Pathogenicity and its mechanism of Mycoplasma hyorhinis

(1)鼓室内接种缩支原体诱导中耳炎15头已知无支原体的SPF仔猪，分为3组：非治疗对照组、鼓室内接种缩支原体组和假手术组。接种mhr的仔猪在接种后7天首次出现轻度至中度的听管和鼓室炎症。14 DPI时牺牲的仔猪炎症程度加重。免疫组化及电镜检查显示，听筒及鼓室腔腔面可见Mhr。25 DPI时耳部病变减弱。Mhr在0 ~ 14 DPI时从鼓室中分离，但在25 DPI时数量减少。本实验表明，Mhr接种于SPF仔猪的鼓室可引起自限性中耳炎。(2)将经鼻接种mhrelven SPF诱导中耳炎的仔猪分为4组：阴性对照、经鼻接种Mhr、经鼻接种多杀性巴氏杆菌（Pm）、经鼻接种Mhr和Pm。6只接种Mhr的仔猪12只中耳中有10只出现亚急性耳咽炎。免疫组织化学和超微结构证实了Mhr在小细胞中的感染。仅接种Pm的仔猪均未出现中耳炎，未发现Mhr和Pm的协同作用。本实验表明鼻内感染的Mhr可引起耳咽炎，而不是Pm单独引起。这两个实验证实了我们之前的假设，即Mhr是仔猪中耳炎的主要原因

(l)Induction of otitis media by intratympanic inoculation of Mycoplasma hyorhinisFifteen SPF piglets, known to be free of Mycoplasma, were allocated in three groups : non-treatment control, intratympanic inoculation of Mycoplasma hyorhinis (Mhr) , and sham operated. Mild to moderate inflammation of the auditory tube and tympanic cavity first appeared at 7 days post inoculation (DPI) in Mhr-inoculated piglets. The degree of the inflammation was aggravated in the piglets sacrificed at 14 DPI.Immunohistochemistry and electron microscopical examinations revealed Mhr on the luminal surface of the auditory tube and tympanic cavity. The ear lesions weakened at 25 DPI.Mhr was isolated from the tympanic cavity from 0 to 14 DPI,but the amounts decreased at 25 DPI.The present experiment indicated that Mhr inoculated into the tympanic cavity could cause a self-limited otitis media in SPF piglets.(2) Induction of otitis media by intranasal inoculation of MhrEleven SPF piglets were allocated in the following 4 groups : negative control, intranasal inoculation of Mhr, intranasal inoculation of Pasteurella multocida (Pm) , and intranasal inoculation of Mhr and Pm. Subacute eustachitis was found in 10 of 12 middle ear of 6 piglets inoculated with Mhr. Immunohistochemistry and ultrastructure confirmed the infection of Mhr in the les ion. None of the piglets inoculated only with Pm showed otitis and synergistic action of Mhr and Pm was not found.The present experiment indicated that intranasally infected Mhr, but not Pm alone could cause eustachitis.These two experiments substantiated our previous hypothesis that Mhr is the primary cause of otitis media of piglets