Optimized Use of the MALDI BioTyper System and the FilmArray BCID Panel for Direct Identification of Microbial Pathogens from Positive Blood Cultures

Abstract

Despite the current reliance on blood cultures (BCs), the diagnosis of bloodstream infections (BSIs) can be sped up using new technologies directly on positive BC bottles. Two methods (the MALDI BioTyper system and FilmArray BCID panel) are potentially applicable. In this study, we performed a large-scale clinical evaluation (1,585 microorganisms from 1,394 BSI episodes) on the combined use of MALDI BioTyper and FilmArray BCID compared to a reference (culture-based) method. As a result, 97.7% (1,362/1,394) of the BSIs were correctly identified by our MALDI BioTyper and FilmArray BCID-based algorithm. Specifically, 65 (5.3%) out of 1,223 monomicrobial BCs that provided incorrect or invalid identifications with the MALDI BioTyper were accurately detected by the FilmArray BCID; additionally, 153 (89.5%) out of 171 polymicrobial BCs achieved complete identification with the FilmArray BCID. Conversely, full use of the MALDI BioTyper would have resulted in the identification of only 1 causative organism in 97/171 (56.7%) of the polymicrobial cultures. By applying our diagnostic algorithm, the median time to identification was shortened (19.5 hours versus 41.7 hours with the reference method; P <0.001), and the minimized use of the FilmArray BCID led to significant cost savings. Twenty-six out of 31 microorganisms that could not be identified were species/genera not designed to be detected with the FilmArray BCID, indicating that subculture was not dispensable for a few of our BSI episodes. In summary, a fast and effective testing of BC bottles is realistically adoptable in the clinical microbiology laboratory workflow, although the usefulness of this testing for the management of BSIs remains to be established.