Promotion of antibiotic-resistant genes dissemination by the micro/nanoplastics in the gut of snail Achatina fulica

Terrestrial animal intestines are hotspots for the enrichment of micro/nano plastics (M/NPs) and antibiotic-resistant genes (ARGs). However, little is known about the further impact of M/NPs on the spread of ARGs in animal guts. This study investigates the role of M/NPs (polystyrene) with varying particle sizes (0.082, 42, and 182 μm), concentrations (10 and 100 mg/L), and exposure durations (4 and 16 days) in the ARGs dissemination via conjugation in the edible snail (Achatina fulica) gut. Combination of qPCR with 16S rRNA-based sequencing, we found that PS exposure caused intestinal cell impairment and shifts in the gut microbial community of snails. Conjugation rate increased with PS particle sizes in the snail gut. After 4 days of exposure, significantly higher conjugation rates were observed in the gut exposed to 100 mg/L PS compared to 10 mg/L, however, this trend reversed after 16 days. Consistently, the abundances of conjugation relevant genes trfA and trbB shared similar trends to the conjugation ratios in the snail gut after PS exposure. Transconjugant diversity was much lower in 10 mg/L PS groups than in 100 mg/L PS treatments. Therefore, this study suggests that the presence of M/NPs would complicate management of ARG spread. The selection pressure exerted by M/NPs may sustain or even amplify the spread of ARGs in the gut of terrestrial animals even in the absence of antibiotics. It highlights the necessity of avoiding M/NPs intake as a part of comprehensive strategy for cubing ARG dissemination in the gut of animals.