title: Variants of AbGRI3 carrying the armA gene in extensively antibiotic-resistant Acinetobacter baumannii from Singapore.
abstract: To investigate the context of the ribosomal RNA methyltransferase gene armA in carbapenem-resistant global clone 2 (GC2) Acinetobacter baumannii isolates from Singapore.
  
  
  
  Antibiotic resistance was determined using disc diffusion; PCR was used to identify resistance genes. Whole genome sequences were determined and contigs were assembled and ordered using PCR. Resistance regions in unsequenced isolates were mapped.
  
  
  
  Fifteen GC2 A. baumannii isolated at Singapore General Hospital over the period 2004-11 and found to carry the armA gene were resistant to carbapenems, third-generation cephalosporins, fluoroquinolones and most aminoglycosides. In these isolates, the armA gene was located in a third chromosomal resistance island, previously designated AbGRI3. In four isolates, armA was in a 19 kb IS 26 -bounded transposon, designated Tn 6180 . In three of them, a 2.7 kb transposon carrying the aphA1b gene, designated Tn 6179 , was found adjacent to and sharing an IS 26 with Tn 6180. However, in these four isolates a 3.1 kb segment of the adjacent chromosomal DNA has been inverted by an IS 26 -mediated event. The remaining 11 isolates all contained a derivative of Tn 6180 that had lost part of the central segment and only one retained Tn 6179 . The chromosomal inversion was present in four of these and in seven the deletion extended beyond the inversion into adjacent chromosomal DNA. AbGRI3 forms were found in available GC2 sequences carrying armA.
  
  
  
  In GC2 A. baumannii , the armA gene is located in various forms of a third genomic resistance island named AbGRI3. An aphA1b transposon is variably present in AbGRI3.
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia.
authors.forename: Grace A
authors.initials: GA
authors.lastname: Blackwell
authors.affiliation: Centre for Systems Genomics, University of Melbourne, Parkville, Victoria 3010, Australia.|Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Australia.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Holt
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Bentley
authors.affiliation: Saw Swee Hock School of Public Health, National University Health System, Singapore.|Yong Loo Lin School of Medicine, National University Health System, Singapore.
authors.forename: Li Yang
authors.initials: LY
authors.lastname: Hsu
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Hall
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000145:classification* / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D002874:Chromosome Mapping; D052978:Disk Diffusion Antimicrobial Tests; D024901:Drug Resistance, Multiple, Bacterial; D023061:Gene Order; D014644:Genetic Variation; D006801:Humans; D020071:Interspersed Repetitive Sequences; D016133:Polymerase Chain Reaction; D012846:Singapore / Q000453:epidemiology; D012359:tRNA Methyltransferases / Q000235:genetics*
chemical_list: D012359:tRNA Methyltransferases