Air temperature and incidence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae

Higher outdoor temperature may be related to an increase in antibiotic resistant bacteria. We investigated the association between local outdoor air temperature and the incidence of extended-spectrum betalactamase (ESBL)-producing Enterobacteriaceae (ESBL-PE) correcting for known drivers of antibiotic resistance.

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.

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 to 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.

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.