Sequence of conjugative plasmid pIP1206 mediating resistance to aminoglycosides by 16S rRNA methylation and to hydrophilic fluoroquinolones by efflux

Unité des Agents Antibactériens, Institut Pasteur, Paris, France; Cliniques Universitaires UCL de Mont-Godinne, Yvoir, Belgium; Centre d'Etudes Pharmaceutiques, Châtenay-Malabry, France; Plate-forme Intégration et Analyse Génomique, Institut Pasteur, Paris, France

^* To whom correspondence should be addressed. Email: pcourval{at}pasteur.fr.

	Abstract

Self-transferable IncFI plasmid pIP1206, isolated from an E. 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 ORFs, 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), 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 IS26, that also carried a class 1 integron including the sulI, qacE1, aad4 and dfrA17 genes, and Tn10, Tn21 and Tn3-like transposons. The plasmid also possessed a raffinose operon, an arginine deiminase pathway, a putative iron-acquisition gene cluster, a S-methylmethionine metabolism operon, two virulence-associated genes, and a type-I DNA restriction-modification 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.