Association of Climate Change with the Spread of Antimicrobial Resistance Genes in Salmonella: a Longitudinal Ecological and Modelling Study.

BACKGROUND:Antimicrobial resistance (AMR) emerges primarily through antibiotic exposure and the resulting selection pressure, but climate change is likely to accelerate the dissemination of AMR, particularly for zoonotic diseases, such as those caused by Salmonella. However, the link between climatic factors and antimicrobial resistance genes (ARGs) carried by Salmonella remains poorly characterised. This longitudinal ecological study aimed to link climate change to ARGs using multiple regression models. METHODS:We analysed a comprehensive dataset of 488 232 Salmonella genomes and multiple potential predictors from 139 countries or regions over the period 1940-2023. Robustness was verified via Tobit and generalised additive models. Climate-related changes of average ARG abundance in Salmonella were quantified through counterfactual scenarios. Future ARG trends were projected to 2100 using integrated Shared Socioeconomic Pathways (SSPs) with Representative Concentration Pathways scenarios (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5). FINDINGS:The global average ARG abundance in Salmonella has increased by 38% (0·50 copies per cell) in the time period considered. Multiple regression models revealed that variability in ARGs follows a non-linear quadratic response to temperature and precipitation. Climate change is associated with a 10% (95% CI 5·4-13·3) global rise in the abundance of Salmonella ARGs, with increases observed in 82 (82%) of 100 countries. By 2100, the emergence of ARGs is projected to be further intensified by warming; however, achieving low-emission (SSP1-2.6) targets alongside strengthened antibiotic stewardship programmes could reduce Salmonella ARGs by 24% (95% CI 21-29) as compared with high-emission scenarios (SSP5-8.5). INTERPRETATION:This study provides global evidence linking climate change to ARG dynamics in Salmonella. Warming and shifting precipitation patterns are associated with rising ARG abundance and are projected to further exacerbate AMR risks under high-emission scenarios (SSP2-4.5, SSP3-7.0, and SSP5-8.5). These findings highlight the need to integrate climate considerations into AMR surveillance and stewardship, providing a quantitative basis for climate-informed strategies to restrict future resistance escalation. FUNDING:National Key Research and Development Program of China, the National Natural Science Foundation of China, Zhejiang Provincial Natural Science Foundation of China, and Beijing Municipal Sci-Tech Project on Ecology and Environment.