Performance of PCR/electrospray ionization-mass spectrometry on whole blood for detection of bloodstream microorganisms in patients with suspected sepsis

Blood culture (BC) often fails to detect bloodstream microorganisms in sepsis. However, molecular diagnostics hold great potential. The molecular method PCR/electrospray ionization-mass spectrometry (PCR/ESI-MS) can detect DNA from hundreds of different microorganisms in whole blood. The aim of the present study was to evaluate the performance of this method in a multicenter study including 16 teaching hospitals in the USA (n=13) and Europe (n=3). First, on 2,754 contrived whole blood samples, with or without spiked microorganisms, PCR/ESI-MS produced 99.1% true positive and 97.2% true negative results. Secondly, among 1,460 patients with suspected sepsis (sepsis-2 definition), BC and PCR/ESI-MS on whole blood were positive in 14.6% and 25.6% of cases, respectively, with the following result combinations: BC+/PCR/ESI-MS-, 4.3%; BC+/PCR/ESI-MS+, 10.3%; BC-/PCR/ESI-MS+, 15.3%; and BC-/PCR/ESI-MS-, 70.1%. Compared with BC, PCR/ESI-MS showed the following sensitivities (coagulase-negative staphylococci not included): Gram-positive bacteria, 58%; Gram-negative bacteria, 78%; and Candida species, 83%. The specificities were > 94% for all individual species. Patients treated with prior antimicrobial medications (n=603) had significantly increased PCR/ESI-MS positivity rates compared with patients without prior antimicrobial treatment, 31% vs 22% (p<0.0001), with pronounced differences for Gram-negative bacteria and Candida species. In conclusion, PCR/ESI-MS showed excellent performance on contrived samples. On clinical samples, it showed high specificities, moderately high sensitivities for Gram-negative bacteria and Candida species, and elevated positivity rates during antimicrobial treatment. These promising results encourage further development of molecular diagnostics on whole blood for detection of bloodstream microorganisms in sepsis.
Funding Agencies:Ibis Biosciences, a division of Abbott Abbott LaboratoriesCepheid ContraFect Nabriva Therapeutics AG Lajolla Pharmaceuticals Alere Corporation Spectral Diagnostics Ferring Pharmaceuticals Inflammix VICTASm Sanofi Pasteur Inc. Curetis GmbH PfizerMerck & CompanyCidara Therapeutics Inc. Shire Aridis Pharmaceuticals Inc. Epigenomics Inc. Roche Holding GenentechFinch Therapeutics Seres Therapeutics Inc. Diasorin Molecular Janssen Research and Development NeuMoDx Molecular Iterum Therapeutics International