Increased Costs with Multidrug Resistant Gram Negative Bloodstream Infections Are Primarily Due to Patients with Hospital-Acquired Infections.

The clinical and economic impact of bloodstream infections (BSI) due to multidrug resistant (MDR) Gram negative bacteria is incompletely understood. From 2009-2015, 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] 1.19-2.16; P=0.002). Patients with MDR BSI had increased BSI recurrence (1.7% [5/292] vs 0.2% [1/599]; P=0.02) and longer hospital length of stay (median 10.0 vs.8.0 days; P=0.0005). Unadjusted 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 versus non-MDR BSI ($59,266 vs. $36,452; P=0.003). This finding persisted after adjustment for patient factors and appropriate empiric antibiotic therapy (means ratio 1.18; 95% CI 1.03-1.36; P=0.01). Adjusted analysis of patient sub-populations revealed that increased cost of MDR BSI occurred primarily among patients with hospital-acquired infections (MDR means ratio 1.41, 95% CI 1.10-1.82, P=0.008). MDR Gram negative BSI are associated with recurrent BSI, longer hospital length of stay, and increased mean inpatient costs. MDR BSI in patients with hospital-acquired infections primarily account for the increased cost.