Genome on the move: emergence of hybrid atypical enteropathogenic/enteroaggregative Escherichia coli (aEPEC/EAEC) during a diarrheal outbreak in Brazil

This study provides evidence that the high genomic plasticity of Escherichia coli has played a key role in the emergence of diarrheagenic strains harboring virulence markers from atypical enteropathogenic (aEPEC) and enteroaggregative (EAEC) E. coli, as well as strains with markers from both pathogenic groups, combined in hybrid aEPEC/EAEC strains. Phylogenetic analysis suggests that these strains share a common ancestral lineage within the ST10, from which a branch subsequently differentiated into the ST8087. The presence of mobile genetic elements shared among all strains, alongside others that are pathotype-specific, highlights the mosaic architecture of these genomes. Elucidating this evolutionary process, particularly the generation of E. coli strains with novel combinations of virulence genes, is essential for advancing our understanding of the evolution of the diarrheagenic E. coli (DEC) genome and its implications for pathogenicity.