The effect of carbon-based copper nanocomposites on Microcystis aeruginosa and the movability of antibiotic resistance genes in urban water

Performance of pharmaceutical products removal in a bioelectrochemical system at low temperatures and changes in microbial communities and antibiotic resistance genes

Biological methods do not effectively remove pharmaceutical products (PPs) and antibiotic resistance genes (ARGs) from wastewater at low temperatures, leading to environmental pollution. Therefore, anaerobic-aerobic-coupled upflow bioelectrochemical reactors (AO-UBERs) were designed to improve the removal of PPs at low temperatures (10 ± 2 °C). The result shows that diclofenac (DIC) and ibuprofen (IBU) removals in the system with aerobic anodic and anaerobic cathodic chambers were 91.7% and 94.7%, higher than that in the control system (12.2 ± 1.5%, 36.5 ± 5.9%), and aerobic zone favors DIC and IBU removal; fluoroquinolone antibiotics (FQs) removals in the system with aerobic cathodic and anaerobic anodic chambers were 17.5-22.4% higher than that in the control system (9.1-22.4%), and anaerobic zone favors FQs removal. Analysis of microbial community structure and ARGs showed that different electrotrophic microbes (Flavobacterium, Acinetobacter, and Delftia) with cold-resistant ability to degrade PPs were enriched in different electrode combinations, and the aerobic cathodic chambers could remove certain ARGs. These results showed that AO-UBERs under intermittent electrical stimulation mode are an alternative method for the effective removal of PPs and ARGs at low temperatures.

Mitigated toxicity of polystyrene nanoplastics in combination exposure with copper ions by transformation into copper (I) oxide: Inhibits the oxidative potential of nanoplastics

The combined impact of trace metals and polystyrene (PS) microplastics is extremely concerning for human health because PS microplastics can serve as a vehicle for other contaminants. Herein, we investigated the combined effect of copper ions (Cu2+) on the toxicity of PS nanoplastics in vivo and in vitro. The pristine PS (PPS) and ultraviolet irradiated oxidized PS (OPS) nanoplastics with 50 nm-size were conjugated with Cu2+ (13-27 mg/g) for 4 days to get four types of samples: PPS, OPS, PPS/Cu, and OPS/Cu. The comparative toxic potentials of test samples were evaluated using a mouse pharyngeal aspiration model and relevant human cell lines (A549 and differentiated THP-1 cells). The results showed an antagonistic effect in vivo and in vitro by the presence of Cu ions: PPS > PPS/Cu; OPS > OPS/Cu. Furthermore, the OPS produced significantly increased toxic potentials compared to the corresponding PPS: OPS > PPS; OPS/Cu > PPS/Cu. The antagonistic effect of Cu2+ on the toxicity of PS was due to the transformation of Cu2+ and balanced the surface charge of the nanoplastics, which inhibited the oxidative potential of corresponding nanoplastics. These antagonistic effects may provide a better understanding of the combined effects of metals on the intrinsic toxic potential of microplastics under natural conditions.

Different fates of extracellular and intracellular antibiotic resistance genes in flocs, granular and biofilm nitrification systems under the stress of acetaminophen

The spread of antibiotic resistance genes (ARGs), including intracellular ARGs (i-ARGs) and extracellular ARGs (e-ARGs), has become a global problem that cannot be ignored. This study clarified the fates of e-ARGs and i-ARGs in floc sludge reactor (FS), granular sludge reactor (GS) and biofilm reactor (BF) under the stress of acetaminophen (APAP). The results showed that the risk of ARGs transmission, especially for e-ARGs, in FS and BF could increase with the increasing times of APAP treatment, except for that in GS. The fates of i-ARGs in three different systems were similar, which were mainly clustered as the efflux pumps mechanism. The secretion and disintegration of extracellular polymeric substances mainly affected the fates of e-ARGs. In the three systems, the complexity of network relationships between ARGs and microbial communities was FS, GS and BF. Partial least-squares path model analysis indicated that bacterial community directly contributed to the variations of e-ARGs and i-ARGs under APAP treatment in the three systems, playing a leading role. And i-ARGs and protein secondary structure showed direct effects on e-ARGs. This study indicated that e-ARGs in complex systems were more susceptible to be influenced, which should be paid more attention to prevent further propagation of ARGs.

Prevalence of antimicrobial resistance in a full-scale drinking water treatment plant

Antibiotic resistance in drinking water has received increasing attention in recent years. In this study, the occurrence and abundance of antibiotic resistance genes (ARGs) in a drinking water treatment plant (DWTP) was comprehensively investigated using metagenomics. Bioinformatics analysis showed that 381 ARG subtypes belonging to 15 ARG types were detected, and bacitracin had the highest abundance (from 0.26 × 10-2 to 0.86 copies/cell), followed by multidrug (from 0.57 × 10-1 to 0.47 copies/cell) and sulfonamide (from 0.83 × 10-2 to 0.35 copies/cell). Additionally, 933 ARG-carrying contigs (ACCs) were obtained from the metagenomic data, among which 153 contigs were annotated as pathogens. The most abundant putative ARG host was Staphylococcus (7.9%), which most frequently carried multidrug ARGs (43.2%). Additionally, 38 high-quality metagenome-assembled genomes (MAGs) were recovered, one of which was identified as Staphylococcus aureus (Bin.624) and harboured the largest number of ARGs (n = 16). Using the cultivation technique, 60 isolates were obtained from DWTP samples, and Staphylococcus spp. (n = 11) were found to be dominant in all isolates, followed by Bacillus spp. (n = 17). Antimicrobial susceptibility testing showed that most Staphylococcus spp. were multidrug resistant (MDR). These results deepen our understanding of the distribution profiles of ARGs and antibiotic resistant bacteria (ARB) in DWTPs for potential health risk evaluation. Our study also highlights the need for new and efficient water purification technologies that can be introduced and applied in DWTPs.

The significance of metallic nanoparticles in the emerging, development and spread of antibiotic resistance

An ever-increasing number of newly synthesised nanoparticles have a constantly expanding range of applications. The large-scale implementation of nanoparticles will inevitably lead to intentional or accidental contamination of various environments. Since the major benefit of using several metallic nanoparticles is antimicrobial activity, these emerging contaminants may have a potentially hazardous impact on the development and spread of antibiotic resistance - a challenge that threats infection therapy worldwide. Few studies underline that metallic nanoparticles may affect the emergence and evolution of resistance via mutations and horizontal transfer between different bacterial species. Due to the complexity of factors and mechanisms involved in disseminating antibiotic resistance, it is crucial to investigate if metallic nanoparticles play a significant role in this process through co-selection ability and pressure exerted on bacteria. The aim of this review is to summarise the current research on mutations and three main horizontal gene transfer modes facilitated by nanoparticles. Here, the current results in the field are presented, major knowledge gaps and the necessity for more environmentally relevant studies are discussed.

Cyanobacterial blooms: A player in the freshwater environmental resistome with public health relevance?

Cyanobacterial harmful algal blooms (cyanoHABs) are an ecological concern because of large ecosystem-disrupting blooms and a global public health concern because of the cyanotoxins produced by certain bloom-forming species. Another threat to global public health is the dissemination of antibiotic resistance (AR) in freshwater environmental reservoirs from anthropogenic sources, such as wastewater discharge and urban and agricultural runoff. In this study, cyanobacteria are now hypothesized to play a role in the environmental resistome. A non-systematic literature review of studies using molecular techniques (such as PCR and metagenomic sequencing) was conducted to explore indirect and direct ways cyanobacteria might contribute to environmental AR. Results show cyanobacteria can host antibiotic resistance genes (ARGs) and might promote the spread of ARGs in bacteria due to the significant contribution of mobile genetic elements (MGEs) located in genera such as Microcystis. However, cyanobacteria may promote or inhibit the spread of ARGs in environmental freshwater bacteria due to other factors as well. The purpose of this review is to 1) consider the role of cyanobacteria as AR hosts, since cyanoHABs are historically considered to be a separate problem from AR, and 2) to identify the knowledge gap in understanding cyanobacteria as ARG reservoirs. Cyanobacterial blooms, as well as other biotic (e.g. interactions with protists or cyanophages) and abiotic factors, should be studied further using advanced methods such as shotgun metagenomic and long read sequencing to clarify the extent of their functional ARGs/MGEs and influences on environmental AR.

Antibiotic Resistance in the Drinking Water: Old and New Strategies to Remove Antibiotics, Resistant Bacteria, and Resistance Genes

Bacterial resistance is a naturally occurring process. However, bacterial antibiotic resistance has emerged as a major public health problem in recent years. The accumulation of antibiotics in the environment, including in wastewaters and drinking water, has contributed to the development of antibiotic resistant bacteria and the dissemination of antibiotic resistance genes (ARGs). Such can be justified by the growing consumption of antibiotics and their inadequate elimination. The conventional water treatments are ineffective in promoting the complete elimination of antibiotics and bacteria, mainly in removing ARGs. Therefore, ARGs can be horizontally transferred to other microorganisms within the aquatic environment, thus promoting the dissemination of antibiotic resistance. In this review, we discuss the efficiency of conventional water treatment processes in removing agents that can spread/stimulate the development of antibiotic resistance and the promising strategies for water remediation, mainly those based on nanotechnology and microalgae. Despite the potential of some of these approaches, the elimination of ARGs remains a challenge that requires further research. Moreover, the development of new processes must avoid the release of new contaminants for the environment, such as the chemicals resulting from nanomaterials synthesis, and consider the utilization of green and eco-friendly alternatives such as biogenic nanomaterials and microalgae-based technologies.