猪链球菌2型感染普通仔猪模型的建立及其病理学观察

试验采用普通长白系仔猪建立猪链球菌2型动物模型,并进行详细的病理学观察。将8头仔猪随机分为试验组和对照组,用猪链球菌2型菌血静脉接种试验组,对照组接种生理盐水2 mL/头。攻毒猪5 d内全部死亡, 主要表现为脑膜炎、心外膜炎、关节炎和败血症等典型症状和病理变化,与自然感染情况相似。从感染死亡猪肺、脾、肝、心中均分离到与攻毒菌株相同的细菌。证明猪链球菌2型菌血静脉接种普通长白系仔猪可以复制出典型病例,成功建立了动物模型,对SS2致病性研究具有重要意义。     

猪链球菌2型在家兔体内的分布及致病性

用猪链球菌2型SS2-1株按109 CFU/只分别以静脉、肌肉、皮下、滴鼻、口服5种途径人工感染健康家兔,结果前4种感染途径均可引起发病并死亡,口服不发病,且以静脉感染发病最急。当分别静脉注射109,108,107,106,105 CFU/只SS2-1株,肌肉注射108,106 CFU/只SS2-1株,结果证实感染剂量与发病程度有正相关性,家兔临床症状和病理变化明显。用荧光定量PCR方法检测所有感染家兔组织的含菌量,结果提示发病程度与含菌量呈正相关,且各组织含菌量有差异。另外,人工感染家兔后在不同时间点取动物组织做菌体含量动态监测,结果提示体内含菌量随时间推移递增,发病高峰或死亡时达最高值。试验结果证明SS2-1株对家兔易感,致病性稳定,且细菌在动物体内增殖稳定并具有规律性。     

人感染猪链球菌2型的研究进展

猪链球菌2型是一种重要的人畜共患病原菌,可引起人的脑膜炎、败血症等疾病.2005年6月发生的四川疫情是由猪链球菌2型引起的人猪共同感染,流行广,发展快,人猪患病数量多.本文从病原、流行特点、感染途径、临床表现、实验室鉴定(包括培养特性、形态特征、生化特性、血清凝集、毒力基因)等方面做了详细的综述,初步探讨了2型猪链球菌病的防治方法.     

一例猪链球菌2型感染的病原分离鉴定及药敏试验

2016年2月,上海市崇明区某乡镇一规模养猪场出现40多头5~8周龄仔猪发病死亡情况。经细菌分离、分离菌株生化鉴定和PCR检测,确诊为猪链球菌2型感染。对该菌株采用K-B纸片法,进行10种常用抗菌药物的体外药敏试验,结果发现该细菌对青霉素、阿莫西林、恩诺沙星敏感,对诺氟沙星、阿奇霉素、壮观霉素、卡那霉素、阿米卡星、庆大霉素和氨苄西林不敏感。根据药敏试验结果,建议养猪户使用阿莫西林和恩诺沙星进行治疗,并做好病猪的隔离与护理。一周后病情得到控制。     

猪链球菌2型和猪圆环病毒2型混合感染的检测

2006年9月,温州某猪场断奶仔猪出现消耗性综合征,剖检的仔猪主要表现为淋巴结肿大和脑膜炎等。分别设计针对猪圆环病毒2型CAP蛋白和猪链球菌2型溶血素蛋白基因的特异性引物,用PCR技术从患病仔猪的肺脏、脾脏、淋巴结和脑组织中扩增出了猪链球菌2型和猪圆环病毒2型特异性片段。结合本病的临床症状和病理变化,病例确诊为猪链球菌2型和猪圆环病毒2型的混合感染。     

猪链球菌2型的鉴定及其毒力因子检测

猪链球菌的感染不仅对养猪业造成巨大的损失,同时对公共卫生尤其是相关从业人员的生命造成威胁,严重感染引起死亡.根据参考文献,设计了1对猪链球菌2型特异性引物.对四川分离的7株链球菌、江苏分离的1株、北京分离的6株和菌种中心保存的5株C群马链球菌兽疫亚种、1株D群链球菌、4株R型链球菌、2株S群链球菌和E、F、G、K、L、M、N、O、P群链球菌各1株进行了检测.结果7株四川分离株均为2型;1株江苏分离株为2型;6株北京分离株有3株为2型;1株R群、2株s群链球菌为2型猪链球菌.对检测出的14株猪链球菌2型的毒力因子做进一步检测.MRP基因检出率为92.9%(13/14);EF基因检出率为100%(14/14);sly基因检出率为71.4%(10/14);Cps2A基因检出率为92.9%(13/14);gapdh基因检出率为64.3%(9/14);FBPS基因检出率为92.9%(13/14);orf2基因检出率为71.4%(10/14).毒力因子全为阳性的菌株有6株,MRP-EF+菌株有2株.本研究从259份健康猪扁桃体中分离到16株2型猪链球菌,健康猪带菌率为6.2%(16/259).16株猪链球菌2型中,MRP、EF、Cps2A全为阴性,只从1株2型猪链球菌中检测到了sly基因(1/16);gapdh基因检出率为56.25%(9/16);FBPS基因检出率为75.0%(12/16);Orf2基因检出率为37.5%(6/16).     

2015年华中地区猪链球菌2型感染的血清学调查

监测华中地区22个未免疫猪链球菌疫苗猪场2015年不同月份、不同猪群的猪链球菌2型(SS2)抗体水平,以期揭示SS2的感染流行情况。共收集923份血清样品,结果 442份为SS2抗体阳性,阳性率为4789%,表明SS2在华中地区感染普遍存在;统计分析发现不同月份感染阳性率差别较大,其中6~9月份最高,说明该病与季节有一定的关系,在夏季尤其应该注意该病的防控;不同阶段猪群统计结果表明保育猪阳性率最低,更应做好保育猪的SS2免疫防控工作。     

Passive immunization of pigs against experimental infection with Streptococcus suis serotype 2

The safety and protective efficacy of a horse antiserum raised against inactivated whole cell preparations of Streptococcus suis serotype 2 was investigated in pigs by experimental challenge. The antiserum was evaluated in two similar experiments each comprising 12 4-week-old pigs treated with 6 ml of antiserum the day before challenge and four pigs used as challenge controls. Pigs were infected by subcutaneous injection with approximately 10(11) colony forming units of S. suis serotype 2. Clinical disease in the pigs that could be attributed to infection with S. suis was reduced from 88 to 35% (P = 0.015). The percentage of pigs with lesions that could be associated with S. suis was reduced from 88 to 22% (P = 0.002) and isolation of S. suis serotype 2 was reduced from five (63%) out of eight pigs in the combined challenge control groups to 3 (13%) out of 23 pigs in the combined treatment groups. These results indicate that passive immunization of pigs may be a way to reduce or control S. suis serotype 2 infections in pigs.     

2016年四川省猪链球菌2型感染的血清流行病学调查

猪链球菌是一种重要的人兽共患病原菌,其中以猪链球菌2型致病性最强。本研究通过ELISA方法,对2016年采集自四川省21市(州)的1 604份猪血清样品进行猪链球菌2型的检测。结果表明:猪链球菌2型的阳性检出率为9.41%(151/1604),其中规模场阳性检出率为7.67%(66/860),散养户阳性检出率为11.42%(85/744)。本研究为四川地区猪链球菌病的防控提供了理论依据。     

从非法屠宰的猪肉中检出猪链球菌2型

从送检的非法屠宰的猪肉中分离到1株链球菌,结合其培养特性、生化特性、血清定型、PCR鉴定、动物实验等对其进行了鉴定。用国际通用的链球菌乳胶分型诊断液检测,结果表明其不属于链球菌兰氏分群的A～G群。但它凝集猪链球菌2型标准阳性血清,三重PCR扩增及测序结果表明其为猪链球菌2型。分离菌具有猪链球菌2型的CPS、MRP、EPF、SLY、ORF2五种主要毒力因子;将分离株人工静脉注射新西兰兔4只,均在12～24h均死亡,腹腔注射8只BALB/c小鼠后,3周内死亡5只,3只未死亡。     

荧光实时定量PCR方法检测猪链球菌2型

以猪链球菌2型的荚膜多糖抗原编码基因cps2J为靶基因设计引物,利用SYBR GreenⅠ能特异地与双链DNA结合发出荧光的特性,以ABI7000为平台,建立荧光实时定量PCR检测猪链球菌2型的方法。该方法检测猪链球菌2型参考株和猪链球菌2型国内分离株都呈阳性,具有良好的特异性。整个检测过程于2h内完成,检测限度为24CFU,标准曲线的相关系数为0.997。对5份采集于猪链球菌2型病猪的病料进行检测,结果表明肝脏和脾脏最适于检测。     

Microarray analyses of THP-1 cells infected with Streptococcus suis serotype 2

Streptococcus suis serotype 2 (S. suis 2) is a pathogen responsible for several diseases in both pigs and humans. To gain more insight into the pathogenesis of this organism, an oligonucleotide (oligo)-based microarray was used to investigate gene expression changes in human monocytic cells (THP-1) in response to exposure to S. suis 2 strain SC19. A total of 328 differentially expressed genes were identified. These differentially expressed genes belonged to a variety of functional categories, including genes involved in apoptosis, immunity, signal transduction, chemokine production and the ubiquitin-proteasome system. Our findings can be of interest for future research.     

猪链球菌2型广西分离株的生物学特性鉴定

猪链球菌2型是一种人兽共患病原菌,主要引起猪脑膜炎、关节炎、心内膜炎、败血症和突然死亡等。在我国许多地方发病率呈不断上升趋势。各年龄段的猪都可感染此病,但多发于3～12周龄的猪,尤其是断奶仔猪易感染此病。猪链球菌2型不但对猪有致病性,而且可引起人的感染并致死。我国江苏省、四川省部分地区暴发2型猪链球菌病导致人员感染致死。本试验对从发病猪中分离到的链球菌株进行了形态、培养特性和使用猪链球2型、1型抗血清进行凝集试验,结果证明4株细菌为荚膜2型猪链球菌。PCR方法检测其5种毒力因子和对仔猪、家兔、小鼠的致病性试验。现将鉴定和试验结果报告如下。     

Immunization of pigs against Streptococcus suis serotype 2 infection using a live avirulent strain.

Streptococcus suis capsular type 2 is still an important cause of economic losses in the swine industry. At the present time, vaccination of pigs against this infection is generally carried out with autogenous bacterins and results are equivocal. In this study, the protective effect of a live avirulent S. suis type 2 strain (#1330) which had induced a good protection in mice, was evaluated in swine. The experiment was performed in triplicate using 4 week-old piglets. A total of 15 piglets were vaccinated 3 times, 15 others were vaccinated 2 times, and 15 piglets were injected 3 times with sterile Todd-Hewitt broth. Using an indirect ELISA, an increase in the IgG response to S. suis antigens was noted in 27 of the 30 vaccinated piglets. On day 21 post-vaccination, all animals were challenged intravenously with a virulent S. suis type 2 strain (#999). In the 2 vaccinated groups, 26 animals were fully protected. Only 1 out of the 15 piglets vaccinated 3 times developed mild clinical signs. In the group vaccinated twice, 3 piglets showed clinical signs and 1 of them died after the challenge. In the control group, 7 animals died out of the 11 with clinical signs of infection. In conclusion, a protective immunity was observed in swine when using strain 1330. However, more studies are needed to assess the use of a live S. suis strain in a vaccine for pigs.     

Rapid detection of Streptococcus suis serotype 2 in weaned pigs

A survey to detect Streptococcus suis serotype 2 in 1,716 weaned pigs was done in Quebec. Forty-nine sow herds were included in this survey: in 26 herds, S suis serotype 2 had been isolated during the preceding 12 months and in 23 herds (control), the organism had not been detected during a previous study. Swab specimens of the nasal cavity and tonsils of pigs were obtained for bacteriologic culture, and S suis serotype 2 was easily detected by the use of brain-heart infusion agar containing a Streptococcus-selective supplement and 5% goat antiserum raised against S suis serotype 2. After measurement of the diameter of the precipitation zone of 539 isolates, a slide agglutination test was performed to identify the S suis serotype 2 isolates. The mean precipitation zone diameter obtained for group S suis serotype 2 was larger (P less than 0.001) than that for the group designated as "others". With slide agglutination test results as reference and on the basis of discriminant analysis to stimulate detection of S suis serotype 2, 93.1% of all isolates were correctly classified, using the precipitation zone diameter as unique classification criterion. Relative specificity was 94.5% and relative sensitivity was 88.7%. Use of the precipitation zone diameter on a quantitative basis led to the proposal of a simple and reliable technique to screen swine herds for S suis serotype 2 in weaned pigs. Nasal and tonsillar swab specimens were obtained and analyzed concurrently for S suis serotype 2. The organism was found in both sites in only 20.4% of 103 carrier pigs.(ABSTRACT TRUNCATED AT 250 WORDS)