Gas chromatographic determination of D-arabinitol/L-arabinitol ratios in urine: a potential method for diagnosis of disseminated candidiasis

Silver nanoparticles (AgNPs) based selective colorimetric sensor for the detection of D-arabinitol in a urine sample

D-arabinitol is a sugar alcohol that is a typical metabolite of Candida species. The hydroxy group owned by D-arabinitol can function as a reducing agent that can reduce Ag+ to AgNPs. The resulting colloid is further stabilized by the addition of a capping agent. The capping agent used in this study was a combination of chitosan 1%(w/w) and PEG 6000 1% (w/w) (2:1) v/v. The formation of AgNPs causes an increase in the surface plasmon resonance spectra of the colloid solution at a wavelength of 430 nm with a slight blue shift. At the same time, the color of the solution changes from colorless to yellow colloid so that the absorbance can be observed using a spectrophotometer. The change in the absorbance value of the colloid produced is proportional to the concentration of D-arabinitol added, so that the amount of D-arabinitol in the sample can be quantified. Under optimum conditions, the resulting method shows good linearity with an R2-value of 0.9979 in the concentration range of D-arabinitol 100-2000 μM and Vxo value is 4.30%. The detection limit is 115.11 μM and the quantification limit is 383.70 μM. The repeatability (%RSD) is 0.78-1.94 and the % recovery in addition to urine samples is 93.27-103.70. This method is quite selective for other components present in urine. The analysis time is short, the number of samples required is only small, and does not require an organic solvent, so this method has the potential to be used in determining the levels of D-arabinitol in urine samples.

Antifungal activity of polymethyl methacrylate/Si3N4 composites against Candida albicans

Previous studies using gram-positive and -negative bacteria demonstrated that hydrolysis of silicon nitride (Si₃N₄) in aqueous suspensions elutes nitrogen and produces gaseous ammonia while buffering pH. According to immunochemistry assays, fluorescence imaging, and in situ Raman spectroscopy, we demonstrate here that the antipathogenic surface chemistry of Si₃N₄ can be extended to polymethylmethacrylate (PMMA) by compounding it with a minor fraction (~8 vol.%) of Si₃N₄ particles without any tangible loss in bulk properties. The hydrolytic products, which were eluted from partly exposed Si₃N₄ particles at the composite surface, exhibited fungicidal action against Candida albicans. Using a specific nitrative stress sensing dye and highly resolved fluorescence micrographs, we observed in situ congestion of peroxynitrite (ONOO^-) radicals in the mitochondria of the Candida cells exposed to the PMMA/Si₃N₄ composite, while these radicals were absent in the mitochondria of identical cells exposed to monolithic PMMA. These in situ observations suggest that the surface chemistry of Si₃N₄ mimics the antifungal activity of macrophages, which concurrently produce NO radicals and superoxide anions (O₂•^-) resulting in the formation of candidacidal ONOO^-. The fungicidal properties of PMMA/Si₃N₄ composites could be used in dental appliances to inhibit the uncontrolled growth of Candida albicans and ensuing candidiasis while being synergic with chemoprophylaxis. STATEMENT OF SIGNIFICANCE: In a follow-up of previous studies of gram-positive and gram-negative bacteria, we demonstrate here that the antipathogenic surface chemistry of Si₃N₄ could be extended to polymethylmethacrylate (PMMA) containing a minor fraction (~8 vol.%) of Si₃N₄ particles without tangible loss in bulk properties. Hydrolytic products eluted from Si₃N₄ particles at the composite surface exhibited fungicidal action against Candida albicans. Highly resolved fluorescence microscopy revealed congestion of peroxynitrite (ONOO^-) radicals in the mitochondria of the Candida cells exposed to the PMMA/Si₃N₄ composite, while radicals were absent in the mitochondria of identical cells exposed to monolithic PMMA. The fungicidal properties of PMMA/Si₃N₄ composites could be used in dental appliances to inhibit uncontrolled growth of Candida albicans and ensuing candidiasis in synergy with chemoprophylaxis.

A novel molecular imprinting polymer for the selective adsorption of D-arabinitol from spiked urine

In this research, molecular imprinting polymers (MIPs) for D-arabinitol were synthesized using a bulk polymerization method through a noncovalent approach. The MIPs were prepared by using D-arabinitol as a template, acrylamide as a functional monomer, ethylene glycol dimethacrylateas cross-linker, benzoyl peroxide as an initiator and dimethyl sulfoxideas a porogen. MIPS was synthesized in several formulas with a different molar ratio of template to functional monomers and cross-linker. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize the MIPs produced. A batch rebinding assay was used to test the binding efficiency of each formula. Batch rebinding test results revealed that MIPsF3 with a molar ratio of the template: monomer and crosslinker ratio respectively (1: 4: 25) had the highest binding capacity at 1.56 mgg ^-1 . The results of isotherm adsorption showed that the MIPs produced followed the Freundlich equation with an R-value of 0.97. The MIPs produced was also selective toward its isomeric compounds (i.e. L-arabinitol, adonitol, xylitol, and glucose). The extraction efficiency of the MIPs against D-arabinitol was 88.98%.

Prospective evaluation of a combination of fungal biomarkers for the diagnosis of invasive fungal disease in high-risk haematology patients

We prospectively evaluated a combination of fungal biomarkers in adult haematology patients with focus on their clinical utility at different time points during the course of infection. In total, 135 patients were monitored once to twice weekly for serum (1-3)-ß-d-glucan (BG), galactomannan (GM), bis-methyl-gliotoxin and urinary d-arabinitol/l-arabinitol ratio. In all, 13 cases with proven or probable invasive fungal disease (IFD) were identified. The sensitivity of BG and GM at the time of diagnosis (TOD) was low, but within 2 weeks from the TOD the sensitivity of BG was 92%. BG >800 pg/mL was highly specific for IFD. At a pre-test probability of 12%, both BG and GM had negative predictive values (NPV) >0.9 but low positive predictive values (PPV). In a subgroup analysis of patients with clinically suspected IFD (pre-test probability of 35%), the NPV was lower, but the PPV for BG was 0.86 at cut-off 160 pg/mL. Among IFD patients, 91% had patterns of consecutively positive and increasing BG levels. Bis-methyl-gliotoxin was undetectable in 15 patients with proven, probable and possible IA. To conclude, BG was the superior fungal marker for IFD diagnosis. Quantification above the limit of detection and graphical evaluation of the pattern of dynamics are warranted in the interpretation of BG results.

Surface enhancement of a molecularly imprinted polymer film using sacrificial silica beads for increasingl-arabitol chemosensor sensitivity and detectability

Sacrificial silica beads, used for increasing the specific surface area of a molecularly imprinted polymer film, improve the performance of the chemosensor.

Determination of urinary D-/L-arabinitol ratios as a biomarker for invasive candidiasis in children with cardiac diseases

A non-invasive, non-culture-based method of determining urinary D-/L-arabinitol (D-/L-ARA) ratios was investigated as a tool for the diagnosis of invasive candidiasis in nosocomial paediatric infection cases. The study encompassed 138 children aged 4 days to 16 years (mean ± SD=1.6 ± 4.2 years) with congenital heart defects (91.4%) or with rhythm disorders or circulatory failure (8.6%). ARA enantiomers were detected by GC using an electron capture detector. Positive D-/L-ARA ratios were found for 11/11 patients with proven candidiasis and 17/19 patients with clinically suspected invasive candidiasis. Thirty children were undergoing antifungal chemotherapy. D-/L-ARA ratios (mean ± SD) were 2.601 ± 0.544 in hospitalized cardiac patients without fungal infection and 5.120 ± 1.253 in those receiving antifungal therapy (P<0.001). The sensitivity of the method was 100%, the specificity 97.2%, the positive predictive value was 78.6% and the negative predictive value was 100%.

Clinical experience of urine D-arabinitol/L-arabinitol ratio in the early diagnosis of invasive candidiasis in paediatric high risk populations

In 2 prospective studies, we previously reported on the early and accurate diagnosis of invasive candidiasis by determining the D-arabinitol/L-arabinitol (DA/LA) ratio in urine in neutropenic children with cancer at the paediatric oncology unit (POU) and in premature infants at the neonatal intensive care unit (NICU) at our hospital. In this retrospective study at the same units, we report how the DA/LA assay was implemented in clinical practice immediately after the prospective study periods. We found that, in the POU, the recommendation of regularly monitoring urine DA/LA ratios in patients at risk and considering antifungal therapy in the case of elevated ratios had been followed. A significant decrease in the incidence of culture positive invasive candidiasis may have been attributed to the introduction of the DA/LA assay. At the NICU, where the DA/LA assay was recommended only as an adjunct to other diagnostic tools, morbidity in invasive candidiasis remained unchanged. While regular monitoring of the urine DA/LA ratio probably facilitates the early detection of invasive candidiasis in paediatric oncology, it remains to be determined if the test can be used in a similar way in neonatal intensive care.

Measurement of serum D-arabinitol/creatinine ratios for initial diagnosis and for predicting outcome in an unselected, population-based sample of patients with Candida fungemia

D-Arabinitol (DA) is a useful diagnostic marker for candidiasis in patients with neutropenia and other high-risk groups, but its use in unselected patients with a broad range of underlying diseases and conditions has not been studied. We used an automated enzymatic fluorometric assay to measure serum DA/creatinine ratios (DA/cr's) in 30 healthy adults, 100 hospitalized controls without Candida fungemia, and 83 patients from a study of all Candida fungemias in Connecticut between October 1998 and September 1999. Sixty-three of 83 (76%) fungemic patients and 11 of 100 (11%) nonfungemic controls had serum DA/cr's >or=3.9 microM/mg/dl (mean + 3 standard deviations for 30 healthy adults). High serum DA/cr's were less frequent in patients with cancer or fungemia caused by the DA nonproducer Candida glabrata than in patients with cancer or fungemia caused by a DA producer, C. albicans, C. tropicalis, or C. parapsilosis. The serum DA/cr was first >or=3.9 microM/mg/dl before, on the same day as, or after the first positive blood culture was drawn for 30 (36%), 22 (27%), and 11 (13%) fungemia patients, respectively. Mortality did not differ significantly among the patients with high or normal initial or peak serum DA/cr's, but mortality was higher if any serum DA/cr value was >or=3.9 microM/mg/dl 3 or more days after the onset of fungemia (18/27 versus 4/24 patients, respectively; P < 0.001). We conclude that serum DA/cr's are useful both for the initial diagnosis of Candida fungemia and for prognostic purposes for unselected patients with a broad range of underlying diseases and conditions.

Development and application of a rapid diagnostic method for invasive Candidiasis by the detection of d-/l-arabinitol using gas chromatography/mass spectrometry

A rapid non-culture-based diagnostic method utilizing d-/l-arabinitol (DA/LA) ratios as a chemical marker of invasive candidiasis was developed and explored. The enantiomers-ratios detection was made possible by the use of gas chromatography coupled with mass spectrometry (GC/MS). The mean DA/LA ratios +/- standard deviation (range) in urine (n = 40) and serum (n = 20) were 2.08 +/- 0.78 (0.57 to 3.55) and 1.79 +/- 0.75 (0.74 to 3.54), respectively, from patients without evidence of fungal infection or colonization; in patients (n = 7) with culture-proven invasive candida infections, the figures were 9.91 +/- 3.04 (7.24 to 16.27) and 13.58 +/- 7.31 (5.57 to 25.88) in urine and serum, respectively. The differences in DA/LA ratios between the candidemic patients and the non-candidemic patients were statistically significant (p < 0.01) in both serum and urine samples. The DA/LA ratios were not significantly affected in patients with oral or vaginal candidiasis and candiduria.

Gas chromatographic determination of D-/L-arabinitol ratio in healthy Polish children

The D-/L-arabinitol enantiomers ratio (a marker of disseminated candidiasis of Candida species) in urine was determined by gas chromatography (GC) in 198 healthy Polish children ranging in age from 0 to 18 years. The urine samples were dry and trifluoroacetic anhydride (TFAA)-treated. Enantiomers derivatives were separated on a chiral column (beta-Dex 120, 60 m x 0.25 mm I.D.). A glass "solid-phase" injector and electron capture detector (ECD) were used. The ECD response was linear with correlation coefficients 0.999. The limit of detection was 0.02 micromol/l. Good results in terms of reproducibility, accuracy (RSD<10%, bias<6%), and linearity were obtained from real urine samples containing up to 400 micromol/l D-arabinitol. TFA-arabinitol derivatives in biological samples were stable from 1 to 5 days (depending on the arabinitol contents), while TFA-arabinitol standard derivatives were stable for 2 weeks. The identity of D- and L-arabinitol were confirmed by GC-MS analysis. The mean D-/L-arabinitol ratios ranged from 2.48 to 1.65 in the examined groups. The D-/L-arabinitol ratio was found to be exponentially regressive with age. A few cases of diagnosis of disseminated candidiasis by the GC method and confirmed by blood culture are described. The described GC method was also used for monitoring antifungal treatment of patients with disseminated candidiasis.

Urine D-arabinitol/L-arabinitol ratio in diagnosing Candida infection in patients with haematological malignancy and HIV infection

Adult patients with hematologic malignancies along with HIV infected patients were prospectively studied to determine the performance of urine D-arabinitol/L-arabinitol (DA/LA) ratio in diagnosing invasive candidiasis. Ten evaluable febrile neutropenic patients had proven invasive candidiasis and elevated DA/LA ratios were found in 5. Invasive candidiasis with normal DA/LA ratios was most frequently due to Candida krusei infection. This Candida species is a non-producer of arabinitol. Only 4 of 81 febrile neutropenic patients given either antifungal prophylaxis or empiric antifungal treatment had elevated DA/LA ratios. Only 1 of 15 HIV positive patients with either oropharyngeal or esophageal candidiasis had elevated DA/LA ratios. Widespread use of fluconazole prophylaxis in bone marrow transplantation patients at the study hospital has led to an increased prevalence of C. krusei infection. This is the likely reason for the low sensitivity of the test in proven and suspected invasive Candida infections reported here.

Urine D-arabinitol/L-arabinitol ratio in diagnosis of invasive candidiasis in newborn infants

Infants treated in neonatal intensive care units suffer an increased risk for invasive candidiasis, but the diagnosis is sometimes difficult. D-arabinitol is a metabolite of most pathogenic Candida species. An elevated urine D-arabinitol/L-arabinitol (DA/LA) ratio is a sensitive sign of invasive candidiasis in children with cancer, but the method has not been previously evaluated for newborn infants. We therefore enrolled 117 infants in a neonatal intensive care unit, and 411 urine samples were obtained on filter paper. The DA/LA ratio was measured by gas chromatography-mass spectrometry. For 81 infants with no suspicion of superficial or invasive candidiasis, the urine DA/LA ratio was 2.7 +/- 0.7 (mean +/- standard deviation [SD]). The upper cutoff level was set at 4.8 (mean plus 3 SD). Of 22 infants with mucocutaneous candidiasis and not given systemic antifungal treatment, two had elevated DA/LA ratios, which normalized after removal of intravascular catheters. Eight other infants were given empiric antifungal treatment but had negative cultures; five of these had repeatedly elevated DA/LA ratios. Six infants with culture-positive invasive candidiasis all had one or more samples with elevated ratios. For seven infants, three with suspected and four with confirmed invasive candidiasis (for which follow-up samples were available), ratios normalized during antifungal treatment. In conclusion, urine DA/LA ratio determination is a rapid test and can be used for newborns. It is possibly more sensitive than fungal blood cultures in the diagnosis of invasive candidiasis and can also be used for monitoring the effect of antifungal treatment.

D-arabinitol--a marker for invasive candidiasis

The five-carbon sugar alcohol D-arabinitol (DA) is a metabolite of most pathogenic Candida species, in vitro as well as in vivo, and can be determined by gas chromatography or enzymatic analysis. Endogenous DA and L-arabinitol (LA) are present in human body fluids, and serum DA and LA increase in renal dysfunction. In prospective clinical studies, elevated DA/LA or DA/creatine ratios in serum or urine have been found in immunocompromised, usually neutropenic, patients with invasive candidiasis. In addition, positive DA results have been obtained several days to weeks before positive blood cultures, and the normalization of DA levels has been correlated with therapeutic response in both humans and animals. However, to date, only a few prospective studies have been conducted in which adequate analytical methods were used. Thus, further investigation of various patient groups is needed to establish the applicability of the 'arabinitol method' in the diagnostic battery for invasive Candida infections.

PCR and other non-culture methods for diagnosis of invasive Candida infections in allogeneic bone marrow and solid organ transplant recipients

In this prospective study 197 serum and 152 urine samples were collected from 40 bone marrow and solid organ transplant recipients with clinically suspected invasive fungal infection before, during and after empirical treatment with lipid formulation of amphotericin B or fluconazole. Serum was analysed by Candida polymerase chain reaction (PCR) and urine by measurement of D/L-arabinitol ratio. One serum from each patient was also tested for concentration of (1-->3)-beta-glucan and two commercial Candida antigens. Invasive fungal infection was diagnosed in four candidosis and one aspergillosis patients (13%). Positive PCR, elevated D/L-arabinitol ratio, (1-->3)-beta-glucan concentration and antigens were detected in nine, 15, 17, and seven patients, respectively. The agreement between PCR and D/L-arabinitol assays was poor. However, 56% agreement was observed between positive PCR and beta-glucan and/or antigen assays, and 60% agreement between positive D/L-arabinitol and beta-glucan and/or antigen assays. Combination of several non-culture assays is needed to diagnose invasive fungal infection in high-risk transplant recipients. No single test was sufficient for diagnosis.

Allogeneic bone marrow transplantation for hematological malignancies--controversies and recent advances

Today more than 80000 allogeneic bone marrow transplantations (BMT) have been performed worldwide. The major indications are hematological malignancies such as acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML) and myelodysplastic syndromes. Unrelated donors are increasingly used and there are around 4 million volunteer donors available in different registers, the largest being the National Marrow Donor Program. Molecular typing has improved the typing technique which has resulted in a decreased risk of graft-versus-host disease (GVHD), lower transplant-related mortality (TRM) and improved leukemia-free survival (LFS). Using HLA-identical siblings, patients with AML in first complete remission (1 CR) and high-risk ALL in 1 CR are clear indications for BMT. However, if an HLA-identical sibling is not available, it is not known today if an unrelated bone marrow or autografting is the best option for all patients with acute leukemia in 1 CR. Because BMT is the only curable treatment for CML, a search for an unrelated donor should start as soon as it is evident that an HLA-identical sibling is not available. BMT within a year from diagnosis is of major importance for outcome. Allogeneic peripheral blood progenitor cells (PBPC) have been used as an alternative to bone marrow. Preliminary studies indicate a faster engraftment, but prospective randomized trials are necessary to establish the role of allogeneic PBPC. Umbilical cord blood has also been used as a source of allogeneic hematopoietic stem cells. Using cord blood from HLA-identical siblings, engraftment seems to be delayed, but the probability of GVHD is low. Preliminary data using unrelated cord blood cells are encouraging. GVHD has an important antileukemic effect. Recently, a graft-versus-myeloma and a graft-versus-breast-cancer effect has been demonstrated. In patients who relapse after BMT, donor lymphocytes can induce remission, especially in patients with CML. With molecular techniques it is possible to detect relapse at an early stage, so called minimal residual disease. Liposomal amphotericin B has few side-effects and decreased the death rate by invasive fungal infection in BMT recipients. Early diagnosis and treatment of cytomegalovirus (CMV) infection with new antiviral drugs have dramatically reduced the incidence and mortality in CMV disease. Cyclosporine combined with methotrexate is today the most widely used immunosuppressive regimen and has decreased GVHD and improved survival. However, several new immunosuppressive drugs need to be explored in clinical BMT. Immune modulation by for instance cytokines and cytokine inhibititors is a new exciting development.

Use of gas chromatography-ion trap tandem mass spectrometry for the detection and characterization of microorganisms in complex samples

Gas chromatography-mass spectrometry (GC-MS) can be applied to detect and characterize microorganisms in clinical and environmental samples, and microbial contaminants in biotechnological production cultures. With this approach, unique microbial monomeric compounds, known as chemical markers, are used as analytes. In the present article, two GC-MS-based techniques, viz. GC-ion trap tandem MS (GC-MS-MS) and conventional quadrupole GC-MS used in the selected ion monitoring mode, were compared regarding their ability to detect 3-hydroxy fatty acids, muramic acid, and ergosterol (markers for endotoxin, peptidoglycan, and fungal biomass, respectively) in complex matrices. When using GC-MS-MS, daughter ion spectra were obtained for all markers present in amounts close to the detection limit of the GC-MS. Ion-trap GC-MS-MS shows great promise as a chemical marker analysis technique for application in clinical diagnosis, occupational and public health care, and biotechnology.

Diagnosis of invasive candidiasis in neutropenic children with cancer by determination of D-arabinitol/L-arabinitol ratios in urine

Determination of D-arabinitol/L-arabinitol ratios (referred to as D/L-arabinitol ratios) in urine as a tool for the diagnosis of invasive candidiasis was investigated in a prospective study comprising 100 children with cancer. The analyses were made by gas chromatography. Positive D/L-arabinitol ratios were found for 10 of 10 children with confirmed invasive candidiasis, 12 of 23 patients undergoing empiric antifungal chemotherapy, and 4 of 67 children not receiving antifungal treatment. D/L-Arabinitol ratios were positive 3 to 31 days (median, 12 days) before the first culture-positive blood sample was drawn or empiric therapy was initiated. The regular monitoring of D/L-arabinitol ratios in urine holds great promise as a sensitive method for diagnosing invasive candidiasis in immunocompromised children with cancer. Moreover, it may be possible to use an early rise in D/L-arabinitol ratios as a basis for the institution of antifungal chemotherapy and as a means of avoiding unnecessary treatment with potentially toxic antifungal agents.

Clinical and laboratory diagnosis of invasive candida infection in neutropenic patients

Cancer patients, especially those with acute leukaemia, represent a group that has the greatest risk for deep fungal infection. Almost no cases were seen before the advent of modern chemotherapy, and prior to the availability of antibacterial agents, less than 5% of patients with acute leukaemia died of fungal infection. These infections are now responsible for 40% or more of the deaths at some institutions. Candida species continues to be the most common fungal pathogen. Rapid and specific diagnosis of invasive candiosis enabling early effective therapy is therefore an important measure for reducing mortality in patients. Here the current status of clinical and laboratory diagnosis of invasive candida infection in neutropenic patients is discussed and recommendations made as to future development programmes.

Diagnosis of disseminated candidiasis by measurement of urine D-arabinitol/L-arabinitol ratio

Relative amounts of D-arabinitol (fungal origin) and L-arabinitol (part of normal human metabolism) in urine were determined by gas chromatography and mass spectrometry from 61 hospitalized patients with hematological malignancies. Seventeen neutropenic patients with acute leukemia (with 53 samples) had disseminated yeast infections and received empiric antifungal therapy before confirmation of the diagnosis. Control groups consisted of 22 hematologic patients (76 samples) with either mucosal (n = 10) or urinary (n = 12) Candida colonization and 22 neutropenic patients (34 samples) with no clinical or laboratory signs of invasive yeast infection. Reference values were also obtained from 50 healthy adults (50 samples). The mean urine D-arabinitol/L-arabinitol ratio +/- standard deviation (range) was 16.91 +/- 41.79 (1.41 to 254.75) in patients with disseminated infection, 2.73 +/- 2.48 (1.11 to 19.00) in colonized hematologic patients, 2.12 +/- 0.84 (1.16 to 5.84) in neutropenic controls, and 1.95 +/- 0.34 (0.97 to 3.44) in healthy adults (P < 0.001 between patients with disseminated infection and all control groups). The sensitivity and specificity of the assay for detecting disseminated yeast infection were, respectively, 88 and 91% per patient (upper limit of normal, 4.00). Seventy-one percent of patients already expressed elevated values at the onset of empiric antifungal therapy. The diagnosis of disseminated infection was confirmed on average 21.7 days after the first elevation of the D-arabinitol/L-arabinitol ratio. The method contributes to diagnosis of disseminated yeast infection and helps in monitoring patients at risk, to support the initiation of antifungal therapy at an early stage of the disease.