To compare the utility of a multiplex polymerase chain reaction system (SeptiFast) and blood cultures for detecting bacteria and fungi in blood samples from patients with severe sepsis or septic shock.


In a prospective observational study, whole blood samples for SeptiFast testing and for culture were collected on admission from all patients with severe sepsis or septic shock admitted to the intensive care unit between July 2011 and September 2012. SeptiFast results were compared with blood and other culture results.


The probability of at least 1 microorganism being isolated at 6 hours was 13-fold higher with the SeptiFast test than with blood cultures (relative risk, 13.5; 95% CI, 5.05–36.06). Unlike culture results, SeptiFast test results were not associated with previous antibiotic consumption. The median time to the first positive blood culture result was 17 hours; SeptiFast results were available in 6 hours. SeptiFast detected genetic material from potentially multiresistant microorganisms in patients whose blood cultures showed no growth at all.


The SeptiFast test provided quicker microbiological diagnosis and identified significantly more microorganisms than blood cultures did, particularly when samples were collected after antibiotic therapy had started or infections were due to resistant bacteria and yeast.

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