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Time to positivity in blood cultures of patients with Staphylococcus aureus bacteraemia: possible correlation with the source of infection

Abstract number: 1733_435

Ezpeleta C., Alava J.A., Ezpeleta G., Cabezas V., Atutxa I., Busto C., Gomez E., Unzaga J., Cisterna R.

Objective: The aim of this study is to asses if the time between blood culture incubation and growth detection in Staphylococcus aureus bacteraemia measured by the time to positivity in a continuously monitored system correlates with the source of infection and the outcome of the patient.

Methods: We performed a retrospective, observational study involving adult inpatients who had S. aureus bacteraemia between 1 October 2002 and 30 September 2006 at a University hospital. Measurements included time to positivity in initial blood culture series, duration of bacteraemia episode, gender, age, rate of metastatic infection, and outcome.

Results: A total of 211 S. aureus bacteraemias (>1 positive blood culture result) were reported for patients with ages between 7–94 years (median age, 69 years); 21 (9.95%) bacteraemias were associated with endocarditis. The microbiological documentation of the source of bacteraemia was achieved only in half of the cases. The mortality rate was 21.8%.

The duration of bacteraemia was 1–60 days (median duration, 8 days; average duration 9.8 days). The time to positivity ranged from 40 minutes to 3 days (median time to positivity, 11.19 h) and was significantly shorter for patients with an endovascular source of infection (endocarditis or catheter related infection), compared with the other sources of bacteraemia (p = 0.001). Analysis of the data using logistic regression revealed that a time to positivity shorter than 10 hours, was an independent predictor of an endovascular source of infection and outcome of the patient.

Conclusions: Time to positivity in S. aureus bacteraemia may provide useful diagnostic and prognostic information. Growth of S. aureus within 10 h after the initiation of incubation may identify patients with a high risk of fatal infection. Meanwhile due to the reduced number of cases further studies are needed.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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