Comparison of microorganism detection and time-to-positivity in pediatric and standard media from three major commercial continuously monitored blood culture systems.

New blood culture instrumentation and media formulations have led to improved time-to-positivity (TTP) for positive blood cultures. Data regarding the necessity of pediatric blood culture bottles with contemporary blood culture systems are sparse. We compared performance of three commercial blood culture systems, evaluating impact of blood volumes in standard and pediatric blood culture media across systems. Simulated blood cultures with packed red blood cells and three Gram-positive, four Gram-negative, and one anaerobic organism (final concentrations ranging from 0.5-19 CFU/mL blood) on the VIRTUO, VersaTREK, and Bactec FX were evaluated with FAN Plus, REDOX, and BACTEC Plus media, respectively. For each media/instrument/organism combination 1, 3, 5, and 10 mL blood volumes were evaluated in triplicate. Detection rate was not affected by blood volume. Aerobic organisms that demonstrated variable detection were Kingella kingae, Haemophilus influenzae and Neisseria meningitidisBacteroides fragilis was detected in 83%, 100%, and 100% of VIRTUO, VersaTREK, and Bactec anaerobic bottles. Average TTP of standard media for aerobic organisms detected on VIRTUO was decreased compared to VersaTREK (-2.3 h) and Bactec (-4.9 h). Compared to standard media, detection rate and TTP was unchanged on VIRTUO, while TTP was reduced with pediatric media for 2/8 organisms tested on Bactec and 7/8 organisms on VersaTREK, illustrating the potential benefit of pediatric media on VersaTREK or BACTEC when low blood volumes (<5 mL) are collected. These results demonstrate that TTP is decreased on the VIRTUO compared to VersaTREK and Bactec for many microorganisms associated with BSI but may have species-specific limitations.