Abstract:

To determine the pathogen causing symptoms such as increased body temperature, salivation, runny nose and dyspnea of beef cattle in a cattle farm, nasal swabs of sick cattle were collected for bacterial isolation and identification and sensitive drug screening. The isolated strain ZZC-JM-1 was identified as Proteus cibarius by determination of swarming motility, biochemical identification and 16S rRNA sequencing. The strain showed swarming motility on the ordinary plate containing 1% and 2% agar, and when the agar concentration reached 3%, the growth was inhibited. Biochemical characteristics were consistent with Proteus cibarius except that maltose and sucrose test showed positive. Similarity between 16S rRNA gene of ZZC-JM-1 and Proteus cibarius reported on Genbank was 99.7%, and ZZC-JM-1 and Proteus cibarius were clustered together by constructing phylogenetic tree.When mice were intraperitoneally injected with 7.35×10 ⁷ CFU·mL^-1 bacterial solution (0.2 mL per mouse), they all died within 7-14 h. Anatomical examination showed hemorrhage and swelling of lung, liver and spleen. Drug sensitivity test showed that ZZC-JM-1 was resistant to common antibiotics, and highly sensitive to ciprofloxacin, levofloxacin and gentamicin. In conclusion, a strain of Proteus cibarius was isolated from diseased cattle with high body temperature and respiratory symptoms, and Proteus cibarius might be the main pathogen or the secondary pathogen of respiratory tract infection in beef cattle, which should be paid highly attention.

Key words: Proteus cibarius, beef cattle, respiratory tract infection, tolerance