Abstract: [Objective] To observe the in vivo antibacterial effects of florfenicol against Pasteurella multocida, and to assess its preventive and therapeutic effects on artificial infection of mice with Pasteurella multocida. [Method]Broth micro-dilution method was used to determine the antibacterial effects of 9 commonly used antimicrobial agents in veterinary clinic against Pasteurella multocida to screen the sensitive drugs. Furthermore, an in vivo study in mice was conducted to evaluate the preventive and therapeutic effects of the screened sensitive drug on artificial infection of mice with Pasteurella multocida. [Result]Among the tested antimicrobial agents, the best antibacterial effects against Pasteurella multocida were observed in florfenicol and doxycycline with MIC of 1 μg/mL and MBC of 2 μg/mL, and tiamulin fumarate showed the weakest antibacterial effects with MIC of 64 μg/mL and MBC of 128 μg/mL. Based on the results of in vivo antibacterial effects evaluation, florfenicol was chosen to perform the in vivo study. A negative control group （normal saline）, a positive control group （challenged with Pasteurella multocida） and a florfenicol administration group （challenged with Pasteurella multocida + florfenicol） were included in preventive or therapeutic experiment. The protection rates of therapeutic and preventive experiments were 78.6% and 84.6%, respectively. [Conclusion]Florfenicol has good preventive and therapeutic effects on artificial infection of mice with Pasteurella multocida.

Key words: Pasteurella multocida, florfenicol, preventive and therapeutic effects