Excess burden of antibiotic-resistant bloodstream infections: evidence from a multicentre retrospective cohort study in Chile, 2018–2022

Background: Antibiotic-resistant bloodstream infections (ARB BSI) cause an enormous disease and economic burden. We assessed the impact of ARB BSI caused by high- and critical-priority pathogens in hospitalised Chilean patients compared to BSI caused by susceptible bacteria. Methods: We conducted a retrospective cohort study from 2018 to 2022 in three Chilean hospitals and measured the association of ARB BSI with in-hospital mortality, length of hospitalisation (LOS), and intensive care unit (ICU) admission. We focused on BSI caused by Acinetobacter baumannii, Enterobacterales, Staphylococcus aureus, Enterococcus species, and Pseudomonas aeruginosa. We addressed confounding using propensity scores, inverse probability weighting, and multivariate regressions. We stratified by community- and hospital-acquired BSI and assessed total hospital and productivity costs. Findings: We studied 1218 adult patients experiencing 1349 BSI episodes, with 47.3% attributed to ARB. Predominant pathogens were Staphylococcus aureus (33% Methicillin-resistant ‘MRSA’), Enterobacterales (50% Carbapenem-resistant ‘CRE’), and Pseudomonas aeruginosa (65% Carbapenem-resistant ‘CRPA’). Approximately 80% of BSI were hospital-acquired. ARB was associated with extended LOS (incidence risk ratio IRR = 1.14, 95% CI = 1.05–1.24), increased ICU admissions (odds ratio OR = 1.25; 1.07–1.46), and higher mortality (OR = 1.42, 1.20–1.68) following index blood culture across all BSI episodes. In-hospital mortality risk, adjusted for time-varying and fixed confounders, was 1.35-fold higher (1.16–1.58) for ARB patients, with higher hazard ratios for hospital-acquired MRSA and CRE at 1.37 and 1.48, respectively. Using a societal perspective and a 5% discount rate, we estimated excess costs for ARB at $12,600 per patient, with an estimated annual excess burden of 2270 disability-adjusted life years (DALYs) and $9.6 (5.0–16.4) million. Interpretation: It is urgent to develop and implement interventions to reduce the burden of ARB BSIs, particularly from MRSA and CRE. Funding: Agencia Nacional de Investigación y Desarrollo ANID, Chile.