We already knew that antibiotic overuse promotes drug-resistant salmonella. Climate change is making the situation worse, according to a major new study.
Researchers analyzed more than 480,000 Salmonella genomes collected from 139 countries over 83 years and found that rising temperatures and changes in precipitation patterns were associated with increases in antimicrobial resistance genes (ARGs). The research results are Lancet Planetary HealthThere is growing concern that climate change could make foodborne illness more difficult to treat. During the study period, Salmonella resistance genes increased by 38%. Climate change alone is estimated to account for about 10% of this increase.
Why Climatic Conditions Affect Resistance
The relationship is not linear. The researchers observed what they described as a U-shaped pattern. Both temperature extremes appear to favor resistant bacteria, but the mechanisms are different. Cold stress may activate bacterial survival responses that inadvertently promote resistance. Heat accelerates bacterial growth, mutation rates, and horizontal gene transfer. Flooding disperses resistant strains through water systems and agricultural runoff. Droughts concentrate pollutants in dwindling water supplies. Different conditions, same result: an environment that favors resistance.
Practical implications for food safety include the development of environmental resistance reservoirs in livestock operations, wastewater systems, irrigation water, soils, wildlife corridors, and food processing environments. These reservoirs directly affect our food supply.
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 vector to illustrate this. Because they move freely between animals, humans, food and the wider environment, they are very effective in spreading resistant traits throughout the ecosystem. Climate-induced disruptions, including increased flooding, increased drought, and increased contact between wildlife, livestock, and humans, create more opportunities for resistant strains to move and exchange genetic material.
The study also found that stronger sanitation infrastructure was associated with lower levels of resistance, while higher use of antibiotics and pesticides was correlated with higher resistance. Critically, sanitation infrastructure itself is vulnerable to climate change, especially in low-income countries where genomic surveillance is already limited.
Important precautions
The authors were careful to characterize their findings as associations rather than evidence for direct causal relationships. Data limitations and uneven surveillance across countries create uncertainty. In other words, this analysis, which analyzed 480,000 genomes across 83 years and 139 countries, is one of the largest analyzes of its kind, and the consistency of the signal across regions and time periods is difficult to ignore.
It’s worth noting that not all studies point in the same direction. A 2025 analysis of Salmonella bacteremia cases in Queensland, Australia, found no statistically significant association between increased ambient temperature and antibiotic resistance.
What does this mean for food safety?
Food safety planning has traditionally focused on what happens inside the farm, processing facility, and supply chain. This study shows that the wider environment (water systems, climate conditions, ecological degradation) deserves equal attention.
For the food industry, this means climate resilience must become part of food safety strategies, with greater focus on water management, environmental monitoring and biosecurity. It also strengthens the argument for investing in genomic surveillance as an early warning system for emerging resistance patterns.
The study’s 2100 projections lend urgency to this moment. In the highest emissions scenario, where antibiotic use is not confirmed, resistance gene levels are expected to continue to rise substantially. Regulators are starting to move in this direction. The FDA’s Human Food Program includes expanded genomic surveillance as a 2025 priority, incorporating whole-genome sequencing data from the foodborne pathogen network into new outbreak surveillance platforms. If this infrastructure is sustained and expanded internationally, it could become essential for detecting climate-induced resistance changes described in this study before they reach consumers.
- Zhou Z, et al. “Association between the spread of antimicrobial resistance genes in Salmonella and climate change: a longitudinal ecology and modeling study.” 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 (i.e., other than the standard parent-to-offspring inheritance). In bacteria, this is the main mechanism by which resistance traits spread rapidly across strains and species, involving plasmids, small, mobile DNA molecules that can carry multiple resistance genes simultaneously.
- One Health is recognized in the United States and around the world as an effective way to address health problems at the human-animal-environment interface, including zoonotic diseases. CDC uses a One Health approach that engages experts in human, animal, environmental health, and other related fields and sectors to monitor and control public health threats and learn how diseases spread among people, animals, plants, and the environment.
- Manchal N, et al. “There is no evidence for temperature-dependent antimicrobial resistance in Salmonella bacteremia in Queensland, Australia.” Antibiotics 14:12 (2025). https://www.mdpi.com/2079-6382/14/12/1274
