Performance of the ePlex Gram Positive Blood Culture ID Panel on Routine and Complex Blood Cultures Elizabeth Gaston, MD 1, Priyanka Uprety, PhD1, Kevin Alby, PhD1 1Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania

Background Results Results ® The ePlex Blood Culture Identification Panel Gram Positive (BCID-GP) is a Eighteen (17.6%) of the cultures contained more than one organism as identified by recently FDA-cleared assay that can identify 20 Gram positive organisms and 4 conventional culture and five of those (4.9%) contained three or more organisms. There ResultsPositive Agreement Negative Agreement resistance determinants along with a Pan Gram-Negative and Pan Candida were 12 repeat sample runs, six for failed cartridges (5.8%) and six for discordant N Culture+ and BCID+ BCID - and Culture - target from a positive blood culture bottle in 90 minutes. results. Staphylococcus 23 100% (23/23) 100% (79/79) 13 100% (13/13) 100% (89/89) Gram-Positive Organisms Positive Agreement Negative Agreement Staphylococcus epidermidis 5 100% (5/5) 100% (97/97) cereus group Micrococcus BCID+ BCID- Staphylococcus lugdunensis 2 100% (2/2) 100% (100/100) Bacillus subtilis group Staphylococcus Resistance Mechanisms N Resistant by AST Susceptible by AST Other Staphylococcus spp. 4 100% (4/4) 100% (98/98) Corynebacterium Staphylococcus aureus Staphylococcus spp. (mecA) 29 100% (5/5) 100% (8/8) (S. capitis n=1, S. cohnii n=1, S. hominis n=2) Cutibacterium acnes (Propionibacterium acnes) Staphylococcus epidermidis spp. (vanA) 25 80% (6/8) 100% (17/17) Enterococcus Staphylococcus lugdunensis N Positive Agreement Negative Agreement Table 2. Positive and negative agreement of BCID with traditional AST for MRSA and 30 96.7% (29/30) 95.8% (69/72) Streptococcus VRE. The two discordant Enterococci were E. gallinarum which is expected to (GBS) Streptococcus agalactiae 3 66.7% (2/3) 98.9% (98/99) display resistance through vanC. 5 100% (5/5) 100% (97/97) Lactobacillus Streptococcus anginosus group Streptococcus anginosus 4 100% (4/4) 97.9% (96/98) Discrepancy Resolution Streptococcus pneumoniae 3 100% (3/3) 98.9% (98/99) Streptococcus pyogenes (GAS) Culture BCID Repeat culture Repeat BCID Other Streptococcus Spp. 16 93.8% (15/16) 100% (86/86) Pan Targets Resistance Genes [S. constellatus n=1, S. dysgalactiae n=2, S. parasanguinis n=2, S. sanguinis n=1, S. Enterococcus hirae*; Pan Gram-Negative mecA gordonii n=1, S. salivarius n=2, S. mitis/oralis n=6, Strep species no further ID n=1 Pan Candida mecC /oralis; Streptococcus Streptococcus salivarius N Positive Agreement Negative Agreement vanA Enterococcus faecalis; Did not isolate Enterococcus 27 92.6% (25/27) 100 % (75/75) vanB Enterococcus faecalis; Enterococcus faecalis; Streptococcus; additional Enterococcus faecalis 12 100% (12/12) 100% (90/90) Table 1. BCID-GP Panel Targets Klebsiella pneumoniae Pan Gram-Negative Pan Gram-Negative Streptococcus spp. Enterococcus faecium 8 100% (8/8) 100% (94/102) Streptococcus agalactiae; Streptococcus agalactiae; Did not isolate Other Enterococcus spp. 7 71.4% (5/7) 100% (95/102) Methods Morganella morganii; Streptococcus anginosus; additional We performed a semi-prospective study comparing the performance of the Achoromobacter sp. Pan Gram-Negative Streptococcus spp. (E. raffinosus n=2, E. gallinarum n=2, E. casseliflavus n=1, E. hirae n=1, E. avium n=1) Enterococcus faecium; research use only (RUO) BCID-GP Panel to conventional culture followed by No additional species Enterococcus faecium Streptococcus agalactiae; Enterococcus faecium Gram positive rods N Positive Agreement Negative Agreement MALDI-TOF identification. Positive blood cultures with Gram positive or mixed isolated Lactobacillus group 2 50% (1/2) 100% (100/100) organisms on Gram stain were run on the RUO BCID-GP Panel within seven Bacillus subtilis group 2 50% (1/2) 100% (100/100) days of culture positivity. Streptococcus Streptococcus Streptococcus mitis/oralis** pneumoniae pneumoniae Corynebacterium 4 100% (4/4) 100% (98/98) A total of 102 distinct cultures were run, including 95 positive blood cultures, Streptococcus. Streptococcus Cutibacterium acnes (P. acnes) 2 100% (2/2) 100% (100/100) 2 spiked blood cultures and 5 negative blood cultures (after 5-day incubation). Streptococcus anginosus; mitis/oralis, anginosus; Lactobacillus 2 100% (2/2) 99% (99/100) Streptococcus mitis/oralis Blood cultures with a discrepancy between the BCID panel and initial culture Staphylococcus epidermidis Staphylococcus Staphylococcus Listeria monocytogenes 1 100% (1/1) 100% (101/101) results were reviewed. Resolution was attempted by reviewing the patients other epidermidis epidermidis Others 6 0% (0/6) 100% (96/96 recent cultures, re-culturing the original blood culture vial and/or repeating the (Bifidobacterium spp. n=1, ramosum n=2, Actinomyces spp. N=2, Anaerobic Staphylococcus aureus; Staphylococcus aureus; GPR no further ID n=1) BCID at the discretion of the clinical microbiologist. Streptococcus agalactiae Streptococcus Streptococcus; Enterococcus avium, Streptococcus, Table 3. Positive and negative agreement of BCID compared to conventional Enterococcus avium Pan Gram-Negative Hafnia alvei Pan Gram-Negative culture followed by MALDI-TOF identification. Analysis was performed after Enterococcus discrepancy resolution. faecalis, Enterococcus gallinarum Enterococcus faecalis Enterococcus faecalis Enterococcus Conclusions gallinarium Bacteroides fragilis, Overall, the ePlex RUO BCID-GP Panel displayed excellent concordance regarding Enterococcus Enterococcus; Enterococcus Staphylococcus spp., Enterococcus spp. and Gram-positive rods. casseliflavus Pan Gram-Negative casseliflavus - In three cases, new microorganisms were identified on BCID and confirmed with Separate bottle w/ re-culture. Streptococcus anginosus; Enterococcus faecalis Streptococcus - The identification of spurious Streptococcal targets, found in three separate Enterococcus faecalis anginosus cases and not confirmed on culture should be monitored as the panel is brought into clinical testing. Table 2. Discrepancies and attempted resolutions: Green- discrepant results able to - At lease one rare enterococcal species (E. hirae) was not identified by BCID. resolve via additional culture data. Red- unable to resolve with culture data Figures 1a and 1b. Distribution of tested cultures (before discrepancy resolution) *Enterococcus hirae ID'd by 16S sequencing The authors would like to thank GenMark Diagnostics for providing equipment and reagents for and percent of the relevant species tested on the BCID Panel. **Bile solubility test on culture confirmed S. mitis/oralis. this study. GenMark had no role in the design, execution, or interpretation of the study.