The blaKPC-249-mediated mechanism drives the transition of ST463 Pseudomonas aeruginosa from Ceftazidime-Avibactam sensitivity to resistance during clinical treatment

Introduction Ceftazidime-avibactam represents a crucial therapeutic option for managing infections attributable to carbapenem-resistant P. aeruginosa . Nonetheless, the emergence of resistance to ceftazidime-avibactam in P. aeruginosa presents a significant challenge for clinical anti-infective therapy. This study primarily elucidates the mechanisms by which P. aeruginosa transitions from drug sensitivity to resistance during ceftazidime-avibactam treatment, ultimately resulting in therapeutic failure. Methods The susceptibility testing was performed using the broth microdilution method, conjugation experiment was performed via the filter mating method, the genetic surroundings of bla KPC-249 and comparison of plasmids structures was performed using short/long-read genome sequencing and analysis method, the resistance of transconjugant carried the bla KPC-249 to ceftazidime-avibactam was performed via molecular cloning method. Results For P. aeruginosa isolates from a patient, the minimum inhibitory concentrations (MICs) of ceftazidime-avibactam (CAZ-AVI) were determined as follows: isolates from sputum and bronchoalveolar lavage fluid both exhibited an MIC of 2 mg/L without blaKPC. In comparison, the blood-isolated strain P. aeruginosa PAE045 showed a significantly elevated MIC of >128 mg/L against CAZ-AVI. Plasmid conjugation experiments results demonstrated that the plasmid harboring the bla KPC-249 gene could be successfully transferred to the recipient strain PAO1 rifR (rifampicin-resistant P. aeruginosa PAO1). Third-generation sequencing results revealed that the bla KPC-249 gene was located on a plasmid with an approximate size of 37 kb. Compared with the wild-type e bla KPC-2 gene, the bla KPC-249 gene had two additional amino acid residues in its encoded protein: threonine (Thr, T) at position 182 and serine (Ser, S) at position 183. Furthermore, the upstream and downstream regions of the bla KPC-249 gene were flanked by the insertion sequences ISK pn6 and ISK pn27 , respectively. Discussion These mobile genetic elements may play a role in the capture and dissemination of the bla KPC-249 gene. The bla KPC-249 gene is identified as a novel mutant variant of the bla KPC gene family, which mediates the resistance of P. aeruginosa to the antimicrobial agent ceftazidime-avibactam.