细菌毒力岛是在基因水平认识细菌毒力因子的新概念，开辟了细菌致病性研究的新思路。本研究以猪链球菌2型为模型，分析其两种毒力因子（MRP和EF）的理化特性、致病性及免疫原性，进而探讨是否存在毒力岛基因。在理论上深化对猪链球菌致病机理的认识；为掌握该病的流行规律提供依据；建立该病的检测手段，提供免疫预防新技术，具有潜在的应用价值。

The key of study on virulence factor of Streptococcus suis type 2 is to expound its mechenism of pathogenicity. The hemolysin of Streptococcus Suis type 2, as an important virulence, was studied systemly, including the cultural conditions, chemical characters, biological characters purified and detection methods. It was concluded that the hemolysin of Strep. Suis type 2 is closely related to the pathogenicicity and is a good immunogen for developing subunit and genetic vaccine. A new gene, orf 2, was found from the isolate HA9801 by the method of PCR. Furthermore, orf 2 was detected from other pathogenic streptococcus isolates. It can be promted that the orf 2 is an important virulent gene. On the other hand, the pathogenicity island of Strep. Suis type 2 was studied also, and the resoults show that there are no pathogenicity island characters in the virulent genes of Streptococcus suis type 2 .