Kudva Indira T, Evans Peter S, Perna Nicole T, Barrett Timothy J, Ausubel Frederick M, Blattner Frederick R, Calderwood Stephen B
Division of Infectious Diseases, Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
J Bacteriol. 2002 Apr;184(7):1873-9. doi: 10.1128/JB.184.7.1873-1879.2002.
Escherichia coli O157:H7 (O157) strains demonstrate varied pulsed-field gel electrophoresis patterns following XbaI digestion, which enable epidemiological surveillance of this important human pathogen. The genetic events underlying PFGE differences between strains, however, are not defined. We investigated the mechanisms for strain variation in O157 by recovering and examining nucleotide sequences flanking each of the XbaI restriction enzyme sites in the genome. Our analysis demonstrated that differences between O157 strains were due to discrete insertions or deletions that contained the XbaI sites polymorphic between strains rather than single-nucleotide polymorphisms in the XbaI sites themselves. These insertions and deletions were found to be uniquely localized within the regions of the genome that are specific to O157 compared to E. coli K-12 (O islands), suggesting that strain-to-strain variation occurs in these O islands. These results may be utilized to devise novel strain-typing tools for this pathogen.
大肠杆菌O157:H7（O157）菌株经XbaI酶切后呈现出不同的脉冲场凝胶电泳图谱，这有助于对这种重要的人类病原体进行流行病学监测。然而，菌株间PFGE差异背后的遗传事件尚未明确。我们通过回收并检查基因组中每个XbaI限制性酶切位点两侧的核苷酸序列，研究了O157菌株变异的机制。我们的分析表明，O157菌株之间的差异是由于离散的插入或缺失，这些插入或缺失包含菌株间多态性的XbaI位点，而不是XbaI位点本身的单核苷酸多态性。与大肠杆菌K-12（O岛）相比，这些插入和缺失被发现仅定位在O157基因组特有的区域内，这表明菌株间的变异发生在这些O岛中。这些结果可用于设计针对这种病原体的新型菌株分型工具。
