Mycoplasma Dispar As a Causative Agent in Pneumonia of Calves

Three field strains of Mycoplasma dispar were inoculated, by aerosol inhalation, into a total of eight naturally-born, colostrum-deprived calves. All three strains produced macroscopic pneumonia, each in one calf. Histopaithologically an exudative bronchitis accompanied by moderate interstitial cell proliferations was found.Reisolation studies indicated that the entire respiratory tract is the natural habitat of Mycoplasma dispar, which apparently does not spread via the blood stream.     

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。     

Antimicrobial susceptibility of Mycoplasma hyorhinis

A broth microdilution technique was used to determine the antimicrobial susceptibility of 15 field isolates of Mycoplasma hyorhinis to 10 antimicrobial agents, representative of different classes, and contrasting newer agents to existing ones. For the macrolides, the MIC(90) for tylosin and tilmicosin was 1 and 4 microg/ml, respectively, but was > or = 16 microg/ml for erythromycin. Tetracycline, lincomycin and enrofloxacin each had an MIC(90) of 2 microg/ml. The mycoplasma had similar levels of susceptibility to the aminoglycoside and aminocyclictol classes exhibiting an MIC(90) of 4 microg/ml for gentamicin and 2 microg/ml for spectinomycin. The isolates exhibited high MICs to trimethoprim/sulfamethoxazole with an MIC(90) > or = 16/304 microg/ml. In summary, M. hyorhinis isolates from the US had low MICs against a variety of antimicrobials tested, with the exception of erythromycin and trimethoprim/sulfamethoxazole.     

规模化猪场猪气喘病的诊治及防控

猪气喘病又称猪地方流行性肺炎，是由猪肺炎支原体引起的猪的一种慢性呼吸道传染病，可以感染不同年龄、性别、品种和用途的猪，主要症状是咳嗽和气喘。本病一年四季都可以发生，在新发病的猪群中常呈暴发性流行，且病势剧烈，多为急性经过，发病率和病死率偏高。本病在我国流行十分广泛，特别是在规模化养殖场中，同一猪群的感染率和发病率甚至可达到100％，而且一旦感染就很难彻底净化，环境一旦有异常变化，就易暴发。随着我国集约化养猪业的发展，     

Enzootic Pneumonia in Pigs: Propagation of a Causative Mycoplasma in Cell Cultures and in Artificial Medium

Three strains of a new species of mycoplasma were recovered from pneumonic pig lungs, known free of Mycoplasma hyorhinis, by prolonged incubation in pig testicle cell cultures. The three strains produced a characteristic cytopathic effect in the cell cultures. A highly enriched meat-infusion-broth medium was evolved and permitted regular propagation of these organisms. Pneumonia could consistently be produced by intratracheal inoculation of pigs with the mycoplasma propagated in the enriched broth medium or in cell cultures. The mycoplasma were recovered from the lungs of experimentally infected pigs by inoculation into the broth medium. Comparative studies of the pneumonia producing mycoplasma and of M. hyorhinis were carried out in cell cultures, broth media, and in pigs infected experimentally by different routes. The morphological characteristics of the mycoplasma, grown in the different media, are described and illustrated.     

Enzootic Pneumonia of Pigs: Identification of a Causative Mycoplasma in Infected Pigs and in Cultures by Immunofluorescent Staining

Immunofluorescent staining has been used to identify Mycoplasma hyopneumoniae in smears of broth cultures, in infected pig testicle cell cultures, and in frozen cut sections of pneumonic lungs from field and experimentally produced cases of enzootic pneumonia. In the pneumonic pig lung, fluorescent staining was limited to the surface of the bronchial and bronchiolar epithelium and to the contained exudate. In a series of trials using experimentally infected pigs fluorescence was not detected until 25 days post-infection and was regularly seen in pigs killed thereafter. Porcine immune globulin precipitated from the serum of experimentally infected pigs and conjugated with fluorescein isothiocyanate was reactive and specific for the detection of M. hyopneumoniae. Immune globulin conjugates prepared from the serum of hyperimmunized rabbits were reactive but in some cases produced a faint non-specific staining of frozen tissue sections. No such non-specific reactions were noted on stained culture smears or cell cultures.

Fluorescence was not seen in known positive preparations stained with non-immune pig globulin conjugates or in preparations from uninoculated cell cultures or pigs, stained with non-immune or immune globulin conjugates.

Mycoplasma hyorhinis was detected by immunofluorescent staining with homologous conjugates, in smears of broth cultures and in tissue sections from pigs with polyserositis.

Immunofluorescent staining was found to be species specific and useful for the early species identification of mycoplasma isolated from pigs.

     

Intranasally inoculated Mycoplasma hyorhinis causes eustachitis in pigs

Specific-pathogen-free pigs were experimentally inoculated with Mycoplasma hyorhinis, Pasteurella multocida, or both bacterial isolates to evaluate the role of these bacteria in the pathogenesis of otitis media. Six pigs were inoculated intranasally with 4.4 X 10(8) colony-forming units (CFU) of M. hyorhinis. Twenty-one days later, three of these six pigs were inoculated intranasally with 5.0 X 10(8) CFU of P. multocida. Three additional pigs were also inoculated intranasally at the time with P. multocida alone. Two pigs served as uninoculated controls. Seven days later, all pigs were euthanatized. Histologically, subacute inflammation was found in 10 auditory tubes of six pigs and two tympanic cavities of two pigs inoculated with M. hyorhinis. Immunohistochemically, M. hyorhinis antigens were detected on the luminal surface of eight of 10 inflamed auditory tubes, and ultrastructural examination confirmed mycoplasmal organisms in two pigs. M. hyorhinis was isolated from the inflamed tympanic cavities of two pigs. None of the pigs inoculated only with P. multocida had otitis, and P. multocida was not isolated from the tympanic cavity. These findings indicate that M. hyorhinis can cause eustachitis but rarely otitis media in specific-pathogen-free pigs.     

Chronological Development of Mycoplasma hyorhinis and Mycoplasma hyosynoviae Infections in Cultures of a Swine Synovial Cell Strain

The sequential development of Mycroplasma hyorhinis and Mycoplasma hyosynoviae was observed in cultures of a swine synovial fluid cell strain. An early transitory filamentous phase was observed with M. hyorhinis infection followed by the development of cell-associated, relatively large, round structures and some ring forms. Infection with M. hyorhinis was characterized by a generalized distribution of the organism and a severe cytopathic effect.

Infection with M. hyosynoviae was represented by the development of circumscribed foci of small pleomorphic structures and a milder effect on the cells. At a high multiplicity of infection, this organism became associated with the cytoplasmic membranes of the cells.

     

猪支原体肺炎的诊断及防制

支原体是引起猪下呼吸道疾病和肺炎的常见病因。在世界范围内,支原体病对每一猪群都造成明显的经济损失。控制支原体病的措施包括改善通风状况、控制温度、全进全出的饲养管理、使用抗生素及疫苗等。对支原体病的诊断和确定可能存在继发性疾病的并发或与原发性疾病的互作是很重要的。     

Fluorescence serological and culture detection of Mycoplasma hyopneumoniae and Mycoplasma hyorhinis in swine lungs

The present paper compares the fluorescence-serological detection of M. hyopneumoniae and M. hyorhinis in frozen sections with cultural procedures. In 161 lungs of swine the agent of enzootic pneumonia, M. hyopneumoniae, was found almost exclusively in frozen sections (22 times). Only one strain was cultivable. M. hyorhinis was detected 59 times by culture but only 18 times in the sections. For the detection of M. hyopneumoniae therefore the fluorescence-serological investigation of lung sections is the preferable method.     

Virus Pneumonia of Pigs; Attempts at Propagation of the Causative Agent in Cell Cultures and Chicken Embryos

Two strains of the agent of virus pneumonia, were tested for the ability to propagate in 12 types of cell cultures and in chicken embryos. The 5 primary cell cultures used were: swine kidney, lung, bone marrow, testicle, and chicken embryo kidney; and the 7 serial passage cell cultures were: swine kidney, kidney-tumor, testicle, bone-marrow, bovine kidney, and human cervical carcinoma (HeLa). The agent of virus pneumonia was propagated in primary swine kidney and in HeLa cell cultures as shown by the production of typical gross and microscopic lesions in pigs inoculated with cell future fluids. Third passage cell culture fluids, produced typical gross lesions in pigs, but fourth passage cell culture fluids produced only microscopic lesions, and no lesions were produced by sixth and eleventh passage fluids. Control pigs receiving fluids from uninoculated cell cultures remained free of gross or microscopic lesions, as did uninoculated controls. Cytopathic effects were not detected in any of the inoculated cell cultures and no cellular changes were detected by staining with Giemsa stain or acridine orange.

Neither lesions nor deaths occurred in chicken embryos inoculated with both strains of virus pneumonia virus. Pneumonia was not produced in pigs inoculated with suspensions from second chicken embryo passage of the 2 strains inoculated by the chorioallantioic sac, the amniotic sac, and the yolk sac routes.

Identical gross and microscopic lesions were produced in pigs inoculated with either pneumonic lung suspensions or with virulent cell culture fluids. Gross lesions consisted of areas of light to reddish-purple consolidation usually limited to the anterior, cardiac, and intermediate lobes of the lungs. Pleuritis and pericarditis were never present in experimentally produced virus pneumonia. The microscopic lesions were characterized by: 1. perivascular and peribronchiolar lymphoid infiltration and hyperplasia, 2. alveolar interstitial thickening and infiltration, and 3. alveolar exudates consisting of alveolar cells, lymphocytes, plasma cells, and neutrophiles.

     

猪肺炎支原体和猪鼻支原体双重PCR检测方法的建立与应用

根据猪肺炎支原体(Mhp)和猪鼻支原体(Mhr)的16S rRNA基因设计3条引物, 建立Mhp和Mhr的双重PCR检测方法,并对该方法进行了特异性和敏感性试验,并使用建立的方法检测了临床样品和疫苗样品。结果显示该方法具有良好的特异性,最低可检测到0.66ng 的Mhp基因组DNA和0.58 ng Mhr基因组DNA,临床样品和疫苗样品检测结果与普通PCR检测结果一致。该双重PCR方法,可用于Mhp与Mhr的鉴别、诊断以及疫苗纯粹性检查,快速而准确。