Genomic characterization of enterohaemolysin-encoding haemolytic Escherichia coli of animal and human origin

Abstract

Enterohaemolysin (Ehx) and alpha-haemolysin are virulence-associated factors (VAFs) causing the haemolytic phenotype in Escherichia coli . It has been shown that chromosomally and plasmid-encoded alpha-haemolysin are characteristic of specific pathotypes, virulence-associated factors and hosts. However, the prevalence of alpha- and enterohaemolysin does not overlap in the majority of pathotypes. Therefore, this study focuses on the characterization of the haemolytic E. coli population associated with multiple pathotypes in human and animal infectious diseases. Using a genomics approach, we investigated characteristic features of the enterohaemolysin-encoding strains to identify factors differentiating enterohaemolysin-positive from alpha-haemolysin-positive E. coli populations. To shed light on the functionality of Ehx subtypes, we analysed Ehx-coding genes and inferred EhxA phylogeny. The two haemolysins are associated with a different repertoire of adhesins, iron acquisition or toxin systems. Alpha-haemolysin is predominantly found in uropathogenic E. coli (UPEC) and predicted to be chromosomally encoded, or nonpathogenic and undetermined E. coli pathotypes and typically predicted to be plasmid-encoded. Enterohaemolysin is mainly associated with Shiga toxin-producing E. coli (STEC) and enterohaemorrhagic E. coli (EHEC) and predicted to be plasmid-encoded. Both types of haemolysin are found in atypical enteropathogenic E. coli (aEPEC). Moreover, we identified a new EhxA subtype present exclusively in genomes with VAFs characteristic of nonpathogenic E. coli . This study reveals a complex relationship between haemolytic E. coli of diverse pathotypes, providing a framework for understanding the potential role of haemolysin in pathogenesis.

Molecular and Genomic Analysis of the Virulence Factors and Potential Transmission of Hybrid Enteropathogenic and Enterotoxigenic Escherichia coli (EPEC/ETEC) Strains Isolated in South Korea

“…In addition, espC and espP , the serine protease autotransporters of Enterobacteriaceae, have been reported to play a role in regulating pore formation and cytotoxicity mediated by the TTSS during EPEC or EHEC infection [ 42 , 43 ]. In addition to this, α-hemolysin is a component of an operon that contains four genes: hlyA (which encodes the functional toxin HlyA), hlyC (which is responsible for the post-translational modification of HlyA), hlyB , and hlyD (which are responsible for the transport of HlyA across the inner membrane) [ 44 , 45 ]. Previous research [ 46 ] has demonstrated that a pore-forming cytolysin functions as a virulence factor in intestinal and extraintestinal pathogenic E .…”

adhesiomeR: a tool for Escherichia coli adhesin classification and analysis

“…However, the role of adhesins as VAFs has been studied for only fraction of them and as a result, many adhesin sequences are not present in available databases. In our previous studies of hemolytic E. coli we found that the repertoire of specific adhesin genes co-occurred in E. coli strains harbouring either alpha-or entero-hemolysin [18]. Furthermore, specific repertoires were associated with alpha-hemolytic E. coli isolated from different hosts (humans or farm animals) [19].…”

“…Each subplot corresponds to one of 19 colonization factors investigated by von Mentzer et al and shows in how many strains adhesiomeR identified given system as present, partial or absent compared to experimental analyses nonpathogenic and unknown (NA). This procedure was based on the presence and/or absence of characteristic virulence factors of these pathotypes (Table S3-4) [18,19]. Additionally, we included 354 ETEC genomes from a paper by Von Mentzer et al [29] and 573 APEC genomes from multiple studies (Table S5).…”