Pharmacokinetics and Pharmacodynamics Evaluation of Amoxicillin Against Staphylococcus pseudintermedius in Dogs

Antibiotic resistance in bacteria from companion animals poses significant public health risks. Prudent antibiotic use, particularly through pharmacokinetics/pharmacodynamics modeling, is crucial for minimizing resistance. We investigated the pharmacokinetics/pharmacodynamics of amoxicillin (AMX) against Staphylococcus pseudintermedius. A pharmacokinetic study was conducted on healthy dogs subcutaneously injected with a dose of 15 mg/kg AMX. The antibacterial efficacy of AMX was evaluated against a standard strain from animals (KCTC 3344) and clinical isolates from dogs (B-2, B-7, and B-8), with minimum inhibitory concentrations (MICs) of 0.25, 0.5, 64, and 16 μg/mL, respectively. The half-life of AMX was 7 h, allowing for extended drug efficacy. The time above MIC (%T > MIC) values indicated that the AMX concentrations were maintained above MICs of the two susceptible strains (KCTC 3344 and B-2) for more than 80% of the time when dosed at a one-day interval, suggesting an effective treatment. The area under the curve over 24 h/MIC ratios confirmed the bacteriostatic, bactericidal, and bacterial eradication effects of AMX against S. pseudintermedius strains, except for B-7 (the most resistant strain). These results support improved clinical dosing strategies for AMX against S. pseudintermedius infections in dogs.