RESUMEN
Isavuconazole (ISZ) is a newly available broad-spectrum triazole agent recently approved for the treatment of both invasive aspergillosis and mucormycosis. The aim of this study was to develop a simple and reliable method for therapeutic drug monitoring (TDM) of ISZ in human plasma samples. The method involves using a kit from ChromSystems intended for TDM of itraconazole (ITZ), posaconazole (PSZ), and voriconazole (VRZ) in serum/plasma for sample preparation and high-performance liquid chromatography, using fluorescence detection with emission and excitation wavelengths set to 261 and 366 nm, respectively. The assay was linear over the ISZ concentration range of 0.2 to 20.0 mg/liter, using a 0.1-ml sample volume. The inter- and intraday coefficients of variation were all below 3.7%, whereas the accuracies ranged from 95.0 to 106.2% and the mean extraction recovery was 91.9%. In addition, the method worked well using four different Vacutainer types, with six different healthy volunteers and under a number of relevant storage conditions. Finally, the ISZ detection could be seamlessly implemented in the TDM kit for VRZ, PSZ, and ITZ, enabling simultaneous detection of all four triazoles. This method proved to be simple, accurate, precise, and well suited for routine analysis work. It has been implemented in our laboratory for the simultaneous quantitative analysis of ISZ, VRZ, PSZ, and ITZ for TDM and pharmacokinetic research. IMPORTANCE Isavuconazole is a new broad-spectrum triazole agent recently approved for the treatment of both invasive aspergillosis and mucormycosis. Currently, there is no consensus regarding the potential need for TDM of isavuconazole, and no therapeutic window has been defined. However, at the ECIL-6 meeting in 2015, it was advised that TDM is indicated in a number of different settings. In this study, we describe a rapid and validated isocratic HPLC method for fluorescence-based detection and quantification of isavuconazole in human plasma/serum samples. The method is simple and efficient with good accuracy and precision and importantly only requires a small volume of patient plasma/serum. Furthermore, this method is highly sensitive and selective and can be detected simultaneously with the three other triazoles, itraconazole, voriconazole, and posaconazole, without the need for expensive mass spectrometry equipment.
RESUMEN
The emergence of extensively drug-resistant tuberculosis (XDR-TB) hampers infection control. To assess the performance of an extended rapid novel molecular analysis for the detection of resistance conferring mutations to fluoroquinolones (gyrA, gyrB genes) and aminoglycosides/cyclic peptides (16S rRNA rrs gene, eis promotor region) compared to phenotypic susceptibility and sequencing, 43 multidrug-resistant (MDR) and 10 susceptible clinical isolates were analyzed. Results were compared to a previous version. Molecular rifampin (rpoB gene) and isoniazid (katG gene, inhA promotor region) resistance was also analyzed. XDR-TB was confirmed in 13 (30%) MDR isolates. Molecular resistance was detected in 91% ofloxacin-, 83% aminoglycoside/cyclic peptide- and 100% kanamycin-resistant isolates. In conclusion, the novel assay is a useful supplement to phenotypic susceptibility testing in determining the presence of XDR-TB. Molecular kanamycin resistance detection was immensely improved compared to the previous version. Aminoglycoside/cyclic peptide susceptible isolates revealed eis promotor region resistance in 29%, reflecting low-level kanamycin susceptibility challenges.
