Evolution of XDR Pseudomonas aeruginosa ST463 strains with two plasmids harboring multiple antimicrobial resistance genes

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ABSTRACT The extensively drug-resistant (XDR) Pseudomonas aeruginosa ST463 strains, which co-harbor plasmid-associated metallo-β-lactamase (MBL) and bla KPC-2 genes, exhibit significant resistance and virulence, posing great clinical treatment challenges. Here, we report on three XDR P. aeruginosa ST463 strains, PA64, PA3117, and PA30, all carrying two plasmid types. One plasmid was a ~450 kb IncP-2-type megaplasmid named pPA64_1, pPA3117_1, and pPA30_1 in strains PA64, PA3117, and PA30, respectively. The other plasmid was a type I plasmid named pPA64_2, pPA3117_2, and pPA30_2 in strains PA64, PA3117, and PA30, respectively, harboring the bla KPC-2 gene in the core genetic platform IS Kpn27- bla KPC-2 -IS Kpn6 . The bla KPC-2 gene copies were associated with IS 26 -mediated inversion or duplication events. Notably, the IncP-2 megaplasmids pPA64_1, pPA3117_1, and pPA30_1 were associated with a variable ~57.3 kb Tn 1403 -like transposon named Tn 6485g , Tn 6485h , and Tn 6485f , respectively. Tn 6485g carried the MBL gene bla IMP-45, which was located in the class 1 integron In 786 , followed by an IS CR1 -associated armA module and the IS 26 -composite transposon Tn 6309 . On this basis, other IS CR1 -associated modules (IS CR1-qnrVC6 , IS CR1-bla PER-1 , and IS CR1-bla AFM-1 ) were inserted between In 786 derivatives and IS CR1-armA , resulting in a novel transposon, Tn6 485h , carrying two MBL genes, bla IMP-45 and bla AFM-1 . In contrast to Tn6 485h , Tn 6485f had another inserted copy of IS CR1-qnrVC6 . We inferred that the evolution of the Tn 1403 -like transposon might be driven by the recruitment of IS CR1 -associated antimicrobial resistance (AMR) modules under antibiotic pressure in a clinical setting.

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