Sequencing of bla IMP -Carrying IncN2 Plasmids, and Comparative Genomics of IncN2 Plasmids Harboring Class 1 Integrons.

This work presents the complete nucleotide sequences of p0801-IMP from Klebsiella pneumoniae , p7121-IMP from K. oxytoca , and p17285-IMP from Citrobacter freundii , which are recovered from three different cases of nosocomial infection. These three plasmids represent the first fully sequenced bla IMP -carrying IncN2 plasmids. Further comparative genomics analysis of all the five integron-carrying IncN2 plasmids p0801-IMP, p7121-IMP, p17285-IMP, pJIE137, and p34983-59.134kb indicates that they possess conserved IncN2 backbones with limited genetic variations with respect to gene content and organization. Four class 1 integrons ( bla IMP-1 -carrying In1223 in p0801-IMP/p7121-IMP, bla IMP-8 -carrying In655 in p17285-IMP, In27 in pJIE137, and In1130 in p34983-59.134kb), two insertion sequence-based transposition units (IS Ecp1 - orfRA1-14 in p17285-IMP, and IS Ecp1 - bla CTX- M -62 -Δ orf477 - orfRA1-14 in pJIE137), and a novel Tn 1696 -related transposon Tn 6325 carrying In1130 in p34983-59.134kb are indentified in the plasmid accessory regions. In1223 and In655 represent ancestral Tn 402 -associated integrons, while In27 and In1130 belong to complex class 1 integrons. The relatively small IncN2 backbones are able to integrate different mobile elements which carry various resistance markers, promoting the accumulation and spread of antimicrobial resistance genes among enterobacterial species.