Kotewicz Michael L, Mammel Mark K, LeClerc J Eugene, Cebula Thomas A
Division of Molecular Biology, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, Laurel, MD 20708, USA.
Microbiology (Reading). 2008 Nov;154(Pt 11):3518-3528. doi: 10.1099/mic.0.2008/019026-0.
Optical maps for five representative clinical, food-borne and bovine-derived isolates from the 2006 Escherichia coli O157 : H7 outbreak linked to fresh spinach in the United States showed a common set of 14 distinct chromosomal markers that define the outbreak strain. Partial 454 DNA sequencing was used to characterize the optically mapped chromosomal markers. The markers included insertions, deletions, substitutions and a simple single nucleotide polymorphism creating a BamHI site. The Shiga toxin gene profile of the spinach-associated outbreak isolates (stx1(-) stx2(+) stx2c(+)) correlated with prophage insertions different from those in the prototypical EDL933 and Sakai reference strains (stx1(+) stx2(+) stx2c(-)). The prophage occupying the yehV chromosomal position in the spinach-associated outbreak isolates was similar to the stx1(+) EDL933 cryptic prophage V, but it lacked the stx1 gene. In EDL933, the stx2 genes are within prophage BP933-W at the wrbA chromosomal locus; this locus was unoccupied in the spinach outbreak isolates. Instead, the stx2 genes were found within a chimeric BP933-W-like prophage with a different integrase, inserted at the argW locus in the outbreak isolates. An extra set of Shiga toxin genes, stx2c, was found in the outbreak isolates within a prophage integrated at the sbcB locus. The optical maps of two additional clinical isolates from the outbreak showed a single, different prophage variation in each, suggesting that changes occurred in the source strain during the course of this widespread, multi-state outbreak.
针对2006年美国与新鲜菠菜相关的大肠杆菌O157 : H7疫情中分离出的5株具有代表性的临床、食源性和牛源分离株绘制的光学图谱显示，共有14个不同的染色体标记，这些标记定义了疫情菌株。利用454 DNA部分测序对光学图谱上的染色体标记进行了表征。这些标记包括插入、缺失、替换以及一个产生BamHI位点的简单单核苷酸多态性。与菠菜相关的疫情分离株的志贺毒素基因谱（stx1(-) stx2(+) stx2c(+)）与原型EDL933和Sakai参考菌株（stx1(+) stx2(+) stx2c(-)）中的前噬菌体插入情况不同。在与菠菜相关的疫情分离株中占据yehV染色体位置的前噬菌体与stx1(+) EDL933隐匿前噬菌体V相似，但缺少stx1基因。在EDL933中，stx2基因位于wrbA染色体位点的前噬菌体BP933-W内；在菠菜疫情分离株中该位点未被占据。相反，在疫情分离株中，stx2基因位于一个具有不同整合酶的嵌合BP933-W样前噬菌体中，插入在argW位点。在疫情分离株中，在整合于sbcB位点的前噬菌体中发现了一组额外的志贺毒素基因stx2c。此次疫情中另外两株临床分离株的光学图谱显示，每株都有一个不同的前噬菌体变异，这表明在这次广泛的多州疫情过程中，源菌株发生了变化。
