Usefulness of Biofire FilmArray BCID2 for blood culture processing in clinical practice.

Rapid pathogen characterization from positive blood cultures (BC) can improve management of patients with blood stream infections (BSI). The FilmArray blood culture identification (BCID) assay is a molecular test approved for direct identification of BSI causing pathogens from positive BC. A recently updated version of the panel (BCID2) comprises improved species identification characteristics, and allows for the detection of one ESBL- and several carbapenemase-encoding genes. Here, the clinical performance of the BCID2 assay for species identification in 180 positive BCs was evaluated. BCID2 results were concordant with standard of care (SOC) in 159/180 (88.3%) BCs. 68/74 (91.9%) and 71/74 (96.0%) of all samples growing mono-bacterial, Gram-positive or Gram-negative pathogens, respectively, were identified in agreement with SOC results. Non-concordance was related to the detection of additional pathogens by the BCID2 (n= 4), discrepant species identification (n= 4), or failure of BCID2 to detect on-panel pathogens (n= 1). A number (12/31; 38.7%) of discordant results became evident in poly-microbial BC specimens. BCID2 identified presence of bla CTX-M carrying species in 12 BC specimens, but failed to predict a third-generation cephalosporin resistance in four isolates exhibiting independent cephalosporin-resistance mechanisms. Carbapenem-resistance related to the presence of bla VIM-2 or bla Oxa-48-like was correctly predicted in two isolates. In conclusion, BCID2 assay is a reliable tool for rapid BC processing and species identification. Despite inclusion of common ESBL- or carbapenemase-encoding markers, the multifactorial nature of β-lactam resistance in Gram-negative organisms warrants combination of BCID2 with (rapid) phenotypic susceptibility assays.