Performance of pathogen identification and resistance gene expression tests using ASTar® remnant bacterial suspension in Gram-negative contrived positive blood cultures
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Introduction
Rapid pathogen identification, resistance detection, and susceptibility profiling improve antimicrobial prescribing and associated outcomes, but fragmented workflows lead to inefficiencies and are costly. We evaluated a research-use-only (RUO) approach using ASTar® remnant bacterial suspension from routine AST for MALDI-TOF MS pathogen identification and Lateral Flow Assay (LFA)-based detection of targeted resistance mechanisms.
Methods
Gram-negative (GN) bacterial strains from reference and curated resistance collections (CDC1, ARLG2, ATCC3) [n=119] were contrived into blood culture bottles and processed in the ASTar System using the ASTar BC G-Kit (Q-linea AB, Sweden). Under RUO conditions, remnant bacterial suspensions were collected ~1-2 h after ASTar run initiation and analyzed using NG Test CTX-M Multi, NG Test CARBA-5, NG Test Acineto-5 RUO, and MALDI-TOF MS.
Results
Mean (± SD) remnant suspension volume was 2722 μL (± 300 μL). All samples yielded high-confidence MALDI-TOF MS scores (>2.0), with five initially scoring <2.0 and resolving on repeat testing. LFA results showed full agreement with reference isolates for blaCTX-M positive/negative (30/30) and with 60 or 61 target carbapenemase-positive/negative isolates. Testing of a subset of samples to mimic reflex workflows with ASTar phenotypic results did not affect LFA performance (n=26; 23 Enterobacterales, 3 P. aeruginosa and 9 A. baumannii) . Cost savings can be realised versus commercial multiplex PCR.
Conclusion
This integrated approach of ~6 h rapid phenotypic AST with same-run identification and resistance detection (1-2 h from instrument start) or reflex testing upon availability of ASTar results may support earlier susceptibility results and offer cost savings to current workflows.
