The Effect of β-Lactam Antibiotics on the Evolution of Ceftazidime/Avibactam and Cefiderocol Resistance in KPC-Producing Klebsiella pneumoniae.

In this study, we aimed to clarify the evolutionary trajectory of a Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-Kp) population during β-lactam antibiotic therapy. Five KPC-Kp isolates were collected from a single patient. Whole-genome sequencing and a comparative genomics analysis were performed on the isolates and all bla KPC-2 -containing plasmids to predict the population evolution process. Growth competition and experimental evolution assays were conducted to reconstruct the evolutionary trajectory of the KPC-Kp population in vitro . Five KPC-Kp isolates (KPJCL-1 to KPJCL-5) were highly homologous, and all harbor an IncFII bla KPC -containing plasmid (pJCL-1 to pJCL-5). Although the genetic structures of these plasmids were almost identical, distinct copy numbers of the bla KPC-2 gene were detected. A single copy of bla KPC-2 was presented in pJCL-1, pJCL-2, and pJCL-5, two copies of bla KPC ( bla KPC-2 and bla KPC-33 ) were presented in pJCL-3, and three copies of bla KPC-2 were presented in pJCL-4. The bla KPC-33 -harboring KPJCL-3 isolate presented resistance to ceftazidime-avibactam and cefiderocol. The bla KPC-2 multicopy strain KPJCL-4 had an elevated ceftazidime-avibactam MIC. The patient had been exposed to ceftazidime, meropenem, and moxalactam, after which KPJCL-3 and KPJCL-4 were isolated, which both showed a significant competitive advantage under antimicrobial pressure in vitro . Experimental evolution assays revealed that bla KPC-2 multicopy-containing cells were increased in the original single-copy bla KPC-2 -harboring KPJCL-2 population under selection with ceftazidime, meropenem, or moxalactam, generating a low-level ceftazidime-avibactam resistance phenotype. Moreover, bla KPC-2 mutants with a G532T substitution, G820 to C825 duplication, G532A substitution, G721 to G726 deletion, and A802 to C816 duplication increased in the bla KPC-2 multicopy-containing KPJCL-4 population, generating high-level ceftazidime-avibactam resistance and reduced cefiderocol susceptibility. Ceftazidime-avibactam and cefiderocol resistance can be selected by β-lactam antibiotics other than ceftazidime-avibactam. Notably, bla KPC-2 gene amplification and mutation are important in KPC-Kp evolution under antibiotic selection.