Chip-Based Molecular Evaluation of a DNA Extraction Protocol for Species from Positive Blood Cultures.

The diagnosis of bloodstream infection (BSI) may rely on a PCR-based analysis of a positive blood culture (PBC) obtained from the patient at the time of BSI. In this study, a yeast DNA extraction protocol for use on PBCs was developed and evaluated with the molecular mouse (MM) yeast blood (YBL) chip-based PCR assay, which allowed us to detect nine medically relevant species. We studied 125 simulated or clinical PBCs for species. A positive correlation between the DNA concentration and colony-forming unit count was found for simulated (Spearman's ρ = 0.58; < 0.0001) and clinical (Spearman's ρ = 0.23, = 0.09) PBCs. The extracted DNA yielded positive results with the MM YBL chip assay that agreed with the species-level identification results for 63 (100%) of 63 isolates from simulated PBCs and 66 (99.5%) of 67 isolates from clinical PBCs. The false-negative result was for one isolate that grew together with in PBC. None of the 30 ()-negative clinical BCs included as negative controls yielded a positive result with the MM YBL chip assay. Our DNA extraction protocol for the species couples efficiency and simplicity together. Nevertheless, further studies are needed before it can be adopted for use with the MM YBL chip assay.