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Bloodstream infections: fast diagnosis using molecular tools

Comparison of Three Rapid Diagnostic Blood Culture Identification Panels for Gram-Negative Bloodstream Infections

April 18 • P0176

J. K. Johnson1, R. D. Smith1, S. Hitchcock1, K. C. Claeys2

1) University of Maryland School of Medicine, Baltimore, United States
2) University of Maryland School of Pharmacy, Baltimore, United States

Background: To best manage bloodstream infections, rapid diagnostic testing (RDT) has become critical in improving patient outcomes. The primary objective of this study was to assess and compare three gram-negative rapid diagnostic blood culture panels.

Methods: Retrospective study from 8/2018 to 11/2019 at the University of Maryland Medical Center. Positive blood cultures from each patient were tested for gram-negatives using Verigene® Blood Culture, BIOFIRE® Blood Culture Identification panel (BCID), and the new BIOFIRE® Blood Culture Identification Panel 2 (BCID2; Research-Use-Only) panels were compared to each other against standard culture and antibiotic susceptibility testing results from VITEK® 2 MS.

Results: 103 positive gram-negative blood cultures were used in this study. P. multocida (2), Burkholderia spp. (1), P. lautus (1), P. intermedia (1), Achromobacter (2), P. pseudoalcaligenes (1) and Psychrobacter (1) were not on any of the panels so they were excluded. The Verigene® panel does not include B. fragilis (1), and S. marcescens (10) so they were excluded (82/103 included). Among included organisms, Verigene® failed to identify 1 K. pneumoniae for an overall positive agreement of 99% (81/82). BCID panel also does not include S. maltophilia (1), B. fragilis (1), Citrobacter (1) and A. junii (1) so those were excluded (90/103 included). BCID misidentified 3 E. coli, 2 E. cloacae complex, 1 Acinetobacter spp., 2 Proteus spp., 1 K. oxytoca, 2 S. marcescens, and 1 K. pneumoniae for 87% (78/90) overall positive agreement. BCID2 (RUO) had a positive agreement of 96% (89/93) missing  2 E. coli, 1 S. maltophilia, and 1 E. cloacae complex. Citrobacter (1) samples were not included in BCID2 analysis as it is not on the panel (93/103 included). Verigene® and BCID2 identified the 6 CTX-M. CTX-M is not on the BCID panel and, therefore, was not detected.

Conclusions: Verigene® and BCID2 have high percent positive agreements. BCID2 is an improvement on BCID as it has increased positive agreement and the panel includes more organisms. BCID2 has the most extensive gram-negative panel of the three. Local epidemiology of bloodstream infections should be considered when laboratories are determining optimal use of rapid detection testing.

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BCID2 Panel

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