title: Molecular clonality and antimicrobial resistance in Salmonella enterica serovars Enteritidis and Infantis from broilers in three Northern regions of Iran.
abstract: BACKGROUND
  Multidrug-resistant Salmonella strains are frequently encountered problems worldwide with considerable increased occurrences in recent years. The aim of this study was to investigate the occurrence and frequency of antimicrobial resistance and associated resistance genes in Salmonella isolates from broiler farms in different regions of Iran covering a time period of four years.
  
  
  RESULTS
  From 2007 to 2011, 36 Salmonella strains were isolated from broiler farms located in three northern provinces of Iran. The isolates were serotyped, antimicrobial susceptibility tested, and characterized for antimicrobial resistance genes associated to the phenotype. Pulsed-field gel electrophoresis (PFGE) was applied for comparison of genetic relatedness.Two serovars were detected among the isolates; Salmonella enterica serovar Infantis (75%) and S. Enteritidis (25%). Thirty-four (94%) of the isolates exhibited resistance to nalidixic acid and ciprofloxacin caused by a single mutation in the quinolone resistance-determining region (QRDR) of gyrA. For all strains this mutation occurred in the codon of Asp87 leading to a Asp87-Tyr, Asp87-Gly or Asp87-Asn substitutions. All S. Infantis (n = 27) were resistant to tetracycline, spectinomycin, streptomycin, and sulfamethoxazole and harbored the associated resistance genes; tetA, dfrA14, aadA1, and sulI together with class 1 integrons. The isolates revealed highly similar PFGE patterns indicating clonal relatedness across different geographical locations.
  
  
  CONCLUSIONS
  The data provided fundamental information applicable when launching future control programs for broilers in Iran with the aim to conserve the effectiveness of important antimicrobials for treatment in humans.
authors.affiliation: Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.
authors.forename: Maral
authors.initials: M
authors.lastname: Rahmani
authors.forename: Seyed Mostafa
authors.initials: SM
authors.lastname: Peighambari
authors.forename: Christina Aaby
authors.initials: CA
authors.lastname: Svendsen
authors.forename: Lina M
authors.initials: LM
authors.lastname: Cavaco
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Agersø
authors.forename: Rene S
authors.initials: RS
authors.lastname: Hendriksen
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002645:Chickens / Q000382:microbiology; D003001:Cloning, Molecular; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D005798:Genes, Bacterial / Q000235:genetics; D007492:Iran / Q000453:epidemiology; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D011201:Poultry Diseases / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D019779:Salmonella enterica / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D012477:Salmonella enteritidis / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D012703:Serotyping / Q000662:veterinary
chemical_list: D000900:Anti-Bacterial Agents
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