The bovine milk microbiome as a One Health interface for antimicrobial resistance, food safety and nutrition

Bovine milk is both a nutrient-rich food matrix and a microbial ecosystem in which composition, food safety and antimicrobial resistance (AMR) intersect. However, these domains are often considered separately, limiting understanding of how milk composition, microbial ecology and resistance dynamics interact across the dairy chain. This review critically synthesises evidence on the bovine milk microbiome as a One Health interface linking nutrition, food safety and AMR across raw, bulk tank and pasteurised milk, and dairy products. Across the literature, three themes emerge. First, milk composition, including nutrients, somatic cell count, inflammatory changes and antimicrobial residues, helps shape microbial ecology and may influence pathogen persistence and antimicrobial resistance gene (ARG) maintenance. Second, milk can harbour antimicrobial-resistant bacteria and clinically relevant ARGs, but the biological significance of detection depends on organism viability, host assignment, mobile-element context, gene expression, processing history and exposure route. Third, resistance dynamics extend beyond the milk matrix through processing environments, equipment biofilms, waste milk feeding and environmental reservoirs, linking animal, food and environmental compartments. Major uncertainties remain regarding the extent to which milk composition drives resistome structure and ARG expression, whether horizontal gene transfer occurs within the milk matrix, whether microbiome diversity provides colonisation resistance against resistant organisms, and the quantitative contribution of milk to human AMR exposure. Evidence is also geographically uneven, particularly for smallholder and informal dairy systems. Future research should prioritise viability-informed, longitudinal farm-to-fork studies integrating milk composition, microbiome profiling, resistome analysis, antimicrobial-use records and processing metadata to guide One Health AMR mitigation.