Synergistic removal of pharmaceuticals and antibiotic resistance from ultrafiltered WWTP effluent: Free-floating ARGs exceptionally susceptible to degradation

EFSA Panel on Food Additives and Flavourings (FAF), Castle L, Andreassen M, Aquilina G, Bastos ML, Boon P, Fallico B, FitzGerald R, Frutos Fernandez MJ, Grasl‐Kraupp B, Gundert‐Remy U, Gürtler R, Houdeau E, Kurek M, Louro H, Morales P, Passamonti S, Batke M, Bruzell E, Chipman J, Cheyns K, Crebelli R, Fortes C, Fürst P, Halldorsson T, Leblanc J, Mirat M, Lindtner O, Mortensen A, Wright M, Barmaz S, Civitella C, Le Gall P, Mazzoli E, Rasinger JD, Rincon A, Tard A, Lodi F. Re-evaluation of acesulfame K (E 950) as food additive

The present opinion deals with the re-evaluation of acesulfame K (E 950) as a food additive. Acesulfame K (E 950) is the chemically manufactured compound 6-methyl-1,2,3-oxathiazin-4(3H)-one-2,2-dioxide potassium salt. It is authorised for use in the European Union (EU) in accordance with Regulation (EC) No 1333/2008. The assessment involved a comprehensive review of existing authorisations, evaluations and new scientific data. Acesulfame K (E 950) was found to be stable under various conditions; at pH lower than 3 with increasing temperatures, it is degraded to a certain amount. Based on the available data, no safety concerns arise for genotoxicity of acesulfame K (E 950) and its degradation products. For the potential impurities, based on in silico data, a concern for genotoxicity was identified for 5-chloro-acesulfame; a maximum limit of 0.1 mg/kg, or alternatively, a request for appropriate genotoxicity data was recommended. Based on the synthesis of systematically appraised evidence of human and animal studies, the Panel concluded that there are no new studies suitable for identification of a reference point (RP) on adverse effects. Consequently, the Panel established an acceptable daily intake (ADI) of 15 mg/kg body weight (bw) per day based on the highest dose tested without adverse effects in a chronic toxicity and carcinogenicity study in rats; a study considered of moderate risk of bias and one of two key studies from the previous evaluations by the Scientific Committee on Food (SCF) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA). This revised ADI replaces the ADI of 9 mg/kg bw per day established by the SCF. The Panel noted that the highest estimate of exposure to acesulfame K (E 950) was generally below the ADI in all population groups. The Panel recommended the European Commission to consider the revision of the EU specifications of acesulfame K (E 950).

Collaborative removal of microplastics, bacteria, antibiotic resistance genes, and heavy metals in a full-scale wastewater treatment plant

Plastics are used in large quantities in food packaging and industrial products in China, which results in ecological risks of microplastics (MPs) to the environment. In this study, the MPs' removal efficiency of a full-scale wastewater treatment plant (WWTP) and the internal interaction of microorganisms, antibiotic resistance genes (ARGs), and heavy metals with MPs were investigated. The dominant MPs in urban sewage were polyurethane (PU), acrylate copolymer (ACR), fluororubber, and polyethylene. MPs in wastewater were removed by WWTP with a total efficiency of 76%. The removal efficiencies of ACR, ethylene-vinyl acetate copolymer, polybutadiene, poly(tetrafluoroethylene), polystyrene, and polypropylene reached 100%. The highest concentration of MPs PU in the influent got a removal efficiency of 93.41%. The interactions between MPs, heavy metals, microorganisms, and ARGs involved adsorption, hydrogen bonds, coprecipitation, and polar interaction. Heavy metals and MPs formed larger aggregated particles, which were removed in the primary process. Heavy metals accumulated in sludge pose ecological risks to soil during landfill or compost to fertilizer. The release of MPs from WWTPs leads to accumulation in organisms and soil. It may affect the entire food chain and promote the transmission of ARGs in the environment, posing potential threats to the entire ecosystem.

Deciphering basic and key traits of bio-pollutants in a long-term reclaimed water headwater urban stream

Reclaimed water has been recognized as a stable water resource for ecological replenishment in riverine environment. However, information about the bio-pollutants spatial and temporal distributions and the associated risk in this environment remains insufficient. Herein, the bio-pollutant profile in a long-term reclaimed water headwater urban stream, including antibiotic resistance genes (ARGs), mobile genetic elements and pathogens, were revealed by metagenomics. Notably, the temporal variation in bio-pollutant levels exceeded spatial fluctuations, possibly due to the varied rainfall intensity. Specially, multidrug resistance genes and Acinetobacter baumannii (A. baumannii) were the dominant ARGs and pathogens, respectively, exhibiting higher abundance in the dry season, especially in the downstream of the receiving point, where the bio-risk also peaked. A. baumannii and Ralstonia solanacearum were found to be the main plasmids contributors inducing the horizontal gene transfer process in this stream. Overall, A. baumannii contributed over 50 % bio-risk values in most samples, indicating that it was the "overlord" in this headwater urban stream. This study revealed characteristics of bio-pollutants in a typical long-term reclaimed water headwater urban stream, highlighting the superiority of A. baumannii in bio-pollutants, which should be a key consideration in the bio-pollutants surveillance for reclaimed waters.

Fate and mitigation of antibiotics and antibiotic resistance genes in microbial fuel cell and coupled systems

Microbial fuel cells (MFCs), known for their low energy consumption, high efficiency, and environmental friendliness, have been widely utilized for removing antibiotics from wastewater. Compared to conventional wastewater treatment methods, MFCs produce less sludge while exhibiting superior antibiotic removal capacity, effectively reducing the spread of antibiotic resistance genes (ARGs). This study investigates 1) the mechanisms of ARGs generation and proliferation in MFCs; 2) the influencing factors on the fate and removal of antibiotics and ARGs; and 3) the fate and mitigation of ARGs in MFC and MFC-coupled systems. It is indicated that high removal efficiency of antibiotics and minimal amount of sludge production contribute the mitigation of ARGs in MFCs. Influencing factors, such as cathode potential, electrode materials, salinity, initial antibiotic concentration, and additional additives, can lead to the selection of tolerant microbial communities, thereby affecting the abundance of ARGs carried by various microbial hosts. Integrating MFCs with other wastewater treatment systems can synergistically enhance their performance, thereby improving the overall removal efficiency of ARGs. Moreover, challenges and future directions for mitigating the spread of ARGs using MFCs are suggested.

Change characteristics, bacteria host, and spread risks of bioaerosol ARGs/MGEs from different stages in sewage and sludge treatment process

The spread of antibiotic resistance genes (ARGs) in the atmospheric environment has seriously threatened human health. Wastewater treatment plants (WWTPs) are an important source of aerosol ARGs. A large WWTP, including sewage treatment process (SWP) and sludge treatment process (SDP), was selected in North China for sampling in this study. The content of ARGs, mobile genetic elements (MGEs), and bacterial genera in sewage/sludge and aerosols from different process stages was detected. The possible correlation between ARGs/ MGEs and bacteria was analyzed. The risk of antibiotic-resistant bacteria was evaluated and the diffusion of ARGs/MGEs was simulated. The results showed that the concentration of ARGs/MGEs varied as the process progressed, and which in the aeration tank was relatively high. The ARGs/MGEs content in SWP aerosol (8.35-163.27 copies/m3) was higher than that in SDP (5.52-16.36 copies/m3). The main ARGs/MGEs detected in SWP aerosol were tnpA-05, tnpA-04, and ermF, while the main ARGs/MGEs detected in SDP aerosol were sul1, ermF, and blaPAO. ARGs were positively correlated with most bacteria and Escherichia coli with ARGs carries higher cytotoxicity. ARGs/MGEs mainly diffused towards the southeast, which may cause harm to urban residents with the diffusion of aerosols. This study provides clues and theoretical basis for preventing the hazards of ARGs from WWTP sources.

Occurrences and implications of pathogenic and antibiotic-resistant bacteria in different stages of drinking water treatment plants and distribution systems

Different stages of drinking water treatment plants (DWTPs) play specific roles in diverse contaminants' removal present in natural water sources. Although the stages are recorded to promote adequate treatment of water, the occurrence of pathogenic bacteria (PB) and antibiotic-resistant bacteria (ARB) in the treated water and the changes in their diversity and abundance as it passed down to the end users through the drinking water distribution systems (DWDSs), is a great concern, especially to human health. This could imply that the different stages and the distribution system provide a good microenvironment for their growth. Hence, it becomes pertinent to constantly monitor and document the diversity of PB and ARB present at each stage of the treatment and distribution system. This review aimed at documenting the occurrence of PB and ARB at different stages of treatment and distribution systems as well as the implication of their occurrence globally. An exhaustive literature search from Web of Science, Science-Direct database, Google Scholar, Academic Research Databases like the National Center for Biotechnology Information, Scopus, and SpringerLink was done. The obtained information showed that the different treatment stages and distribution systems influence the PB and ARB that proliferate. To minimize the human health risks associated with the occurrence of these PB, the present review, suggests the development of advanced technologies that can promote quick monitoring of PB/ARB at each treatment stage and distribution system as well as reduction of the cost of environomics analysis to promote better microbial analysis.

Free-floating extracellular DNA (exDNA) in different wastewaters: Status quo on exDNA-associated antimicrobial resistance genes

Wastewater treatment plants (WWTPs) have been reported as major anthropogenic reservoirs for the spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) into the environment, worldwide. While most studies mainly focus on the intracellular DNA (iDNA), extracellular DNA (exDNA) accounting for a significant proportion of the total DNA in wastewater, was usually neglected. Following the One Health approach, this study focuses on wastewaters of municipal, clinical, and livestock origins (n = 45) that undergo different treatment processes (i.e., conventional activated sludge, ultrafiltration, and ozonation). Water samples were analysed for 12 ARGs as indicators of the different compartments associated with iDNA and exDNA by quantitative real-time PCR (qPCR). Taxonomic profiling of exDNA-fractions, obtained using nucleic acid adsorption particles, was conducted by sequencing the V3-V4 hypervariable regions of the 16S rRNA gene. Notified exDNA concentrations varied between on-site WWTPs and treatment stages, and ranged from 314.0 ± 70.2 ng/mL in untreated livestock wastewater down to 0.7 ± 0.1 ng/mL in effluents after ultrafiltration. In general, influents exhibited higher concentrations compared to effluents, while wastewater treated by advanced treatment processes (i.e., ultrafiltration and ozonation) showed the lowest exDNA concentrations. Despite the lower concentrations, free-floating exDNA accounted for up to 80.0 ± 5.8% of the total DNA in effluents. Target ARGs were more common in the iDNA (100%, n = 45/45), compared to the exDNA-fractions (51.1%, n = 23/45), whereas exDNA-ARGs were mostly detected in clinical and slaughterhouse wastewaters as well as in the municipal influents. Compared to the iDNA-ARGs, the concentrations of exDNA-ARGs were in general lower. Nevertheless, significant higher concentrations for exDNA-associated genes were measured in clinical wastewaters for blaNDM (4.07 ± 0.15 log gene copies (GC)/L) and blaVIM-2 (6.0 ± 0.2 log GC/L). Overall, our results suggest that depending on the origin of wastewater and its treatment methods, exDNA represents an important reservoir for ARGs, particularly in clinical wastewater.

Innovative Phospholipid Carriers: A Viable Strategy to Counteract Antimicrobial Resistance

The overuse and misuse of antibiotics have led to the emergence and spread of multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) bacteria strains, usually associated with poorer patient outcomes and higher costs. In order to preserve the usefulness of these life-saving drugs, it is crucial to use them appropriately, as also recommended by the WHO. Moreover, innovative, safe, and more effective approaches are being investigated, aiming to revise drug treatments to improve their pharmacokinetics and distribution and to reduce the onset of drug resistance. Globally, to reduce the burden of antimicrobial resistance (AMR), guidelines and indications have been developed over time, aimed at narrowing the use and diminishing the environmental spread of these life-saving molecules by optimizing prescriptions, dosage, and times of use, as well as investing resources into obtaining innovative formulations with better pharmacokinetics, pharmacodynamics, and therapeutic results. This has led to the development of new nano-formulations as drug delivery vehicles, characterized by unique structural properties, biocompatible natures, and targeted activities such as state-of-the-art phospholipid particles generally grouped as liposomes, virosomes, and functionalized exosomes, which represent an attractive and innovative delivery approach. Liposomes and virosomes are chemically synthesized carriers that utilize phospholipids whose nature is predetermined based on their use, with a long track record as drug delivery systems. Exosomes are vesicles naturally released by cells, which utilize the lipids present in their cellular membranes only, and therefore, are highly biocompatible, with investigations as a delivery system having a more recent origin. This review will summarize the state of the art on microvesicle research, liposomes, virosomes, and exosomes, as useful and effective tools to tackle the threat of antibiotic resistance.