江苏省徐州市分离的大肠杆菌O157:H7菌株携带志贺毒素2型别的变化

Escherichia coli O157:H7 strains carrying Shiga toxin 2 variant slt2vha were isolated from Xuzhou City of Jiangsu Province

目的 研究我国分离的大肠杆菌O15 7:H7菌株的志贺毒素型别的变化。方法 使用针对志贺毒素 2及其变种的引物对进行PCR检测、细菌染色体DNA的PstI酶切后的Southern印迹实验和PCR产物的HaeⅢ、RasⅠ酶切分析 ,以及PCR产物克隆后的序列分析方法以及致病性大质粒的PstI酶切分析。结果 1999年分离自徐州市的人的 5株菌均携带slt1、slt2 ,而 2 0 0 0年从江苏省徐州市患者分离的 10株和蜣螂标本分离的 4株共计 14株大肠杆菌O15 7:H7菌株仅携带slt2vha毒素基因 ,其致病性质粒的限制性酶切图谱与 1999年的菌株相比也发生了改变。结论 鉴于江苏省徐州市1999年的分离的 5菌株全部携带slt1和slt2基因 ,结果提示该地的优势菌型发生了改变 ,可能当地大肠杆菌O15 7:H7感染的流行病学特点有关。针对slt2变异基因而设计的引物及其以此为基础进行的限制性片段长度多态性分析的方法对于研究O15 7:H7菌株的志贺毒素型别的变化能够满足特异性及灵敏性的要求。

Objective To monitor the changes of predominant Shiga toxin types of Escherichia coli O157:H7 in Xuzhou City, Jiangsu Province. Methods PCR typing with slt2-specific primer pairs (slt2cslt2, slt2v1slt2v2), hybridization of chromosome DNA digested by PstI, and DNA sequencing of PCR products. with slt2-specific primer pairs (slt2cslt2d ;slt2eslt2f) were conducted on 14 strains of E. coli isolated from diarrhea patients and dung beetles in 1999 and 2000. Results The 5 strains of E. coli isolated from diarrhea patients in 1999 carried slt1 and slt2. The 1 strains of E. coli O157:H7 isolated from diarrhea patients and the 5 strains isolated from dung beetles in 2000 only carried slt2vha, a variance of Shiga toxin 2. Conclusion The predominant Shiga toxin types of E. coli O157:H7 in Xuzhou changed 1999-2000, which may be related to the changes of epidemiological features of E.coli O157:H7 infection in Xuzhou. A genotyping method based on restriction fragment length polymorphism (RFLP) analysis of a B-subunit-encoding DNA fragment obtained by PCR described in this study is a useful tool to identify slt2 gene and slt2 variant gene in epidemiological studies with O157:H7 strains.