In vivo Pharmacokinetic/Pharmacodynamic Analysis of the Efficacy of the Cefepime/Nacubactam Combination Against ß-Lactamase-Producing Enterobacterales based on the Instantaneous MIC Concept.

PURPOSE: Nacubactam (NAC) is a novel diazabicyclooctane ß-lactamase inhibitor used in combination with cefepime (CFPM). In this study, we aimed to determine the target pharmacokinetics (PK) and pharmacodynamics (PD) values of CFPM/NAC in mice infected with ß-lactamase-producing Enterobacterales, such as the carbapenemase-producing Enterobacterales. METHODS: Three strains of ß-lactamase-producing Enterobacterales, Klebsiella pneumoniae MSC 21444, Escherichia coli MSC 20662, and K. pneumoniae ATCC BAA-1898, were used for checkerboard assays and fractionation studies and dose-range studies. A PK study was performed in neutropenic mice. Additionally, PK/PD analysis was performed based on the instantaneous minimum inhibitory concentration (MICi) concept. RESULTS: Checkerboard measurements revealed that higher NAC concentrations decreased the CFPM MIC in a concentration-dependent manner. In all tested strains, fT > MICi calculated from the PK experiments showed a high correlation with the mean change in the bacterial count of thigh-infected mice in the in vivo PD study, suggesting that fT > MICi is an optimal PK/PD parameter for monitoring the CFPM/NAC combination. The target fT > MICi values for CFPM/NAC to achieve a bacteriostatic effect, 1-log10-kill, and 2-log10-kill values were 30, 49, and 94%, respectively. CONCLUSIONS: Our results indicate that fT > MICi is a PK/PD parameter is suitable for monitoring the CFPM/NAC combination. The minimum target value for achieving a static effect against ß-lactamase-producing Enterobacterales is 30%.

In vivo Pharmacokinetics/Pharmacodynamics Profiles for Appropriate Doses of Cefditoren pivoxil against S. pneumoniae in Murine Lung-Infection Model.

PURPOSE: Cefditoren, the active form of cefditoren pivoxil, is an oral cephalosporin antimicrobial drug. Although cefditoren exhibits high antimicrobial activity against Streptococcus pneumoniae, its pharmacokinetics/pharmacodynamics (PK/PD) characteristics remain unknown. This study aimed to determine its PK/PD parameter with target values for cefditoren against S. pneumoniae in S. pneumoniae lung-infected mice and to simulate MIC range of S. pneumoniae that can be expected to be treated at approved cefditoren doses in human using population pharmacokinetic (PPK) data from patients. METHODS: Susceptibility testing and time-kill assays against S. pneumoniae ATCC® 49619 were performed for in vitro PD evaluation. Based on the results of a PK study in healthy mice and PD studies in S. pneumoniae lung-infected mice, optimal PK/PD parameters were determined using the correlation curve between the PK/PD parameters and lung bacterial count changes. The target value was calculated to achieve a 2 log10 reduction in the lung bacterial counts. RESULTS: In vitro PD evaluation showed that cefditoren had a potent antimicrobial effect against S. pneumoniae in a time-dependent manner at concentrations above the MIC. In PK/PD analyses, both fAUC24/MIC and fCmax/MIC were well correlated with bactericidal efficacy, achieving 2 log10-kill with fAUC24/MIC ≥ 63 and fCmax/MIC ≥ 16. CONCLUSIONS: Cefditoren pivoxil has good therapeutic efficacy against acute pneumonia caused by S. pneumoniae with a MIC ≤ 0.031-0.063 mg/L at approved doses in adults and children.

Development of an optimized and practical pharmacokinetics/pharmacodynamics analysis method for aztreonam/nacubactam against carbapenemase-producing K. pneumoniae.

BACKGROUND: Nacubactam, a new ß-lactamase inhibitor with antibacterial activity, is being developed as a single drug to be co-administered with cefepime or aztreonam. However, determining pharmacokinetics/pharmacodynamics (PK/PD) parameters in ß-lactam/ß-lactamase inhibitor combinations remains challenging. We aimed to establish a practical PK/PD analysis method for aztreonam/nacubactam that incorporates instantaneous MIC (MICi). METHODS: Based on chequerboard MIC measurements, MICi of aztreonam against carbapenemase-producing Klebsiella pneumoniae in the presence of nacubactam was simulated. RESULTS: The mean change in the bacterial count of thigh-infected mice in an in vivo PD study was plotted based on %fT>MICi and analysed using the inhibitory effect sigmoid Imax model. fT>MICi calculated from the PK experiments showed a high correlation with the in vivo bactericidal effect, suggesting that fT>MICi is the optimal PK/PD parameter for aztreonam/nacubactam. The target values of fT>MICi achieving growth inhibition, 1 log10 kill and 2 log10 kill, were 22, 38% and 75%, respectively. CONCLUSIONS: The PK/PD analysis method proposed in this study is promising for determining practical PK/PD parameters in combination therapy. In addition, this is the first report of aztreonam/nacubactam showing a potent in vivo therapeutic effect against NDM-producing K. pneumoniae.

Therapeutic plasma exchange in postpartum HELLP syndrome: a case report.

BACKGROUND: Postpartum hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome is more difficult to treat than HELLP syndrome during pregnancy. We describe a case of postpartum HELLP syndrome that responded to plasma exchange (PE) therapy. CASE PRESENTATION: A 30-year-old primipara woman was hospitalized for gestational hypertension at 33 weeks of gestation and underwent an emergent cesarean section at 36 weeks and 6 days of gestation due to rapidly progressing pulmonary edema. After delivery, liver dysfunction and a rapid decrease in platelet count were observed, and the patient was diagnosed with severe HELLP syndrome. She experienced multiple organ failure despite intensive care, and PE therapy was initiated. Her general condition dramatically stabilized within a few hours of PE therapy. CONCLUSION: It is controversial whether PE therapy should be used primarily in the management of HELLP syndrome, but early initiation of PE therapy could be effective for severe HELLP syndrome.

Differences in Pharmacokinetic/Pharmacodynamic Parameters of Tedizolid Against VRE and MRSA.

PURPOSE: Vancomycin-resistant enterococci (VRE) have recently become a major cause of nosocomial infections and a global public health concern. Tedizolid exhibits powerful antibacterial activity against VRE in vitro, but its pharmacokinetic/pharmacodynamic (PK/PD) parameters remain unclear. Therefore, we aimed to determine the PK/PD indices of tedizolid action on VRE and the mechanisms underlying the PK/PD indices differences of tedizolid against VRE and methicillin-resistant Staphylococcus aureus (MRSA). METHODS: Optimal PK/PD target values of tedizolid were determined in vitro, based on time-kill curves and post-antibiotic effects (PAEs), and in vivo, using mouse models of thigh infection with VRE and MRSA strains. RESULTS: The tedizolid bactericidal activity on VRE and MRSA was time-dependent. Correlations were closest between fAUC24/MIC and the tedizolid PK/PD index against MRSA and VRE. To achieve 1 log10 kill tedizolid fAUC24/MIC in neutropenic mouse models of thigh infection with VRE and MRSA should be 14.2 and 138.5, respectively. The PAEs of tedizolid against VRE and MRSA were 2.39 and 0.99 h, respectively. CONCLUSION: Tedizolid showed bactericidal effects against VRE even in neutropenic mice unlike MRSA, which could be attributed to its longer PAE against VRE. Hence, we hypothesize that tedizolid treatment against VRE infections is promising for achieving therapeutic success in clinical.

Cefmetazole as an Alternative to Carbapenems Against Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Infections Based on In Vitro and In Vivo Pharmacokinetics/Pharmacodynamics Experiments.

PURPOSE: Cefmetazole (CMZ) has received attention as a pharmaceutical intervention for extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) infections. This study aimed to investigate the pharmacokinetics/pharmacodynamics (PK/PD) characteristics of CMZ against ESBL-EC. METHODS: The susceptibility and time-killing activity of CMZ against clinically isolated ESBL-EC (EC9 and EC19) were determined in vitro. The optimal PK/PD index and its target value were calculated based on the results of a PK study in healthy mice and PD study in neutropenic murine thigh infection model mice. RESULTS: The minimum inhibitory concentrations (MICs) of CMZ against EC9 and EC19 were 2.0 and 1.0 µg/mL, respectively. Time-kill studies showed that colony-forming units decreased in a time-dependent manner at CMZ concentrations in the range of 4-64 × MIC. In in vivo PK/PD studies, the antibacterial effect of CMZ showed the better correlation with the time that the free drug concentration remaining above the MIC (fT>MIC), with the target values for a static effect and 1 log10 kill reduction calculated as 57.6% and 69.6%, respectively. CONCLUSION: CMZ possesses time-dependent bactericidal activities against ESBL-EC and is required to achieve "fT>MIC" ≥ 69.6% for the treatment of ESBL-EC infections.

The optimal trough-guided monitoring of vancomycin in children: Systematic review and meta-analyses.

We carried out a systematic review and meta-analysis exploring the relationship between vancomycin (VCM) trough concentrations and its effectiveness and nephrotoxicity in pediatric patients. We conducted our analysis using MEDLINE, Web of Sciences, and Cochrane Register of Controlled Trials as electronic databases (June 29, 2019). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. We identified 16 studies that were eligible for the meta-analysis. A total of 351 and 3,266 patients were included in the analysis for effectiveness and nephrotoxicity, respectively. Pediatric MRSA infection patients with VCM trough concentrations ≥ 10 µg/mL had significantly lower treatment failure rates (OR 0.54, 95% CI 0.30-0.96). The incidence of nephrotoxicity was significantly higher in trough concentrations ≥ 15 µg/mL than when they were < 15 µg/mL (OR 3.02, 95% CI 2.08-4.38). We identified the optimal VCM trough concentrations associated with effectiveness and nephrotoxicity in pediatric patients with MRSA infection. Further prospective studies are needed to find optimal dosing and monitoring strategy on VCM in pediatric population.

The monitoring of vancomycin: a systematic review and meta-analyses of area under the concentration-time curve-guided dosing and trough-guided dosing.

BACKGROUND: This systematic review and meta-analysis explored the relationship between vancomycin (VCM) monitoring strategies and VCM effectiveness and safety. METHODS: We conducted our analysis using the MEDLINE, Web of Sciences, and Cochrane Register of Controlled Trials electronic databases searched on August 9, 2020. We calculated odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Adult patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia with VCM trough concentrations ≥15 µg/mL had significantly lower treatment failure rates (OR 0.63, 95% CI 0.47-0.85). The incidence of acute kidney injury (AKI) increased with increased trough concentrations and was significantly higher for trough concentrations ≥20 µg/mL compared to those at 15-20 µg/mL (OR 2.39, 95% CI 1.78-3.20). Analysis of the target area under the curve/minimum inhibitory concentration ratios (AUC/MIC) showed significantly lower treatment failure rates for high AUC/MIC (cut-off 400 ± 15%) (OR 0.28, 95% CI 0.18-0.45). The safety analysis revealed that high AUC value (cut-off 600 ± 15%) significantly increased the risk of AKI (OR 2.10, 95% CI 1.13-3.89). Our meta-analysis of differences in monitoring strategies included four studies. The incidence of AKI tended to be lower in AUC-guided monitoring than in trough-guided monitoring (OR 0.54, 95% CI 0.28-1.01); however, it was not significant in the analysis of mortality. CONCLUSIONS: We identified VCM trough concentrations and AUC values that correlated with effectiveness and safety. Furthermore, compared to trough-guided monitoring, AUC-guided monitoring showed potential for decreasing nephrotoxicity.

Pharmacokinetics/Pharmacodynamics Evaluation of Flomoxef against Extended-Spectrum Beta-Lactamase-Producing Escherichia coli In Vitro and In Vivo in a Murine Thigh Infection Model.

PURPOSE: Although flomoxef (FMOX) has attracted substantial attention as an antibiotic against extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-producing E. coli), the pharmacokinetics/pharmacodynamics (PK/PD) characteristics of FMOX against ESBL-producing E. coli is unclear. The aim of this study was to determine the PK/PD index of FMOX against ESBL-producing E. coli. METHODS: In vitro time-kill curve studies and in vivo PK/PD experiments were carried out. RESULTS: Time-kill curves exhibited a unique bactericidal activity: time-dependent activity at low concentrations and concentration-dependent activity at high concentrations. In neutropenic murine thigh infection experiments, the antibacterial activity of FMOX correlated with the time that the free drug concentration remaining above the minimum inhibitory concentration (MIC) (fT>MIC) and the ratio of the area under the free drug concentration-time curve for a 24 h period to the MIC (fAUC24/MIC). However, the burden of ESBL producing E. coli significantly reduced when the time intervals for administration were shorter among three dosage regimens with same magnitude of fAUC24/MIC, indicating that fT>MIC is significant PK/PD index. The target value of fT>MIC for 1 log10 kill reduction was 35.1%. CONCLUSIONS: fT>MIC is the most significant PK/PD index of FMOX against ESBL-producing E. coli and its target value is ≥ 40%.