Evolution of ceftazidime-avibactam resistance driven by mutations in double-copy blaKPC-2 to blaKPC-189 during treatment of ST11 carbapenem-resistant Klebsiella pneumoniae.

UNLABELLED: Klebsiella pneumoniae carbapenemase (KPC) variants can contribute to resistance to ceftazidime-avibactam (CZA) in Klebsiella pneumoniae (KP). However, two-copy KPC variant-mediated resistance to CZA has rarely been reported to date. Here, we aimed to clarify the evolutionary trajectory of CZA resistance driven by mutations in double-copy blaKPC-2 to blaKPC-189 carried by the tandem core structure (ISKpn6-blaKPC-ISKpn27-tnpR-IS26) during treatment of ST11 carbapenem-resistant K. pneumoniae (CRKP). The CZA-resistant KP strain carried double-copy blaKPC-189, a variant with alanine-threonine and aspartate-tyrosine substitutions at Ambler amino acid positions 172 (A172T) and 179 (D179Y) of blaKPC-2. Clone experiments confirmed that, compared with that of the wild-type blaKPC-2 clone strain, the minimum inhibitory concentration of CZA increased 16-fold in the blaKPC-189-mutant strain. Furthermore, protein structure analysis revealed the A172T and D179Y mutations of blaKPC-189 can have a direct effect on the binding affinity of CAZ and AVI for KPC. Sequence comparison revealed that blaKPC-189 was mutated in a double-copy format upon CZA exposure, which was carried by the IS26-mediated tandem core structure ISKpn27-blaKPC-ISKpn6. This tandem core structure apparently evolves in vivo during infection, although not by self-transferring, and multiple ISKpn27-blaKPC-ISKpn6 copy numbers could mediate transferable CZA resistance upon mobilization. In addition, compared with the wild-type blaKPC-2 gene, the blaKPC-189 gene had no fitness cost. In summary, our study highlighted the emergence of CZA-resistant blaKPC-189 variants in the ST11 clone and the presence of a double-copy blaKPC-189 in the IncFII-type plasmid, which is carried by a tandem core structure (IS26-ISKpn6-blaKPC-189-ISKpn27-tnpR-IS26).

IMPORTANCE

To date, ceftazidime-avibactam (CZA) resistance caused by double-copy Klebsiella pneumoniae carbapenemase (KPC) variants has not been elucidated. The multicopy forms of carbapenem resistance genes carried by the same plasmid are relatively rare in most carbapenem-resistant Enterobacteriaceae. In this study, we elucidate the evolutionary trajectory of CZA resistance in ST11 carbapenem-resistant K. pneumoniae harboring a double-copy blaKPC and provide new insights into the mechanisms of acquired resistance to CZA.