In vitro pharmacokinetics/pharmacodynamics evaluation of marbofloxacin against Staphylococcus pseudintermedius

This study aimed at determining the in vitro antibacterial activity of a clinically achievable marbofloxacin (MAR) concentration against the clinical isolate S. pseudintermedius in an in vitro dynamic model simulating the in vivo pharmacokinetics of dogs. The in vitro PK/PD (pharmacokinetic/pharmacodynamic) model that mimics the single daily doses of MAR (half-life, 8 h) was simulated. An inoculum (10⁸ cfu/ml) of clinical isolate S. pseudintermedius (MIC = 0.0625 μg/ml) was exposed to monoexponentially decreasing concentrations of MAR with simulated AUC_{24 h}/MIC varied from 34.81 h to 696.15 h. Every two hours, the multiple sample colony forming units were determined. The result of this study demonstrated that the clinically achieved MAR concentrations at AUC_{24 h}/MIC ratios of 348.08 and 696.15 h produced a pronounced reduction in the bacterial counts and prevented the re-growth of the clinical isolate S. pseudintermedius. However, further study, considering the strains with different susceptibility levels, is recommended.