As a result of public health concerns regarding antimicrobial resistance in animal-based food products, conventional poultry companies have turned to ‘raised without antibiotics’ (ABF) and organic farming systems. In this work, we evaluated the influence of rearing systems on antimicrobial susceptibility in E. coli and extended-spectrum β-lactamase (ESLB) E. coli diffusion in conventional (C), organic (O) and antibiotic free (ABF) chicken samples collected from cloacal swabs and skin samples in slaughterhouse. The E.