2026 Southeastern Residency Conference

Impact of Time to Positive Blood Culture and Time to Definitive Antimicrobial Therapy on Mortality in Intensive Care Unit Patients with Bacteremia
Nicole Rios Serrano, Lena K. Tran, Christopher Lloyd
AdventHealth Kissimmee – Kissimmee, FL

Background: Bacteremia in critically ill patients is associated with a high risk of morbidity and mortality. Delays between blood culture collection, result availability, and adjustment to proper antimicrobial therapy can lead to worse clinical outcomes. Previous studies have linked delayed appropriate therapy to increased mortality, but the relationship between time to positive blood culture and treatment timing remains less defined. This study aims to evaluate the association between time to positive blood culture (TTP) and time to definitive antimicrobial therapy, and their effect on in-hospital mortality among critically ill patients with bacteremia.

Methods: This study was reviewed by the local investigational review board and deemed a quality improvement project. A retrospective analysis was performed on adult patients admitted to the intensive care unit (ICU) with positive blood cultures at AdventHealth Central Florida Division hospitals from July 1, 2023, through June 30, 2025. Data collected from the electronic health record included baseline characteristics, co-morbidities, baseline sepsis markers, pathogen identification, and timing of empiric therapy initiation. The primary outcome was in-hospital mortality. Secondary outcomes include time to definitive antimicrobial therapy, time to positive blood culture, appropriate empiric antibiotic coverage, length of definitive treatment, and hospital length of stay. Descriptive statistics, student t-tests, Mann–Whitney U, or chi-squared test were conducted, as appropriate. This study will identify gaps in diagnostic and treatment workflows and provide actionable data to enhance hospital protocols, strengthen antimicrobial stewardship programs, and improve outcomes for critically ill patients with bacteremia.

Results: After screening 669 patients for exclusion, 166 patients were included in the final analysis. Patients were divided into two separate groups, rapid time to initial positive blood culture (<360 minutes, n=81) and prolonged time to initial positive blood culture (>360 minutes, n=85). Demographics included an average patient age of 66 years for rapid TTP and 64 years for prolonged TTP. The rapid TTP group had 83% of patients meeting sepsis criteria, compared to 79% in the prolonged TTP group (p = 0.525). The predominant organism in the rapid TTP group was Klebsiella pneumoniae (25%) compared to Escherichia coli (24%) in the prolonged TTP group. Piperacillin-tazobactam and vancomycin were the most common antibiotics ordered empirically in both groups. 91% of patients in the rapid TTP group were started on appropriate empiric therapy compared to 84% in the prolonged TTP group (p = 0.129). Patients with rapid TTP suffered higher all-cause in-hospital mortality (47%) compared to the prolonged TTP group (39%; p = 0.292). The median TTP in the rapid group was 272 minutes compared to 567 minutes in the prolonged group (p = 0.001). The median time to definitive antimicrobial therapy was 22 hours for rapid TTP and 21 hours for prolonged TTP (p = 0.691). The hospital length of stay was 14 days for rapid TTP and 14 days for prolonged TTP (p = 0.676). Average time to empiric treatment initiation was 99 minutes for rapid TTP and 156 minutes for prolonged TTP (p = 0.290). Time between antibiotic administration and blood culture collection was on average 172 minutes for rapid TTP and 313 minutes for prolonged TTP (p = 0.0053).

Conclusions: These findings highlight that TTP may serve as an early indicator of illness severity. Although rapid TTP did not shorten time to definitive antimicrobial therapy, it may be associated with higher in-hospital mortality, suggesting that rapid microbial growth may reflect higher burden of infection. This underscores the importance of using rapid TTP as an early warning tool to recognize high-risk patients and guide timely clinical intervention.