猪链球菌9型国内分离株毒力基因的检测及小鼠免疫试验

Detection of the virulence-associated genes of Streptococcus suis type 9 isolates in China and their protective efficacy in mice

通过检测7株猪链球菌9型(SS9)国内分离株的毒力基因,比对7株SS9荚膜合成基因cps9j的300 bp碱基序列,以及进行7株SS9对小鼠的毒力试验和免疫保护试验,初步探讨了国内SS9的毒力特性。结果显示,7株SS9均缺失胞外因子(epf)和溶血素(sly)基因,溶菌酶释放蛋白基因(mrp)存在于GZ0665和GD0606株,orf2仅存于GZ0665株;病猪脑脊液分离株GZ0665与从健康猪扁桃体分离的6株SS9的cps9j同源性低;在7株SS9分离株和SS2分离株HA9801中,只有GZ0665和GD0606株能致死小鼠;用灭活的GZ0665菌株免疫的小鼠对同源菌株GZ0665及GD0606株攻击的保护率均为100%(10/10),用灭活的GD0606和未灭活的GD0627菌株免疫的小鼠对GD0606株攻击的保护率分别为80%(8/10)和50%(5/10),而对GZ0665株攻击的保护率分别为60%(6/10)和30%(3/10)。证实,SS9病猪脑脊液分离株的毒力基因有别于SS9健康猪扁桃体分离株和SS2。表明,小鼠可以用来区分SS9病猪脑脊液分离株与健康猪扁桃体分离株的致病力。

The 7 virulence-associated genes in 7 isolates of Streptococcus suis type 9（SS9） in China were detected. Genes epf and sly were not found in any of the 7 strains, rnrp gene was found in GZ0665 and GD0606 strains, and off2 gene was detected in GZ0665 strain only. GZ0665 isolate from a pig with meningitis had low homology of cpsgj with other SS9 isolates from pig tonsils,by comparing their 300 bp cpsgj sequence. GZ0665 and GD0606 caused mice death,but others including SS2 virulent strain HA9801 did not. GZ0665 had 100% （10/10） protective rate in mice against challenge with strains GZ0665 and GD0606. GD0606 and GD0627 strains had 80% （8/10） and 50% （5/10） of protective rates for mice against GD0606 strain challenge, and had 60 % （6/10） and 30 % （3/10） for mice against GZ0665 strain challenge. It was concluded that virulence-associated genes in GZ0665 differed from those in other SS9 strains and SS2, and mice could be used to evaluate the virulence of SS9 isolates