Clinical Performance of the Novel GenMark Dx ePlex® Blood Culture ID Gram-Positive Panel

Background: Rapid identification from positive blood cultures is standard of care (SOC) in many clinical microbiology laboratories. The GenMark Dx ePlex® Blood Culture ID Gram Positive (BCID-GP) Panel is a multiplex nucleic acid amplification assay based on competitive DNA hybridization and electrochemical detection using eSensor® technology. This multicenter study compared the Investigational Use Only (IUO) BCID-GP Panel to comparator methods for identification of 20 gram-positive bacteria, four antimicrobial resistance genes, and both Pan Candida and Pan Gram-Negative targets that are unique to the BCID-GP Panel. Materials and Methods: Ten microbiology laboratories throughout the USA collected residual, de-identified positive blood culture samples for analysis. Five laboratories tested both clinical and contrived samples with the BCID-GP Panel. Comparator identification methods included each laboratory9s SOC, which included MALDI-TOF MS and automated identification systems, and targeted PCR/qPCR with bidirectional sequencing. Results: A total of 2,342 evaluable samples (1,777 clinical, 565 contrived) were tested with the BCID-GP Panel. The overall sample accuracy for on-panel organisms was 89% before discordant resolution. For pathogenic gram-positive targets (Bacillus cereus group, Enterococcus, E. faecalis, E.faecium, Staphylococcus, S. aureus, S. epidermidis, S. lugdunensis, Listeria, L. monocytogenes, Streptococcus, S. agalactiae, S. anginosus group, S. pneumoniae, S. pyogenes), positive percent agreement (PPA) and negative percent agreement (NPA) ranged from 93.1%-100% and 98.8%-100%, respectively. For contamination rule-out targets (Bacillus subtilis group, Corynebacterium, Cutibacterium acnes, Lactobacillus, Micrococcus), PPA and NPA ranged from 84.5%-100% and 99.9%-100%, respectively. Positive percent agreement and NPA for the Pan Candida and Pan Gram-Negative targets were 92.4%, 95.7% and 99.9%, 99.6%, respectively. The PPA for each resistance marker was mecA 97.2 %, mecC 100%, vanA 96.8%, and vanB 100%. Negative percent agreement ranged from 96.6%-100%. Conclusion: The ePlex BCID-GP Panel compares favorably to SOC and targeted molecular methods for the identification of twenty gram-positive pathogens and four antimicrobial resistance genes in positive blood culture bottles. This panel detects a broad range of pathogens and mixed infections with yeast and gram-negative organisms from the same positive blood culture bottle.