Objective 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. Methods 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. 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. Conclusions 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.

Most Escherichia coli resistant to quinolones are not haemolytic. The objective of this study was to determine the phylogroup, clonal relationship, mechanism of quinolone resistance and virulence factors in 70 haemolytic E. coli resistant to nalidixic acid. Sixty-six isolates contained the hlyA gene, belonged to phylogroup B2, and 61 of them presented low-level resistance to fluoroquinolones. Four isolates presented high-level resistance to fluoroquinolones, contained the clyA gene and were included in phylogroup D. One single isolate (phylogroup D, with low level resistance to fluoroquinolones) contained both cytotoxins.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-71) contains supplementary material, which is available to authorized users.