Rapid AST not superior to standard testing based on DOOR in Gram-Negative Bloodstream infections: JAMA

A new study published in the Journal of the American Medical Association revealed that rapid blood culture antimicrobial susceptibility testing (AST) did not show superiority over standard testing based on DOOR outcomes in patients with gram-negative bacilli bloodstream infections (BSIs). These results may still help guide clinical use along with other efficacy and safety considerations. 

The study focused on BSIs caused by gram-negative bacilli which are often linked to serious illness and rising antimicrobial resistance. This research evaluated whether a newer rapid AST method which helps to quickly identify the antibiotics will work, could outperform standard testing methods in real-world hospital settings.

7 medical centers across Greece, India, Israel, and Spain, enrolled 899 hospitalized patients in this randomized clinical trial between December 2023 and May 2025. Of these, 850 individuals (both adults and children) diagnosed with BSIs due to gram-negative bacteria were included in the final analysis.

The patients were divided into two groups, where one received rapid phenotypic AST directly from positive blood cultures along with standard testing, while the other group received only standard susceptibility testing. Antimicrobial stewardship teams at each hospital reviewed cases and guided treatment decisions.

The primary measure of success was based on a desirability of outcome ranking (DOOR) at 30 days, which categorized patients as alive without complications, alive with complications, or deceased. These results showed that the probability of better outcomes in the rapid-testing group was 48.8%, which fell short of the threshold required to demonstrate superiority over the standard methods.

The clinicians were able to adjust antibiotic treatments (escalating or deescalating therapy) approximately 14 hours sooner than with standard testing. However, this time advantage did not translate into measurable improvements in key clinical outcomes like the mortality, length of hospital stay, or rates of intensive care unit admission. Among patients with carbapenem-resistant infections, rapid testing reduced the median time to effective therapy from 28 hours to 9.5 hours.

The results highlight the complexity of treating severe infections in an era of growing antimicrobial resistance. Overall, the research indicates that rapid AST can enhance workflow efficiency and support quicker therapeutic adjustments, but its broader clinical impact remains limited. 

Source:

Banerjee, R., Komarow, L., Li, Y., Mau, D., Dodd, A., Geres, H., Greenwood-Quaintance, K., Adler, A., Baliga, S., Chowers, M., Chrysos, G., Zarkotou, O., Paul, M., Pournaras, S., Regueiro, D. S., Evans, S., Chambers, H., Fowler, V. G., Jr, Patel, R., & Antibacterial Resistance Leadership Group. (2026). Fast antimicrobial susceptibility testing for gram-negative bacteremia: The FAST randomized clinical trial: The FAST randomized clinical trial. The Journal of the American Medical Association. https://doi.org/10.1001/jama.2026.5487