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673300.9922Bioavailability of tetracycline to antibiotic resistant Escherichia coli in water-clay systems. Tetracyclines are a class of antimicrobials frequently found in the environment, and have promoted the proliferation of antibiotic resistance. An unanswered research question is whether tetracycline sorbed to soils is still bioavailable to bacteria and exerts selective pressure on the bacterial community for the development of antibiotic resistance. In this study, bioreporter E. coli MC4100/pTGM strain was used to probe the bioavailability of tetracycline sorbed by smectite clay, a class of common soil minerals. Batch sorption experiments were conducted to prepare clay samples with a wide range of sorbed tetracycline concentration. The bioreporter was incubated with tetracycline-sorbed clay at different clay/solution ratios and water contents, as well as using dialysis tubings to prevent the direct contact between bacterial cells and clay particles. The expression of antibiotic resistance genes from the bioreporter was measured using a flow cytometer as a measurement of bioavailability/selective pressure. The direct contact of bioreporter cells to clay surfaces represented an important pathway facilitating bacterial access to clay-sorbed tetracycline. In clay-water suspensions, reducing solution volume rendered more bacteria to attach to clay surfaces enhancing the bioavailability of clay-sorbed tetracycline. The strong fluorescence emission from bioreporter cells on clay surfaces indicated that clay-sorbed tetracycline was still bioavailable to bacteria. The formation of biofilms on clay surfaces could increase bacterial access to clay-sorbed tetracycline. In addition, desorption of loosely sorbed tetracycline into bulk solution contributed to bacterial exposure and activation of the antibiotic resistance genes. Tetracycline sorbed by soil geosorbents could exert selective pressure on the surrounding microbial communities via bacterial exposure to tetracycline in solution from desorption and to the geosorbent-sorbed tetracycline as well.201830253298
745310.9921Long-term application of Swedish sewage sludge on farmland does not cause clear changes in the soil bacterial resistome. The widespread practice of applying sewage sludge to arable land makes use of nutrients indispensable for crops and reduces the need for inorganic fertilizer, however this application also provides a potential route for human exposure to chemical contaminants and microbial pathogens in the sludge. A recent concern is that such practice could promote environmental selection and dissemination of antibiotic resistant bacteria or resistance genes. Understanding the risks of sludge amendment in relation to antibiotic resistance development is important for sustainable agriculture, waste treatment and infectious disease management. To assess such risks, we took advantage of an agricultural field trial in southern Sweden, where land used for growing different crops has been amended with sludge every four years since 1981. We sampled raw, semi-digested and digested and stored sludge together with soils from the experimental plots before and two weeks after the most recent amendment in 2017. Levels of selected antimicrobials and bioavailable metals were determined and microbial effects were evaluated using both culture-independent metagenome sequencing and conventional culturing. Antimicrobials or bioavailable metals (Cu and Zn) did not accumulate to levels of concern for environmental selection of antibiotic resistance, and no coherent signs, neither on short or long time scales, of enrichment of antibiotic-resistant bacteria or resistance genes were found in soils amended with digested and stored sewage sludge in doses up to 12 metric tons per hectare. Likewise, only very few and slight differences in microbial community composition were observed after sludge amendment. Taken together, the current study does not indicate risks of sludge amendment related to antibiotic resistance development under the given conditions. Extrapolations should however be done with care as sludge quality and application practices vary between regions. Hence, the antibiotic concentrations and resistance load of the sludge are likely to be higher in regions with larger antibiotic consumption and resistance burden than Sweden.202032036119
707320.9920Fecal Indicator Bacteria and Antibiotic Resistance Genes in Storm Runoff from Dairy Manure and Compost-Amended Vegetable Plots. Given the presence of antibiotics and resistant bacteria in livestock manures, it is important to identify the key pathways by which land-applied manure-derived soil amendments potentially spread resistance. The goal of this field-scale study was to identify the effects of different types of soil amendments (raw manure from cows treated with cephapirin and pirlimycin, compost from antibiotic-treated or antibiotic-free cows, or chemical fertilizer only) and crop type (lettuce [ L.] or radish [ L.]) on the transport of two antibiotic resistance genes (ARGs; 1 and ) via storm runoff from six naturally occurring storms. Concurrent quantification of sediment and fecal indicator bacteria (FIB; and enterococci) in runoff permitted comparison to traditional agricultural water quality targets that may be driving factors of ARG presence. Storm characteristics (total rainfall volume, storm duration, etc.) significantly influenced FIB concentration (two-way ANOVA, < 0.05), although both effects from individual storm events (Kruskal-Wallis, < 0.05) and vegetative cover influenced sediment levels. Composted and raw manure-amended plots both yielded significantly higher 1 and B levels in runoff for early storms, at least 8 wk following initial planting, relative to fertilizer-only or unamended barren plots. There was no significant difference between 1 or B levels in runoff from plots treated with compost derived from antibiotic-treated versus antibiotic-free dairy cattle. Our findings indicate that agricultural fields receiving manure-derived amendments release higher quantities of these two "indicator" ARGs in runoff, particularly during the early stages of the growing season, and that composting did not reduce effects of ARG loading in runoff.201931589689
655830.9920Does Irrigation with Treated and Untreated Wastewater Increase Antimicrobial Resistance in Soil and Water: A Systematic Review. Population growth and water scarcity necessitate alternative agriculture practices, such as reusing wastewater for irrigation. Domestic wastewater has been used for irrigation for centuries in many historically low-income and arid countries and is becoming more widely used by high-income countries to augment water resources in an increasingly dry climate. Wastewater treatment processes are not fully effective in removing all contaminants, such as antimicrobial resistant bacteria (ARB) and antimicrobial resistance genes (ARGs). Literature reviews on the impact of wastewater irrigation on antimicrobial resistance (AMR) in the environment have been inconclusive and mostly focused on treated wastewater. We conducted the first systematic review to assess the impact of irrigation with both treated or untreated domestic wastewater on ARB and ARGs in soil and adjacent water bodies. We screened titles/abstracts of 3002 articles, out of which 41 were screened in full text and 26 were included in this review. Of these, thirteen investigated irrigation with untreated wastewater, and nine found a positive association with ARB/ARGs in soil. Out of thirteen studies focused on treated wastewater, six found a positive association with ARB/ARGs while six found mixed/negative associations. Our findings demonstrate that irrigation with untreated wastewater increases AMR in soil and call for precautionary action by field workers, their families, and consumers when untreated wastewater is used to irrigate crops. The effect of irrigation with treated wastewater was more variable among the studies included in our review, highlighting the need to better understand to what extent AMR is disseminated through this practice. Future research should assess factors that modify the effect of wastewater irrigation on AMR in soil, such as the degree and type of wastewater treatment, and the duration and intensity of irrigation, to inform guidelines on the reuse of wastewater for irrigation.202134769568
647040.9920The urgent need for risk assessment on the antibiotic resistance spread via sewage sludge land application. Sewage sludge is an ever-increasing by-product of the wastewater treatment process frequently used as a soil fertiliser. To control its quality and prevent any possible hazardous impact of fertilisation, some mandatory limits of heavy metal content have been established by the European Commission (Sewage Sludge Directive). However, since the implementation of the limits, new emerging contaminants have been reported worldwide. Regardless of the wastewater treatment process, sewage sludge contains antibiotics, antibiotic-resistant bacteria and antibiotic resistance genes, which can be released into the environment through its land application. Such a practice may even boost the dissemination and further development of antibiotic resistance phenomenon - already a global problem challenging modern medicine. Due to the growing pharmaceutical pollution in the environment, the time is ripe to assess the risk for the human and environmental health of sewage sludge land application in the context of antibiotic resistance spread. In this review we present the current knowledge in the field and we emphasise the necessity for more studies.201626646979
647350.9920The potential implications of reclaimed wastewater reuse for irrigation on the agricultural environment: The knowns and unknowns of the fate of antibiotics and antibiotic resistant bacteria and resistance genes - A review. The use of reclaimed wastewater (RWW) for the irrigation of crops may result in the continuous exposure of the agricultural environment to antibiotics, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). In recent years, certain evidence indicate that antibiotics and resistance genes may become disseminated in agricultural soils as a result of the amendment with manure and biosolids and irrigation with RWW. Antibiotic residues and other contaminants may undergo sorption/desorption and transformation processes (both biotic and abiotic), and have the potential to affect the soil microbiota. Antibiotics found in the soil pore water (bioavailable fraction) as a result of RWW irrigation may be taken up by crop plants, bioaccumulate within plant tissues and subsequently enter the food webs; potentially resulting in detrimental public health implications. It can be also hypothesized that ARGs can spread among soil and plant-associated bacteria, a fact that may have serious human health implications. The majority of studies dealing with these environmental and social challenges related with the use of RWW for irrigation were conducted under laboratory or using, somehow, controlled conditions. This critical review discusses the state of the art on the fate of antibiotics, ARB and ARGs in agricultural environment where RWW is applied for irrigation. The implications associated with the uptake of antibiotics by plants (uptake mechanisms) and the potential risks to public health are highlighted. Additionally, knowledge gaps as well as challenges and opportunities are addressed, with the aim of boosting future research towards an enhanced understanding of the fate and implications of these contaminants of emerging concern in the agricultural environment. These are key issues in a world where the increasing water scarcity and the continuous appeal of circular economy demand answers for a long-term safe use of RWW for irrigation.201728689129
647460.9920Impact of treated wastewater irrigation on antibiotic resistance in the soil microbiome. The reuse of treated wastewater (TWW) for irrigation is a practical solution for overcoming water scarcity, especially in arid and semiarid regions of the world. However, there are several potential environmental and health-related risks associated with this practice. One such risk stems from the fact that TWW irrigation may increase antibiotic resistance (AR) levels in soil bacteria, potentially contributing to the global propagation of clinical AR. Wastewater treatment plant (WWTP) effluents have been recognized as significant environmental AR reservoirs due to selective pressure generated by antibiotics and other compounds that are frequently detected in effluents. This review summarizes a myriad of recent studies that have assessed the impact of anthropogenic practices on AR in environmental bacterial communities, with specific emphasis on elucidating the potential effects of TWW irrigation on AR in the soil microbiome. Based on the current state of the art, we conclude that contradictory to freshwater environments where WWTP effluent influx tends to expand antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes levels, TWW irrigation does not seem to impact AR levels in the soil microbiome. Although this conclusion is a cause for cautious optimism regarding the future implementation of TWW irrigation, we conclude that further studies aimed at assessing the scope of horizontal gene transfer between effluent-associated ARB and soil bacteria need to be further conducted before ruling out the possible contribution of TWW irrigation to antibiotic-resistant reservoirs in irrigated soils.201323378260
665470.9919Natural recreational waters and the risk that exposure to antibiotic resistant bacteria poses to human health. Antimicrobial resistance (AMR) is widely recognised as a considerable threat to human health, wellbeing and prosperity. Many clinically important antibiotic resistance genes are understood to have originated in the natural environment. However, the complex interactions between humans, animals and the environment makes the health implications of environmental AMR difficult to quantify. This narrative review focuses on the current state of knowledge regarding antibiotic resistant bacteria (ARB) in natural bathing waters and implications for human health. It considers the latest research focusing on the transmission of ARB from bathing waters to humans. The limitations of existing evidence are discussed, as well as research priorities. The authors are of the opinion that future studies should include faecally contaminated bathing waters and people exposed to these environments to accurately parameterise environment-to-human transmission.202234739925
749980.9919Sunlight Photolysis of Extracellular and Intracellular Antibiotic Resistance Genes tetA and sul2 in Photosensitizer-Free Water. Antibiotic resistance genes (ARGs; the genetic material in bacteria that encode for resistance to antibiotics) have been found in the aquatic environment, raising concerns of an environmental transmission route. In an effort to contribute to models predicting the fate of ARGs in the environment-to design control measures, predict health risks, inform ARG surveillance activities, and prioritize policy interventions-and given the importance of sunlight in damaging DNA, we evaluated the sunlight photolysis kinetics of antibiotic-resistant bacteria (ARB) and ARGs under laboratory conditions, focusing on Escherichia coli SMS-3-5 and its ARGs tetA and sul2. Experiments were conducted in the absence of photosensitizers, and ARG decay rates were quantified by quantitative polymerase chain reaction (qPCR) with short and long amplicon targets. Long amplicon qPCR targets quantified greater photolysis rate constants, due to greater ARG coverage. After a lag phase, intracellular ARG had faster decay rates than extracellular ARG, likely due to the contribution of intracellular indirect photolysis processes. Furthermore, all ARG decay rates were significantly slower than those of E. coli. Decay rate constants and quantum yields are presented as foundational work in the development of models to describe the persistence of ARGs in sunlit, environmental waters.202134346694
707590.9919Impact of surface-applied liquid manure on the drainage resistance profile of an agricultural tile-drained clay till field. Dissemination of antibiotic resistance genes (ARGs) in aquatic environments is a concern due to human and animal health. Application of liquid manure on agricultural land is an important source of ARGs, where pathogens, antibiotic-resistant bacteria, and selective agents are released. To improve our understanding of ARGs spreading through soils, our main objective was to evaluate the effectiveness of the soil as a barrier protecting water resources. Over the course of a year, profiles and abundances of ARGs and mobile genetic elements in soil and drainage from an agricultural tile-drained clay till field were investigated upon liquid pig manure application by applying high-throughput quantitative polymerase chain reaction targeting 143 genes. The findings were as follows: (a) 97 genes were detected, where only the transposon gene tnpA-03/ IS6 was shared between the genes detected in drainage and those in acidified liquid manure or fertilized soils, indicating that liquid manure application had a limited impact on the drainage resistance profile; (b) intI1 gene was present in ∼60% of drainage samples in concentrations up to 1,634 intI1 ml(-1) ; and (c) evapotranspiration from barley (Hordeum vulgare L., 'KWS Irina') and a low groundwater table appeared to reduce preferential transport to drainage during the first 3 mo of liquid manure application. Interestingly, the first preferential transport to drainage was observed immediately after the harvest of spring barley. Overall, during the monitoring year we found the soil to be an effective barrier against the spread of fecal ARGs even though the occurrence of the intI1 gene questions the barrier effect from previous years.202235435263
7060100.9918Antibiotic resistance partitioning during on-farm manure separation and high temperature rotary drum composting. Manure application as fertilizer can increase environmental exposure risk, as antibiotics, antibiotic resistance bacteria (ARB), and antibiotic resistant genes (ARGs) can be transmitted to agricultural fields, and adjacent natural systems. Understanding how specific antibiotics and ARGs respond within different manure fractions during on-farm management is limited. The study objective was to conduct a mass flow analysis determining the fate of antibiotic resistance factors (antibiotics, ARGs, and ARB) through solid-liquid separation, with the solid fraction continuing through a bedding recovery unit (BRU) via high temperature rotary composting for use of the manure solids as dairy cow bedding. The results show that most of the manure mass containing the antibiotic resistance factors went untreated following solid-liquid separation, with 95% of the mass leaving the separator as a liquid and pumped to a storage lagoon for field application and 5% proceeding to BRU processing. The tetracyclines and tulathromycin sorbed to the manure solids, while the beta lactams, ampicillin, and benzylpenicilloic acid were only found in the liquid fraction. The removal of antibiotic residuals during the BRU composting was insignificant, yet 40%-73% of the antibiotics were in the liquid fraction. The BRU composting was 100% effective in removing the ARB examined. Five of the eight ARGs (intl1, sul1, tetQ, tetX, and tetM) had significant reduction (>95%) following the BRU composting treatment. While the three other ARGs (tetW, ermB, and bla2) remained constant despite treatment. This study highlighted the importance of examining manure management from a mass balance perspective and understanding antibiotic resistance risk factors.202539617587
3545110.9918Fecal indicators and antibiotic resistance genes exhibit diurnal trends in the Chattahoochee River: Implications for water quality monitoring. Water bodies that serve as sources of drinking or recreational water are routinely monitored for fecal indicator bacteria (FIB) by state and local agencies. Exceedances of monitoring thresholds set by those agencies signal likely elevated human health risk from exposure, but FIB give little information about the potential source of contamination. To improve our understanding of how within-day variation could impact monitoring data interpretation, we conducted a study at two sites along the Chattahoochee River that varied in their recreational usage and adjacent land-use (natural versus urban), collecting samples every 30 min over one 24-h period. We assayed for three types of microbial indicators: FIB (total coliforms and Escherichia coli); human fecal-associated microbial source tracking (MST) markers (crAssphage and HF183/BacR287); and a suite of clinically relevant antibiotic resistance genes (ARGs; blaCTX-M, blaCMY, MCR, KPC, VIM, NDM) and a gene associated with antibiotic resistance (intl1). Mean levels of FIB and clinically relevant ARGs (blaCMY and KPC) were similar across sites, while MST markers and intI1 occurred at higher mean levels at the natural site. The human-associated MST markers positively correlated with antibiotic resistant-associated genes at both sites, but no consistent associations were detected between culturable FIB and any molecular markers. For all microbial indicators, generalized additive mixed models were used to examine diurnal variability and whether this variability was associated with environmental factors (water temperature, turbidity, pH, and sunlight). We found that FIB peaked during morning and early afternoon hours and were not associated with environmental factors. With the exception of HF183/BacR287 at the urban site, molecular MST markers and intI1 exhibited diurnal variability, and water temperature, pH, and turbidity were significantly associated with this variability. For blaCMY and KPC, diurnal variability was present but was not correlated with environmental factors. These results suggest that differences in land use (natural or urban) both adjacent and upstream may impact overall levels of microbial contamination. Monitoring agencies should consider matching sample collection times with peak levels of target microbial indicators, which would be in the morning or early afternoon for the fecal associated indicators. Measuring multiple microbial indicators can lead to clearer interpretations of human health risk associated with exposure to contaminated water.202236439800
6553120.9918Antibiotic 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.202033142796
7431130.9918Antibiotic Resistant Bacteria in Municipal Wastes: Is There Reason for Concern? Recently, there has been increased concern about the presence of antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARG), in treated domestic wastewaters, animal manures and municipal biosolids. The concern is whether these additional sources of ARB contribute to antibiotic resistance levels in the environment, that is, "environmental antibiotic resistance." ARB and ARG occur naturally in soil and water, and it remains unclear whether the introduction of ARB in liquid and solid municipal and animal wastes via land application have any significant impact on the background levels of antibiotic resistance in the environment, and whether they affect human exposure to ARB. In this current review, we examine and re-evaluate the incidence of ARB and ARG resulting from land application activities, and offer a new perspective on the threat of antibiotic resistance to public health via exposure from nonclinical environmental sources. Based on inputs of ARBs and ARGs from land application, their fate in soil due to soil microbial ecology principles, and background indigenous levels of ARBs and ARGs already present in soil, we conclude that while antibiotic resistance levels in soil are increased temporally by land application of wastes, their persistence is not guaranteed and is in fact variable, and often contradictory based on application site. Furthermore, the application of wastes may not produce the most direct impact of ARGs and ARB on public health. Further investigation is still warranted in agriculture and public health, including continued scrutiny of antibiotic use in both sectors.201829505255
6688140.9918Antibiotic resistant bacteria: A bibliometric review of literature. Antibiotic-resistant bacteria (ARB) are a serious threat to the health of people and the ecological environment. With this problem becoming more and more serious, more countries made research on the ARB, and the research number has been sharply increased particularly over the past decade. Therefore, it is quite necessary to globally retrace relevant researches on the ARB published from 2010 to 2020. This will help researchers to understand the current research situation, research trends and research hotspots in this field. This paper uses bibliometrics to examine publications in the field of ARB from 2010 to 2020 that were retrieved from the Web of Science (WOS). Our study performed a statistical analysis of the countries, institutions, journals, authors, research areas, author keywords, Essential Science Indicators (ESI) highly cited papers, and ESI hotspots papers to provide an overview of the ARB field as well as research trends, research hotspots, and future research directions in the field. The results showed that the number of related studies is increasing year by year; the USA is most published in the field of ARB; China is the most active in this field in the recent years; the Chinese Acad Sci published the most articles; Sci. Total Environ. published the greatest number of articles; CM Manaia has the most contributions; Environmental Sciences and Ecology is the most popular research area; and "antibiotic resistance," "antibiotics," and "antibiotic resistance genes" were the most frequently occurring author keywords. A citation analysis showed that aquatic environment-related antibiotic resistance is a key research area in this field, while antimicrobial nanomaterial-related research is a recent popular topic.202236466520
7063150.9918Impact of dairy manure pre-application treatment on manure composition, soil dynamics of antibiotic resistance genes, and abundance of antibiotic-resistance genes on vegetables at harvest. Manuring ground used for crop production is an important agricultural practice. Should antibiotic-resistant enteric bacteria carried in the manure be transferred to crops that are consumed raw, their consumption by humans or animals will represent a route of exposure to antibiotic resistance genes. Treatment of manures prior to land application is a potential management option to reduce the abundance of antibiotic resistance genes entrained with manure application. In this study, dairy manure that was untreated, anaerobically digested, mechanically dewatered or composted was applied to field plots that were then cropped to lettuce, carrots and radishes. The impact of treatment on manure composition, persistence of antibiotic resistance gene targets in soil following application, and distribution of antibiotic resistance genes and bacteria on vegetables at harvest was determined. Composted manure had the lowest abundance of antibiotic resistance gene targets compared to the other manures. There was no significant difference in the persistence characteristics of antibiotic resistance genes following land application of the various manures. Compared to unmanured soil, antibiotic resistance genes were detected more frequently in soil receiving raw or digested manure, whereas they were not in soil receiving composted manure. The present study suggests that vegetables grown in ground receiving raw or digested manure are at risk of contamination with manure-borne antibiotic resistant bacteria, whereas vegetables grown in ground receiving composted manure are less so.201728076772
6407160.9918Urban wastewater treatment plants as hotspots for antibiotic resistant bacteria and genes spread into the environment: a review. Urban wastewater treatment plants (UWTPs) are among the main sources of antibiotics' release into the environment. The occurrence of antibiotics may promote the selection of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB), which shade health risks to humans and animals. In this paper the fate of ARB and ARGs in UWTPs, focusing on different processes/technologies (i.e., biological processes, advanced treatment technologies and disinfection), was critically reviewed. The mechanisms by which biological processes influence the development/selection of ARB and ARGs transfer are still poorly understood. Advanced treatment technologies and disinfection process are regarded as a major tool to control the spread of ARB into the environment. In spite of intense efforts made over the last years to bring solutions to control antibiotic resistance spread in the environment, there are still important gaps to fill in. In particular, it is important to: (i) improve risk assessment studies in order to allow accurate estimates about the maximal abundance of ARB in UWTPs effluents that would not pose risks for human and environmental health; (ii) understand the factors and mechanisms that drive antibiotic resistance maintenance and selection in wastewater habitats. The final objective is to implement wastewater treatment technologies capable of assuring the production of UWTPs effluents with an acceptable level of ARB.201323396083
6582170.9918Effective Treatment Strategies for the Removal of Antibiotic-Resistant Bacteria, Antibiotic-Resistance Genes, and Antibiotic Residues in the Effluent From Wastewater Treatment Plants Receiving Municipal, Hospital, and Domestic Wastewater: Protocol for a Systematic Review. BACKGROUND: The widespread and unrestricted use of antibiotics has led to the emergence and spread of antibiotic-resistant bacteria (ARB), antibiotic-resistance genes (ARGs), and antibiotic residues in the environment. Conventional wastewater treatment plants (WWTPs) are not designed for effective and adequate removal of ARB, ARGs, and antibiotic residues, and therefore, they play an important role in the dissemination of antimicrobial resistance (AMR) in the natural environment. OBJECTIVE: We will conduct a systematic review to determine the most effective treatment strategies for the removal of ARB, ARGs, and antibiotic residues from the treated effluent disposed into the environment from WWTPs that receive municipal, hospital, and domestic discharge. METHODS: We will search the MEDLINE, EMBASE, Web of Science, World Health Organization Global Index Medicus, and ProQuest Environmental Science Collection databases for full-text peer-reviewed journal articles published between January 2001 and December 2020. We will select only articles published in the English language. We will include studies that measured (1) the presence, concentration, and removal rate of ARB/ARGs going from WWTP influent to effluent, (2) the presence, concentration, and types of antibiotics in the effluent, and (3) the possible selection of ARB in the effluent after undergoing treatment processes in WWTPs. At least two independent reviewers will extract data and perform risk of bias assessment. An acceptable or narrative synthesis method will be followed to synthesize the data and present descriptive characteristics of the included studies in a tabular form. The study has been approved by the Ethics Review Board at the International Centre for Diarrhoeal Disease Research, Bangladesh (protocol number: PR-20113). RESULTS: This protocol outlines our proposed methodology for conducting a systematic review. Our results will provide an update to the existing literature by searching additional databases. CONCLUSIONS: Findings from our systematic review will inform the planning of proper treatment methods that can effectively reduce the levels of ARB, ARGs, and residual antibiotics in effluent, thus lowering the risk of the environmental spread of AMR and its further transmission to humans and animals. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/33365.202134842550
6472180.9918Balancing water sustainability and public health goals in the face of growing concerns about antibiotic resistance. Global initiatives are underway to advance the sustainability of urban water infrastructure through measures such as water reuse. However, there are growing concerns that wastewater effluents are enriched in antibiotics, antibiotic resistant bacteria, and antibiotic resistance genes, and thus could serve as a contributing factor to growing rates of antibiotic resistance in human infections. Evidence for the role of the water environment as a source and pathway for the spread of antimicrobial resistance is examined and key knowledge gaps are identified with respect to implications for sustainable water systems. Efforts on the part of engineers along with investment in research in epidemiology, risk assessment, water treatment and water delivery could advance current and future sustainable water strategies and help avoid unintended consequences.201424279909
7295190.9917Dissemination of antibiotic resistance in receiving environments under a changing climate: A modeling exercise. Antibiotic resistance in rivers has become a global problem, particularly due to the discharge of wastewater treatment plant (WWTP) effluents into these systems. These effluents contain residual antibiotics, antibiotic-resistance genes (ARGs), and antibiotic-resistant bacteria (ARB). While watershed-scale models are commonly used to address other water quality issues, they have not typically been used to address antibiotic resistance. In this study, we present a new model called SWAT-ARB (SWAT- Antibiotic-Resistant Bacteria) that can simulate antibiotic resistance in E. coli at the watershed scale. SWAT-ARB is an adaptation of the widely-used SWAT (Soil and Water Assessment Tool) model, which is a physically-based, watershed-scale hydrological model. We used SWAT-ARB to study the receiving environments of WWTPs in the Adyar River basin in India, Crab Creek in the United States, and the Upper Viskan basin in Sweden. We analyzed the simulations of resistant fractions (the ratio of resistant E. coli concentration to total E. coli concentration) in the streamflow at different flow levels. We also examined the long-term trends of resistant fractions to understand how rising temperatures may impact resistance. We found that in the Adyar and Crab Creek basins, the resistant fractions were largely influenced by temperature rather than flow and wash-off processes, while in the Upper Viskan basin, the resistant fractions were affected by both temperature and flow conditions. In a simulation where we only increased temperatures by 2 °C in the bacteria sub-routine, we found that the Adyar basin showed a decrease in resistant fractions of up to 17 % in dry conditions, while Crab Creek showed increases of 17.5-24.1 % and Upper Viskan showed increases of 4.6-33.5 % across flow classes. Under future climate scenarios (SSP 2-4.5 and SSP 5-8.5), Adyar's resistant fractions decreased by up to 55.5 % as temperatures approached the bacterial growth inhibition threshold, while Crab Creek's resistant fractions increased by up to 175 % as temperatures remained within the optimal 10-20 °C growth range. Our results suggest that the SWAT-ARB model could be further improved by incorporating temperature-dependent parameters into the resistance simulation component.202540743959