Tn6249, a New Tn6162Transposon Derivative Carrying a Double-Integron Platform and Involved with Acquisition of theblaVIM-1Metallo-β-Lactamase Gene in Pseudomonas aeruginosa

Abstract

ABSTRACTThe In70.2 integron platform appears to be a conserved structure involved in the dissemination of theblaVIM-1metallo-β-lactamase gene inPseudomonas aeruginosa. The genetic context of the In70.2 integron platform fromP. aeruginosaVR-143/97, the VIM-1-producing index strain isolated in Italy in 1997, was fully characterized by a next-generation sequencing approach refined by conventional sequencing. The In70.2 integron platform from VR-143/97 was found to be associated with a defective Tn402-like transposon inserted into theurf2gene of a Tn3family transposon of an original structure, named Tn6249, which also carried a partially deletedmeroperon and an In90 integron platform in a tail-to-tail orientation. Tn6249was inserted into a PACS171b-like genomic island, which was in turn inserted into theendAgene of thePseudomonaschromosomal backbone. Tn6249showed a similar structure and a conserved location with respect to that of Tn6060, a Tn3family transposon associated with In70.2 and carrying a double-integron platform, which was detected in a VIM-1-producingP. aeruginosastrain isolated in Australia in 2008. Both Tn6249and Tn6060are apparently derived from Tn6162, a mercury resistance transposon carrying an integron platform, which was found inP. aeruginosaisolates from different geographic locations. The conservation of the genetic context of Tn6249and Tn6060suggests anin situevolution of these elements after the insertion of a Tn6162-like ancestor into the PACS171b-like genomic island (GI) present in the genome of a successful widespreadP. aeruginosaclonal lineage.