Assays that expedite the reporting of organism identification and antibiotic susceptibility status in positive blood cultures can fast track interventions that improve clinical outcomes. We evaluated the Verigene Gram-positive blood culture nucleic acid test (BC-GP) in two pediatric hospitals. Positive BacT/Alert Pediatric FAN blood cultures with Gram-positive organisms were tested using the BC-GP in tandem with routine laboratory procedures. To test organisms underrepresented in the clinical blood culture evaluation, blood culture bottles were spiked with diluted organism suspensions at concentrations of 10 to 100 CFU per milliliter. A total of 249 Gram-positive bacterial isolates were recovered from 242 blood cultures. The BC-GP detected Staphylococcus aureus, methicillin-susceptible S. aureus, and methicillin-resistant S. aureus with sensitivities of 100%, 99%, and 100% and specificities of 100%, 100%, and 99.5%, respectively. The BC-GP detected Staphylococcus epidermidis, methicillin-susceptible S. epidermidis, and methicillin-resistant S. epidermidis with sensitivities of 95%, 80%, and 96%, respectively, and 100% specificity. The BC-GP correctly identified 14/15 cases of Enterococcus faecalis and Enterococcus faecium bacteremia and 9 cases of Streptococcus pneumoniae. It misidentified 5/15 clinical blood cultures with Streptococcus mitis/Streptococcus oralis and 1/3 blood cultures spiked with Streptococcus anginosus group as S. pneumoniae. The BC-GP detected a case of Streptococcus pyogenes bacteremia but failed to detect 2/3 clinical blood cultures with Streptococcus agalactiae. BC-GP's rapid accurate detection of Staphylococcus spp., E. faecium, and E. faecalis and its ability to ascertain mecA, vanA, and vanB status may expedite clinical decisions pertaining to optimal antibiotic use. False-positive S. pneumoniae results may warrant reporting of only "Streptococcus spp." when this organism is reported by the BC-GP.

Context.-Timely initiation of directed antimicrobial therapy for Staphylococcus aureus bacteremia is dependent on rapid identification of S aureus to ascertain methicillin-susceptibility status.Objective.-To investigate the performance of the rapid KeyPath (MicroPhage, Inc, Longmont, Colorado) methicillin-resistant S aureus (MRSA) and methicillin-susceptible S aureus (MSSA) blood culture test (MMBT).Design.-Positive BacT/ALERT Pediatric FAN (fastidious antibiotic neutralization) blood culture bottles (bioMérieux, Inc, Durham, North Carolina) were tested prospectively using MMBT and routine bacterial identification and antibiotic susceptibility testing procedures as the gold standard. The MMBT uses an S aureus-specific bacteriophage cocktail that infects bacterial cells and replicates them, resulting in cellular lysis. Bacteriophagespecific antibodies detect the increase in bacteriophage concentration in an immunoassay device. Phage amplification, in both the presence and absence of cefoxitin, indicates the presence of MRSA. The sensitivity, specificity, positive predictive value, and negative predictive value of MMBT in detecting S aureus, MSSA, and MRSA were calculated.Results.-Of 188 positive blood cultures tested, 199 (63%) had Gram-positive cocci in clusters, 46 (24%) grew S aureus (26 MSSA [57%], 20 MRSA [43%]) with the MMBT detecting 40 of 46 (87%). The sensitivity, specificity, positive predictive value, and negative predictive value among blood cultures with Gram-positive cocci in clusters were 87%, 100%, 100%, and 92% for S aureus; 81%, 100%, 100%, and 95% for MSSA; and 95%, 100%, 100%, and 99% for MRSA. All blood cultures without growth of S aureus tested negative by MMBT.Conclusions.-The MMBT detected MSSA and MRSA directly from positive BacT/ALERT PF bottles with positive predictive values of 100%, suggesting that positive results could be reported immediately, but the sensitivity of this assay limited immediate reporting of negative results.

c Here, we compare the sensitivities and times to detection (TTD) of BacT/Alert Pediatric FAN (PF) and Bactec Peds Plus blood culture bottles. Test bottles were inoculated with 2 ml of banked whole blood, 1-ml aliquots of antibiotic suspension, and organisms diluted to simulate a bacteremia level of 10 to 100 CFU/ml. The control bottles were inoculated with 3 ml of banked blood and organism suspensions only. The organism-drug combinations were Staphylococcus epidermidis and vancomycin, methicillin-resistant Staphylococcus aureus and vancomycin, Streptococcus pneumoniae, vancomycin, and ceftriaxone, Streptococcus agalactiae, ampicillin, and cefotaxime, Escherichia coli, cefotaxime, and cefepime, Pseudomonas aeruginosa, piperacillin-tazobactam, cefepime, and gentamicin, Neisseria meningitidis and ceftriaxone, and Haemophilus influenzae and ceftriaxone. The control and test bottle combinations were tested in duplicate. The bottles were incubated for 5 days; 32 control and 104 test bottles were incubated. Overall, the bacterial recovery rates for the PF and Peds Plus bottles were 37% and 62%, 94% and 100% in the controls, 19% and 50% in the test bottles, and 33% and 92% in the bottles with vancomycin, respectively. No bacteria were recovered from the bottles with S. pneumoniae, S. agalactiae, E. coli, N. meningitidis, or H. influenzae in combination with cefotaxime or ceftriaxone. The Peds Plus system detected P. aeruginosa in bottles with cefepime and piperacillin-tazobactam, but the PF system recovered bacteria only in bottles with trough levels of piperacillin-tazobactam. The mean TTD were shorter in the Peds Plus system controls (14.2 versus 18.0 h; P ‫؍‬ 0.001) and the test bottles (14.3 versus 17.8 h; P ‫؍‬ 0.008) than in the PF bottles. Overall, we demonstrated superior sensitivity, TTD, and antibiotic neutralization in the Bactec Peds Plus system compared to those in the Pediatric FAN system.