Overgrowth control of potentially hazardous bacteria during storage of ozone treated wastewater through natural competition. - Related Documents




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744601.0000Overgrowth control of potentially hazardous bacteria during storage of ozone treated wastewater through natural competition. Improving the chemical and biological quality of treated wastewater is particularly important in world regions under water stress. In these regions, reutilization of wastewater is seen as an alternative to reduce water demand, particularly for agriculture irrigation. In a reuse scenario, the treated wastewater must have enough quality to avoid chemical and biological contamination of the receiving environment. Ozonation is among the technologies available to efficiently remove organic micropollutants and disinfect secondary effluents, being implemented in full-scale urban wastewater treatment plants worldwide. However, previous studies demonstrated that storage of ozone treated wastewater promoted the overgrowth of potentially harmful bacteria, putting at risk its reutilization, given for instance the possibility of contaminating the food-chain. Therefore, this study was designed to assess the potential beneficial role of inoculation of ozone treated wastewater with a diverse bacterial community during storage, for the control of the overgrowth of potentially hazardous bacteria, through bacterial competition. To achieve this goal, ozone treated wastewater (TWW) was diluted with river water (RW) in the same proportion, and the resulting bacterial community (RW+TWW) was compared to that of undiluted TWW over 7 days storage. As hypothesized, in contrast to TWW, where dominance of Beta- and Gammaproteobacteria, namely Pseudomonas spp. and Acinetobacter spp., was observed upon storage for 7 days, the bacterial communities of the diluted samples (RW+TWW) were diverse, resembling those of RW. Moreover, given the high abundance of antibiotic resistance genes in RW, the concentration of these genes in RW+TWW did not differ from that of the non-ozonated controls (WW, RW and RW+WW) over the storage period. These results highlight the necessity of finding a suitable pristine diverse bacterial community to be used in the future to compete with bacteria surviving ozonation, to prevent reactivation of undesirable bacteria during storage of treated wastewater.202234902759
745210.9998Elevation of antibiotic resistance genes at cold temperatures: implications for winter storage of sludge and biosolids. Prior research suggests that cold temperatures may stimulate the proliferation of certain antibiotic resistance genes (ARGs) and gene transfer elements during storage of biosolids. This could have important implications on cold weather storage of biosolids, as often required in northern climates until a time suitable for land application. In this study, levels of an integron-associated gene (intI1) and an ARG (sul1) were monitored in biosolids subject to storage at 4, 10 and 20°C. Both intI1 and sul1 were observed to increase during short-term storage (<2 months), but the concentrations returned to background within 4 months. The increases in concentration were more pronounced at lower temperatures than ambient temperatures. Overall, the results suggest that cold stress may induce horizontal gene transfer of integron-associated ARGs and that biosolids storage conditions should be considered prior to land application. SIGNIFICANCE AND IMPACT OF THE STUDY: Wastewater treatment plants have been identified as the hot spots for the proliferation and dissemination of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) to the environment through discharge of treated effluent to water bodies as well as application of biosolids to land. Identifying critical control points within the treatment process may aid in the development of solutions for the reduction of ARGs and ARB and curbing the spread of antibiotic resistance. This study found increases in ARGs during biosolids storage and identifies changes in operational protocols that could help reduce ARG loading to the environment when biosolids are land-applied.201425196177
744820.9998Performance of a constructed wetland in Grand Marais, Manitoba, Canada: Removal of nutrients, pharmaceuticals, and antibiotic resistance genes from municipal wastewater. BACKGROUND: The discharge of complex mixtures of nutrients, organic micropollutants, and antibiotic resistance genes from treated municipal wastewater into freshwater systems are global concerns for human health and aquatic organisms. Antibiotic resistance genes (ARGs) are genes that have the ability to impart resistance to antibiotics and reduce the efficacy of antibiotics in the systems in which they are found. In the rural community of Grand Marais, Manitoba, Canada, wastewater is treated passively in a sewage lagoon prior to passage through a treatment wetland and subsequent release into surface waters. Using this facility as a model system for the Canadian Prairies, the two aims of this study were to assess: (a) the presence of nutrients, micropollutants (i.e., pesticides, pharmaceuticals), and ARGs in lagoon outputs, and (b) their potential removal by the treatment wetland prior to release to surface waters in 2012. RESULTS: As expected, concentrations of nitrogen and phosphorus species were greatest in the lagoon and declined with movement through the wetland treatment system. Pharmaceutical and agricultural chemicals were detected at concentrations in the ng/L range. Concentrations of these compounds spiked downstream of the lagoon following discharge and attenuation was observed as the effluent migrated through the wetland system. Hazard quotients calculated for micropollutants of interest indicated minimal toxicological risk to aquatic biota, and results suggest that the wetland attenuated atrazine and carbamazepine significantly. There was no significant targeted removal of ARGs in the wetland and our data suggest that the bacterial population in this system may have genes imparting antibiotic resistance. CONCLUSIONS: The results of this study indicate that while the treatment wetland may effectively attenuate excess nutrients and remove some micropollutants and bacteria, it does not specifically target ARGs for removal. Additional studies would be beneficial to determine whether upgrades to extend retention time or alter plant community structure within the wetland would optimize removal of micropollutants and ARGs to fully characterize the utility of these systems on the Canadian Prairies.201323506187
737830.9998Role of endogenous soil microorganisms in controlling antimicrobial resistance after the exposure to treated wastewater. The reuse of treated wastewater (TWW) for irrigation appears to be a relevant solution to the challenges of growing water demand and scarcity. However, TWW contains not only micro-pollutants including pharmaceutical residues but also antibiotic resistant bacteria. The reuse of TWW could contribute to the dissemination of antimicrobial resistance in the environment. The purpose of this study was to assess if exogenous bacteria from irrigation waters (TWW or tap water-TP) affect endogenous soil microbial communities (from 2 soils with distinct irrigation history) and key antibiotic resistance gene sul1 and mobile genetic elements intl1 and IS613. Experiments were conducted in microcosms, irrigated in one-shot, and monitored for three months. Results showed that TP or TWW exposure induced a dynamic response of soil microbial communities but with no significant increase of resistance and mobile gene abundances. However, no significant differences were observed between the two water types in the current experimental design. Despite this, the 16S rDNA analysis of the two soils irrigated for two years either with tap water or TWW resulted in soil microbial community differentiation and the identification of biomarkers from Xanthomonadaceae and Planctomycetes families for soils irrigated with TWW. Low-diversity soils were more sensitive to the addition of TWW. Indeed, TWW exposure stimulated the growth of bacterial genera known to be pathogenic, correlating with a sharp increase in the copy number of selected resistance genes (up to 3 logs). These low-diversity soils could thus enable the establishment of exogenous bacteria from TWW which was not observed with native soils. In particular, the emergence of Planctomyces, previously suggested as a biomarker of soil irrigated by TWW, was here demonstrated. Finally, this study showed that water input frequency, initial soil microbial diversity and soil history drive changes within soil endogenous communities and the antibiotic resistance gene pool.202438703836
742540.9997Antibiotic resistant bacteria and genes in wastewater treatment plants: From occurrence to treatment strategies. This study aims to discuss the following: (1) occurrence and proliferation of antibiotic resistance in wastewater treatment plants (WWTPs); (2) factors influencing antibiotic resistance bacteria and genes in WWTPs; (3) tools to assess antibiotic resistance in WWTPs; (4) environmental contamination of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from WWTPs; (5) effects of ARB and ARGs from WWTPs on human health; and (6) treatment strategies. In general, resistant and multi-resistant bacteria, including Enterobacteriaceae, Pseudomonas aeruginosa, and Escherichia coli, exist in various processes of WWTPs. The existence of ARB and ARGs results from the high concentration of antibiotics in wastewater, which promote selective pressures on the local bacteria present in WWTPs. Thus, improving wastewater treatment technology and avoiding the misuse of antibiotics is critical to overcoming the threat of proliferation of ARBs and ARGs. Numerous factors can affect the development of ARB and ARGs in WWTPs. Abiotic factors can affect the bacterial community dynamics, thereby, affecting the applicability of ARB during the wastewater treatment process. Furthermore, the organic loads and other nutrients influence bacterial survival and growth. Specifically, molecular methods for the rapid characterization and detection of ARBs or their genes comprise DNA sequencing, real-time PCR, simple and multiplex PCR, and hybridization-based technologies, including micro- and macro-arrays. The reuse of effluent from WWTPs for irrigation is an efficient method to overcome water scarcity. However, there are also some potential environmental risks associated with this practice, such as increase in the levels of antibiotic resistance in the soil microbiome. Human mortality rates may significantly increase, as ARB can lead to resistance among several types of antibiotics or longer treatment times. Some treatment technologies, such as anaerobic and aerobic treatment, coagulation, membrane bioreactors, and disinfection processes, are considered potential techniques to restrict antibiotic resistance in the environment.202235679932
649450.9997Performance Efficiency of Conventional Treatment Plants and Constructed Wetlands towards Reduction of Antibiotic Resistance. Domestic and industrial wastewater discharges harbor rich bacterial communities, including both pathogenic and commensal organisms that are antibiotic-resistant (AR). AR pathogens pose a potential threat to human and animal health. In wastewater treatment plants (WWTP), bacteria encounter environments suitable for horizontal gene transfer, providing an opportunity for bacterial cells to acquire new antibiotic-resistant genes. With many entry points to environmental components, especially water and soil, WWTPs are considered a critical control point for antibiotic resistance. The primary and secondary units of conventional WWTPs are not designed for the reduction of resistant microbes. Constructed wetlands (CWs) are viable wastewater treatment options with the potential for mitigating AR bacteria, their genes, pathogens, and general pollutants. Encouraging performance for the removal of AR (2-4 logs) has highlighted the applicability of CW on fields. Their low cost of construction, operation and maintenance makes them well suited for applications across the globe, especially in developing and low-income countries. The present review highlights a better understanding of the performance efficiency of conventional treatment plants and CWs for the elimination/reduction of AR from wastewater. They are viable alternatives that can be used for secondary/tertiary treatment or effluent polishing in combination with WWTP or in a decentralized manner.202235052991
744760.9997Holistic approach to chemical and microbiological quality of aquatic ecosystems impacted by wastewater effluent discharges. Wastewater treatment plants (WWTPs) collect wastewater from various sources and use different treatment processes to reduce the load of pollutants in the environment. Since the removal of many chemical pollutants and bacteria by WWTPs is incomplete, they constitute a potential source of contaminants. The continuous release of contaminants through WWTP effluents can compromise the health of the aquatic ecosystems, even if they occur at very low concentrations. The main objective of this work was to characterize, over a period of four months, the treatment steps starting from income to the effluent and 5 km downstream to the receiving river. In this context, the efficiency removal of chemical pollutants (e.g. hormones and pharmaceuticals, including antibiotics) and bacteria was assessed in a WWTP case study by using a holistic approach. It embraces different chemical and biological-based methods, such as pharmaceutical analysis by HPLC-MSMS, growth rate inhibition in algae, ligand binding estrogen receptor assay, microbial community study by 16S and shotgun sequencing along with relative quantification of resistance genes by quantitative polymerase chain reaction. Although both, chemical and biological-based methods showed a significant reduction of the pollutant burden in effluent and surface waters compared to the influent of the WWTP, no complete removal of pollutants, pathogens and antibiotic resistance genes was observed.202235489490
745370.9997Long-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
649380.9997Antibiotic microbial resistance (AMR) removal efficiencies by conventional and advanced wastewater treatment processes: A review. The World Health Organization (WHO) has identified the spread of antibiotic resistance as one of the major risks to global public health. An important transfer route into the aquatic environment is the urban water cycle. In this paper the occurrence and transport of antibiotic microbial resistance in the urban water cycle are critically reviewed. The presence of antibiotic resistance in low impacted surface water is being discussed to determine background antibiotic resistance levels, which might serve as a reference for treatment targets in the absence of health-based threshold levels. Different biological, physical and disinfection/oxidation processes employed in wastewater treatment and their efficacy regarding their removal of antibiotic resistant bacteria and antibiotic resistance geness (ARGs) were evaluated. A more efficient removal of antibiotic microbial resistance abundances from wastewater effluents can be achieved by advanced treatment processes, including membrane filtration, ozonation, UV-irradiation or chlorination, to levels typically observed in urban surface water or low impacted surface water.201931195321
739290.9997Distribution of genetic elements associated with antibiotic resistance in treated and untreated animal husbandry waste and wastewater. Animal breeding for meat production based on swine, cattle, poultry, and aquaculture is an activity that generates several impacts on the environment, among them the spread of antibiotic resistance. There is a worldwide concern related to the massive use of antibiotics, which causes selective pressure on the microbial community, triggering bacteria that contain "antibiotic resistance genes." According to the survey here presented, antibiotic resistance-related genes such as tetracyclines (tet), erythromycin (erm), and sulfonamides (sul), as well as the genetic mobile element interferon (int), are the most reported genetic elements in qualitative and quantitative studies of swine, cattle, poultry, and aquaculture manure/wastewater. It has been observed that biological treatments based on waste composting and anaerobic digestion are effective in ARG removal, particularly for tet, bla, erm, and qnr (quinolone) genes. On the other hand, sul and intI genes were more persistent in such treatments. Tertiary treatments, such advanced oxidative processes, are suitable strategies to improve ARG reduction. In general temperature, hydraulic retention time, and penetration of sunlight are the main operational parameters for ARG reduction in treatments applied to animal waste, and therefore attention should be addressed to optimize their efficacy regarding ARG removal. Despite being reduced, the presence of ARG in treated effluents and in biosolids indicates that there is a potential risk of antibiotic resistance spread in nature, especially through the release of treated livestock waste into the environment.202133835340
7431100.9997Antibiotic 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
7514110.9997Early and differential bacterial colonization on microplastics deployed into the effluents of wastewater treatment plants. Microbial colonization of microplastics (MPs) in aquatic ecosystems is a well-known phenomenon; however, there is insufficient knowledge of the early colonization phase. Wastewater treatment plant (WWTP) effluents have been proposed as important pathways for MPs entry and transport in aquatic environments and are hotspots of bacterial pathogens and antibiotic resistance genes (ARGs). This study aimed at characterizing bacterial communities in the early stage of biofilm formation on seven different types of MPs deployed in two different WWTPs effluents as well as measuring the relative abundance of two ARGs (sulI and tetM) on the tested MPs. Illumina Miseq sequencing of the 16S rRNA showed significant higher diversity of bacteria on MPs in comparison with free-living bacteria in the WWTP effluents. β-diversity analysis showed that the in situ environment (sampling site) and hydrophobicity, to a lesser extent, had a role in the early bacterial colonization phase. An early colonization phase MPs-core microbiome could be identified. Furthermore, specific core microbiomes for each type of polymer suggested that each type might select early attachment of bacteria. Although the tested WWTP effluent waters contained antibiotic resistant bacteria (ARBs) harboring the sulI and tetM ARGs, MPs concentrated ARBs harboring the sulI gene but not tetM. These results highlight the relevance of the early attachment phase in the development of bacterial biofilms on different types of MP polymers and the role that different types of polymers might have facilitating the attachment of specific bacteria, some of which might carry ARGs.202133246729
6495120.9997A Review on Occurrence and Spread of Antibiotic Resistance in Wastewaters and in Wastewater Treatment Plants: Mechanisms and Perspectives. This paper reviews current knowledge on sources, spread and removal mechanisms of antibiotic resistance genes (ARGs) in microbial communities of wastewaters, treatment plants and downstream recipients. Antibiotic is the most important tool to cure bacterial infections in humans and animals. The over- and misuse of antibiotics have played a major role in the development, spread, and prevalence of antibiotic resistance (AR) in the microbiomes of humans and animals, and microbial ecosystems worldwide. AR can be transferred and spread amongst bacteria via intra- and interspecies horizontal gene transfer (HGT). Wastewater treatment plants (WWTPs) receive wastewater containing an enormous variety of pollutants, including antibiotics, and chemicals from different sources. They contain large and diverse communities of microorganisms and provide a favorable environment for the spread and reproduction of AR. Existing WWTPs are not designed to remove micropollutants, antibiotic resistant bacteria (ARB) and ARGs, which therefore remain present in the effluent. Studies have shown that raw and treated wastewaters carry a higher amount of ARB in comparison to surface water, and such reports have led to further studies on more advanced treatment processes. This review summarizes what is known about AR removal efficiencies of different wastewater treatment methods, and it shows the variations among different methods. Results vary, but the trend is that conventional activated sludge treatment, with aerobic and/or anaerobic reactors alone or in series, followed by advanced post treatment methods like UV, ozonation, and oxidation removes considerably more ARGs and ARB than activated sludge treatment alone. In addition to AR levels in treated wastewater, it examines AR levels in biosolids, settled by-product from wastewater treatment, and discusses AR removal efficiency of different biosolids treatment procedures. Finally, it puts forward key-points and suggestions for dealing with and preventing further increase of AR in WWTPs and other aquatic environments, together with a discussion on the use of mathematical models to quantify and simulate the spread of ARGs in WWTPs. Mathematical models already play a role in the analysis and development of WWTPs, but they do not consider AR and challenges remain before models can be used to reliably study the dynamics and reduction of AR in such systems.202134707579
7377130.9997Impact of treated wastewater irrigation on antibiotic resistance in agricultural soils. Antibiotic resistance (AR) is a global phenomenon with severe epidemiological ramifications. Anthropogenically impacted natural aquatic and terrestrial environments can serve as reservoirs of antibiotic resistance genes (ARG), which can be horizontally transferred to human-associated bacteria through water and food webs, and thus contribute to AR proliferation. Treated-wastewater (TWW) irrigation is becoming increasingly prevalent in arid regions of the world, due to growing demand and decline in freshwater supplies. The release of residual antibiotic compounds, AR bacteria, and ARGs from wastewater effluent may result in proliferation of AR in irrigated soil microcosms. The aim of this study was to assess the impact of TWW-irrigation on soil AR bacterial and ARG reservoirs. Tetracycline, erythromycin, sulfonamide, and ciprofloxacin resistance in soil was assessed using standard culture-based isolation methods and culture-independent molecular analysis using quantitative real-time PCR (qPCR). High levels of bacterial antibiotic resistance were detected in both freshwater- and TWW-irrigated soils. Nonetheless, in most of the soils analyzed, AR bacteria and ARG levels in TWW-irrigated soils were on the whole identical (or sometimes even lower) than in the freshwater-irrigated soils, indicating that the high number of resistant bacteria that enter the soils from the TWW are not able to compete or survive in the soil environment and that they do not significantly contribute ARG to soil bacteria. This strongly suggests that the impact of the TWW-associated bacteria on the soil microbiome is on the whole negligible, and that the high levels of AR bacteria and ARGs in both the freshwater- and the TWW-irrigated soils are indicative of native AR associated with the natural soil microbiome.201222494147
7067140.9997Impact of the antibiotic doxycycline on the D. magna reproduction, associated microbiome and antibiotic resistance genes in treated wastewater conditions. Wastewater Treatment Plant (WWTP) effluents are important sources of antibiotics, antibiotic resistance genes (ARGs) and resistant bacteria that threaten aquatic biota and human heath. Antibiotic effects on host-associated microbiomes, spread of ARGs and the consequences for host health are still poorly described. This study investigated changes of the Daphnia magna associated microbiome exposed to the recalcitrant antibiotic doxycycline under artificial reconstituted lab water media (lab water) and treated wastewater media. D. magna individual juveniles were exposed for 10 days to treated wastewater with and without doxycycline, and similarly in lab water. We analysed 16 S rRNA gene sequences to assess changes in community structure, monitored Daphnia offspring production and quantified ARGs abundances by qPCR from both Daphnia and water (before and after the exposure). Results showed that doxycycline and media (lab water or wastewater) had a significant effect modulating Daphnia-associated microbiome composition and one of the most discriminant taxa was Enterococcus spp. Moreover, in lab water, doxycycline reduced the presence of Limnohabitans sp., which are dominant bacteria of the D. magna-associated microbiome and impaired Daphnia reproduction. Contrarily, treated wastewater increased diversity and richness of Daphnia-associated microbiome and promoted fecundity. In addition, the detected ARG genes in both lab water and treated wastewater medium included the qnrS1, sul1, and bla(TEM,) and the integron-related intI1 gene. The treated wastewater contained about 10 times more ARGs than lab water alone. Furthermore, there was an increase of sul1 in Daphnia cultured in treated wastewater compared to lab water. In addition, there were signs of a higher biodegradation of doxycycline by microbiomes of treated wastewater in comparison to lab water. Thus, results suggest that Daphnia-associated microbiomes are influenced by their environment, and that bacterial communities present in treated wastewater are better suited to cope with the effects of antibiotics.202337442322
7454150.9997Invited review: Fate of antibiotic residues, antibiotic-resistant bacteria, and antibiotic resistance genes in US dairy manure management systems. United States dairy operations use antibiotics (primarily β-lactams and tetracyclines) to manage bacterial diseases in dairy cattle. Antibiotic residues, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARG) can be found in dairy manure and may contribute to the spread of antibiotic resistance (AR). Although β-lactam residues are rarely detected in dairy manure, tetracycline residues are common and perhaps persistent. Generally, <15% of bacterial pathogen dairy manure isolates are ARB, although resistance to some antibiotics (e.g., tetracycline) can be higher. Based on available data, the prevalence of medically important ARB on dairy operations is generally static or may be declining for antibiotic-resistant Staphylococcus spp. Over 60 ARG can be found in dairy manure (including β-lactam and tetracycline resistance genes), although correlations with antibiotic usage, residues, and ARB have been inconsistent, possibly because of sampling and analytical limitations. Manure treatment systems have not been specifically designed to mitigate AR, though certain treatments have some capacity to do so. Generally, well-managed aerobic compost treatments reaching higher peak temperatures (>60°C) are more effective at mitigating antibiotic residues than static stockpiles, although this depends on the antibiotic residue and their interactions. Similarly, thermophilic anaerobic digesters operating under steady-state conditions may be more effective at mitigating antibiotic residues than mesophilic or irregularly operated digesters or anaerobic lagoons. The number of ARB may decline during composting and digestion or be enriched as the bacterial communities in these systems shift, affecting relative ARG abundance or acquire ARG during treatment. Antibiotic resistance genes often persist through these systems, although optimal management and higher operating temperature may facilitate their mitigation. Less is known about other manure treatments, although separation technologies may be unique in their ability to partition antibiotic residues based on sorption and solubility properties. Needed areas of study include determining natural levels of AR in dairy systems, standardizing and optimizing analytical techniques, and more studies of operating on-farm systems, so that treatment system performance and actual human health risks associated with levels of antibiotic residues, ARB, and ARG found in dairy manure can be accurately assessed.202031837779
7610160.9997Coagulation promotes the spread of antibiotic resistance genes in secondary effluents. Wastewater treatment plants (WWTPs) are biological hotspots receiving the residual antibiotics and antibiotic resistant bacteria/genes (ARB/ARGs) that greatly influence the spread of antibiotic resistance in the environment. A common method used in WWTPs for the purification of secondary effluent is coagulation. Notwithstanding the increasing health concern of antibiotic resistance in WWTPs, the impact of coagulation on the emergence and spread of antibiotic resistance remains unclear. To shed light on this, our study investigated the behavior of four representative ARB types (tetracycline, sulfamethoxazole, clindamycin, and ciprofloxacin resistance) during the coagulation process in a model wastewater treatment plant. Our search showed a significant reduction in the presence of ARBs after either PAC or FeCl(3) coagulation, with removal efficiencies of 95% and 90%, respectively. However, after 4 days of storage, ARB levels in the coagulated effluent increased by 6-138 times higher than the original secondary effluent. It suggests a potential resurgence and spread of antibiotic resistance after coagulation. Detailed studies suggest that coagulants, particularly PAC, may facilitate the transfer of ARGs among different bacterial species by the enhanced cell-cell contact during coagulation-induced bacterial aggregation. This transfer is further enhanced by the factors such as auxiliary mixing, longer incubation time and ideal operating temperatures. In addition, both PAC and FeCl(3) affected gene expression associated with bacterial conjugation, leading to an increase in conjugation efficiency. In conclusion, while coagulation serves as a purification method, it might inadvertently boost the spread of ARGs during tertiary wastewater treatment. This underscores the importance of implementing subsequent measures to mitigate this effect. Our findings provide a deeper understanding of the challenges posed by bacterial antibiotic resistance in wastewater and pave the way for devising more effective ARB and ARG management strategies.202438810683
6408170.9997Antibiotic resistance in wastewater treatment plants: Tackling the black box. Wastewater is among the most important reservoirs of antibiotic resistance in urban environments. The abundance of carbon sources and other nutrients, a variety of possible electron acceptors such as oxygen or nitrate, the presence of particles onto which bacteria can adsorb, or a fairly stable pH and temperature are examples of conditions favouring the remarkable diversity of microorganisms in this peculiar habitat. The wastewater microbiome brings together bacteria of environmental, human and animal origins, many harbouring antibiotic resistance genes (ARGs). Although numerous factors contribute, mostly in a complex interplay, for shaping this microbiome, the effect of specific potential selective pressures such as antimicrobial residues or metals, is supposedly determinant to dictate the fate of antibiotic resistant bacteria (ARB) and ARGs during wastewater treatment. This paper aims to enrich the discussion on the ecology of ARB&ARGs in urban wastewater treatment plants (UWTPs), intending to serve as a guide for wastewater engineers or other professionals, who may be interested in studying or optimizing the wastewater treatment for the removal of ARB&ARGs. Fitting this aim, the paper overviews and discusses: i) aspects of the complexity of the wastewater system and/or treatment that may affect the fate of ARB&ARGs; ii) methods that can be used to explore the resistome, meaning the whole ARB&ARGs, in wastewater habitats; and iii) some frequently asked questions for which are proposed addressing modes. The paper aims at contributing to explore how ARB&ARGs behave in UWTPs having in mind that each plant is a unique system that will probably need a specific procedure to maximize ARB&ARGs removal.201829626693
7455180.9997Lagoon, Anaerobic Digestion, and Composting of Animal Manure Treatments Impact on Tetracycline Resistance Genes. Increased demand for animal protein is met by increased food animal production resulting in large quantities of manure. Animal producers, therefore, need sustainable agricultural practices to protect environmental health. Large quantities of antimicrobials are used in commercial food animal production. Consequently, antimicrobial-resistant bacteria and the resistance genes emerge and are excreted through feces. Manure management is essential for the safe disposal of animal waste. Lagoons, with or without covers, and anaerobic digesters, with the primary purpose of methane production, and composting, with the primary purpose of producing organic fertilizer, are widely used methods of manure treatment. We reviewed manure management practices and their impact on tetracycline resistance genes. Lagoons are maintained at ambient temperatures; especially uncovered lagoons are the least effective in removing tetracycline resistance genes. However, some modifications can improve the performance of lagoons: sequential use of uncovered lagoons and the use of covered lagoons resulted in a one-log reduction, while post-treatments such as biofiltration following covered lagoon treatment resulted in 3.4 log reduction. Mesophilic digestion of animal manure did not have any significant effect; only a 0.7 log reduction in tet(A) was observed in one study. While thermophilic anaerobic digesters are effective, if properly operated, they are expensive for animal producers. Aerobic thermophilic composting is a promising technology if optimized with its economic benefits. Composting of raw animal manure can result in up to a 2.5 log reduction, and postdigestion composting can reduce tetracycline resistance gene concentration by >80%. In general, manure management was not designed to mitigate antimicrobial resistance; future research is needed to optimize the economic benefits of biogas or organic fertilizer on the one hand and for the mitigation of foodborne pathogens and antimicrobial resistance on the other.202235326854
7424190.9997Fate of antibiotic resistance genes and antibiotic-resistant bacteria in water resource recovery facilities. Many important diseases are showing resistance to commonly used antibiotics, and the resistance is potentially caused by widespread use of antibiotics for maintaining human health and improving food production. Antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) are associated with this increase, and their fate in water resource recovery facilities is an important, emerging area of research. This literature review summarizes current findings of worldwide research on the fate of ARB and ARGs in various types of treatment plants. Twenty-five published studies were reviewed which contained 215 observations in activated sludge, membrane bioreactors, anaerobic digestion, constructed wetlands, coagulation-filtration, and three types of disinfection. We found 70% decreased observations, 18% increased observations, and 12% unchanged observations of all observations in all treatment processes. Resistance genes to tetracycline were most often observed, but more studies are needed in other antibiotic resistance genes. The causes for increased abundance of ARGs and ARB are not well understood, and further studies are warranted. PRACTITIONER POINTS: Antibiotic resistance is increasing with concern that treatment plants may acclimate bacteria to antibiotics. A literature survey found 215 resistance observations with 70% decreased, 18% increased, 12% unchanged after treatment. The type of treatment process is important with activated sludge showing the greatest reductions.201930682226