title: A conjugative plasmid carrying the carbapenem resistance gene blaOXA-23 in AbaR4 in an extensively resistant GC1 Acinetobacter baumannii isolate.
abstract: OBJECTIVE
  To locate the acquired bla(OXA-23) carbapenem resistance gene in an Australian A. baumannii global clone 1 (GC1) isolate.
  
  
  METHODS
  The genome of the extensively antibiotic-resistant GC1 isolate A85 harbouring bla(OXA-23) in Tn2006 was sequenced using Illumina HiSeq, and the reads were used to generate a de novo assembly. PCR was used to assemble relevant contigs. Sequences were compared with ones in GenBank. Conjugation experiments were conducted.
  
  
  RESULTS
  The sporadic GC1 isolate A85, recovered in 2003, was extensively resistant, exhibiting resistance to imipenem, meropenem and ticarcillin/clavulanate, to cephalosporins and fluoroquinolones and to the older antibiotics gentamicin, kanamycin and neomycin, sulfamethoxazole, trimethoprim and tetracycline. Genes for resistance to older antibiotics are in the chromosome, in an AbaR3 resistance island. A second copy of the ampC gene in Tn6168 confers cephalosporin resistance and the gyrA and parC genes have mutations leading to fluoroquinolone resistance. An 86 335 bp repAci6 plasmid, pA85-3, carrying bla(OXA-23) in Tn2006 in AbaR4, was shown to transfer imipenem, meropenem and ticarcillin/clavulanate resistance into a susceptible recipient. A85 also contains two small cryptic plasmids of 2.7 and 8.7 kb. A85 is sequence type ST126 (Oxford scheme) and carries a novel KL15 capsule locus and the OCL3 outer core locus.
  
  
  CONCLUSIONS
  A85 represents a new GC1 lineage identified by the novel capsule locus but retains AbaR3 carrying genes for resistance to older antibiotics. Resistance to imipenem, meropenem and ticarcillin/clavulanate has been introduced into A85 by pA85-3, a repAci6 conjugative plasmid carrying Tn2006 in AbaR4.
authors.affiliation: School of Molecular Bioscience, The University of Sydney, NSW 2006, Australia.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Hamidian
authors.affiliation: School of Molecular Bioscience, The University of Sydney, NSW 2006, Australia.
authors.forename: Johanna J
authors.initials: JJ
authors.lastname: Kenyon
authors.affiliation: Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Holt
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK.
authors.forename: Derek
authors.initials: D
authors.lastname: Pickard
authors.affiliation: School of Molecular Bioscience, The University of Sydney, NSW 2006, Australia ruth.hall@sydney.edu.au.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Hall
mesh_terms: D000151:Acinetobacter Infections / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015780:Carbapenems / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D023061:Gene Order; D006801:Humans; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D004251:DNA Transposable Elements; C466679:beta-lactamase OXA-23; D001618:beta-Lactamases
keywords: A. baumannii; Tn2006; conjugative resistance plasmids