In Vivo Pharmacokinetics And Pharmacodynamics Integration Against Pasteurella Multocida In Mice Pneumonia Model

This study was conducted to evaluate the penetration of marbofloxacin into lung tissue by comparing the pharmacokinetics characteristics of marbofloxacin in plasma, lung tissue and epithelial lining fluid?ELF? in a murine lung infection model. The in vivo activities of marbofloxacin against P.multocida were determined with different single dosage regimes to infected mice. The in vivo PK/PD model of marbofloxacin against P.multocida was established by the integration of the plasma pharmacokinetics and the pharmacodynamics, and the change of antimicrobial susceptibility after the therapy was monitored. It is proposed that this study can be used to provide experimental data for reevaluating dosage regimen in the treatment of respiratory disease. The contents of this study were listed as follows:The minimum inhibitory concentrations?MICs? of marbofloxacin were determined by a broth micro dilution assay against three P.multocidas according to CLSI?VET-A04?. The MICs of marbofloxacin against P.multocida CVCC434, CVCC411, CVCC1669 were 0.125, 0.03125, 0.0625 ?g/ml, respectively. The mutant prevention concentrations?MPCs? of marbofloxacin were determined by agar method. The MPCs of marbofloxacin against P. multocida CVCC434, CVCC411 CVCC1669 were 0.5, 0.2, 0.3 ?g/ml, respectively.The neutropenic mice and immunity normal mice were infected with 50?L of a P. multocida suspension containing about 5×108 CFU/m L using endotracheal intubation respectively. The mice were sacrificed 12 and 24 hours after the inoculation and the amount of bacteria in the lungs were counted. The results showed that the growth of P.multocida in the mice lung exhibited obviously individual difference and self-eradication, suggesting that the mice in presence of neutrophil could not be used to build steady lung infection model. 12 hours after the inoculation which was the time of start of the therapy, the neutropenic mice were lethargic, dyspnea and the bacterial population reached to about 107 CFU/lung. Most of mice were dead after 24 h after inoculation, and the bacterial population increased to 109 CFU/lung. Thus the neutropenic mice were used for the establishment of the lung infection model.Marbofloxacin was administrated subcutaneously to the neutropenic infected mice at dosage of 2.5, 5, 10 and 20 mg/kg at 12 h after infection. Blood, lung tissue and bronchoalveolar lavage fluid?BLAF? samples were obtained at the following time points: 0.083, 0.25, 0.5, 1, 2, 4, 6, 8, 12, 24 h after dosing. Marbofloxacin concentrations in plasma, lung tissue, BLAF were analyzed by high performance liquid chromatography?HPLC?. The ratios of urea of plasma to that of BLAF were analyzed by the BUN Assay, and then calculating the marbofloxacin concentrations in ELF by the equation of CELF=CBAL × Ureaserum/UreaBA. The concentration-time data of marbofloxacin were analyzed by the noncompartment model of Win Nonlin5.2.1 software. The results showed that the marbofloxacin concentration in lung tissue was 2³ fold to that in plasma, the concentration in ELF was slightly higher than that in plasma and the value of AUCELF/f AUCplasma was about 2. The kinetics of marbofloxacin in the plasma of infected mice were linearity.The infected mice with three P.multocidas strains were treated for 24 hours with different single dosages of marbofloxacin at 12 h after infection. Combined with plasma pharmacokinetics and the MICs value of marbofloxacin, an Effect E_max model was used to estimate the magnitudes of the f AUC24 h /MIC associated with antibacterial effect. The results showed that the values of f AUC24 h /MIC required to produce static effect, 2-log kill, and 3-log kill were 15.8 h, 70 h, 153 h respectively.