Evaluation of BACTEC™ FX and BacT/Alert™ Automated Blood Culture Systems for Detection of Clinically Relevant Bacterial and Yeast Species

Background: Bloodstream infections (BSI) are a significant health concern, necessitating effective diagnostic tools. This study evaluates the performance of the BD Bactec FX system in comparison to the established BacT/Alert system, examining mean time till detection (TTD) across various blood culture bottles. Methods: The study involves 148 blood culture bottles, inoculated with representative bacterial ATCC strains (n= 15) and 04 yeast isolates. Parallel testing is conducted by seeding 10-30 colony-forming units (CFU) in duplicate in both BD Bactec FX and BacT/Alert systems. TTD is assessed across aerobic, anaerobic, and pediatric bottles for diverse microbial species. Results: All 148 bottles tested in parallel show positive signals in both systems. BD Bactec FX demonstrates significantly shorter TTD for adult-seeded cultures in aerobic and anaerobic bottles compared to BacT/Alert Similarly, pediatric bottles with BD Bactec FX exhibit a shorter TTD compared to BacT/Alert. The statistical significance of TTD, 95% confidence intervals (CI), and p-values is evident for Bactec FX aerobic, anaerobic, and pediatric bottles across tested organisms. Notable examples of faster TTD include; Bacteroides ovatus (16.6h by Bactec FX vs. 70.5h by Bact/Alert 3D), Stenotrophomonas maltophilia (33.7h vs. 72.5h), and Streptococcus pyogenes (8.1h vs. 11.9h). Conclusions: In conclusion, the study's findings demonstrate that BD Bactec FX surpasses BacT/Alert in prompt microbial detection, showcasing potential for early identification of bacteremia and fungemia. Faster TTD implies the potential to initiate timely antimicrobial treatment, thereby reducing patient morbidity and mortality. However, exceptions in certain microbial species highlight the need for comprehensive clinical validation to establish the broad applicability of these findings.