Aims: To investigate the transfer of antibiotic resistance from a donor Salmonella Typhimurium DT104 strain to a recipient Escherichia coli K12 strain.
Methods and Results: Mating experiments were conducted in broth, milk and ground meat (beef) at incubation temperatures of 4, 15, 25 and 37°C for 18 and 36 h. Ampicillin-resistance transfer was observed at similar frequencies in all transfer media at 25 and 37°C (10−4 to 10−5 log10 CFU ml g−1, transconjugants per recipient) for 18 h. At 15°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°C, transfer did not occur in any of the examined mediums. Further analysis of the E. coli K12 nalR transconjugant strain revealed the presence of a newly acquired plasmid (21 kbp) bearing the β-lactamase gene blaTEM. Transconjugants isolated on the basis of resistance to ampicillin did not acquire any other resistant markers.
Conclusion: This study demonstrates the transfer of antibiotic resistance in food matrices at mid-range temperatures.
Significance and Impact of the Study: It highlights the involvement of food matrices in the dissemination of antibiotic-resistant genes and the evolution of antibiotic-resistant bacteria
