KPC-53, a KPC-3 variant of clinical origin associated with reduced susceptibility to ceftazidime-avibactam.

This study reports on the characterization of a Klebsiella pneumoniae clinical isolate showing a high-level resistance to ceftazidime-avibactam associated with production of KPC-53, a KPC-3 variant exhibiting a Leu167Glu168 duplication in the Ω-loop and loss of carbapenemase activity. WGS revealed the presence of two copies of blaKPC-53, located on a pKpQIL-like plasmid and on a plasmid prophage of the Siphoviridae family, respectively. Present findings provided new insights about the mechanisms of resistance to ceftazidime-avibactam.