The Escherichia coli sequence type (ST) 131 C2/H30Rx clade with the blaCTX-M-15 gene had been most responsible for the global dissemination of extended-spectrum β-lactamase (ESBL)-producing E. coli. ST131 C1/H30R with blaCTX-M-27 emerged among ESBL-producing E. coli in Japan during the late 2000s. To investigate the possible expansion of a single clade, we performed whole-genome sequencing for 43 Japan and 10 global ST131 isolates with blaCTX-M-27 (n = 16), blaCTX-M-14 (n = 16), blaCTX-M-15 (n = 13), and others (n = 8). We also included 8 ST131 genomes available in public databases. Core genome-based analysis of 61 isolates showed that ST131 with blaCTX-M-27 from 5 countries formed a distinct cluster within the C1/H30R clade, named C1-M27 clade. Accessory genome analysis identified a unique prophage-like region, supporting C1-M27 as a distinct clade. Our findings indicate that the increase of ESBL-producing E. coli in Japan is due mainly to emergence of the C1-M27 clade.
Keywords: CTX-M-27; E. coli; Escherichia coli; MLST; antimicrobial resistance; bacteria; bla gene; clones; high-throughput DNA sequencing; molecular epidemiology; multilocus sequence typing; β-lactamases.