Background: Staphylococci are opportunistic pathogens and a major cause of both nosocomial and community-acquired bloodstream infections (BSI). Compared to the existing BIOFIRE® FILMARRAY® Blood Culture Identification (BCID) Panel, the updated BioFire BCID2 Panel contains an assay with expanded coverage for Staphylococcus species. Also, alongside an updated Staphylococcus aureus assay, the BCID2 Panel includes assays for key coagulase-negative staphylococci (CoNS) like Staphylococcus epidermidis, and Staphylococcus lugdunensis. Revised algorithms, facilitated by a new assay that identifies the insertion site of the staphylococcal cassette chromosome mec in S. aureus, aid accurate reporting of methicillin-resistant S. aureus (MRSA). Here, we evaluate the coverage and performance of these assays and associated algorithms.
Methods: Coverage and performance were evaluated using sequence data available for 72/77 species/subspecies, 107 Staphylococcus isolates and 1074 residual positive blood cultures (PBC) collected prospectively from 9 clinical sites. For pathogen identification from residual PBC, the reference method was microbial culture performed at clinical sites. The Xpert MRSA/SA BC test (Cepheid, Inc.) and phenotypic susceptibility testing were used as reference methods for MRSA.
Results: In silico assessment predicts reactivity for 66/72 staphylococci compared to ~40 species by the BCID Panel. During analytical testing, the Staphylococcus species assay also detected 103/107 isolates. Specific assays for S. aureus, S. epidermidis, and S. lugdunensis were reactive to all relevant isolates. At least one Staphylococcus species was reported in 472/1074 (44%) samples enrolled in the prospective clinical study; the BIOFIRE BCID2 Panel accurately identified 99.8% of these. The BIOFIRE BCID2 Panel MRSA results were 100% concordant with phenotypic results and 95.4% concordant with Xpert MRSA/SA BC test. In addition, the algorithm accurately identified the absence of MRSA in 3/3 cases where methicillin-susceptible S. aureus was present with methicillin-resistant S. epidermidis (MRSE) in the PBC.
Conclusions: The BIOFIRE BCID2 Panel assays for S. aureus, S. epidermidis, S. lugdunensis, and Staphylococcus spp. are highly inclusive of clinically relevant staphylococci. The high accuracy of the MRSA detection algorithms are anticipated to assist in implementation of effective treatment plans and antibiotic stewardship.
Data presented are from assays that have not been cleared or approved for diagnostic use.