Relevance of testing for microbial DNA in critically ill patients

Abstract number: P1999

Bloos F., Regueiro J., Bruin-Buisson C., Sachse S., Hinder F., Becker K., Straube E., Reinhart K., Bauer M.

Objectives: Blood culture is an important method for identifying the underlying microorganism causative of sepsis. However, blood culture results may take up to 48 hours possibly delaying appropriate antibiotic therapy. The goal of this study was to evaluate the performance of microbial DNA testing in the blood compared to blood culture in critically ill patients.

Methods: The study was performed in 3 centres. Inclusion criteria were either severe sepsis (sepsis group) or elective surgery without evidence of infection (control group). A blood culture (BC) was obtained and 10 ml EDTA blood were simultaneously taken by sterile venous puncture. Further samples were taken on max. 3 consecutives days. Microbial DNA was measured by PCR with the LightCycler System 2.0 (Roche Diagnostics).

Results: 142 sepsis patients (236 samples) and 63 control patients (111 samples) have been included. Control patients had 3.6% positive PCRs and 4.5% positive BCs (sensitivity 0; specificity 0.95). 34.7% of PCRs were positive in the sepsis group compared to 16.5% of BCs (sensitivity 0.79; specificity 0.74). Procalcitonin values at diagnosis of sepsis were higher in PCR/BC positive than in PCR/ BC negative patients (figure).

Conclusion: Concordance between blood culture and PCR results is very good in patients without evidence of infection. In patients with sepsis, PCR showed positive results more often than the blood culture. PCR-based culture-independent detection correlated well with disease severity as reflected in plasma procalcitonin levels. In the light of shorter time to result, PCR based detection might trigger appropriate antibiotic therapy in the early therapeutic window which determines prognosis of the patient with severe sepsis.

Acknowledgements: This study was sponsored by Roche Diagnostics, Penzberg, Germany