猪链球菌2型的分子流行病学研究

Study on Molecular Epidemiology of Streptococcus suis Type 2

目的 了解猪链球菌 2型高发地区 (疫区 )与少发地区 (非疫区 )猪群的带菌率及其毒力因子MRP与EF的分布情况 ,探讨猪链球菌 2型的发生及其流行规律。方法 分别从不同地区采集正常屠宰猪或活体采集成年猪扁桃体 ,经接种马丁汤培养基增菌培养后 ,用PCR方法进行 2型猪链球菌的检测 ,同时检测各 2型菌的主要毒力因子溶菌酶释放蛋白 (MRP)与细胞外蛋白因子 (EF)基因 (mrp和epf)。 结果 除少数猪群外正常猪群中猪链球菌 2型的带菌率普遍较高 ,为 31 6 %～77% ,平均为 4 0 9% ,且疫区 (39% )与非疫区 (42 % )差异不明显。但毒力因子mrp和epf的阳性率疫区与非疫区存在明显差异 ,非疫区的 2型菌株除极少数表现为mrp+ epf-(5 % )或mrp-epf+ (5 % )外 ,绝大多数 (90 % )都表现为对猪无毒力的mrp-epf-表现型 ,无一株表现为mrp+ epf+ ;来自疫区的所有 16株 2型菌株均为对猪有强毒力的mrp+ epf+ 表现型。结论 正常猪群中 2型猪链球菌的带菌率与猪群是否暴发流行该病可能并无直接关系 ,但疫区猪群mrp+ epf+ 表现型菌株检出比率较高 ,提示携带mrp+ epf+

Aim To understand the positive rate of Streptococcus suis type 2(S suis type 2)and the phenotypes of their Muramidase Released Protein(mrp) and Extracellular Protein(epf)in the herds known to be infected and the herds without a S suis history recent years Method S suis type 2 and the phenotypes of their mrp and epf in tonsillar specimens from slaughtered healthy pigs from different districts were identified for by PCR assays Results There was no obvious difference between the herds known to be infected and the herds without a S suis history recent years But that the difference in the phenotypes of mrp and epf between the herds is interesting In the herds without a S suis history,90%(18/20) of S suis type 2 were mrp -epf - and no was mrp +epf + On the contrary,all 16 strains of S suis type 2 from the herds infected in 1998 and 1999 were the phenotype of mrp +epf + Conclusion The positive rate of S suis type 2 in herds isn't associated with the disease,but the positive rate of typical virulent phenotype mrp +epf + is probably very important for the disease