Urban organic manure application enhances antibiotic resistance gene diversity and potential human pathogen abundance in invasive giant African snails

The giant African snail (Achatina fulica) is an invasive species served as potential vectors for antibiotic resistance genes (ARGs) and potential human bacterial pathogens. Currently, urban green spaces receive extensive organic manure additions as part of their management, may intensify the biological contamination potential of these snail vectors, thereby increasing the risk of biological pollution in green spaces. However, the specific impacts of this practice on the microbial ecology of these invasive species remain poorly understood. Here, we investigated the effects of organic manure application on the gut microbiome of giant African snails, focusing on ARGs, bacterial community structure, and potential human bacterial pathogens. Microcosm experiments compared snail gut microbiomes in different treatments (Soil: soil samples collected after manure amendment, before any snail exposure. Feces: fecal samples collected from snails that lived on manure-amended soil. Control: fecal samples collected from snails that lived on unamended soil) using 16S rRNA high-throughput sequencing and metagenomic analysis. Our results show that manure application significantly altered gut bacterial community structure and increased ARG diversity by enriching specific high-risk ARGs (such as sul1 and sul2 in the Feces group increased by 2.89 and 2.43 times, respectively, compared to the Control group), and the introduction of eight novel ARG subtypes, despite decreasing overall ARG abundance. Moreover, the relative abundance of potential human pathogens, particularly Pseudomonadaceae, was greatly increased by manure application. These findings reveal that organic manure application in urban green spaces can potentially enhances their role as reservoirs and vectors of ARGs and human pathogens.