Antibiotic Resistant Bacteria in Municipal Wastes: Is There Reason for Concern?

New directions on membranes for removal and degradation of emerging pollutants in aqueous systems

Emerging pollutants (EPs) refer to a group of non-regulated chemical or biological substances that have been recently introduced or detected in the environment. These pollutants tend to exhibit resistance to conventional treatment methods and can persist in the environment for prolonged periods, posing potential adverse effects on ecosystems and human health. As we enter a new era of managing these pollutants, membrane-based technologies hold significant promise in mitigating impact of EPs on the environment and safeguarding human health due to their high selectivity, efficiency, cost-effectiveness and capability for simultaneous separation and degradation. Moreover, these technologies continue to evolve rapidly with the development of new membrane materials and functionalities, advanced treatment strategies, and analyses for effectively treating EPs of more recent concerns. The objective of this review is to present the latest directions and advancements in membrane-based technologies for addressing EPs. By highlighting the progress in this field, we aim to share valuable perspectives with researchers and contribute to the development of future directions in sustainable treatments for EPs.

Urban green waste bulking agent is the major source of antimicrobial resistance genes persisted in home compost, not animal manure

Urban green waste and food waste are often used as bulking agents to prepare home compost in combination with animal manure in urban horticulture and community gardening. Although it is known that antimicrobial resistance genes (ARGs) persist in home compost, their origins have not been determined. In addition, the factors contributing to ARGs persistence remain unclear. In this study, we aim to (i) characterize the changes in the microbiome and antimicrobial resistome during the composting process of home compost using metagenomics shotgun sequencing, (ii) identify the source of the ARGs persisted in home compost using SourceTracker, and (iii) elucidate the collective effect of compost microbiome and environmental factors, including the physicochemical properties and antibiotics concentration of home compost, in contributing to ARG persistence using Procrustes analysis, co-occurrence network analysis, variation partitioning analysis, and structural equation modeling. SourceTracker analysis indicated that urban green waste bulking agent was the major source of the persisting ARGs in home compost instead of animal manure. Procrustes analysis and co-occurrence network analysis revealed a strong association between microbiome and antimicrobial resistome. Variation partitioning analysis and structural equation modeling suggested that physicochemical properties shaped the antimicrobial resistome directly and indirectly by influencing the microbiome. Our results indicated that the persistence of ARGs in home compost might be due to the succession of microbial species from the urban green waste bulking agent, and the physicochemical properties might have defined the compost environment to shape the microbiome in the compost, thus, in turn, the persisting antimicrobial resistome.

Solvent-free synthesis of foam board-like CoSe2 alloy to selectively generate singlet oxygen via peroxymonosulfate activation for sulfadiazine degradation

Singlet oxygen (1O2) is a highly effective reactive species in selectively oxidizing organic pollutants. However, it is still challenging to rationally design robust catalysts for the selective generation of 1O2. Herein, the coordination and engineering architecture of the foam board-like CoSe2 alloy were facilely constructed through a green solvent-free method and displayed almost 100% 1O2 production selectivity. The CoSe2 alloy showed excellent catalytic ability for the efficient and fast removal of organic pollutants via peroxymonosulfate (PMS) activation compared with previously reported cobalt-based catalysts. The CoSe2/PMS system exhibited strong resistance for a broad pH range (3.0-11.0) and various coexisting inorganic ions owing to the advantage of the strong bonding of Co-Se in CoSe2 alloy. Mechanism studies revealed that 1O2 was the only reactive oxygen species in the CoSe2/PMS system. Theoretical calculations demonstrated that Co was the dominant adsorption site for PMS in CoSe2, and the production pathway of 1O2 was PMS* → *OH → *O → 1O2. In addition, it was proved that *OH and *O served as the rate-determining steps for the formation of 1O2 by PMS activation on CoSe2 alloy. These findings provide a rational strategy for preparing a series of low-cost transition metal-based alloy catalysts for PMS activation to achieve high-efficiency 1O2 production in the elimination of organic pollutants.

Impacts of irrigation with treated livestock wastewater on the accumulation characteristic of ARGs in the farmland soil: a case study in Hohhot, China

Irrigation with treated livestock wastewater (TWW) is a promising strategy for reusing resources. However, TWW irrigation might introduce antibiotic resistant genes (ARGs) into the soil, posing environmental risks associated with antibiotic resistance. This study focuses on investigating the influence of irrigation amounts and duration on the fate of ARGs and identifies key factors driving their changes. The results showed that there were 13 ARGs in TWW, while only 5 ARGs were detected in irrigated soil. That is some introduced ARGs from TWW could not persistently exist in the soil. After 1-year irrigation, an increase in irrigation amount from 0.016 t/m2 to 0.048 t/m2 significantly enhanced the abundance of tetC by 29.81%, while ermB and sul2 decreased by 45.37% and 76.47%, respectively (p < 0.01). After 2-year irrigation, the abundance of tetC, ermB, ermF, dfrA1, and total ARGs significantly increased (p < 0.05) when the irrigation amount increased. The abundances of ARGs after 2-year irrigation were found to be 2.5-34.4 times higher than 1 year. Obviously, the irrigation years intensified the positive correlation between ARGs abundance and irrigation amount. TetC and ermF were the dominant genes resulting in the accumulation of ARGs. TWW irrigation increased the content of organic matter and total nitrogen in the soil, which affected microbial community structure. The changes of the potential host were the determining factors driving the ARGs abundance. Our study demonstrated that continuous TWW irrigation for 2 years led to a substantial accumulation of ARGs in soil.

Roles of extracellular polymeric substances in the adsorption and removal of norfloxacin during hydrothermal treatment of sewage sludge

Hydrothermal treatment (HT) is promising to remove antimicrobials from sewage sludge (SS); however, the mechanism of antimicrobial degradation during the HT of SS is not fully understood. In this study, the roles of extracellular polymeric substances (EPS) in the removal and transformation of norfloxacin (NOR) during the HT of SS at temperatures of 100 and 160 °C were investigated. The results indicated that the degradation of NOR increased with increasing HT temperature, with maximum NOR removal (52%) achieved at 160 °C. Furthermore, the NOR in sludge showed higher degradation efficiencies than the control as HT temperature was higher than 120 °C. Evident promotion effects of bound-EPS (B-EPS) in sludge were observed on the NOR degradation as HT temperature was higher than 120 °C, leading to the mineralization and deamination of protein-like components in EPS during HT. Beside, the adsorption capacity of NOR during the HT of SS decreased at temperatures higher than 120 °C. The evolution of the spatial structure of B-EPS was predominantly responsible for the adsorption of antimicrobials, a spontaneous process driven mainly by hydrophilic interactions. With the hydrothermal conversion of B-EPS, the electron transfer, and reactive species (3EPS* and ·OH) derived from B-EPS could facilitate the degradation of NOR. In particular, hydrogen bonds between B-EPS and NOR increased the apparent yield of ·OH and accelerated the decarboxylation of NOR during HT at temperatures higher than 120 °C. A toxicity evaluation suggested that HT for NOR degradation could attenuate toxicity, whereas deep oxidation or mineralization would be needed to promote ecosystem safety. These findings provide new insights into the hydrothermal activation of EPS and the interrelated hydrothermal fate of antimicrobials and other toxic pollutants in sludge.

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.

Water, Water Everywhere, but Every Drop Unique: Challenges in the Science to Understand the Role of Contaminants of Emerging Concern in the Management of Drinking Water Supplies

The protection and management of water resources continues to be challenged by multiple and ongoing factors such as shifts in demographic, social, economic, and public health requirements. Physical limitations placed on access to potable supplies include natural and human-caused factors such as aquifer depletion, aging infrastructure, saltwater intrusion, floods, and drought. These factors, although varying in magnitude, spatial extent, and timing, can exacerbate the potential for contaminants of concern (CECs) to be present in sources of drinking water, infrastructure, premise plumbing and associated tap water. This monograph examines how current and emerging scientific efforts and technologies increase our understanding of the range of CECs and drinking water issues facing current and future populations. It is not intended to be read in one sitting, but is instead a starting point for scientists wanting to learn more about the issues surrounding CECs. This text discusses the topical evolution CECs over time (Section 1), improvements in measuring chemical and microbial CECs, through both analysis of concentration and toxicity (Section 2) and modeling CEC exposure and fate (Section 3), forms of treatment effective at removing chemical and microbial CECs (Section 4), and potential for human health impacts from exposure to CECs (Section 5). The paper concludes with how changes to water quantity, both scarcity and surpluses, could affect water quality (Section 6). Taken together, these sections document the past 25 years of CEC research and the regulatory response to these contaminants, the current work to identify and monitor CECs and mitigate exposure, and the challenges facing the future.

Co single atoms anchored on straw biochar as an efficient peroxydisulfate activator for ultrafast removal of antibiotics

The removal efficiency of antibiotics decreases at low temperature, which is an urgent problem to be solved in cold regions. This study prepared a low-cost single atom catalyst (SAC) from straw biochar, which can rapidly degrade antibiotics at different temperatures by activating peroxydisulfate (PDS). Co SA/CN-900 + PDS system can degrade 100% of tetracycline hydrochloride (TCH, 10 mg/L) in 6 min. The high concentration of TCH (25 mg/L) was degraded by 96.3% in 10 min at 4 °C. The system was also tested in simulated wastewater and showed a good removal efficiency. TCH was primarily degraded by 1O2 and direct electron transfer pathway. Electrochemical experiments and density functional theory (DFT) calculations showed that CoN4 improved the electron transfer capacity of biochar and thus enhanced the oxidation capacity of Co SA/CN-900 + PDS complex. This work optimizes the application of agricultural waste biochar and provides a design strategy of efficient heterogenous Co SACs to degrade antibiotics in cold regions.

Identifying sources of antibiotic resistance genes in the environment using the microbial Find, Inform, and Test framework

Introduction

Antimicrobial resistance (AMR) is an increasing public health concern for humans, animals, and the environment. However, the contributions of spatially distributed sources of AMR in the environment are not well defined.

Methods

To identify the sources of environmental AMR, the novel microbial Find, Inform, and Test (FIT) model was applied to a panel of five antibiotic resistance-associated genes (ARGs), namely, erm(B), tet(W), qnrA, sul1, and intI1, quantified from riverbed sediment and surface water from a mixed-use region.

Results

A one standard deviation increase in the modeled contributions of elevated AMR from bovine sources or land-applied waste sources [land application of biosolids, sludge, and industrial wastewater (i.e., food processing) and domestic (i.e., municipal and septage)] was associated with 34-80% and 33-77% increases in the relative abundances of the ARGs in riverbed sediment and surface water, respectively. Sources influenced environmental AMR at overland distances of up to 13 km.

Discussion

Our study corroborates previous evidence of offsite migration of microbial pollution from bovine sources and newly suggests offsite migration from land-applied waste. With FIT, we estimated the distance-based influence range overland and downstream around sources to model the impact these sources may have on AMR at unsampled sites. This modeling supports targeted monitoring of AMR from sources for future exposure and risk mitigation efforts.

Risk control of antibiotics, antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) during sewage sludge treatment and disposal: A review

Sewage sludge is an important reservoir of antibiotics, antibiotic resistance genes (ARGs), and antibiotic resistant bacteria (ARB) in wastewater treatment plants (WWTPs), and the reclamation of sewage sludge potentially threats human health and environmental safety. Sludge treatment and disposal are expected to control these risks, and this review summarizes the fate and controlling efficiency of antibiotics, ARGs, and ARB in sludge involved in different processes, i.e., disintegration, anaerobic digestion, aerobic composting, drying, pyrolysis, constructed wetland, and land application. Additionally, the analysis and characterization methods of antibiotics, ARGs, and ARB in complicate sludge are reviewed, and the quantitative risk assessment approaches involved in land application are comprehensively discussed. This review benefits process optimization of sludge treatment and disposal, with regard to environmental risks control of antibiotics, ARGs, and ARB in sludge. Furthermore, current research limitations and gaps, e.g., the antibiotic resistance risk assessment in sludge-amended soil, are proposed to advance the future studies.

Periodate activation by pyrite for the disinfection of antibiotic-resistant bacteria: Performance and mechanisms

The propagation of antibiotic-resistant bacteria (ARB) greatly endangers the ecological safety and human health. This study employed pyrite (FeS₂, naturally abundant mineral) for periodate (PI) activation to disinfect ARB. FeS₂/PI system could disinfect 1 × 10⁷ CFU mL^-1 of kanamycin-resistant E.coli below the limit of detection in 20 min. Efficient ARB inactivation performance was achieved in pH from 3 to 9, ionic strength from 0 to 300 mM, with HA (0.1-10 mg L^-1) in suspension, and in real water samples including tap water, river water and sewage. FeS₂/PI system could also efficiently disinfect gentamycin-resistant E.coli and Gram-positive B. subtilis. The generated reactive species including Fe(IV), ·O₂^- and ·OH would attack cell membrane and overwhelmed intracellular defense system. The intracellular kanamycin resistance genes in cells would be released and then degraded in FeS₂/PI system. PI preferred to be adsorbed on Fe site of FeS₂ (with lower adsorption energy, more occupancy of bonding state and stronger bonding strength). The subsequent transfer of electron cloud from Fe site to PI would cleave IO bond to generate reactive species. Moreover, FeS₂/PI system could also combine with sand filtration system to efficiently capture and disinfect ARB. Therefore, FeS₂/PI system is a promising approach to inactivate ARB in different scenarios.

Electroactive Ultrafiltration Membrane for Simultaneous Removal of Antibiotic, Antibiotic Resistant Bacteria, and Antibiotic Resistance Genes from Wastewater Effluent

To combat the spread of antibiotic resistance into the environment, we should adequately manage wastewater effluent treatment to achieve simultaneous removal of antibiotics, antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs). Herein, we fabricate a multifunctional electroactive poly(vinylidene fluoride) ultrafiltration membrane (C/PVDF) by phase inversion on conductive carbon cloth. The membrane possesses not only excellent retention toward ARB and ARGs but also exhibits high oxidation capacity as an electrode. Notably, sulfamethoxazole degradation involving hydroxylation and hydrolysis by the anode membrane is predominant, and the degradation efficiency is up to 81.5% at +4 V. Both electro-filtration processes exhibit significant ARB inactivation, anode filtration is superior to cathode filtration. Moreover, the degradation of intracellular ARGs (iARGs) located in the genome is more efficient than those located in the plasmid, and these degradation efficiencies at -2 V are higher than +2 V. The degradation efficiencies of extracellular ARGs (eARGs) are opposite and are lower than iARGs. Compared with regular filtration, the normalized flux of electroactive ultrafiltration membrane is improved by 18.0% at -2 V, 15.9% at +2 V, and 30.4% at +4 V during treating wastewater effluent, confirming its antifouling properties and feasibility for practical application.

Distribution and characteristics of carbapenem-resistant and extended-spectrum β-lactamase (ESBL) producing Escherichia coli in hospital effluents, sewage treatment plants, and river water in an urban area of Japan

Occurrence of profiles of the carbapenem-resistant Escherichia coli (CRE-E) and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-E) in an urban river in a sub-catchment of the Yodo River Basin, one of the representative water systems of Japan was investigated. We conducted seasonal and year-round surveys for the antimicrobial-resistant bacteria (AMRB) and antimicrobial-resistance genes (AMRGs) in hospital effluents, sewage treatment plant (STP) wastewater, and river water; subsequently, contributions to wastewater discharge into the rivers were estimated by analyses based on the mass flux. Furthermore, the characteristics of AMRB in the water samples were evaluated on the basis of antimicrobial susceptibility tests. CRE-E and ESBL-E were detected in all water samples with mean values 11 and 1900 CFU/mL in the hospital effluent, 58 and 4550 CFU/mL in the STP influent, not detected to 1 CFU/mL in the STP effluent, and 1 and 1 CFU/mL in the STP discharge into the river, respectively. Contributions of the pollution load derived from the STP effluent discharged into the river water were 1 to 21%. The resistome profiles for bla_IMP, bla_TEM, and bla_CTX-M genes in each water sample showed that AMRGs were not completely removed in the wastewater treatment process in the STP, and the relative abundances of bla_IMP, bla_TEM, and bla_CTX-M genes were almost similar (P<0.05). Susceptibility testing of antimicrobial-resistant E. coli isolates showed that CRE-E and ESBL-E detected in wastewaters and river water were linked to the prevalence of AMRB in clinical settings. These results suggest the importance of conducting environmental risk management of AMRB and AMRGs in the river environment. To our knowledge, this is the first detailed study that links the medical environment to CRE-E and ESBL-E for evaluating the AMRB and AMRGs in hospital effluents, STP wastewater, and river water at the basin scale on the basis of mass flux as well as the contributions of CRE-E and ESBL-E to wastewater discharge into the river.

Investigation of the effect of microplastics on the UV inactivation of antibiotic-resistant bacteria in water

This study investigated the effect of polyethylene and polyvinyl chloride microplastics on the UV fluence response curve for the inactivation of multidrug-resistant E. coli and enterococci in ultrapure water at pH 6.0 ± 0.1. In the absence of microplastics, the UV inactivation of the studied bacteria exhibited an initial resistance followed by a faster inactivation of free (dispersed) bacteria, while in the presence of microplastics, these 2 regimes were followed by an additional regime of slower or no inactivation related to microplastic-associated bacteria (i.e., bacteria aggregated with microplastics resulting in shielding bacteria from UV indicated by tailing at higher UV fluences). The magnitude of the negative effect of microplastics varied with different microplastics (type/particle size) and bacteria (Gram-negative and Gram-positive). Results showed that when the UV transmittance of the microplastic-containing water was not taken into account in calculating UV fluences, the effect of microplastics as protectors of bacteria was overestimated. A UV fluence-based double-exponential microbial inactivation model accounting for both free and microplastic-associated bacteria could describe well the disinfection data. The present study elucidated the effect of microplastics on the performance of UV disinfection, and the approach used herein to prove this concept may guide future research on the investigation of the possible effect of other particles including nanoplastics with different characteristics on the exposure response curve for the inactivation of various microorganisms by physical and chemical disinfection processes in different water and wastewater matrices.

The elimination of cell-associated and non-cell-associated antibiotic resistance genes during membrane filtration processes: A review

With increasing water reuse as a sustainable water management strategy, antibiotic resistance genes (ARGs) which have been identified as emerging contaminants in wastewater are attracting global attentions. Given that wastewater treatment plants are now well-established as a sink and source of ARGs in both cell-associated and non-cell-associated forms, a need is acknowledged to reduce their proliferation and protect public health. Due to their different characteristics, cell-associated and non-cell-associated ARGs may have distinct responses to membrane filtration processes which are widely used as advanced treatment to the secondary effluent. This review improves the understanding of the abundance of cell-associated and non-cell-associated ARGs in wastewaters and the secondary effluents and compares the elimination of ARGs in cell-associated and non-cell-associated forms by low-pressure and high-pressure membrane filtration processes. The former process reduces the concentration of cell-associated ARGs by more than 2-logs on average. An increase of the retention efficiency of non-cell-associated ARGs is observed with decreasing molecular weight cut-offs in ultrafiltration. The high-pressure membrane filtration (i.e., nanofiltration and reverse osmosis) can effectively eliminate both cell-associated and non-cell-associated ARGs, with averagely more than 4.6-log reduction. In general, the two forms of ARGs can be removed from water by the membrane filtration processes via the effects of size exclusion, adsorption, and electrostatic repulsion. The size and conformation of cell-associated and non-cell-associated ARGs, characteristics of membranes, coexisting substances, and biofilm formation influence ARG retention. Accumulation and potential proliferation of cell-associated and non-cell-associated ARGs in foulants and concentrate and corresponding control strategies warrant future research.

Composition and contamination of source separated food waste from different sources and regulatory environments

Food waste recycling is needed to create a more sustainable, circular food system; however, the process must be carefully managed to avoid the introduction and build-up of contaminants. We collected and screened source-separated food waste for five classes of contaminants (physical contaminants, heavy metals, halogenated organics, pathogens and antibiotic resistance genes) from two regulatory environments (voluntary vs mandated food separation) to quantify contamination. Physical contamination was frequently found; 57% of samples contained non-compostable waste. Most heavy metals were not detected, and although copper and zinc were present in most samples, they were always below the most stringent global standards for compost. Some samples had detectable halogenated organics, including perfluoroalkyl substances (PFAS), which is cause for concern because some of these accumulate in the food chain. PFBA was detected in 60%, PFHxS in 8% and PFNA in 4% of samples tested. The pathogen Salmonella was present in 3% (2/71) and L. monocytogenes in 11% (8/71) of samples. Shiga toxin-producing E. coli was not detected. Next generation sequencing showed the presence of several genera that contain foodborne pathogens, most commonly Yersinia. Antibiotic resistance genes tet(M) and bla_TEM were present in 96% and 97% of samples respectively, however the last-resort colistin resistance gene mcr-1 was not detected. Overall contamination in our source-separated samples was low, with the exception of some antibiotic resistance genes, however our processing method might have underestimated packaging-associated contamination. Regulatory environment did not affect contamination, but carbon, nitrogen phosphorus, calcium, copper, tet (M), and physical contamination varied by source type.

Default predicted no-effect target concentrations for antibiotics in the absence of data for the protection against antibiotic resistance and environmental toxicity

The pharmaceutical manufacturing industry, via the AMR Industry Alliance, has developed and implemented steps to help minimize the potential impact of pharmaceutical manufacturing on the spread of antimicrobial resistance (AMR). One of these steps was to publish predicted no-effect concentrations (PNECs) to serve as targets for antibiotic manufacturing wastewater effluent risk assessments aimed to help protect environmental receptors and to mitigate against the spread of antibiotic resistance. Concentrations below which adverse effects in the environment are not expected to occur (PNECs) were first published in 2018 and are updated annually. The current list now stands at 125 antibiotics; however, it is recognized that this list does not encompass all manufactured antibiotics. Therefore, a statistical evaluation of currently available data was conducted and a default PNEC of 0.05 µg/L for antibiotics in the absence of other data was derived. Integr Environ Assess Manag 2022;18:863-867. © 2022 Merck, Sanofi, Johnson & Johnson Services, Inc, F.Hoffmann-La Roche Ltd, Teva Pharmaceuticals, GlaxoSmithKline, Novartis Pharma AG, and Pfizer lnc. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Efficient removal of antibiotic-resistant bacteria and intracellular antibiotic resistance genes by heterogeneous activation of peroxymonosulfate on hierarchical macro-mesoporous Co3O4-SiO2 with enhanced photogenerated charges

Antibiotic resistance genes (ARGs) and their host antibiotic-resistant bacteria (ARB) are widely detected in the environment and pose a threat to human health. Traditional disinfection in water treatment plants cannot effectively remove ARGs and ARB. This study explored the potential of a heterogeneous photo-Fenton-like process utilizing a hierarchical macro-mesoporous Co₃O₄-SiO₂ (MM CS) catalyst for activation of peroxymonosulfate (PMS) to inactivate ARB and degrade the intracellular ARGs. A typical gram-negative antibiotic-resistant bacteria called Pseudomonas sp. HLS-6 was used as a model ARB. A completed inactivation of ARB at ∼10⁷ CFU/mL was achieved in 30 s, and an efficient removal rate of more than 4.0 log for specific ARGs (sul1 and intI1) was achieved within 60 min by the MM CS-based heterogeneous photo-Fenton-like process under visible light and neutral pH conditions. Mechanism investigation revealed that •O₂^- and ¹O₂ were the vital reactive species for ARB inactivation and ARG degradation. The formation and transformation of the active species were proposed. Furthermore, the hierarchical macro-mesoporous structure of MM CS provided excellent optical and photoelectrochemical properties that promoted the cycle of Co³⁺/Co²⁺ and the effective utilization of PMS. This process was validated to be effective in various water matrices, including deionized water, underground water, source water, and secondary effluent wastewater. Collectively, this work demonstrated that the MM CS-based heterogeneous photo-Fenton-like process is a promising technology for controlling the spread of antibiotic resistance in aquatic environments.

Antimicrobial-Resistant Escherichia coli Distribution and Whole-Genome Analysis of Sequence Type 131 Escherichia coli Isolates in Public Restrooms in Taiwan

The threat of antibiotic-resistant bacteria to public health may originate from public restrooms. To better understand the community burden of antimicrobial-resistant Escherichia coli and sequence type complex 131 E. coli (STc131) in the public restroom, we performed a surveillance in public restrooms in southern Taiwan. Swabs were sampled from randomly selected public restrooms in Tainan, Taiwan in 2019. Antimicrobial susceptibility, phylogenetic grouping, and multiplex PCR were performed for the major ST complex in the B2 phylogenetic group. If STc131 isolates were identified, the whole-genome sequencing was performed. A total of 613 collection sites found 132 sites (21.5%) positive for E. coli. The most common phylogenetic group was A (30.9%) followed by B2 (30.3%). Ceftriaxone-resistant E. coli and extended-spectrum β-lactamases–producing E. coli were found in 2.4 and 1.0% of total public restrooms, respectively. The isolates in rural areas had higher ceftriaxone non-susceptibility than those in the city centers (3.9 vs. 1.2%, P = 0.038). Nine STc131 isolates were found in public restrooms, and most (77.8%) belonged to the subtype fimH41, whereas 22.2% belonged to fimH30. With the inclusion of STc131 isolates from human and dog fecal colonization in Taiwan, whole-genome sequencing was performed in 35 isolates. A large cluster of fimH41 in SNP-tree and GrapeTree was found from different sources (human, dog, and environment) and geographical areas. In conclusion, our surveillance of antimicrobial-resistant E. coli showed a higher prevalence of E. coli detected in public restrooms in the rural areas compared to those in city centers. The whole-genome sequence implies that fimH41 STc131 strains are successfully circulated in the community in Taiwan.

Fate of Clostridia and other spore-forming Firmicute bacteria during feedstock anaerobic digestion and aerobic composting

Pathogenic spore-forming Firmicutes are commonly present in animal and human wastes that are used as fertilizers in crop production. Pre-treatments of organic waste prior to land application offer the potential to abate enteric microorganisms, and therefore reduce the risk of contamination of crops or adjacent water resources with pathogens carried in these materials. The inactivation and reduction of gram-positive spore formers such as Clostridium spp., Clostridioides spp. and Bacillus spp. from animal and human waste can be challenging given the recalcitrance of the spores these bacteria produce. Given the significance of these organisms to human and animal health, information concerning spore-forming bacteria inactivation during anaerobic digestion (AD) and aerobic composting (AC) is required as the basis for recommending safe organic waste management practices. In this review, an assessment of the inactivation of spore-forming Firmicutes during AD and AC was conducted to provide guidance for practical management of organic matrices of animal or human origin. Temperature and pH may be the main factors contributing to the inactivation of spore-forming Firmicutes during batch lab-scale AD (log reduction <0.5-5 log). In continuous digesters, wet AD systems do not effectively inactivate spore-forming Firmicutes even under thermopholic conditions (log reduction -1.09 - 0.98), but dry AD systems could be a feasible management practice to inactivate spore-forming Firmicutes from organic materials with high solid content (log reduction 1.77-3.1). In contrast, composting is an effective treatment to abate spore-forming Firmicutes (log reduction 1.7-6.5) when thermophilic conditions last at least six consecutive days. Temperature, moisture content and composting scale are the key operating conditions influencing the inactivation of spore-forming Firmicutes during composting. Where possible, undertaking AD with subsequent composting to ensure the biosafety of digestate before its downstream processing and recycling is recommended to abate recalcitrant bacteria in digestate.

Hiding in plain sight - Wildlife as a neglected reservoir and pathway for the spread of antimicrobial resistance: A narrative review

Antimicrobial resistance represents a global health problem, with infections due to pathogenic antimicrobial resistant bacteria (ARB) predicted to be the most frequent cause of human mortality by 2050. The phenomenon of antimicrobial resistance has spread to and across all ecological niches, and particularly in livestock used for food production with antimicrobials consumed in high volumes. Similarly, hospitals and other healthcare facilities are recognized as significant “hotspots” of ARB and antimicrobial resistance genes (ARGs); however, over the past decade, new and previously overlooked ecological niches are emerging as hidden reservoirs of ARB/ARGs. Increasingly extensive and intensive industrial activities, degradation of natural environments, burgeoning food requirements, urbanization, and global climatic change have all dramatically affected the evolution and proliferation of ARB/ARGs, which now stand at extremely concerning ecological levels. While antimicrobial resistant bacteria and genes as they originate and emanate from livestock and human hosts have been extensively studied over the past 30 years, numerous ecological niches have received considerably less attention. In the current descriptive review, the authors have sought to highlight the importance of wildlife as sources/reservoirs, pathways and receptors of ARB/ARGs in the environment, thus paving the way for future primary research in these areas.

Motivation of reactive oxygen and nitrogen species by a novel non-thermal plasma coupled with calcium peroxide system for synergistic removal of sulfamethoxazole in waste activated sludge

Large amounts of antibiotics are concentrated in waste activated sludge (WAS) and released into the environment. It is thus critical to develop advanced sludge treatment technology to remove these antibiotics. Dielectric barrier discharge (DBD) combined with calcium peroxide (CaO₂), as an innovative technology to attenuate sulfamethoxazole (SMX) in sludge, was investigated. Evident synergistic effects between DBD and CaO₂ were observed on the SMX degradation with a synergistic factor of 2.02. Moreover, the energy consumption of DBD/CaO₂ was significantly lower than that of DBD alone. At a typical CaO₂ dosage of 0.1 g/g TS and discharge power of 64.5 W, the highest SMX removal of 96% was achieved within 50 min. The synergistic effects of DBD/CaO₂ could be associated with the base catalysis of H₂O₂ and O₃, UV-base-photolysis, peroxone oxidation, and photocatalytic H₂O₂. DBD/CaO₂ generated various reactive oxygen species (ROS) and nitrogen species (RNS) that participated in SMX removal. The contributions of these reactive species followed the sequence of e^- > •OH > •O₂^- > ¹O₂ > ONOO^-. Based on the detected transformation by-products and their variations during treatment, a plausible SMX degradation pathway in sludge was proposed. Besides, DBD/CaO₂ also promoted sludge disintegration, dewatering, heavy metal removal, sludge reduction, sludge solubilization, and acetate-enriched volatile fatty acid (VFA) production. Therefore, DBD/CaO₂ exhibited great potential for controlling antibiotic, as well as promoting sludge reduction, decontamination, and resourcization.

Inactivation of Antibiotic-Resistant Bacteria in Wastewater by Ozone-Based Advanced Water Treatment Processes

The inactivating effect of ozone (O₃)-based advanced oxidation processes (AOPs) (O₃/H₂O₂, O₃/UV, and O₃/UV/H₂O₂ systems) on antimicrobial-resistant bacteria (AMRB) and antimicrobial-susceptible bacteria (AMSB) in sewage treatment plant (STP) wastewater was investigated. The AMRB were grouped into six classes: carbapenem-resistant Enterobacteriaceae (CRE), extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E), multidrug-resistant Acinetobacter (MDRA), multidrug-resistant Pseudomonas aeruginosa (MDRP), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE); these classes constituted the World Health Organization (WHO) global priority list of AMRB. The results indicate that O₃-based advanced wastewater treatment inactivated all AMRB and AMSB (>99.9%) after 10 min of treatment, and significant differences (p < 0.5) were not observed in the disinfection of AMRB and AMSB by each treatment. Altered taxonomic diversity of micro-organisms based on 16S rRNA gene sequencing via O₃/UV and O₃/UV/H₂O₂ treatment showed that advanced wastewater treatments not only inactivated AMRB but also removed antimicrobial resistance genes (AMRGs) in the wastewater. Consequently, this study recommends the use of advanced wastewater treatments for treating the STP effluent, reducing environmental pollution, and alleviating the potential hazard to human health caused by AMRB, AMSB, and infectious diseases. Overall, this study provides a new method for assessing environmental risks associated with the spread of AMRB and AMSB in aquatic environments, while keeping the water environment safe and maintaining human health.

Bioleaching rather than chemical conditioning using Fe[III]/CaO or polyacrylamide mitigates antibiotic resistance in sludge composting via pre-removing antibiotic resistance genes and limiting horizontal gene transfer

Conditioning can drastically improve the dewaterability of sewage sludge and is widely practiced in most wastewater treatment plants (WWTPs). Sludge conditioning was also reported as a crucial step in sludge treatment to attenuate antibiotic resistance, but it remains unclear whether the attenuated antibiotic resistance by conditioning treatments would guarantee low abundance of antibiotic resistance genes (ARGs) in the compost products of municipal sewage sludge. Herein, the impacts of three conditioning treatments, including bioleaching and chemical conditioning using Fe[III]/CaO or polyacrylamide (PAM), on the abundances of 20 ARGs and 4 mobile genetic elements (MGEs) during conventional aerobic composting of dewatered sludge were investigated. It was found that the absolute and relative abundances of total ARGs in compost product of bioleached sludge accounted for only 13.8%-28.8% of that in compost products of un-conditioned, Fe[III]/CaO-conditioned, or PAM-conditioned sludges. Besides, bioleaching conditioning resulted in the lowest abundances of ARG subtypes and ARG-associated bacteria in the sludge compost product. The shift of ARG profiles in the bioleached sludge composting can be mainly ascribed to the ARG-associated bacteria, while the MGEs drove the ARG profiles during conventional composting of un-conditioned sludge and the two chemically conditioned sludge. Thus, bioleaching conditioning is superior to the chemical conditioning using Fe[III]/CaO or PAM in mitigating antibiotic resistance in sludge compost products, which was contributed by the pre-removal of ARGs prior to composting treatment and the potential limitation of ARGs transfer during conventional composting.

Soil type shapes the antibiotic resistome profiles of long-term manured soil

Animal manure fertilization facilitates the proliferation and dissemination of antibiotic resistance genes (ARGs) in soil, posing high risks to humans and ecosystem health. Although studies suggest that soil types could shape the ARG profiles in greenhouse soil, there is still a lack of comparative studies on the fate of ARGs in different types of manured soils under field trials. Thus, a metagenomic approach was used to decipher the fate of ARGs in 12-year long-term fertilized (inorganic fertilizer, compost manure and a mix of them) acidic, near-neutral and alkaline soils. A total of 408 unique ARG subtypes with multidrug, glycopeptide, beta-lactam and aminoglycoside resistance genes were identified as the most universal ARG types in all soil samples. Genes conferred to beta-lactam was the predominant ARG type in all the manure-amended soils. Genomic and statistical analyses showed that manure application caused the enrichment of 98 and 91 ARG subtypes in acidic and near-neutral soils, respectively, and 8 ARG subtypes in alkaline soil. The abundances of Proteobacteria (acidic and near-neutral soils) and Actinobacteria (alkaline soil), which are the potential hosts of ARGs, were clearly increased in manured soils. Random forest modelling and Pearson correlation analysis revealed that the soil properties (pH and bio-available Zn) and mobile genetic elements had considerable impacts on the transmission of ARGs. A structural equation model further indicated that soil types shaped the ARG profiles by significantly (P < 0.01) influencing the soil properties, bacterial abundance and bacterial diversity, where bacterial abundance was the major factor influencing the ARG profiles. This study systematically explored the mechanisms shaping the ARG profiles of long-term manured soils, and this information could support strategies to manage the dissemination of ARGs in different soil types.

Recycling of Expired Ceftamil Drug as Additive in the Copper and Nickel Electrodeposition from Acid Baths

Due to the large quantity of expired and unused drugs worldwide, pharmaceutical disposal has become a serious problem that requires increased attention. In the present paper, the study on recycling ceftazidime (CZ) as an additive in copper and nickel electrodeposition from acid baths is highlighted. CZ is the active substance from expired commercial drug Ceftamil^®. Its electrochemical behavior was studied by cyclic voltammetry. As well, kinetic parameters for copper and nickel electrodeposition were determined using Tafel plots method at different temperatures and CZ concentrations in these acid baths. The activation energy was calculated from Arrhenius plots. Electrochemical impedance spectroscopy was used to investigate the charge transfer resistance and coverage degree in the electrolyte solutions at several potential values. Gibbs free energy values, calculated from Langmuir adsorption isotherms, revealed the chemical nature of CZ–electrode surface interactions. The favorable effect of the organic molecules added in copper and nickel electroplating baths was emphasized by optical microscope images. The morphology of the obtained deposits without and with 10⁻⁴ mol L⁻¹ CZ was compared. The experimental results revealed that expired Ceftamil^® is suitable as additive in copper and nickel electroplating processes from acid baths.

Antibiotic-Resistant Genes and Bacteria as Evolving Contaminants of Emerging Concerns (e-CEC): Is It Time to Include Evolution in Risk Assessment?

The pressing issue of the abundance of antibiotic resistance genes and resistant bacteria in the environment (ARGs and ARB, respectively) requires procedures for assessing the risk to health. The chemo-centric environmental risk assessment models identify hazard(s) in a dose–response manner, obtaining exposure, toxicity, risk, impact and policy. However, this risk assessment approach based on ARGs/ARB evaluation from a quantitative viewpoint shows high unpredictability because ARGs/ARB cannot be considered as standard hazardous molecules: ARB duplicate and ARGs evolve within a biological host. ARGs/ARB are currently listed as Contaminants of Emerging Concern (CEC). In light of such characteristics, we propose to define ARGs/ARB within a new category of evolving CEC (or e-CEC). ARGs/ARB, like any other evolving determinants (e.g., viruses, bacteria, genes), escape environmental controls. When they do so, just one molecule left remaining at a control point can form the origin of a new dangerous and selection-responsive population. As a consequence, perhaps it is time to acknowledge this trait and to include evolutionary concepts within modern risk assessment of e-CEC. In this perspective we analyze the evolutionary responses most likely to influence risk assessment, and we speculate on the means by which current methods could measure evolution. Further work is required to implement and exploit such experimental procedures in future risk assessment protocols.

Simultaneous inactivation of multidrug-resistant Escherichia coli and enterococci by peracetic acid in urban wastewater: Exposure-based kinetics and comparison with chlorine

The presence of antibiotic resistance in wastewater sparked a great interest in investigating the inactivation of antibiotic-resistant bacteria by disinfecting agents. In this study, the inactivation kinetics of multidrug-resistant E. coli and enterococci by an emerging environmentally-friendly disinfectant, peracetic acid (PAA), in wastewater and phosphate buffer at pH 6.5 and pH 7.5, were characterized. It was demonstrated that the inactivation of the studied multidrug-resistant bacteria was governed by their exposure to PAA, i.e., integral of the PAA concentration over time (integral CT or ICT). Both regimes of the PAA inactivation of bacteria, i.e., initial resistance followed by a faster inactivation, were described well by an ICT-based Chick-Watson inactivation kinetic model. In wastewater at pH 7.5, the model-predicted ICT requirements showed that the multidrug-resistant enterococci were less susceptible to PAA than E. coli, e.g., to achieve a 3-log reduction, an ICT of 32.7 mg min/L and 23.4 mg min/L was needed, respectively. No regrowth of the studied bacteria was observed after 72 h from PAA disinfection at 25 ± 1 °C. Soluble constituents of wastewater decreased the PAA inactivation of both multidrug-resistant bacteria, i.e., higher inactivation was observed in phosphate buffer than wastewater at the same pH of 7.5. In phosphate buffer, a lower pH of 6.5 resulted in higher inactivation of multidrug-resistant E. coli compared with pH 7.5, but it did not affect the PAA inactivation of multidrug-resistant enterococci. A comparison with the most commonly used chemical disinfectant, chlorine, showed higher inactivation of both multidrug-resistant bacteria by chlorine and higher chlorine decay than PAA. The results of the present study may have implications in designing a PAA disinfection process, aiming at controlling antibiotic resistance, in terms of selecting a suitable fecal indicator and optimizing disinfectant dosing.

Occurrence and distribution of antibiotics and corresponding antibiotic resistance genes in different soil types irrigated with treated wastewater

Diminishing freshwater (FW) supplies necessitate the reuse of treated wastewater (TWW) for various purposes, like irrigation of agricultural lands. However, there is a growing concern that irrigation with TWW may transfer antibiotic resistance genes (ARGs) to the soil and crops. We hypothesized that TWW irrigation would increase the prevalence of antibiotic residues together with the corresponding ARGs in the irrigated soil. We further predicted that soil texture, especially pH, clay content, and organic matter variabilities, would change the antibiotic residues concentrations and thus ARGs dissemination. To test our predictions, three soils types (loamy-sand, loam, and clay) were irrigated with two water types (FW and TWW), over two consecutive seasons. We monitored physico-chemical parameters, the abundance of seven antibiotic residues, and their corresponding ARGs together with class 1 integron (intI1) in 54 water and soil samples collected at the end of the field experiments. The results revealed increase in antibiotics concentrations and ARGs relative abundance in TWW than FW. Yet, in the soil ARGs relative abundances were independent of the irrigation water quality, but dependent on the soil type, especially the clay content. Further, there were no clear associations between the targeted antibiotics or the presence of heavy metals and ARGs' relative abundance in the water or soil samples. Therefore, our results question the link between the discharge of antibiotics and heavy metals, and the dissemination of ARGs in soil environments.

Investigating antibiotics, antibiotic resistance genes in soil, groundwater and vegetables in relation to agricultural field - Applicated with lincomycin mycelial residues compost

Antibiotic mycelial residue, a kind of organic bio-waste, after composting with the subsequent land application is an effective way to achieve its resource utilization. However, its influences on soil quality and ecological safety in the practical agricultural field and related environmental media, e.g., groundwater and vegetables, remain investigated. In the present study, a field experiment with vegetable plants was conducted to study the influences of lincomycin mycelial residue compost (LMRC) on soil quality, and antibiotics and ARGs' fate. In particular, soil physicochemical properties and microbial community composition were analyzed. Moreover, antibiotics and ARGs' evolution in soil, vegetable, and groundwater were determined. The results showed that the LMRC amendment enhanced soil fertility with the increases of organic matter, total nitrogen, and available P/K. Enzyme activities except catalase and urease were promoted, and they were positively related to the LMRC application ratio. Soil microbial community composition presented temporary shifts as LMRC added, and the low application amount soil showed no significant difference with control at the end of the experiment. Similarly, lincomycin concentration in soil was far lower than the background, and it decreased below the predicted no-effect concentration in groundwater. Besides, the detected lincomycin in pakchoi grew in 0.5% and 1% LMRC amended soil was lower than acceptable daily intake (30 μg/kg). Low application rate (0.5%) of LMRC caused no significant changes of tested ARGs in soil, vegetables, and groundwater. Information obtained from this study provides reasonable application strategies for LMRC that with environmental acceptable antibiotic and ARGs.

On-site chlorination responsible for effective disinfection of wastewater from hospital

Both hospital effluent and a model sewage treatment plant (STP) wastewater prepared by mixing STP influent and STP secondary effluent at a volume ratio of 1:9 were directly treated with chlorine for investigation of their effects on disinfection of antimicrobial-resistant bacteria (AMRB) and antimicrobial-susceptible bacteria (AMSB). The overall results indicate that the chlorine disinfection effectively inactivated the majority of AMRB and AMSB, expect for MRSA and Staphylococcus aureus in both wastewaters. No significant differences could further be observed in the taxonomic diversity of micro-organisms after the treatment. The degrees of disinfection given by the direct chlorination were comparable to those attained by combination of conventional activated sludge process and additional chlorine treatment at the STP. The results of this study evoked a recommendation to operate local chlorination treatment directly for the wastewater from medicinal facilities prior to its flow into the STP as sewage. Although additional disinfection treatment at the STP seems necessary to remove the recalcitrant MRSA and Staphylococcus aureus, the present study desirably contributes to a great reduction of the loads of STP and urgent prevention of spreading of infectious diseases in the present state.

Effects of natural sunlight on antimicrobial-resistant bacteria (AMRB) and antimicrobial-susceptible bacteria (AMSB) in wastewater and river water

The effects of natural sunlight on antimicrobial-resistant bacteria (AMRB) and antimicrobial-susceptible bacteria (AMSB) were investigated in three types of water: sewage treatment plant (STP) influent, STP secondary effluent, and river water in an urban area of Japan. The AMRB were grouped into six classes: carbapenem-resistant Enterobacteriaceae (CRE), extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E), multi-drug-resistant Acinetobacter (MDRA), multi-drug-resistant Pseudomonas aeruginosa (MDRP), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE). The amount of each group of bacteria present was estimated using specific chromogenic agar formulations. AMRB were detected in all water samples, with 13-2,407 colony-forming units (CFU)/mL in the STP influent, N.D. to 202 CFU/mL in the secondary STP effluent, and N.D. to 207 CFU/mL in the river water. The distribution profiles of the AMSB in water samples were similar to those of AMRB. The degree to which AMRB and AMSB present in the river water were inactivated by natural sunlight was tested as the main aim of this study. Irradiation by natural sunlight was found to inactivate almost 100% of all the target AMRB after 5 h of exposure, with no significant differences (P < 0.05) observed in the effects that sunlight had on AMSB and AMRB. Analysis of the bacterial community structure based on 16S rRNA gene sequencing showed that the structure of the bacterial community was apparently not affected by the exposure to sunlight. In addition, the taxonomic diversity in the STP secondary effluent did not change as a result of additional disinfection with chlorine. The results of this study suggest that it is possible that exposure to sunlight could be used as an alternative to disinfection via chlorine. To our knowledge, this is the first report to demonstrate the mitigation of AMSB and AMRB pollution in a river environment via the exposure to natural sunlight.

Mg2TiO4 spinel modified by nitrogen doping as a Visible-Light-Active photocatalyst for antibacterial activity

Nitrogen doped Mg₂TiO₄ spinel, i.e. Mg₂TiO_4-xN_y, has been synthesized and investigated as a photocatalyst for antibacterial activity. Mg₂TiO_4-xN_y demonstrates superior photocatalytic activity for E. coli disinfection under visible light illumination (λ ≥ 400 nm). Complete disinfection of E. coli at a bacterial cell density of 1.0 × 10⁷ CFU mL^-1 can be achieved within merely 60 min. Mg₂TiO_4-xN_y is capable of generating superoxide radicals (^•O₂ ^-) under visible light illumination which are the reactive oxygen species (ROSs) for bacteria disinfection. DFT calculations have verified the importance of nitrogen dopants in improving the visible light sensitivity of Mg₂TiO_4-xN_y. The facile synthesis, low cost, good biocompatibility and high disinfection activity of Mg₂TiO_4-xN_y warrant promising applications in the field of water purification and antibacterial products.

Removal of pathogen and antibiotic resistance genes from waste activated sludge by different pre-treatment approaches

In wastewater treatment plants, most of the pathogens and antibiotic resistant genes (ARGs) transferred into and concentrated in waste activated sludge (WAS), which would cause severe public health risks. In this study, the capabilities of several WAS pre-treatment approaches to inactivate coliforms/E. coli and ARGs, as well as the subsequent regrowth of coliforms/E. coli and ARGs/intI1 in treated sludge were investigated. The results showed that electro-Fenton (EF), with continuous hydroxyl radical generation, could efficiently inactivate coliforms/E. coli in 60 min (about 4 log units), followed by methanol (MT), anode oxidization (AO), and acidification (AT). Kinetic analysis showed that the inactivation mainly occurred in the first 10 min. However, the efficiencies of all studied pre-treatment approaches on inactivating ARGs/intI1 (<2 log units) were lower than coliforms/E. coli, whilst EF still had the highest efficiency of ARGs/intI1 reduction. Mechanical ultrasound treatment (ULS) could not inactivate coliforms/E. coli in WAS, but it could efficiently reduce ARGs/intI1. High regrowth rates of coliforms/E. coli were observed in the treated WAS in 10 days, but the abundances of ARGs/intI1 continuously reduced during the after-treatment incubation. Our study showed that EF could efficiently disinfect potential pathogens, however, the reduction of ARGs/intI1 in WAS need further investigation.

Simultaneously attenuating antibiotic resistance genes and improving the dewaterability of sewage sludge by conditioning with Fenton's reagent: the pivotal role of sludge pre-acidification

Fenton conditioning processes have been recently employed to improve the dewaterability of sewage sludge. However, it remains unclear whether the conditioning with Fenton's reagent would simultaneously attenuate antibiotic resistance genes (ARGs) in sludge and improve sludge dewaterability. It was found in the present study that sludge pre-acidification played a pivotal role in simultaneously removing ARGs and improving sludge dewaterability by conditioning with Fenton's reagent. When the sewage sludge was pre-acidified to pH = 3.0 and was then conditioned using Fenton's reagent, the absolute abundances of the total ARGs and the total mobile genic elements (MGEs) in conditioned sludge were reduced by 1.85-2.10 and 2.84-3.12 log units, respectively. Additionally, sludge capillary suction time (CST) and specific resistance to filtration (SRF) were drastically reduced, and the moisture content (MC) in dewatered sludge cake was reduced to only 60.61-69.95%. Such effective attenuation of ARGs and MGEs in conditioned sludge led to their removal in both the dewatered sludge cakes and dewatering filtrate. However, only the improvement of sludge dewaterability was attained by sludge conditioning with Fenton's reagent but without sludge pre-acidification. During the conditioning treatment, the removal of loosely bound extracellular polymeric substance (EPS) and tightly bound EPS in conditioned sludge contributed to the improvement of sludge dewaterability, and the damage of sludge microbial cells was highly correlated with the attenuation of antibiotic resistance. Thus, sludge pre-acidification combined with conditioning using Fenton's reagent can be employed to simultaneously attenuate the antibiotic resistance in sewage sludge and improve sludge dewaterability.

A review of chemical and microbial contamination in food: What are the threats to a circular food system?

A circular food system is one in which food waste is processed to recover plant nutrients and returned to the soil to enable the production of more food, rather than being diverted to landfill or incineration. The approach may be used to reduce energy and water use in food production and contribute to the sustainability of the system. Anaerobic digestion and composting are common food waste treatment technologies used to stabilize waste and produce residual materials that can replenish the soil, thus contributing to a circular food system. This approach can only be deemed safe and feasible, however, if food waste is uncontaminated or any contaminants are destroyed during treatment. This review brings together information on several contaminant classes at different stages of the food supply chain, their possible sources, and their fates during composting and digestion. The main aim is to identify factors that could impede the transition towards a safe, reliable and efficient circular food system. We investigated heavy metals, halogenated organic compounds, foodborne pathogens and antibiotic resistance genes (ARGs) in the food system and their fates during digestion and composting. Production and processing stages were identified as major entry points for these classes of contaminants. Heavy metals and foodborne pathogens pose less risk in a circular system than halogenated organics or antibiotic resistance. Given the diversity of properties among halogenated organic compounds, there is conflicting evidence about their fate during treatment. There are relatively few studies on the fate of ARGs during treatment, and these have produced variable results, indicating a need for more research to clarify their fate in the final products. Repeated land application of contaminated food waste residuals can increase the risk of accumulation and jeopardize the safety of a circular food system. Thus, careful management of the system and research into the fate of the contaminants during treatment is needed.

Antibiotic resistance development and human health risks during wastewater reuse and biosolids application in agriculture

The reuse of treated wastewater (TWW) and sewage sludge are considered as solutions to the limited water resource and sludge disposal issues, respectively. The associated environmental and human health risks need to be analyzed to assess whether they are safe solutions or not. This paper discusses issues that relate to the accumulation of antibiotics and antibiotic resistance (AR) determinants in agricultural lands and crops, following TWW irrigation and biosolid amendment. Exposure assessment and dose-response assessment are the two important aspects of risk assessment discussed in this paper. Finally, research gaps in current knowledge that are relevant to a comprehensive and quantitative AR risk assessment were identified which includes: 1.) Studies on soil conditions that increase the frequency of horizontal gene transfer (HGT) between native soil resistome and pathogenic microbes in biosolids and TWW 2.) Holistic studies that examine the accumulation or dissipation of antibiotics, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from the irrigation/biosolids application stage to crop consumption stage 3.) The influences of soil environmental conditions (e.g. salinity, nutrients) on the fate of ARB and ARGs in soil and translocation in edible plants 4.) The development of dose-response models that explicitly incorporate the potential for ARGs transfer between microbes when quantifying the risks of infection due to ARB.

Insects, Rodents, and Pets as Reservoirs, Vectors, and Sentinels of Antimicrobial Resistance

This paper reviews the occurrence of antimicrobial resistance (AMR) in insects, rodents, and pets. Insects (e.g., houseflies, cockroaches), rodents (rats, mice), and pets (dogs, cats) act as reservoirs of AMR for first-line and last-resort antimicrobial agents. AMR proliferates in insects, rodents, and pets, and their skin and gut systems. Subsequently, insects, rodents, and pets act as vectors that disseminate AMR to humans via direct contact, human food contamination, and horizontal gene transfer. Thus, insects, rodents, and pets might act as sentinels or bioindicators of AMR. Human health risks are discussed, including those unique to low-income countries. Current evidence on human health risks is largely inferential and based on qualitative data, but comprehensive statistics based on quantitative microbial risk assessment (QMRA) are still lacking. Hence, tracing human health risks of AMR to insects, rodents, and pets, remains a challenge. To safeguard human health, mitigation measures are proposed, based on the one-health approach. Future research should include human health risk analysis using QMRA, and the application of in-silico techniques, genomics, network analysis, and ’big data’ analytical tools to understand the role of household insects, rodents, and pets in the persistence, circulation, and health risks of AMR.

Sources of Antibiotic Resistant Bacteria (ARB) and Antibiotic Resistance Genes (ARGs) in the Soil: A Review of the Spreading Mechanism and Human Health Risks

Soil is an essential part of our ecosystem and plays a crucial role as a nutrient source, provides habitat for plants and other organisms. Overuse of antibiotics has accelerated the development and dissemination of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). ARB and ARGs are recognized as emerging environmental contaminants causing soil pollution and serious risks to public health. ARB and ARGs are discharged into soils through several pathways. Application of manure in agriculture is one of the primary sources of ARB and ARGs dissemination in the soil. Different sources of contamination by ARB and ARGs were reviewed and analyzed as well as dissemination mechanisms in the soil. The effects of ARB and ARGs on soil bacterial community were evaluated. Furthermore, the impact of different sources of manure on soil microbial diversity as well as the effect of antibiotics on the development of ARB and ARGs in soils was analyzed. Human health risk assessments associated with the spreading of ARB and ARGs in soils were investigated. Finally, recommendations and mitigation strategies were proposed.

Pyroligneous acid mitigated dissemination of antibiotic resistance genes in soil

Strategies to mitigate the spread of antibiotic resistance genes (ARGs) in soils are urgently needed. Therefore, a pristine pyroligneous acid (PA) from pyrolyzing blended woody waste at 450 °C and its three fractions distilled at 98, 130, and 220 °C (F1, F2, and F3) were used to evaluate their feasibility of reducing ARGs in soil. Application of PA, F2, and F3 effectively decreased the relative ARG abundance by 22.4-75.4% and 39.7-66.7% in the rhizosphere and bulk soil relative to control, respectively, and the removal efficiency followed an order of F3 > PA > F2. Contrarily, F1 increased the abundance of ARGs. The decreased abundance of two mobile genetic elements and impaired conjugative transfer of RP4 plasmid in the presence of PA, F2 and F3 demonstrated that the weakened horizontal gene transfer (HGT) contributed to the reduced ARG level. Variation partitioning analysis and structural equation models confirmed that ARG reduction was primarily driven by the weakened HGT, followed by the decreased co-selection of heavy metals and shifted bacterial community (e.g., reduced potential host bacteria of ARGs). Our findings provide practical and technical support for developing PA-based technology in remediating ARG-contaminated soil to ensure food safety and protect human health.

Composting of chicken litter from commercial broiler farms reduces the abundance of viable enteric bacteria, Firmicutes, and selected antibiotic resistance genes

We examined the ability of composting to remove ARGs and enteric bacteria in litter obtained from broiler chickens fed with a diet supplemented with Bacitracin methylene disalicylate (BDM) (conventional chicken litter), or an antibiotic-free diet (raised without antibiotic (RWA) chicken litter). This was done by evaluating the litter before and after composting for the abundance of ten gene targets associated with antibiotic resistance or horizontal gene transfer, the composition of the bacterial communities, and the abundance of viable enteric bacteria. The abundance of gene targets was determined by qPCR and the microbial community composition of chicken litter determined by 16S rRNA gene amplicon sequencing. Enteric bacteria were enumerated by viable plate count. A majority of the gene targets were more abundant in conventional than in RWA litter. In both litter types, the absolute abundance of all of the target genes decreased after composting except sul1, intI1, incW and erm(F) that remained stable. Composting significantly reduced the abundance of enteric bacteria, including those carrying antibiotic resistance. The major difference in bacterial community composition between conventional and RWA litter was due to members affiliated to the genus Pseudomonas, which were 28% more abundant in conventional than in RWA litter. Composting favoured the presence of thermophilic bacteria, such as those affiliated with the genus Truepera, but decreased the abundance of those bacterial genera associated with cold-adapted species, such as Carnobacterium, Psychrobacter and Oceanisphaera. The present study shows that chicken litter from broilers fed with a diet supplemented with antibiotic has an increased abundance of some ARGs, even after composting. However, we can conclude that fertilization with composted litter represents a reduced risk of transmission of antibiotic resistance genes and enteric bacteria of poultry origin to soil and crops than will fertilization with raw litter.

Increased (Antibiotic-Resistant) Pathogen Indicator Organism Removal during (Hyper-)Thermophilic Anaerobic Digestion of Concentrated Black Water for Safe Nutrient Recovery

Source separated toilet water is a valuable resource for energy and fertilizers as it has a high concentration of organics and nutrients, which can be reused in agriculture. Recovery of nutrients such as nitrogen, phosphorous, and potassium (NPK) decreases the dependency on energy-intensive processes or processes that rely on depleting natural resources. In new sanitation systems, concentrated black water (BW) is obtained by source-separated collection of toilet water. BW-derived products are often associated with safety issues, amongst which pathogens and antibiotic-resistant pathogens. This study presents results showing that thermophilic (55–60 °C) and hyperthermophilic (70 °C) anaerobic treatments had higher (antibiotic-resistant) culturable pathogen indicators removal than mesophilic anaerobic treatment. Hyperthermophilic and thermophilic anaerobic treatment successfully removed Escherichia coli and extended-spectrum β-lactamases producing E. coli from source-separated vacuum collected BW at retention times of 6–11 days and reached significantly higher removal rates than mesophilic (35 °C) anaerobic treatment (p < 0.05). The difference between thermophilic and hyperthermophilic treatment was insignificant, which justifies operation at 55 °C rather than 70 °C. This study is the first to quantify (antibiotic-resistant) E. coli in concentrated BW (10–40 gCOD/L) and to show that both thermophilic and hyperthermophilic anaerobic treatment can adequately remove these pathogen indicators.

Antibiotic Resistance in Recreational Waters: State of the Science

Ambient recreational waters can act as both recipients and natural reservoirs for antimicrobial resistant (AMR) bacteria and antimicrobial resistant genes (ARGs), where they may persist and replicate. Contact with AMR bacteria and ARGs potentially puts recreators at risk, which can thus decrease their ability to fight infections. A variety of point and nonpoint sources, including contaminated wastewater effluents, runoff from animal feeding operations, and sewer overflow events, can contribute to environmental loading of AMR bacteria and ARGs. The overall goal of this article is to provide the state of the science related to recreational exposure and AMR, which has been an area of increasing interest. Specific objectives of the review include (1) a description of potential sources of antibiotics, AMR bacteria, and ARGs in recreational waters, as documented in the available literature; (2) a discussion of what is known about human recreational exposures to AMR bacteria and ARGs, using findings from health studies and exposure assessments; and (3) identification of knowledge gaps and future research needs. To better understand the dynamics related to AMR and associated recreational water risks, future research should focus on source contribution, fate and transport-across treatment and in the environment; human health risk assessment; and standardized methods.

Antibiotic resistome and microbial community structure during anaerobic co-digestion of food waste, paper and cardboard

Solid organic waste is a significant source of antibiotic resistance genes (ARGs) and effective treatment strategies are urgently required to limit the spread of antimicrobial resistance. Here, we studied ARG diversity and abundance as well as the relationship between antibiotic resistome and microbial community structure within a lab-scale solid-state anaerobic digester treating a mixture of food waste, paper and cardboard. A total of 10 samples from digester feed and digestion products were collected for microbial community analysis including small subunit rRNA gene sequencing, total community metagenome sequencing and high-throughput quantitative PCR. We observed a significant shift in microbial community composition and a reduction in ARG diversity and abundance after 6 weeks of digestion. ARGs were identified in all samples with multidrug resistance being the most abundant ARG type. Thirty-two per cent of ARGs detected in digester feed were located on plasmids indicating potential for horizontal gene transfer. Using metagenomic assembly and binning, we detected potential bacterial hosts of ARGs in digester feed, which included Erwinia, Bifidobacteriaceae, Lactococcus lactis and Lactobacillus. Our results indicate that the process of sequential solid-state anaerobic digestion of food waste, paper and cardboard tested herein provides a significant reduction in the relative abundance of ARGs per 16S rRNA gene.

Manure as a Potential Hotspot for Antibiotic Resistance Dissemination by Horizontal Gene Transfer Events

The increasing demand for animal-derived foods has led to intensive and large-scale livestock production with the consequent formation of large amounts of manure. Livestock manure is widely used in agricultural practices as soil fertilizer worldwide. However, several antibiotic residues, antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria are frequently detected in manure and manure-amended soils. This review explores the role of manure in the persistence and dissemination of ARGs in the environment, analyzes the procedures used to decrease antimicrobial resistance in manure and the potential impact of manure application in public health. We highlight that manure shows unique features as a hotspot for antimicrobial gene dissemination by horizontal transfer events: richness in nutrients, a high abundance and diversity of bacteria populations and antibiotic residues that may exert a selective pressure on bacteria and trigger gene mobilization; reduction methodologies are able to reduce the concentrations of some, but not all, antimicrobials and microorganisms. Conjugation events are often seen in the manure environment, even after composting. Antibiotic resistance is considered a growing threat to human, animal and environmental health. Therefore, it is crucial to reduce the amount of antimicrobials and the load of antimicrobial resistant bacteria that end up in soil.

Multimedia mass balance approach to characterizing the transport potential of antibiotics in soil-plant systems following manure application

Antibiotics are ubiquitous in agro-ecosystems worldwide, which can pose remarkable risks to ecological security and human health. However, comprehensive evaluation on the multimedia fate and transport potential of antibiotics in soil-plant systems is still lacking. A mass balance approach was performed to gain insights into the transport and fate of antibiotics in soil-plant systems following manure application. Our results showed that more than 99 % of antibiotics were released from applied manure fertilizer into the soil-plant system. Antibiotic concentrations in soil and plant compartments increased over 120 days. Most of the antibiotics persisted in soil (about 65 %), while less than 0.1 % accumulated in the plants. Rainfall-induced runoff, subsurface interflow and soil water infiltration were alternative transport pathways for antibiotics in soil-plant systems although their contributions were limited. Dissipation was the main removal pathway for antibiotics accounting for about 33 % of total input mass. Tetracyclines had higher mass proportion in soil following by quinolones, whereas most of sulfonamides and macrolides were dissipated. Mass balance approach based on tracking environmental fates of antibiotics can facilitate the understandings in the source comparisons and mitigation strategies, and therefore provide insights to inform modeling and limiting the transport of manure-borne antibiotics to neighboring environmental compartments.