The complete nucleotide sequence of an IncP-2 megaplasmid unveils a mosaic architecture comprising a putative novel blaVIM-2-harbouring transposon in Pseudomonas aeruginosa

Objectives: In Pseudomonas aeruginosa, blaVIM-2 has been mostly associated with a chromosomal location and rarely with a plasmid backbone. Until now, only three complete blaVIM-2-carrying plasmid sequences have been described in this species. Here we explore the modular structure of pJB37, the first blaVIM-2-carrying megaplasmid described in P. aeruginosa. Methods: The complete nucleotide sequence of plasmid pJB37 was determined with an Illumina HiSeq, with de novo assembly by SPAdes, annotation by RAST and searching for antimicrobial resistance genes and virulence factors. Conjugation assays were conducted. Results: Megaplasmid pJB37 (464 804 bp long and GC content of 57.2%) comprised: an IncP-2 repA-oriV-parAB region; a conjugative transfer region (traF, traG, virD2 and trbBCDEJLFGI genes); Tn6356, a new putative blaVIM-2-carrying transposon; heavy metal (mercury and tellurite) resistance operons; and an arsenal of virulence genes. Plasmid pJB37 was transferable by conjugation to a spontaneous rifampicin-resistant mutant of P. aeruginosa PAO1. Here, a blaVIM-2-harbouring In58 integron was associated with a new complex transposable structure, herein named Tn6356, suggesting that In58 was most likely acquired by insertion of this element. Conclusions: The mosaic arrangement exhibited by the pJB37 IncP-2 megaplasmid, which highlights the vast assembly potential of distinct genetic elements in a Pseudomonas widespread plasmid platform, gives new insights into bacterial adaptation and evolution.