Interdisciplinary insights on selection, surveillance and mitigations of antimicrobial resistance dynamics on a UK dairy farm with relevance to other one health sectors.

Antibiotic use in agriculture is a global driver for antimicrobial resistance (AMR). Dairy farming, one of the largest producers of agricultural waste, represents a critical opportunity for mitigating AMR impacts. We review, synthesize and generalize from results of 10 years of interdisciplinary study of AMR in the waste from a single, medium-sized intensive UK dairy farm and related One Health AMR work. Resistance patterns reflect a combination of (i) short-term stability with (ii) long-term change associated with altered antibiotic use. These dynamics were driven by clonal expansion and contraction characterized by chromosomal carriage of resistance, and co-selection by environmentally stable antimicrobials including copper, zinc and tetracycline, rather than horizontal gene transfer. We outline 10 considerations for study, surveillance and mitigation: (i) the need for long-term longitudinal sampling; (ii) the value of intense focus on representative sites; (iii) inclusion of both Gram-positive and Gram-negative sentinels; (iv) adoption of shared standards for measurement and reporting; (v) use of precise language for AMR hazards to enable appropriate study site selection; (vi) reduction of overall antibiotic use, e.g., through infection control; (vii) continued avoidance of veterinary use of internationally recognized critical human antibiotics; (viii) avoidance of environmentally stable antibiotics such as some tetracyclines; (ix) reduction of co-selection pressure via recovery of metals such as copper and zinc; and (x) mitigation of resistance through storage of slurry without further additions, e.g., through the use of two-tank systems. We propose that these considerations are relevant beyond dairy, applicable in wider livestock, environmental and One Health settings.