title: Transmission of Salmonella enterica serotype Typhimurium in poultry with and without antimicrobial selective pressure.
abstract: OBJECTIVE
  To determine the effect of antimicrobial selective pressure on the transmission of antimicrobial resistant and sensitive strains of Salmonella in poultry.
  
  
  RESULTS
  Eight pens housed 12 broiler chicks each. Two chicks in four of the pens were inoculated with a Salm. Typhimurium strain resistant to 12 antimicrobials (including tetracycline), and two chicks in each of the four other pens were inoculated with a strain sensitive to all antimicrobials tested. Two pens inoculated with each strain were treated with chlortetracycline and two were not. Chicks were killed on day 7 and caeca were cultured for Salmonella. Experiments were performed independently twice. Chicks exposed to pen mates inoculated with the resistant strain and treated with tetracycline were 90% positive for Salmonella; whereas 60% of chicks given no antimicrobials were positive. Chicks exposed to the sensitive strain were 95% positive with tetracycline treatment and 90% positive without treatment.
  
  
  CONCLUSIONS
  A multidrug-resistant Salm. Typhimurium strain had significantly increased transmission when chicks were treated with tetracycline. Transmission of a sensitive strain was not inhibited by antimicrobial selective pressure at recommended therapeutic dose.
  
  
  CONCLUSIONS
  This study demonstrates that antimicrobial usage may influence the transmission of antimicrobial-resistant pathogens in poultry.
authors.affiliation: US Department of Agriculture, Agricultural Research Service, Bacterial Epidemiology and Antimicrobial Resistance Research Unit, Athens, GA 30605, USA.
authors.forename: J
authors.initials: J
authors.lastname: Bauer-Garland
authors.forename: J G
authors.initials: JG
authors.lastname: Frye
authors.forename: J T
authors.initials: JT
authors.lastname: Gray
authors.forename: M E
authors.initials: ME
authors.lastname: Berrang
authors.forename: M A
authors.initials: MA
authors.lastname: Harrison
authors.forename: P J
authors.initials: PJ
authors.lastname: Fedorka-Cray
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002645:Chickens; D004352:Drug Resistance, Microbial; D007218:Industrial Microbiology; D011201:Poultry Diseases / Q000635:transmission*; D012481:Salmonella Infections, Animal / Q000517:prevention & control / Q000635:transmission*; D012486:Salmonella typhimurium
chemical_list: D000900:Anti-Bacterial Agents