1株猪鼻支原体的分离鉴定及致病性

猪鼻支原体是猪场感染率极高的一种支原体，可引起多发性浆膜炎、关节炎等症状。目前尚未建立标准的猪鼻支原体发病模型，也缺乏标准强毒株。本研究从某猪场发病猪的关节液中分离得到一株支原体，通过PCR检测、菌落形态观察、菌体形态电镜分析、菌株MLST分型等方法对其进行了鉴定，确认其为猪鼻支原体。为评价菌株致病性，将该分离株接种1月龄自然分娩不吃初乳猪（SF-pCD猪），试验猪在感染后出现关节肿胀、跛行等临床症状，日增重显著低于对照组，并出现部分死亡。剖检结果显示感染组出现胸膜炎、腹膜炎、心包炎及关节炎，肺部组织病理分析显示为间质增宽，无虾肉样病变。从发病猪的扁桃体、肺、心及关节积液中可再次分离到攻毒株。综上，本研究分离获得一株猪鼻支原体，人工感染猪后可出现典型的发病症状，猪鼻支原体发病模型的建立为致病机制及疫苗研究奠定了重要的基础。

Isolation,Identification and Pathogenicity of a Mycoplasma hyorhinis Strain

Mycoplasma hyorhinis is ubiquitous in the pig population and could cause systemic diseases such as polyserositis and polyarthritis. At present, there is no standard challenge model for M. hyorhinis, as well as standard virulent strain. In this study, a M. hyorhinis strain was isolated from the synovial fluid of a pig with typical clinical symptoms. It was identified to be M. hyorhinis by analysis of PCR, colony and bacterial morphology identification and multi locus sequence typing (MLST). To evaluate the pathogenicity of the strain, 1-month-old snatch-farrowed, porcine-colostrum-deprived (SF-pCD) pigs were inoculated with the isolated strain. The infected piglets showed obvious joint swelling and lameness. The daily weight gains of the infected piglets were significantly lower than those of the pigs in the control group. Three of the infected piglets died during the observation period. At necropsy, the infected pigs showed extensive pleurisy, peritonitis, pericarditis and arthritis. The histopathological analysis of the lung tissues showed thickened alveolar septa but no shrimp-like lesions. The challenge strain can be re-isolated from the tonsils, lungs, hearts and joint effusions of the infected pigs. To sum up, a strain of M. hyorhinis was isolated in this study, and the pigs artificially infected which showed typical symptoms. The establishment of the challenge model laid an important foundation for the study of M. hyorhinis pathogenic mechanisms and vaccine development.