Ampicillin pharmacokinetics in azotemic and healthy dogs

Resistance mechanism of Escherichia coli strains with different ampicillin resistance levels

Antibiotic resistance is an important problem that threatens medical treatment. Differences in the resistance levels of microorganisms cause great difficulties in understanding the mechanisms of antibiotic resistance. Therefore, the molecular reasons underlying the differences in the level of antibiotic resistance need to be clarified. For this purpose, genomic and transcriptomic analyses were performed on three Escherichia coli strains with varying degrees of adaptive resistance to ampicillin. Whole-genome sequencing of strains with different levels of resistance detected five mutations in strains with 10-fold resistance and two additional mutations in strains with 95-fold resistance. Overall, three of the seven mutations occurred as a single base change, while the other four occurred as insertions or deletions. While it was thought that 10-fold resistance was achieved by the effect of mutations in the ftsI, marAR, and rpoC genes, it was found that 95-fold resistance was achieved by the synergistic effect of five mutations and the ampC mutation. In addition, when the general transcriptomic profiles were examined, it was found that similar transcriptomic responses were elicited in strains with different levels of resistance. This study will improve our view of resistance mechanisms in bacteria with different levels of resistance and provide the basis for our understanding of the molecular mechanism of antibiotic resistance in ampicillin-resistant E. coli strains. KEY POINTS: •The mutation of the ampC promoter may act synergistically with other mutations and lead to higher resistance. •Similar transcriptomic responses to ampicillin are induced in strains with different levels of resistance. •Low antibiotic concentrations are the steps that allow rapid achievement of high antibiotic resistance.

Updated ACVIM consensus statement on leptospirosis in dogs

Since publication of the last consensus statement on leptospirosis in dogs, there has been revision of leptospiral taxonomy and advancements in typing methods, widespread use of new diagnostic tests and vaccines, and improved understanding of the epidemiology and pathophysiology of the disease. Leptospirosis continues to be prevalent in dogs, including in small breed dogs from urban areas, puppies as young as 11 weeks of age, geriatric dogs, dogs in rural areas, and dogs that have been inadequately vaccinated for leptospirosis (including dogs vaccinated with 2-serovar Leptospira vaccines in some regions). In 2021, the American College of Veterinary Internal Medicine (ACVIM) Board of Regents voted to approve the topic for a revised Consensus Statement. After identification of core panelists, a multidisciplinary group of 6 experts from the fields of veterinary medicine, human medicine, and public health was assembled to vote on the recommendations using the Delphi method. A draft was presented at the 2023 ACVIM Forum, and a written draft posted on the ACVIM website for comment by the membership before submission to the editors of the Journal of Veterinary Internal Medicine. This revised document provides guidance for veterinary practitioners on disease in dogs as well as cats. The level of agreement among the 12 voting members (including core panelists) is provided in association with each recommendation. A denominator lower than 12 reflects abstention of ≥1 panelists either because they considered the recommendation to be outside their scope of expertise or because there was a perceived conflict of interest.

Population pharmacokinetic analysis of enrofloxacin and its active metabolite ciprofloxacin after intravenous injection to cats with reduced kidney function

BACKGROUND

It is unknown if enrofloxacin accumulates in plasma of cats with reduced kidney function.

HYPOTHESIS

To determine if enrofloxacin and its active metabolite ciprofloxacin have reduced clearance in azotemic cats.

ANIMALS

Thirty-four cats hospitalized for clinical illness with variable degree of kidney function.

METHODS

Prospective study. After enrofloxacin (dose 5 mg/kg) administration to cats, sparse blood sampling was used to obtain 2 compartment population pharmacokinetic results using nonlinear mixed-effects modeling. Plasma enrofloxacin and ciprofloxacin concentrations were measured and summed to obtain the total fluoroquinolone concentration. A model of ciprofloxacin metabolism from enrofloxacin was created and evaluated for covariate effects on clearance, volume of distribution, and the metabolic rate of ciprofloxacin generation from enrofloxacin.

RESULTS

Body weight was the only covariate found to affect total fluoroquinolone volume of distribution (effect 1.63, SE 0.19, P < .01) and clearance (effect 1.63, SE 0.27, P < .01). Kidney function did not have a significant effect on total fluoroquinolone clearance (median 440.8 mL/kg/h (range 191.4-538.0 mL/kg/h) in cats with normal kidney function, 365.8 mL/kg/h (range 89.49-1092.0 mL/kg/h) in cats with moderate kidney dysfunction, and 308.5 mL/kg/h (range 140.20-480.0 mL/kg/h) in cats with severe kidney dysfunction (P = .64). Blood urea nitrogen concentration influenced the metabolic generation of ciprofloxacin from enrofloxacin (effect 0.51, SE 0.08, P < .01), but other markers of kidney function did not.

CONCLUSIONS AND CLINICAL IMPORTANCE

Adjustment of enrofloxacin dosage is not indicated for azotemic cats.

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

Introduction

The spread of extended-spectrum β-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.

Comparison of the pharmacokinetics of continuous and intermittent infusions of ampicillin-sulbactam in dogs with septic peritonitis

OBJECTIVE

To evaluate the time-course of ampicillin-sulbactam and percentage of time that its concentration is above a given MIC (T% > MIC) in dogs with septic peritonitis when delivered as either a continuous infusion (CI) or intermittent infusion (II).

ANIMALS

11 dogs with septic peritonitis.

PROCEDURES

Dogs were randomized to receive ampicillin-sulbactam as either CI or II. Continuous infusions were delivered as a 50 mg/kg bolus IV followed by a rate of 0.1 mg/kg/min. Intermittent infusions were administered as 50 mg/kg IV q8h. Serum ampicillin-sulbactam concentrations were measured at hours 0, 1, 6, and every 12 hours after until patients were transitioned to an oral antimicrobial equivalent. All other care was at the discretion of the attending clinician. Statistical analysis was used to determine each patient's percentage of time T% > MIC for 4 MIC breakpoints (0.25, 1.25, 8, and 16 µg/mL).

RESULTS

No dogs experienced adverse events related to ampicillin-sulbactam administration. Both CI and II maintained a T% > MIC of 100% of MIC 0.25 µg/mL and MIC 1.25 µg/mL. The CI group maintained a higher T% > MIC for MIC 8 µg/mL and MIC 16 µg/mL; however, these differences did not reach statistical significance (P = .15 and P = .12, respectively).

CLINICAL RELEVANCE

This study could not demonstrate that ampicillin-sulbactam CI maintains a greater T% > MIC in dogs with septic peritonitis than II; however, marginal differences were noted at higher antimicrobial breakpoints. While these data support the use of antimicrobial CI in septic and critically ill patients, additional prospective trials are needed to fully define the optimal doses and the associated clinical responses.

Drug-Dosing Adjustment in Dogs and Cats with Chronic Kidney Disease

Chronic kidney disease is a common kidney disorder in adult and aged dogs and cats; the management of associated complications and comorbidities generally requires a life-long medical treatment to ensure a good quality of life of affected patients. However, indications and the literature on drug dosing in dogs and cats with chronic kidney disease are often lacking. The aim of this review is to revise the current literature on drug dosing in canine and feline patients with renal impairment, with a special focus on the most commonly used medications to manage chronic kidney disease and possible comorbidities.

Population Pharmacokinetics of Intravenous Amoxicillin Combined With Clavulanic Acid in Healthy and Critically Ill Dogs

Background: Data regarding antimicrobial pharmacokinetics (PK) in critically ill dogs are lacking and likely differ from those of healthy dogs. The aim of this work is to describe a population PK model for intravenous (IV) amoxicillin–clavulanic acid (AMC) in both healthy and sick dogs and to simulate a range of clinical dosing scenarios to compute PK/PD cutoffs for both populations.

Methods: This study used a prospective clinical trial in normal and critically ill dogs. Twelve client-owned dogs hospitalized in the intensive care unit (ICU) received IV AMC 20 mg/kg every 8 h (0.5-h infusion) during at least 48 h. Eight blood samples were collected at predetermined times, including four trough samples before the next administration. Clinical covariates and outcome were recorded, including survival to discharge and bacteriologic clinical failure. Satellite PK data were obtained de novo from a group of 12 healthy research dogs that were dosed with a single AMC 20 mg/kg IV. Non-linear mixed-effects model was used to estimate the PK parameters (and the effect of health upon them) together with variability within and between subjects. Monte Carlo simulations were performed with seven dosage regimens (standard and increased doses). The correlation between model-derived drug exposure and clinical covariates was tested with Spearman's non-parametric correlation analysis. Outcome was recorded including survival to discharge and bacteriologic clinical failure.

Results: A total of 218 amoxicillin concentrations in plasma were available for healthy and sick dogs. A tricompartmental model best described the data. Amoxicillin clearance was reduced by 56% in sick dogs (0.147 L/kg/h) compared with healthy dogs (0.336 L/kg/h); intercompartmental clearance was also decreased (p <0.01). None of the clinical data covariates were significantly correlated with individual exposure. Monte Carlo simulations showed that higher PK/PD cutoff values of 8 mg/L could be reached in sick dogs by extending the infusion to 3 h or doubling the dose.

Conclusions: The PK of AMC is profoundly different in critically ill dogs compared with normal dogs, with much higher interindividual variability and a lower systemic clearance. Our study allows to generate hypotheses with regard to higher AMC exposure in clinical dogs and provides supporting data to revise current AMC clinical breakpoint for IV administration.

Ampicillin pharmacokinetics in azotemic and healthy dogs

BACKGROUND

Little is known about effects of factors such as kidney disease, affecting ampicillin pharmacokinetics in dogs.

OBJECTIVES

Determine the pharmacokinetics of ampicillin after a single intravenous dose in healthy and azotemic dogs.

ANIMALS

Nine dogs presenting with acute kidney injury and 10 healthy dogs.

METHODS

This was a prospective study. An ampicillin dose of 22.2 mg/kg (mean dose) was administered once intravenously. Blood samples were obtained at timed intervals (just before administration, 1, 2, 4, 12, and 24 hours), analyzed using high-pressure liquid chromatography followed by pharmacokinetic analysis of the plasma drug concentrations.

RESULTS

Peak ampicillin concentration (mcg/mL; 97.07 (36.1) vs 21.3 (50.26)), P<.001 (geometric mean (coefficient of variation, CV%)), half-life (hours; 5.86 (56.55) vs 0.97 (115.3)), P<.001) and AUC (h × mcg/mL; 731.04 (83.75) vs 33.57 (53.68)), P<.001) were greater in azotemic dogs than in healthy dogs. Azotemic dogs also had significantly lower clearance (30.06 (84.19) vs 655.03 (53.67); mL/kg h, P < .001) and volume of distribution (253.95 (30.14) vs 916.93 (135.24); mL/kg, P <.001) compared to healthy dogs.

CONCLUSION AND CLINICAL IMPORTANCE

Increased drug concentrations and slower clearance of ampicillin in azotemic dogs could have clinical importance in contributing to antibiotic associated morbidity requiring indicating the need to adjust ampicillin dosing in dogs with decreased kidney function.