Edwardsiella tarda, can carry antibiotic resistance genes (ARGs) on chromosomes and/or plasmids, which can be transmitted to the environmental microbiomes through horizontal gene transfer.  E. tarda is a core bacterium in the aquatic resistomes. Introducing exterior plasmids to the bacterium through conjugation or transformation from the environmental resistomes can make E. tarda and other antibiotic resistant bacteria withstand and grow in the presence of multiple antibiotics. The purpose of this study was to find new recipients that can harbour plasmids isolated from frog farms. In mating experiments, we chose a natural frog isolate E. tarda GT9, which housed no plasmids, and an E. tarda mutant, GT45 Δp1p2, that lost two plasmids due to curing as recipients. Frog farm isolates, E. coli ET82 and E. tarda GT18 were used as donors. After the mating experiments, the transfer efficiencies were calculated. The results showed that E. tarda GT9 and GT45 Δp1p2 were suitable recipients for the transfer of Edwardsiella and E. coli plasmids. These studies will help us elucidate the conjugation process in the natural environment and lead to find novel ways to minimize the spread of antibiotic resistance and other virulent genes among bacteria.

Keywords: Plasmid transfer; E. tarda; E. coli