The FilmArray platform (FA; BioFire, Salt Lake City, UT) is a closed diagnostic system allowing high-order multiplex PCR analysis with automated readout of results directly from positive blood cultures in 1 h. In the present study, we evaluated the clinical performance of the FilmArray blood culture identification (BCID) panel, which includes 19 bacteria, five yeasts, and three antibiotic resistance genes. In total, 206 blood culture bottles were included in the study. The FilmArray could identify microorganisms in 153/167 (91.6%) samples with monomicrobial growth. Thirteen of the 167 (7.8%) microorganisms were not covered by the FilmArray BCID panel. In 6/167 (3.6%) samples, the FilmArray detected an additional microorganism compared to blood culture. When polymicrobial growth was analyzed, the FilmArray could detect all target microorganisms in 17/24 (71%) samples. Twelve blood culture bottles that yielded a positive signal but showed no growth were also negative by FilmArray. In 3/206 (1.5%) bottles, the FilmArray results were invalid. The results of the FilmArray were reproducible, as demonstrated by the testing and retesting of five bottles in the same day and a longitudinal follow-up of five other blood cultures up to 4 weeks. The present study shows that the FilmArray is a rapid identification method with high performance in direct identification of bacteria and yeasts from positive blood culture bottles.

Rapid identification of bacteria from blood cultures enables early initiation of appropriate antibiotic treatment in patients with bloodstream infections (BSI). The objective of the present study was to evaluate the use of matrix-associated laser desorption ionization-time of flight (MALDI-TOF) MS after a short incubation on solid media for rapid identification of bacteria from positive blood culture bottles. MALDI-TOF MS was performed after 2.5 and 5.5 h plate incubation of samples from positive blood cultures. Identification scores with values ≥ 1.7 were accepted as successful identification if the results were confirmed by conventional methods. Conventional methods included MALDI-TOF MS, Vitek 2, and diverse biochemical and agglutination tests after overnight culture. In total, 515 positive blood cultures with monomicrobial bacterial growth representing one blood culture per patient were included in the study. There were 229/515 (44.5%) and 286/515 (55.5%) blood culture bottles with Gram-negative bacteria (GNB) and Gram-positive bacteria (GPB), respectively. MALDI-TOF MS following short-term culture could accurately identify 300/515 (58.3%) isolates at 2.5 h, GNB being identified in greater proportion (180/229; 78.6%) than GPB (120/286; 42.0%). In an additional 124/515 bottles (24.1%), identification was successful at 5.5 h, leading to accurate identification of bacteria from 424/515 (82.3%) blood cultures after short-term culture. Interestingly, 11/24 of the isolated anaerobic bacteria could be identified after 5.5 h. The present study demonstrates, in a large number of clinical samples, that MALDI-TOF MS following short-term culture on solid medium is a reliable and rapid method for identification of bacteria from blood culture bottles with monomicrobial bacterial growth.

cWe compared the newly approved BacT/Alert Virtuo blood culture system to the BacT/Alert 3D system using 115 clinical bacterial and fungal isolates in 784 simulated blood culture bottles. The time to detection was reduced by roughly 20% in the Virtuo system (P < 0.0001) while the detection rate did not differ. Bloodstream infections remain a leading cause of death and are associated with high mortality and morbidity (1, 2). Early intervention and initiation of appropriate treatment have been shown to improve patient outcome (3-5). Rapid detection and identification of the causing pathogen are therefore essential in the diagnosis of these invasive diseases.Blood culture (BC) is the gold standard for detection of bacteria and fungi from blood or other normally sterile body fluids. It has previously been shown that the type of BC bottle used has a substantial impact on the microbiological diagnosis of bloodstream infections (6-10), as these media are complex formulations that provide nutrients and neutralizing antimicrobials in clinical blood samples (11). In addition, the BC system affects workflow and microbiological performance (11,12). To date, the most widely distributed BC systems are the BacT/Alert 3D (bioMérieux; referred to as 3D hereafter), BD Bactec (Becton Dickinson), and VersaTREK (Thermo Scientific). bioMérieux has recently introduced a new BC system with automatic loading and unloading of BC bottles, the BacT/ Alert Virtuo (Virtuo), for bacterial and fungal detection in BC. Enhanced colorimetric technology to detect microbial growth and improved temperature stability suggest improved culture conditions in the Virtuo compared to the 3D system. However, the microbiological performance of Virtuo has not been evaluated.In this study, the Virtuo system was tested in direct comparison with the 3D system by parallel incubation of a total of 115 clinical bacterial and fungal isolates (Table 1). All isolates were originally collected from clinical BC samples sent for microbiological diagnosis to Karolinska University Laboratory (Stockholm, Sweden) from three tertiary care hospitals in the greater Stockholm area. Isolates were recovered from frozen stocks and were cultured overnight on appropriate agar medium. Approximately 15 CFU in phosphate-buffered saline was inoculated into each BC bottle with 8 ml defibrinated horse blood, and all BC bottles were incubated until positivity was reached or for a maximum of 5 days. We and others have previously demonstrated that the use of horse blood does not significantly influence the performance of BC systems (13-17). Growth was assessed in aerobic (FA and FA Plus) and anaerobic (FN and FN Plus) BacT/Alert BC bottles, except for Acinetobacter spp. and Candida spp., which were cultured under aerobic conditions only. While the CE-approved version of the Virtuo system is intended to operate with resin-based BC bottles (FA Plus and FN Plus) only, charcoal-based BC bottles (FA and FN) were evaluated in the 3D system and in the investigational-use-only version of Virtuo emplo...