Bloodstream infections are associated with high rates of morbidity and mortality. Blood culture remains the gold standard for the diagnosis of BSIs.

Background Bloodstream infections are associated with high rates of morbidity and mortality, therefore prompt identification and antimicrobial susceptibility testing of the causative organism(s) are critical. We compared the microbiological/clinical performance of BacT/ALERT®-VIRTUO™-(BioMerieux) to that of the BACTEC™FX-(BD) instrument, with time-to-detection (TTD, from loading into system until positivity) as the primary outcome. Secondary microbiological outcomes were positivity and contamination rates, hands-on-time, turn-around-time (TAT) and time-to-identification. Methods We performed a prospective cross-over study using blood cultures from patients (>18 years) suspected of bacteremia/fungemia, localized in different wards into two strata (Stratum-1: Emergency Department-ED-; Stratum-2: in-hospital patients). Testing was performed in BACTEC™-PlusAerobic/F and BACTEC-Lytic/10-Anaerobic/F bottles and incubated in BACTEC™FX, or BacT/ALERT®FA-Plus and FN-Plus bottles and incubated in VIRTUO™. Initially, each strata was randomly assigned to one of the incubators and then alternated every 2-weeks for 6 months (October-16th-2018 to April-16th-2019). All samples were processed in parallel with the same work-flow from the moment they were flagged positive. Maximum incubation time was 5 days. Results We included a total of 4782 extractions (9510 bottles) in VIRTUO and 5139 (10193 bottles) in BACTEC. The median age was 67 years for both groups and the samples were equally distributed for each ward (ED: VIRTUO 80.9%, BD 76.4%). The number of blood cultures with at least one positive extraction was 873(18.3%) for VIRTUO and 802(15.6%) for BACTEC (p=0.0003). TTD and proportion of aerobic/anaerobic bottles is shown in Table. Hands-on-time was reduced by 15 minutes/day when using VIRTUO. Table Conclusion We have compared on a large scale and in a “real world” setting the performance of two automatic blood culture incubators. TTD was significantly lower for the VIRTUO incubated samples, with differences in both systems depending on the type of bottle (aerobic vs. anaerobic). The number of positive results was significantly higher for the VIRTUO incubated samples, which might impact antimicrobial prescription and clinical outcomes. Disclosures Ana V. Halperin, MD, Biomérieux (Grant/Research Support) José Luis Cortés Cuevas, MD, biomerieux (Research Grant or Support)biomerieux (Research Grant or Support) Juan Antonio Del Castillo Polo, MD, Biomérieux (Research Grant or Support) Sergio Talens, n/a, Biomerieux (Research Grant or Support) Robert Birch, n/a, bioMerieux Inc. (Employee) Rafael Cantón, PharmD PhD, Biomérieux (Grant/Research Support)