Characterization of the Chromosomally Located Metallo-β-Lactamase Genes blaIMP-45 and blaVIM-2 in a Carbapenem-Resistant Pseudomonas aeruginosa Clinical Isolate.

Objective: Characterization of the multidrug resistance (MDR) region in P. aeruginosa strain PA59 revealed the presence of antibiotic resistance genes, including bla_IMP-45 and bla_VIM-2, within a complex genetic landscape of mobile genetic elements. Methods: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) strains were isolated from Shanghai Changhai Hospital. Polymerase chain reaction (PCR) was used to detect the β-lactamase genes in the isolated strains. Strains carrying two or more genes were subjected to whole-genome sequencing (WGS) and in-depth bioinformatics analysis. Results: A total of 94 CRPA strains were isolated, among which PA59 was determined to carry bla_IMP-45 and bla_VIM-2 genes. Compared with single-gene positive or other bla_IMP and bla_VIM dual-gene positive strains reported, PA59 exhibited a broader range of drug resistance. We discovered a multidrug resistant (MDR)-related region composed of various mobile elements in the PA59 chromosome. This region carried many resistance genes, including the target genes bla_IMP-45 and bla_VIM-2. By further comparing the mobile elements GI13 and Ph08, we speculated that this integron structure carrying bla_IMP-45 and bla_VIM-2 was initially integrated into the genomic island or prophage, forming a more complex genetic structure, and then further integrated into the PA59 chromosome through plasmids. Phylogenetic tree analysis showed limited sequence similarity between PA59 and other CRPA strains. Conclusions: This study identified PA59 as the first reported P. aeruginosa strain carrying both bla_IMP-45 and bla_VIM-2 on the chromosome. The assembly and annotation of the PA59 genome provide valuable insights into the genomic diversity and gene content of this clinically important pathogen, aiding the development of effective strategies against antibiotic resistance.