Detection of antimicrobial residues in animal manure by a microbiological screening methodology: A non-invasive tool in animal production

Antimicrobial residues are of great importance in food production because of the potential for negative consequences on human health, such as antimicrobial resistance. A large percentage of these drugs are excreted and persist in animal waste. Therefore, animal waste could be used as a non-invasive matrix for antimicrobial analysis, and a tool to control the use of antimicrobials in animal production. A new microbiological screening method for the detection of antimicrobials for six classes in manure was developed, implemented, validated, and verified in vivo. Validation was performed by assessing the specificity, CC8, stability and ruggedness according to (EU) 2021/808. The in vivo verification was performed in broiler chickens. Six birds were treated per group, one for each antimicrobial class. Manure samples were analysed by the screening methodology and HPLC-MS/MS, as confirmation. The implemented six plate screening was specific to detect all antimicrobials tested. A CC8 of 200, mu g kg-1 was determined for macrolides, of 300 mu g kg-1 for 8-lactams and sulphonamides, 400 mu g kg-1 for tetracyclines and lincosamides, and 500 mu g kg-1 for, quinolones. positive samples were confirmed by HPLC-MS/MS. The applicability of the method was tested on pig manure, in these samples a higher number of false positives were obtained with respect to chicken droppings. In conclusion, this new screening method presented performance characteristics that demonstrate utility for the intended analytical applications, ensuring traceability of the results.