Characterization of blaKPC-2 and blaNDM-1 Plasmids of a K. pneumoniae ST11 Outbreak Clone

The most common resistance mechanism to carbapenems is the production of carbapenemases. In 2021, the Pan American Health Organization warned of the emergence and increase in new carbapenemase combinations in <i>Enterobacterales</i> in Latin America. In this study, we characterized four <i>Klebsiella pneumoniae</i> isolates harboring <i>bla</i>_KPC and <i>bla</i>_NDM from an outbreak during the COVID-19 pandemic in a Brazilian hospital. We assessed their plasmids' transference ability, fitness effects, and relative copy number in different hosts. The <i>K. pneumoniae</i> BHKPC93 and BHKPC104 strains were selected for whole genome sequencing (WGS) based on their pulsed-field gel electrophoresis profile. The WGS revealed that both isolates belong to ST11, and 20 resistance genes were identified in each isolate, including <i>bla</i>_KPC-2 and <i>bla</i>_NDM-1. The <i>bla</i>_KPC gene was present on a ~56 Kbp IncN plasmid and the <i>bla</i>_NDM-1 gene on a ~102 Kbp IncC plasmid, along with five other resistance genes. Although the <i>bla</i>_NDM plasmid contained genes for conjugational transfer, only the <i>bla</i>_KPC plasmid conjugated to <i>E. coli</i> J53, without apparent fitness effects. The minimum inhibitory concentrations (MICs) of meropenem/imipenem against BHKPC93 and BHKPC104 were 128/64 and 256/128 mg/L, respectively. Although the meropenem and imipenem MICs against <i>E. coli</i> J53 transconjugants carrying the <i>bla</i>_KPC gene were 2 mg/L, this was a substantial increment in the MIC relative to the original J53 strain. The <i>bla</i>_KPC plasmid copy number was higher in <i>K. pneumoniae</i> BHKPC93 and BHKPC104 than in <i>E. coli</i> and higher than that of the <i>bla</i>_NDM plasmids. In conclusion, two ST11 <i>K. pneumoniae</i> isolates that were part of a hospital outbreak co-harbored <i>bla</i>_KPC-2 and <i>bla</i>_NDM-1. The <i>bla</i>_KPC-harboring IncN plasmid has been circulating in this hospital since at least 2015, and its high copy number might have contributed to the conjugative transfer of this particular plasmid to an <i>E. coli</i> host. The observation that the <i>bla</i>_KPC-containing plasmid had a lower copy number in this <i>E. coli</i> strain may explain why this plasmid did not confer phenotypic resistance against meropenem and imipenem.