Diversity and geographic distribution of antibiotic resistance in food waste anaerobic digestion systems

Antibiotic resistance genes (ARGs) present in food waste pose a significant environmental and public health challenge, with anaerobic digestion emerging as a promising technology to reduce ARG abundance during waste treatment. In this study, we analyzed the resistomes in 64 anaerobic digestion sludge samples from seven full-scale food waste treatment facilities representing seven Chinese provinces. Across all facilities, a small core set of glycopeptide (van clusters), β-lactamase, aminoglycoside, and macrolide-lincosamide-streptogramin genes accounted for most ARG abundance (70.3%), marking them as critical targets for monitoring and post-treatment at high-risk sites such as Wenzhou. Resistome composition differed significantly among facilities and exhibited moderate correlation with bacterial taxonomic composition, with Firmicutes (Bacillota), Chloroflexota, and Proteobacteria as the major carriers associated with multiple resistance classes. ARG abundance was positively correlated with mobile genetic elements (r = 0.54, p < 0.0001), driven by integrases, transposases, and Tn916. Horizontal gene transfer was largely constrained within phylogenetic boundaries, particularly within Firmicutes (66.67%), limiting cross-phyla ARG dissemination. Resistome variation was driven predominantly by deterministic processes.; these deterministic filters together with regional differences in food-waste composition and MGEs, collectively select for a glycopeptide-dominated, Firmicutes-anchored resistome that is distinct from those in activated sludge and manure digesters.