Abstract: A gram negative bacilli was isolated from fattening pigs of a pig farm with pneumonia in Hubei province. After pathogen isolation, gram staining, PCR identification and biochemical identification, it was identified as Mannheimia haemolytica. The bacterium was gram-negative short bacilli with two poles stained. The results of sequence comparison showed that the homology rate of the gene sequence of the strain was more than 99.7%, and its biochemical characteristics accorded with the biochemical characteristics of the strain. The strain 2×10⁸ CFU/mL can kill mice and has strong pathogenicity. The results of drug sensitivity test showed that the strain was sensitive to ampicillin, cefotaxime and ciprofloxacin.

Key words: pig, Mannheimia haemolytica, isolation, identification