News release

From: The Lancet

Climate change linked to rising antibiotic resistance in Salmonella worldwide, study suggests

Climate change is associated with a 10% global increase in Salmonella antibiotic resistance genes between 1940 and 2023, according to the first-of-its-kind study published in The Lancet Planetary Health journal.

Antimicrobial resistance (AMR) is mainly driven by the overuse and misuse of antibiotics, which allows resistant bacteria to survive and spread. However, rising temperatures and changing rainfall patterns can influence how bacteria survive, mutate, and spread, potentially increasing the exchange of antibiotic resistance genes. While previous studies have linked higher temperatures to greater levels of resistant bacteria, global quantitative studies on this relationship have been limited.

The current study analysed the genomes of more than 480,000 Salmonella samples from 139 countries collected between 1940 and 2023, comparing levels of antibiotic resistance genes with changes in average temperature and rainfall over time. The study used a model to study the relationship, finding that AMR doesn’t just increase steadily as temperatures rise, but that the number of resistance genes changes over time in a more complicated way depending on both temperature and rainfall, suggesting that environmental changes can speed up how bacteria adapt to antibiotics.

The study found that 82% of countries studied saw increases in antibiotic resistance genes in Salmonella, with the strongest climate-associated increases occurring in the Middle East and North Africa, followed by South Asia, and Sub-Saharan Africa. The authors note the study shows a link between climate change and antibiotic resistance genes in Salmonella, but it does not prove that climate change directly causes the increase.

The study also used a model to predict the change in antibiotic resistance genes in Salmonella by 2100 under different climate emissions scenarios. The model suggests that if countries meet low-emission climate targets and strengthen efforts to use antibiotics responsibly, levels of resistance genes could be 24% lower than under the highest-emission scenario. However, they caution that these projections, as with all models, involve uncertainty.

The authors say the findings highlight the need to consider climate change when monitoring and addressing AMR. They add that stronger climate action, alongside responsible antibiotic use and improved disease surveillance across humans, animals, and the environment, will be important in limiting the future spread of AMR.