摘要： CDT毒素是多种革兰氏阴性致病菌的毒力因子。为了阐明CDT毒素在副猪嗜血杆菌不同菌株中的分布及其遗传变异情况,本试验对从浙江省不同地区猪场临床发病猪中分离到的41个副猪嗜血杆菌分离株进行了CDT基因PCR扩增,并对其中21个分离株CDT 3个亚基进行了基因测序及氨基酸序列分析。结果表明:所有41个临床分离株中都可以检测到CDT 3个亚基的基因,其中cdtA蛋白的氨基酸序列在不同副猪嗜血杆菌菌株中最为保守,同源性≥97.8%;cdtB及cdtC蛋白氨基酸序列变化较大,同源性均≥92.1%。其中cdtB亚基与牛DNase I活性关键位点的氨基酸残基具有一致性,且这些位点的氨基酸残基在不同菌株中高度保守,可能对CDT诱导细胞凋亡的活性起着重要作用。为研究副猪嗜血杆菌CDT的生物学作用提供了新的信息。

关键词: 副猪嗜血杆菌, CDT, 同源性

Abstract: Cytolethal distending toxin(CDT) is a virulence factor of gram negative bacteria． The aim of this study was to investigate the prevalence and phylogenetic relationships of CDT genes in different clinical isolates of Haemophilus parasuis． The presence of CDT gene was detected by PCR against three subunits gene of the toxin respectively． Of the 41 clinical isolates from pig farms of Zhejiang province，CDT genes of 21 isolates were sequenced． It shows that CDT gene of three subunits were presented in the genome of all 41 isolates used in this study． CdtA is the most conserved protein with more than 97． 8% amino acid sequence identity compared to cdtB and cdtC(both≥ 92． 1%). The catalytic residues in cdtB corresponding to bovine DNase I are highly conserved among all the isolates， which may indicate a key role of cdtB in the activity to induce mammalian cell apoptosis． This artical provide new information which will facilitate study of the biological activity of Haemophilus parasuisCDT．

Key words: Haemophilus parasuis, CDT, Identity

中图分类号: 

• Q78