The AB5 cytotoxins are important virulence factors in Escherichia coli . The most notable members of the AB5 toxin families include Shiga toxin families 1 (Stx1) and 2 (Stx2), which are associated with enterohaemorrhagic E. coli infections causing haemolytic uraemic syndrome and haemorrhagic colitis. The subAB toxins are the newest and least well understood members of the AB5 toxin gene family. The subtilase toxin genes are divided into a plasmid-based variant, subAB1, originally described in enterohaemorrhagic E. coli O113:H21, and distinct chromosomal variants, subAB2, that reside in pathogenicity islands encoding additional virulence effectors. Previously we identified a chromosomal subAB2 operon within an E. coli ST58 strain IBS28 (ONT:H25) taken from a wild ibis nest at an inland wetland in New South Wales, Australia. Here we show the subAB2 toxin operon comprised part of a 140 kb tRNA–Phe chromosomal island that co-hosted tia, encoding an outer-membrane protein that confers an adherence and invasion phenotype and additional virulence and accessory genetic content that potentially originated from known virulence island SE-PAI. This island shared a common evolutionary history with a secondary 90 kb tRNA–Phe pathogenicity island that was presumably generated via a duplication event. IBS28 is closely related [200 single-nucleotide polymorphisms (SNPs)] to four North American ST58 strains. The close relationship between North American isolates of ST58 and IBS28 was further supported by the identification of the only copy of a unique variant of IS26 within the O-antigen gene cluster. Strain ISB28 may be a historically important E. coli ST58 genome sequence hosting a progenitor pathogenicity island encoding subAB.

中文翻译：

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大肠杆菌ST58中具有枯草蛋白酶细胞毒素的独特染色体毒力岛的复制和多样化。

AB 5细胞毒素是大肠杆菌中重要的毒力因子。AB 5毒素家族中最著名的成员包括志贺毒素家族1（Stx 1）和2（Stx 2），它们与引起出血性尿毒症和出血性结肠炎的肠出血性大肠杆菌感染有关。subAB毒素是AB 5毒素基因家族中最新的，鲜为人知的成员。枯草杆菌蛋白酶毒素基因分为最初在肠出血性大肠杆菌O113：H21中描述的基于质粒的变异体subAB1和不同的染色体变异体subAB2 ，位于编码其他毒力效应子的致病岛中。以前，我们在大肠杆菌ST58菌株IBS28（ONT：H25）中鉴定了一个染色体subAB2操纵子，该菌株取自澳大利亚新南威尔士州内陆湿地的野生宜必思巢。在这里，我们显示了subAB2毒素操纵子包含140 kb tRNA–Phe染色体岛的一部分，该岛共同托管着tia ，编码一种外膜蛋白，该蛋白赋予粘附和侵袭表型以及可能源自已知毒力岛SE-PAI的其他毒力和辅助遗传成分。该岛与第二个90 kb tRNA–Phe致病岛具有共同的进化史，该岛可能是通过复制事件产生的。IBS28与四种北美ST58菌株密切相关[200个单核苷酸多态性（SNP）]。通过鉴定O-抗原基因簇内IS26独特变体的唯一拷贝，进一步支持了北美ST58和IBS28分离株之间的密切关系。菌株ISB28可能是具有重要历史意义的大肠杆菌ST58基因组序列，其宿主编码subAB的祖先致病岛 。