Advancing antimicrobial therapy: evaluating the ASTar (Q-linea) System for rapid AST in Gram-negative bloodstream...

Bloodstream infections (BSIs) caused by Gram-negative bacteria are a leading cause of sepsis and mortality, underscoring the need for rapid, reliable antimicrobial susceptibility testing (AST) to guide targeted therapy. We evaluated the analytical performance, turnaround time, and potential clinical impact of the ASTar System (Q-linea), an automated rapid phenotypic AST platform that reports minimum inhibitory concentration-based results directly from positive blood cultures. A total of 76 prospective clinical and 32 antibiotic-resistant specimens from the CDC & FDA AR Isolate Bank selected to represent diverse and well-characterized resistance profiles were tested and compared with the Standard-of-Care (SoC) MicroScan-WalkAway method using 2021 FDA STIC breakpoints. ASTar demonstrated essential and categorical agreement of 98.4% and 99.3% with SoC for clinical isolates, and 95.4% and 97.0% for CDC & FDA AR Isolate Bank specimens, respectively. The median turnaround time for ASTar results was 13.1 h compared with 51.2 h for SoC (P < 0.0001). Clinician-led retrospective chart review indicated earlier ASTar results could have influenced antimicrobial therapy in 83% of cases, enabling de-escalation in 66.2%, escalation in 13.8%, adjustment of route of administration in 15.4%, potential dose adjustment in 1.5%, and confirmation of the ongoing empiric therapy in 16.9%, with anticipated benefits, such as reduced antibiotic-related side effects in 47.7%, decreased antibiotic exposure in 46.2%, earlier discharge on oral therapy in 32.3%, correction of ineffective empiric therapy, and reduced length of stay, were each anticipated in 21.5% and 15.4% of cases, respectively. These findings support the use of ASTar to improve the management of Gram-negative BSIs through faster, targeted antimicrobial therapy.

Delays in antimicrobial susceptibility testing for Gram-negative bloodstream infections prolong empiric broad-spectrum therapy and can worsen clinical outcomes. This study presents data on the analytical performance, turnaround time, and potential clinical impact of the ASTar System for rapid antimicrobial susceptibility testing of Gram-negative bloodstream infections. The comparison of ASTar results with a Standard-of-Care method offers data to support clinical laboratories in assessing rapid phenotypic AST platforms, such as ASTar, their role in antimicrobial stewardship, and possible workflow adjustments for faster, targeted therapy in the management of Gram-negative bloodstream infections.