Assessing antibiotic sorption in soil: a literature review and new case studies on sulfonamides and macrolides

Rational design of a dual-bacterial system for synchronous removal of antibiotics and Pb(Ⅱ)/Cd(Ⅱ) from water

Facing the combined pollution of antibiotics and heavy metals caused by livestock excrement and industrial effluents, how to use microbial technology to remove these pollutants simultaneously is an important research topic in environmental remediation. In addition, quick separation of the bacteria-water after remediation is also an urgent problem. In this study, we gradually developed a dual-bacteria microbial treatment technology capable of removing Pb(Ⅱ), Cd(Ⅱ) and common antibiotics, as well as self-settling after treatment. The key technology in this study mainly includes modifying the bacterial membrane proteins using Pb-binding protein PbrR, Cd-binding protein CadR and bacterial laccase CotA via surface-display technology to maximize the removal of Pb(Ⅱ), Cd(Ⅱ) and antibiotics, separately. Besides, the introduction of nanobody-antigen adhesion facilitated the self-settling in dual-bacterial system. Then, we studied its effectiveness in removing single pollutants, analyzed the influence of different heavy metal ions, and conducted detailed studies on the kinetics. Further characterization of heavy metal biosorption behavior was conducted using SEM, SEM-EDS, FTIR, and XPS techniques. Via protein fusion and dual vector expression, we constructed a dual-bacteria treatment system that could achieve rapid, selective removal of combined pollutants at a wide pH range temperature range, ultimately precipitating at bottom. Finally, molecular dynamics simulation was employed to elucidate the molecular mechanism underlying the selective biosorption by metal-binding proteins. The findings in this study hold significant implications for achieving selective pollutant removal using engineering bacteria in complex water environments.

Novel carbazole-oxadiazole derivatives as anti-α-glucosidase and anti-α-amylase agents: Design, synthesis, molecular docking, and biological evaluation

To find novel inhibitors of α-glucosidase and α-amylase, a series of new carbazole-oxadiazole derivatives (6a-6n) were prepared, and screened for their anti-α-glucosidase and anti-α-amylase effects. Most of the tested derivatives showed different degrees of α-glucosidase and α-amylase inhibitory activity (IC50: 21.39 ± 0.69-92.05 ± 1.54 μM, 45.53 ± 1.50-126.14 ± 6.33 μM, respectively) compared to the standard acarbose (IC50: 427.00 ± 9.56 μM, 24.68 ± 1.10 μM, respectively). Thereinto, 6c (IC50 = 21.39 ± 0.69 μM) displayed the most effective anti-α-glucosidase activity and 6e presented the best anti-α-amylase activity with an IC50 value of 45.53 ± 1.50 μM. Lineweaver-Burk plot analysis suggested that 6c and 6e behaved as mixed α-glucosidase inhibitor and mixed α-amylase inhibitor, respectively. The results of circular dichroism, atomic force microscope, and molecular docking simulation exposed interaction mechanisms between two preferred compounds (6c and 6e) and their corresponding enzymes. Combined with the possible properties of reducing the elevation in postprandial blood glucose, oral activity, positive bioavailability, and low cytotoxicity of 6c and 6e, it could be concluded that the target derivatives may be able to act as lead molecules for the development of new hypoglycemic agents.

Insight into environmental adaptability of antibiotic resistome from surface water to deep sediments in anthropogenic lakes by metagenomics

The escalating antibiotic resistance threatens the long-term global health. Lake sediment is a vital hotpot in transmitting antibiotic resistance genes (ARGs); however, their vertical distribution pattern and driving mechanisms in sediment cores remain unclear. This study first utilized metagenomics to reveal how resistome is distributed from surface water to 45 cm sediments in four representative lakes, central China. Significant vertical variations in ARG profiles were observed (R2 = 0.421, p < 0.001), with significant reductions in numbers, abundance, and Shannon index from the surface water to deep sediment (all p-values < 0.05). ARGs also has interconnections within the vertical profile of the lakes: twelve ARGs persistently exist all sites and depths, and shared ARGs (e.g., vanS and mexF) were assembled by diverse hosts at varying depths. The 0-18 cm sediment had the highest mobility and health risk of ARGs, followed by the 18-45 cm sediment and water. The drivers of ARGs transformed along the profile of lakes: microbial communities and mobile genetic elements (MGEs) dominated in water, whereas environmental variables gradually become the primary through regulating microbial communities and MGEs with increasing sediment depth. Interestingly, the stochastic process governed ARG assembly, while the stochasticity diminished under the mediation of Chloroflexi, Candidatus Bathyarcaeota and oxidation-reduction potential with increasing depth. Overall, we formulated a conceptual framework to elucidate the vertical environmental adaptability of resistome in anthropogenic lakes. This study shed on the resistance risks and their environmental adaptability from sediment cores, which could reinforce the governance of public health issues.

Indole-Based Compounds in the Development of Anti-Neurodegenerative Agents

Neurodegeneration is a gradual decay process leading to the depletion of neurons in both the central and peripheral nervous systems, ultimately resulting in cognitive dysfunctions and the deterioration of brain functions, alongside a decline in motor skills and behavioral capabilities. Neurodegenerative disorders (NDs) impose a substantial socio-economic strain on society, aggravated by the advancing age of the world population and the absence of effective remedies, predicting a negative future. In this context, the urgency of discovering viable therapies is critical and, despite significant efforts by medicinal chemists in developing potential drug candidates and exploring various small molecules as therapeutics, regrettably, a truly effective treatment is yet to be found. Nitrogen heterocyclic compounds, and particularly those containing the indole nucleus, which has emerged as privileged scaffold, have attracted particular attention for a variety of pharmacological applications. This review analyzes the rational design strategy adopted by different research groups for the development of anti-neurodegenerative indole-based compounds which have the potential to modulate various molecular targets involved in NDs, with reference to the most recent advances between 2018 and 2023.

Experimental data and modeling of sulfadiazine adsorption onto raw and modified clays from Tunisia

In recent years, the increasing detection of emerging pollutants (particularly antibiotics, such as sulfonamides) in agricultural soils and water bodies has raised growing concern about related environmental and health problems. In the current research, sulfadiazine (SDZ) adsorption was studied for three raw and chemically modified clays. The experiments were carried out for increasing doses of the antibiotic (0, 1, 5, 10, 20, and 40 μmol L-1) at ambient temperature and natural pH with a contact time of 24 h. The eventual fitting to Freundlich, Langmuir and Linear adsorption models, as well as residual concentrations of antibiotics after adsorption, was assessed. The results obtained showed that one of the clays (HJ1) adsorbed more SDZ (reaching 99.9 % when 40 μmol L-1 of SDZ were added) than the other clay materials, followed by the acid-activated AM clay (which reached 99.4 % for the same SDZ concentration added). The adsorption of SDZ followed a linear adsorption isotherm, suggesting that hydrophobic interactions, rather than cation exchange, played a significant role in SDZ retention. Concerning the adsorption data, the best adjustment corresponded to the Freundlich model. The highest Freundlich KF scores were obtained for the AM acid-treated and raw HJ1 clays (606.051 and 312.969 Ln μmol1-n kg-1, respectively). The Freundlich n parameter ranged between 0.047 and 1.506. Regarding desorption, the highest value corresponded to the AM clay, being generally <10 % for raw clays, <8 % for base-activated clays, and <6 % for acid-activated clays. Chemical modifications contributed to improve the adsorption capacity of the AM clay, especially when the highest concentrations of the antibiotic were added. The results of this research can be considered relevant as regard environmental and public health assessment since they estimate the feasibility of three Tunisian clays in SDZ removal from aqueous solutions.

Natural attenuation of sulfonamides and metabolites in contaminated groundwater - Review, advantages and challenges of current documentation techniques

Sulfonamides are applied worldwide as antibiotics. They are emerging contaminants of concern, as their presence in the environment may lead to the spread of antibiotic resistance genes. Sulfonamides are present in groundwater systems, which suggest their persistence under certain conditions, highlighting the importance of understanding natural attenuation processes in groundwater. Biodegradation is an essential process, as degradation of sulfonamides reduces the risk of antibiotic resistance spreading. In this review, natural attenuation, and in particular assessment of biodegradation, is evaluated for sulfonamides in groundwater systems. The current knowledge level on biodegradation is reviewed, and a scientific foundation is built based on sulfonamide degradation processes, pathways, metabolites and toxicity. An overview of bacterial species and related metabolites is provided. The main research effort has focused on aerobic conditions while investigations under anaerobic conditions are lacking. The level of implementation in research is laboratory scale; here we strived to bridge towards field application and assessment, by assessing approaches commonly used in monitored natural attenuation. Methods to document contaminant mass loss are assessed to be applicable for sulfonamides, while the approach is limited by a lack of reference standards for metabolites. Furthermore, additional information is required on relevant metabolites in order to improve risk assessments. Based on the current knowledge on biodegradation, it is suggested to use the presence of substituent-containing metabolites from breakage of the sulfonamide bridge as specific indicators of degradation. Microbial approaches are currently available for assessment of microbial community's capacities, however, more knowledge is required on indigenous bacteria capable of degrading sulfonamides and on the impact of environmental conditions on biodegradation. Compound specific stable isotope analysis shows great potential as an additional in situ method, but further developments are required to analyse for sulfonamides at environmentally relevant levels. Finally, in a monitored natural attenuation scheme it is assessed that approaches are available that can uncover some processes related to the fate of sulfonamides in groundwater systems. Nevertheless, there are still unknowns related to relevant bacteria and metabolites for risk assessment as well as the effect of environmental settings such as redox conditions. Alongside, uncovering the fate of sulfonamides in future research, the applicability of the natural attenuation documentation approaches will advance, and provide a step towards in situ remedial concepts for the frequently detected sulfonamides.

A perspective of spatial variability and ecological risks of antibiotics in the agricultural-pastoral ecotone soils in eastern Inner Mongolia

Antibiotics have garnered growing attention as pharmaceuticals ubiquitously present in human society. Within the soil environment, antibiotics exhibit a propensity for high environmental persistence, thereby posing a potential threat to the ecosystem. However, research on antibiotics in agricultural-pastoral ecotone soils is scarce. This study investigates the occurrence, distribution and risk of 11 common antibiotics in agricultural soils of the agro-pastoral transition zone in Horqin Left Middle Banner, eastern Inner Mongolia. The total concentration varies from not detectable to 609.62 μg/kg. Tetracyclines are the dominant antibiotic, with a higher detection frequency than Macrolides and Sulfonamides. The detection rates of the three types of antibiotics differ significantly. The study also finds that soil properties (organic matter content, pH, bulk density, clay, cation exchange capacity have no significant correlation with antibiotics in soil. Moreover, spatial regression analysis reveals that population density is the primary factor influencing the spatial distribution of antibiotics in soil. Ecological risk assessment shows that clarithromycin and erythromycin are the two most harmful factors in the ecological risk of agricultural soil.

Insights into the pH-dependent interactions of sulfadiazine antibiotic with soil particle models

Sulfonamide antibiotics (SAs) are widely used as a broad-spectrum antibiotic, leading to global concerns due to their potential soil accumulation and subsequent effects on ecosystems. SAs often exhibit remarkable environmental persistence, necessitating further investigation to uncover the ultimate destiny of these molecules. In this work, molecular dynamics simulations combined with complementary quantum chemistry calculations were employed to investigate the influence of pH on the behavior of sulfadiazine (SDZ, a typical SAs) in soil particle models (silica, one of the main components of soil). Meanwhile, the quantification of SDZ molecules aggregation potential onto silica was further extended. SDZ molecules tend to form a monolayer on the soil surface under acidic conditions while forming aggregated adsorption on the surface under neutral conditions. Due to the hydrophilicity of the silica, multiple hydration layers would form on its surface, hindering the further adsorption of SDZ molecules on its surface. The calculated soil-water partition coefficient (Psoil/water) of SDZ+ and SDZ were 9.01 and 7.02, respectively. The adsorption evaluation and mechanisms are useful in controlling the migration and transformation of SAs in the soil environment. These findings provide valuable insights into the interactions between SDZ and soil components, shedding light on its fate and transport in the environment.

An evaluation of conventional and nature-based technologies for controlling antibiotic-resistant bacteria and antibiotic-resistant genes in wastewater treatment plants

Antibiotic resistance is a globally recognized health concern which leads to longer hospital stays, increased morbidity, increased mortality, and higher medical costs. Understanding how antibiotic resistance persists and exchanges in environmental systems like soil, water, and wastewater are critically important for understanding the emergence of pathogens with new resistance profiles and the subsequent exposure of people who indirectly/directly come in contact with these pathogens. There are concerns about the widespread application of prophylactic antibiotics in the clinical and agriculture sectors, as well as chemicals/detergents used in food and manufacturing industries, especially the quaternary ammonium compounds which have been found responsible for the generation of resistant genes in water and soil. The rates of horizontal gene transfer increase where there is a lack of proper water/wastewater infrastructure, high antibiotic manufacturing industries, or endpoint users - such as hospitals and intensive agriculture. Conventional wastewater treatment technologies are often inefficient in the reduction of ARB/ARGs and provide the perfect combination of conditions for the development of antibiotic resistance. The wastewater discharged from municipal facilities may therefore be enriched with bacterial communities/pathogens and provide a suitable environment (due to the presence of nutrients and other pollutants) to enhance the transfer of antibiotic resistance. However, facilities with tertiary treatment (either traditional/emerging technologies) provide higher rates of reduction. This review provides a synthesis of the current understanding of wastewater treatment and antibiotic resistance, examining the drivers that may accelerate their possible transmission to a different environment, and highlighting the need for tertiary technologies used in treatment plants for the reduction of resistant bacteria/genes.

Does Environmental Exposure to Pharmaceutical and Personal Care Product Residues Result in the Selection of Antimicrobial-Resistant Microorganisms, and is this Important in Terms of Human Health Outcomes?

The environment plays a critical role in the development, dissemination, and transmission of antimicrobial resistance (AMR). Pharmaceuticals and personal care products (PPCPs) enter the environment through direct application to the environment and through anthropogenic pollution. Although there is a growing body of evidence defining minimal selective concentrations (MSCs) of antibiotics and the role antibiotics play in horizontal gene transfer (HGT), there is limited evidence on the role of non-antibiotic PPCPs. Existing data show associations with the development of resistance or effects on bacterial growth rather than calculating selective endpoints. Research has focused on laboratory-based systems rather than in situ experiments, although PPCP concentrations found throughout wastewater, natural water, and soil environments are often within the range of laboratory-derived MSCs and at concentrations shown to promote HGT. Increased selection and HGT of AMR by PPCPs will result in an increase in total AMR abundance in the environment, increasing the risk of exposure and potential transmission of environmental AMR to humans. There is some evidence to suggest that humans can acquire resistance from environmental settings, with water environments being the most frequently studied. However, because this is currently limited, we recommend that more evidence be gathered to understand the risk the environment plays in regard to human health. In addition, we recommend that future research efforts focus on MSC-based experiments for non-antibiotic PPCPS, particularly in situ, and investigate the effect of PPCP mixtures on AMR. Environ Toxicol Chem 2024;43:623-636. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Low uptake of pharmaceuticals in edible mushrooms grown in polluted biogas digestate

The uptake dynamics of two sulfonamide antibiotics, two fluoroquinolone antibiotics, and the anticonvulsant carbamazepine during the cultivation of two species of edible mushrooms (Agaricus subrufescens and A. bisporus) was investigated. None of the antibiotics were accumulated by the mushrooms, while carbamazepine and its transformation product carbamazepine-10,11-epoxide were taken up by A. bisporus fruiting body but only in small amounts (up to 0.76 and 1.85 μg kg-1 dry weight, respectively). The sulfonamides were quickly removed from the mushroom growth substrate, while the recalcitrant fluoroquinolones and carbamazepine were only partially removed. Dissipation half-lives were generally lower for A. subrufescens than A. bisporus, but A. subrufescens was also grown at a slightly higher culture temperature. A. subrufescens also showed a lower uptake of contaminants. Comparison of maximum dietary intake with other common exposure sources showed that these mushrooms can safely be eaten although produced on a polluted substrate, with respect to the investigated compounds.

Carbon-Supported Nanocomposite Synthesis, Characterization, and Application as an Efficient Adsorbent for Ciprofloxacin and Amoxicillin

The existence of antibiotics in the environment has recently raised serious concerns about their possible hazards to human health and the water ecosystem. In the current study, an activated carbon-supported nanocomposite, AC-CoFe2O3, was synthesized by a coprecipitation method, characterized, and then applied to adsorb different drugs from water. The synthesized composites were characterized by using energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller plots, and scanning electron microscopy. The adsorption of both Ciprofloxacin (Cipro) and Amoxicillin (Amoxi) antibiotics on the composite followed the pseudo-second-order kinetic model (R2 = 0.9981 and 0.9974 mg g-1 min-1, respectively). Langmuir isotherm was the best-fit model showing 312.17 and 217.76 mg g-1 adsorption capacities for Ciprofloxacin and Amoxicillin, respectively, at 333 K. The negative Gibbs free energy (ΔG°) specified the spontaneity of the method. The positive change in the enthalpy (ΔH) indicated that the adsorption process was assisted by higher temperatures. The different optimized parameters were pH, contact time, adsorbent weight, concentration, and temperature. The maximum adsorption of Cipro was found to be 98.41% at pH 12, while for Amoxi, it was 89.09% at pH 2 at 333 K. The drugs were then successfully determined from natural water samples at optimized conditions using these nanocomposites.

Difference of Microbial Community in the Stream Adjacent to the Mixed Antibiotic Effluent Source

Released antibiotics from source to stream can influence bacterial communities and potentially alter the ecosystem. This research provides a comprehensive examination of the sources, distribution, and bacterial community dynamics associated with varied antibiotic release sources adjacent to the stream. The residual of antibiotics from different sources was determined, and the bacterial community structure was examined to reveal the differences in the bacteria community in the stream. The residual of antibiotics was quantified with liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the Illumina MiSeq platform was utilized to sequence bacterial 16S rRNA genes, providing comprehensive insights into the bacterial community structure in the sediment across five different sites. Results indicated that the presence and distribution of antibiotics were significantly influenced by released sources. In the case of the bacterial community, the Proteobacteria and Firmicutes were the most dominant phyla in the sediment, and especially, the Firmicutes showed higher abundance in sites mostly affected by livestock sources. Additionally, livestock gut bacteria such as Clostridium saudiense, Proteiniclasticum ruminis, and Turicibacter sanguinis were prevalent in antibiotic-contaminated sites adjacent to livestock facilities. Overall, this study provides critical insights into the effect of antibiotic contamination by verifying the relationship between the occurrence of antibiotic residuals and the alteration in the bacterial community in the stream.

Synthesis of indole derivatives as Alzheimer inhibitors and their molecular docking study

Acetylcholinesterase prevails in the healthy brain, with butyrylcholinesterase reflected to play a minor role in regulating brain acetylcholine (ACh) levels. However, BuChE activity gradually increases in patients with (AD), while AChE activity remains unaffected or decays. Both enzymes therefore represent legitimate therapeutic targets for ameliorating the cholinergic deficit considered to be responsible for the declines in cognitive, behavioural, and global functioning characteristic of AD. Current study described the synthesis of indole-based sulfonamide derivatives (1-23) and their biological activity. Synthesis of these scaffolds were achieved by mixing chloro-substituted indole bearing amine group with various substituted benzene sulfonyl chloride in pyridine, under refluxed condition to obtained desired products. All products were then evaluated for AchE and BuchE inhibitory potential compare with positive Donepezil as standard drug for both AchE and BchE having IC50 = 0.016 ± 0.12 and 0.30 ± 0.010 μM respectively. In this regard analog 9 was found potent having IC50 value 0.15 ± 0.050 μM and 0.20 ± 0.10 for both AchE and BuChE respectively. All other derivatives also found with better potential. All compounds were characterized by various techniques such as 1H, 13C-NMR and HREI-MS. In addition, biological activity was maintained to explore the bioactive nature of scaffolds and their protein-ligand interaction (PLI) was checked through molecular docking study.Communicated by Ramaswamy H. Sarma.

Clarithromycin as soil and environmental pollutant: Adsorption-desorption processes and influence of pH

Antibiotics pollution is a growing environmental issue, as high amounts of these compounds are found in soil, water and sediments. This work studies the adsorption/desorption of the macrolide antibiotic clarithromycin (CLA) for 17 agricultural soils with different edaphic characteristics. The research was carried out using batch-type experiments, with an additional assessment of the specific influence of pH for 6 of the soils. The results show that CLA adsorption reaches between 26 and 95%. In addition, the fit of the experimental data to adsorption models provided values between 1.9 and 19.7 Ln μmol1-n kg-1 for the KF, Freundlich affinity coefficient, and between 2.5 and 10.5 L kg-1 for Kd, distribution constant of Linear model. Regarding the linearity index, n, it varied between 0.56 and 1.34. Desorption showed lower scores than adsorption, with an average of 20%, and with values of 3.1 and 93.0 Ln μmol1-n kg-1 for KF(des) and 4.4 and 95.0 L kg-1 for Kd(des). The edaphic characteristics with the highest influence on adsorption were the silt fraction content and the exchangeable Ca content, while in the case of desorption, they were the total nitrogen, organic carbon, and exchangeable Ca and Mg contents. Regarding the pH, within the range studied (between 3 and 10), its value did not decisively affect the adsorption/desorption process. Overall, the set of these results could be of help to program appropriate measures leading to the retention/elimination of this antibiotic when it reaches the environment as a pollutant.

The dynamics and transmission of antibiotic resistance associated with plant microbiomes

Antibiotic resistance genes (ARGs) have been widely found and studied in soil and water environments. However, the propagation of ARGs in plant microbiomes has attracted insufficient attention. Plant microbiomes, especially the rhizosphere microorganisms, are closely connected with water, soil, and air, which allows ARGs to spread widely in ecosystems and pose a threat to human health after entering the human body with bacteria. Therefore, it is necessary to deeply understand and explore the dynamics and the transmission of ARGs in rhizosphere microorganisms and endophytes of plants. In this review, the transmission and influencing factors of ARGs in the microorganisms associated with plants, especially the influence of root exudates on plant microbiomes, are analyzed. Notably, the role of intrinsic genes of plants in determining root exudates and their potential effects on ARGs are proposed and analyzed. The important role of phyllosphere microorganisms and endophytes in the transmission of ARGs and co-resistance of antibiotics and other substances are also emphasized. The proliferation and transmission of ARGs associated with plant microbiomes addressed in this review is conducive to revealing the fate of ARGs in plant microorganisms and alleviating ARG pollution.

Competitive adsorption and desorption of three antibiotics in distinct soil aggregate size fractions

Multiple antibiotics that are used in veterinary medicine coexist in soils, but their interaction and the effects on adsorption and desorption in soils have not been extensively studied. In this study, using batch experiments, we evaluated the adsorption and desorption of sulfadiazine (SDZ), tetracycline (TC), and norfloxacin (NFX) using four different soil aggregate size fractions and discovered that: (1) TC had the highest adsorption (76-98 %) and the lowest desorption in each tested system, whereas SDZ showed opposite adsorption and desorption ability, (2) the highest adsorption and the lowest desorption of all three tested antibiotics were observed with soil macroaggregates (250-2000 µm) in all the cases; in contrast, opposite adsorption and desorption ability were observed for soil clay (<53 µm), and (3) adsorption of each antibiotic was in the following order: single system (71-89 %) > binary system (56-84 %) > ternary system (50-78 %); however, desorption were in the reverse order. The Freundlich equation fitting and Brunauer-Emmett-Teller (BET) analysis further demonstrated that the adsorption competition between the tested antibiotics depended mainly on the specific surface area of each soil aggregate size fractions and its chemical properties. In conclusion, soil macroaggregates play a key role in the retention of antibiotics in soils, and the coexistence of multiple antibiotics greatly increases leaching risk.

Adsorption behaviors and influencing factors of antibiotic norfloxacin on natural kaolinite-humic composite colloids in aquatic environment

Particles are ubiquitous and abundant in natural waters and play a crucial role in the fate and bioavailability of organic pollution. In the present study, natural mineral (kaolinites, KL), organic (humic/fulvic acid, HA/FA) and their composite particles were further separated into particles fractions (PFs, >1 μm) and colloidal fractions (CFs, 1 kDa-1 μm) by cross-flow ultrafiltration (CFUF). This research demonstrated the role of kaolinite-humic composite colloids on the adsorption of fluoroquinolone norfloxacin (NOR). The Freundlich model satisfactory described adsorption curves, showing strong affinity of NOR to CFs, with sorption capacity (K_F) between 8975.50 and 16638.13 for NOR. The adsorption capacities of NOR decreased with the particle size increasing from CFs to PFs. In addition, composite CFs showed excellent adsorption capacity, which was mainly attributed to the larger specific surface area of composite CFs and electronegativity and numerous oxygen-containing functional groups on the surfaces of the complexes, and electrostatic attraction, hydrogen bond and cation exchange could dominate the NOR adsorption onto the composite CFs. The best pH value under adsorption condition of composite CFs varied from weakly acidic to neutral with the increase of load amount of humic and fulvic acids on the surface of inorganic particles. The adsorption decreased with higher cation strength, larger cation radius and higher cation valence, which depended on the surface charge of colloids and the molecular shape of NOR. These results provided insight into the interfacial behaviors of NOR on the surfaces of natural colloids and promoted the understanding of the migration and transport of antibiotics in environmental systems.

The impact of antibiotic residues on resistance patterns in leek at harvest

When crops are cultivated on fields fertilized with animal manure, the risk exists that plants may take up antibiotic residues and may be exposed to antibiotic resistance genes and antibiotic resistant bacteria. During cultivation in a greenhouse pot experiment, leek (Allium porrum) was fertilized with either pig slurry or mineral fertilizer and exposed to either no antibiotics, doxycycline (10,000 μg/kg manure), sulfadiazine (1000 μg/kg manure), or lincomycin (1000 μg/kg manure). At harvest, 4.5 months later, lincomycin, sulfadiazine or doxycycline were not detected in any of the leek samples nor in their corresponding soil samples. Further, antimicrobial susceptibility testing was performed on 181 Bacillus cereus group isolates and 52 Pseudomonas aeruginosa isolates from the grown leek. For the B. cereus group isolates, only a small shift in MIC50 for lincomycin was observed among isolates from the lincomycin and control treatment. For P. aeruginosa, only in the setup with doxycycline treatment a higher MIC50 for doxycycline was observed compared to the control, specifically the isolates selected from growth media supplemented with 8 mg/L doxycycline. Nine antibiotic resistance genes (tet(B), tet(L), tet(M), tet(O), tet(Q), tet(W), erm(B), erm(F) and sul2) were investigated at harvest in the leek and soil samples. In the leek samples, none of the antibiotic resistance genes were detected. In the soil samples fertilized with pig slurry, the genes erm(B), erm(F), tet(M), sul2, tet(W) and tet(O) were detected in significantly higher copy numbers in the lincomycin treatment as compared to the other antibiotic treatments. This could be due to a shift in soil microbiota induced by the addition of lincomycin. The results of this study indicate that consumption of leek carries a low risk of exposure to antibiotic residues or antibiotic resistance to doxycycline, sulfadiazine or lincomycin.

Advancements in the dominion of fate and transport of pharmaceuticals and personal care products in the environment-a bibliometric study

The study on the fate and transport of Pharmaceuticals and Personal Care Products, PPCPs (FTP) in the environment, has received particular attention for over two decades. The PPCPs threaten ecology and human health even at low concentrations due to their synergistic effects and long-range transport. The research aims to provide an inclusive map of the scientific background of FTP research over the last 25 years, from 1996 to 2020, to identify the main characteristics, evolution, salient research themes, trends, and research hotspots in the field of interest. Bibliometric networks were synthesized and analyzed for 577 journal articles extracted from the Scopus database. Consequently, seven major themes of FTP research were identified as follows: (i) PPCPs category; (ii) hazardous effects; (iii) occurrence of PPCPs; (iv) PPCPs in organisms; (v) remediation; (vi) FTP-governing processes; and (vii) assessment in the environment. The themes gave an in-depth picture of the sources of PPCPs and their transport and fate processes in the environment, which originated from sewage treatment plants and transported further to sediment/soils/groundwater/oceans that act as the PPCPs' major sink. The article provided a rigorous analysis of the research landscape in the FTP study conducted during the specified years. The prominent research themes, content analysis, and research hotspots identified in the study may serve as the basis of real-time guidance to lead future research areas and a prior review for policymakers and practitioners.

Mesocosm experiment to determine the contribution of adsorption, biodegradation, hydrolysis and photodegradation in the attenuation of antibiotics at the water sediment interface

To understand the fate of antibiotics in the aquatic environment, we need to evaluate to which extent the following processes contribute to the overall antibiotic attenuation: adsorption to river sediment, biodegradation, hydrolysis and photodegradation. A laboratory scale mesocosm experiment was conducted in 10 L reactors filled with river sediment and water. The reactors were spiked with four classes of antibiotics (fluoroquinolones, macrolides, sulfonamides, tetracyclines), as well as clindamycin and trimethoprim. The experimental-set-up was designed to study the attenuation processes in parallel in one mesocosm experiment, hence also considering synergetic effects. Our results showed that antibiotics belonging to the same class exhibited similar behavior. Adsorption was the main attenuation process for the fluoroquinolones and tetracyclines (44.4 to 80.0 %). For the sulfonamides, biodegradation was the most frequent process (50.2 to 65.1 %). Hydrolysis appeared to be significant only for tetracyclines (12.6 to 41.8 %). Photodegradation through visible light played a minor role for most of the antibiotics - fluoroquinolones, sulfonamides, and trimethoprim (0.7 to 24.7 %). The macrolides were the only class of antibiotics not affected by the studied processes and they persisted in the water phase. Based on our results, we propose to class the antibiotics in three groups according to their persistence in the water phase. Fluoroquinolones and tetracyclines were non-persistent (half-lives shorter than 11 d). Chlorotetracycline, sulfapyridine and trimethoprim showed a moderate persistence (half-lives between 12 and 35 d). Due to half-lives longer than 36 d sulfonamides and clindamycin were classified as persistent.

Comprehensive analysis of the fates and risks of veterinary antibiotics in a small ecosystem comprising a pig farm and its surroundings in Northeast China

This study investigated the behavior of veterinary antibiotics (VAs) in a small farm ecosystem. Manure and environmental samples were collected around a large pig farm in northeast China. Thirty-four VAs in six categories were analyzed. Then, a multimedia fugacity model was used to estimate the fates of VAs in the environment. The results showed that VAs were prevalent in manure, soil, water, and sediment, but not in crops. Compared with fresh manure, VA levels were significantly lower in surface manure piles left in the open air for 3-6 months. The main VAs, tetracyclines and quinolones, decreased by 427.12 and 158.45 µg/kg, respectively. VAs from manure piles were transported to the surroundings and migrated vertically into deep soil. The concentrations of ∑VAs detected in agricultural soils were 0.03-4.60 µg/kg; > 94% of the mass inventory of the VAs was retained in soil organic matter (SOM), suggesting that SOM is the main reservoir for antibiotics in soil. Risk assessment and model analysis indicated that the negative impact of mixed antibiotics at low concentrations in farmland on crops may be mediated by indirect effects, rather than direct effects. Our findings highlight the environmental fates and risks of antibiotics from livestock farms.

A review of the influence of soil minerals and organic matter on the migration and transformation of sulfonamides

Sulfonamides (SAs) are common antibiotics that are widely present in the environment and can easily migrate in the environment, so they pose an environmental risk. Minerals and organic matter influence the antibiotic migration and transformation in sewage treatment plants, activated sludge, surface water, and soil environment. In the present paper, the influence of the process and mechanism of minerals and organic matter on the adsorption, degradation, and plant uptake of SAs in soil were summarized. In the impact process of mineral and organic matter on the SAs migration and transformation, the pH value is undoubtedly the most important factor because it determines the ionic state of SAs. In terms of influence mechanisms, the minerals absorb SAs well via cation exchange, complexation, H-bonding, and cation bridging. Mineral photodegradation is also one of the primary removal methods for SAs. Soil organic matter (SOM) can significantly increase the SAs adsorption. The adsorption forces of SAs and SOM or dissolved organic matter (DOM) were very similar, but SOM decreased SAs mobility in the environment, while DOM increased SAs availability. DOM generated active substances and aided in the photodegradation of SAs. This review describes the effects of minerals and organic matter on the fate of SAs in soil, which is useful in controlling the migration and transformation of SAs in the soil environment.

Human health risk estimation of antibiotics transferred from wastewater and soil to crops

Antibiotics enter into agricultural land, via manure application or wastewater irrigation. The practices of using untreated wastewater in the agricultural system help in the bioaccumulation of antibiotics in vegetables and other crops. Exposure to the bioaccumulated antibiotics poses serious health risks to ecosystem and human. In this study, the prevalence of two fluoroquinolones (levofloxacin and ciprofloxacin), their bioaccumulation in five crops (Daucus carota L., Pisum sativum L., Raphanus raphanistrum L., Lactuca sativa L., Spinacia oleracea L.), and associated human health risks were investigated. Lettuce showed highest bioaccumulation of levofloxacin (LEV) (12.66 μg kg-1) and carrot showed high bioaccumulation of ciprofloxacin (CIP) (13.01 μg kg-1). In roots, bioconcentration factor (BCFroot) was observed to be relatively high in radish (LEV 0.24-0.43, CIP 0.32-0.49) and observed to be lower in spinach (LEV 0.05-0.13, CIP 0.12-0.19). The translocation factor (TF) for LEV and CIP was generally >1 for all five crops under all treatment. The final transfer and distribution of LEV and CIP in the edible parts of the crops were as follows: leaves > shoots > roots for both antibiotics. Risk quotient of both LEV and CIP in current study is found to be in between 0.018 and 0.557 and shows a medium risk (0.1 to 1) to human health due the discharge of untreated wastewater into the fields. However, our study reports that both antibiotics do accumulate in the edible plant parts; therefore, it poses potential risks to human health.

Antibiotics, antibiotic resistance and associated risk in natural springs from an agroecosystem environment

This study investigates the occurrence, transport, and risks associated to antibiotic residues, antibiotic resistance genes (ARGs) and antibiotic resistant Escherichia coli (AR-E. coli) in eleven natural springs in an agroecosystem environment with intense livestock production, where groundwater nitrate concentration usually sets above 50 mg L^-1. Out of 23 multiple-class antibiotics monitored, tetracycline and sulfonamide residues were the most ubiquitous, and they were detected at concentrations ranging from ng L^-1 to μg L^-1. Five ARGs were monitored, conferring resistance to the antibiotic classes of major use in livestock production. Thus, genes conferring resistance to sulfonamides (sul1 and sul2) and tetracyclines (tetW) as well as a gene proxy for anthropogenic pollution (intI1) were present in most springs. sul1 was the most abundant, with absolute concentrations ranging from 4 × 10² to 5.6 × 10⁶ gene copies L^-1 water. AR-E. coli showing resistance to sulfonamides and tetracyclines was also detected, with a prevalence up to approximately 40 % in some sites but with poor correlations with the concentration of antibiotic residues and ARGs. The occurrence of antibiotics, ARGs and AR-E. coli was characterized by large seasonal variations which were mostly associated to both hydrological factors and reactive transport processes. Finally, a risk assessment approach pointed out towards low risk for both the groundwater environment and human health, when spring water is used for direct human consumption, associated with the occurrence of antibiotics, ARGs and AR-E. coli. However, long-term effects cannot be neglected, and proper actions must be taken to preserve groundwater quality.

Antibiotic concentrations and antibiotic resistance in aquatic environments of the WHO Western Pacific and South-East Asia regions: a systematic review and probabilistic environmental hazard assessment

BACKGROUND

Antibiotic resistance poses human health risks, and there are concerns about the effect of environmental antibiotic residues in the selection and spread of antibiotic resistance. The aim of this study was to identify antibiotic residue levels that are likely to select for resistance and relative contributions from different aquatic sources, of various aquatic environmental compartments of the WHO Western Pacific region (WPR) and the WHO South-East Asia region (SEAR), including in China and India.

METHODS

A systematic review of empirical studies that measured antibiotic concentrations in aquatic environments, published between 2006 and 2019, and a probabilistic environmental hazard assessments approach, were used to identify antibiotic concentrations that are likely to select for resistance in various aquatic environmental compartments of the WPR and SEAR, including in China and India. The assessment involved the use of measured environmental concentrations and predicted no-effect concentrations (PNECs).

FINDINGS

The systematic review found 218 relevant studies of 5230 screened from the WPR and 22 relevant studies of 2625 screened from the SEAR; some of these relevant studies were largely from China (n=168) and India (n=15). 92 antibiotics in the WPR and 45 in the SEAR were detected in various aquatic compartments. Antibiotic concentrations that most likely exceeded PNECs (0-100%) were observed in wastewater, and influents and effluents of wastewater treatment plants. Antibiotic concentrations that most likely exceeded PNECs were also observed in aquatic environmental compartments. The highest risk for the development of resistance was in tap or drinking water of the WPR and China for ciprofloxacin (62·5%). The relative contributions of potential sources of antibiotic contamination in waterways, such as hospitals, municipals, livestock, and pharmaceutical manufacturing, was determined for each antibiotic.

INTERPRETATION

The concentrations of antibiotic residues found in wastewater and wastewater treatment plants of the WPR and SEAR make them potential hotspots for the development of antibiotic resistance, which creates human health risks from environmental exposure via drinking water. These findings can help decision makers to target risk reduction measures against environmental residues of priority antibiotics in high-risk sites, and help to focus research efforts in these world regions.

FUNDING

Swedish Research Council.

New Models for Estimating the Sorption of Sulfonamide and Tetracycline Antibiotics in Soils

Sulfonamides (SAs) and tetracyclines (TCs) are two classes of widely used antibiotics. There is a lack of easy models for estimating the parameters of antibiotic sorption in soils. In this work, a dataset of affinity coefficients (Kf and Kd) of seven SA/TC antibiotics (i.e., sulfachlorpyridazine, sulfamethazine, sulfadiazine, sulfamethoxazole, oxytetracycline, tetracycline, and chlortetracycline) and associated soil properties was generated. Correlation analysis of these data showed that the affinity coefficients of the SAs were predominantly affected by soil organic matter and cation exchange capacity, while those of the TCs were largely affected by soil organic matter and pH. Pedotransfer functions for estimating Kf and Kd were built by multiple linear regression analysis and were satisfactorily validated. Their performances would be better for soils having higher organic matter content and lower pH. These pedotransfer functions can be used to aid environmental risk assessment, prioritization of antibiotics and identification of vulnerable soils.

A high-precision prediction for spatiotemporal distribution and risk assessment of antibiotics in an urban watershed using a hydrodynamic model

A methodology for the high-precision prediction and risk assessment of antibiotics at the watershed scale was established. Antibiotic emission inventory and attenuation processes were integrated into the MIKE 11 model to predict the spatiotemporal distribution of norfloxacin, ofloxacin, enrofloxacin, erythromycin, roxithromycin, and sulfamethoxazole in the Nanfei River watershed, China. Considering the variations in antibiotic removal in sewage treatment plants, manure composting, and lagoon systems, the high, medium, and low removal efficiencies of selected antibiotics across China were obtained and used as the best, expected, and worst scenarios, respectively, to evaluate the uncertainty of antibiotic emissions. The predicted concentrations were comparable to antibiotic measurements after flow calibration. The prediction results showed that the highest concentration exposures were mainly concentrated in urban areas with a dense population. Flow variations controlled the temporal distribution characteristics of antibiotics via the dilution effect, and the concentrations of antibiotics in the dry season were 3.1 times higher than those in the wet season. The median concentrations of norfloxacin and erythromycin ranged from 111.36 ng/L to 592.33 ng/L and 106.63 ng/L to 563.01 ng/L, respectively, which both posed a high risk to cyanobacteria and a medium risk to spreading antibiotic resistance. Scenario analysis further demonstrated that high removal efficiencies of these antibiotics can considerably reduce the potential ecotoxicity risks and bacterial resistance selection. The developed methodology for predicting the distribution and risk of antibiotics was suitable for the risk assessment and control strategy of human- and livestock-sourced pollutants.

Influence of Organic Matter on the Sorption of Cefdinir, Memantine and Praziquantel on Different Soil and Sediment Samples

Pharmaceuticals are known for their great effects and applications in the treatment and suppression of various diseases in human and veterinary medicine. The development and modernization of science and technologies have led to a constant increase in the production and consumption of various classes of pharmaceuticals, so they pose a threat to the environment, which can be subjected to the sorption process on the solid phase. The efficiency of sorption is determined by various parameters, of which the physicochemical properties of the compound and the sorbent are very important. One of these parameters that determine pharmaceutical mobility in soil or sediment is the soil−water partition coefficient normalized to organic carbon (Koc), whose determination was the purpose of this study. The influence of organic matter, suspended in an aqueous solution of pharmaceutical (more precisely: cefdinir, memantine, and praziquantel), was studied for five different types of soil and sediment samples from Croatia. The linear, Freundlich, and Dubinin−Raduskevich sorption isotherms were used to determine specific constants such as the partition coefficient Kd, which directly describes the strength of sorbate and sorbent binding. The linear model proved to be the best with the highest correlation coefficients, R2 > 0.99. For all three pharmaceuticals, a positive correlation between sorption affinity described by Kd and Koc and the amount of organic matter was demonstrated.

Competitive adsorption and desorption of tetracycline and sulfadiazine in crop soils

In view of the environmental issues caused by antibiotics, this research studies competitive adsorption/desorption for tetracycline (TC) and sulfadiazine (SDZ) in agricultural soils. Competitive adsorption was studied in binary systems (adding equal concentrations of both antibiotics). In addition, it was compared with results from simple systems. In all cases, batch-type adsorption/desorption experiments were carried out. In the binary systems, for the highest antibiotic concentration added, adsorption percentages were always higher for TC (close to 100%) than for SDZ (10-90%). In these systems, TC desorption was lower than 5% for all soils, and generally <10% for SDZ. Comparing TC and SDZ adsorption for the different systems, SDZ was clearly affected by the presence of TC, with SDZ adsorption percentages being was much higher (with differences generally above 65%) in the binary than in the simple systems. On the contrary, comparing the results of TC adsorption in simple and binary systems, TC was not affected by the presence of SDZ, obtaining similar adsorption percentages in both systems. K_d and K_F values (in the Linear and Freundlich models), were higher in the simple systems in the case of TC, which could be due to competition with SDZ, while for SDZ K_d and K_F were higher in the binary systems, with a synergistic effect of TC favoring SDZ adsorption. Regarding desorption, it reached 100% for SDZ in some soils in simple systems, dropping to 10% in the presence of TC. TC desorption was <4%, not affected by SDZ. The results indicate that environmental risks would be higher for SDZ, showing differences when both antibiotics are present. This can be considered relevant as regards public health and environmental preservation, in view of direct toxicities and the promotion of resistance to antibiotics associated with the presence of these contaminants in the environment.

Insights into the fate of antibiotics in constructed wetland systems: Removal performance and mechanisms

Antibiotics have been recognized as emerging contaminants that are widely distributed and accumulated in aquatic environment, posing a risk to ecosystem at trace level. Constructed wetlands (CWs) have been regarded as a sustainable and cost-effective alternative for efficient elimination of antibiotics. This review summarizes the removal of 5 categories of widely used antibiotics in CWs, and discusses the roles of the key components in CW system, i.e., substrate, macrophytes, and microorganisms, in removing antibiotics. Overall, the vertical subsurface flow CWs have proven to perform better in terms of antibiotic removal (>78%) compared to other single CWs. The adsorption behavior of antibiotics in wetland substrates is determined by the physicochemical properties of antibiotics, substrate configuration and operating parameters. The effects of wetland plants on antibiotic removal mainly include direct (e.g., plant uptake and degradation) and indirect (e.g., rhizosphere processes) manners. The possible interactions between microorganisms and antibiotics include biosorption, bioaccumulation and biodegradation. The potential strategies for further enhancement of the antibiotic removal performance in CWs included optimizing operation parameters, innovating substrate, strengthening microbial activity, and integrating with other treatment technologies. Taken together, this review provides useful information for facilitating the development of feasible, innovative and intensive antibiotic removal technologies in CWs, as well as enhancing the economic viability and ecological sustainability.

Synthesis, In Vitro Anti-Microbial Analysis and Molecular Docking Study of Aliphatic Hydrazide-Based Benzene Sulphonamide Derivatives as Potent Inhibitors of α-Glucosidase and Urease

A unique series of sulphonamide derivatives was attempted to be synthesized in this study using a new and effective method. All of the synthesized compounds were verified using several spectroscopic methods, including FTIR, ¹H-NMR, ¹³C-NMR, and HREI-MS, and their binding interactions were studied using molecular docking. The enzymes urease and α-glucosidase were evaluated against each derivative (1–15). When compared to their respective standard drug such as acarbose and thiourea, almost all compounds were shown to have excellent activity. Among the screened series, analogs 5 (IC₅₀ = 3.20 ± 0.40 and 2.10 ± 0.10 µM) and 6 (IC₅₀ = 2.50 ± 0.40 and 5.30 ± 0.20 µM), emerged as potent molecules when compared to the standard drugs acarbose (IC₅₀ = 8.24 ± 0.08 µM) and urease (IC₅₀ = 7.80 ± 0.30). Moreover, an anti-microbial study also demonstrated that analogs 5 and 6 were found with minimum inhibitory concentrations (MICs) in the presence of standard drugs streptomycin and terinafine.

Determination of antimicrobial agents and their transformation products in an agricultural water-soil system modified with manure

Manure fertilization is the primary source of veterinary antimicrobials in the water-soil system. The research gap is the fate of antimicrobials after their release into the environment. This study aimed to provide a detailed and multi-faceted examination of fertilized cultivated fields using two types of manure (poultry and bovine) enriched with selected antimicrobials. The research focused on assessing the mobility and stability of antimicrobials in the water-soil system. Additionally, transformation products of antimicrobials in the environment were identified. The extraction (solid-phase extraction and/or solid-liquid extraction) and LC-MS/MS analysis procedures were developed to determine 14 antimicrobials in the soil and pore water samples. Ten out of fourteen antimicrobials were detected in manure-amended soil and pore water samples. The highest concentration in the soil was 109.1 ng g^-1 (doxycycline), while in pore water, it was 186.6 ng L^-1 (ciprofloxacin). Sixteen transformation products of antimicrobials were identified in the soil and soil-related pore water. The same transformation products were detected in both soil and soil pore water extracts, with significantly higher signal intensities observed in soil extracts than in water. Transformation products were formed in oxidation, carbonylation, and ring-opening reactions.

Global review of macrolide antibiotics in the aquatic environment: Sources, occurrence, fate, ecotoxicity, and risk assessment

The extensive use of macrolide antibiotics (MCLs) has led to their frequent detection in aquatic environments, affecting water quality and ecological health. In this study, the sources, global distribution, environmental fate, ecotoxicity and global risk assessment of MCLs were analyzed based on recently published literature. The results revealed that there are eight main sources of MCLs in the water environment. These pollution sources resulted in MCL detection at average or median concentrations of up to 3847 ng/L, and the most polluted water bodies were the receiving waters of wastewater treatment plants (WWTPs) and densely inhabited areas. Considering the environmental fate, adsorption, indirect photodegradation, and bioremoval may be the main attenuation mechanisms in natural water environments. N-demethylation, O-demethylation, sugar and side chain loss from MCL molecules were the main pathways of MCLs photodegradation. Demethylation, phosphorylation, N-oxidation, lactone ring hydrolysis, and sugar loss were the main biodegradation pathways. The median effective concentration values of MCLs for microalgae, crustaceans, fish, and invertebrates were 0.21, 39.30, 106.42, and 28.00 mg/L, respectively. MCLs induced the generation of reactive oxygen species, that caused oxidative stress to biomolecules, and affected gene expression related to photosynthesis, energy metabolism, DNA replication, and repair. Moreover, over 50% of the reported water bodies represented a medium to high risk to microalgae. Further studies on the development of tertiary treatment technologies for antibiotic removal in WWTPs, the combined ecotoxicity of antibiotic mixtures at environmental concentration levels, and the development of accurate ecological risk assessment models should be encouraged.

Distribution and ecological risks of pharmaceuticals and personal care products with different anthropogenic stresses in a coastal watershed of China

The occurrences of pharmaceutical and personal care products (PPCPs) in both freshwater and sea have been widely reported. However, pollution control requires further information on riverine discharges with influence of land-based activities and associated risks to estuarine ecosystems. This study investigated the spatial occurrences and the relationship to sociodemographic parameters of 30 PPCPs in 67 rivers along the Bohai coastal region. The results showed that PPCPs were mainly deposited in aquatic phase, and the partitioning coefficient between water and sediment was highly determined by chemical properties. The levels of 30 PPCPs in rivers ranged from 8.33 to 894.48 ng/L, showing a large variance among regions. Caffeine, sulfamethoxazole, sulfamethazine, ofloxacin, anhydro-erythromycin, and trimethoprim were found to be the major pollutants. Multivariable analysis method was used to assess the correlation of PPCPs markers to socio-economic parameters. The results indicated that domestic emissions contributed most to the occurrences of PPCPs in the riverine water. Risk assessment result indicated that sulfamethoxazole, caffeine, tetracycline, and carbamazepine ranked top four with the highest risks to the most sensitive aquatic organisms. The results identified caffeine and carbamazepine with high detection frequency and concentration as the priority chemicals, while sulfamethoxazole and erythromycin should also be concerned due to their potential threats in specific rivers. This study provides valuable information for pollution control over PPCPs riverine discharges in estuarine regions.

Impacts of farmland application of antibiotic-contaminated manures on the occurrence of antibiotic residues and antibiotic resistance genes in soil: A meta-analysis study

A meta-analysis of 94 published studies was conducted to explore the impacts of farmland application of antibiotic-contaminated manures on antibiotic concentrations and ARG abundances in manure-amended soil. Forty-nine antibiotics were reported, in which chlortetracycline, oxytetracycline, doxycycline, tetracycline, enrofloxacin, ciprofloxacin and norfloxacin were the most prevalent and had relatively high concentrations. The responses of ARG and mobile genetic element (MGE) abundances to farmland application of antibiotic-contaminated manures varied considerably under different management strategies and environmental settings. On average, compared to unamended treatments, farmland application of antibiotic-contaminated manures significantly increased the total ARG and MGE abundances by 591% and 351%, respectively (P < 0.05). Of all the included ARG classes, the largest increase was found for sulfonamide resistance genes (1121%), followed by aminoglycoside (852%) and tetracycline (763%) resistance genes. Correlation analysis suggested that soil organic carbon (SOC) was significantly negatively correlated with antibiotic concentrations in manured soil (P < 0.05) due to the formation of covalent bonds and nonextractable residues. Soil silt content was significantly positively correlated with antibiotic concentration (P < 0.05), which was attributed to greater sorption capacities. The ARG abundances were significantly positively correlated with soil silt content, antibiotic concentrations, mean annual temperature, SOC, MGEs and soil pH (P < 0.05), suggesting that changes in these factors may shape the ARG profiles. Collectively, these findings advanced our understanding of the occurrence of antibiotics and ARGs in manure-amended soil and potential factors affecting them and will contribute to better management of these contaminants in future agricultural production.

Understanding flow patterns from the field - Controlled laboratory experiments on the transport behavior of veterinary antibiotics in the presence of liquid manure

The main entry path of veterinary antibiotics to the environment is the application of liquid manure on agricultural land. Along with the manure, they can infiltrate into soils and leach into groundwater. As the environmental behavior of veterinary antibiotics is strongly affected by the process of sorption, the comprehensive knowledge regarding their sorption behavior is key to a reliable risk assessment. However, the flow patterns in field experiments are influenced by several factors that can hardly be distinguished, while most of the sorption studies on veterinary antibiotics were designed without manure or as batch experiments, which means that the effects of manure on the transport behavior of the antibiotic substances remained unaccounted for. In order to understand the results from a previous field experiment and concurrently fill the identified knowledge gap, a column experiment was performed to investigate the effects of manure on the transport of sulfamethazine, sulfadiazine, tetracycline, and lincomycin in soil. Results show that sulfamethazine and sulfadiazine were highly mobile in both the presence and absence of manure, while tetracycline did not appear at the outlet of any column. Despite their high mobility, in the presence of manure the sulfonamides were slightly delayed compared to the conservative tracer as was also seen during the previous field experiment. Lincomycin transport was already delayed in the absence of manure. Furthermore, in the presence of manure, lincomycin was delayed by 4.5 times relative to the tracer, which clearly underlined the influence of manure on the transport of lincomycin and offers an explanation why lincomycin has barely been detected in the long-term field experiment. However, in contrast to the results obtained in the field experiment, the recovery rates were the same in presence and absence of manure for both sulfonamides and lincomycin, probably due to reduced degradation at the applied concentration level.

Relevance of sorption in bio-reduction of amoxicillin taking place in forest and crop soils

The fate of antibiotics reaching soils is a matter of concern, given its potential repercussions on public health and the environment. In this work, the potential bio-reduction of the antibiotic amoxicillin (AMX), affected by sorption and desorption, is studied for 17 soils with clearly different characteristics. To carry out these studies, batch-type tests were performed, adding increasing concentrations of AMX (0, 2.5, 5, 10, 20, 30, 40, and 50 μmol L^-1) to the soils. For the highest concentration added (50 μmol L^-1), the adsorption values for forest soils ranged from 90.97 to 102.54 μmol kg^-1 (74.21-82.41% of the amounts of antibiotic added), while the range was 69.96-94.87 μmol kg^-1 (68.31-92.56%) for maize soils, and 52.72-85.40 μmol kg^-1 (50.96-82.55%) for vineyard soils. When comparing the results for all soils, the highest adsorption corresponded to those more acidic and with high organic matter and non-crystalline minerals contents. The best adjustment to adsorption models corresponded to Freundlich's. AMX desorption was generally <10%; specifically, the maximum was 6.5% in forest soils, and 16.9% in agricultural soils. These results can be considered relevant since they cover agricultural and forest soils with a wide range of pH and organic matter contents, for an antibiotic that, reaching the environment as a contaminant, can pose a potential danger to human and environmental health.

Water-sediment partitioning of flumequine and florfenicol, two antibiotics used in salmon aquaculture in Chile

The water-sediment partitioning of flumequine and florfenicol, two antibiotics used in salmon aquaculture is a critical driver of their fate and environmental impact. Batch experiments, were carried out using pure water or seawater, with or without sediment, and at summer and winter temperatures of Chilean fjords. Log K_d (partition between water and sediment) of florfenicol in seawater varied from 0.62 ± 0.69 to 0.67 ± 0.13, and Log K_OC (partition between water and organic fraction of sediment) from 2.15± 0.29 to 2.19 ± 0.13. Difference between K_OC and the octanol-water partition constant (K_OW) showed that for florfenicol, adsorption onto the surface of particles was more significant than the absorption driven by hydrophobicity whilst hydrophobic absorption was a major driver of flumequine sorption. Flumequine Log K_d (0.92 ± 0.25 to 1.36 ± 0.10) and Log K_OC (from 2.44 ± 0.25 to 2.89 ± 0.10) demonstrated its greater affinity than florfenicol to particles and potential accumulation into marine sediments.

Suspect screening of antimicrobial agents transformation products in environmental samples development of LC-QTrap method running in pseudo MRM transitions

The aim of the work was to develop a new HPLC-MS/MS method that allows for the simultaneous detection of antimicrobials agents (targeted analysis) and their transformation products (non-targeted analysis), which enabled the elucidation of their transformation pathways in the environment. Targeted analysis was performed for 16 selected antimicrobials agents (AMs) in wastewater collected at different stages of the treatment process and river water from sections before and after wastewater discharge. The samples were collected in the Łyna sewage treatment plant (Olsztyn, Poland) in three measuring periods at different seasons. Analytes were selected from tetracyclines, fluoroquinolones, β-lactams, macrolides, glycopeptides, lincosamides and synthetic antibiotics. As a part of the targeted analysis, 13 AMs were detected in wastewater samples, and 7 of them in river water samples. However, their presence and concentrations were closely related to the type of the sample and the season in which the sample was taken. The highest concentrations of AMs were detected in samples collected in September (max. 1643.7 ng L^-1 TRI), while the lowest AMs concentrations were found in samples collected in June (max. 136.1 ng L^-1 CLR). The total content of AMs in untreated wastewater was in the range of 1.42-1644 ng L^-1, while in the river water was for upstream 1.22-48.73 ng L^-1 and for downstream 2.24-149 ng L^-1. In the non-target analysis, 33 degradation products of the selected AMs were identified, and the transformation pathways of their degradation were speculated. In the course of the research, it was found that as a result of the processes taking place in wastewater treatment plant, the parent substances are transformed into a number of stable transformation products. Transformation products resulted from hydroxylation, ring opening, oxidation, methylation or demethylation, carboxylation, or cleavage of the CN bond of the parent AMs.

From gut to mud: dissemination of antimicrobial resistance between animal and agricultural niches

With increasing reports on antimicrobial resistance (AMR) in humans, animals and the environment, we are at risk of returning to a pre-antibiotic era. Therefore, AMR is recognized as one of the major global health threats of this century. Antibiotics are used extensively in farming systems to treat and prevent infections in food animals or to increase their growth. Besides the risk of a transfer of AMR between the human and the animal sector, there is another yet largely overlooked sector in the One Health triad. Human-dominated ecosystems such as agricultural soils are a major sink for antibiotics and AMR originating from livestock farming. This review summarizes current knowledge on the prevalence of AMR at the interface of animal and agricultural production and discusses the potential implications for human health. Soil resistomes are augmented by the application of manure from treated livestock. Subsequent transfer of AMR into plant microbiomes may likely play a critical role in human exposure to antibiotic resistance in the environment. Based on the knowledge that is currently available we advocate that more attention should be paid to the role of environmental resistomes in the AMR crisis.

Effect of Soil Solution Properties and Cu2+ Co-Existence on the Adsorption of Sulfadiazine onto Paddy Soil

Paddy soils are globally distributed and saturated with water long term, which is different from most terrestrial ecosystems. To better understand the environmental risks of antibiotics in paddy soils, this study chose sulfadiazine (SDZ) as a typical antibiotic. We investigated its adsorption behavior and the influence of soil solution properties, such as pH conditions, dissolved organic carbon (DOC), ionic concentrations (IC), and the co-existence of Cu²⁺. The results indicated that (1) changes in soil solution pH and IC lower the adsorption of SDZ in paddy soils. (2) Increase of DOC facilitated the adsorption of SDZ in paddy soils. (3) Cu²⁺ co-existence increased the adsorption of SDZ on organic components, but decreased the adsorption capacity of clay soil for SDZ. (4) Further FTIR and SEM analyses indicated that complexation may not be the only form of Cu²⁺ and SDZ co-adsorption in paddy soils. Based on the above results, it can be concluded that soil solution properties and co-existent cations determine the sorption behavior of SDZ in paddy soils.

Chemical Fate and Partitioning Behavior of Antibiotics in the Aquatic Environment-A Review

Antibiotics in the aquatic environment is a major problem because of the emergence of antibiotic resistance. The long-term ecological impact on the aquatic environment is unknown. Many sources allow entry of antibiotics into the environment, including wastewater-treatment plants (WWTPs), agricultural runoff, hospital effluent, and landfill leachate. Concentrations of antibiotics in the aquatic environment vary significantly; studies have shown fluoroquinolones, tetracycline, macrolides, sulfonamides, and penicillins to reach 2900, 1500, 9700, 21 400, and 1600 ng L^-1 in wastewater effluent samples, respectively. However, concentrations are highly variable between different countries and depend on several factors including seasonal variation, prescription, and WWTP operating procedures. Likewise, the reported concentrations that cause environmental effects vary greatly between antibiotics, even within the same class; however, this predicted concentration for the antibiotics considered was frequently <1000 ngL^-1 , indicating that when discharged into the environment along with treated effluent, these antibiotics have a potentially detrimental effect on the environment. Antibiotics are generally quite hydrophilic in nature; however, they can ionize in the aquatic environment to form charged structures, such as cations, zwitterions, and anions. Certain classes, particularly fluoroquinolones and tetracyclines, can adsorb onto solid matrices, including soils, sediment, and sludge, making it difficult to fully understand their chemical fate in the aquatic environment. The adsorption coefficient (K_d ) varies between different classes of antibiotics, with tetracyclines and fluoroquinolones showing the highest K_d values. The K_d values for fluoroquinolones, tetracyclines, macrolides, and sulfonamides have been reported as 54 600, 7600, 130, and 1.37 L kg^-1 , respectively. Factors such as pH of the environment, solid matrix (sediment/soil sludge), and ionic strength can influence the K_d ; therefore, several values exist in literature for the same compound. Environ Toxicol Chem 2021;40:3275-3298. © 2021 SETAC.

An integrated modelling approach to derive the grey water footprint of veterinary antibiotics

Water pollution by veterinary antibiotics (VAs) resulting from livestock production is associated with severe environmental and human health risks. While upward trends in global animal product consumption signal that these risks might exacerbate toward the future, VA related water pollution is currently insufficiently understood. To increase this understanding, the present research assesses processes influencing VA pollution from VA administration to their discharge into freshwater bodies, using an integrated modelling approach (IMA). For the VAs amoxicillin, doxycycline, oxytetracycline, sulfamethazine, and tetracycline we estimate loads administered to livestock, excretion, degradation during manure storage, fate in soil and transport to surface water. Fate and transport are modelled using the VA transport model (VANTOM), which is fed with estimates from the Pan-European Soil Erosion Risk Assessment (PESERA). The grey water footprint (GWF) is used to indicate the severity of water pollution in volumetric terms by combining VA loads and predicted no effect concentrations. We apply our approach to the German-Dutch Vecht river catchment, which is characterized by high livestock densities. Results show a VA mass load decrease larger than 99% for all substances under investigation, from their administration to surface water emission. Due to metabolization in the body, degradation during manure storage and degradation in soil, VA loads are reduced by 45%, 80% and 90% on average, respectively. While amoxicillin and sulfamethazine dissipate quickly after field application, significant fractions of doxycycline, oxytetracycline and tetracycline accumulate in the soil. The overall Vecht catchment's GWF is estimated at 250,000 m³ yr^-1, resulting from doxycycline (81% and 19% contribution from the German and Dutch catchment part respectively). Uncertainty ranges of several orders of magnitude, as well as several remaining limitations to the presented IMA, underscore the importance to further develop and refine the approach.

Performance of full scale constructed wetlands in removing antibiotics and antibiotic resistance genes

Additional treatment of wastewater, such as constructed wetlands (CWs), is a possible solution to reduce the discharge of antibiotics and antibiotic resistance genes (ARGs) from households and industry to the environment. This study aims to investigate the occurrence and removal of antibiotics and ARGs by two full scale CWs operated at different hydraulic retention times (HRT), namely 1 day and 3 days. Both CWs were receiving the same wastewater treatment plant (WWTP) effluent. Temporally and spatially distributed sampling of water and sediment was conducted for one year and samples were analyzed for antibiotics and ARGs by using LC-MS/MS and qPCR. Results showed that both CWs removed antibiotics significantly with a comparable overall removal of 28%-100%, depending on the type of antibiotics. However, some of the antibiotics showed higher concentration after the CW treatment. Five antibiotics (tiamulin, tylosin, oxytetracycline, sulfamethoxazole and trimethoprim) were the most abundant (>1500 ng/l on average) in winter. Meanwhile, ermB was the most abundant (average of 5.0 log) in winter compared to summer (average of 3.5 log). Other ARGs did not show a significant increase or decrease between winter and summer. ARGs were removed from the wastewater by 0.8 to 1.5 log. The HRT did not influence the removal of either the antibiotics or the ARGs. A strong correlation was found between sul genes and intI1. The results also revealed a positive and a negative relationship from sampling point 1 to sampling point 5: a positive relation between abundance of antibiotics, ARGs, and of NO₃-N, NH₄-N, TP, COD and a negative relation between antibiotics, ARGs and temperature. This relationship showed the effect between antibiotics and ARGs concentrations with physicochemical parameters and nutrients. The ability of CWs to reduce the input of micropollutants into the environment makes CWs a potential post treatment to WWTP.

A strategy to determine the fate of active chemical compounds in soil; applied to antimicrobially active substances

Data on the fate of chemical substances in the environment after e.g. manure application is mandatory input for risk assessment in perspective of a more circular biobased economy. Such fate studies include a persistence study to determine a half-life value and a mobility study. It is recognized that not only the native substance should be considered, but that also degradation products should be included that might exert a similar effect as the native substance. We report a tiered fate study strategy that starts with a persistence study. For non-persistent substances a study is performed to determine if degradation products have a similar effect as the native compound. If so, a procedure using high resolution mass spectrometry is suggested to identify the potentially active degradation products. Based on the outcomes, substances are divided into three categories: (I) persistent, (II) degradable to inactive products or (III) degradable to active products. Even though the priority is with category I and III, for all substances and possible degradation products a mobility study is proposed. The fate strategy is successfully applied to ten antimicrobially active substances originating from the tetracyclines, sulfonamides, diaminopyrimidines, fluoroquinolones, macrolides and lincosamides. The fluoroquinolones, tetracyclines and trimethoprim were relatively persistent. The sulfonamides, macrolides and lincomycin (the latter also depending on soil type) degraded relatively quickly. Tylosin A proved to degrade to antimicrobially active degradation products which were tentitatively identified as tylosin C, tylosin A acid, tylosin B acid and tylosin C acid.

Pharmaceuticals in edible crops irrigated with reclaimed wastewater: Evidence from a large survey in Israel

Pharmaceuticals and other contaminants of emerging concern (CECs) are continuously introduced into the agroecosystem via reclaimed wastewater irrigation, a common agricultural practice in water-scarce regions. Although reclaimed wastewater irrigated crops are sold and consumed, only limited information is available on the occurrence of pharmaceuticals and other CECs in edible produce. Here, we report data on CECs in irrigation water, soils, and crops collected from 445 commercial fields irrigated with reclaimed wastewater in Israel. The following produce were analyzed: leafy greens, carrot, potato, tomato, orange, tangerine, avocado, and banana. Pharmaceuticals and CECs were found in quantifiable levels in all irrigation water, soils, and plants (>99.6%). Leafy greens exhibited the largest number and the highest concentration of pharmaceuticals. Within the same crop, contamination levels varied due to wastewater source and quality of treatment, and soil characteristics. Anticonvulsants (carbamazepine, lamotrigine, and gabapentin) were the most dominant therapeutic group found in the reclaimed wastewater-soil-plant continuum. Antimicrobials were detected in ~85% of the water and soil samples, however they exhibited low detection frequencies and concentrations in produce. Irrigation with reclaimed wastewater should be limited to crops where the risk for pharmaceutical transfer to the food chain is minimal.

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.