Estimation of latamoxef (moxalactam) dosage regimens against ß-lactamase-producing Enterobacterales in dogs: a pharmacokinetic and pharmacodynamic analysis using Monte Carlo simulation.

One of the most significant research areas in veterinary medicine is the search for carbapenem substitutes for the treatment of extended-spectrum ß-lactamase (ESBL)-producing Enterobacterales (ESBL-E). This study applied a pharmacokinetic/pharmacodynamic (PK/PD) strategy in validating optimal latamoxef (LMX) therapeutic regimens against canine ESBL-E infections. Five dogs were administered a bolus dose of 40 mg/kg LMX intravenously to measure serum drug concentrations and determine PK indices using the noncompartmental model. The highest minimum inhibitory concentration (MIC) with a probability of target attainment ≥90% was used to compute the PK/PD cutoff values for bacteriostatic (time for which the unbound drug concentration was above the MIC [fTAM] ≥40%) and bactericidal (fTAM ≥70%) effects when administered at 20, 30, 50, and 60 mg/kg, in addition to 40 mg/kg. The cumulative fraction of response (CFR) was determined using the MIC distribution of wild-type ESBL-E in companion animals. The PK/PD cutoff values can be increased by reducing the dosing interval rather than increasing the dose per time. Based on the calculated CFRs for ESBL-producing Escherichia coli and Klebsiella pneumoniae, all LMX regimens in this study and those administered at 30-60 mg/kg every 8 and 6 hr were found to be optimal (CFR ≥90%) for exerting bacteriostatic and bactericidal effects, respectively. However, the regimens of 50 and 60 mg/kg every 6 hr may merely exert bacteriostatic effects on ESBL-producing Enterobacter cloacae. Further clinical trials are required to confirm the clinical efficacy of LMX.

Pharmacokinetic and Pharmacodynamic Analysis of the Oxacephem Antibiotic Flomoxef against Extended-Spectrum ß-Lactamase-Producing Enterobacterales from Dogs.

Flomoxef (FMX) may be a potential alternative to carbapenems for dogs infected with Enterobacterales-producing extended-spectrum ß-lactamase (ESBL-E). However, the appropriate dosage of FMX in dogs with ESBL-E infections has yet to be established. This study was carried out to establish appropriate treatment regimens for FMX against ESBL-E infections in dogs using a pharmacokinetics-pharmacodynamics (PK-PD) approach. Five dogs were intravenously administered at a bolus dose of FMX (40 mg/kg body weight). Serum concentrations of FMX were calculated with high-performance liquid chromatography-tandem mass spectrometry, and then applied to determine PK indices based on a non-compartmental model. The cumulative fraction of response (CFR) was estimated based on the dissemination of minimum inhibitory concentrations among wild-type ESBL-E from companion animals. From the results, the dosage regimens of 40 mg/kg every 6 and 8 h were estimated to attain a CFR of >90% for wild-type isolates of ESBL-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis for dogs. By contrast, all regimens had a CFR of <80% for ESBL-producing Enterobacter cloacae. Our results indicated that dosage regimens of 40 mg/kg FMX every 6 and 8 h can be a non-carbapenem treatment for canine infections of ESBL-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, but not for those of ESBL-producing Enterobacter cloacae.

Pharmacokinetic-pharmacodynamic analysis of cefmetazole against extended-spectrum ß-lactamase-producing Enterobacteriaceae in dogs using Monte Carlo Simulation.

Introduction: The spread of extended-spectrum ß-lactamase-producing Enterobacteriaceae (ESBL-E) is a serious concern in companion animal medicine owing to their ability to develop multidrug resistance. Cefmetazole (CMZ) is a candidate drug for treating ESBL-E infections; however, its regimen in dogs has not been established. In this study, we investigated the pharmacokinetic (PK) indices of CMZ in dogs and performed PK-pharmacodynamic (PD) analyses using Monte Carlo Simulation (MCS). Methods: In total, six healthy dogs received an intravenous bolus dose of CMZ (40 mg/kg body weight). Serum CMZ concentrations were evaluated using liquid chromatography-mass spectrometry, and PK indices were determined based on non-compartmental analysis. The PK-PD cut-off (COPD) values were calculated as the highest minimum inhibitory concentration (MIC) that achieved ≥90% probability of target attainment for a target value of unbounded drug concentration exceeding 40% of the dosing interval. The cumulative fraction of response (CFR) was calculated based on the MIC distribution of wild-type ESBL-E from companion animals. Results: The area under the concentration-time curve and elimination half-time were 103.36 ± 7.49 mg·h/L and 0.84 ± 0.07 h, respectively. MCS analysis revealed that COPD values for regimens of 40 mg/kg q12, q8h, and q6h were ≤ 0.5, ≤2, and ≤ 4 µg/mL, respectively. A regimen of 40 mg/kg q6h was estimated to achieve a CFR of 80-90% for Escherichia coli and Klebsiella pneumoniae. By contrast, all regimens exhibited a CFR of ≤70% for Proteus mirabilis and Enterobacter cloacae. Discussion: We conclude that CMZ at 40 mg/kg q6h could be a viable treatment regimen for dogs infected with ESBL-producing Escherichia coli and Klebsiella pneumoniae.

In vitro efficacy of cephamycins against multiple extended-spectrum ß-lactamase-producing Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter cloacae isolates from dogs and cats.

The susceptibility of 218 extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae isolates from companion animals to three cephamycins (cefmetazole, flomoxef, and latamoxef) was investigated. Phenotypic testing found 8 of 120 Klebsiella pneumoniae (KP) and 15 of 69 Enterobacter cloacae (EC) isolates were ESBL and AmpC ß-lactamase (ABL) co-producers. Isolates of KP, Proteus mirabilis, and EC that only produced ESBL exhibited susceptibility rates to cefmetazole (95.5%, 82.7%, and 9.3%), flomoxef (99.1%, 96.6%, and 74.0%), and latamoxef (99.1%, 100%, and 100%), respectively. Notably, isolates of KP and EC co-producing ESBL and ABL had significantly lower susceptibility rates to the studied drugs when compared with only ESBL producers. This implies that the in vitro activity of cephamycins against ESBL-producing bacteria can differ depending on ABL production and bacterial species.