Evaluation of the Nanosphere Verigene Gram-Positive Blood Culture Assay with the VersaTREK Blood Culture System and Assessment of Possible Impact on Selected Patients

The Verigene Gram-positive blood culture (BC-GP) assay (Nanosphere, Northbrook, IL) is a molecular method for the rapid identification of Gram-positive organisms and resistance markers directly from blood culture bottles. A total of 148 VersaTREK REDOX 1 40-ml aerobic bottles demonstrating Gram-positive bacteria were tested. Results were compared with those from conventional biochemical and matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) identifications. We obtained isolates of methicillin-resistantStaphylococcus aureus (MRSA) (24), methicillin-susceptibleStaphylococcus aureus (MSSA) (14), methicillin-resistantStaphylococcus epidermidis (MRSE) (17), methicillin-susceptibleStaphylococcus epidermidis (MSSE) (9), other coagulase-negative staphylococci (19),Streptococcus salivarius (5),Streptococcus parasanguinis (2),Streptococcus sanguinis (1),Streptococcus cristatus (1), theStreptococcus bovis group (5),Streptococcus agalactiae (9), theStreptococcus anginosus group (1),Streptococcus pneumoniae (6), vancomycin-resistantEnterococcus faecium (VRE FCM) (16), vancomycin-susceptibleEnterococcus faecalis (3),Aerococcus viridans (2),Bacillus (6),Corynebacterium (8),Lactobacillus (2),Micrococcus (2),Neisseria mucosa (1),Escherichia coli (3),Candida tropicalis (1),Propionibacterium (1), andRothia (1). Overall agreement with the culture results was 95%. A total of 137 of 138 (99%) monomicrobial cultures were concordant. We tested 9 polymicrobial samples and found 33% agreement. A chart review of 31 patients with MRSA, MSSA, or VRE demonstrated that the Nanosphere BC-GP assay might have led to more appropriate antibiotic selection for these patients an average of 42 h earlier. Additionally, contact isolation could have been initiated an average of 37 h earlier for patients with MRSA or VRE. The BC-GP assay may have a positive impact on patient care, health care costs, and antibiotic stewardship.