Identification and antimicrobial susceptibility profiles of Nocardia species clinically isolated in Japan.

The aims of the present study were to profile the antimicrobial susceptibility patterns of a diverse range of Nocardia species isolated in Japan, and to determine the ability of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for species/complex identification. Identification of 153 clinical isolates was performed by full-length 16S rRNA gene sequencing as a reference method to evaluate the usefulness of MALDI-TOF MS identification. Antimicrobial susceptibility testing (AST) for 14 antibiotics was performed using the broth microdilution method against 146 of the isolates. Among the total 153 clinical isolates, Nocardia farcinica complex (25%) was the most common species, followed by Nocardia cyriacigeorgica (18%), Nocardia brasiliensis (9%), Nocardia nova (8%), and Nocardia otitidiscaviarum (7%). Among 150 isolates identified to the species/complex level by 16S rRNA gene sequencing, MALDI-TOF MS with the use of a supplemental Nocardia library (JMLD library ver.ML01) correctly identified 97.3% (n = 146) to the species/complex level and 1.3% (n = 2) to the genus level. Among the 146 Nocardia isolates that underwent AST, the susceptibilities were 100% to linezolid, 96% to amikacin, 94% to trimethoprim-sulfamethoxazole, and 76% to imipenem. None of the trimethoprim-sulfamethoxazole-resistant isolates carried either plasmid-mediated sulfonamide-resistant genes (sul1, sul2) or trimethoprim-resistant genes (dfrA).

Validation of MALDI-TOF MS devices in reanalysis of unidentified pathogenic bacteria detected in blood cultures.

In hospital microbial laboratories, morphological and biochemical analyses are performed to identify pathogenic microbes;however, these procedures lack rapidity and accuracy. Recently, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) has been clinically utilized, and is expected to enable rapid and accurate microbial identification. We aimed to validate two MALDI-TOF MS devices available in Japan: the VITEK-MS (BioMérieux) and the Microflex LT (Bruker Daltonics). Clinically isolated bacteria, 100 samples in all, detected in blood cultures but incompletely identified by conventional procedures, were reanalyzed using the two devices. The VITEK-MS and Microflex LT, respectively, identified 49% (49/100) and 80% (80/100) of the tested bacteria at the species level, as well as 96% (96/100) and 95% (95/100) at the genus level. Among those reidentified strains, 26% (26/100) at the species level and 88% (88/100) at the genus level were concordant with each other, though three strains were unmatched. Moreover, four bacterial strains were unable to be identified using the VITEK-MS, versus five using the Microflex LT. MALDI-TOF MS devices can provide more rapid and accurate bacterial identification than ever before;however, the characteristics of each system were slightly different;therefore, it is necessary to understand the difference in performance of MALDI-TOF MS models.

Pharmacokinetics of R- and S-carvedilol in routinely treated Japanese patients with heart failure.

The purpose of this study was to evaluate the pharmacokinetics of R- and S-carvedilol in routinely treated Japanese patients with heart failure. We measured peak and trough blood concentrations at steady state following repeated oral administration to 24 patients. The blood concentration of S-carvedilol with potent beta-blocking activity was lower than that of R-carvedilol. The mean oral clearance (CL/F) of R- and S-carvedilol was not altered by CYP2D6*10, UGT2B7*3, and the etiology of heart failure. In addition, the CL/F values of enantiomers were not correlated with age, creatinine clearance, and plasma concentrations of alpha1-acid glycoprotein and brain natriuretic peptide. On the other hand, the mean CL/F values of R- and S-carvedilol in patients with heart failure were 0.89 and 1.52 l/h/kg, respectively, considerably lower than those estimated previously in healthy subjects. These results suggested that the pharmacokinetics of R- and S-carvedilol was altered significantly by heart failure.

UGT2B7*3 did not affect the pharmacokinetics of R- and S-carvedilol in healthy Japanese.

We previously investigated the pharmacokinetics of R- and S-carvedilol in 54 healthy Japanese subjects, and reported that the oral clearance (CL/F) and apparent volume of distribution (V/F) of both enantiomers in subjects with the CYP2D6*10 allele were significantly lower than those in subjects without the CYP2D6*10 allele. In the present study, we examined the genotype of UGT2B7 in these 54 subjects, and investigated the effect of UGT2B7*3 on the pharmacokinetics of R- and S-carvedilol. Forty-three subjects did not have the UGT2B7*3 allele, and 11 subjects had one UGT2B7*3 allele. CL/F and V/F values of R- and S-carvedilol in the subjects with one UGT2B7*3 allele were similar to those without the UGT2B7*3 allele, indicating that the UGT2B7*3 allele did not significantly affect the systemic clearance (CL) and bioavailability (F) of the two enantiomers.

Stereoselective metabolism of carvedilol by the beta-naphthoflavone-inducible enzyme in human intestinal epithelial Caco-2 cells.

Treatment of Caco-2 cells with beta-naphthoflavone (beta-NF) and 1alpha,25-dihydroxyvitamin D(3) (VD(3)) induces UDP-glucuronosyltransferases (UGTs) and cytochrome P450 (CYP) 3A4, respectively. In the present study, we evaluated the metabolism of carvedilol in beta-NF- and VD(3)-treated Caco-2 cells. The metabolism of R-carvedilol was not significant in non-treated Caco-2 cells, whereas S-carvedilol was significantly metabolized in the cells. The metabolism of R- and S-carvedilol was significantly increased by the treatment of Caco-2 cells with 50 microM beta-NF for 3 d. In contrast, the treatment of Caco-2 cells with 250 nM VD(3) for 2 weeks did not induce a significant change in the metabolism of R- and S-carvedilol. The metabolism of carvedilol in beta-NF-treated Caco-2 cells was markedly inhibited by a substrate of UGTs, baicalein. In addition, the expression of UGT1A1, 1A6, and 1A9 mRNA was increased in beta-NF-treated Caco-2 cells as compared with non-treated cells. These findings indicated that carvedilol was metabolized stereoselectively by the beta-NF-inducible enzyme in Caco-2 cells. The UGT1A subfamily in intestinal epithelial cells may be partly responsible for first-pass (presystemic) metabolism of the drug.

Population pharmacokinetics of higher-dose mizoribine in healthy male volunteers.

The population pharmacokinetic parameters of mizoribine in healthy subjects were estimated using a nonlinear mixed effects model (NONMEM) program. Pharmacokinetic data for population analysis were obtained in the previous study, in which 24 healthy Caucasian male subjects participated in a single-dose (3, 6, 9, 12 mg/kg) study, and 12 subjects participated in a multiple-dose (6, 12 mg/kg/d) study. The mean value of the absorption lag time, absorption rate constant (KA), and apparent distribution volume (V/F) was estimated to be 0.349 h, 0.869 h-1, and 0.834 l/kg, respectively. Oral clearance (CL/F) was modeled with creatinine clearance (CLcr), and the mean value was estimated to be 1.93.CLcr l/h. In addition, pharmacokinetic parameters in individual 36 subjects were obtained from population estimates according to Bayes' theorem. Pharmacokinetic parameters (KA, V/F, and CL/F) in the single-dose study were almost constant at a dose range of 3-12 mg/kg, and were similar to those in the multiple-dose study. These findings indicated that the pharmacokinetics of mizoribine is well described by a simple one-compartment model with first-order absorption.

Multiple regression analysis of pharmacogenetic variability of carvedilol disposition in 54 healthy Japanese volunteers.

The aim of this study was to evaluate the pharmacogenetic variability in the disposition of carvedilol in the Japanese population. Five or 10 mg of carvedilol was orally administered to 54 healthy Japanese subjects (22-44 years old), and blood samples were taken at 2 and 6 h after dosing. We determined the polymorphic alleles of CYP2D6, CYP2C9, CYP2C19, CYP3A5, UGT2B7, and MDR1 in each subject. The whole blood concentration of R- and S-carvedilol was measured by an HPLC method. The pharmacokinetic parameters in individual subjects were estimated by the Bayesian method using the nonlinear mixed effects model (NONMEM) program. We then examined the effect of the genetic polymorphisms on the variability in the pharmacokinetics of carvedilol using a multiple regression analysis. The oral clearance (CL/F) and also apparent volume of distribution (V/F) of both enantiomers were significantly lower in the subjects with the CYP2D6*10 allele than those with the CYP2D6*1/*1, *1/*2, or *2/*2 genotype, confirming our previous finding that the bioavailability (F) and systemic clearance (CL) of R- and S-carvedilol in the liver is significantly altered in Japanese with the CYP2D6*10 allele. On the other hand, CYP2C9*3, CYP2C19*2, CYP2C19*3, CYP3A5*3, UGT2B7*2, and MDR1 C3435T did not significantly affect the pharmacokinetics of carvedilol in Japanese subjects.

Effect of CYP2D6*10 on the pharmacokinetics of R- and S-carvedilol in healthy Japanese volunteers.

This study was performed to investigate the effect of CYP2D6*10 on the pharmacokinetics of R- and S-carvedilol in healthy Japanese volunteers. Five or 10 mg of carvedilol was orally administered to 23 subjects (22-44 years old), and blood samples were taken at 2 and 6 h after dosing. We determined the polymorphic alleles of CYP2D6 in each subject. The whole blood concentration of R- and S-carvedilol was measured by an HPLC method. The pharmacokinetic parameters in individual subjects were estimated by the Bayesian method using the nonlinear mixed effects model (NONMEM) program. The mean values of oral clearance for R- and S-carvedilol were estimated to be 1.01 and 2.15 l/h/kg, respectively. The oral clearance was highly correlated with the apparent volume of distribution among the subjects, suggesting that the interindividual difference in bioavailability was largely responsible for the pharmacokinetic variability of carvedilol. The oral clearance and also volume of distribution of both enantiomers were significantly lower in the subjects with the CYP2D6*10 allele than with the CYP2D6*1/*1 or *1/*2 genotype. These results suggested that the systemic and/or pre-systemic metabolism of R- and S-carvedilol in the liver is significantly decreased in Japanese with the CYP2D6*10 allele.