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Microplastics and pathogen risk across ecosystems: From biofilm to antimicrobial resistance and host susceptibility
Summary
Researchers reviewing microplastic-pathogen interactions reframe the question using a vectorial-capacity lens, arguing that mere microbial detection on MP surfaces is insufficient evidence of transmission risk — and highlight that MP exposure can compromise host epithelial barriers, modulate innate immunity, and enrich antibiotic-resistant bacteria through plastisphere biofilm dynamics, though direct field-scale attribution of infection risk remains limited.
Microplastics (MPs) are ubiquitous in terrestrial and aquatic ecosystems, where they rapidly acquire organic coatings and biofilms (the plastisphere) and interact with co-occurring chemical pollutants. However, the conditions under which MPs become ecologically relevant in increasing disease risk remain underexplored. A key controversy is that microbial detection or enrichment on MPs is often treated as evidence of pathogen "vectoring," yet most studies do not quantify viability/infectivity, detachment, or delivered dose to hosts under environmentally realistic conditions. This review synthesizes evidence on MP-pathogen interactions and dispersal across ecosystems and reframes "MPs as vectors" through a vectorial-capacity lens that distinguishes association from transmission relevance and links MP-mediated risk to measurable dose delivery at host-relevant interfaces. Across ecosystems, evidence supports biofilm-driven persistence and enrichment of opportunistic taxa, but direct demonstrations of MP-mediated infection remain limited. We further highlight an unresolved issue, whether MPs confer unique transmission advantages compared with size-matched natural particulates that also sorb microbes and contaminants but are rarely used as comparators. We examine host susceptibility as a risk multiplier: MP exposure can compromise epithelial barriers via oxidative stress, modulate innate immunity, and disrupt microbiome-mediated colonization resistance. Plastisphere biofilms may also function as eco-evolutionary microhabitats that enrich antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), with plausible enhancement of horizontal gene transfer, although field-scale attribution is still scarce. Finally, we outline priorities for standardized evidence grading, comparator-based study designs, and quantitative metrics (loading, viability decay, detachment kinetics) to enable risk attribution and guide monitoring and mitigation.