Assessment of antibiotic resistance in chicken meat labelled as antibiotic-free: A focus on Escherichia coli and horizontally transmissible antibiotic resistance genes

This study has addressed the escalating concern of antibiotic resistance (AR) linked to the use of antibiotics in food -producing animals, particularly in low- and middle -income countries (LMICs). The focus was on assessing the AR profile of 100 Escherichia coli isolates from antibiotic -free (AF) labelled retail chicken meat in comparison to conventional (CL) chicken meat being sold in Delhi, India. Surprisingly, the results revealed a substantial prevalence of resistance in E. coli from AF chicken meat, notably against tetracycline (80 %), ciprofloxacin (67 %), and imipenem (49 %), among others. Moreover, a striking 92 % of AF chicken meat -derived isolates demonstrated resistance to multiple drugs, with 48 % displaying resistance to over six antimicrobial classes. The study also identified prevalent mobile genetic elements -associated antibiotic resistance genes (ARGs), suggesting a potential for horizontal transfer of resistance. Importantly, the research highlighted a lack of significant difference in the AR profile between E. coli from AF and CL chicken meat. Additionally, positive correlations between different AR phenotypes and ARGs suggested the feasibility of predicting physical resistance through molecular resistance and vice versa. In conclusion, the research indicates that at the current state, choosing AFlabelled chicken meat retailing in north Indian market may not effectively reduce the exposure to antibioticresistant bacteria.