Candida krusei renal cyst infection and measurement of amphotericin B levels in cystic fluid in a patient receiving AmBisome.

Candida krusei is an opportunistic pathogen commonly implicated in urinary tract infections in immunocompromised patients. We present the first case of C. krusei renal cyst infection, occurring in a post-liver and kidney transplant patient with autosomal dominant polycystic kidney disease. Her persistent candiduria and fevers were refractory to prolonged therapy with AmBisome (Fujisawa Pharmaceuticals Co. Ltd., Osaka, Japan). She eventually required bilateral nephrectomies of her native kidneys. Cystic fluid was aspirated from six hemorrhagic and six nonhemorrhagic cysts. Cystic fluid cultures yielded C. krusei. Fluid from the nonhemorrhagic cysts was also analyzed for amphotericin B levels, measured using a bioassay. Free amphotericin B levels in the cysts were lower than the minimal inhibitory concentration for amphotericin B for this organism. We provide the first description of amphotericin B levels in cystic fluid obtained during bilateral nephrectomies.

Comparison of high-performance liquid chromatographic and microbiological methods for determination of voriconazole levels in plasma.

A new selective high-performance liquid chromatography (HPLC) method with UV detection for the determination of the investigational triazole voriconazole in human plasma by using acetonitrile precipitation followed by reverse-phase HPLC on a C(18) column was compared with a simple agar well diffusion bioassay method with Candida kefyr ATCC 46764 as the assay organism. Pooled plasma was used to prepare standard and control samples for both methods. The results of analyses with spiked serum samples (run as unknowns) were concordant by the bioassay and HPLC methods, with expected values being obtained. HPLC demonstrated an improved precision (3.47 versus 12.12%) and accuracy (0.81 versus 1.28%) compared to those of the bioassay method. The range of linearity obtained by both methods (from 0.2 to 10 microg/ml for HPLC and from 0.25 to 20 microg/ml for the bioassay) includes the range of concentrations of voriconazole (from 1.2 to 4.7 microg/ml) which are considered clinically relevant. Although either methodology could be used for the monitoring of patient therapy, the smaller variability observed with HPLC compared to that observed with the bioassay favors the use of HPLC for pharmacokinetic studies.

Amphotericin B enzyme-linked immunoassay for clinical use: comparison with bioassay and HPLC.

OBJECTIVE: To evaluate a new enzyme-linked immunosorbent assay (ELISA) for amphotericin B in serum samples. Results are compared with those obtained by HPLC and bioassay. DESIGN: Comparison of results obtained by ELISA, HPLC, and bioassay. METHODS: We developed a new ELISA using a polyclonal rabbit antibody to measure serum amphotericin B concentrations. Blinded samples of amphotericin B in concentrations of 0.15-78 micrograms/mL were prepared in human serum and assayed simultaneously by the ELISA, HPLC, and bioassay. The results of each assay were derived from standard curves and evaluated by using the Table Curve 2D computer program. These data were compared by using correlation analysis with evaluation of Pearson's correlation coefficient by Student's t-test. RESULTS: ELISA and bioassay compared favorably at amphotericin B concentrations of 0.3-20 micrograms/mL with a correlation coefficient of r = 0.993, while ELISA and HPLC compared with a correlation coefficient of r = 0.944. The average coefficient of variation over the range 0.3-20.0 micrograms/mL was 28% +/- 7% for HPLC, 26% +/- 9% for ELISA, and 13% +/- 4% for bioassay. Comparison of all three assays revealed the highest correlation with the ELISA assay (r = 0.998) for the range of concentrations (0.3-20 micrograms/mL) routinely achieved. Samples containing concentrations in excess of 20 micrograms/mL could be diluted. Desiccation for concentrations less than 0.3 microgram/mL was not tested. CONCLUSION: The determination of serum amphotericin B concentrations by ELISA gave results similar to those obtained by a bioassay and HPLC technique. Although variability appears greater with ELISA, the ease of performing yjis assay expedites the evaluation of amphotericin B concentrations from lipid formulations without interference from coadministered antibacterials of azole antifungals.