一株牛源致病性卡氏变形杆菌的分离鉴定与敏感药物筛选

为确定引起某养殖场肉牛体温升高、流涎、流鼻液、呼吸困难等症状疾病的病原菌,采集病牛鼻腔拭子进行细菌分离鉴定和敏感药物筛选。对分离的优势菌株ZZC-JM-1进行群集运动特性、生化特性、16S rRNA测序等试验。结果表明,该优势菌为卡氏变形杆菌,该菌的生长在含1%和2%琼脂的培养基上呈现群集运动,而琼脂含量达到3%时生长被抑制;除麦芽糖和蔗糖试验为阳性外,其余生化特性均与卡氏变形杆菌一致;ZZC-JM-1的16S rRNA基因与卡氏变形杆菌的同源性达99.7%,并与卡氏变形杆菌聚为一支。小鼠腹腔注射7.35×10⁷ CFU·mL^-1 ZZC-JM-1菌液(每只小鼠注射0.2 mL),7~14 h全部死亡;病理剖检可见肺、肝、脾等器官充血、肿大。ZZC-JM-1对常见抗菌药物耐药,对庆大霉素和环丙沙星、左氧氟沙星高度敏感。综上,该研究从体温升高、呼吸道症状为主症的病牛分离到一株对小鼠具有强致死性的卡氏变形杆菌,该卡氏变形杆菌可能为肉牛呼吸道感染的主要致病菌或继发感染病原菌,应引起高度重视。

Isolation,identification and sensitive drug screening of a pathogenic Proteus cibarius strain from beef cattle

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.