Characterization of the complete nucleotide sequence of IncA/C2 plasmids carrying In809-like integrons from Enterobacteriaceae of wildlife origin [PublishAheadOfPrint]

A total of 18 Enterobacteriaceae (seventeen from gulls, and one from a clinical sample), carrying IncA/C plasmids with the IMP-encoding In809-like integrons, collected from Australia were studied. Seven plasmids being representatives of different origins, plasmid sizes, replicon combinations and resistance genes, were completely sequenced. Plasmid pEc158, identified in a clinical ST752 Escherichia coli isolate, showed extensive similarity to type 2 IncA/C₂ plasmids. pEc158 carried none of the bla_CMY-2-like region, ARI-B and ARI-A regions, while it contained a hybrid transposon structure. The six remaining plasmids, which were of wildlife origin, were highly similar to each other and probably were fusion derivatives of type 1 and type 2 A/C₂ plasmids. The latter plasmids contained an ARI-B region and hybrid transposon structures. In all plasmids, hybrid transposon structures containing In809-like integrons were inserted 3434 bp downstream the rhs2 start codon. In all cases, the one outermost 38 bp IR of the transposon was associated with the Tn1696 tnp module, while the other outermost 38 bp IR of the transposon was associated with either a Tn6317-like module or a Tn21 mer module. However, the internal structure of the transposon and the resistance genes were different in each plasmid. These findings indicated that, for the specific periods of time and settings, different IncA/C₂ plasmid types carrying In809-like elements circulated among isolates of wildlife and clinical origin. Additionally, they provided the basis for speculations regarding the reshuffling of IncA/C₂ plasmids with In809-like integrons and confirmed the rapid evolution of IncA/C₂ plasmid lineages.

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