Pseudomonas putida group species serve as reservoirs of conjugative plasmids disseminating Tn402-like class 1 integrons carrying blaVIM-2 metallo-β-lactamase genes

Abstract

The Pseudomonas putida group (P. putida G) is composed of at least 21 species associated to a wide range of environments, including the clinical setting. Here, we characterized 13 carbapenem-resistant P. putida G clinical isolates carrying blaVIM-2 from different hospitals of Argentina. Multilocus sequencing (MLSA) and phylogenetic analyses based on the 16S rDNA, gyrB and rpoD sequences comparison allowed us to assign them to 7 well-differentiated species. Sequencing analysis revealed that blaVIM-2 genes were carried in these isolates by three different class 1 integrons (In41, In899 and In528) embedded into Tn402-like transposons. Those harboring In41 and In899 were designated Tn6335 and Tn6336, respectively, with the former found among 10 isolates. Both encompassed complete transposition modules and inverted repeats boundaries characteristic of the Tn5053/Tn402 family, whereas the third, bearing In528, exhibited a defective tni module. Tn6335 and Tn6336 were located in conjugative pLD209-type plasmids in P. asiatica, P. juntendi, P. putida G/II, and P. putida G/V isolates, and could be mobilized to Escherichia coli and P. aeruginosa indicating a relevant mechanism of blaVIM-2 dissemination. In other P. asiatica and P. putida G/II isolates, Tn6335 was found inserted into the Tn21 subgroup transposons-res region, indicating capability for intragenomic mobilization and further dissemination associated to Tn3 family transposons. The Tn402-like defective element was also found inserted into the res region of another Tn3 family transposon in a P. monteilii isolate, but in an atypical orientation. Overall findings shed light on the mechanisms by which resistance genes move through environmental and opportunist Pseudomonas species.