猪链球菌3型分离菌的生物学特性及致病性

Biological characteristics and pathogenicity of Streptococcus suis serotype 3 isolates

为研究猪链球菌3型(Ss3)分离菌的生物学特性及致病性,对疑似Ss进行培养、染色、生化试验、猪链球菌PCR鉴定、血清分型PCR鉴定、多位点序列分型(MLST型)PCR鉴定,并对小鼠和仔猪进行致病性试验。结果显示,3株分离菌(分别命名为JSHZ菌株、GD7菌株、H30菌株)均呈革兰氏阳性,Ss PCR鉴定显示为阳性,血清分型PCR结果表明分离到的菌株为Ss3,序列型(ST)分别属于ST27型(JSHZ菌株)、ST1004型(GD7菌株)和ST 117型(H30菌株);3株分离菌的生化特性与猪链球菌相符;3株分离菌经腹腔注射均可致死Balb/C小鼠,半致死量(LD50)分别为2.0×107CFU/ml、3.5×107CFU/ml和2.5×108CFU/ml。选择3株分离菌中毒力较强的JSHZ菌株进行仔猪致病性试验,感染仔猪会出现明显的关节红肿、跛行,体温多数升高至40.5~41.8℃,精神萎靡,食欲减少等症状;高剂量(每头仔猪注射JSHZ菌数6.0×109 CFU)处理可致仔猪出现食欲废绝、神经症状,甚至濒死,并在其脑组织中分离到Ss3。本研究结果为进一步开展Ss3的防控研究奠定了基础。

In order to study the biological characteristics and pathogenicity of Streptococcus suis serotype 3(Ss3)isolates,three strains of suspected Streptococcus suis(Ss),strain JSHZ and GD7 isolated from acute dead piglets,strain H30 isolated from healthy piglet,were cultured,stained and identified by Ss PCR,Ss serotyping PCR,multilocus sequence typing(MLST)PCR,biochemical tests,and pathogenicity tests were conducted on mice and piglets.The results showed that all the three isolates were Gram-positive and Ss3.The sequence type(ST)of JSHZ,GD7 and H30 belonged to ST27,ST1004 and ST117,respectively.The biochemical characteristics of the three strains were consistent with Ss.The three strains could be lethal to mice by intraperitoneal injection,and the median lethal dose(LD50)were 2.0×107CFU/ml(JSHZ),3.5×107CFU/ml(GD7)and 2.5×108CFU/ml(H30),respectively.The JSHZ with highest virulence to mice was selected for the pathogenicity test on piglets.The results showed that for piglets,JSHZ could cause obvious arthritis and limping,raise the body temperature to 40.5-41.8℃,reduce the spirit and appetite.High dose of JSHZ(6.0×109 CFU)could cause piglet anorexia,neurological symptoms and even being dying,and Ss3 was isolated from the brain tissues of dying piglet.This study can lay a foundation for further research on prevention and control of Ss3.