Molecular Characterization of blaVIM-2-carrying Pseudomonas asiatica L2126: Identification of a ∼44 kb Untypable Plasmid with Intra-Genus Dissemination Potential.

Objectives: This study aims to elucidate the molecular characteristics of a bla_VIM-2-carrying Pseudomonas asiatica isolate (L2126) from China and to characterize a ∼44 kb untypable plasmid harboring bla_VIM-2. We investigated the genetic context of bla_VIM-2, assessed the associated antimicrobial resistance determinants, and explored the role of this plasmid in mediating gene dissemination.

Methods: The isolate L2126 was recovered from an intestinal colonization sample in a patient from Hangzhou, China. Species identification was confirmed by average nucleotide identity (ANI) analysis. Hybrid whole-genome sequencing was performed using Illumina short-read and Oxford Nanopore long-read platforms. Genome assembly was conducted using Unicycler and annotated with Prokka. Antimicrobial resistance genes were identified via ResFinder and CARD. The genetic context of bla_VIM-2 was delineated using IntegronFinder. Plasmid profiles were determined by S1-nuclease pulsed-field gel electrophoresis (S1-PFGE) and in silico replicon analysis.

Results: L2126 exhibited a multidrug-resistant profile with high-level resistance to carbapenems, cephalosporins, and fluoroquinolones. Genome analysis revealed 7 resistance genes, including bla_VIM-2 and sul1. Notably, bla_VIM-2 resides within a class 1 integron (intI1-attI1- bla_VIM-2-qacEΔ1-sul1) embedded in a Tn402-like platform on a ∼44 kb untypable plasmid. The adjacent tni module (tniR-tniQ-tniB-tniA) is encoded on the opposite strand, indicating that it is part of the transposition platform rather than the integron cassette array. S1-PFGE confirmed the presence of the ∼44 kb plasmid, and in silico analysis provided a schematic representation of its genetic organization. BLAST analysis demonstrated that this plasmid shares high sequence homology with a plasmid previously identified in Pseudomonas monteilii, despite the two isolates belonging to different species.

Conclusions: Our findings demonstrate that the carriage of bla_VIM-2 on a novel ∼44 kb untypable plasmid in P. asiatica L2126 could facilitate horizontal gene transfer of carbapenem resistance. The plasmid's high homology to one previously identified in P. monteilii suggests that it has the potential for intra-genus dissemination, posing a significant threat to the spread of carbapenem resistance.