Genetic and phenotypic analysis of the virulence plasmid of a non-Shigatoxigenic enteroaggregative Escherichia coli O104:H4 outbreak strain

Whelan, R, Cyganek, M, Oxley, CL ORCID: https://orcid.org/0009-0006-4715-8528, Dickins, B ORCID: https://orcid.org/0000-0002-0866-6232, Thomas, JC ORCID: https://orcid.org/0000-0002-1599-9123 and McVicker, G ORCID: https://orcid.org/0000-0002-6967-5968, 2025. Genetic and phenotypic analysis of the virulence plasmid of a non-Shigatoxigenic enteroaggregative Escherichia coli O104:H4 outbreak strain. Microbiology, 171 (3): 001550. ISSN 1350-0872

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Abstract

Enteroaggregative Escherichia coli O104:H4 is best known for causing a worldwide outbreak in 2011 due to acquisition of a Shiga-like toxin alongside traditional enteroaggregative virulence traits; however, whilst the 2011 outbreak strain has been well-studied, the virulence plasmid of O104:H4 has been subjected to far less experimental analysis. In this paper, we analyse the genetic and phenotypic contribution of the pAA virulence plasmid to a non-Shigatoxigenic O104:H4 strain (1070/13) that was nonetheless implicated in a substantial UK outbreak in 2013. We find that pAA1070 is 99.95% identical across 88% of the plasmid sequence to pTY2 from the 2011 outbreak strain and has a copy number of approximately 2-3 plasmid molecules per chromosome. We demonstrate that pAA1070 carries a functional CcdAB plasmid addiction system that only marginally impacts its stability under the conditions tested. None of the other toxin-antitoxin systems encoded by the plasmid appear to be functional, though we note a surprisingly high stability of the plasmid in vitro regardless. We demonstrate the expected contribution of pAA1070 to intestinal cell adhesion but find that it does not contribute to biofilm formation. When assessing the impact of pAA1070 on motility, we discovered a region of the O104:H4 chromosome that can be excised, abolishing motility via truncation of the fliR gene. Ultimately this work demonstrates the importance of mobile genetic elements to enteroaggregative E. coli as a pathovar in its own right and highlights the complexity but necessity of experimentally characterising genuine outbreak strains rather than laboratory strains in order to understand virulence phenotypes.

Item Type:	Journal article
Publication Title:	Microbiology
Creators:	Whelan, R., Cyganek, M., Oxley, C.L., Dickins, B., Thomas, J.C. and McVicker, G.
Publisher:	Microbiology Society
Date:	27 March 2025
Volume:	171
Number:	3
ISSN:	1350-0872
Identifiers:	Number Type 2412783 Other 10.1099/mic.0.001550 DOI
Rights:	© 2025 the authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License. This article was made open access via a Publish and Read agreement between the Microbiology Society and the corresponding author’s institution.
Divisions:	Schools > School of Science and Technology
Record created by:	Laura Borcherds
Date Added:	21 Mar 2025 10:48
Last Modified:	10 Sep 2025 09:27
URI:	https://irep.ntu.ac.uk/id/eprint/53277

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