Sequential Time to Positivity as a Prognostic Indicator in Staphylococcus aureus Bacteremia

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Clinical Diagnostics

Background:

• Staphylococcus aureus bacteremia (SAB) poses significant risks, including mortality and adverse outcomes.
• Sequential blood culture time to positivity (STTP) and time to positivity (TTP) ratio are potential biomarkers for SAB severity.
• Previous research defined a TTP ratio threshold of 1.5 for predicting adverse outcomes.

Purpose of the Study:

• To identify factors associated with STTP in SAB patients.
• To validate the TTP ratio threshold of 1.5 in predicting adverse disease outcomes and mortality in SAB.
• To explore the clinical utility of STTP in identifying patients at higher risk for native valve endocarditis (NVE).

Main Methods:

• An observational study was conducted on adult patients diagnosed with SAB.
• The TTP ratio was calculated by dividing the TTP of the second blood culture by that of the first.
• Statistical analyses were performed to correlate STTP, TTP ratio, methicillin susceptibility, and adverse outcomes like NVE.

Main Results:

• Of 186 patients, MRSA-infected patients exhibited significantly shorter STTPs and lower TTP ratios compared to MSSA.
• A TTP ratio of ≤1.5 was significantly correlated with a higher rate of NVE (OR, 2.65).
• Patients with an initial TTP <12 hours and a TTP ratio ≤1.5 showed the highest prevalence of NVE.

Conclusions:

• STTP is influenced by the methicillin susceptibility of the Staphylococcus aureus isolate.
• The STTP and TTP ratio show potential clinical utility in identifying SAB patients at higher risk for NVE.
• Prospective studies are necessary to validate these findings and their clinical application.