title: Transfer of ampicillin resistance from Salmonella Typhimurium DT104 to Escherichia coli K12 in food.
abstract: OBJECTIVE
  To investigate the transfer of antibiotic resistance from a donor Salmonella Typhimurium DT104 strain to a recipient Escherichia coli K12 strain.
  
  
  RESULTS
  Mating experiments were conducted in broth, milk and ground meat (beef) at incubation temperatures of 4, 15, 25 and 37 degrees C for 18 and 36 h. Ampicillin-resistance transfer was observed at similar frequencies in all transfer media at 25 and 37 degrees C (10(-4) to 10(-5) log(10 )CFU ml g(-1), transconjugants per recipient) for 18 h. At 15 degrees C, transfer was observed in ground meat in the recipient strain (10(-6), log10 CFU g(-1), transconjugants per recipient), but not in broth or milk. At 4 degrees C, transfer did not occur in any of the examined mediums. Further analysis of the E. coli K12 nal transconjugant strain revealed the presence of a newly acquired plasmid (21 kbp) bearing the beta-lactamase gene bla(TEM). Transconjugants isolated on the basis of resistance to ampicillin did not acquire any other resistant markers.
  
  
  CONCLUSIONS
  This study demonstrates the transfer of antibiotic resistance in food matrices at mid-range temperatures.
  
  
  CONCLUSIONS
  It highlights the involvement of food matrices in the dissemination of antibiotic-resistant genes and the evolution of antibiotic-resistant bacteria.
authors.affiliation: The Ashtown Food Research Centre, Teagasc, Ashtown, Dublin, Ireland. ciara.walsh@ucd.ie
authors.forename: C
authors.initials: C
authors.lastname: Walsh
authors.forename: G
authors.initials: G
authors.lastname: Duffy
authors.forename: P
authors.initials: P
authors.lastname: Nally
authors.forename: R
authors.initials: R
authors.lastname: O'Mahony
authors.forename: D A
authors.initials: DA
authors.lastname: McDowell
authors.forename: S
authors.initials: S
authors.lastname: Fanning
mesh_terms: D000668:Ampicillin Resistance / Q000235:genetics*; D000818:Animals; D003227:Conjugation, Genetic; D048168:Escherichia coli K12 / Q000235:genetics*; D005516:Food Microbiology; D008460:Meat / Q000382:microbiology; D008892:Milk / Q000382:microbiology; D010957:Plasmids / Q000235:genetics; D012486:Salmonella typhimurium / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D001618:beta-Lactamases