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From gut lumen to extragut tissue: dysbiosis-induced gut bacterial translocation mediates antibiotic resistance gene enrichment in Eisenia fetida under polystyrene microplastic and roxithromycin exposure
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Scientists found that when earthworms are exposed to both microplastics and a common antibiotic, harmful gut bacteria and antibiotic-resistant genes can leak out of the gut and spread into the worm's body tissue. This matters because these worms are used in some traditional medicines and can enter the food chain, meaning this combo of pollution could help antibiotic resistance travel from soil into things people eat or use—making it harder to treat infections down the line.
Microplastics' (MPs) capacity to sorb antibiotics in soil ecosystems poses emerging risks, yet their combined toxic effects on soil fauna remain poorly understood. Consequently, we examined the gut toxicity and antibiotic resistance genes (ARGs) of polystyrene MPs (PS-MPs) and the macrolide antibiotic roxithromycin (ROX) in Eisenia fetida. Overall, although co-exposure suppressed gut barrier gene expression (occludin and ZO-1), it did not worsen bacterial translocation (LPS and LBP) relative to single exposures, which is associated with the significant upregulation of antibacterial defense indicators (TLR and CCF), potentially enhancing bacterial clearance. Additionally, PS-MPs mediated the reduction of ROX bioaccumulation by 34.78%, which contributed to the antagonistic interactions observed across multiple indicators, including attenuated deterministic assembly of gut microbiota and ARGs under co-exposure. Beyond enriching resistant Actinobacteria (e.g., Streptomyces and Actinophytocola), ROX also enriched plastisphere-associated pathogenic taxa Escherichia and Enterococcus, as did PS-MPs. These taxa were closely implicated in gut barrier dysfunction and exhibited the strongest correlations with gut ARGs and mobile genetic elements (MGEs) profiles, particularly macrolide-lincosamide-streptogramin B (MLSB) resistance genes (mphA-01, oleC) and MGEs (intI-1(clinic), tnpA-02). Though co-exposure did not increase gut ARGs and MGEs abundance, the enrichment of gut-dominant MLSB resistance genes and MGEs extended to earthworm body tissue, notably driven by PS-MPs, while ROX increased intI-1 (clinic), the strongest contributor to overall variation. PLS-PM revealed that tissue ARGs and MGEs enrichment was associated with gut bacterial translocation driven by dysbiosis-induced activation of LPS-TLR signaling pathways, raising concerns about ARGs dissemination through earthworm-derived traditional medicine and food chains.
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Ecotoxicological effects of polyethylene microplastics on earthworms (Eisenia fetida) in tetracycline-contaminated soil: Oxidative stress, intestinal barrier damage, and metabolic reprogramming
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Scientists found that when microplastics and antibiotic residue (tetracycline) mix together in soil, they cause even more damage to earthworms than either pollutant alone — harming their gut tissue, disrupting their energy production, and overwhelming their natural defense systems. Since earthworms are a key indicator of soil health, and soil health underpins the food we grow, this suggests that the growing combo of plastic waste and antibiotic pollution in farmland could pose bigger risks to ecosystems (and potentially our food supply) than scientists previously realized by studying these pollutants separately.
Pivotal role of earthworm gut protists in mediating antibiotic resistance genes under microplastic and sulfamethoxazole stress in soil–earthworm systems
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Researchers found that gut protists in earthworms play a pivotal role in mediating the spread of antibiotic resistance genes when earthworms are co-exposed to microplastics and antibiotics in soil, identifying a previously overlooked biological pathway for AMR dissemination.
Low-density polyethylene enhances the disturbance of microbiome and antibiotic resistance genes transfer in soil-earthworm system induced by pyraclostrobin
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When earthworms were exposed to both polyethylene microplastics and a common fungicide (pyraclostrobin), the microplastics increased the pesticide's absorption into the earthworms' bodies and caused more severe oxidative damage than either pollutant alone. The combination also dramatically increased antibiotic resistance genes in both the soil and earthworm gut. This is concerning because it shows microplastics in farmland can amplify the spread of antibiotic resistance, a major threat to human medicine.
Polyvinyl chloride microplastic triggers bidirectional transmission of antibiotic resistance genes in soil-earthworm systems
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This study found that PVC microplastics in soil trigger a two-way spread of antibiotic resistance genes between earthworm guts and the surrounding soil. The microplastics increased both the diversity and abundance of these resistance genes, with the transfer happening through bacteria sharing genetic material. This is concerning because earthworms are essential for soil health, and microplastics may be turning soil ecosystems into breeding grounds for antibiotic-resistant bacteria.
Microplastics combined with tetracycline in soils facilitate the formation of antibiotic resistance in the Enchytraeus crypticus microbiome
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Soil invertebrates (Enchytraeus crypticus) were exposed to microplastics and tetracycline alone and in combination; combined exposure promoted greater shifts in gut microbiome composition and higher levels of antibiotic resistance genes than either stressor alone, suggesting microplastics exacerbate antibiotic resistance spread in soil.
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