Antibiotic susceptibility and molecular characterization of resistance genes among Escherichia coli and among Salmonella subsp. in chicken food chains

Abstract Objective To investigate the occurrence of resistance genes among Escherichia coli ( E. coli ) and Salmonella subsp. isolated in chicken food chains in Phnom Penh, 2012–2013. Methods Six hundred eighty two E . coli and 181 Salmonella Albany, Corvallis, and Kentucky strains were examined for susceptibilities to eight antimicrobials and following resistance genes were identified by PCR: bla Tem , StrA , aadA , sul1 , sul2 , gyrA , Tet (A) , and Tet (B) . Results E . coli presented high resistances to tetracycline, amoxicillin, and sulfamethoxazole (63.1%–76.1%). Salmonella Albany and Salmonella Kentucky traduced high resistance percentages to amoxicillin, tetracycline, sulfamethoxazole, and nalidixic acid (84.6%–100%). Among amoxicillin-resistant isolates, bla Tem genes were observed for 62% of E . coli isolates and 20% of 65 Salmonella Kentucky. The StrA gene was prevalent in 36% of 331 aminoglycoside-resistant E . coli and 90% of 40 aminoglycoside-resistant Salmonella Corvallis. The sul2 gene was predominant among sulfamethoxazole-resistant isolates, for 56% of 431 E . coli and 53% of 66 Salmonella Corvallis; the sul1 gene was observed in 54% of Salmonella Albany. The Tet (A) resistance gene was prevalent in E . coli (86%), Salmonella Corvallis (82%), Salmonella Kentucky (84%). High percentages of gyrA genes observed among nalidixic-acid resistant E . coli (91%), Salmonella Albany (92%), Salmonella Corvallis (75%) and Salmonella Kentucky (85%). Conclusions Important occurrences of resistance gene were observed among E . coli and Salmonella in chicken food chains in Cambodia.