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. 2025 Apr 30;80(4):727-734.
doi: 10.1093/cid/ciae628.

Time to Staphylococcus aureus Blood Culture Positivity as a Risk Marker of Infective Endocarditis: A Retrospective Cohort Study

Martin Strömdahl  1   2 , Karl Hagman  3   4 , Karolina Hedman  5 , Anna Westman  1   5 , Magnus Hedenstierna  1   2 , Johan Ursing  1   2
Affiliations

Time to Staphylococcus aureus Blood Culture Positivity as a Risk Marker of Infective Endocarditis: A Retrospective Cohort Study

Martin Strömdahl et al. Clin Infect Dis. .

Abstract

Background: Endocarditis occurs in approximately 10%-15% of patients with Staphylococcus aureus bacteremia (SAB). Short time to positivity (TTP) in blood culture flasks has been linked to endocarditis in smaller studies. This study evaluated the association between TTP and endocarditis in SAB in a large cohort.

Methods: Adult patients with ≥1 S. aureus positive blood culture treated at a tertiary-level, 500-bed hospital in Stockholm, Sweden between 2011-2021 were retrospectively identified. The primary outcome was the presence of infective endocarditis.

Results: A total of 1703 episodes of SAB (23/1703 methicillin-resistant) in 1610 patients were included. Median age was 75 (interquartile range [IQR], 63-84) years and median Charlson comorbidity index score was 2 (IQR, 1-3). Echocardiography was performed in 1102/1703 (65%). Thirty-day mortality was 406/1703 (24%) and endocarditis was found in 154/1703 (9%). Median TTP was shorter in patients with endocarditis (9 [IQR, 7-12] hours) compared to patients without endocarditis (13 [interquartile range, 10-18] hours; P < .001). The risk of endocarditis decreased with 11% per hour (odds ratio [OR], 0.89 [95% confidence interval {CI}, .54-.92]; P < .001) in a univariate analysis using TTP as a continuous variable. In multivariate analysis, TTP <13 hours (the median) was independently associated with endocarditis (OR, 3.59 [95% CI, 2.35-5.3]; P < .001). The negative predictive value of TTP >13 hours for endocarditis was 96% (95% CI, 95%-97%).

Conclusions: Short TTP was associated with endocarditis. The negative predictive value of >95% suggests that TTP >13 hours can be used to risk-stratify patients with SAB.

Keywords: Staphylococcus aureus; bacteremia; bloodstream infection; infective endocarditis; time to blood culture positivity.

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Conflict of interest statement

Potential conflicts of interest . The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest.

Figures

Figure 1.
Figure 1.
A, Boxplot of time to positivity in episodes with (n = 154) and without (n = 1549) endocarditis. B, Boxplot of time to positivity in episodes with endocarditis with community-onset (n = 122) or hospital-acquired (n = 32) Staphylococcus aureus bacteremia.
Figure 2.
Figure 2.
Receiver operating characteristic (ROC) curves of the ability of time to positivity to differentiate Staphylococcus aureus bacteremia episodes with and without infective endocarditis. Area under the curve (AUC) was 0.72 (95% confidence interval, .67–.76; P < .001).
Figure 3.
Figure 3.
Boxplot of time to positivity in Staphylococcus aureus bacteremia episodes from 2011 to 2018 and 2019 to 2021, respectively.
See this image and copyright information in PMC

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