In vivo activity of cefquinome against Riemerella anatipestifer using the pericarditis model in the duck

Cefquinome is a fourth‐generation cephalosporin with broad‐spectrum antibacterial activity, including activity against enteric gram‐negative bacilli such as Riemerella anatipestifer . The pericarditis model was used to examine the pharmacodynamic characteristics of cefquinome against R. anatipestifer . Serum levels of cefquinome following the administration of different doses were determined by LC ‐ MS / MS . Ducks with ca. 10 6   CFU / mL at the initiation of therapy were treated with cefquinome at doses that ranged from 0.0156 to 2 mg/kg of body weight/day (in 3, 6, 12, or 24 divided doses) for 24 h. The percentage of a 24‐h dosing interval that the unbound serum cefquinome concentrations exceeded the MIC ( f T  >  MIC ) were the pharmacokinetic ( PK )–pharmacodynamic ( PD ) parameter that best correlated with efficacy ( R 2 86.3% for R. anatipestifer , compared with 58.9% for the area under the concentration–time curve/ MIC and 10.6% for peak/ MIC ). A sigmoid E max model was used to estimate the magnitudes of the % f T  >  MIC associated with net bacterial stasis, a 1‐log 10 CFU reduction from baseline, and a 2‐log 10 CFU reduction from baseline; the corresponding values were (22.5 ± 1.3) %, (35.2 ± 4.5) %, and (42.4 ± 2.7) %. These data showed that treatment with cefquinome results in marked antibacterial effects in qvivo against R. anatipestifer and that the host's immunity may also play a key role in the anti‐infective therapy process.