Distribution, sources, and potential risks of antibiotic resistance genes in wastewater treatment plant: A review

Occurrence and environmental fate of anti-influenza drugs in a subcatchment of the Yodo River Basin, Japan

Understanding the current situation and risk of environmental contamination by anti-influenza drugs in aquatic environments is key to prevent the unexpected emergence and spread of drug-resistant viruses. However, few reports have been focused on newer drugs that have recently been introduced in clinical settings. In this study, the behaviour of the prodrug baloxavir marboxil (BALM)-the active ingredient of Xofluza, an increasingly popular anti-influenza drug-and its pharmacologically active metabolite baloxavir (BAL) in the aquatic environment was evaluated. Additionally, their presence in urban rivers and a wastewater treatment plant (WWTP) in the Yodo River basin was investigated and compared with those of the major anti-influenza drugs used to date (favipiravir (FAV), peramivir (PER), laninamivir (LAN), and its active metabolite, laninamivir octanoate (LANO), oseltamivir (OSE), and its active metabolite, oseltamivir carboxylate (OSEC), and zanamivir (ZAN)) to comprehensively assess their environmental fate in the aquatic environment. The results clearly showed that BALM, FAV, and BAL were rapidly degraded through photolysis (2-h, 0.6-h, and 0.4-h half-lives, respectively), followed by LAN, which was gradually biodegraded (7-h half-life). In addition, BALM and BAL decreased by up to 47 % after 4 days and 34 % after 2 days of biodegradation in river water. However, the remaining conventional drugs, except for LANO (<1 % after 10 days), were persistent, being transported from the upstream to downstream sites. The LogKd values for the rates of sorption of BALM (0.5-1.6) and BAL (1.8-3.1) on river sediment were higher than those of conventional drugs (-0.5 to 1.7). Notably, all anti-influenza drugs were effectively removed by ozonation (>90-99.9 % removal) after biological treatment at a WWTP. Thus, these findings suggest the importance of introducing ozonation to reduce pollution loads in rivers and the environmental risks associated with drug-resistant viruses in aquatic environments, thereby promoting safe river environments.

Enhanced removal of antibiotic-resistant bacteria and resistance genes by three-dimensional electrochemical process using MgFe2O4-loaded biochar as both particle electrode and catalyst for peroxymonosulfate activation

In this study, MgFe2O4-loaded biochar (MFBC) was used as a three-dimensional particle electrode to active peroxymonosulfate (EC/MFBC/PMS) for the removal of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). The results demonstrated that, under the conditions of 1.0 mM PMS concentration, 0.4 g/L material dosage, 5 V voltage intensity, and MFBC preparation temperature of 600 °C, the EC/MFBC600/PMS system achieved complete inactivation of E. coli DH5α within 5 min and the intracellular sul1 was reduced by 81.5 % after 30 min of the treatment. Compared to EC and PMS alone treatments, the conjugation transfer frequency of sul1 rapidly declined by 92.9 % within 2 min. The cell membrane, proteins, lipids, as well as intracellular and extracellular ARGs in E. coli DH5α were severely damaged by free radicals in solution and intracellular reactive oxygen species (ROS). Furthermore, up-regulation was observed in genes associated with oxidative stress, SOS response and cell membrane permeability in E. coli DH5α, however, no significant changes were observed in functional genes related to gene conjugation and transfer mechanisms. This study would contribute to the underlying of PMS activation by three-dimensional particle electrode, and provide novel insights into the mechanism of ARB inactivation and ARGs degradation under PMS advanced oxidation treatment.

Nature-based bioreactors: Tackling antibiotic resistance in urban wastewater treatment

The overuse and misuse of antibiotics have accelerated the selection of antibiotic-resistant bacteria, significantly impacting human, animal, and environmental health. As aquatic environments are vulnerable to antibiotic resistance, suitable management practices should be adopted to tackle this phenomenon. Here we show an effective, nature-based solution for reducing antibiotic resistance from actual wastewater. We utilize a bioreactor that relies on benthic (biofilms) and planktonic microbial communities to treat secondary effluent from a small urban wastewater treatment plant (<10,000 population equivalent). This treated effluent is eventually released into the local aquatic ecosystem. We observe high removal efficiency for genes that provide resistance to commonly used antibiotic families, as well as for mobile genetic elements that could potentially aid in their spread. Importantly, we notice a buildup of sulfonamide (sul1 and sul2) and tetracycline (tet(C), tet(G), and tetR) resistance genes specifically in biofilms. This advancement marks the initial step in considering this bioreactor as a nature-based, cost-effective tertiary treatment option for small UWWTPs facing antibiotic resistance challenges.

Antibiotic resistance genes risks in relation to host pathogenicity and mobility in a typical hospital wastewater treatment process

Hospital wastewaters (HWWs) serve as critical reservoirs for disseminating antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB). However, the dynamics and noteworthy shifts of ARGs and their associated pathogenicity, mobility, and resistome risks during HWWs treatment processes remain poorly understood. Utilizing metagenomic sequencing and assembly, we identified 817 ARG subtypes conferring resistance to 20 classes of antibiotics across 18 HWW samples from influent to effluent. Genes encoding resistance to multidrug, aminoglycoside and beta_lactam were the most prevalent ARG types, reflecting patterns observed in clinical settings. On-site treatment efforts decreased the relative abundance of ARGs by 77.4% from influent to secondary sedimentation, whereas chlorine disinfection significantly increased their abundance in the final effluent. Deterministic processes primarily drove the taxonomic assembly, with Proteobacteria being the most abundant phylum and serving as the primary host for 15 ARG types. Contig-based analysis further revealed 114 pathogenic ARB, with Escherichia coli, Pseudomonas alcaligenes, and Pseudomonas aeruginosa exhibiting multidrug-resistant. The contributions of host bacteria and pathogenic ARB varied throughout wastewater treatment. In addition, 7.10%-31.0 % ARGs were flanked by mobile genetic elements (MGEs), predominantly mediated by transposase (74.1%). Notably, tnpA exhibited the highest potential for ARG dissemination, frequently co-occurring with beta-lactam resistance genes (35.2%). Considering ARG profiles, pathogenic hosts, and transferability, raw influent exhibited the highest antibiotic resistome risk index (ARRI), followed by the final effluent. Chlorine disinfection exacerbated resistome risks by inducing potential pathogenic ARB and mobile ARGs, posing threats to the receiving environment. This study delineates ARG occurrence patterns, highlights mechanisms of ARG carriage and horizontal gene transfer, and provides insights for assessing resistance risks and prioritizing interventions in clinical settings.

Towards the definition of an antibiotic resistome signature in wastewater and downstream environments

Domestic wastewater is a significant reservoir of antibiotic resistance genes, which pose environmental and public health risks. We aimed to define an antibiotic resistome signature, represented by core genes, i.e., shared by ≥ 90% of the metagenomes of each of three conceptual environmental compartments - wastewater (influent, sludge, effluent), freshwater, and agricultural soil. The definition of resistome signatures would support the proposal of a framework for monitoring treatment efficacy and assessing the impact of treated wastewater discharge into the environment, such as freshwater and agricultural soil. Metagenomic data from 163 samples originating from wastewater (n = 81), freshwater (n = 58), and agricultural soils (n = 24) across different regions (29 countries, 5 continents), were analysed regarding antibiotic resistance diversity, based on annotation against a database that merged CARD and ResFinder databases. The relative abundance of the total antibiotic resistance genes (corresponding to the ratio between the antibiotic resistance genes and total reads number) was not statistically different between raw and treated wastewater, being significantly higher than in freshwater or agricultural soils. The latter had the significantly lowest relative abundance of antibiotic resistance genes. Genes conferring resistance to aminoglycosides, beta-lactams, and tetracyclines were among the most abundant in wastewater environments, while multidrug resistance was equally distributed across all environments. The wastewater resistome signature included 27 antibiotic resistance genes that were detected in at least 90% of the wastewater resistomes, and that were not frequent in freshwater or agricultural soil resistomes. Among these were genes responsible for resistance to tetracyclines (n = 8), macrolide-lincosamide-streptogramin B (n = 7), aminoglycosides (n = 4), beta-lactams (n = 3), multidrug (n = 2), sulphonamides (n = 2), and polypeptides (n = 1). This comprehensive assessment provides valuable insights into the dynamics of antibiotic resistance in urban wastewater systems and their potential ecological implications in diverse environmental settings. Furthermore, provides guidance for the implementation of One Health monitoring approaches.

Occurrence and human exposure risk of antibiotic resistance genes in tillage soils of dryland regions: A case study of northern Ningxia Plain, China

Agricultural soils are important source and sink of antibiotic resistance genes (ARGs). However, little is known about the fate of ARGs in dryland soils, while its human exposure risks were seriously overlooked. Taking the northern Ningxia Plain as a case, this study explored the occurrence of ARGs and its relationship with mobile genetic elements (MGEs), pathogens, and environmental factors. Furthermore, the concentrations of airborne ARGs by soil wind erosion and the human exposure doses of soil ARGs were evaluated. The results showed the abundances of different regions ranged from 4.0 × 105 to 1.6 × 106 copies/g. Soil ARGs are driven by MGEs, but multiply impacted by soil properties, nutrition, and bacterial community. Vibrio metschnikovii, Acinetobacter schindleri, and Serratia marcescens are potential pathogenic hosts for ARGs. Further exploration revealed the concentration of ARGs loaded in dust by soil wind erosion reached more than 105 copies/m3, which were even higher than those found in sewage treatment plants and hospitals. Skin contact is the primary route of ARGs exposure, with a maximum dose of 24071.33 copies/kg/d, which is largely attributed to ARGs loaded in dust. This study bridged the gap on ARGs in dryland soils, and provided reference for human exposure risk assessment of soil ARGs.

Development of a new synchronous fluorescence spectrometry combined with Al3+ sensitized for simultaneous and rapid determination of trace flumequine, ciprofloxacin and doxycycline hydrochloride residues in wastewater

Antibiotics are a new type of environmental pollutants. Due to its wide application in many fields, antibiotic residues are ubiquitous in the wastewater environments. Given their potential threat on water ecosystem functioning and public health, the detection of antibiotic residues in wastewater environments has become very necessary. Based on the complexation of Al3+ with flumequine (FLU), ciprofloxacin (CIP) and doxycycline hydrochloride (DOX), their molecular conjugated area were increased and fluorescence intensity were enhanced, combined with synchronous fluorescence spectrometry (SFS) had good selectivity and high sensitivity, a novel method of Al3+ sensitized synchronous fluorescence spectrometry for the determination of FLU, CIP and DOX residues in wastewater was established. When the wavelength difference (Δλ) was selected 115.0 nm, synchronous fluorescence spectra of the three antibiotics could be well separated and the interference of wastewater matrix were eliminated primely. The new SFS made good use of spectral separation instead of conventional chemical separation, and the actual wastewater sample could be directly determined after simple filtration. The experiment results showed that the concentrations of FLU, CIP and DOX in the range of 0.5000-800.0 ng·mL-1, 0.5000-640.0 ng·mL-1 and 10.00-3500 ng·mL-1 had a good linear relationship with fluorescence intensity. The detection limits of three antibiotics were 0.02054 ng·mL-1, 0.03956 ng·mL-1 and 0.8524 ng·mL-1, respectively. Recovery rates of three antibiotics in wastewater samples were 90.72%-98.23%, 88.68%-95.08% and 85.94%-96.70%. The new SFS established in this experiment had the advantages of simple, rapid, sensitive, accurate and good selectivity. Simultaneous and rapid detection of FLU, CIP and DOX residues in wastewater was successfully realized. It had good application prospects in real-time water quality monitoring.

Spatiotemporal distribution of the planktonic microbiome and antibiotic resistance genes in a typical urban river contaminated by macrolide antibiotics

The widespread application of macrolide antibiotics has caused antibiotic resistance pollution, threatening the river ecological health. In this study, five macrolide antibiotics (azithromycin, clarithromycin, roxithromycin, erythromycin, and anhydro erythromycin A) were monitored in the Zao River across three hydrological periods (April, July, and December). Simultaneously, the changes in antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and planktonic bacterial communities were determined using metagenomic sequencing. A clear pollution gradient was observed for azithromycin and roxithromycin, with the concentrations in the dry season surpassing those in other seasons. The highest concentration was observed for azithromycin (1.36 μg/L). The abundance of MLS resistance genes increased along the Zao River during the dry season, whereas the opposite trend was obtained during the wet season. A significant correlation between the levels of MLS resistance genes and macrolide antibiotics was identified during the dry season. Notably, compared with the reference site, the abundance of transposase in the effluent from wastewater treatment plants (WWTPs) was significantly elevated in both dry and wet seasons, whereas the abundance of insertion sequences (IS) and plasmids declined during the dry season. The exposure to wastewater containing macrolide antibiotics altered the diversity of planktonic bacterial communities. The bacterial host for ARGs appeared to be Pseudomonas, primarily associated with multidrug subtypes. Moreover, the ARG subtypes were highly correlated with MGEs (transposase and istA). The partial least-squares path model (PLS-PM) demonstrated a positive correlation between the abundance of MGEs and ARGs, indicating the significance of horizontal gene transfer (HGT) in the dissemination of ARGs within the Zao River. Environmental variables, such as TN and NO3--N, were significantly correlated with the abundance of MGEs, ARGs, and bacteria. Collectively, our findings could provide insights into the shift patterns of the microbiome and ARGs across the contamination gradient of AZI and ROX in the river.

Non-thermal obliteration of critically ranked carbapenem-resistant Acinetobacter baumannii and its resistance gene in a batch atmospheric plasma reactor

Wastewater treatment plants (WWTPs) have been implicated as direct key reservoir of both antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) associated with human infection, as high concentrations of ARBs and ARGs have been detected in recycled hospital wastewater. Among the ARBs, the carbapenem-resistant Acinetobacter baumannii has been ranked as priority 1 (critical) pathogen by the World Health Organization (WHO), due to its overwhelming burden on public health. Therefore, this study is aimed at investigating non-thermal plasma (NTP) technology as an alternative disinfection step to inactivate this bacterium and its ARGs. Culture-based method and PCR were employed in confirming the carbapenem resistance gene blaNDM-1 in A. baumannii (BAA 1605). Suspension of carbapenem-resistant A. baumannii (24 h culture) was prepared from the confirmed isolate and subjected to plasma treatment at varying time intervals (3 min, 6 min, 9 min, 12 min, and 15 min) in triplicates. The plasma-treated samples were evaluated for re-growth and the presence of the resistance gene. The treatment resulted in a 1.13 log reduction after 3 min and the highest log reduction of ≥ 8 after 15 min, and the results also showed that NTP was able to inactivate the blaNDM-1 gene. The log reduction and gel image results suggest that plasma disinfection has a great potential to be an efficient tertiary treatment step for WWTPs.

On-Site Inactivation for Disinfection of Antibiotic-Resistant Bacteria in Hospital Effluent by UV and UV-LED

The problem of antimicrobial resistance (AMR) is not limited to the medical field but is also becoming prevalent on a global scale in the environmental field. Environmental water pollution caused by the discharge of wastewater into aquatic environments has caused concern in the context of the sustainable development of modern society. However, there have been few studies focused on the treatment of hospital wastewater, and the potential consequences of this remain unknown. This study evaluated the efficacy of the inactivation of antimicrobial-resistant bacteria (AMRB) and antimicrobial resistance genes (AMRGs) in model wastewater treatment plant (WWTP) wastewater and hospital effluent based on direct ultraviolet (UV) light irradiation provided by a conventional mercury lamp with a peak wavelength of 254 nm and an ultraviolet light-emitting diode (UV-LED) with a peak emission of 280 nm under test conditions in which the irradiance of both was adjusted to the same intensity. The overall results indicated that both UV- and UV-LED-mediated disinfection effectively inactivated the AMRB in both wastewater types (>99.9% after 1-3 min of UV and 3 min of UV-LED treatment). Additionally, AMRGs were also removed (0.2-1.4 log10 for UV 254 nm and 0.1-1.3 log10 for UV 280 nm), and notably, there was no statistically significant decrease (p < 0.05) in the AMRGs between the UV and UV-LED treatments. The results of this study highlight the importance of utilizing a local inactivation treatment directly for wastewater generated by a hospital prior to its flow into a WWTP as sewage. Although additional disinfection treatment at the WWTP is likely necessary to remove the entire quantity of AMRB and AMRGs, the present study contributes to a significant reduction in the loads of WWTP and urgent prevention of the spread of infectious diseases, thus alleviating the potential threat to the environment and human health risks associated with AMR problems.

Metagenomic approach revealed the mobility and co-occurrence of antibiotic resistomes between non-intensive aquaculture environment and human

BACKGROUND

Aquaculture is an important food source worldwide. The extensive use of antibiotics in intensive large-scale farms has resulted in resistance development. Non-intensive aquaculture is another aquatic feeding model that is conducive to ecological protection and closely related to the natural environment. However, the transmission of resistomes in non-intensive aquaculture has not been well characterized. Moreover, the influence of aquaculture resistomes on human health needs to be further understood. Here, metagenomic approach was employed to identify the mobility of aquaculture resistomes and estimate the potential risks to human health.

RESULTS

The results demonstrated that antibiotic resistance genes (ARGs) were widely present in non-intensive aquaculture systems and the multidrug type was most abundant accounting for 34%. ARGs of non-intensive aquaculture environments were mainly shaped by microbial communities accounting for 51%. Seventy-seven genera and 36 mobile genetic elements (MGEs) were significantly associated with 23 ARG types (p < 0.05) according to network analysis. Six ARGs were defined as core ARGs (top 3% most abundant with occurrence frequency > 80%) which occupied 40% of ARG abundance in fish gut samples. Seventy-one ARG-carrying contigs were identified and 75% of them carried MGEs simultaneously. The qacEdelta1 and sul1 formed a stable combination and were detected simultaneously in aquaculture environments and humans. Additionally, 475 high-quality metagenomic-assembled genomes (MAGs) were recovered and 81 MAGs carried ARGs. The multidrug and bacitracin resistance genes were the most abundant ARG types carried by MAGs. Strikingly, Fusobacterium_A (opportunistic human pathogen) carrying ARGs and MGEs were identified in both the aquaculture system and human guts, which indicated the potential risks of ARG transfer.

CONCLUSIONS

The mobility and pathogenicity of aquaculture resistomes were explored by a metagenomic approach. Given the observed co-occurrence of resistomes between the aquaculture environment and human, more stringent regulation of resistomes in non-intensive aquaculture systems may be required. Video Abstract.

Airborne ARGs/MGEs from two sewage types during the COVID-21: Population, microbe interactions, cytotoxicity, formation mechanism, and dispersion

During the COVID-2021 epidemic, a large number of antibiotics were used for clinical treatment in hospitals or daily prevention. Sewage from hospital sewage treatment centers (HSTC) and wastewater treatment plants (WWTP) produced a lot of antibiotic-resistance genes/mobile genetic elements (ARGs/MGEs). In this study, the sewage and bioaerosol in the biochemical tank (BT) of an HSTC and a WWTP were sampled throughout the year. The results showed that the average absolute abundance of sewage in BT of WWTP (BTW-W) was higher than sewage in BT of HSTC (BTW-H). Sewage was an important source of microorganisms and ARGs/MGEs in the air of BT. Microorganisms and MGEs were the factors affecting the differences in ARGs/MGEs. Cytotoxicity experiment proved that the cytotoxicity changed from Grade III to Grade IV with the increase in drug-resistant Escherichia coli concentration. According to the formation mechanism formula, the average generation rate of ARGs/MGEs in BT of HSTC was lower than that in WWTP. The diffusion range of ARGs/MGEs of HSTC was larger than that of WWTP. According to the above results, this study found that when people were far away from BT, the health risk of HSTC caused by the diffusion of bioaerosol was higher than WWTP; When people were close to BT, the health risk of WWTP was higher than HSTC due to the aeration of BT. This study provided a basis for public protection of ARGs. In the future, the elimination of airborne ARGs and crowd protection can be further studied in detail.

The fate of antibiotic resistance genes in wastewater containing microalgae treated by chlorination, ultra-violet, and Fenton reaction

Antibiotic resistance genes (ARGs) and bacteria (ARBs) in the effluent of wastewater treatment plants (WWTPs) are of utmost importance for the dissemination of ARGs in natural aquatic environments. Therefore, there is an urgent need for effective technologies to eliminate WWTP ARGs/ARBs and mitigate the associated risks posed by the discharged ARG in aquatic environments. To test the effective technology for eliminating ARGs/ARBs, we compared the removal of ARGs and ARBs by three different tertiary treatments, namely ultra-violet (UV) disinfection, chlorination disinfection, and Fenton oxidation. Then, the treated wastewater was co-cultured with Chlorella vulgaris (representative of aquatic biota) to investigate the fate of discharged ARGs into the aquatic environment. The results demonstrated that chlorination (at a chlorine concentration of 15 mg/L) and Fenton (at pH 2.73, with 0.005 mol/L Fe2+ and 0.0025 mol/L H2O2) treatment showed higher efficacy in ARG removal (1.8 - 4.17 logs) than UV treatment (15 min) (1.29 - 3.87 logs). Moreover, chlorine at 15 mg/L and Fenton treatment effectively suppressed ARB regeneration while UV treatment for 15 min could not. Regardless of treatments tested in this study, the input of treated wastewater to the Chlorella system increased the number of ARGs and mobile genetic elements (MGEs), indicating the potential risk of ARG dissemination associated with WWTP discharge. Among the wastewater-Chlorella co-culture systems, chlorination resulted in less of an increase in the number of ARGs and MGEs compared to Fenton and UV treatment. When comparing the wastewater systems to the co-culture systems, it was observed that Chlorella vulgaris reduced the number of ARGs and MGEs in chlorination and UV-treated wastewater; however, Chlorella vulgaris promoted ARG survival in Fenton-treated water, suggesting that aquatic microalgae might act as a barrier to ARG dissemination. Overall, chlorination treatment not only effectively removes ARGs and inhibits ARB regeneration but also shows a lower risk of ARG dissemination. Therefore, chlorination is recommended for practical application in controlling the spread of discharged ARGs from WWTP effluent in natural aquatic environments.

Prevalence of antibiotics, antibiotic resistance genes, and their associations in municipal wastewater treatment plants along the Yangtze River basin, China

The overuse and misuse of antibiotics have resulted in the pollution of antibiotics and antibiotic resistance genes (ARGs) in municipal wastewater treatment plants (WWTPs), posing threats to ecological security and human health. Thus, a comprehensive investigation was conducted to assess the occurrence, removal efficiency, and ecological risk of antibiotics, along with the diversity, abundance, and co-occurrence of ARGs, and their correlations in 13 WWTPs along the Yangtze River Basin. Among 35 target antibiotics, 23 antibiotics within 6 categories were detected in all the samples. Amoxicillin (AMO), ofloxacin (OFL), and pefloxacin (PEF) were predominant in influents, while AMO exhibited dominance with the highest concentration of 1409 ng/L in effluents. Although antibiotic removal performance varied among different WWTPs, a significant decrease in each antibiotic category and overall antibiotics was observed in effluents compared with that in influents (p < 0.05). Remarkably, ecological risk assessment revealed high risks associated with AMO and ciprofloxacin (CIP) and medium risks linked to several antibiotics, notably including OFL, roxithromycin (ROX), clarithromycin (CLA), and tetracycline (TC). Furthermore, 96 ARG subtypes within 12 resistance types were detected in this study, and the total absolute abundance and diversity of ARGs were significantly decreased from influents to effluents (p < 0.05). Enrichment of 38 ARGs (e.g., blaNDM, ermA, vatA, mexA, and dfrA25) in effluents indicated potential health risks. Various mobile genetic elements (MGEs), exhibited significant correlations with a majority of ARGs in both influents and effluents, such as intⅠ1, tnpA1, tnpA5, and tp614, underscoring the important role of MGEs in contributing to the ARG dissemination. Many antibiotics displayed lower correlations with corresponding ARGs, but exhibited higher correlations with other ARGs, suggesting complex selective pressures influencing ARG propagation. Overall, the incomplete elimination of antibiotics and ARGs in WWTPs is likely to pose adverse impacts on aquatic ecosystems in the Yangtze River Basin.

Assessing the impact of low organic loading on effluent safety in wastewater treatment: Insights from an activated sludge reactor study

In this study, an organic loading (OL) of 300 mg/(L d) was set as the relative normal condition (OL-300), while 150 mg/(L d) was chosen as the condition reflecting excessively low organic loading (OL-150) to thoroughly assess the associated risks in the effluent of the biological wastewater treatment process. Compared with OL-300, OL-150 did not lead to a significant decrease in dissolved organic carbon (DOC) concentration, but it did improve dissolved organic nitrogen (DON) levels by ∼63 %. Interestingly, the dissolved organic matter (DOM) exhibited higher susceptibility to transformation into chlorinated disinfection by-products (Cl-DBPs) in OL-150, resulting in an increase in the compound number of Cl-DBPs by ∼16 %. Additionally, OL-150 induced nutrient stress, which promoted engendered human bacterial pathogens (HBPs) survival by ∼32 % and led to ∼51 % increase in the antibiotic resistance genes (ARGs) abundance through horizontal gene transfer (HGT). These findings highlight the importance of carefully considering the potential risks associated with low organic loading strategies in wastewater treatment processes.

Horizontal transfer potential of antibiotic resistance genes in wastewater treatment plants unraveled by microfluidic-based mini-metagenomics

Wastewater treatment plants (WWTPs) are known to harbor antibiotic resistance genes (ARGs), which can potentially spread to the environment and human populations. However, the extent and mechanisms of ARG transfer in WWTPs are not well understood due to the high microbial diversity and limitations of molecular techniques. In this study, we used a microfluidic-based mini-metagenomics approach to investigate the transfer potential and mechanisms of ARGs in activated sludge from WWTPs. Our results show that while diverse ARGs are present in activated sludge, only a few highly similar ARGs are observed across different taxa, indicating limited transfer potential. We identified two ARGs, ermF and tla-1, which occur in a variety of bacterial taxa and may have high transfer potential facilitated by mobile genetic elements. Interestingly, genes that are highly similar to the sequences of these two ARGs, as identified in this study, display varying patterns of abundance across geographic regions. Genes similar to ermF found are widely found in Asia and the Americas, while genes resembling tla-1 are primarily detected in Asia. Genes similar to both genes are barely detected in European WWTPs. These findings shed light on the limited horizontal transfer potential of ARGs in WWTPs and highlight the importance of monitoring specific ARGs in different regions to mitigate the spread of antibiotic resistance.

Wastewater surveillance for antibiotics and resistance genes in a river catchment: Spatiotemporal variations and the main drivers

Wastewater-based epidemiology (WBE) is used for mining information about public health such as antibiotics resistance. This study investigated the distribution profiles of six types of antibiotic resistance genes (ARGs) in wastewater and rivers in Wuhu City, China. The levels of ARGs found in the Qingyijiang River were significantly higher than other rivers, and were comparable to effluent levels. Among the ARGs, sulfonamides ARGs and intI1 were the predominant in both wastewaters and rivers. Additionally, the concentrations of ARGs were higher on weekends as opposed to weekdays. Their distribution patterns remained consistent inter-week and inter-season using linear regression analysis (p < 0.001). Interestingly, the occurrence levels of ARGs in wastewaters during spring were significantly higher than in autumn, although insignificant in rivers. The apparent removal rate of ARGs in domestic wastewater sources ranged from 61.52-99.29%, except for qepA (-1.91% to 81.09%), whereas the removal rates in mixed domestic and industrial wastewaters showed a marked decrease (-92.94% to 76.67%). A correlation network analysis revealed that azithromycin and erythromycin were key antibiotics, while blaNDM-1, tetM, tetB, and ermB were identified as key ARGs. Sulfonamide and fluoroquinolone antibiotics, and tetracycline and macrolide ARGs were the primary contributors. Linear mixed models demonstrated that socio-economic variables positively impacted the occurrence levels of ARGs, whereas wastewater flow and river runoff were the negative drivers for their concentrations in wastewaters and surface waters, respectively. Overall, this WBE study contributes to the understanding of spatiotemporal profiles and main drivers of the occurrence of ARGs in wastewater and receiving water.

Antibiotic resistance genes associated with size-segregated bioaerosols from wastewater treatment plants: A review

The antibiotic-resistant pollution in size-segregated bioaerosols from wastewater treatment plants (WWTPs) is of increasing concern due to its public health risks, but an elaborate review is still lacking. This work overviewed the profile, mobility, pathogenic hosts, source, and risks of antibiotic resistance genes (ARGs) in size-segregated bioaerosols from WWTPs. The dominant ARG type in size-segregated bioaerosols from WWTPs was multidrug resistance genes. Treatment units that equipped with mechanical facilities and aeration devices, such as grilles, grit chambers, biochemical reaction tanks, and sludge treatment units, were the primary sources of bioaerosol antibiotic resistome in WWTPs. Higher enrichment of antibiotic resistome in particulate matter with an aerodynamic diameter of <2.5 μm, was found along the upwind-downwind-WWTPs gradient. Only a small portion of ARGs in inhalable bioaerosols from WWTPs were flanked by mobile genetic elements. The pathogens with multiple drug resistance had been found in size-segregated bioaerosols from WWTPs. Different ARGs or antibiotic resistant bacteria have different aerosolization potential associated with bioaerosols from various treatment processes. The validation of pathogenic antibiotic resistance bacteria, deeper investigation of ARG mobility, emission mechanism of antibiotic resistome, and development of treatment technologies, should be systematically considered in future.

Multidrug-resistant plasmid RP4 inhibits the nitrogen removal capacity of ammonia-oxidizing archaea, ammonia-oxidizing bacteria, and comammox in activated sludge

In wastewater treatment plants (WWTPs), ammonia oxidation is primarily carried out by three types of ammonia oxidation microorganisms (AOMs): ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and comammox (CMX). Antibiotic resistance genes (ARGs), which pose an important public health concern, have been identified at every stage of wastewater treatment. However, few studies have focused on the impact of ARGs on ammonia removal performance. Therefore, our study sought to investigate the effect of the representative multidrug-resistant plasmid RP4 on the functional microorganisms involved in ammonia oxidation. Using an inhibitor-based method, we first evaluated the contributions of AOA, AOB, and CMX to ammonia oxidation in activated sludge, which were determined to be 13.7%, 41.1%, and 39.1%, respectively. The inhibitory effects of C2H2, C8H14, and 3,4-dimethylpyrazole phosphate (DMPP) were then validated by qPCR. After adding donor strains to the sludge, fluorescence in situ hybridization (FISH) imaging analysis demonstrated the co-localization of RP4 plasmids and all three AOMs, thus confirming the horizontal gene transfer (HGT) of the RP4 plasmid among these microorganisms. Significant inhibitory effects of the RP4 plasmid on the ammonia nitrogen consumption of AOA, AOB, and CMX were also observed, with inhibition rates of 39.7%, 36.2%, and 49.7%, respectively. Moreover, amoA expression in AOB and CMX was variably inhibited by the RP4 plasmid, whereas AOA amoA expression was not inhibited. These results demonstrate the adverse environmental effects of the RP4 plasmid and provide indirect evidence supporting plasmid-mediated conjugation transfer from bacteria to archaea.

Inactivation of antibiotic-resistant bacteria in hospital wastewater by ozone-based advanced water treatment processes

The emergence and spread of antimicrobial resistance (AMR) continue on a global scale. The impacts of wastewater on the environment and human health have been identified, and understanding the environmental impacts of hospital wastewater and exploring appropriate forms of treatment are major societal challenges. In the present research, we evaluated the efficacy of ozone (O3)-based advanced wastewater treatment systems (O3, O3/H2O2, O3/UV, and O3/UV/H2O2) for the treatment of antimicrobials, antimicrobial-resistant bacteria (AMRB), and antimicrobial resistance genes (AMRGs) in wastewater from medical facilities. Our results indicated that the O3-based advanced wastewater treatment inactivated multiple antimicrobials (>99.9%) and AMRB after 10-30 min of treatment. Additionally, AMRGs were effectively removed (1.4-6.6 log10) during hospital wastewater treatment. The inactivation and/or removal performances of these pollutants through the O3/UV and O3/UV/H2O2 treatments were significantly (P < 0.05) better than those in the O3 and O3/H2O2 treatments. Altered taxonomic diversity of microorganisms based on 16S rRNA gene sequencing following the O3-based treatment showed that advanced wastewater treatments not only removed viable bacteria but also removed genes constituting microorganisms in the wastewater. Consequently, the objective of this study was to apply advanced wastewater treatments to treat wastewater, mitigate environmental pollution, and alleviate potential threats to environmental and human health associated with AMR. Our findings will contribute to enhancing the effectiveness of advanced wastewater treatment systems through on-site application, not only in wastewater treatment plants (WWTPs) but also in medical facilities. Moreover, our results will help reduce the discharge of AMRB and AMRGs into rivers and maintain the safety of aquatic environments.

Significant Differences in the Effects of Nitrogen Doping on Pristine Biochar and Graphene-like Biochar for the Adsorption of Tetracycline

To improve the adsorption efficiency of pollutants by biochar, preparing graphene-like biochar (GBC) or nitrogen-doped biochar are two commonly used methods. However, the difference in the nitrogen doping (N-doping) effects upon the adsorption of pollutants by pristine biochar (PBC) and GBC, as well as the underlying mechanisms, are still unclear. Take the tetracycline (TC) as an example, the present study analyzed the characteristics of the adsorption of TCs on biochars (PBC, GBC, N-PBC, N-GBC), and significant differences in the effects of N-doping on the adsorption of TCs by PBC and GBC were consistently observed at different solution properties. Specifically, N-doping had varied effects on the adsorption performance of PBC, whereas it uniformly improved the adsorption performance of GBC. To interpret the phenomenon, the N-doping upon the adsorption was revealed by the QSAR model, which indicated that the pore filling (VM) and the interactions between TCs with biochars (Ead-v) were found to be the most important two factors. Furthermore, the density functional theory (DFT) results demonstrated that N-doping slightly affects biochar's chemical reactivity. The van der Waals (vdWs) and electrostatic interactions are the main forces for TCs-biochars interactions. Moreover, N-doping mostly strengthened the electrostatic interactions of TCs-biochars, but the vdWs interactions of most samples remained largely unaffected. Overall, the revealed mechanism of N-doping on TCs adsorption by biochars will enhance our knowledge of antibiotic pollution remediation.

Characterization of urban sources of antibiotics and antibiotic-resistance genes in a Dutch sewer catchment

A one year study was conducted in the city of Nijmegen, The Netherlands, to characterize various urban sources of antibiotics and antibiotic resistant genes (ARGs) in wastewater within a single sewer catchment. Prevalence of ermB, tet(W), sul1, sul2, intl1, and 16S rRNA gene was determined at 10 locations within the city. Sampling locations included a nursing home, a student residence, a hospital and an industrial area, among others. Wastewater concentrations of 23 antibiotics were measured using passive sampling. Additionally, excreted loads of 22 antibiotics were estimated based on ambulatory prescription and clinical usage data. Genes sul1 and intl1 were most abundant across most locations. Ciprofloxacin and amoxicillin together contributed over 92 % of the total estimated antibiotic selective pressure at all sampling points. The present study highlights the prominent role that hospitals can have in the prevalence and proliferation of ARGs in urban wastewater. Furthermore, results suggest that even short-term changes in the therapeutic regimen prescribed in hospitals may translate into shifting ARG abundance patterns in hospital wastewater. The methods applied present an opportunity to identify emission hotspots and prioritize intervention options to limit ARG spread from urban wastewater to the environment.

Metabolite Cross-Feeding Promoting NADH Production and Electron Transfer during Efficient SMX Biodegradation by a Denitrifier and S. oneidensis MR-1 in the Presence of Nitrate

Antibiotics often coexist with other pollutants (e.g., nitrate) in an aquatic environment, and their simultaneous biological removal has attracted widespread interest. We have found that sulfamethoxazole (SMX) and nitrate can be efficiently removed by the coculture of a model denitrifier (Paracoccus denitrificans, Pd) and Shewanella oneidensis MR-1 (So), and SMX degradation is affected by NADH production and electron transfer. In this paper, the mechanism of a coculture promoting NADH production and electron transfer was investigated by proteomic analysis and intermediate experiments. The results showed that glutamine and lactate produced by Pd were captured by So to synthesize thiamine and heme, and the released thiamine was taken up by Pd as a cofactor of pyruvate and ketoglutarate dehydrogenase, which were related to NADH generation. Additionally, Pd acquired heme, which facilitated electron transfer as heme, was the important composition of complex III and cytochrome c and the iron source of iron sulfur clusters, the key component of complex I in the electron transfer chain. Further investigation revealed that lactate and glutamine generated by Pd prompted So chemotactic moving toward Pd, which helped the two bacteria effectively obtain their required substances. Obviously, metabolite cross-feeding promoted NADH production and electron transfer, resulting in efficient SMX biodegradation by Pd and So in the presence of nitrate. Its feasibility was finally verified by the coculture of an activated sludge denitrifier and So.

The factors controlling antibiotic resistance genes in different treatment processes of mainstream full-scale wastewater treatment plants

The alteration of antibiotic resistance genes (ARGs) in wastewater has been less studied in wastewater treatment plants (WWTPs), making it difficult to assess ARGs' spreading risk comprehensively. Therefore, this study investigated the distribution and reduction of ARGs in the main process (Anaerobic-Anoxic-Oxic with Membrane Bio-Reactor (A2/O + MBR), Oxidation Ditch with sedimentation (OD), and Cyclic Activated Sludge System (CASS) with sedimentation) and disinfection process (Ultra-violet and Chlorination) of full-scale WWTPs. The wastewater was sampled before and after the different main process and disinfection process; then, the diversity and abundance of ARGs and mobile genetic genes (MGEs, helping the horizontal transfer of ARGs) in wastewater of different treatment stages were determined by a real-time high-throughput quantitative PCR (HT-qPCR) system. It was found that similar influents would result in similar ARGs in wastewater samples, independent of the treatment processes used. The main process could effectively reduce the abundance of ARGs and MGEs by 1.80-2.12 and 1.46-2.18 logarithm units, respectively. The main factors affecting ARGs were mainly wastewater quality index, especially COD, and MGEs like transposase and insertion sequences which were significantly associated with 66 and 48 subtypes of ARGs, respectively. Moreover, disinfection was more effective than the main process in inactivating antibiotic resistance bacteria (ARB), and the removal rate of ARB by disinfection reached 43.53 %-100 %. However, there are still risks of ARB regeneration (up to 4.22 log units) in the effluent of WWTPs. In the future, nutrient removal and disinfection process improvement is necessary to benefit ARG and ARB removal.

Spatial and temporal distribution of endotoxins, antibiotic resistance genes and mobile genetic elements in the air of a dairy farm in Germany

Antimicrobial resistance (AMR) is a serious issue that is continuously growing and spreading, leading to a dwindling number of effective treatments for infections that were easily treatable with antibiotics in the past. Animal farms are a major hotspot for AMR, where antimicrobials are often overused, misused, and abused, in addition to overcrowding of animals. In this study, we investigated the risk of AMR transmission from a farm to nearby residential areas by examining the overall occurrence of endotoxins, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) in the air of a cattle farm. We assessed various factors, including the season and year, day and nighttime, and different locations within the farm building and its vicinity. The most abundant ARGs detected were tetW, aadA1, and sul2, genes that encode for resistances towards antibiotics commonly used in veterinary medicine. While there was a clear concentration gradient for endotoxin from the middle of the farm building to the outside areas, the abundance of ARGs and MGEs was relatively uniform among all locations within the farm and its vicinity. This suggests that endotoxins preferentially accumulated in the coarse particle fraction, which deposited quickly, as opposed to the ARGs and MGEs, which might concentrate in the fine particle fraction and remain longer in the aerosol phase. The occurrence of the same genes found in the air samples and in the manure indicated that ARGs and MGEs in the air mostly originated from the cows, continuously being released from the manure to the air. Although our atmospheric dispersion model indicated a relatively low risk for nearby residential areas, farm workers might be at greater risk of getting infected with resistant bacteria and experiencing overall respiratory tract issues due to continuous exposure to elevated concentrations of endotoxins, ARGs and MGEs in the air of the farm.

Tracking spatio-temporal distribution and transmission of antibiotic resistance in aquatic environments by using ESBL-producing Escherichia coli as an indicator

Wastewater treatment plants (WWTPs) play an important role in the production, and transmission of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) as a convergence for human, animal, and environmental wastewater. The aim of this study was to investigate the spatio-temporal variation and influencing factors of ARB in different functional areas of the urban WWTP and the connecting rivers for 1-year monitoring using extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) as an indicator bacteria, and to study the transmission patterns of ARB in the aquatic environment. The results showed that ESBL-Ec isolates were identified from the WWTP (n = 219), including influent (n = 53), anaerobiotic tank (n = 40), aerobiotic tank (n = 36), activated sludge tank (n = 31), sludge thickner tank (n = 30), effluent (n = 16), and mudcake storage area (n = 13). The dehydration process can significantly remove the ESBL-Ec isolates; however, ESBL-Ec was still detected in samples collected from the effluent of the WWTP (37.0%). The detection rate of ESBL-Ec was significantly different across seasons (P < 0.05), and ambient temperature was negatively correlated with the detection rate of ESBL-Ec (P < 0.05). Furthermore, a high prevalence of ESBL-Ec isolates (29/187, 15.5%) was detected in samples collected from the river system. These findings emphasize that the high majority of ESBL-Ec in aquatic environments is alarming because it poses a significant threat to public health. Clonal transmission of ESBL-Ec isolates between the WWTP and rivers based on the spatio-temporal scale was observed by pulsed-field gel electrophoresis analysis, ST38 and ST69 ESBL-Ec clone were selected as prioritized isolates for antibiotic resistance monitoring in the aquatic environment. Further phylogenetic analysis showed human-associated (feces, blood) E. coli was the main source contributing to the presence of antibiotic resistance in aquatic environments. Longitudinal and targeted monitoring of ESBL-Ec in WWTPs and the development of effective wastewater disinfection strategies before effluent discharge from WWTPs are urgently required, to prevent and control the spread of antibiotic resistance in the environment.

Long-term impacts of conservation pasture management in manuresheds on system-level microbiome and antibiotic resistance genes

Animal manure improves soil fertility and organic carbon, but long-term deposition may contribute to antibiotic resistance genes (ARGs) entering the soil-water environment. Additionally, long-term impacts of applying animal manure to soil on the soil-water microbiome, a crucial factor in soil health and fertility, are not well understood. The aim of this study is to assess: (1) impacts of long-term conservation practices on the distribution of ARGs and microbial dynamics in soil, and runoff; and (2) associations between bacterial taxa, heavy metals, soil health indicators, and ARGs in manures, soils, and surface runoff in a study following 15 years of continuous management. This management strategy consists of two conventional and three conservation systems, all receiving annual poultry litter. High throughput sequencing of the 16S ribosomal RNA was carried out on samples of cattle manure, poultry litter, soil, and runoff collected from each manureshed. In addition, four representative ARGs (intl1, sul1, ermB, and blactx-m-32) were quantified from manures, soil, and runoff using quantitative PCR. Results revealed that conventional practice increased soil ARGs, and microbial diversity compared to conservation systems. Further, ARGs were strongly correlated with each other in cattle manure and soil, but not in runoff. After 15-years of conservation practices, relationships existed between heavy metals and ARGs. In the soil, Cu, Fe and Mn were positively linked to intl1, sul1, and ermB, but trends varied in runoff. These findings were further supported by network analyses that indicated complex co-occurrence patterns between bacteria taxa, ARGs, and physicochemical parameters. Overall, this study provides system-level linkages of microbial communities, ARGs, and physicochemical conditions based on long-term conservation practices at the soil-water-animal nexus.

Chlorine oxide radical (ClO) enables the enhanced degradation of antibiotic resistance genes during UV/chlorine treatment by selectively inducing base damage

Compared to individual UV or chlorine disinfection, the combined UV and chlorine (i.e., UV/chlorine) can substantially promote the degradation of antibiotic resistance genes (ARGs) in the effluent by generating radicals. However, the mechanisms of ARG degradation induced by radicals during UV/chlorine treatment remain largely unknown, limiting further enhancement of ARG degradation by process optimization. Herein, we aimed to uncover the role of different radicals in ARG degradation and the molecular mechanisms of ARG degradation by radicals in UV/chlorine process. The ClO was proven to be responsible for the enhanced ARG degradation during UV/chlorine treatment, while the other radicals (OH, Cl, and Cl2-) played a minor role. This is because ClO possessed both high steady-state concentration and high reactivity toward ARGs (rate constant: 4.29 × 1010 M-1 s-1). The ClO might collaborate with free chlorine to degrade ARG. The ClO degraded ARGs by selectively attacking guanine and thymine but failed to induce strand breakage, while chlorine could break the strand of ARGs. Ultimately, ClO cooperated with chlorine to degrade ARGs quickly by hydroxylation and chlorination of bases and produce many chlorine- and nitrogen-containing products as revealed by high-resolution mass spectrometry. The uncovered degradation mechanisms of ARGs by UV/chlorine provide useful guidelines for process optimization to achieve deep removal of effluent ARGs.

Characteristics of bacterial community and ARG profiles in the surface and air environments in a spacecraft assembly cleanroom

Understanding the microbial communities and antibiotic resistance genes (ARGs) in spacecraft assembly cleanrooms is crucial for spacecraft microbial control and astronaut safety. However, there have been few reports of ARG profiles and their relationship with microbiomes in such environments. In the present study, we assessed the bacterial community and ARGs in the air dust and surface environments of a typical spacecraft assembly cleanroom. Our results show a significant difference in bacterial composition between surfaces and air dust, as they belong to two distinct ecostates. Bacillus and Acinetobacter were significantly enriched in the air samples. Bacterial community network analysis revealed lower topological parameters and robustness of bacterial networks in the air samples. We also observed different distribution patterns of some typical ARGs between surface and air dust samples. Notably, the ermB gene exhibited a relatively high copy number and was enriched in the surface environment, compared to that in the air. Overall, our study provides insight into the complex microbial community and the distribution and transfer of ARGs in spacecraft assembly cleanrooms, and offers important input for developing control strategies against ARGs.

Hospitals and households as primary emission sources for risk-posing pharmaceuticals in municipal wastewater

A wide range of pharmaceutical residues is known to occur in the environment. While they are released into surface waters mainly through centralized wastewater treatment plants (WWTPs), their primary emission sources are located upstream in the sewer network. Information on emissions from different types of primary emission sources is scarce. However, such information could help direct emission reduction measures more efficiently. In this study, we analysed the concentrations of selected active pharmaceutical ingredients (APIs) in wastewater samples taken from altogether ten sites, covering primary emission sources (hospitals and households), and conventional WWTPs. The concentrations in WWTP effluents were used to identify APIs causing risk in recipient waterbodies. Furthermore, the API loads from households and hospitals were compared to those reaching the WWTP in mixed influents. Our results confirm previously published observations of several pharmaceuticals exceeding their predicted no-effect concentrations in effluent wastewaters. Moreover, the concentrations of most of the analysed APIs are comparatively high in hospital wastewaters, resulting in elevated risk quotients. While the total API loads are relatively low from primary emission sources, owing to the low wastewater volume generated at those sites, per capita emissions were shown to be several times higher at hospital sites than at household sites for APIs such as metronidazole, trimethoprim, and ofloxacin. These findings indicate, that directing emission reduction measures to hospitals could be an effective way to decrease the loads of several risk-posing APIs into the environment, especially where hospital contribution to overall wastewater flow to WWTPs is high.

Effects of tidal action on the stability of microbiota, antibiotic resistance genes, and microplastics in the Pearl River Estuary, Guangzhou, China

In this study, the 16S rRNA gene amplicon sequencing technique was used to explore the microbial diversity and differences in the water environment of the Pearl River Estuary in Nansha District with various land use types such as the aquaculture area, industrial area, tourist area, agricultural plantation, and residential area. At the same time, the quantity, type, abundance, and distribution of two types of emerging environmental pollutants, antibiotic resistance genes (ARGs) and microplastics (MPs), are explored in the water samples from different functional areas. The results show that the dominant phyla in the five functional regions are Proteobacteria, Actinobacteria and Bacteroidetes, and the dominant genera are Hydrogenophaga, Synechococcus, Limnohabitans and Polynucleobacter. A total of 248 ARG subtypes were detected in the five regions, belonging to nine classes of ARGs (Aminoglycoside, Beta_Lactamase, Chlor, MGEs, MLSB, Multidrug, Sul, Tet, Van). Blue and white were the dominant MP colors in the five regions; 0.5-2 mm was the dominant MP size, and cellulose, rayon, and polyester comprised the highest proportion of the plastic polymers. This study provides the basis for understanding the environmental microbial distribution in estuaries and the prevention of environmental health risks from ARGs and microplastics.

Performance of a Pilot-Scale Continuous Flow Ozone-Based Hospital Wastewater Treatment System

Antimicrobial resistance (AMR) is becoming a global concern. Recently, research has emerged to evaluate the human and environmental health implications of wastewater from medical facilities and to identify acceptable wastewater treatment methods. In this study, a disinfection wastewater treatment system using an ozone-based continuous flow system was installed in a general hospital located in Japan. The effectiveness of antimicrobial-resistant bacteria (ARB) and antimicrobials in mitigating the environmental impact of hospital wastewater was evaluated. Metagenomic analysis was conducted to characterize the microorganisms in the wastewater before and after treatment. The results demonstrated that ozone treatment enables effective inactivation of general gut bacteria, including Bacteroides, Prevotella, Escherichia coli, Klebsiella, DNA molecules, and ARGs, as well as antimicrobials. Azithromycin and doxycycline removal rates were >99% immediately after treatment, and levofloxacin and vancomycin removal rates remained between 90% and 97% for approximately one month. Clarithromycin was more readily removed than the other antimicrobials (81-91%), and no clear removal trend was observed for ampicillin. Our findings provide a better understanding of the environmental management of hospital wastewater and enhance the effectiveness of disinfection wastewater treatment systems at medical facilities for mitigating the discharge of pollutants into aquatic environments.

Dual-channel fluorescence detection of antibiotic resistance genes based on DNA-templated silver nanoclusters

The aqueous environment is an ideal site for the generation and transmission of antibiotic resistance genes (ARGs), and has become a sink for multiple ARGs. Detection of multiple ARGs in one-pot by a simple method is essential to control the spread of antibiotic resistance. Herein, we developed a novel fluorescence sensing strategy based on chameleon DNA-templated silver nanoclusters (AgNCs) to achieve simultaneous detection of two ARGs (tet-A and sul-1). A DNA fluorescent probe with AgNCs stabilized at both termini and another DNA probe carried enhancer sequences were designed. The hybridization of the target ARGs and probes can form an infinitely extended linear DNA structure containing multi-branched AgNCs beacons, and the chameleon AgNCs approach the fluorescence enhancer sequence, thereby realizing the transduction and amplification of green and red fluorescence signals. Through this strategy, we successfully achieved highly specific detection of two ARGs with the LOD of 0.45 nM for tet-A and 0.32 nM for sul-1. In addition, the strategy still had good applicability in the detection of actual samples containing complex components. In this study, fluorescent DNA-AgNCs were applied to the rapid, enzyme-free and reliable detection of ARGs for the first time. The excellent performance of the simultaneous detection of two ARGs displayed that this method can be used to simultaneously analyze different types of ARGs, indicating its great potential in rapid screening and quantitative detection of ARGs in various environmental medias.

Inactivation of antibiotic-resistant bacteria and antibiotic-resistance genes in wastewater streams: Current challenges and future perspectives

The discovery of antibiotics, which was once regarded as a timely medical intervention now leaves a bitter aftertaste: antimicrobial resistance (AMR), due to the unregulated use of these compounds and the poor management receiving wastewaters before discharge into pristine environments or the recycling of such treated waters. Wastewater treatment plants (WWTPs) have been regarded a central sink for the mostly unmetabolized or partially metabolised antibiotics and is also pivotal to the incidence of antibiotic resistance bacteria (ARBs) and their resistance genes (ARGs), which consistently contribute to the global disease burden and deteriorating prophylaxis. In this regard, we highlighted WWTP-antibiotics consumption-ARBs-ARGs nexus, which might be critical to understanding the epidemiology of AMR and also guide the precise prevention and remediation of such occurrences. We also discovered the unsophistication of conventional WWTPs and treatment techniques for adequate treatment of antibiotics, ARBs and ARGs, due to their lack of compliance with environmental sustainability, then ultimately assessed the prospects of cold atmospheric plasma (CAP). Herein, we observed that CAP technologies not only has the capability to disinfect wastewater polluted with copious amounts of chemicals and biologicals, but also have a potential to augment bioelectricity generation, when integrated into bio electrochemical modules, which future WWTPs should be retrofitted to accommodate. Therefore, further research should be conducted to unveil more of the unknowns, which only a snippet has been highlighted in this study.

Extracellular polymeric substances-antibiotics interaction in activated sludge: A review

Antibiotics, the most frequently prescribed drugs, have been widely applied to prevent or cure human and veterinary diseases and have undoubtedly led to massive releases into sewer networks and wastewater treatment systems, a hotspot where the occurrence and transformation of antibiotic resistance take place. Extracellular polymeric substances (EPS), biopolymers secreted via microbial activity, play an important role in cell adhesion, nutrient retention, and toxicity resistance. However, the potential roles of sludge EPS related to the resistance and removal of antibiotics are still unclear. This work summarizes the composition and physicochemical characteristics of state-of-the-art microbial EPS, highlights the critical role of EPS in antibiotics removal, evaluates their defense performances under different antibiotics exposures, and analyzes the typical factors that could affect the sorption and biotransformation behavior of antibiotics. Next, interactions between microbial EPS and antibiotic resistance genes are analyzed. Future perspectives, especially the engineering application of microbial EPS for antibiotics toxicity detection and defense, are also emphatically stressed.