title: A type 2 A/C2 plasmid carrying the aacC4 apramycin resistance gene and the erm(42) erythromycin resistance gene recovered from two Salmonella enterica serovars.
abstract: OBJECTIVE
  To determine the relationships between RepA/C2 plasmids carrying several antibiotic resistance genes found in isolates of Salmonella enterica serovars Ohio and Senftenberg from pigs.
  
  
  METHODS
  Illumina HiSeq was used to sequence seven S. enterica isolates. BLAST searches identified relevant A/C2 plasmid contigs and contigs were assembled using PCR.
  
  
  RESULTS
  Two serovar Ohio isolates were ST329 and the five Senftenberg isolates were ST210. The A/C2 plasmids recovered from the seven isolates belong to type 2 and contain two resistance islands. Their backbones are closely related, differing by five or fewer SNPs. The sul2-containing resistance island ARI-B is 19.9 kb and also contains the kanamycin and neomycin resistance gene aphA1, the tetracycline resistance gene tetA(D) and an erythromycin resistance gene, erm(42), not previously seen in A/C2 plasmids. A second 30.3 kb resistance island, RI-119, is in a unique location in the A/C2 backbone 8.2 kb downstream of rhs. RI-119 contained genes conferring resistance to apramycin, netilmicin and tobramycin (aacC4), hygromycin (hph), sulphonamides (sul1) and spectinomycin and streptomycin (aadA2). In one of the seven plasmids, this resistance region contained two IS26-mediated deletions. A discrete 5.7 kb segment containing the aacC4 and hph genes and bounded by IS26 on one side and the inverted repeat of Tn5393 on the other was identified.
  
  
  CONCLUSIONS
  The presence of almost identical A/C2 plasmids in two serovars indicates a common origin. Type 2 A/C2 plasmids continue to evolve via addition of new resistance regions such as RI-119 and evolution of existing ones.
authors.affiliation: School of Molecular Bioscience, The University of Sydney, Sydney, New South Wales, Australia christopher.harmer@sydney.edu.au.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Harmer
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: School of Molecular Bioscience, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Hall
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004265:DNA Helicases / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology*; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D009328:Nebramycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D010957:Plasmids / Q000145:classification / Q000302:isolation & purification*; D012481:Salmonella Infections, Animal / Q000382:microbiology; D019779:Salmonella enterica / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D009328:Nebramycin; C011666:apramycin; D004917:Erythromycin; D004265:DNA Helicases
keywords: Ohio; RepA/C2; S. enterica; Senftenberg; antibiotic resistance