Comparison of Growth Performance of the BacT/ALERT VIRTUO and BACTEC FX Blood Culture Systems Under Simulated Bloodstream Infection Conditions.

BACKGROUND

We evaluated growth performance of the BacT/ALERT VIRTUO and the BACTEC FX blood culture (BC) systems based on recovery rate and time to detect microorganisms under simulated bloodstream infection conditions.

METHODS

Three expected concentrations of 125, 30, and 5 CFU/mL of eighteen reference microorganisms were diluted with 5 mL blood for adult aerobic/anaerobic culture and with 3 mL for pediatric aerobic culture and inoculated, and each of three BC bottles were loaded into the two BC systems.

RESULTS

A total of 405 comparative bottles were analyzed in this study. The percent agreement between the BacT/ ALERT VIRTUO and BACTEC FX systems after comparing the positive results was 96.8% (392/405). The BacT/ ALERT VIRTUO and BACTEC FX systems yielded 100% positive signals at 125 and 30 CFU/mL, whereas there were 5.2% (7/135) and 8.1% (11/135) false-negative results at 5 CFU/mL, respectively. No statistical difference in recovery rate based on the overall concentration of microorganisms was observed between the two BC systems (p = 0.329). No statistical difference in time to detection (TTD) was observed between the two BC systems based on the overall concentration of microorganisms (p = 0.067). Inter-instrument comparisons of TTD resulted in a good correlation (r = 0.947) for all inoculated bottles.

CONCLUSIONS

The BacT/ALERT VIRTUO showed similar recovery rate and TTD of microorganisms, compared to BACTEC FX BC system. Due to its versatility to accommodate a higher workload through automated loading and unloading of BC bottles with faster detection of pathogens from bloodstream, the BacT/ALERT VIRTUO system may establish itself as a useful alternative.