溶原性噬菌体在猪链球菌2型分离株中的检出和鉴定

[目的]为了研究噬菌体整合酶基因在猪链球菌2型(Streptococcus suis type 2,SS2)中的分布情况.[方法]根据噬菌体整合酶基因设计引物,建立了PCR方法,并对扩增产物进行测序.[结果]结果显示,25株SS2致病菌株均扩增出目的片段,非毒力株T15、5株其它血清型猪链球菌及兰氏C群猪源链球菌未扩增出目的片段.经丝裂霉素C诱导后,SS2致病菌株出现完全的细胞溶解,而非毒力株T15未出现溶解.SS2致病株HA9801和ZY05719诱导均产生溶原性噬菌体,分别命名为SS2-HA和SS2-ZY,电镜观察,二者均头部呈正六边形,无尾部,其核酸类型为dsDNA,可鉴定为复层噬菌体科(Tectiviridae)的成员.噬菌体SS2-HA和SS2-ZY整合酶基因序列与已报道的SS2噬菌体整合酶基因序列高度同源,显示SS2噬菌体整合酶具有较高的特异性.[结论]从SS2致病株中检出溶原性噬菌体和噬菌体整合酶基因,且噬菌体整合酶基因与SS2溶菌酶释放蛋白(mrp)等7种毒力相关基因有相关性,表明SS2的溶原性噬菌体可能与其致病性有关.

Isolation and Identification of the Temperate Bacteriophage from Isolated Strains of Streptococcus suis Serotype 2

A PCR assay was developed to study the distributional characteristics of phage integrase gene in Streptococcus suis serotype 2 (SS2). A 323bp distinct DNA target can be amplified in 25 strains of virulent SS2, while can not be amplified in avirulent strain T15, 5 strains of other serotypes (SS1, SS7, SS9) and strains of group C Streptococcus strains from pigs, which suggested that the phage integrase gene may be related to the pathogenicity of SS2 and can be consider as a detection factor of the virulent gene of SS2. The sequencing and restriction endonuclease analysis of the PCR products were also done. Comparisons between the sequences of phage integrase gene with that of SS2 strain, showed a high homology with SS2 China strains 98HAH33, 05ZYH33 and North American strain 89-1591. Complete cell lysis was observed with SS2 virulent strains but not with avirulent strain T15 after the induction by mitomycin C. Electron microscopy analysis of the lysate from SS2 virulent strains HA9801 and ZY05719 revealed the presence of phage particles. The induced phage, named SS2-HA and SS2-ZY, both have a small isometric nucleocapsid approximately 50 nm in diameter and have no tail and is therefore a member of the Tectiviridae family. The phage integrase gene sequence of phage SS2-HA and SS2-ZY shared high homologue identities with virulent SS2 strains, which suggested that the phage integrase gene of SS2 has high specify. The temperate phage and phage integrase gene can only detected from SS2 virulent strains but not from avirulent strain, and the detection of phage integrase gene was related to the virulence-associate factors of SS2, such as the muramidase-released protein gene (mrp), which suggested that the temperate phage of SS2 may be related to the pathogenicity of SS2.