The pattern, association with multidrug-resistance and transferability of plasmid-mediated tetracycline resistance in Escherichia coli isolates from the poultry in Iran

Objective of this study was to assess the pattern of plasmid-mediated tetracycline-resistance (Tet(r)) in poultry Escherichia coli, to verify whether this resistance is associated with multidrug-resistance (MDR), and to know about the involvement of efflux via detection of tet (A) and tet (C). Seventy poultry E. coli-isolates were tested against tetracycline, beta-lactams, quinolones/flouroquinolone, chloramphenicol, aminoglycosides, and trimethoprim-sulphamethoxazole (SXT) by disk-diffusion. Plasmid-DNA from Tet(r)-isolates were compared by electrophoresis and transferred to DH5a and Hb101 E. coli strains via electroporation and conjugation; presence of tet(A) and tet(C) was detected by PCR. Transformants and transconjugants were compared with donor strains in plasmids, restriction-endonuclease patterns, and presence of tet (A) or tet (C) Eighty-nine percent and 11% of the isolates were resistant and intermediately-resistant to Tet; of which 75% were multidrug-resistant to quinolones/flouroquinolone, SXT, chloramphenicol and/or beta-lactams. Their plasmid profile was heterogenous but 72% contained a 100 Kb plasmid-band. Fifty-percent, 19%, and 3% of the Tetr-isolates amplified for tet(A), tet(C), and both of them, respectively. Transformants and transconjugants have acquired a large 100 Kb-plasmid with similar restriction-endonuclease patterns of the donor-strains, resistance to Tet, SXT, beta-lactams, and the efflux determinants of Tet(A), or tet(C). Escherichia coli strains from poultry in Iran are heterogeneous, multidrug-resistant, contain a large transferable-plasmid conferring resistance to Tet, beta-lactams, SXT and carrying the Tet efflux genes of tet(A) and/or tet(C). These data indicate that poultry E. coli strains in this region can be a reservoir for antimicrobial-resistance genes and can play a role in dissemination of resistance genes to other pathogenic and commensal bacteria in poultry industry and/or environment.