Emergence of Enteroaggregative Escherichia coli within the ST131 Lineage as a Cause of Extraintestinal Infections

Escherichia coli sequence type 131 (ST131) is a major cause of urinary and bloodstream infections. Its association with extended-spectrum β-lactamases (ESBLs) significantly complicates treatment. Its best-described component is the rapidly expanding H30Rx clade, containing allele 30 of the type 1 fimbrial adhesin gene fimH. This lineage appears to have emerged in the United States and spread around the world in part due to the acquisition of the ESBL-encoding blaCTX-M-15 gene and resistance to fluoroquinolones. However, non-H30 ST131 sublineages with other acquired CTX-M-type resistance genes are also emerging. Based on whole-genome analyses, we describe here the presence of an (fimH) H27 E. coli ST131 sublineage that has recently caused an outbreak of community-acquired bacteremia and recurrent urinary tract infections (UTIs) in Denmark. This sublineage has acquired both a virulence plasmid (pAA) that defines the enteroaggregative E. coli (EAEC) diarrheagenic pathotype and multiple genes associated with extraintestinal E. coli (ExPEC); combined, these traits have made this particular ST131 sublineage successful at colonizing its human host and causing recurrent UTI. Moreover, using a historic World Health Organization (WHO) E. coli collection and publicly available genome sequences, we identified a global H27 EAEC ST131 sublineage that dates back as far as 1998. Most H27 EAEC ST131 isolates harbor pAA or pAA-like plasmids, and our analysis strongly implies a single ancestral acquisition among these isolates. These findings illustrate both the profound plasticity of this important pathogenic E. coli ST131 H27 sublineage and genetic acquisitions of EAEC-specific virulence traits that likely confer an enhanced ability to cause intestinal colonization.