Abstract
ABSTRACTRapid pathogen characterization from positive blood cultures (BC) can improve management of patients with bloodstream 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 expanded-spectrum β-lactamase (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 the standard of care (SOC) in 159/180 (88.3%) BCs; 68/74 (91.9%) and 71/74 (96.0%) of all samples growing monobacterial, Gram-positive or Gram-negative pathogens, respectively, were identified, in agreement with SOC results. Nonconcordance was related to the detection of additional pathogens by the BCID2 assay (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 polymicrobial BC specimens. BCID2 identified the presence of blaCTX-M-carrying species in 12 BC specimens but failed to predict third-generation cephalosporin resistance in four isolates exhibiting independent cephalosporin resistance mechanisms. Carbapenem resistance related to the presence of blaVIM-2 or blaOxa-48-like was correctly predicted in two isolates. In conclusion, the 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.
Highlights
Rapid pathogen characterization from positive blood cultures (BC) can improve management of patients with bloodstream infections (BSI)
Blood cultures qualified for BCID2 analysis if drawn from patients hospitalized in the intensive care unit/ emergency department, the age of the patient was $18 years, no positive blood cultures from the patient were available within the past 7 days from which pathogens of the same Gram staining behavior had been cultivated, and time to positivity (TTP) was,20 h
In 31 polymicrobial specimens, a total of 65 isolates were detected by standard of care (SOC), of which 62 were BCID2 on the panel
Summary
Rapid pathogen characterization from positive blood cultures (BC) can improve management of patients with bloodstream infections (BSI). Available molecular assays marketed for direct species identification usually provide information on some resistance markers (e.g., mecA, vanA-vanB, and expanded-spectrum b-lactamase [ESBL]and carbapenemase-encoding genes) and enable short turnaround and hands-on times [7, 8]. The BioFire FilmArray blood culture ID (BCID) assay, a highly multiplexed, singlepouch PCR kit that identifies 24 pathogens and gives additional insight into some important resistance genes (mecA, vanA-vanB, and blaKPC), proved to be a powerful tool [9, 10]. The recently released BCID2, an update to the original BCID, identifies 33 species, including a new distinction between Enterococcus faecalis and E. faecium It analyzes 10 genetic resistance markers, including common carbapenemase-encoding genes (i.e., blaKPC, blaIMP, blaNDM, blaOXA-48-like, and blaVIM), the most common ESBL gene (blaCTX-M) [11], and a genetic marker for colistin resistance (mcr-1). We evaluate the BCID2 real-life performance in a tertiary care hospital in Germany by comparison of identification results of 180 blood cultures from patients with a bloodstream infection (BSI) against our current culture-based standard of care (SOC) and an identification employing MALDI-TOF mass spectrometry
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