents that provides a rapid objective result. CAGTA assay was compared with the monotest automatic VirClia^® assay in order to establish the diagnostic reliability, accuracy, and usefulness of this method. A prospective study with 361 samples from 179 non-neutropenic critically ill adults patients was conducted, including 21 patients with candidemia, 18 with intra-abdominal candidiasis, 84 with Candida spp. colonization, and 56 with culture-negative samples, as well as samples from ten healthy subjects. Overall agreement between the two assays (CAGTA and VirCLIA) was 85.3%. These assays were compared with the gold-standard method to determine the sensitivity, specificity as well as positive and negative predictive values. In patients with candidemia, values for CAGTA and VirCLIA assays were 76.2 versus 85.7%, 80.3 versus 75.8%, 55.2 versus 52.9%, and 91.4 versus 94.3%, respectively. The corresponding values in patients with intra-abdominal candidiasis were 61.1 versus 66.7%, 80.3 versus 75.8%, 45.8 versus 42.9%, and 88.3 versus 89.3%, respectively. No differences were found according to the species of Candida isolated in culture, except for Candida albicans and C. parapsilosis, for which VirClia^® was better than CAGTA. According to these results, the automated VirClia^® assay was a reliable, rapid, and very easy to perform technique as tool for the diagnosis invasive candidiasis.

[Update on invasive candidiasis in non-neutropenic critically ill adult patients]

Invasive candidiasis in non-neutropenic critically ill patients remains a challenge for clinicians due to its association with high morbidity and mortality rates, increased incidence, and health-care costs. It is well known that early diagnosis and treatment are associated with a better prognosis. For these reasons a thorough update has been performed in this setting focused on recent Spanish epidemiology, new predictive scores and microbiological tests such as mannan antigen, mannan antibodies, Candida albicans germ-tube antibodies or (1→3)-β-D-glucan detection, molecular techniques for the detection of fungal-specific DNA, advances in antifungal treatment and educational programs in Spain. An early diagnostic and therapeutic algorithm is proposed based on the combination of scores and microbiological test. The aim of this review is to provide physicians with the best information available in order to improve the prognosis of these patients.

Contribution of Candida biomarkers and DNA detection for the diagnosis of invasive candidiasis in ICU patients with severe abdominal conditions

BACKGROUND

To assess the performance of Candida albicans germ tube antibody (CAGTA), (1 → 3)-ß-D-glucan (BDG), mannan antigen (mannan-Ag), anti-mannan antibodies (mannan-Ab), and Candida DNA for diagnosing invasive candidiasis (IC) in ICU patients with severe abdominal conditions (SAC).

METHODS

A prospective study of 233 non-neutropenic patients with SAC on ICU admission and expected stay ≥ 7 days. CAGTA (cutoff positivity ≥ 1/160), BDG (≥80, 100 and 200 pg/mL), mannan-Ag (≥60 pg/mL), mannan-Ab (≥10 UA/mL) were measured twice a week, and Candida DNA only in patients treated with systemic antifungals. IC diagnosis required positivities of two biomarkers in a single sample or positivities of any biomarker in two consecutive samples. Patients were classified as neither colonized nor infected (n = 48), Candida spp. colonization (n = 154) (low-grade, n = 130; high-grade, n = 24), and IC (n = 31) (intra-abdominal candidiasis, n = 20; candidemia, n = 11).

RESULTS

The combination of CAGTA and BDG positivities in a single sample or at least one of the two biomarkers positive in two consecutive samples showed 90.3 % (95 % CI 74.2-98.0) sensitivity, 42.1 % (95 % CI 35.2-98.8) specificity, and 96.6 % (95 % CI 90.5-98.8) negative predictive value. BDG positivities in two consecutive samples had 76.7 % (95 % CI 57.7-90.1) sensitivity and 57.2 % (95 % CI 49.9-64.3) specificity. Mannan-Ag, mannan-Ab, and Candida DNA individually or combined showed a low discriminating capacity.

CONCLUSIONS

Positive Candida albicans germ tube antibody and (1 → 3)-ß-D-glucan in a single blood sample or (1 → 3)-ß-D-glucan positivity in two consecutive blood samples allowed discriminating invasive candidiasis from Candida spp. colonization in critically ill patients with severe abdominal conditions. These findings may be helpful to tailor empirical antifungal therapy in this patient population.

Antifungal stewardship in daily practice and health economic implications

During recent years, inappropriate antifungal use has contributed to the global increase in antifungal resistance and has played a role in the shift in the aetiology of invasive fungal infections. Moreover, overuse of antifungals may also lead to higher toxicity associated with unnecessary medication exposure and to increased healthcare costs. Antifungal stewardship (AFS) programmes consist of multidisciplinary interventions, led by specialists in infectious disease, microbiology and pharmacy that cooperate and communicate with the major prescribing departments in order to optimise antifungal therapies evaluating the indication, dose, streamlining and duration. Herein, we review the available evidence for the use of AFS and their impact on health economics. We also describe our AFS program, the successive steps we followed and the main difficulties we found.

Diagnostic of Fungal Infections Related to Biofilms

Fungal biofilm-related infections, most notably those caused by the Candida and Aspergillus genera, need to be diagnosed accurately and rapidly to avoid often unfavorable outcomes. Despite diagnosis of these infections is still based on the traditional histopathology and culture, the use of newer, rapid methods has enormously enhanced the diagnostic capability of a modern clinical mycology laboratory. Thus, while accurate species-level identification of fungal isolates can be achieved with turnaround times considerably shortened, nucleic acid-based or antigen-based detection methods can be considered useful adjuncts for the diagnosis of invasive forms of candidiasis and aspergillosis. Furthermore, simple, reproducible, and fast methods have been developed to quantify biofilm production by fungal isolates in vitro. In this end, isolates can be categorized as low, moderate, or high biofilm-forming, and this categorization may reflect their differential response to the conventional antifungal therapy. By means of drug susceptibility testing performed on fungal biofilm-growing isolates, it is now possible to evaluate not only the activity of conventional antifungal agents, but also of novel anti-biofilm agents. Despite this, future diagnostic methods need to target specific biofilm components/molecules, in order to provide a direct proof of the presence of this growth phenotype on the site of infection. In the meantime, our knowledge of the processes underlying the adaptive drug resistance within the biofilm has put into evidence biofilm-specific molecules that could be potentially helpful as therapeutic targets. Surely, the successful management of clinically relevant fungal biofilms will rely upon the advancement and/or refinement of these approaches.

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.

β-D-Glucan and Candida albicans germ tube antibody in ICU patients with invasive candidiasis

PURPOSE

To assess the performance of (1→3)-β-D-glucan (BDG) and Candida albicans germ tube antibody (CAGTA) for the diagnosis of invasive candidiasis (IC) in a prospective cohort of 107 unselected, non-neutropenic ICU patients.

METHODS

BDG (cutoff positivity ≥80 pg/mL) and CAGTA (cutoff positivity ≥1/160) assays were performed twice a week. Confounding factors included amoxicillin-clavulanate and piperacillin-tazobactam treatments, recent surgery, Gram-positive bloodstream infection, renal replacement therapy, and enteral nutrition. Patients were classified as neither colonized nor infected (n = 29), Candida spp. colonization (n = 63) (low grade, n = 32; high grade, n = 31), and invasive candidiasis (IC) (n = 15).

RESULTS

BDG levels were higher in patients with IC and high-grade colonization than in the remaining groups (p = 0.012), and two consecutive measurements ≥80 pg/mL discriminated IC from the remaining groups (sensitivity 80%, specificity 75.7%). For the discrimination between IC and Candida spp. colonization, the AUC for the maximum value of BDG was 0.667 (95% CI 0.544-0.790) and for the maximum value of CAGTA 0.545 (95% CI 0.395-0.694). Significant changes of BDG and CAGTA kinetics in IC patients treated with antifungals were not observed. In patients neither colonized nor infected or with low-grade Candida spp. colonization, none of the confounding factors was associated with a significant increase in BDG positivity.

CONCLUSIONS

Two consecutive BDG levels ≥80 pg/mL allowed discrimination among IC and high-grade colonization. Systemic antifungal therapy could not be monitored with biomarker kinetics, and BDG levels were not subject to interference by confounding factors in either colonized or infected patients or with low-grade colonization.

Non-cultural methods for the diagnosis of invasive fungal disease

Invasive fungal diseases carry a high mortality risk which can be reduced by early treatment. Diagnosing invasive fungal diseases is challenging, because invasive methods for obtaining histological samples are frequently not feasible in thrombocytopenic immunocompromised patients, while fungal cultures have low sensitivity and a long turn-around time. Non-cultural methods are fundamental for a rapid diagnosis of invasive fungal diseases and they include assays based on the detection of fungal antigens (galactomannan, Aspergillus-lateral flow device, [1,3]-β-D-glucan, mannan), antibodies, such as anti-mannan, and molecular tests. With the exception of some molecular methods for rare fungi, the non-cultural assays are usually applied to the diagnosis of invasive aspergillosis, invasive candidiasis and pneumocystosis. The performance of a single test or a combination of tests will be discussed, with particular focus on choosing the most appropriate marker(s) for every specific patient population. Reasons for potential false-positive or false-negative results will be discussed.