猪链球菌2型不同mrp基因型与毒力的关系

Genotype of mrp and its relationship with the virulence of Streptococcus suis serotype 2

【目的】猪链球菌2型(Streptococcus suis serotype 2,SS2)是重要的人畜共患病病原,且有强弱毒株之分,但至今仍缺少合适的毒力标志基因来鉴定致病性SS2。本文旨在研究mrp基因型与SS2毒力的关系。【方法】通过PCR方法鉴定不同SS2菌株的mrp基因型。再通过"内标"化的斑马鱼感染模型和实时荧光定量PCR,分别测定不同mrp基因型菌株的毒力水平和mrp转录水平。【结果】根据PCR结果可将53株SS2分为mrp-A型(27株)和mrp-B型(26株)两种基因型;mrp-A型菌株比mrp-B菌株毒力偏强,且A型菌株中mrp转录水平更高。【结论】发现mrp基因在SS2中分布广泛,但不同菌株中mrp基因型不同,mrp-A型菌株的致病力更强。而且,以mrp非保守区域作为诊断靶点能有效鉴定SS2强毒株。

[Objective] Streptococcus suis serotype 2（SS2） is an important zoonotic pathogen, showing high diversity in virulence in different strains. Lacking suitable target（s） has, to date, hindered evaluation of virulence in SS2. Therefore, we investigated the relationship between the genotype of mrp and the virulence of SS2. [Methods] Different genotypes of mrp were identified by PCR; Virulence of SS2 strains was evaluated by internally standardized zebrafish model; and the transcription level of mrp in different strains was evaluated by real time PCR（quantitative PCR, q PCR）. [Results] Two genotypes, named mrp-A（27 strains） and mrp-B（26 strains）, were identified in 53 SS2 strains. Strains belonged to genotype mrp-A showed stronger virulence and higher transcription level of mrp than mrp-B strains. [Conclusion] mrp was widespread but various in different SS2 strains; and mrp-A strains tended to be highly pathogenic. Furthermore, the non-conservative region of mrp could be a virulence-marker for SS2.