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

Dimethylcysteine (DiCys)/o-Phthalaldehyde Derivatization for Chiral Metabolite Analyses: Cross-Comparison of Six Chiral Thiols

Metabolomics profiling using liquid chromatography-mass spectrometry (LC-MS) has become an important tool in biomedical research. However, resolving enantiomers still represents a significant challenge in the metabolomics study of complex samples. Here, we introduced N,N-dimethyl-l-cysteine (dimethylcysteine, DiCys), a chiral thiol, for the o-phthalaldehyde (OPA) derivatization of enantiomeric amine metabolites. We took interest in DiCys because of its potential for multiplex isotope-tagged quantification. Here, we characterized the usefulness of DiCys in reversed-phase LC-MS analyses of chiral metabolites, compared against five commonly used chiral thiols: N-acetyl-l-cysteine (NAC); N-acetyl-d-penicillamine (NAP); isobutyryl-l-cysteine (IBLC); N-(tert-butoxycarbonyl)-l-cysteine methyl ester (NBC); and N-(tert-butylthiocarbamoyl)-l-cysteine ethyl ester (BTCC). DiCys and IBLC showed the best overall performance in terms of chiral separation, fluorescence intensity, and ionization efficiency. For chiral separation of amino acids, DiCys/OPA also outperformed Marfey’s reagents: 1-fluoro-2-4-dinitrophenyl-5-l-valine amide (FDVA) and 1-fluoro-2-4-dinitrophenyl-5-l-alanine amide (FDAA). As proof of principle, we compared DiCys and IBLC for detecting chiral metabolites in aqueous extracts of rice. By LC–MS analyses, both methods detected twenty proteinogenic l-amino acids and seven d-amino acids (Ala, Arg, Lys, Phe, Ser, Tyr, and Val), but DiCys showed better analyte separation. We conclude that DiCys/OPA is an excellent amine-derivatization method for enantiomeric metabolite detection in LC-MS analyses.

Expression and Purification along with Evaluation of Serological Response and Diagnostic Potential of Recombinant Sap2 Protein from C. parapsilosis for Use in Systemic Candidiasis

Systemic candidiasis is the fourth most common bloodstream infection in ICU patients worldwide. Although C. albicans is a predominant species causing systemic candidiasis, infections caused by non-albicans Candida (NAC) species are increasingly becoming more prevalent globally along with the emergence of drug resistance. The diagnosis of systemic candidiasis is difficult due to the absence of significant clinical symptoms in patients. We investigated the diagnostic potential of recombinant secreted aspartyl proteinase 2 (rSap2) from C. parapsilosis for the detection of Candida infection. The rSap2 protein was successfully cloned, expressed and purified using Ni-NTA chromatography under denaturing conditions using an E. coli-based prokaryotic expression system, and refolded using a multi-step dialysis procedure. Structural analysis by CD and FTIR spectroscopy revealed the refolded protein to be in its near native conformation. Immunogenicity analysis demonstrated the rSap2 protein to be highly immunogenic as evident from significantly high titers of Sap2-specific antibodies in antigen immunized Balb/c mice, compared to sham-immunized controls. The diagnostic potential of rSap2 protein was evaluated using immunoblotting and ELISA assays using proven candidiasis patient serum and controls. Immunoblotting results indicate that reactivity to rSap2 was specific to candidiasis patient sera with no cross reactivity observed in healthy controls. Increased levels of anti-Sap2-specific Ig, IgG and IgM antibodies were observed in candidiasis patients compared to controls and was similar in sensitivity obtained when whole Candida was used as coating antigen. In summary, the rSap2 protein from C. parapsilosis has the potential to be used in the diagnosis of systemic candidiasis, providing a rapid, convenient, accurate and cost-effective strategy.

The complex human urinary sugar profile: determinants revealed in the cross-sectional KarMeN study

Background

Although sugars and sugar derivatives are an important class of metabolites involved in many physiologic processes, there is limited knowledge on their occurrence and pattern in biofluids.

Objective

Our aim was to obtain a comprehensive urinary sugar profile of healthy participants and to demonstrate the wide applicability and usefulness of this sugar profiling approach for nutritional as well as clinical studies.

Design

In the cross-sectional KarMeN study, the 24-h urine samples of 301 healthy participants on an unrestricted diet, assessed via a 24-h recall, were analyzed by a newly developed semitargeted gas chromatography-mass spectrometry (GC-MS) profiling method that enables the detection of known and unknown sugar compounds. Statistical analyses were performed with respect to associations of sex and diet with the urinary sugar profile.

Results

In total, 40 known and 15 unknown sugar compounds were detected in human urine, ranging from mono- and disaccharides, polyols, and sugar acids to currently unknown sugar-like compounds. A number of rarely analyzed sugars were found in urine samples. Maltose was found in statistically higher concentrations in the urine of women compared with men and was also associated with menopausal status. Further, a number of individual sugar compounds associated with the consumption of specific foods, such as avocado, or food groups, such as alcoholic beverages and dairy products, were identified.

Conclusions

We here provide data on the complex nature of the sugar profile in human urine, of which some compounds may have the potential to serve as dietary markers or early disease biomarkers. Thus, comprehensive urinary sugar profiling not only has the potential to increase our knowledge of host sugar metabolism, but can also reveal new dietary markers after consumption of individual food items, and may lead to the identification of early disease biomarkers in the future. The KarMeN study was registered at drks.de as DRKS00004890.

The level of arabinitol in autistic children after probiotic therapy

OBJECTIVE

The level of D-arabinitol (DA) and the ratio of D-/L-arabinitol (DA/LA) in the urine of children with autism were investigated. The changes in DA/LA after probiotic treatment in urine samples of children with autism were studied.

METHODS

DA and LA and the DA/LA ratio were identified by capillary gas chromatography/mass spectrometry in urine before and after the probiotic therapy.

RESULTS

The level of DA is significantly higher (P < 0.05) in the urine of autistic children before (A) and after probiotic supplementation (A1) (160.04 ± 22.88 μmol/mmol creatinine and 89.53 ± 37.41 μmol/mmol creatinine, respectively). Nonetheless, the probiotic supplementation let to a significant decrease in DA and DA/LA and to a significant improvement in ability of concentration and carrying out orders.

CONCLUSION

The use of probiotics seems to be helpful in reducing the level of DA and the ratio of DA/LA in the urine of children with autism.

Prospective survey of (1→3)-beta-D-glucan and its relationship to invasive candidiasis in the surgical intensive care unit setting

Non-culture-based diagnostic strategies are needed for diagnosing invasive candidiasis (IC). We evaluated serial serum (1→3)-β-d-glucan (BG) levels in patients in the surgical trauma intensive care unit (SICU) patients with clinical evidence of IC. Serum samples from patients admitted to the SICU for a minimum of 3 days were collected twice weekly and analyzed for BG by using a Fungitell kit with a positive cutoff of ≥ 80 pg/ml. Diagnosis of IC was done using a set of predefined and validated clinical practice-based criteria. A total of 57 patients consented to participate and were enrolled. The median ICU stay was 16 days (range, 3 to 51). A total of 14 of 57 (25%) false positives were observed in the first sample (ICU day 3) and, overall, 73% of the day 3 samples had higher BG levels than subsequent samples. On the date of clinical diagnosis of IC, the sensitivity of a positive BG for identifying invasive candidiasis was 87%, with a 73% specificity. In patients with evidence of IC, the median BG value was significantly higher than those without evidence of IC (171 versus 48 pg/ml, P = 0.02), respectively. In the three patients with proven IC, BG was detected 4 to 8 days prior to diagnosis. BG serum detection may be a useful tool to aid in the early diagnosis of IC in SICU patients, particularly after day 3 and in patients with at least two positive samples drawn several days apart. Elevated BG levels within the first 3 days need to be further characterized.

Candida prosthetic infections: case series and literature review

Candida prosthetic joint infections are considered to be rare. We retrospectively studied patients treated for Candida prosthetic infections between 1 January 1995 and 31 December 2007 in our infectious diseases department, a tertiary referral centre. We identified 7 patients, 4 with knee and 3 with hip prosthetic infections. The most frequent fungal agent was Candida albicans (4 cases), followed by Candida parapsilosis (2 cases) and Candida guillermondii (1 case). All the patients received antifungal treatment for a prolonged period. Five patients had their prosthesis removed and 3 had reimplantation, 1 patient was treated with debridement and prosthetic retention, and the last patient refused surgery. The mean follow-up time was 2.5 y. At the last evaluation, 3 patients were considered as cured, 3 patients presented a secondary bacterial infection leading to amputation for 2 of them, and 1 patient died from heart failure. During Candida prosthetic joint infections, the epidemiological characteristics and the location of the prosthesis are very similar to bacterial prosthetic infections. The benchmark antifungal therapies remain amphotericin B and/or fluconazole.

Preparation of combined extract of cell wall and cytosol antigens of Candida albicans for immunoblot analysis

Immunoblot analysis is not in wide use for diagnosis of invasive candidiasis, mostly because the procedure is not standardized and hence not reliable. This work describes a standardized method for C. albicans antigen extract preparation and immunochemical detection. The major improvement of the method is the preparation of combined antigen extract -- consisting of the cell wall and cytosol antigens. The fungal cells and lysis buffer were mixed at a 1:3 ratio and disintegrated by ultrasound for six cycles of one minute each. After centrifugation, cytosol antigens were obtained in the supernatant and cell wall antigens were in the precipitate. Precipitate was dissolved in lysis buffer with 2% sodium dodecyl sulfate (SDS) and boiled at 100 degrees C for 2 min. After centrifugation, the supernatant was combined with the previous one, so the extract of the combined antigens was obtained in the mixture. With those combined antigen extracts and with sera of three different groups of patients, immunoblot analysis showed sensitivity of 90.2%, specificity of 84.4%, and accuracy of 88.0%.

Use of in vivo 13C nuclear magnetic resonance spectroscopy to elucidate L-arabinose metabolism in yeasts

Candida arabinofermentans PYCC 5603(T) and Pichia guilliermondii PYCC 3012 were shown to grow well on L-arabinose, albeit exhibiting distinct features that justify an in-depth comparative study of their respective pentose catabolism. Carbon-13 labeling experiments coupled with in vivo nuclear magnetic resonance (NMR) spectroscopy were used to investigate L-arabinose metabolism in these yeasts, thereby complementing recently reported physiological and enzymatic data. The label supplied in L-[2-(13)C]arabinose to nongrowing cells, under aerobic conditions, was found on C-1 and C-2 of arabitol and ribitol, on C-2 of xylitol, and on C-1, C-2, and C-3 of trehalose. The detection of labeled arabitol and xylitol constitutes additional evidence for the operation in yeast of the redox catabolic pathway, which is widespread among filamentous fungi. Furthermore, labeling at position C-1 of trehalose and arabitol demonstrates that glucose-6-phosphate is recycled through the oxidative pentose phosphate pathway (PPP). This result was interpreted as a metabolic strategy to regenerate NADPH, the cofactor essential for sustaining l-arabinose catabolism at the level of L-arabinose reductase and L-xylulose reductase. Moreover, the observed synthesis of D-arabitol and ribitol provides a route with which to supply NAD(+) under oxygen-limiting conditions. In P. guilliermondii PYCC 3012, the strong accumulation of L-arabitol (intracellular concentration of up to 0.4 M) during aerobic L-arabinose metabolism indicates the existence of a bottleneck at the level of L-arabitol 4-dehydrogenase. This report provides the first experimental evidence for a link between L-arabinose metabolism in fungi and the oxidative branch of the PPP and suggests rational guidelines for the design of strategies for the production of new and efficient L-arabinose-fermenting yeasts.

Diagnosis of invasive candidiasis by enzyme-linked immunosorbent assay using the N-terminal fragment of Candida albicans hyphal wall protein 1

BACKGROUND

The diagnosis of invasive candidiasis is difficult because there are no specific clinical manifestations of the disease and colonization and infection are difficult to distinguish. In the last decade, much effort has been made to develop reliable tests for rapid diagnosis of invasive candidiasis, but none of them have found widespread clinical use.

RESULTS

Antibodies against a recombinant N-terminal fragment of the Candida albicans germ tube-specific antigen hyphal wall protein 1 (Hwp1) generated in Escherichia coli were detected by both immunoblotting and ELISA tests in a group of 36 hematological or Intensive Care Unit patients with invasive candidiasis and in a group of 45 control patients at high risk for the mycosis who did not have clinical or microbiological data to document invasive candidiasis. Results were compared with an immunofluorescence test to detect antibodies to C. albicans germ tubes (CAGT). The sensitivity, specificity, positive and negative predictive values of a diagnostic test based on the detection of antibodies against the N-terminal fragment of Hwp1 by immunoblotting were 27.8 %, 95.6 %, 83.3 % and 62.3 %, respectively. Detection of antibodies to the N-terminal fragment of Hwp1 by ELISA increased the sensitivity (88.9 %) and the negative predictive value (90.2 %) but slightly decreased the specificity (82.6 %) and positive predictive values (80 %). The kinetics of antibody response to the N-terminal fragment of Hwp1 by ELISA was very similar to that observed by detecting antibodies to CAGT.

CONCLUSION

An ELISA test to detect antibodies against a recombinant N-terminal fragment of the C. albicans germ tube cell wall antigen Hwp1 allows the diagnosis of invasive candidiasis with similar results to those obtained by detecting antibodies to CAGT but without the need of treating the sera to adsorb the antibodies against the cell wall surface of the blastospore.

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.

Urinary D-arabinitol/L-arabinitol levels in infants undergoing long-term antibiotic therapy

Long-term antibiotic therapy is one of the main risk factors for mycosis. The urinary D-arabinitol/L-arabinitol (D-/L-ARA) ratio (a biomarker of several Candida species) was determined by gas chromatography with an electron capture detector in samples from 51 infants undergoing long-term antibiotic therapy. Although 47 of these children had higher D-/L-ARA ratios than healthy controls (P<0.0003), their values nonetheless remained within upper-normal limits (D-/L-ARA ratio of <3.6). Four children with suspected invasive candidiasis had above-normal ratios that normalized with fluconazole treatment.

Current literature in mass spectrometry

In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (5 Weeks journals ‐ Search completed at 8th. Sept. 2004)