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Bloodstream infections: fast diagnosis using molecular tools

Analytical performance evaluation of the BIOFIRE® Blood Culture Identification 2 (BCID2) Panel

April 18 • P0174

B. Flaherty1, M. Buccambuso1, N. Francis1, J. Manwaring1, J. Southwick1, J. Larsen1, J. Arce1, K. Mylroie1, E. Ong1, K. Ekins1, J. Gann1, T. Dawson1, H. Burton1, C. Russell1, J. Brooksby1, S. Hansen1, C. Dubost2, C. Cantrell3, E. Amiott1

1) BioFire Diagnostics, LLC, Salt Lake City, UT, USA
2) BioMérieux, SA, Grenoble, France
3) BioMérieux, Inc, Durham, USA

Background: The BIOFIRE® FILMARRAY® Blood Culture Identification 2 Panel is the next-generation BIOFIRE® system for rapid detection of bacteria, yeast and select antimicrobial resistance (AMR) genes in positive blood cultures. Analytical studies evaluated compatibility of the panel with different bottle types and culture systems, established the limit of detection (LoD), reactivity, and specificity of the assays, and assessed the robustness of results from samples containing potentially interfering substances.

Materials/methods: Blood culture system compatibility was evaluated by determining organism titers and panel test results from seeded positive blood cultures grown to positivity (and 24 hours post-positivity) in 13 different bottle types incubated in 2 continuously monitoring blood culture systems. Limits of detection were estimated by serial dilution of contrived samples, and LoD was subsequently confirmed by detection in a minimum of 95% of 20 or more replicates. Analytical reactivity and specificity were evaluated by testing over 450 on-panel isolates and 200 off-panel species, and panel robustness was assessed by testing low-level analytes in the presence of over 50 substances. All testing used Investigational Use Only kits.

Results: Titers in positive blood cultures from different systems (0-24 hour post-positivity) ranged from ~3.0E+05 – 4.5E+07 CFU/mL for yeast and ~3.0E+06 – 3.0E+09 CFU/mL for bacteria, which are ≥30-fold higher than the detection capability of the assays (LoD of 5.0E+02 – 1.0E+04 CFU/mL for yeast and 1.0E+03 – 1.0E+06 CFU/mL for bacteria). Testing near LoD demonstrated assay reactivity with a diverse collection of species and AMR genes in isolates from around the globe, and the panel provided reliable results in the presence of potentially interfering substances. Testing at high concentration (>1.0E+08 CFU/mL) demonstrated few instances of cross-reactivity with unrelated off-panel species.

Conclusions: The BIOFIRE® BCID2 Panel assays are robust, specific, and reactive with expected diversity of bacterial and yeast causes of bloodstream infection. Rapid identification of organisms in blood culture, along with information about antimicrobial resistance gene status for select microorganisms, may aid in timely diagnosis and appropriate treatment decisions for bloodstream infections.

The panel has not been cleared for diagnostic use by the FDA or other regulatory entities.

filmarray

BCID2 Panel

Paper poster