Evaluation of the potential risks of antibioticresistant bacteria and genes (ARBs & ARGs), and microplastics (MPs); and monitoring of their removal in water treatment processes

Abstract

Antibiotic resistance poses a significant threat to global health, food security, and development. It has led to longer hospital stays, higher medical costs, and increased mortality rates [1]. Additionally, there is a concern over microplastics (MPs) in the environment. Plastics that end up in the environment stay for centuries and degrade into small pieces (< 5mm) called MPs. MPs are also produced deliberately and added to various products. At present, there is no allencompassing European legislation that deals with MPs. The existing proposition by the European Commission is to limit MPs under the REACH Regulation (EC No 1907/2006) [2]. MP pollution was also included in the European Union´s proposal by the Marine Strategy Framework Directive (MSFD,2008/56/EC) [3]. However, there are no prescribed minimal reductions for MPs, antibiotics, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) in water and wastewater treatment guidelines [4]. MPs, ARB, and ARGs continue to persist as global pollutants in both natural and engineered water systems. Twelve bacterial families are included in the list of priority pathogens for antibiotic resistance [1]. The spread of ARB and ARGs through water is a matter of great concern and identifying the ARG carriers isolated in wastewater treatment plant (WWTP) effluent is critical in determining the potential threat to human health caused by antibiotic resistance. MPs in water bodies are considered a novel microbial niche with the potential to act as a vector for ARGs and pathogens to new environments, spreading the associated health risk across environmental compartments and the aquatic food-chain [5]. Wu et al. [6] studied the bacterial pathogens in MP biofilm and found that the MP biofilm had a distinctive resistome as compared to the rock and leaf particles in the same water matrix. Furthermore, ARGs in three pathogens were found in MP biofilm only, indicating ARG enrichment by MP biofilm as compared to natural particles. The MP biofilm has the potential to spread antibiotic resistance, alter marine bacterial communities and pose health hazards [7]. Therefore, there is a possibility of MP bound pathogens acquiring ARGs from the surrounding environment and traveling to remote environmental compartments. Previous studies also identified opportunistic pathogens in MP biofilm [8]. Furthermore, a potential connection is anticipated between WWTP derived bacteria and the intl1 abundance in the plastisphere. It could be due to the ability of even small amounts of sewage effluent to enhance the intl1 prevalence in freshwater biofilm without alteration of the ambient water microbial community [9]. The environmental factors along with the physicochemical properties of MPs are important in the determination of bacterial ecology in the MP biofilm.