Introduction: Traditional blood cultures (BC) have well known limits: time to first results (48 hours) and sensitivity (only 15-25%). New methods are needed and molecular biology seems to offer interesting opportunities. Our evaluation was a part of an european multicenter study. Objectives: The aim of the study was to evaluate a new PCR based molecular assay (25 pathogens detected in six hours) and its clinical impact in comparison with BC results. Methods: BC were performed by BactAlert System (BioMerieux) and incubated for 7 days. The SeptiFast test was performed on LightCycler 2.0 (Roche Diagnostics). The principle of the method will be explained. PCR samples were collected after BC from patients fulfilling the SIRS criteria. For each patient a data set was collected: clinical and laboratory data, microbiological results from all specimens. The results were finally discussed by a group of 4 clinicians. Results: A total of 114 samples were collected from 74 patients. 73 samples were BC and PCR negative. Positive rate for BC was 11.4% and for PCR 27.2%. 13 samples were BC and PCR positive. 4 were BC positive for coagulase-negative staphylococci (CNS) but PCR negative. 24 were BC negative but PCR positive: 6 of them detected only CNS; 11 were of clinical importance. PCR was able to detect: a) Streptococcus viridans group in a patient with endocarditis; b) Staphylococcus aureus in a patient with pancreatitis; and c) S. aureus in a patient with spondylodiscitis.The PCR results were available after 16-30 hours, the biopsy and valve culture results were reported after 5-7 days. In 7 samples PCR detected a pathogen (Aspergillus fumigatus, Stenotrophomonas maltophilia, Escherichia coli, S. aureus, Enterococcus faecalis) but there were no additional data that confirmed these results. Conclusion: In our study PCR detect all BC positive samples and it was the best test able to help with the right diagnosis for 3 patients. PCR requires a DNA-free workflow and well-trained workers, otherwise results could be misleading by the detection of environmental DNA.PCR is faster and more sensitive than BC. Further studies will show the best use of this interesting new method.
Full conference title:
16th European Congress of Clinical Microbiology and Infectious Diseases
- ECCMID 16th (2006)