Objective:

To assess whether the clearance duration of Staphylococcus aureus bacteraemia measured by blood culture (BC) or T2Bacteria (T2B) better identifies patients at risk for deep-seated or metastatic infection and poor clinical outcomes, including in-hospital mortality.

Approach:

• Study Design: A prospective observational diagnostic study conducted at Klinik Favoriten hospital in Vienna, Austria, from October 2022 through February 2025.
• Participants: Adults aged 18 years or older with S. aureus detected in a blood culture within 24 hours before study inclusion were eligible. A total of 56 hospitalized patients were enrolled.
• Intervention: Blood cultures and T2B testing were performed at study inclusion and repeated every 48 hours until both methods were negative. Clearance duration was defined as the time from the first positive study blood culture to the last documented positive blood culture or T2B result.
• Data Collection: Demographic and baseline clinical data were collected at enrollment. Deep-seated or metastatic infection, in-hospital mortality, and ICU admission were assessed at hospital discharge or death, with 30- and 90-day mortality and hospital readmission evaluated during follow-up.

Key Findings:

• T2B remained positive significantly longer than blood culture, with a mean time to the last positive result of 3.9 days versus 1.7 days, respectively.
• Patients with prolonged T2B clearance of more than 3 days had higher rates of deep-seated or metastatic infection than those with clearance within 3 days (57.1% vs 8.6%; P < 0.001) and higher in-hospital mortality (42.9% vs 14.3%; P = 0.038).
• T2B clearance duration showed significantly better predictive performance than blood culture clearance duration for deep-seated or metastatic infection (AUC, 0.798 vs 0.647; P = 0.042) and for the combined endpoint of deep-seated or metastatic infection and/or in-hospital mortality (AUC, 0.822 vs 0.663; P = 0.011). Differences between T2B and blood culture for mortality alone were not statistically significant.

Interpretation:

Prolonged T2B positivity was associated with deep-seated or metastatic infection and in-hospital mortality, and T2B clearance duration provided better prognostic discrimination than blood culture for deep-seated or metastatic infection. Because treating physicians were blinded to T2B results, the findings establish prognostic associations rather than demonstrating that T2B-guided management improves outcomes.

Limitations:

• The study was conducted at a single center and included only 56 patients. The small number of patients with prolonged bacteraemia by blood culture may have reduced statistical power, and the absence of adjustment for multiple comparisons raises the possibility of type I error.
• Enrollment constraints, including the requirement for identification within 24 hours of a positive blood culture and weekday-only notification of the study team, may have introduced selection bias and limited generalizability. The T2Bacteria Panel is also no longer commercially available, limiting direct clinical implementation.

Conclusion:

Prolonged T2B positivity identified patients at increased risk for deep-seated or metastatic infection and was superior to blood culture clearance duration for predicting these complications in S. aureus bacteraemia. Serial molecular detection of bacterial DNA may therefore provide prognostic information beyond conventional blood cultures and help identify patients who warrant intensified evaluation for persistent infectious foci.