Antimicrobial resistance in Escherichia coli strains isolated from organic and conventional pork meat: a comparative survey

Mean counts of Escherichia coli were determined for 54 samples of organic pork meat, and in 67 samples of conventional pork meat. Up to three E. coli strains from each sample were analysed by an agar disk diffusion assay for their resistance to ampicillin, chloramphenicol, cephalotin, doxycycline, enrofloxacin, gentamicin, nitrofurantoin, sulfisoxazole and streptomycin by the agar disk diffusion method. Results indicated that the presence of E. coli was significantly (P < 0.05) higher in organic pork meat as compared to conventional pork meat. Isolates from organic pork meat exhibited lower levels of antimicrobial resistance against ampicillin (P < 0.0001), doxycycline (P < 0.0001) and sulfisoxazole (P < 0.0001), as compared to isolates from conventional meat. Moreover, presence of multi-resistant E. coli strains was significantly (P < 0.0001) higher in conventional pork meat as compared to organic pork meat, the largest differences being observed for isolates resistant to combinations of ampicillin, sulfisoxazol and/or doxycycline. Organically-farmed pork samples showed significantly lower development of antimicrobial resistance in E. coli, thus contributing to reduce the development and spread of antimicrobial resistance among these food-borne bacteria.