No Evidence of Temperature-Driven Antimicrobial Resistance in Salmonella Bacteraemia in Queensland, Australia

Background: Antimicrobial resistance (AMR) has been predicted to worsen with rising ambient temperatures and climate change, though the causal association between temperature and antimicrobial resistance in Salmonella species remains unconfirmed. This study investigates the association between rising ambient temperatures and resistance to antimicrobials used to treat Salmonella bacteraemia in Queensland, Australia. Methods: Time-series analysis with distributed lag non-linear models was used to test associations between deseasonalised temperature and resistance to ampicillin, ciprofloxacin, gentamicin, and third-generation cephalosporins, adjusting for precipitation, seasonality, and temporal trends. Results: A total of 1012 Salmonella bacteraemia cases were analysed in this study. Resistance to any antibiotic occurred in 25.5% of cases (95% CI: 22.8-28.3), resistance to gentamicin in 15.4% (95% CI: 13.2-17.8), and resistance to cephalosporins in 15% (95% CI: 12.9-17.4), with variation among Salmonella serotypes. After adjustment, no antimicrobial resistance was significantly associated with temperature: gentamicin (RR = 1.23 per 1 °C, 95% CI: 0.57-2.65, p = 0.59), cephalosporins (RR = 1.19, 95% CI: 0.52-2.72, p = 0.68), ciprofloxacin (RR = 1.88, 95% CI: 0.29-12.03, p = 0.50), and ampicillin (RR = 1.93, 95% CI: 0.28-13.17, p = 0.50). A marginal temperature-precipitation interaction for cephalosporins, identified using GAM (p = 0.048), did not remain significant after multiple testing correction, nor was it robust across model specifications (GLM p = 0.058) or cross-validation. Conclusions: The findings demonstrate that climate-AMR relationships are not universal, highlighting the importance of geographic, epidemiologic, and organism contexts in these associations.