Volume 4, Issue 6
The Escherichia coli sequence type 131 (ST131) clone is notorious for extraintestinal infections, fluoroquinolone resistance, and extended-spectrum beta-lactamase (ESBL) production, attributable to a CTX-M-15-encoding mobile element. Here, we applied pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing to reconstruct the evolutionary history of the ST131 clone. PFGE-based cluster analyses suggested that both fluoroquinolone resistance and ESBL production had been acquired by multiple ST131 sublineages through independent genetic events. In contrast, the more robust whole-genome-sequence-based phylogenomic analysis revealed that fluoroquinolone resistance was confined almost entirely to a single, rapidly expanding ST131 subclone, designated H30-R. Strikingly, 91% of the CTX-M-15-producing isolates also belonged to a single, well-defined clade nested within H30-R, which was namedH30-Rx due to its more extensive resistance. Despite its tight clonal relationship with H30Rx, the CTX-M-15 mobile element was inserted variably in plasmid and chromosomal locations within the H30-Rx genome. Screening of a large collection of recent clinical E. coli isolates both confirmed the global clonal expansion of H30-Rx and revealed its disproportionate association with sepsis (relative risk, 7.5; P < 0.001). Together, these results suggest that the high prevalence of CTX-M-15 production among ST131 isolates is due primarily to the expansion of a single, highly virulent subclone, H30-Rx.
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Price, L.B., Johnson, J.R., Aziz, M., Clabots, C., Johnston, B., Tchesnokova, V., Nordstrom, L., Billig, M., Chattopadhyay, S., Stegger, M., Andersen, P.S., Pearson, T., Riddell, K., Rogers, P., Scholes, D., Kahl, B., Keim, P., Sokurenko, E.V. (2013). The epidemic of extended-spectrum-β-lactamase-producing Escherichia coli ST131 is driven by a single highly pathogenic subclone, H30-Rx. mBio 4(6):e00377-13.