Meta-analysis and interpretable machine learning characterize ARG and MGE co-enrichment under microplastic exposure...

Waste activated sludge is an important sink for microplastics (MPs), and anaerobic digestion (AD), the mainstream process for sludge treatment, may provide conditions that facilitate MP-associated enrichment and dissemination of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), posing potential resistance-related risks. However, how MP physical attributes and AD operating conditions are jointly associated with ARG and MGE dynamics remains unclear. Here, we integrated evidence using dependency-aware three-level random-effects meta-analysis and XGBoost-SHAP association analysis, with reactor mode tested as a moderator and generalizability assessed by study-grouped and leave-one-study-out validation. MP exposure was associated with 57.5% and 35.0% increases in ARGs and MGEs, respectively, while responses were broadly consistent across batch and semi-continuous reactors. Tetracycline, β-lactam, and sulfonamide ARGs showed enrichment, whereas MGE responses were concentrated in integron-related elements, particularly intI1. SHAP analysis associated MP shape and aging status more strongly with ARG enrichment and particle size more closely with MGE responses, while incubation duration acted as a shared factor. Joint interaction analysis identified shape- and aging-centred combinations as predominantly ARG-associated, duration-temperature interactions as predominantly MGE-associated, and particle size and duration as links between the two response structures. The design separates pooled-effect estimation and reactor-related moderation from nonlinear association mapping while accounting for dependent observations across studies. Together, the findings support a staged associative framework linking plastisphere establishment, ARG host enrichment, and MGE-associated mobilization, providing a basis for coordinated monitoring and management of MP-related resistance risks in AD systems.