Minimal inhibitory concentrations(MICs) of florfenicol and chloramphenicol were determined for(Pasteurella) multocida by the method of broth two-fold dilution in vitro.Therapeutic trials on chickens infected with experimentally Pasteurella multocida were carried out with florfenicol at the dosage of 20,40,80mg/kg and chloramphenicolat 40 mg/kg by oral or intramuscular administration twice daily for 3 successive days.The inhibition tests in vitro showed that MIC of florfenicol and chloramphenicol was 0.5 and 1.0 μg/mL for Pasteurella multo-(cida,) respectively.After the oral treatment with florfenicol(20,40,80 mg/kg) and chloramphenicol(40 mg/kg) for 3 days,the curative rates of the drugs against Pasteurella multocida infection in chickens were 93.3%,100%,100% and 70%,respectively.After the intramuscular treatment with florfenicol(20,40,80 mg/kg) and chloramphenicol(40 mg/kg) for 3 days,the curative rates of the drugs against Pasteurella multocida infection in chickens were 86.7%,100%,100% and 83.3%,respectively.The mortality of the infected and untreated group was(90.0%.)
