Assessing antibiotic residues in poultry eggs from backyard production systems in Chile, first approach to a non-addressed issue in farm animals

Abstract

Simple Summary Eggs are a readily available and important food source for low income families that raise chicken in their households. It is therefore important to monitor if these products are safe for human consumption and contain no antibiotic residues that could lead to allergic reactions, intoxication, or antimicrobial resistance. However, little is known about the antimicrobial content of eggs consumed in rural households in Chile. Consequently, the aim of this study was to collect chicken eggs from rural households in the central region of Chile and screen them for antimicrobial activity. The results indicate that most collected eggs (73% of the 83 surveyed households), exhibited antimicrobial activity for at least one of the four tested antimicrobials. These results indicate that household members who consume these eggs are in danger of developing antibiotic-related illnesses and could contribute to antimicrobial resistance. Therefore, further studies are required to identify the exact compounds used to treat the chickens and to establish preventive measures to eradicate antimicrobial presence in their food supply. Eggs are the main product generated from backyard poultry production systems (BPS) because they can quickly be consumed and sold to meet essential family needs. Nevertheless, antimicrobial residues can accumulate in this product. The objective of this study was to evaluate the presence of antimicrobial residues in eggs produced by poultry kept in BPS in central Chile. To assess this, eggs were obtained from 83 BPS and analysed to evaluate the presence of antibiotic residues (families: tetracyclines, beta-lactams, aminoglycosides and macrolides), using a Four-Plate Test screening method for the detection, based on a bacterial growth inhibition method. Results show a lack of biosecurity procedures at BPS level, making these systems susceptible to the dissemination of antimicrobial residues. These include intensive animal production units in the proximity, and the presence of shared watercourses with other farms. Furthermore, 66% of the surveyed owners are indicated as giving pharmacological treatments to their chickens. Eggs from 61 BPS were positive for at least one antimicrobial. Fifty-three BPS were positive for more than one antimicrobial, and one BPS was positive for all four antimicrobials tested. Consequently, there is a risk that poultry eggs produced in BPS in central Chile carry residues of different families of antimicrobials.