Multi-center evaluation of the Selux next-generation phenotyping system for gram-negative direct-from-positive blood culture antimicrobial susceptibility testing

Accurate and rapid antimicrobial susceptibility test (AST) results from positive blood cultures are crucial for patient care and combatting antimicrobial resistance. Although recent advancements in rapid direct-from-positive blood culture (PBC) identification platforms have enabled the provision of species-level identification and some resistance marker information within hours after blood culture positivity, AST results required for clinical decision-making often require 48 h after blood culture positivity. This study evaluated the Selux next-generation phenotyping system, including an automated PBC Separator and the Selux AST system in a multicenter clinical trial for their ability to perform AST directly from PBCs for gram-negative bacilli. The PBC separator produces McFarland equivalent inocula from positive blood cultures within 1 h, facilitating direct processing on the Selux AST system. The study evaluated 162 fresh clinical PBC samples, 307 seeded clinical samples, and 87 seeded challenge samples across 4 sites for each of the 17 antimicrobials included in the panel. The results demonstrate that the Selux system's clinical performance, reproducibility, and analytical performances are consistent when using positive blood cultures held for up to 16 h after positivity on the BACTEC and BacT/ALERT 3D and BacT/ALERT VIRTUO blood culture systems, including all major BACTEC and BacT/ALERT blood culture bottle types. These findings suggest that the PBC Separator with the Selux AST system is a valuable addition to the arsenal of tools available for rapid sepsis diagnosis and management.