Time Is of the Essence: The Impact of Delayed Antibiotic Therapy on Patient Outcomes in Hospital-Onset Enterococcal Bloodstream Infections

Abstract

Background: With increasing prevalence of vancomycin-resistant enterococci (VRE), appropriate antibiotic therapy for enterococcal bloodstream infections (EBSI) can be delayed. Data regarding the impact of delayed therapy on EBSI outcomes are conflicting, and the time delay most strongly associated with poor outcomes has not been defined.

Methods: This was a single-center, retrospective cohort study of adult, nonneutropenic patients with hospital-onset EBSI from 2010 to 2014. Classification and regression tree (CART) analysis was used to determine the delay in appropriate therapy most predictive of 30-day mortality. Appropriate therapy was defined as antibiotic therapy to which the enterococci and copathogen, where applicable, were susceptible. Outcomes and clinical characteristics were compared between patients receiving early or delayed therapy, defined by CART timepoint. Poisson regression was employed to determine the independent association of delayed therapy on 30-day mortality and predictors of delayed therapy.

Results: Overall, 190 patients were included. A breakpoint in time to appropriate therapy was identified at 48.1 hours, where 30-day mortality was substantially increased (14.6% vs 45.3%; P < .001). Patients receiving appropriate therapy after 48.1 hours also experienced higher in-hospital mortality and longer EBSI duration. After adjustment for severity of illness and comorbidity, delayed therapy ≥48.1 hours was associated with a 3-fold increase in 30-day mortality (risk ratio, 3.16 [95% confidence interval, 1.96-5.09]). Vancomycin resistance was the only independent predictor of delayed therapy.

Conclusions: In patients with hospital-onset EBSI, receipt of appropriate therapy within the first 48 hours was associated with reduced mortality, underscoring the potential role of rapid diagnostic testing for early identification of VRE.

Keywords: Enterococcus faecalis; Enterococcus faecium; appropriate antibiotic therapy; bacteremia; vancomycin-resistant enterococci.

Figure 1.

Receiver operating characteristic curve of time to appropriate therapy for prediction of 30-day mortality. Abbreviations: AUC, area under the curve; CI, confidence interval.

Figure 2.

Relationship between day appropriate therapy was received and 30-day mortality. ^aP value for χ² and χ² test for linear trend.

Figure 3.

Classification and regression tree analysis results for 30-day mortality stratified by Pitt bacteremia score. ^aWorst score in 48 hours preceding index culture. Abbreviation: TTAT, time to appropriate therapy.