Enzymatic fluorometric method for the determination of D-arabinitol in serum by initial rate analysis

Pseudomonas fluorescens mannitol 2-dehydrogenase and the family of polyol-specific long-chain dehydrogenases/reductases: sequence-based classification and analysis of structure-function relationships

Multiple sequence alignment and analysis of evolutionary relationships have been used to characterize a family of polyol-specific long-chain dehydrogenases/reductases (PSLDRs). At the present time, 66 known and putative NAD(P)H-dependent oxidoreductases of mainly prokaryotic origin and between 357 and 544 amino acids in length constitute this family. The family is shown to include D-mannitol 2-dehydrogenase, D-mannonate 5-oxidoreductase, D-altronate 5-oxidoreductase, D-arabinitol 4-dehydrogenase, and D-mannitol-1-phosphate 5-dehydrogenase which form individual sub-families (defined by internal sequence identity of >/=30%) having distant origin and divergent substrate specificity but clearly displaying entire-chain relationship. When all forms are aligned, only three residues, Gly-33, Asp-230, and Lys-295 (in the numbering of Pseudomonas fluorescens D-mannitol 2-dehydrogenase (PsM2DH)) are strictly conserved. By combining sequence alignment with the known structure of PsM2DH and results from site-directed mutagenesis, we have developed a structure/function analysis for the family. Gly-33 is in the N-terminal coenzyme-binding domain and part of a nucleotide fingerprint region for the family, and Asp-230 and Lys-295 are at an interdomain segment contributing to the active site in which the lysine likely functions as the catalytic general acid/base. PSLDRs do not require a metal cofactor for activity and are specific for transferring the 4-pro-S hydrogen from NAD(P)H. Comparisons reveal that the core part of the two-domain fold has been conserved throughout all family members, perhaps reflecting the recruitment of a stable oxidoreductase structure and extensive trimming thereof to acquire functional properties specific to each sub-family. They also identify interactions that define the chemical mechanism of oxidoreduction and likely contribute to substrate and co-substrate specificities and are thus relevant for protein engineering.

Current status of nonculture methods for diagnosis of invasive fungal infections

The incidence of invasive fungal infections has increased dramatically in recent decades, especially among immunocompromised patients. However, the diagnosis of these infections in a timely fashion is often very difficult. Conventional microbiologic and histopathologic approaches generally are neither sensitive nor specific, and they often do not detect invasive fungal infection until late in the course of disease. Since early diagnosis may guide appropriate treatment and prevent mortality, there has been considerable interest in developing nonculture approaches to diagnosing fungal infections. These approaches include detection of specific host immune responses to fungal antigens, detection of specific macromolecular antigens using immunologic reagents, amplification and detection of specific fungal nucleic acid sequences, and detection and quantitation of specific fungal metabolite products. This work reviews the current status and recent developments as well as problems in the design of nonculture diagnostic methods for invasive fungal infections.

New enzymatic method for determining D-arabinitol in serum

A new reagent has been developed to determine D-arabinitol. This utilizes D-arabinitol 2-oxidoreductase derived from Bacillus sp. with high stability, and water-soluble tetrazolium salt, that can detect NADH with high sensitivity. Since this enzyme does not react to D-mannitol, elimination of D-mannitol is unnecessary. Thus, this is a much simpler process than currently available with commercial kits use D-arabinitol 4-oxidoreductase. The within-run and between-run precisions (CV) were 2.4-6.9% and 3.1-8.7%, respectively, whilst the correlation (r) between the results obtained with our proposed method (y) and those obtained with the commercial "Arabinitec-auto" kit (x) was 0.964 (y = 1.02x + 0.933 mumol/l; n = 69). However, some samples deviated remarkably from correlation in both methods. Our analyzing accuracy is satisfactory in clinical application, as it does not miss positive sample over cut-off value. We are refining this method by investigating why some specimens are apart from correlation significantly.

Measurement of (1-->3)-beta-D-glucan in an experimental model of systemic candidiasis

To investigate the utility of measuring blood concentrations of (1-->3)-beta-D-glucan, a component of the fungal cell wall, as an auxiliary diagnostic method for systemic candidiasis, rats were inoculated with Candida albicans and the number of C. albicans in the viscera and glucan in the blood were quantitated. The concentration of blood glucan and the number of C. albicans in the viscera were also measured both under leukopenia and with deteriorated reticuloendothelial system cell function, and when the liver and spleen had been excised. As a result, systemic candidiasis appeared in the group with leukopenia, and the number of living C. albicans increased in the kidney and liver. Together with this increase in the number of C. albicans, there was an increase in blood (1--> 3)-beta-D-glucan. Measurements of blood (1--> 3)-beta-D-glucan well reflect a proliferation of C. albicans in vivo, which would make this a useful auxiliary for the clinical diagnosis of systemic mycosis.

A rapid, automated enzymatic fluorometric assay for determination of D-arabinitol in serum

A rapid enzymatic fluorometric assay for measuring D-arabinitol in serum was developed using recombinant D-arabinitol dehydrogenase from Candida albicans (rArDH). rArDH was produced in Escherichia coli and purified by dye-ligand affinity chromatography. rArDH was highly specific for D-arabinitol, cross-reacting only with xylitol (4.9%) among all polyols tested. A Cobas Fara II centrifugal autoanalyzer (Roche) was used to measure NADH fluorometrically when rArDH and NAD were added to serum extracts, and D-arabinitol concentrations were calculated from standard curves derived from pooled human serum containing known amounts of D-arabinitol. The method was precise (mean intra-assay coefficients of variation [CVs], 0.8%, and mean interassay CVs, 1.6%) and rapid (3.5 min per assay) and showed excellent recovery of added D-arabinitol in serum (mean recovery rate, 101%). The mean and median D-arabinitol/creatinine ratios were 2.74 and 2.23 microM/mg/dl, respectively, for the 11 patients with candidemia compared to 1.14 and 1.23 microM/mg/dl, respectively, for 10 healthy controls (P < 0.01). These results confirm earlier studies showing that serum D-arabinitol measurement may help to promptly diagnose invasive candidiasis. The technique shows a significant improvement in terms of accuracy, cost, simplicity, specificity, and speed compared with gas chromatography, mass spectrometry, and earlier enzymatic assays.

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.

Diagnosis and therapeutic monitoring of invasive candidiasis by rapid enzymatic detection of serum D-arabinitol

BACKGROUND

Using a rapid automated enzymatic assay, we prospectively investigated serum D-arabinitol (DA), a biochemical marker of invasive candidiasis, in a large population of high-risk patients to determine its potential diagnostic, therapeutic, and prognostic significance in invasive candidiasis.

PATIENTS AND METHODS

A total of 3,223 serum samples were collected from 274 patients with cancer. Serum DA concentrations were determined in coded serum samples analyzed by rapid enzymatic assay. Creatinine also was analyzed in the same system to determine a serum DA and creatinine ratio (DA/Cr). The sensitivity, specificity, correlation with therapeutic response, and prognostic significance were analyzed for all patient study groups.

RESULTS

A DA/Cr of > or = 4.0 mumol/L per mg/dL was detected in 31 (74%) of all 42 cases of fungemia and 25 (83%) of the 30 cases of the subset of persistent fungemia. Elevated DA/Cr was detected in 4 (40%) of 10 patients with tissue-proven, deeply invasive candidiasis and negative blood cultures (eg, hepatosplenic candidiasis or localized abscess) and 7 (44%) of 16 cases of deep mucosal candidiasis (eg, esophageal candidiasis). Elevated serial DA/Cr levels also were detected in persistently febrile and granulocytopenic patients requiring empirical amphotericin B. Among 26 assessable cases of fungemia, abnormally elevated DA/Cr values were detected in 14 (54%) before, 10 (38%) after, and 2 (8%) simultaneously with the first microbiologic report of fungemia. The trends of serial DA/Cr values correlated with therapeutic response in 29 (85%) of 34 patients with assessable cases of fungemia, decreasing in 8 (89%) of 9 patients with clearance of fungemia and increasing in 21 (84%) of 25 patients with persistence of fungemia. Among the 34 assessable patients with fungemia, mortality was directly related to the trend of serial DA/Cr determinations over time: 71% among fungemic patients who had persistently elevated or increasing DA/Cr, and 18% among the fungemic patients who had resolving DA/Cr or never had elevated DA/Cr (P < 0.01).

CONCLUSIONS

Rapid enzymatic detection of DA in serially collected serum samples from high-risk cancer patients permitted detection of invasive candidiasis, early recognition of fungemia, and therapeutic monitoring in DA-positive cases. Serially collected serum DA determinations complement blood cultures for improving detection and monitoring therapeutic response in patients at risk for invasive candidiasis.

D-arabinitol versus mannan antigen and candidal protein antigen as a serum marker for Candida pyelonephritis

To evaluate serum markers for the diagnosis of Candida pyelonephritis, levels of D-arabinitol, candidal mannan antigen and candidal protein antigen were measured using an enzymatic fluorometric assay, an enzyme immunoassay and a latex agglutination assay, respectively. The study group comprised 36 patients with candiduria (11 disseminated candidiasis, 9 Candida pyelonephritis and 16 colonization) and 27 without candiduria. The D-arabinitol/creatinine ratio was the only marker that differentiated between Candida pyelonephritis and colonization (p < 0.01). Using the cut-off values (1.4 mumol/mg of D-arabinitol/creatinine ratio, 0.28 of mannan/creatinine ratio (x 10(4)) and 1:4 of protein antigen titer) D-arabinitol/creatinine ratio showed the highest sensitivity in Candida pyelonephritis (77.8%) as compared to mannan/creatinine ratio (55.6%) and protein antigen titer (11.1%) although there were no differences in specificity, positive predictive value or negative predictive value. These results suggest that D-arabinitol/creatinine ratio is the most useful marker of Candida pyelonephritis.

Trichosporon cutaneum fungemia in patients with acute myeloblastic leukemia and measurement of serum D-arabinitol, Candida antigen (CAND-TEC), and beta-D-glucan

Two patients with acute myeloblastic leukemia are described who developed fungemia due to Trichosporon cutaneum. Fungemia occurred at the leukocyte nadir following the administration of anti-cancer chemotherapy. One patient was cured but the other died. Both patients received prednisolone continuously and had central venous catheters in place for parenteral hyperalimentation. T. cutaneum isolates were resistant to 5-fluorocytosine and moderately susceptible to fluconazole. One case was complicated by endophthalmitis due to T. cutaneum; this is the second report of such a complication in the world. We investigated the serum levels of beta-D-glucan, D-arabinitol, and Candida antigen (CAND-TEC); beta-D-glucan was elevated in both cases, which suggests that simultaneous measurements of these laboratory values are useful for the diagnosis and possibly for the evaluation of therapy for this fungal infection.

Serum D-arabinitol measured by automated quantitative enzymatic assay for detection and therapeutic monitoring of experimental disseminated candidiasis: correlation with tissue concentrations of Candida albicans

In order to further understand serum D-arabinitol (DA) as a marker for the diagnosis of disseminated candidiasis and for monitoring response to antifungal therapy, we studied the serum levels of this Candida carbohydrate metabolite by rapid automated enzymatic assay in rabbits with experimental disseminated candidiasis. The enzymatic reaction steps were performed on a standard automated clinical chemistry analyser. As a correction for renal impairment, data were expressed as serum D-arabinitol/creatinine ratio (DA/Cr). Serum creatinine concentrations were determined from the same sample with the same instrument, thereby allowing rapid determination of the DA/Cr within one laboratory. The DA/Cr was determined in 321 samples from 132 rabbits. The mean serum DA/Cr in 31 normal non-infected rabbits was 1.51 +/- 0.2 microM mg-1 dl-1. Among 84 rabbits with disseminated candidiasis and pre-terminal samples, there was a direct correlation between DA/Cr and tissue concentration of Candida albicans (r = 0.80; P < 0.001). A threshold of elevated DA/Cr (> or = 3.0 microM mg-1 dl-1) was evident in rabbits with a tissue concentration of C. albicans > or = 3 x 10(4) colony forming units (CFU) g-1. Elevated DA/Cr was detected in 48 (89%) of 54 rabbits at a C. albicans tissue concentration of > or = 3 x 10(4) CFU g-1 vs. one (3%) of 30 rabbits with < 3 x 10(4) CFU g-1 (P < 0.0001). Among all 101 rabbits with disseminated candidiasis, an elevated DA/Cr was detected at any point during infection in 60 (92%) of 65 rabbits having a C. albicans tissue concentration > or = 3 x 10(4) CFU g-1 vs. 13 (36%) of 36 rabbits with < 3 x 10(4) CFU g-1 (P < 0.0001). The relationship between the tissue response to antifungal therapy and change in DA/Cr was then further analysed. Ten (91%) of 11 rabbits with a tissue-proven response to antifungal therapy (defined as > or = 10(2)-fold reduction of CFU g-1 in comparison to untreated controls) had a > 50% reduction in elevated DA/Cr levels. By comparison, 10 (83%) of 12 treated rabbits with no response to therapy had persistently elevated DA/Cr levels (P < 0.001). These findings provide an experimental basis for understanding the patterns of expression of serum DA in disseminated candidiasis and further indicate that serial DA/Cr measurements may be useful for diagnosis and therapeutic monitoring of disseminated candidiasis.

Diagnosis and monitoring of disseminated candidiasis based on serum/urine D/L-arabinitol ratios

Disseminated candidiasis, a devastating disease with high morbidity and mortality in immunosuppressed patients, is difficult to diagnose because of the protean nature of symptoms and the lack of rapid and reliable laboratory diagnostic procedures. The subject of this review is the status of gas chromatographic-mass spectrometric techniques for the determination of D-arabinitol, a unique metabolite of pathogenic Candida species, in serum and urine. The enantiomers are separated by chiral chromatography followed by specific and sensitive detection using chemical ionization and selected ion monitoring. Using D/L-arabinitol ratios, instead of individual concentrations, eliminates the need for knowing the volume of samples and for calibration curves. A new filter paper technique requires only an unmeasured drop of whole blood (venous or finger/heel puncture) or urine; paper spots are mailable. Parallel determinations of D/L-arabinitol ratios in serum and urine in normal subjects and cancer patients with both normal and increased D/L-arabinitol ratios revealed constant (1.2-1.3 range) ratios of serum D/L-arabinitol/urine D/L-arabinitol for all populations studied. Analyzing two body fluids taken at the same time increases reliability by reducing false positives.

An automated enzymatic method for measurement of D-arabinitol, a metabolite of pathogenic Candida species

An automated enzymatic method was developed for the measurement of D-arabinitol in human serum. The assay is based on a novel, highly specific D-arabinitol dehydrogenase from Candida tropicalis. This enzyme catalyzes the oxidation of D-arabinitol to D-ribulose and the concomitant reduction of NAD+ to NADH. The NADH produced is used in a second reaction to reduce p-iodonitrotetrazolium violet (INT) to INT-formazan, which is measured spectrophotometrically. The entire reaction sequence can be performed automatically on a COBAS MIRA-S clinical chemistry analyzer (Roche Diagnostic Systems, Inc., Montclair, N.J.). Replicate analyses of human sera supplemented with D-arabinitol over a concentration range of 0 to 40 microM demonstrated that the pentitol could be measured with an accuracy of +/- 7% and a precision (standard deviation) of +/- 0.4 microM. Serum D-arabinitol measurements correlated with those determined by gas chromatography (r = 0.94). The enzymatic method is unaffected by L-arabinitol, D-mannitol, or other polyols commonly found in human serum. Any of 17 therapeutic drugs potentially present in serum did not significantly influence assay performance. Data illustrating the application of the assay in patients for possible diagnosis of invasive candidiasis and the monitoring of therapeutic intervention are presented. The automated assay described here was developed to facilitate the investigation of D-arabinitol as a serum marker for invasive Candida infections.

Nonculture methods for diagnosis of disseminated candidiasis

Two of the nonculture approaches to the diagnosis of DC, enzymatic-fluorometric determination of serum D-arabinitol and detection of marker antigens in antigenemia (enolase and CWMP), have been commercialized and have shown promise in limited clinical trials. These approaches are not new but are the culmination of efforts made over 10 or more years. Clearly, further fine-tuning of both metabolite and antigen detection is needed to simplify the methods and to improve their sensitivity and specificity so that they will be valuable in guiding clinical treatment decisions. An alternative approach, detection of DC by DNA amplification methods such as PCR, is a special case of a compelling technology and one that is capable of standardization across microbial genera. The availability of simplified PCR diagnostic methods for DC remains a tantalizing prospect. Nevertheless, the development of methods to release DNA from very small numbers of Candida organisms in the blood in a form that is sufficiently free of inhibitors of PCR will require further intensive effort. The maturation of these converging laboratory approaches to nonculture diagnosis of DC leads to more optimism about the eventual use of these methods in clinical laboratories.

Diagnostic value of determination of serum mannan concentrations in patients with candiduria

The diagnostic value of determination of serum mannan levels was studied in 41 patients with candiduria and 20 control patients without candiduria. The patients with candiduria comprised 18 asymptomatic afebrile patients (group 1) and 23 febrile patients with suspected Candida pyelonephritis (group 2). Mannan antigenemia (> or equal to 0.5 ng/ml) was detected in 14 patients in group 2, this rate being significantly higher than the rate of four patients in group 1 (p < 0.05) and none in the control group (p < 0.01). Serum mannan levels decreased gradually and became undetectable in six patients in whom therapy with an anticandidal agent was effective. Determination of serum mannan levels may be a useful parameter in diagnosing Candida pyelonephritis and deciding on effective treatment.

An evaluation of serodiagnostic tests in patients with candidemia: beta-glucan, mannan, candida antigen by Cand-Tec and D-arabinitol

The serodiagnostic tests, beta-glucan, mannan, candida antigen by Cand-Tec, and D-arabinitol were evaluated in 10 patients with candidemia, 14 patients with suspected fungemia, and 10 healthy persons. By blood culture or lysis centrifugation, C. albicans was isolated from 5 patients, C. parapsilosis from 4, and C. tropicalis from 1 patient; no organisms were isolated from the 14 patients with suspected fungemia or the 10 healthy subjects. Beta-glucan was measured by the difference between two chromogenic limulus tests (Endotoxin test-D and Endospecy), which was more than 60 pg/ml in 7 of 9 (78%) candidemic patients and 1 of 12 (8%) patients with suspected fungemia. Mannan was positive in 6 of 10 (60%) candidemic patients and 1 of 13 (8%) patients with suspected fungemia. Both antigens were very sensitive and highly specific for candidemia. However, the Cand-Tec assay was less specific, because titers of more than 4 were observed in 5 of 14 (34%) patients with suspected fungemia. D-Arabinitol was the least sensitive, because a D-arabinitol/creatinine ratio greater than 2.0 mumol/mg was observed in only 2 of 7 (29%) candidemic patients. The titers of serodiagnostic tests decreased after successful treatment with an anti-fungal agent. Our results show that the combined use of the assays in necessary for accurate serological diagnosis of candidemia.

Increased D-arabinitol/creatinine ratio in sera of patients with Behçet's disease during an active phase

The ratios of D-arabinitol (a major metabolite of Candida species) to creatinine were examined in 46 sera of 40 patients with ocular inflammatory disease and in 50 age-matched normal controls (25 men and 25 women). The mean ratio in patients with endogenous Candida endophthalmitis was higher than in the normal controls. Seven samples taken from patients with Behçet's disease during an active phase showed higher values than in the controls. Fourteen patients with Behçet's disease in remission showed D-arabinitol/creatinine values within normal range. In four patients with sarcoidosis, in two patients with Vogt-Koyanagi-Harada disease, and in 16 patients with bilateral uveitis of an unknown cause, the ratios were within normal range. It is possible that D-arabinitol, or a metabolite of Candida species, may be related in part to the active phase of Behçet's disease.

Detection of serum Candida antigens by enzyme-linked immunosorbent assay and a latex agglutination test with anti-Candida albicans and anti-Candida krusei antibodies

Serum samples from 197 patients with and without candidiasis were assayed for Candida albicans mannan and Candida krusei mannan by an enzyme-linked immunosorbent assay (ELISA) and a latex agglutination test (LA) and for D-arabinitol by the enzymatic fluorometric method. Of the 43 patients positive for C. albicans mannan (> or = 0.2 ng/ml), 34 were infected with C. albicans and 9 were infected with Candida tropicalis. C. krusei mannan (> or = 0.3 ng/ml) was detected in 10 patients infected with Candida parapsilosis, 2 patients infected with Candida guilliermondii, and 1 patient infected with C. krusei. With both anti-C. albicans antibodies and anti-C. krusei antibodies, the sensitivities of ELISA and LA for detection of invasive candidiasis (58 patients) were 74 and 38%, respectively. No false-positive reactions were observed by the ELISA or the LA. The sensitivity and specificity of the D-arabinitol/creatinine ratio (> or = 1.5 mumol/mg) to invasive candidiasis were 50 and 91%, respectively. The ELISA with antibodies against both C. albicans and C. krusei may be useful in diagnosing invasive candidiasis caused by medically important Candida strains excluding Candida glabrata.

Comparison of antibody, antigen, and metabolite assays for hospitalized patients with disseminated or peripheral candidiasis

Repeat serum samples from 22 patients with proven disseminated candidiasis and 42 with simple peripheral colonization were assayed for Candida antibodies by coelectrosyneresis, immunoprecipitation, and A and B immunofluorescence, for metabolites by D-arabinitol measurement, and for antigens by the mannan immunoassay and Cand-tec latex agglutination (mean number of samples tested, 2.5 per patient). For the antibody and metabolite assays, the results showed no statistical difference between the two groups. By contrast, the results of both antigen assays were positive for a significantly larger number of patients with disseminated candidiasis than of those with simple peripheral colonization. Results were regardless of whether the patients were neutropenic. They were not predictive of death. We calculated that the mannan antigen assay had 29% sensitivity and 97% specificity for the diagnosis of disseminated candidiasis. Likelihood ratios of a positive and a negative result of this test were 9.2 and 0.7, respectively, for this diagnosis. In the latex agglutination test, likelihood ratios were 2.5, 1.5, 1.6, and 0.3 when the test was positive for dilutions of 1/8, 1/4, and 1/2 and was negative, respectively.

Separation and quantification by gas chromatography-mass spectrometry of arabinitol enantiomers to aid the differential diagnosis of disseminated candidiasis

To differentiate increased arabinitol due to fungal (only D-arabinitol) and non-fungal origin, O-trifluoroacetyl derivatives of the enantiomers were separated using alpha-perpentylated cyclodextrin columns and measured by selected ion monitoring. Mean +/- S.D. D/L in normal serum: 1.40 +/- 0.42. D/L ratios greater than 2.24, defined as normal mean + 2S.D., were considered outside normal range. D/L was greater than 2.2 in 10 of 12 confirmed candidiasis cases with one false negative and one borderline. Renal dysfunction without candidiasis yielded normal D/L despite high arabinitol concentrations. D/L in normal urine was nearly identical to that in serum despite 60 times larger concentration. D/L ratios, determined by peak heights or areas, could be used without the need to determine concentrations.

Effects of gastrointestinal candidiasis, antibiotics, dietary arabinitol, and cortisone acetate on levels of the Candida metabolite D-arabinitol in rat serum and urine

We studied the effects of gastrointestinal (GI) colonization by Candida albicans, dietary arabinitol, intragastric antibiotics, and cortisone on levels of the Candida metabolite D-arabinitol in rat serum and urine. Rats given conventional laboratory chow, intragastric gentamicin and chloramphenicol, and 6.0 x 10(8) live C. albicans B311 blastoconidia by gavage had minimal invasive GI disease and no more DL-arabinitol in the urine than controls given killed C. albicans. However, colonized and uncolonized rats given intragastric antibiotics had transiently higher urine arabinitol levels than the corresponding controls given saline. Rats given conventional laboratory chow (which contained 50 micrograms of arabinitol per g) had higher serum and urine arabinitol levels than rats given no dietary arabinitol, but the differences were less than expected. Moreover, intragastric antibiotics did not cause increased arabinitol excretion in rats given no dietary arabinitol. Rats given intragastric antibiotics and live C. albicans but no dietary arabinitol had no more arabinitol in their serum or urine than controls given antibiotics and killed C. albicans or saline and live or killed C. albicans. Lastly, cortisone acetate (10 mg/kg of body weight per day intramuscularly for 10 days) did not cause increased serum or urine arabinitol levels. We conclude that neither GI colonization by C. albicans nor cortisone should interfere with the usefulness of arabinitol as a marker for invasive candidiasis; antibiotics appear to increase arabinitol excretion by suppressing GI bacteria capable of consuming dietary arabinitol.

Enantioselective measurement of fungal D-arabinitol in the sera of normal adults and patients with candidiasis

A new method was used to measure D-arabinitol enantioselectively in the sera of 27 healthy adults and four patients with candidiasis. Arabinitol was measured by gas chromatography in serum that was treated with and without the Klebsiella pneumoniae enzyme D-arabinitol dehydrogenase, lactic dehydrogenase, NAD, and sodium pyruvate. Since enzyme treatment removed 98% of 0 to 20 micrograms of D-arabinitol per ml and none of 0 to 20 micrograms of L-arabinitol per ml from spiked sera, D-arabinitol could be determined from the difference in the treated and untreated samples. The concentrations of D- and L-arabinitol in serum from normal subjects were 0.22 +/- 0.052 and 0.16 +/- 0.055 micrograms/ml, respectively, and their D-arabinitol/creatinine and L-arabinitol/creatinine ratios were 0.024 +/- 0.0089 and 0.017 +/- 0.0053 (all means +/- standard deviations). The infected patients all had markedly elevated serum D-arabinitol levels, but their L-arabinitol levels were either normal or proportionately much lower. The excess arabinitol in the sera of individuals with candidiasis is D-arabinitol, and use of enantioselective analytical methods should result in improved ability to diagnose and estimate the severity of candidiasis.

Diagnosis of invasive candidiasis in patients with and without signs of immune deficiency: a comparison of six detection methods in human serum

Visceral candidiasis in 56 patients, 39 of whom were thought to be immune deficient, was investigated using three serological detection methods--whole cell agglutination, haemagglutination, and counterimmunoelectrophoresis for antibodies; two determinations of circulating antigens--haemagglutination inhibition and latex agglutination; and determination of the arabinitol:creatinine ratio. Of the 39 patients with suspected immune deficiency, 13 had confirmed invasive candidiasis and 26 were colonised; of those without signs of immune deficiency, 10 patients also had invasive candidiasis and seven were colonised. Twenty three patients with invasive candidiasis were analysed in total. For suspected immune deficient patients the best discrimination between visceral candidiasis and colonisation was obtained by combining the results of haemagglutination inhibition and arabinitol:creatinine ratio. For patients without signs of immune deficiency the best discrimination between invasive candidiasis and colonisation was achieved with counterimmunoelectrophoresis. The results of the serological tests confirmed the classification on clinical grounds of those with and without immune deficiency.