Evaluation of SeptiFast - a new commercially available broad-range real-time PCR assay for detection of bacteria and fungi in blood

G. Lisby, H. Westh

Author address: 

Hvidovre, DK


Introduction: Blood culture (BC) is the gold standard for detection of bacteraemia and fungaemia but has several limitations. False positive results due to contamination and false negative results due to e.g. antibiotic treatment at the time of sampling are well known problems. Nucleic acid target amplification (PCR) could potentially supplement traditional BC. Objective: To compare a new commercially available broad-range real-time PCR assay (SeptiFast) with BC for detection of bacteria and fungi in blood from patients with suspected sepsis or SIRS. SeptiFast detects a total of 23 pathogen species. Methods: A BC sample (32-40 ml) was obtained using sterile technique. Immediately after, a 5 ml blood sample was obtained for PCR. At the Department of Clinical Microbiology, Hvidovre Hospital, BC (BactAlert, BioMerioux) was performed according to standard operating procedures. PCR (SeptiFast, Roche Diagnostics) was performed according to the manufacturers' description using a MagNA Lyser and LightCycler 2.0 (Roche Diagnostics). Results: A total of 114 episodes (combined BC samples and PCR samples) were collected from 114 patients. 83 episodes were negative in both BC and PCR and 21 episodes were positive in one or both assays. 13 episodes were BC positive, yielding 13 BC isolates (positive rate for non contaminant BC: 7.9%). Two isolates were not included in the PCR panel and three isolates were considered as contamination. Of the remaining seven isolates available for direct comparison, PCR detected five. 15 episodes were PCR positive (positive rate for non contaminant PCR: 11.4%), detecting a total of 19 microorganisms. Two of the detected microorganisms were considered as contamination, six were also detected by BC, but 11 were not detected by BC. Of these 11 PCR ± BC- isolates, six were confirmed by culture of the same micororganism from a clinical relevant anatomical site and five could not be confirmed by culture. The combined tests had a positive rate for non-contaminants of 15.8%. In the six episodes positive by both PCR and BC, PCR would reveal species identification in approx 18 hours if performed on a daily basis. BC had an average delay of 2 days until Gram stain, and 3-4 days until species identification. Conclusion: This study shows SeptiFast PCR to be a valuable add-on to conventional BC for detection of bacteria and fungi in blood.

abstract No: 


Full conference title: 

16th European Congress of Clinical Microbiology and Infectious Diseases
    • ECCMID 16th (2006)