O157∶H7原噬菌体消除菌株的鉴定与分析  

Identification and analysis of prophage curing mutant of Enterohemorrhagic Escherichia coli O157∶H7

作　　者：刘军[1] 冯书章[1] 孙洋[1] 郭学军[1] 常国权[1] 尹铁勇[1] 

机构地区：[1]军事医学科学院军事兽医研究所,长春130062

出　　处：《中国人兽共患病杂志》2005年第1期45-48,51,共5页Chinese Journal of Zoonoses

基　　金：国家自然科学基金资助项目 (No .3 0 2 70 985 )

摘　　要：目的　O15 7∶H7是一种重要的新发传染病病原 ,它主要引起出血性或非出血性腹泻 ,出血性结肠炎 (HC)或溶血性尿路综合征 (HUS)等。研究表明引起HC和HUS的主要毒力因子是由整合到O15 7基因组中的原噬菌体编码的志贺毒素(Stx) ,包括Stx1和Stx2 ,它们分别由原噬菌体 933v和 933w所编码。由于原噬菌体本身具有潜在的不稳定性 ,本研究以O15 7∶H786 - 2 4为始发菌株 ,将其进行传代培养 ,筛选原噬菌体消除菌株 ,对原噬菌体在O15 7基因组中的整合位点进行分析 ,并用Vero细胞对原噬菌体消除菌株的细胞毒性进行鉴定。结果筛选到了原噬菌体消除后的O15 7菌株 ,该菌株丧失了对Vero细胞的毒性作用。序列比较分析表明原噬菌体 933v的整合位点位于O15 7∶H7EDL933基因组中第 2 96 6 137位的相对位置 ,在整合位点两侧有一个 2 0bp的直接重复序列 ,原噬菌体 933w的整合位点位于基因组中第 1330 82 6位的相对位置 ,在整合位点两侧有一个 7bp的直接重复序列。该研究证实了编码Stx的原噬菌体具有不稳定性 ,原噬菌体对O15 7的致病性具有重要作用 ,也提示原噬菌体在致病菌的进化过程中也具有重要作用。Enterohemorrhagic Escherichia coli (EHEC) is a new important human pathogen. The most common serotype of EHEC is O157:H7. One of important virulence factors of EHEC O157∶H7 is Shiga toxin (Stx), encoded by prophages (933v and 933w) integrated into the chromosome of O157∶H7. This potent cytotoxin leads to death and many other symptoms in patients infected with EHEC O157∶H7. Due to potential instability of the prophages carrying the stx gene, in this study, the prophage of O157:H7 86-24 strain was cured with serial passages of bacteria, confirmed by PCR and DNA sequencing. The cultural supernatant of O157 prophage curing mutant was inoculated into Vero cells, indicating that the prophage curing mutant of O157 lost the toxigenicity to Vero cells. The sequence analysis indicated that the integrate sites of prophages 933v and 933w Located at 2966137 and 1330826, respectively. There were 20bp and 7bp direct repeat sequences flanking the prophages 933v and 933w. The flanking repeat sequences are termed as attachment sites (attL and attR). The results of this study confirm the instability of prophage, and suggested that the prophage plays important role in the pathogenicity of O157∶H7, and in the evolution of pathogenic bacteria.

关 键 词：O157:H7 原噬菌体 志贺毒素 

分 类 号：R378.2[医药卫生—病原生物学]