Activity of Imipenem-Relebactam against Carbapenem-Resistant Escherichia coliIsolates from the United States in Relation to Clonal Background, Resistance Genes, Coresistance, and Region

Imipenem-relebactam (I-R) is a recently developed carbapenem–beta-lactamase inhibitor combination agent that can overcome carbapenem resistance, which has now emerged in Escherichia coli, including sequence type 131 (ST131) and its fluoroquinolone-resistant H30R subclone, the leading cause of extraintestinal E. coliinfections globally. To clarify the likely utility of I-R for carbapenem-resistant (CR) E. coliinfections in the United States, we characterized 203 recent CR clinical E. coliisolates from across the United States (years 2002 to 2017) for phylogroup, clonal group (including ST131, H30R, and the CTX-M-15-associated H30Rx subset within H30R), relevant beta-lactamase genes, and broth microdilution MICs for I-R and 11 comparator agents.