Genomic epidemiology reveals geographical clustering of multidrug-resistant <i>Escherichia coli</i> ST131 associated with bacteraemia in Wales

<p dir="ltr">Antibiotic resistance is a significant global public health concern. Uropathogenic <i>Escherichia coli</i> sequence type (ST)131, a widely prevalent multidrug-resistant clone, is frequently associated with bacteraemia. This study investigates third-generation cephalosporin resistance in bloodstream infections caused by <i>E. coli</i> ST131. From 2013-2014 blood culture surveillance in Wales, 142 <i>E. coli</i> ST131 genomes were studied alongside global data. All three major ST131 clades were represented across Wales, with clade C/<i>H</i>30 predominant (<i>n</i> = 102/142, 71.8%). Consistent with global findings, Welsh strains of clade C/<i>H</i>30 contain <i>β</i>-lactamase genes from the <i>bla</i>_CTX-M-1 group (<i>n</i> = 65/102, 63.7%), which confer resistance to third-generation cephalosporins. Most Welsh clade C/<i>H</i>30 genomes belonged to sub-clade C2/<i>H</i>30Rx (58.3%). A Wales-specific sub-lineage, named GB-WLS.C2, diverged around 1996-2000. An introduction to North Wales around 2002 led to a localised cluster by 2009, depicting limited genomic diversity within North Wales. This investigation emphasises the value of genomic epidemiology, allowing the detection of genetically similar strains in local areas, enabling targeted and timely public health interventions.</p>