Increased Costs Associated with Bloodstream Infections Caused by Multidrug-Resistant Gram-Negative Bacteria Are Due Primarily to Patients with Hospital-Acquired Infections

ABSTRACT The clinical and economic impacts of bloodstream infections (BSI) due to multidrug-resistant (MDR) Gram-negative bacteria are incompletely understood. From 2009 to 2015, all adult inpatients with Gram-negative BSI at our institution were prospectively enrolled. MDR status was defined as resistance to ≥3 antibiotic classes. Clinical outcomes and inpatient costs associated with the MDR phenotype were identified. Among 891 unique patients with Gram-negative BSI, 292 (33%) were infected with MDR bacteria. In an adjusted analysis, only history of Gram-negative infection was associated with MDR BSI versus non-MDR BSI (odds ratio, 1. 60; 95% confidence interval CI, 1. 19 to 2. 16; P = 0. 002). Patients with MDR BSI had increased BSI recurrence (1. 7% 5/292 versus 0. 2% 1/599; P = 0. 02) and longer hospital stay (median, 10. 0 versus 8. 0 days; P = 0. 0005). Unadjusted rates of in-hospital mortality did not significantly differ between MDR (26. 4% 77/292) and non-MDR (21. 7% 130/599) groups (P = 0. 12). Unadjusted mean costs were 1. 62 times higher in MDR than in non-MDR BSI (59, 266 versus 36, 452; P = 0. 003). This finding persisted after adjustment for patient factors and appropriate empirical antibiotic therapy (means ratio, 1. 18; 95% CI, 1. 03 to 1. 36; P = 0. 01). Adjusted analysis of patient subpopulations revealed that the increased cost of MDR BSI occurred primarily among patients with hospital-acquired infections (MDR means ratio, 1. 41; 95% CI, 1. 10 to 1. 82; P = 0. 008). MDR Gram-negative BSI are associated with recurrent BSI, longer hospital stays, and increased mean inpatient costs. MDR BSI in patients with hospital-acquired infections primarily account for the increased cost.