Increase in surgical site infections caused by gram-negative bacteria in warmer temperatures: Results from a retrospective observational study.

Objective: Surgical site infections (SSIs) occur more frequently during periods of warmer temperatures. We aimed to investigate for which pathogens this association is particularly strong.

Design: A retrospective observational study was conducted.

Methods: Data from the SSI-module of the German nosocomial infection surveillance system between 2000 and 2016 were linked with data from the German Meteorological Service. Patient- and procedure-related data were associated with monthly aggregated meteorological data. Due to high correlation with other meteorological parameters, we focused on the outside temperature. Adjusted odds ratios were calculated for SSI rates relating to temperature. SSIs were stratified by pathogen. A P value of <.05 was considered significant.

Results: Altogether, 2,004,793 procedures resulting in 32,118 SSIs were included. Generally, warmer temperatures were associated with a higher SSI risk, especially for SSIs with gram-negative pathogens. This association was particularly prominent for Acinetobacter spp, Pseudomonas aeruginosa, and certain Enterobacteriaceae. Per additional 1°C, we observed a 6% increase in the SSI risk for Acinetobacter spp and a 4% increase for Enterobacter spp. Superficial SSIs with Acinetobacter spp were 10 times more likely to occur when comparing surgeries in months with mean temperatures of ≥20°C to mean temperatures of <5°C.

Conclusions: Higher temperatures were associated with increased SSI rates caused by gram-negative bacteria. Future SSI prevention measures should consider this aspect. Underlying shifts in microbiome composition due to climate factors should be included in further analyses. Given the expected rise of global temperatures until the end of the century, this topic has relevance from multiple perspectives.