1858. Sequential Time to Positivity as a Prognostic Indicator in Staphylococcus aureus bacteremia

Abstract

Abstract Background The role of sequential blood culture time to positivity (TTP) as a surrogate marker for bacterial load and as a prognostic indicator in S. aureus bacteremia (SAB) is not well established in the literature. Methods We performed a single healthcare system, multi-site, retrospective review of adult patients with positive blood culture for S. aureus between January 2019 and December 2019. Sequential TTP was defined as the TTP of the first subsequent blood cultures obtained from patients with SAB for at least 24 hours. We adapted the previously described TTP ratio of < 1.5 as the cut-off for study groups. Infective endocarditis (IE) was defined according to modified Duke’s criteria. High-grade bacteremia was defined as the growth of the organism in two or more sets of blood cultures or growth in >50% of all bottles collected. Descriptive, comparative statistics and survival analysis were performed using Python 3 and IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY: IBM Corp. Results A total of 602 patients with SAB were identified, and 186 patients who met the study criteria were included. Sixty-nine patients (37%) were female, and the mean age was 63.6 years. Patients with initial TTP < 12 hours had higher 30-day and 90-day mortality than those with initial TTP ≥ 12 hours. Patients with TTP ratio of > 1.5 had higher rates of cardiac prosthetic device (30 [26.1%] vs. 9 [12.7%], p = .03) and high-grade bacteremia (106 [92.2%] vs. 56 [78.9%], p = .01). In univariate analysis, history of myocardial infarction, cardiac prosthetic device, and findings of high-grade bacteremia and native valve vegetation in echocardiogram were significant predictors for a TTP ratio of < 1.5. In multivariate analysis, native valve vegetation (OR 2.4; 95% CI 1.2-4.84), and high-grade bacteremia (OR, 0.3; 95% CI, 0.13- 0.77) were independent predictors (Table 1 and 2). No differences in 30- day or 90-day survival based on the TTP ratio were seen (Figure 1). Figure 1.Kaplan-Meier (KM) curves and log rank test results based on time to positivity (TTP) of initial blood cultures and TTP ratio of sequential to initial blood culture The X-axis represents the days elapsed from the initial blood culture collection. Number of patients at risk and events are given below the x-axis for each group. 30-day and 90-day survival rates were significantly lower in patients with initial TTP of < 12 hours compared with those with ≥ 12 hours. There were no statistically significant differences in survival based on TTP ratio. Conclusion In patients with SAB, a second TTP to first TPP ratio of > 1.5 was associated with higher rates of presence of the cardiac prosthetic device and high-grade bacteremia. Initial TTP < 12 hours was associated with lower survival; however sequential TTP ratio didn’t predict mortality. Disclosures All Authors: No reported disclosures.