Enrichment risk and drivers of manure-derived antibiotic resistance genes in black soldier fly larval gut

Black soldier fly larvae (BSFL) are promising for converting animal manure into protein; however, the risk of antibiotic resistance gene (ARG) enrichment in the larval gut during this process remains unclear. Here, we employed metagenomic and metatranscriptomic analyses to investigate this risk during BSFL conversion of duck manure. Our results demonstrated that within the BSFL treatment system, ARG abundance and diversity in manure decreased significantly over time. Concurrently, total abundance and transcriptional activity of ARGs in the larval gut were significantly lower than those in manure. However, comparative sequence analysis suggested the potential for ARG exchange between bacterial communities in manure and larval gut. Klebsiella, Escherichia, Citrobacter, and Pseudomonas were identified as the primary hosts in the gut. The enrichment and dynamics of these manure-derived ARGs were jointly driven by shifts in physicochemical properties (notably organic matter and total nitrogen), mobile genetic elements, and the bacterial community. Validation experiments demonstrated that modulating these key physicochemical drivers can mitigate ARG abundance in the larval gut. Overall, this study highlights the potential enrichment risk of manure-derived ARGs in the BSFL gut, identifies key hosts and drivers, and provides actionable mitigation strategies for safer BSFL application.