Genomic characterization of ceftazidime/avibactam-resistant Klebsiella pneumoniae: a retrospective analysis on clinical isolates from an Italian transplant unit

Introduction Klebsiella pneumoniae infections are a significant healthcare concern due to advancing antimicrobial resistance rates and virulence genes’ detection. Specifically, ceftazidime/avibactam resistance is increasingly diffused among K. pneumoniae clinical isolates, limiting therapeutic choices and complicating patients’ outcomes. Some authors documented the simultaneous presence of ceftazidime/avibactam resistance markers and specific virulence genes. According to these premises, we characterized ceftazidime/avibactam-resistant K. pneumoniae strains, exploring their diffusion at the Mediterranean Institute for Transplants and Highly Specialized Therapies (ISMETT) of Palermo, Italy. Materials and methods A total of 14 ceftazidime/avibactam-resistant strains were retrospectively analyzed using whole-genome sequencing and Sanger validation. Results Most strains belonged to ST101 and carried bla KPC-31 , bla KPC-3 , or bla KPC-34 genes, often with resistance-associated mutations. The analysed strains revealed multidrug resistance, frequent outer membrane protein alterations, and a significant spectrum of virulence genes. Additionally, plasmid analysis revealed sequence type–specific replicons potentially involved in gene dissemination. Discussion These findings highlight a convergence of resistance and virulence traits in high-risk K. pneumoniae clones, enhancing the importance of MDR pathogens’ genomic surveillance in critical healthcare settings.