Objective:

To evaluate the effectiveness of rapid antimicrobial susceptibility testing compared to standard testing specifically in patients with gram-negative bloodstream infections.

Key Findings:

• Rapid testing did not show superiority over standard testing for 30-day clinical outcomes (48.8% probability of favorable outcomes), indicating no significant benefit.
• 30-day mortality rates were similar: 24% in rapid testing group vs 23% in standard group, highlighting the lack of impact on mortality.
• Median time to antibiotic modification was faster with rapid testing (22 hours vs 36 hours), demonstrating improved treatment speed.
• 84% of patients in the rapid group received effective therapy within 24 hours compared to 75% in the standard group, emphasizing the advantage of rapid testing.
• Among carbapenem-resistant infections, 72% in the rapid group received effective therapy within 24 hours vs 47% in the standard group, indicating a significant benefit in this subgroup.

Interpretation:

Rapid testing improved the speed of treatment optimization but did not significantly impact overall clinical outcomes, likely due to the patient population and the presence of existing effective therapies at enrollment, which may have masked potential benefits.

Limitations:

• The open-label design and combined intervention with antimicrobial stewardship review limited the ability to isolate the effects of rapid testing.
• Variability in resistance prevalence, testing workflows, and antibiotic availability across sites may have influenced results.
• Nearly 20% of patients had organisms not included in the rapid testing panel, potentially limiting the intervention's effectiveness.

Conclusion:

While rapid antimicrobial susceptibility testing enhances treatment speed, it does not significantly improve clinical outcomes; however, it may be beneficial in managing resistant infections, particularly through faster deescalation of broad-spectrum antibiotics.