猪源3型链球菌分离鉴定及生物学特性研究

Isolation,Identification and Biological Characteristics of Serotype 3 Streptococcus suis

为了解天津地区某规模化猪场仔猪关节肿大并伴有严重呼吸道症状的发病原因,先后对病死仔猪进行剖检、病原菌分离鉴定、生化特性、耐药性检测、分子特征及致病力研究。结果分离到1株灰白色、半透明、边缘整齐的β溶血环的光滑型圆形小菌落,初步鉴定为革兰阳性链球菌。经细菌通用16S rRNA及链球菌荚膜多糖分型PCR鉴定,分离菌株为血清3型链球菌,并携带SrtA、orf2、Gapdh、abpb、SsnA、Lmb、znuA、gdhgdh、epf、mrp毒力基因,将其命名为TJ1806。生长曲线显示该菌株在9 h^10 h时生长达到峰值(log CFU=9.4);药敏试验结果表明分离株对阿莫西林、头孢类等敏感,对氟苯尼考、林可霉素等耐药;对小鼠表现强致病力,用细菌数为1×10^9 CFU/mL菌株于感染后12 h内致死率达100%。研究结果为了解链球菌的流行血清型多样性与防控技术研究提供了新数据。

To investigate the cause of diseased piglets with joint swelling and severe respiratory symptoms from a pig farm in Tianjin area,pathological anatomy,pathogen isolation,antimicrobial susceptibility test,molecular characteristics and pathogenicity were performed on the dead piglets.The results showed that a smooth round colony ofβ-hemolytic ring was isolated and identified as Gram-positive Streptococcus.The serotype of the isolated strain was identified by PCR using the 16S rRNA and capsular serotyping studies.The result showed that the strain belonged to S.suis serotype 3,and carried SrtA,orf2,Gapdh,abpb,SsnA,Lmb,znuA,gdhgdh,epf,mrp virulence genes,named as TJ1806.Growth curve analysis revealed that the isolated strain reached its peak at 9 h-10 h(log CFU=9.4).The antimicrobial susceptibility test showed that the isolated strain was sensitive to amoxicillin and cephalosporins,resistant to flufenicol and lincomycin.Pathogenicity test showed that significant pathogenicity for mice,the mortality rate reached 100%at infection12 h and dose of 1×10^9 cfu/mL.This study provided a new data for the serotype diversity and prevention of tachnology reaserch.