一株羊源链球菌的分离鉴定及溶血素(SLS)基因序列分析

Isolation and identification of a Streptococcus strain from sheep and sequence analysis of hemolysin (SLS) gene

为分析一株羊源链球菌分离株的部分生物学特性及溶血素(SLS)基因的变异特点,本研究自四川省某绵羊养殖场一只病死绵羊肺脏中分离到一株链球菌并命名为SZ-1,经纯化培养后观察该菌的生长、染色特性,并对其进行16S rRNA基因PCR鉴定、生化鉴定、药物敏感性试验以及SLS基因序列分析。结果显示纯化培养后的细菌于哥伦比亚血琼脂培养基上呈现β溶血;分离菌株16S rRNA基因序列与马链球菌兽疫亚种的同源性在99%以上;药物敏感性试验显示分离株对螺旋霉素、红霉素、萘啶酸、庆大霉素、氯霉素、青霉素、克林霉素敏感,对四环素和卡那霉素耐药;SLS基因与马链球菌兽疫亚种属参考菌株的核苷酸序列相比在第87、291、450位出现了单个碱基的置换,核苷酸同源性为98.77%,SLS基因遗传进化树显示SZ-1与马链球菌兽疫亚种(BHS5、CY、ATCC36524)菌株的亲缘关系最近。综上所述本实验分离株为马链球菌兽疫亚种菌,该研究结果为该菌的临床诊断、选药治疗及其SLS基因的遗传动态变异研究等奠定了基础。

In order to analyze the biological and variation characteristics of hemolysin （SLS） gene of the Streptococcus, isolated from the lungs of a diseased sheep in a sheep farm in Sichuan province and named SZ-I, the growth culture characteristics, drug sensitivity of the strain were observed, and the 16S rRNA and SLS gene sequences of the strain were sequenced and analyzed. The results showed that the purified bacteria was 13 hemolytic on the Colombian blood agar medium, and drug susceptibility experiments showed that the isolate was sensitive to spiramycin, erythromycin, nalidixic acid, gentamycin, chloramphenicol, penicillin and clindamycin, but was resistant to tetracycline and kanamycin. The SLS gene of the isolate showed single base substitution in the 87th, 291st, 450th positions and the nucleotide homology was 98.77% with that of the reference strains of the S.equi subsp, zooepidemicus. The phylogenetic tree based on SLS gene sequence showed that SZ-I and S.equi subsp, zooepidemicus strains （BHS5, CY, ATCC36524） had the closest relationship, which indicated the SZ-1 was S.equi subsp. zooepidemicus. This strdy laid a foundation for the clinical diagnosis, drug selection of the strain and research on genetic variation of SLS gene in the strain.