Sequence of Conjugative Plasmid pIP1206 Mediating Resistance to Aminoglycosides by 16S rRNA Methylation and to Hydrophilic Fluoroquinolones by Efflux

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Abstract
Self-transferable IncFI plasmid pIP1206, isolated from an Escherichia coli clinical isolate, carries two new resistance determinants: qepA , which confers resistance to hydrophylic fluoroquinolones by efflux, and rmtB , which specifies a 16S rRNA methylase conferring high-level aminoglycoside resistance. Analysis of the 168,113-bp sequence (51% G+C) revealed that pIP1206 was composed of several subregions separated by copies of insertion sequences. Of 151 open reading frames, 56 (37%) were also present in pRSB107, isolated from a bacterium in a sewage treatment plant. pIP1206 contained four replication regions (RepFIA, RepFIB, and two partial RepFII regions) and a transfer region 91% identical with that of pAPEC-O1-ColBM, a plasmid isolated from an avian pathogenic E. coli . A putative oriT region was found upstream from the transfer region. The antibiotic resistance genes tet (A), catA1, bla TEM-1 , rmtB , and qepA were clustered in a 33.5-kb fragment delineated by two IS 26 elements that also carried a class 1 integron, including the sulI, qacE Δ 1, aad4 , and dfrA17 genes and Tn 10 , Tn 21 , and Tn 3 -like transposons. The plasmid also possessed a raffinose operon, an arginine deiminase pathway, a putative iron acquisition gene cluster, an S -methylmethionine metabolism operon, two virulence-associated genes, and a type I DNA restriction-modification (R-M) system. Three toxin/antitoxin systems and the R-M system ensured stabilization of the plasmid in the host bacteria. These data suggest that the mosaic structure of pIP1206 could have resulted from recombination between pRSB107 and a pAPEC-O1-ColBM-like plasmid, combined with structural rearrangements associated with acquisition of additional DNA by recombination and of mobile genetic elements by transposition.

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