Tracing the evolutionary trajectory of the IncP-2 plasmid co-harboring bla IMP-45 and bla VIM-1: an outbreak of Pseudomonas aeruginosa co-producing IMP-45 and VIM-1 carbapenemases in China.

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) poses a significant global health risk, particularly for immunocompromised individuals. This study documents an outbreak of CRPA strains co-harboring bla VIM-1 and bla IMP-45 on IncP-2 plasmids in a Chinese tertiary hospital, resulting in poor outcomes for transplant patients. 17 ST313 VIM-1-IMP-45 CRPA strains were collected from transplant patients, and antibiotic susceptibility was tested via microbroth dilution. Whole genome sequencing (WGS) identified drug resistance and virulence mechanisms, analyzed ST313 P. aeruginosa phylogeny, and traced bla VIM-1 and bla IMP-45 origins. Conjugation experiments were conducted to assess the conjugative potential of the IncP-2 plasmid co-harboring bla VIM-1 and bla IMP-45. Structural and molecular docking studies explored the PBP3 (P527S) mutation's role in aztreonam resistance. From February 2022 to July 2024, 17 ST313 VIM-1-IMP-45 CRPA strains from 10 transplant patients were identified. All strains were extensively drug-resistant but sensitive to colistin and cefiderocol. WGS showed bla IMP-45 and bla VIM-1 on an IncP-2 megaplasmid. Phylogenetic analysis indicated high homology with plasmids carrying bla IMP-45. Further analysis of the genetic environment showed that the IncP-2 plasmid co-harboring bla VIM-1 and bla IMP-45 was formed by the insertion of a Tn3-family transposon carrying bla VIM-1 into the IncP-2 plasmid carrying bla IMP-45. In addition aztreonam-resistant strains (14/15) had a PBP3 (P527S) mutation, with molecular docking studies suggesting reduced aztreonam binding. This study reports a clonal outbreak of ST313 P. aeruginosa strains co-producing IMP-45 and VIM-1 carbapenemases in a tertiary hospital. The evolutionary path of the IncP-2 plasmid co-harboring bla IMP-45 and bla VIM-1 was elucidated.