title: IncA/C plasmids mediate antimicrobial resistance linked to virulence genes in the Spanish clone of the emerging Salmonella enterica serotype 4,[5],12:i:-.
abstract: OBJECTIVE
  To broaden knowledge of the molecular bases and genetics of multidrug resistance in clinical isolates of Salmonella enterica serotype 4,5,12:i:- belonging to the Spanish clone.
  
  
  METHODS
  The relatedness of the isolates was determined by phage typing and XbaI-PFGE. Resistance genes, integrons and transposable elements were identified by PCR amplification and sequencing. Plasmids were characterized by alkaline lysis, S1-PFGE, conjugation, replicon typing and Southern blot hybridization.
  
  
  RESULTS
  The isolates were closely related and resistant to five to seven antimicrobials (ampicillin, chloramphenicol, gentamicin, streptomycin/spectinomycin, sulphonamides, trimethoprim and tetracycline, arranged in different combinations). Most of the responsible genes were provided by a conventional class 1 integron with the dfrA12-orfF-aadA2 variable region, an atypical class 1 integron containing sul3 next to the estX-psp-aadA2-cmlA1-aadA1 variable region and a truncated Tn1721 transposon carrying tet(A). A defective Tn21 with the mer operon and ISVsa3 associated with sul2 were also detected. All resistance genes and mobile genetic elements were located on large, non-conjugative and highly variable plasmids carrying one (A/C) or two (A/C and N) replicons, as well as virulence genes of pSLT.
  
  
  CONCLUSIONS
  IncA/C plasmids are responsible for multidrug resistance in an increasing number of relevant human and animal bacterial pathogens, and hence are regarded as an important threat to public health. Those found in the Spanish clone of Salmonella 4,5,12:i:- constitute a relevant example of short-term evolution, and could have been involved in the successful adaptation of this pathogen.
authors.affiliation: Departamento de Biología Funcional (Área de Microbiología), Universidad de Oviedo, 33006-Oviedo, Asturias, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: García
authors.forename: Beatriz
authors.initials: B
authors.lastname: Guerra
authors.forename: Margarita
authors.initials: M
authors.lastname: Bances
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Mendoza
authors.forename: M Rosario
authors.initials: MR
authors.lastname: Rodicio
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D015373:Bacterial Typing Techniques; D001434:Bacteriophage Typing; D015139:Blotting, Southern; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial; D006801:Humans; D032023:Integrons; D017720:Molecular Epidemiology; D058889:Molecular Typing; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012480:Salmonella Infections / Q000453:epidemiology* / Q000382:microbiology; D012481:Salmonella Infections, Animal / Q000453:epidemiology* / Q000382:microbiology; D019779:Salmonella enterica / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013030:Spain / Q000453:epidemiology; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D037521:Virulence Factors