Ring, E. | bioRxiv Science

bioRxiv2026

Performance of pathogen identification and resistance gene expression tests using ASTar(R) remnant bacterial suspension in Gram-negative contrived positive blood cultures

IntroductionRapid 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(R) remnant bacterial suspension from routine AST for MALDI-TOF MS pathogen identification and Lateral Flow Assay (LFA)-based detection of targeted resistance mechanisms. MethodsGram-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. ResultsMean ({+/-} SD) remnant suspension volume was 2722 L ({+/-} 300 L). 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. ConclusionThis 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.

microbiology↗

bioRxiv2026

Microplastics drive both linear and threshold-type shifts in soil multifunctionality along concentration gradients

Microplastics are increasingly recognized as emerging contaminants in terrestrial ecosystems, yet their mechanistic impacts on soil multifunctionality remain poorly understood. Here, we evaluated the influence of two microplastic polymers, polyethylene terephthalate and polypropylene, on soil functioning by subjecting soils to a gradient of concentrations of these microplastics, and measuring six variables representing soil physical, chemical, and biological functions. A statistical framework combining multi-model inference with threshold detection and machine learning was implemented in this study to identify the main pathways of soil multifunctional change. Most significant responses followed nonlinear trends and threshold shifts, primarily in physical properties, indicating that microplastic stress first impacts soil structure before cascading to chemical and biological processes. We identified two system-level thresholds at 0.3% PP and 0.55% PET w/w; while random forest highlighted water-stable aggregates as the dominant predictor of overall soil multifunctionality. Our findings provide new quantitative evidence of complex soil multifunctionality responses to microplastic pollution. Most importantly, physical deterioration emerged as an early-warning signal of microplastic disturbance, thereby advancing our understanding of microplastic pollution on soil systems.

ecology↗