Open AccessDuplication and diversification of a unique chromosomal virulence island hosting the subtilase cytotoxin in Escherichia coli ST58
Author(s) -
Ethan R. Wyrsch,
Piklu Roy Chowdhury,
Veronica M. Jarocki,
Kate Brandis,
Steven P. Djordjevic
Publication year - 2020
Publication title -
microbial genomics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.476
H-Index - 28
ISSN - 2057-5858
DOI - 10.1099/mgen.0.000387
Subject(s) - virulence , pathogenicity island , biology , escherichia coli , operon , microbiology and biotechnology , gene , plasmid , genetics , gene duplication , horizontal gene transfer , chromosomal region , genome , chromosome
The AB 5 cytotoxins are important virulence factors in Escherichia coli . The most notable members of the AB 5 toxin families include Shiga toxin families 1 (Stx 1 ) and 2 (Stx 2 ), 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 AB 5 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 .