Defining the Breakpoint Duration of Staphylococcus aureus Bacteremia Predictive of Poor Outcomes

Abstract

Background: Persistent Staphylococcus aureus bacteremia (SAB) is defined based on varying duration in literature. The primary objective was to determine the risk of poor outcomes in relation to bacteremia duration.

Methods: Multicenter, prospective, observational study of adult hospitalized patients with SAB. Medical records were reviewed for pertinent data. Patients were grouped by bacteremia duration: short (1-2 days), intermediate (3-6 days), and prolonged (≥7 days) and compared for risk factors and outcomes.

Results: Of 884 patients, 63% had short, 28% intermediate, and 9% prolonged bacteremia. Overall mean age was 57 years, and 70% were male. The prolonged group had the highest proportion of methicillin-resistant SAB (P < .0001). Choice of antibiotic therapy did not significantly affect bacteremia duration; however, time to source-control procedure was delayed in the prolonged and intermediate groups compared with the short group (3.5 vs 3 vs 1 day, P < .0001). Metastatic complications, length of stay, and 30-day mortality were progressively worse as bacteremia duration increased (P < .0001). Every continued day of bacteremia was associated with a relative risk of death of 1.16 (95% confidence interval, 1.10-1.22; P < .0001), with a significant increase in risk starting at 3 days as determined by receiver operating characteristic analysis.

Conclusions: Optimal management of SAB should target bacterial clearance as soon as possible to minimize incremental risk of mortality with each day of positive blood culture. Delay in source control but not type of antistaphylococcal therapy was significantly associated with prolonged bacteremia and worse outcomes.

Keywords: S. aureus bacteremia; mortality; persistence.

© The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

Figures

Figure 1.

<?Query_Start ?>Relative risk (95% confidence interval) of mortality by duration of bacteremia<?Query_End ?> (N = 884). The numbers of days of infection at 8–10 and 11+ were collapsed to account for the observed sample sizes.

Figure 2.

ROC curve to de<?Query_Start ?>ter<?Query_End ?>mine the cutoff to differentiate 30-day mortality versus survivors. The ROC curve with corresponding labels for the number of days of infection for several optimality criteria plotted for 30-day mortality. The cut-point at 3 days was found to minimize the absolute distance between sensitivity and specificity (diff = 0.04) and the distance to the (0,1), or “ideal” point (D = 0.53). Label C is the cut-point with the maximum correct classification rate. Label Y is the cut-point with the maximum Youden index. Abbreviation: ROC, receiver operating characteristics.