An Investigation of the Diversity of Strains of Enteroaggregative Escherichia coli Isolated from Cases Associated with a Large Multi-Pathogen Foodborne Outbreak in the UK

Abstract

Following a large outbreak of foodborne gastrointestinal (GI) disease, a multiplex PCR approach was used retrospectively to investigate faecal specimens from 88 of the 413 reported cases. Gene targets from a range of bacterial GI pathogens were detected, including Salmonella species, Shigella species and Shiga toxin-producing Escherichia coli, with the majority (75%) of faecal specimens being PCR positive for aggR associated with the Enteroaggregative E. coli (EAEC) group. The 20 isolates of EAEC recovered from the outbreak specimens exhibited a range of serotypes, the most frequent being O104:H4 and O131:H27. None of the EAEC isolates had the Shiga toxin (stx) genes. Multilocus sequence typing and single nucleotide polymorphism analysis of the core genome confirmed the diverse phylogeny of the strains. The analysis also revealed a close phylogenetic relationship between the EAEC O104:H4 strains in this outbreak and the strain of E. coli O104:H4 associated with a large outbreak of haemolytic ureamic syndrome in Germany in 2011. Further analysis of the EAEC plasmids, encoding the key enteroaggregative virulence genes, showed diversity with respect to FIB/FII type, gene content and genomic architecture. Known EAEC virulence genes, such as aggR, aat and aap, were present in all but one of the strains. A variety of fimbrial genes were observed, including genes encoding all five known fimbrial types, AAF/1 to AAF/V. The AAI operon was present in its entirety in 15 of the EAEC strains, absent in three and present, but incomplete, in two isolates. EAEC is known to be a diverse pathotype and this study demonstrates that a high level of diversity in strains recovered from cases associated with a single outbreak. Although the EAEC in this study did not carry the stx genes, this outbreak provides further evidence of the pathogenic potential of the EAEC O104:H4 serotype.

Distribution of Virulence Genes, Enterotoxin and Biofilm Formation Among Enteroaggregative Escherichia Coli (EAEC) Strains Isolated From Stools of Children With Diarrhea in South East Iran

“…In the present study, which was carried out for the first time in south east Iran, we demonstrated the importance of specific virulence genes in the biofilm formation of EAEC isolates. The rate of EAEC infection, in our case, was similar with reports from other parts of Iran (23,24). Indeed, the varying presence of the different virulence factors indicates heterogeneity of the EAEC isolates.…”

“…The EAEC strains are heterogeneous, both with respect to symptoms developed by infected hosts and with respect to virulence genes (24). In the present study, which was carried out for the first time in south east Iran, we demonstrated the importance of specific virulence genes in the biofilm formation of EAEC isolates.…”

Novel Aggregative Adherence Fimbria Variant of Enteroaggregative Escherichia coli

“…PCR assay with E coli clinical isolate C338-14 and BLAST analysis revealed an uncharacterized gene, agg5A, whose sequence has been deposited in GenBank (AB571097, AB571098) and which was mentioned in three recent studies (27,41,42). However, as of this writing no experimental characterization of this gene is available.…”

Public Health Investigation of Two Outbreaks of Shiga Toxin-Producing Escherichia coli O157 Associated with Consumption of Watercress

“…These typing schemes are instrumental in facilitating both the detection and investigation of outbreaks (4)(5)(6). Recently, whole-genome sequencing (WGS) has also been evaluated at PHE for its utility in informing outbreak investigation and surveillance of gastrointestinal disease (7)(8)(9).…”