title: Complex multiple antibiotic and mercury resistance region derived from the r-det of NR1 (R100).
abstract: The sequence of the 45.2-kb multidrug and mercury resistance region of pRMH760, a large plasmid from a clinical isolate of Klebsiella pneumoniae collected in 1997 in Australia, was completed. Most of the modules found in the resistance determinant (r-det), or Tn2670, region of NR1 (also known as R100), isolated from a Shigella flexneri strain in Japan in the late 1950s, were present in pRMH760 but in a different configuration. The location was also different, with the Tn2670-derived region flanked by the transposition module of Tn1696 and a mercury resistance module almost identical to one found in the plasmid pDU1358. This arrangement is consistent with a three-step process. First, the r-det was circularized via homologous recombination between the IS1 elements and reincorporated at a new location, possibly in a different plasmid, via homologous recombination between the 5'-conserved (5'-CS) or 3'-CS of the In34 integron in the r-det and the same region of a second class 1 integron in a Tn1696 relative. Subsequently, resolvase-mediated recombination between the res sites in the r-det and a second mercury resistance transposon removed one end of the Tn1696-like transposon and part of the second transposon. Other events occurring within the r-det-derived portion have also contributed to the formation of the pRMH760 resistance region. Tn2 or a close relative that includes the bla(TEM-1b) gene had moved into the Tn21 mercury resistance module with subsequent deletion of the adjacent sequence, and all four 38-bp inverted repeats corresponding to Tn21 family transposon termini have been interrupted by an IS4321-like element.
authors.affiliation: School of Molecular and Microbial Biosciences, Biochemistry and Microbiology Building G08, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Sally R
authors.initials: SR
authors.lastname: Partridge
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Hall
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D032023:Integrons / Q000235:genetics; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000235:genetics*; D008628:Mercury / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D011815:R Factors / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D008628:Mercury