Outbreak of IncX8 Plasmid–Mediated KPC-3–Producing Enterobacterales Infection, China

Carbapenem-resistant Enterobacterales (CRE) infection is highly endemic in China; Klebsiella pneumoniae carbapenemase (KPC) 2–producing CRE is the most common, whereas KPC-3–producing CRE is rare. We report an outbreak of KPC-3–producing Enterobacterales infection in China. During August 2020–June 2021, 25 bla(KPC-3)–positive Enterobacteriale isolates were detected from 24 patients in China. Whole-genome sequencing analysis revealed that the bla(KPC-3) genes were harbored by IncX8 plasmids. The outbreak involved clonal expansion of KPC-3–producing Serratia marcescens and transmission of bla(KPC-3) plasmids across different species. The bla(KPC-3) plasmids demonstrated high conjugation frequencies (10(−3) to 10(−4)). A Galleria mellonella infection model showed that 2 sequence type 65 K2 K. pneumoniae strains containing bla(KPC-3) plasmids were highly virulent. A ceftazidime/avibactam in vitro selection assay indicated that the KPC-3–producing strains can readily develop resistance. The spread of bla(KPC-3)–harboring IncX8 plasmids and these KPC-3 strains should be closely monitored in China and globally.