Food- and Waterborne Bacteria Transmission and Antimicrobial Resistance Under Climate Change: Evidence Gaps in Mainland Portugal

Climate change is increasingly recognised as a driver of microbial risks and antimicrobial resistance (AMR) dynamics across environmental and human systems. This review synthesises current evidence on how climate-related factors may affect the persistence, dissemination, and AMR profiles of some food- and waterborne bacterial pathogens, using mainland Portugal as a climate-vulnerable Mediterranean case study. The analyses focused on Salmonella spp., pathogenic Escherichia coli, Vibrio spp., Listeria monocytogenes, Shigella spp. and Yersinia enterocolitica, integrating findings from environmental, food-chain, and clinical research within a One Health framework. Evidence associates increasing temperatures with enhanced bacterial growth and shifts in seasonal dynamics. Extreme rainfall and flooding events promote faecal contamination through runoff and sediment resuspension, compromising water quality. Drought conditions may concentrate microbial loads and promote the use of alternative water sources, introducing additional exposure pathways. Aquatic and terrestrial systems emerge as critical interfaces for pathogen transmission and AMR dissemination. In mainland Portugal, data from clinical, food, animal, wildlife, and environmental studies are available. However, studies linking climate variables with environmental metadata, AMR and genomic data remain limited. Climate-informed One Health surveillance, through longitudinal sampling, harmonised metadata, whole-genome sequencing and predictive modelling, is essential to anticipate and mitigate climate-driven microbial and AMR risk.