We already knew antibiotic overuse was fueling drug-resistant Salmonella. A major new study suggests climate change is making things worse.
Researchers analyzed more than 480,000 Salmonella genomes collected from 139 countries over 83 years and found that rising temperatures and shifting rainfall patterns are associated with increases in antimicrobial resistance genes (ARGs). The findings, published in The Lancet Planetary Health, add to growing concerns that climate change could make foodborne illness harder to treat. Over the study period, resistance genes in Salmonella increased 38 percent. Climate change alone is estimated to account for roughly 10 percent of that increase.
Why climate conditions affect resistance
The relationship isn’t linear. Researchers observed what they described as a U-shaped pattern: both temperature extremes appear to favor resistant bacteria, but through different mechanisms. Cold stress can activate bacterial survival responses that incidentally promote resistance. Heat accelerates bacterial growth, mutation rates, and horizontal gene transfer. Flooding disperses resistant strains through water systems and agricultural runoff. Drought concentrates contaminants in shrinking water supplies. Different conditions, same outcome: environments that favor resistance.
The practical implication for food safety is the development of environmental resistance reservoirs — in livestock operations, wastewater systems, irrigation water, soil, wildlife corridors, and food processing environments. These reservoirs feed directly into the food supply.
A One Health problem
The study reinforces what researchers call the One Health framework: the recognition that human, animal, and environmental health are inseparable. Salmonella is a natural vehicle for illustrating this. It moves freely between animals, humans, food products, and the broader environment, making it unusually effective at spreading resistance traits across ecosystems. Climate-driven disruptions—more flooding, more drought, more contact between wildlife, livestock, and humans—create more opportunities for resistant strains to travel and exchange genetic material.
The study also found that stronger sanitation infrastructure was associated with lower resistance levels, while higher antibiotic and insecticide use correlated with higher resistance. Critically, sanitation infrastructure is itself vulnerable to climate disruption, particularly in lower-income countries where genomic surveillance is already limited.
Important caveats
The authors are careful to characterize the findings as associations rather than proof of direct causation. Data limitations and uneven surveillance across countries introduce uncertainty. That said, at 480,000 genomes across 83 years and 139 countries, this is one of the largest analyses of its kind, and the consistency of the signal across regions and time periods is difficult to dismiss.
It is worth noting that not all studies point in the same direction: a 2025 analysis of Salmonella bacteraemia cases in Queensland, Australia found no statistically significant association between rising ambient temperatures and antibiotic resistance.
What this means for food safety
Food safety planning has traditionally focused on what happens inside farms, processing facilities, and supply chains. This study makes the case that the broader environment (water systems, climate conditions, ecological disruptions) deserves equal attention.
For the food industry, that means climate resilience may need to become part of food safety strategy, with greater focus on water management, environmental monitoring, and biosecurity. It also strengthens the argument for investment in genomic surveillance as an early warning system for emerging resistance patterns.
The study’s 2100 projections lend urgency to this point: under the highest-emission scenario with unchecked antibiotic use, resistance gene levels are expected to continue rising substantially. Regulatory agencies are beginning to move in this direction. The FDA’s Human Foods Program included expanded genomic surveillance as a priority for 2025, integrating whole-genome sequencing data from foodborne pathogen networks into a new outbreak surveillance platform. That infrastructure, if sustained and expanded internationally, could become essential for detecting the climate-driven resistance shifts this study describes before they reach consumers.
Zhou Z, et al. “Association of climate change with the spread of antimicrobial resistance genes in Salmonella: a longitudinal ecological and modelling study.” The Lancet Planetary Health (2026). https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(26)00018-5/fulltext Horizontal gene transfer is the movement of genetic material between bacteria without reproduction (that is, other than by standard parent-to-offspring inheritance). In bacteria, it is a primary mechanism by which resistance traits spread rapidly across strains and species, including via plasmids—small, transferable DNA molecules that can carry multiple resistance genes simultaneously. One Health is gaining recognition in the United States and globally as an effective way to fight health issues at the human-animal-environment interface, including zoonotic diseases. CDC uses the One Health approach by involving experts in human, animal, environmental health, and other relevant disciplines and sectors in monitoring and controlling public health threats and to learn about how diseases spread among people, animals, plants, and the environment. Manchal N, et al. “No Evidence of Temperature-Driven Antimicrobial Resistance in Salmonella Bacteraemia in Queensland, Australia.” Antibiotics 14:12 (2025). https://www.mdpi.com/2079-6382/14/12/1274