Comparison of ten E. coli ST131 genomes. Escherichia coli O25b:H4-ST131

Escherichia coli of the sequence type ST131 are increasingly being reported as the emerging dominant strain type associated with extra-intestinal infections worldwide, leading to this strain type being termed a “pandemic E. coli”. Here we present data confirming that E. coli ST131 is over-represented in a collection of clinical isolates, and that there is large phenotypic variation amongst isolates. Genome sequencing of a selection of non-related clinical isolates in contrast shows almost no genomic variation between ST131 strains, and that E. coli ST131 shows evidence of a genetically monomorphic pathogen showing similar evolutionary trend to hypervirulent Clostridium difficile. This is in contrast to previous E. coli population studies performed on other pathogenic sub-types, and raises new questions in our understanding of the evolution and emergence of highly-pathogenic lineages of E. coli.