Trends in incidence and antimicrobial resistance of Gram-negative bloodstream infections in intensive care units vs other hospital wards: a national surveillance and data linkage study, England, 2017–2024

BACKGROUND: Gram-negative bloodstream infections (GNBSIs) are an important cause of healthcare-associated infection in intensive care units (ICUs), with increasing resistance to broad-spectrum antibiotics observed. There is a need to understand how resistance differs in ICUs to help inform decision-making on antimicrobial use in this setting. METHODS: Reports of Escherichia coli, Klebsiella spp., and Pseudomonas aeruginosa GNBSIs between 2017 and 2024 were linked to hospital data to determine ICU-associated bloodstream infections (ICU-BSIs; including high-dependency units) and to laboratory data to obtain antimicrobial susceptibility results. We estimated GNBSI incidence over time and compared resistance in ICU-BSIs against non-ICU hospital-onset bloodstream infections (niHO-BSIs). RESULTS: Of the 381,810 GNBSIs identified, 6325 (1.7%) were ICU-BSIs, representing 7.5% of hospital-onset BSIs. ICU-BSI incidence varied by pathogen and across the study period. Incidence of Klebsiella spp. and P. aeruginosa ICU-BSIs increased by 104% and 65%, respectively, between 2019/20 and 2020/21, before returning towards baseline levels. Incidence of E. coli ICU-BSIs remained stable before a small reduction in 2022/23. P. aeruginosa ICU-BSIs were more resistant than niHO-BSIs to ceftazidime (13.7% vs 9.0%), piperacillin/tazobactam (15.4% vs 10.3%), and carbapenems (18.9% vs 11.1%). CONCLUSIONS: Rates of GNBSIs have varied by pathogen since 2017, with increases during the COVID-19 pandemic. Resistance to several antibiotics, including carbapenem resistance in P. aeruginosa, was higher in ICU-BSIs than in niHO-BSIs. The finding of elevated resistance highlights the need to identify risk factors for AMR in this setting.