Prevalence and Analysis of Antibiotic Resistant Genes in Escherichia coli and Salmonella Isolates from Green Leaf Lettuce

The objective of this study was to evaluate the prevalence and antibiogram of Escherichia coli and Salmonella isolated from green leaf lettuce (n=120), collected from open and supermarkets of Cambodia and Thailand. From 120 samples of lettuce leaves, 47 (39.17%) E. coli and 28 (23.33%) Salmonella were isolated and identified by biochemical and immunological tests. Twenty seven E. coli isolates (57.45%) and 13 Salmonella isolates, (46.43%) were found resistant to at least one of the antibacterial drugs. Escherichia coli were more resistant to amoxicillin and ampicillin (92.6%), followed by tetracycline (70.4%). Almost all the isolated Salmonella were found resistant to ampicillin and amoxicillin, followed by tetracycline (69.23%). The beta-lactam (bla(TEM)) and tetracycline (tetA and tetB) resistance genes were analyzed by polymerase chain reaction in the tested bacterial isolates. This study concludes that fresh vegetables and fruits should be subjected to pretreatment prior to human consumption, to avoid the foodborne illnesses associated with multidrug resistant bacteria. Moreover, the use of antibiotics in agriculture farming should be strictly monitored in developing countries to avoid the emergence of multidrug resistant pathogens.