Uropathogenic Escherichia coli ST127 is a recently emerged clone that is reported to cause a small, but significant, proportion of urinary tract infections. Paradoxically, the low prevalence of ST127 in most published studies is also accompanied by a virulence potential significantly higher than many of the leading uropathogenic lineages (cf. ST131) using an established uropathogenic PCR virulence assay. This study explores the contradictory nature of these findings by evaluating some of the major aspects concerning the diagnosis, genomic repertoire and pathogenicity of strains of this sequence type in relation to its recorded prevalence. Analysis was performed to determine if UPEC ST127 had a propensity towards a certain group of individuals, was underrepresented due to diagnostic criterion or possessed a novel polymicrobial aetiology concealing the true prevalence of this clone in the general population. To enable evaluation, rapid and robust PCR tests were designed for identifying this sequence type within a collection of 475 urine isolates collected from clinical laboratories. Specimens underwent genomic examination and were subject to three virulence assays in an attempt to validate results and establish the true value of these assays. Further examination to determine the virulence for members of this sequence type was performed using a bladder cell culture infection model. Results suggest that the presence of a highly motile phenotype may dictate the prevalence of UPEC in the population and the ability to invade the uroepithelium. A widespread frameshift mutation present in the flhB gene in the majority of ST127 isolates suggests that motility may be supressed in this lineage and the reason for the reported low prevalence of ST127. This report supports the long suspected, but never proved, notion that bacterial motility is one of the most important virulence traits relating to the pathogenicity of Escherichia coli within the urinary tract.

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