title: Aminoglycoside resistance in multiply antibiotic-resistant Acinetobacter baumannii belonging to global clone 2 from Australian hospitals.
abstract: OBJECTIVE
  To examine the distribution and context of aminoglycoside resistance genes in multiply antibiotic-resistant Acinetobacter baumannii isolates from Australia that are members of the global clone 2 and carry the bla(OXA-23) gene conferring resistance to carbapenems.
  
  
  METHODS
  Sixty-one multiply antibiotic-resistant A. baumannii strains isolated between 2000 and 2010 at six Australian hospitals that belonged to global clone 2 and carried the bla(OXA-23) gene were studied. Various molecular techniques were used to determine their relatedness and to detect antibiotic resistance genes and insertion sequences. Structures surrounding the aminoglycoside resistance genes were sequenced.
  
  
  RESULTS
  The isolates all shared several antibiotic resistance genes, including the sul2 sulphonamide resistance gene, but varied in their pattern of resistance to aminoglycosides. The aminoglycoside resistance profiles of isolates were accounted for by four resistance genes-aadB, aacC1, aphA1b and aphA6-in various combinations. The aadB gene cassette was located at a secondary site on a 6 kb plasmid similar to pRAY. The aphA6 gene was in a transposon, TnaphA6, bounded by directly oriented copies of ISAba125. The aacC1 gene cassette in a class 1 integron and Tn6020 carrying aphA1b were always present together, but were not linked.
  
  
  CONCLUSIONS
  Imipenem-resistant global clone 2 A. baumannii isolates containing bla(OXA-23) have been present in Australian hospitals for at least 10 years. Variation in this global clone 2 type has occurred with the introduction of various aminoglycoside resistance genes carried on a small plasmid or within transposons.
authors.affiliation: School of Molecular Bioscience, The University of Sydney, NSW 2006, Australia.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Nigro
authors.forename: Virginia
authors.initials: V
authors.lastname: Post
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Hall
mesh_terms: D000151:Acinetobacter Infections / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001315:Australia; D003428:Cross Infection / Q000382:microbiology*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D005798:Genes, Bacterial; D005838:Genotype; D006761:Hospitals; D006801:Humans; D008969:Molecular Sequence Data; D058889:Molecular Typing; D010957:Plasmids; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D001618:beta-Lactamases