Evaluation of Performance and Possible Clinical Impact of Rapid QMAC-dRAST Antimicrobial Susceptibility Testing From Positive Blood Cultures in a Tertiary Hospital and Low Antimicrobial Resistance Setting

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• Picked for Microbiology (medical) (top studies of the week, 8 November 2026): Evaluates rapid blood-culture AST accuracy and resistance detection

Abstract

This study evaluated QMAC-dRAST for rapid antimicrobial susceptibility testing from positive blood cultures in a low-resistance setting by assessing analytical accuracy, detection of key resistance mechanisms and potential to shorten time to effective therapy. We tested 181 isolates and compared QMAC-dRAST results with disc diffusion, resolving discrepancies by broth microdilution and calculating categorical agreement (CA) and error rates according to ISO 20776-1:2019. We analyzed potential clinical impact among 128 patients with bacteremia. Categorical agreement was 92% for Gram-negative and 91% for Gram-positive bacteria, with very major errors in 7% and 28% of resistant isolates, respectively. Performance was limited for several key antibiotics: cefotaxime showed high very major error rates, piperacillin-tazobactam resistance was overestimated and meropenem resistance was underestimated. QMAC-dRAST system correctly detected most critical resistance mechanisms, including all MRSA and VRE isolates and, after user interpretation, 90% of carbapenemase-producing Enterobacterales. QMAC-dRAST could have markedly shortened time to effective therapy in 8% of patients, but one false MRSA result risked inappropriate escalation of therapy. In this low-resistance setting, QMAC-dRAST offered modest benefit over rapid species identification, while suboptimal performance for key antibiotics, the absence of cefuroxime from the panel, and workflow challenges limited its utility without further optimization.

Abstract as published, via PubMed.