Genomic characterization of the multidrug-resistant IncP-2 plasmid pPAMS in a clinical isolate Pseudomonas aeruginosa

The multidrug-resistant Pseudomonas aeruginosa represents a significant global public health threat, particularly strains associated with IncP-2 plasmids, which pose considerable challenges for clinical treatment. In this study, we conducted a comprehensive genomic characterization of the multidrug-resistant IncP-2 plasmid pPAMS, highlighting genomic diversity and molecular evolution of IncP-2 plasmids. We identified an extensively drug-resistant P. aeruginosa strain, designated PAMS, which harbors an IncP-2 plasmid, referred to as pPAMS (448,129 bp). This plasmid contains 15 resistance genes, distribute in two multidrug resistance integrons (In786 and In1237), a cluster of RND efflux pump genes (tmexCD3-toprJ3), and a tetracycline resistance gene [tetA(C)]. Comparative analysis revealed that pPAMS and 20 megaplasmids shared high nucleotide identity and coverage in the NCBI database. The resistance region of pPAMS exhibited high similarity to previously reported plasmids pPA1609-475 and pBM413, sharing the same genetic architecture, with the exception of the genetic unit IS26-tetR(C)-tetA(C)-IS26. Notably, pPAMS possesses a unique variable region of approximately 20 kbp, contains the glycoside hydrolase 25, which may be associated with the microbial competition. Conjugation assays and antimicrobial susceptibility testing demonstrated that pPAMS could be transferred to P. aeruginosa PAO1, resulting in a multidrug-resistant phenotype. Additionally, virulence assays indicated that plasmid pPAMS could reduce bacterial pathogenicity, suggesting that it may repress the expression of virulence factors. This study provides a comprehensive genetic analysis of the multidrug-resistant IncP-2 plasmid pPAMS. Our findings offer valuable insights into the genomic diversity and molecular evolution of IncP-2 plasmids.