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 , Enterobacterales, , Enterococcus species, and . 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 (33% Methicillin-resistant 'MRSA'), Enterobacterales (50% Carbapenem-resistant 'CRE'), and (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.