Time to blood culture positivity (TTP) provided reliable information on the risk for infective endocarditis (IE) in patients with Staphylococcus aureus bacteraemia, according to study data published in Clinical Microbiology and Infection.

TTP is a readily available parameter in automated blood culture systems and provides useful information, as a short TTP likely reflects a more virulent infection and/or a high bacterial load. TTP data from a multicenter prospective cohort study of adult patients with S aureus bacteraemia from 4 centers in France between 2009 and 2011 was used to study the associations between TTP and definite IE.

A total of 587 patients with a mean age of 65.3±16.3 were included in the study; 71.6% were men, 20.6% died, and 7.2% had definite IE. Median TTP of first positive blood cultures was 13.7 h (interquartile range, 9.9-18) and 30-day mortality was associated with TTP ≤13.7 h (25.1% vs 16.1%, P =.02), old age, McCabe score, methicillin-resistant infection, liver disease, stroke, pneumonia, and high C-reactive protein measurement. IE was more common in the first and last quartiles of TTP; TTP <10 hours (11.5%) and TTP ≥18 hours (5.5%) respectively, (P =.002).

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The analyses of risk factors for IE were limited by small sample sizes in this study and by the use of two different blood cultures, potentially biasing results. Also, the volume of blood inoculated into blood culture bottles was not monitored, which could have a strong impact on both pathogen detection and TTP.

The investigators concluded that patients with a short TTP are at higher risk for early death and should therefore be more closely monitored and more aggressively treated than their counterparts. Further, they believe that the results demonstrate the value of developing a clinical use for TTP in the management of patients with S aureus bacteraemia.

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Siméon S, Moing VL, Tubiana S, et al. Time to blood culture positivity: an independent predictor of infective endocarditis and mortality in patients with Staphylococcus aureus bacteraemia [published online July 20 2018] Clin Microbiol Infect. doi:10.1016/j.cmi.2018.07.015