In Vitro Pharmacodynamics And Pharmacokinetics Research Of Florfenicol Against Riemerella Anatipestifer In Ducks

Riemrella anatipestifer(Ra)is the causative agent of infectious serositis of duck,which has an important economic impact on the poultry industry.Florfenicol belongs to chloramphenicol class and is solely used in animal.It shows broad-spectrum antibacterial activity including activity against gram-negative bacteria such as Riemerella anatipestifer and gram-positive bacteria.It also possesses excellent pharmacokinetic properties.However,with the rapid development of intensive poultry industry,the florfenicol residues occur more and more frequently and florfenicol-resistant bacteria increased significantly.Thus,an in vitro pharmacodynamics and in vivo pharmacokinetic research of florfenicol against Ra was studied in order to optimize the efficacy of florfenicol and decrease the emergence of florfenicol-resistant bacteria.The MIC and MBC of florfenicol against Ra r-3 in artificial media was 0.5 ?g/mL and 1?g/mL and the MPC was 1.6 ?g/mL;while the value of MIC and MBC in serum was 1 and 4?g/mL.This results emphasized the impact of matrix on MIC determination.The time killing curve showed that with the increasing of drug concentration,the antibacterial effect enhanced.The experimentally infected model was established with 0.5 mL 108cfu/mL Ra r-3.The clinical and anatomical symptom was obvious;and bacteria loading was stable.The mortality rate was 20%.The PKs of florfenicol in infected ducks after oral administration at dose of 10,30,60 mg/kg body weight(B.W.)were evaluated with high-performance liquid chromatography(HPLC)method.The Tmax and T1/2? of florfenicol at the three doses were similar with values of 0.54±0.23 h,0.44±0.11 h and 0.40±0.13 h,;1.72±0.44 h,1.41±0.12 h,1.28±0.16 h respectively.Florfenicol absorbed quickly and eliminated fast in infected ducks.The peak concentration(Cmax),and the area under the concentrations-time curve from 0 to 24 h(AUC0-24)of florfenicol increased in a dose-dependent manner during the dose range of 10 to 60 mg/kg.