title: [Antibiotic resistance and virulence factors in clinical Salmonella enterica isolates].
abstract: BACKGROUND
  The increase of Salmonella enterica isolates multi-resistant to different antibiotics, including β-lactams and fluoroquinolones, is a problem of clinical importance. The dissemination of Salmonella Typhimurium resistant to ampicillin (AMP)-chloramphenicol (CHL)-streptomycin (STR)-sulphonamides and (SUL)-tetracycline (TET), that harbour the Salmonella Genomic Island type 1 (SGI1), and the acquisition of transferable genetic material have favoured the multi-resistance in this genus.
  
  
  METHODS
  A total of 114 clinical S.enterica isolates were studied (period 2009-2010). The susceptibility to 20 antibiotics was determined by disc diffusion and microdilution. The antimicrobial resistance mechanisms and the integrons were analysed by PCR, and sequencing in the AMP(R) isolates. In all the blaPSE-1-positive isolates, the clonal relationship was determined by PFGE, as well as the presence of SGI1 and 29 virulence genes by PCR.
  
  
  RESULTS
  Eighteen different serotypes were found among the 114 isolates studied, Typhimurium (61%) and Enteritidis (16%) being the most prevalent. High percentages of resistance to SUL (68%), TET (58%), AMP (55%) and STR (46%) were observed. The great majority (92%) of 63 AMP(R) isolates were multi-resistant, with the AMP-STR-TET-SUL phenotype (19 isolates) being the most frequent one and associated with the blaTEM-1b+strA-strB+tet(B)+sul2 genotype. Class 1 integrons (7 different structures) were observed in 48% AMP(R) isolates, highlighting the blaOXA-1+aadA1 structure (8 isolates), one empty integron and non-classical integrons (5 isolates). The blaPSE-1 gene was detected inside the classical SGI1 structure in 13 clonally-related isolates that showed the same virulence profile.
  
  
  CONCLUSIONS
  The high percentage of multi-resistant S.enterica isolates, especially associated to S.Typhimurium, to the AMP, STR, TET and SUL phenotype, and to the blaTEM-1b+strA-strB+tet(B)+sul2 genotype, shows an important risk of possible failures in the treatment of serious infections caused by this serotype.
authors.affiliation: Área de Microbiología Molecular, Centro de Investigación Biomédica de La Rioja (CIBIR), Logroño, España; Área de Bioquímica y Biología Molecular, Universidad de La Rioja, Logroño, España.
authors.forename: María
authors.initials: M
authors.lastname: de Toro
authors.affiliation: Servicio de Microbiología, Hospital Clínico Universitario Lozano Blesa, Zaragoza, España; Departamento de Microbiología, Facultad de Medicina, Universidad de Zaragoza , Zaragoza, España.
authors.forename: Cristina
authors.initials: C
authors.lastname: Seral
authors.affiliation: Área de Microbiología Molecular, Centro de Investigación Biomédica de La Rioja (CIBIR), Logroño, España.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Rojo-Bezares
authors.affiliation: Área de Microbiología Molecular, Centro de Investigación Biomédica de La Rioja (CIBIR), Logroño, España; Área de Bioquímica y Biología Molecular, Universidad de La Rioja, Logroño, España.
authors.forename: Carmen
authors.initials: C
authors.lastname: Torres
authors.affiliation: Servicio de Microbiología, Hospital Clínico Universitario Lozano Blesa, Zaragoza, España; Departamento de Microbiología, Facultad de Medicina, Universidad de Zaragoza , Zaragoza, España.
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Castillo
authors.affiliation: Área de Microbiología Molecular, Centro de Investigación Biomédica de La Rioja (CIBIR), Logroño, España. Electronic address: ysaenz@riojasalud.es.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Sáenz
mesh_terms: D024881:Drug Resistance, Bacterial / Q000235:genetics; D044404:Genomic Islands; D006801:Humans; D032023:Integrons; D008826:Microbial Sensitivity Tests; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D037521:Virulence Factors
chemical_list: D037521:Virulence Factors
keywords: ACSSuT phenotype; Ampicillin-resistance; Electroforesis en gel de campo pulsado; Fenotipo ACSSuT; Integrones; Integrons; Isla genómica de Salmonella de tipo 1; Pulsed-field gel electrophoresis; Resistencia a ampicilina; Salmonella Genomic Island type 1; bla(OXA-1); bla(PSE-1)