Microplastics　(MPs)　in　aquatic　environments　provide　a　new　ecological　niche　that　facilitates　the　attachment　of　antibiotic-resistance　genes　(ARGs)　and　pathogens.　However,　the　effect　of　particle　size　on　the　colonization　of　antibiotic　resistomes　and　pathogens　remains　poorly　understood.　To　address　this　knowledge　gap,　this　study　explored　the　antibiotic　resistome　and　core　microbiome　on　three　distinct　types　of　MPs　including　polyethylene,　polypropylene,　and　polystyrene　(PS),　with　varying　sizes　of　30,　200,　and　3000　μm　by　metagenomic　sequencing.　Our　finding　showed　that　the　ARG　abundances　of　the　PS　type　increased　by　4-folds　with　increasing　particle　size　from　30　to　3000　μm,　and　significant　differences　in　ARG　profiles　were　found　across　the　three　MP　types.　In　addition,　the　concentrations　of　ARGs　and　mobile　genetic　elements　(MGEs)　were　markedly　higher　in　the　MPs　than　in　the　surrounding　water,　indicating　their　enrichment　at　these　artificial　interfaces.　Notably,　several　pathogens　such　as　Pseudomonas　aeruginosa,　Mycobacterium　tuberculosis,　and　Legionella　pneumophila　were　enriched　in　MP　biofilms,　and　the　co-occurrence　of　ARGs　and　virulence　factor　genes　(VFGs)/MGEs　suggested　the　presence　of　pathogenic　antibiotic-resistant　microbes　with　potential　mobility.　Both　redundancy　analysis　(RDA)　and　structural　equation　modeling　(SEM)　demonstrated　that　physicochemical　properties　such　as　zeta　potential,　MP　size,　and　contact　angle　were　the　most　significant　contributors　to　the　antibiotic　resistome.　Strikingly,　no　significant　differences　were　observed　in　the　health　risk　scores　of　the　ARG　profiles　among　different　sizes　and　types　of　MPs.　This　study　expands　our　knowledge　on　the　impact　of　MP　size　on　microbial　risks,　thus　enhancing　our　understanding　of　the　potential　health　hazards　they　pose.　©　2024　Elsevier　B.V.