Unraveling antibiotic resistance gene hotspots in mass-reared insects’ manure compost: A comparative study of traditional and industrialized sericulture

Industrial insect farming generates large quantities of manure, yet the fate and transmission risk of antibiotic resistance genes (ARGs) during insect-manure composting are largely unknown. Here, we compared ARG risks during the composting of silkworm excrement from traditional (TSE) and industrialized (ISE) sericulture. Specifically, in TSE, enriched ARGs were closely linked to pathogens, whereas in ISE, antibiotic-use practices drove ARG enrichment. Through metagenomic binning analysis, we identified 119 ARG-hosting taxa (TSE: 71, ISE: 48). In the TSE group, Pseudomonadota was the primary high-risk MAG, carrying an average of 20 ARGs per genome, while Bacillota dominated in the ISE group, with only five ARGs per genome. Furthermore, 52.1% of high-risk MAGs in the TSE group were considered potential pathogens, whereas the proportion was 33.3% in the ISE group. We then quantified ARG transmission risk using the ARGs-Mobile Genetic Elements (MGEs) distance index and further validated it through a compost-soil microcosm experiment, which indicated a higher risk of ARG transmission in the TSE group. Furthermore, the ARG transmission risk increased in the TSE group but decreased in the ISE group during composting. Notably, over 50% of ARGs formed stable combinations with specific MGEs, highlighting potential targets for reduction strategies. Finally, structural equation modeling revealed that biotic factors (MGEs and bacterial composition) had direct effects on ARGs, while abiotic factors (temperature and compost properties) influenced them indirectly. Overall, this study provides the first ecotechnological insights into ARG risks in insect manure compost, paving the way for sustainable insect bioresource production.