Characterization of Tn7-like transposons and its related antibiotic resistance among Enterobacteriaceae from livestock and poultry in China

Background: This study was aimed to investigate the prevalence and structure of Tn7-like in Enterobacteriaceae from livestock and poultry as well as their possible role as reservoir of antibiotic resistance genes (ARGs). Methods: : Polymerase chain reaction (PCR) and DNA sequencing analyses were used for the characterization of Tn7-like, associated integrons and ARGs. The antimicrobial resistance profile of the isolates was examined by using disc diffusion test. Results: : Three hundred and seventy-eight Tn7-like-positive strains of Enterobacteriaceae were isolated, and included E. coli (128), Proteus (150), K. pneumonia (17), Salmonella (13), M. morganii (21) and A. baumannii (1), wherein high resistance was observed for Trimethoprim/Sulfamethoxazole and Streptomycin, and fifty percent of the strains were multidrug-resistant. Integrons class 2 were detected in all of the isolates and there are high frequency mutation sites especially in 535, a stop mutation. Variable region of class 2 integrons carried same gene cassettes, namely aadA1 - sat2 - dfrA1 . From the 378 isolated strains, we found a new type of Tn7-like on a plasmid, named Tn6765. Conclusions: : These findings proved that the Tn7-like can contribute to the horizontal transmission of antibiotic resistant genes in livestock and poultry. As potential vessels for antibiotic resistance genes (ARGs), Tn7-like could not be ignored due to their efficient transfer ability in environments.