P-63. Direct Identification of Gram-Negative Bacteria Culture: Analytical and Clinical Performance of a Multi-pathogen Molecular Assay

TL;DR

A new molecular test rapidly and accurately identifies gram-negative bacteria in blood cultures, improving diagnosis of bloodstream infections.

Contribution

The LIAISON PLEX® assay introduces a fast, automated, multi-pathogen molecular method for gram-negative bacteria identification in blood cultures.

Findings

The assay achieved 100% positivity for gram-negative bacteria and 0% false positives in negative cultures.

Clinical performance showed high Positive and Negative Percent Agreement for most pathogens, including resistance markers.

Commonly identified pathogens were Escherichia coli and Klebsiella pneumoniae in prospective samples.

Abstract

Bloodstream infection (BSI) is a critical condition requiring prompt diagnosis and treatment. This study evaluated the LIAISON PLEX® Gram-Negative Blood Culture Assay, a multi-target molecular panel for rapid and accurate identification of gram-negative (GN) bacteria grown in blood culture specimens. The panel’s analytical and clinical performance was compared to standard culture and automated methods to assess its effectiveness as a faster, sensitive adjunct.

The assay was performed directly on blood culture specimens positive for gram-negative bacteria. A 300 µL aliquot was processed in a single-use cartridge, utilizing NanoGrid Technology for rapid and direct detection without the need for target amplification. The fully automated LIAISON PLEX® system extracts nucleic acid and hybridizes it to a microarray with probes for 19 bacteria and 8 resistance genes, using gold nanoparticle chemistry with silver-enhanced signal amplification.

The assay showed 100% positivity for GN bacteria and 0% for negative blood cultures in a growth and detection study. It detected up to 21 representative strains across 13 blood culture media types and showed 100% inclusivity to 245 of 246 on-panel strains, including resistance markers (RM). The assay maintained sensitivity with low concentrations of on-panel GN organisms in the presence of high levels of other co-infecting GN or gram-positive bacteria.

Clinical performance was assessed in a multi-site study with 381 prospective, 231 pre-selected, and 746 contrived specimens. Among prospective samples, Positive Percent Agreement (PPA) ranged from 96.6% (Pseudomonas aeruginosa) to 100% (10 organisms including RM) excluding Acinetobacter spp., where the PPA was lower due to limited prevalence, and Negative Percent Agreement (NPA) ranged from 98.8% (E. coli) to 100% (20 organisms including RM). The common pathogens identified were Escherichia coli (47.2%) and Klebsiella pneumoniae (12.8%). In contrived specimens, PPA ranged from 97.2% to 100%, and NPA from 99.6% to 100%.

The LIAISON PLEX® Gram-Negative Blood Culture Assay offers fast and accurate identification of gram-negative pathogens, providing a reliable adjunct to culture-based methods for timely BSI management.

Seema Shaikh, MS, Diasorin: Employee Brian Bernier, PhD, Diasorin: Employee Megan Martinez, BS, Diasorin: Employee Jason Williams, BS, Diasorin: Employee Nicole Kroutter, MS, Diasorin: Employee Mahima Pancholi, MS, Diasorin: Employee Edward Sekinger, PhD, Diasorin: Employee Sundaresh Brahmasandra, PhD, Diasorin: Employee Janet Farhang, PhD, Diasorin: Employee|Diasorin: Employee