Impact of time to positive blood culture on mortality in intensive care unit patients with bacteremia: a retrospective cohort study

Abstract 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. This study evaluated whether shorter time-to-positivity was associated with increased in-hospital mortality among critically ill patients with bacteremia. Methods This 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. The primary outcome was in-hospital mortality. Secondary outcomes include time to empiric antimicrobial therapy, time to positive blood culture, appropriate empiric antibiotic coverage, length of definitive treatment, and hospital length of stay. Results A total of 166 patients were included in the final analysis. Patients were divided into two separate groups, rapid time to initial positive blood culture (< 360 min, n = 81) and prolonged time to initial positive blood culture (> 360 min, n = 85). Patients with rapid TTP suffered higher all-cause in-hospital mortality (47%) compared to the prolonged TTP group (39%; p = 0.292), although not statistically significant. In the multivariable analysis, MRSA bacteremia and higher APACHE II scores were independently associated with increased mortality, while infectious disease consultation was associated with reduced mortality. Conclusion These findings support existing evidence that shorter TTP may serve as an early surrogate marker of bacterial burden and illness severity in critically ill patients with bacteremia. Although rapid TTP did not shorten time to empiric or definitive antimicrobial therapy, it may be associated with higher in-hospital mortality, suggesting that rapid microbial growth may reflect higher burden of infection.