Sequential time to positivity of blood cultures can be a predictor of prognosis of patients with persistent Staphylococcus aureus bacteraemia

A short time to positivity (TTP) correlates with poor clinical outcome in patients with Staphylococcus aureus bacteraemia, but the association between sequential TTPs and the outcome of these patients is unclear. Sequential TTPs from patients with S.aureus bacteraemia persisting for >48h were analysed with respect to clinical parameters and patient outcome at a tertiary hospital. During the 5-year study period, 87 patients (9.2%; mean age of 64years) had persistent S.aureus bacteraemia, with an average Pittsburgh bacteraemia score of 2.7. Forty-eight patients (55%) had methicillin-resistant S.aureus infection, and 28 (32%) had nosocomial infection. The most common underlying disease was end-stage renal disease (43%). The most common type of infection was catheter-related infection (31%), followed by infective endocarditis (18%). The in-hospital mortality rate was 40%. Higher Pittsburgh scores (p0.005; OR1.37; 95%CI1.1-1.7) and a second TTP/first TTP ratio of <1.5 (p0.004; OR0.2; 95%CI0.07-0.6) were independent risk factors for mortality. Among patients receiving adequate empirical therapy, a second positive blood culture growing within 12h was more frequent in patients who finally died. Factors associated with a second TTP/first TTP ratio of <1.5 included older age (p0.02; OR0.96; 95%CI0.92-0.99) and inadequate empirical antimicrobial therapy (p0.01; OR3.53; 95%CI1.42-8.78). Among patients with persistent S.aureus bacteraemia, a second TTP/first TTP ratio of <1.5 is a predictor of poor outcome. Physicians should search for interventions guaranteeing that all patients with S.aureus bacteraemia receive adequate empirical therapy.