Improving the Diagnosis of Bloodstream Infections: PCR Coupled with Mass Spectrometry

Jordana-Lluch, Elena; Giménez, Montserrat; Quesada, M. Dolores; Ausina, Vicente; Martró, Elisa

In the Magicplex Sepsis assay, three PCR reactions are necessary to achieve the identification at the species level of the pathogen. First, a conventional PCR amplification step is performed. In this step, primers designed to amplify genomic material from 91 microorganisms (85 bacteria, five species of Candida, and Aspergillus fumigatus) and three resistance genes (methicillin resistance gene mecA and vancomycin resistance genes vanA and vanB) are used. A real-time PCR is then carried out in a screening step for identification of the group or genera level of pathogens present. Finally, a second real-time PCR is performed to achieve the identification at species level. Identification of 21 bacterial species, five Candida species, and Aspergillus fumigatus is possible. For the DNA extraction, 1 mL of whole blood is used and human DNA is removed prior to the lysis of microorganisms. The time-to-result of this assay is 6 hours. To our knowledge, only one study using this approach for the molecular diagnosis of sepsis has been published [15] . The sensitivity and specificity were reported to be 65.0% and 92.0%, respectively.