A Novel pAA Virulence Plasmid Encoding Toxins and Two Distinct Variants of the Fimbriae of Enteroaggregative Escherichia coli

Abstract

Enteroaggregative Escherichia coli (EAEC) is an increasingly recognized pathogen associated with acute and persistent diarrhea worldwide. While EAEC strains are considered highly heterogeneous, aggregative adherence fimbriae (AAFs) are thought to play a pivotal role in pathogenicity by facilitating adherence to the intestinal mucosa. In this study, we optimized an existing multiplex PCR to target all known AAF variants, which are distinguished by differences in their pilin subunits. We applied the assay on a collection of 162 clinical Danish EAEC strains and interestingly found six, by SNP analysis phylogenetically distinct, strains harboring the major pilin subunits from both AAF/III and AAF/V. Whole-genome and plasmid sequencing revealed that in these six strains the agg3A and agg5A genes were located on a novel pAA plasmid variant. Moreover, the plasmid also encoded several other virulence genes including some not previously found on pAA plasmids. Thus, this plasmid endows the host strains with a remarkably high number of EAEC associated virulence genes hereby likely promoting strain pathogenicity.

Genetic and Virulence Profiles of Enteroaggregative Escherichia coli (EAEC) Isolated From Deployed Military Personnel (DMP) With Travelers' Diarrhea

“…The operons for the known EAEC AAF variants I-V were identified in 35/56 of the strains in the collection ( Table 1). The sequence for one strain (E11V1A) contained the genes for both agg3A (entire agg3 operon was present) and agg5A, a phenomenon described previously (Jonsson et al, 2017), although in E11V1A there was only a single agg3B gene. Most of the isolates also had the operons for E. coli common pilus (Ecp), type I fimbriae, long polar fimbriae type 1 or 2, and/or Pil ( Table 2).…”

“…There are five different types of AA fimbriae (AAF), designated AAF/I-V, that are specific to EAEC (Jonsson et al, 2015). The genes for the AAF are located on the plasmid of aggregative adherence (pAA), and except for one reported strain (Jonsson et al, 2017), EAEC only encode one of the five AAF types. In the prototype strain 042 (AAF/II), proper display of fimbriae on the bacterial surface is dependent on the dispersin protein, Aap (Sheikh et al, 2002).…”

Benchmarking Long-Read Assemblers for Genomic Analyses of Bacterial Pathogens Using Oxford Nanopore Sequencing

“…Previous studies have demonstrated the effectiveness of Oxford Nanopore sequencing in the rapid identification of virulence genes in bacterial pathogens [22][23][24]. The numbers of virulence genes identified in all assemblies of mediocre-quality reads of each strain were not significantly different (p > 0.05) from those in the reference genome (Table 4).…”

Analysis of the Virulence Profile and Phenotypic Features of Typical and Atypical Enteroaggregative Escherichia coli (EAEC) Isolated From Diarrheal Patients in Brazil

“…However, the occurrence of Brazilian EAEC isolates harboring the agg5A, alone or concomitantly with agg3A, is described for the first time in this study. A study performed with Danish EAEC isolates identified six harboring the major pilin subunits from both AAF/III (agg3A) and AAF/V (agg5A), with these genes located in a novel pAA variant (Jønsson et al, 2017b).…”