Selective enrichment of antibiotic resistome and bacterial pathogens by aquatic microplastics

In the aquatic environment, plastic wastes, including microplastics (MPs), are colonized by bacterial communities (BCs), forming dynamic biofilms, which promote the development and spread of antibiotic resistome (AR) such as antibiotic-resistant bacteria (ARB), antibiotic-resistant genes (ARGs), and multi-drug resistant genes (MDRGs). Thus, this review combines studies on abundance of BCs, AR, and bacterial pathogens in the plastics (primarily MPs) and free-living fractions in various aquatic environments (freshwater, seawater, and wastewater). Previous research studies revealed that plastics provide novel microbial niche and selectively enrich BCs containing AR elements, implying that plastics may exhibit a more diverse bacterial population compared to that in the surrounding water. However, compared to the planktonic bacteria, plastic-associated bacteria contain a higher abundance of mobile genetic elements (MGEs), which are excellent biomarkers of horizontal gene transfer (HGT), highlighting the elevated dissemination of AR elements by plastics in the aquatic environment. Further, most commonly reported potentially pathogenic bacterial strains on MPs were associated with Vibrio, Pseudomonas, and Acinetobacter genera, including well-known plant, fish, and human pathogens. The antibiotic resistome and pathogens in the plastisphere can be affected by several factors such as MGE abundance and type, characteristics of plastics, BC structure and density, incubation period, anthropogenic chemicals, and medium qualities all have a role in the generation and transmission of MP-associated AR and pathogens in the aquatic environment. Furthermore, the nexus between biotic (BCs, ARGs, ARB, MGEs, and pathogens) and abiotic (physicochemical parameters) elements, the multifaceted ecological and human health impacts, as well as future research perspectives and remedial measures against plastisphere associated AR and pathogens in the global aquatic environment, are also highlighted in this review.