Growth Stage-Dependent Variations of Antibiotic Resistance and Potential Pathogens in Earthworm Gut: Potential Risk to Soil Health

Under the “One Health” framework, microbial
resistance
and pathogenicity across environments and animals pose significant
health threats and have become a global issue. Although antibiotic
resistance genes (ARGs) in earthworm guts and their influence on soil
ARGs have been studied, how earthworm life stages affect ARGs and
potential pathogens in the gut and soil remains unclear. Here, we
assessed intestinal ARGs and virulence factor genes (VFGs) during
earthworm development (egg, juvenile, and adult) and their influence
on soil ARGs and potential pathogens. Our results showed that ARGs
and potential pathogens were widespread and varied within earthworm
guts at different growth stages. Earthworm guts harbored significantly
(p < 0.05) fewer high-risk ARGs than soil, indicating
potential roles of earthworms in soil ARG mitigation. Conversely,
potential pathogens were significantly (p < 0.05)
higher in guts than in soil. We further found that earthworms across
life stages increased soil potential pathogens and reinforced ARG-mobile
genetic element (MGE)-pathogen linkages in the soil ecosystem. ARG
spread in earthworm guts relied more on vertical transmission than
horizontal gene transfer (HGT). These results suggest that earthworms
harbor abundant and diverse ARGs and potential pathogens, influencing
soil microbiota and resistomes, which reveal earthworm-associated
risks to soil ecosystem health.