Air Temperature and Incidence of Extended-Spectrum Beta-Lactamase (ESBL)-Producing Enterobacteriaceae – An Observational Time-Series Regression Study

Background: Higher outdoor temperature may be related to an increase in antibiotic resistant bacteria. We investigated the association between outdoor air temperature and the incidence of extended-spectrum betalactamase (ESBL)-producing Enterobacteriaceae (ESBL-PE) correcting for known drivers of antibiotic resistance. Methods: We performed a time-series regression study using prospectively collected weekly surveillance data on all ESBL-PE isolated from in- and outpatients of the University Hospital Basel, a tertiary care center in Switzerland, between 01/2008-12/2017. Temperature was measured hourly at the meteorological institute of the University Basel next to our institution over this time period. A time-series approach using a Poisson regression model and different lag terms for delayed exposure effects was performed to assess associations between minimal, mean and maximal weekly temperature and the number of ESBL-PE recovered. Findings: Over 10 years, recovery of ESBL-PE increased (annual incidence rate ratio [IRR] 1·14, 95%CI 1·13-1·16), while mean weekly temperature measures remained stable. In multivariable analyses, increasing temperature was associated with higher recovery rates of ESBL-PE after three to four weeks, correcting for potential confounders, such as the number of admissions, proportion of long-term nursing facility- and ICU-admissions, age, Charlson comorbidity index and consumption of antimicrobials (IRRs per 10°C ranging from 1·14-1·22, 95%CIs 1·07-1·33). These trends remained when analyzing correlations between temperature with the proportion of extended spectrum cephalosporin resistance of all recovered Enterobacteriaceae. Interpretation: Higher outdoor temperature may be associated with an increase of ESBL-PE-incidence, independent of important confounders, such as antimicrobial consumption and thus should be considered for future resistance-trajectories. Funding Statement: This work was supported by the University Hospital Basel, Switzerland. No further funding was received for this study. Declaration of Interests: None of the authors has any conflict of interest related to this study. Ethics Approval Statement: This study was approved by the local ethics committee (Project-ID ID 2017-00100).