Burden of Antimicrobial Resistance-Attributable Mortality in Nigerian Intensive Care Units: A Multicenter Cohort Study with Quantitative Attribution Modeling

Quantifying the mortality directly attributable to antimicrobial resistance, as distinct from the underlying infection, requires methodologically rigorous attribution modeling that has not been applied in Nigerian intensive care settings. This multicenter prospective cohort study enrolled 600 critically ill adult patients with microbiologically confirmed infections from ICUs at Lagos University Teaching Hospital, Aminu Kano Teaching Hospital, University of Benin Teaching Hospital, and Jos University Teaching Hospital across four geopolitical zones over 24 months. Resistant organism attribution was operationalized using a counterfactual attributable fraction framework comparing outcomes in infections caused by resistant versus susceptible strains of the same species, adjusted for disease severity using APACHE II scores. Thirty-day all-cause mortality and infection-attributable mortality were the primary outcomes. Overall ICU mortality was 38.7 percent. Multi-drug resistant organisms were implicated in 51.3 percent of infections. Attributable mortality fraction for MDR infection was 16.8 percentage points above susceptible-organism infection after severity adjustment. Carbapenem-resistant Acinetobacter baumannii and ESBL-producing Klebsiella pneumoniae carried the highest attributable mortality fractions of 27.4 and 21.3 percent respectively. Total annual AMR-attributable deaths in the four study ICUs were estimated at 312, representing 44 percent of total infection-related ICU deaths. These data provide the first rigorous AMR-attributable mortality estimates from Nigerian ICUs and create an evidence base for health economic prioritization of AMR control investments in Nigeria. Keywords: antimicrobial resistance, mortality attribution, ICU, multicenter cohort, Nigeria.