Performance of the LIAISON PLEX gram-negative blood culture assay for identifying bacterial pathogens and resistance genes in blood cultures

ABSTRACT Gram-negative bacteria cause potentially life-threatening bloodstream infections worldwide. Delayed initiation of optimal antimicrobial therapy worsens health outcomes. Molecular assays characterize bloodstream pathogens and their antimicrobial resistance (AMR) genes faster than gold-standard culture-based methods. This multi-site study evaluated the performance of the automated multiplex LIAISON PLEX Gram-Negative Blood Culture (BCN) Assay (Luminex Corporation), which tests positive blood cultures for 19 gram-negative bacteria and 8 AMR genes, in approximately 2 h. Samples included 351 prospectively collected, 231 pre-selected, and 746 contrived specimens. For combined prospective plus pre-selected specimens, sensitivity/positive percent agreement was 90.0%–100% for 18/19 on-panel bacterial targets, and 97.8%–100% for detected AMRs. Specificity/negative percent agreement was ≥99.3% for all 19 bacterial targets, and ≥99.6% for AMRs. Common pathogens in prospective samples were Escherichia coli (51.4%), Klebsiella pneumoniae (12.9%), and Pseudomonas spp. (8.3%). Contrived specimen sensitivity and specificity both averaged >99.8% across all assay targets. All 13 tested bottle/matrix types gave 100% detection of 21 targetable pathogens tested. The assay identified a cumulative 246 reportable on-target strains, indicating broad inclusivity. Cross-reactivity was observed with 17/41 off-panel gram-negative bacteria; no cross-reactivity was observed with 61 gram-positive bacteria or 11 fungal pathogens. Low concentrations of 10 on-panel bacteria were detectable alongside high concentrations of 9 other on-panel targets or 7 gram-positive potential confounders. Six potential interfering substances in blood culture bottles had no impact on the detection of four representative on-target bacteria. Reproducibility approached 100% both within-lab and across sites. The LIAISON PLEX BCN Assay provides excellent sensitivity and specificity for quickly characterizing gram-negative bacterial pathogens and their resistance genes in positive blood culture specimens. IMPORTANCE Bloodstream bacterial infections may cause serious illness and death. Successful treatment demands rapid pathogen identification so the optimal antibiotic therapy can be initiated. Blood culture is standard for confirming bloodstream infection but may not provide detailed pathogen information in a timely manner. The LIAISON PLEX Gram-Negative Blood Culture assay quickly analyzes blood cultures to identify 19 pathogenic gram-negative bacteria and 8 associated antibiotic drug resistance genes. The LIAISON PLEX BCN Assay demonstrated a high degree of reliability in rapidly characterizing the infective pathogen and associated resistance genes in blood cultures from 582 patients with demonstrated gram-negative bloodstream infection. Assay performance was confirmed in 746 contrived samples in which samples were spiked with different gram-negative bacteria.