Reduced persistence of the macrolide antibiotics erythromycin, clarithromycin and azithromycin in agricultural soil following several years of exposure in the field

Temporal dynamics of the soil resistome and microbiome irrigated with treated wastewater containing clarithromycin

Clarithromycin, a common antibiotic found in domestic wastewater, persists even after treatment and can transfer to soils when treated wastewater (TWW) is used for irrigation. This residual antibiotic may exert selection pressure, promoting the spread of antibiotic resistance. While Predicted No Effect Concentrations (PNECs) are used in liquid media to predict resistance risks, PNEC values for soils, especially for clarithromycin, are lacking. Thus, this study aimed to assess clarithromycin's fate and its concentration threshold affecting soil microbial communities and macrolide resistance genes. The study used a soil microcosm approach with TWW containing clarithromycin at concentrations of 0, 0.01, 0.1, 0.5, and 1 mg/kgdry soil over a three-month period. Results showed clarithromycin persisted with limited degradation, likely due to strong adsorption to soil particles. Two transformation products were identified: decladinose-CLA (abiotic degradation) and phosphate-CLA (bacterial phosphotransferase activity). Soil bacterial communities were more influenced by TWW than by clarithromycin itself, as its antimicrobial effect was reduced due to adsorption. While clarithromycin did not significantly affect the abundance of resistance genes like intl1, mphA, and ereA, concentrations above 0.01 mg/kg increased the ermB gene abundance during the first week. The mefA gene (macrolide efflux pump) showed a hormetic effect: low doses (<0.1 mg/kg) increased gene abundance, while higher doses (>0.5 mg/kg) inhibited gene transfer or the bacteria carrying it. This study performed under controlled conditions provided insights into antibiotic resistance dynamics in soils exposed to clarithromycin, highlighting key concentration thresholds influencing resistance spread in soils.

Veterinary tetracycline residues: Environmental occurrence, ecotoxicity, and degradation mechanism

Tetracycline has been widely used in the intensive livestock and poultry breeding industry to prevent and treat infectious diseases or promote animal growth. Usually, about 40.0-90.0% of tetracycline is excreted in the form of original drugs or metabolites and finally enters the surrounding water and soil, causing a series of eco-toxic effects. In this review, the toxic effects on plants, soil animals, and microorganisms are systematically reviewed. The migration and degradation mechanisms of tetracycline are emphasized, which are closely related to the physical and chemical properties of soil. In addition, the residual tetracycline in soil and water can be efficiently degraded by "plant-microorganism". Based on summarizing the current research progress, this review puts forward some important problems to be solved in the study of tetracycline residue and looks forward to the future research direction.

Influence of soil type on bacterial growth and tolerance to experimentally added human antibiotics

The human antibiotics cefuroxime (CXM) and azithromycin (AZI) are among the most commonly prescribed. A significant portion of both are excreted and has been detected in sewage treatment plant effluents. The increasing use of such effluents in crops for irrigation and as fertilisers poses a threat to soil microbiota because of the presence of antibiotics. The lack of studies on CXM and AZI in soils hinders our understanding of their potential toxic effects on soil bacterial communities and ecosystem services. This study significantly contributes to the literature by quantifying the toxicity of CXM and AZI at varying concentrations in 12 different crop soils and tracking their evolution over time. The study also examined whether antibiotic pressure led to the development of more tolerant bacterial communities. The results of this study are the values of the logarithm of the antibiotic concentration at which 50 % of bacterial growth is inhibited (Log IC50) and indicate that both antibiotics are toxic to soil bacteria. The direct toxicity of CXM (1 day after contamination) was higher (Log IC50: 0.9 = 7.9 mg kg-1) than that of AZI (Log IC50: 3.4 = 2362 mg kg-1). However, bacterial growth was less affected by CXM over time, whereas AZI remained toxic in some soils until day 42 (Log IC50: 3.2 = 1533 mg kg-1 and 3.4 = 2291 mg kg-1, respectively). The overall results indicate that selective pressure exerted by antibiotics generates antibiotic tolerance in soils, even at the lowest antibiotic concentration studied (7.8 mg kg-1). The general trend was to increase tolerance to higher antibiotic concentrations up to the highest concentration studied (2000 mg kg-1). However, the degree of tolerance developed was highly dependent on soil type. More studies should be conducted to quantitatively assess the toxic and tolerance-developing effects of antibiotics in soils. Such information will be valuable for identifying which antibiotics pose a threat to the soil microbiota and consequently to human health.

Effects of glyphosate on antibiotic resistance in soil bacteria and its potential significance: A review

The evolution and spread of antibiotic resistance are problems with important consequences for bacterial disease treatment. Antibiotic use in animal production and the subsequent export of antibiotic resistance elements in animal manure to soil is a concern. Recent reports suggest that exposure of pathogenic bacteria to glyphosate increases antibiotic resistance. We review these reports and identify soil processes likely to affect the persistence of glyphosate, antibiotic resistance elements, and their interactions. The herbicide molecular target of glyphosate is not shared by antibiotics, indicating that target-site cross-resistance cannot account for increased antibiotic resistance. The mechanisms of bacterial resistance to glyphosate and antibiotics differ, and bacterial tolerance or resistance to glyphosate does not coincide with increased resistance to antibiotics. Glyphosate in the presence of antibiotics can increase the activity of efflux pumps, which confer tolerance to glyphosate, allowing for an increased frequency of mutation for antibiotic resistance. Such effects are not unique to glyphosate, as other herbicides and chemical pollutants can have the same effect, although glyphosate is used in much larger quantities on agricultural soils than most other chemicals. Most evidence indicates that glyphosate is not mutagenic in bacteria. Some studies suggest that glyphosate enhances genetic exchange of antibiotic-resistance elements through effects on membrane permeability. Glyphosate and antibiotics are often present together in manure-treated soil for at least part of the crop-growing season, and initial studies indicate that glyphosate may increase abundance of antibiotic resistance genes in soil, but longer term investigations under realistic field conditions are needed. Although there are demonstratable interactions among glyphosate, bacteria, and antibiotic resistance, there is limited evidence that normal use of glyphosate poses a substantial risk for increased occurrence of antibiotic-resistant, bacterial pathogens. Longer term field studies using environmentally relevant concentrations of glyphosate and antibiotics are needed.

Impact of veterinary pharmaceuticals on environment and their mitigation through microbial bioremediation

Veterinary medications are constantly being used for the diagnosis, treatment, and prevention of diseases in livestock. However, untreated veterinary drug active compounds are interminably discharged into numerous water bodies and terrestrial ecosystems, during production procedures, improper disposal of empty containers, unused medication or animal feed, and treatment procedures. This exhaustive review describes the different pathways through which veterinary medications enter the environment, discussing the role of agricultural practices and improper disposal methods. The detrimental effects of veterinary drug compounds on aquatic and terrestrial ecosystems are elaborated with examples of specific veterinary drugs and their known impacts. This review also aims to detail the mechanisms by which microbes degrade veterinary drug compounds as well as highlighting successful case studies and recent advancements in microbe-based bioremediation. It also elaborates on microbial electrochemical technologies as an eco-friendly solution for removing pharmaceutical pollutants from wastewater. Lastly, we have summarized potential innovations and challenges in implementing bioremediation on a large scale under the section prospects and advancements in this field.

Persistence and evidence for accelerated biodegradation of streptomycin in agricultural soils

Some antibiotics are used for the treatment of various bacterial crop diseases, and there is a concern that this practice may represent a selection pressure that increases the reservoir of antibiotic resistance carried by bacteria in crop production systems. Since the 1950s the aminoglycoside antibiotic streptomycin has been widely used for the treatment of some bacterial crop diseases such as fire blight in apples and pears. Following application, the time that bacteria will be exposed to the antibiotic, and therefore the pressure for selection of resistance, will vary according to the environmental persistence of the antibiotic. In the present study, the dissipation of streptomycin was examined in soils supplemented with 5 mg streptomycin/kg soil and incubated for 21 days under laboratory conditions. The impact of two key rate-controlling variables, soil texture (sandy loam, loam, clay loam) and temperature (4, 20, 30 °C) on streptomycin persistence were explored. -Robust methods for streptomycin extraction and analysis by LC-MS/MS were developed. Streptomycin dissipation followed first order kinetics, with the time to dissipate 50 % of the parent compound (DT50) in soils of varying texture incubated at 20 °C ranging from about seven to 15 days. In contrast, the DT50 of streptomycin in autoclaved loam soil incubated at 20 °C was about 111 days. At 4 °C the DT50 ranged from 49 to 137 days. Under no incubation conditions were any extractable transformation products obtained. Streptomycin was dissipated significantly more rapidly in field soil that had a prior history of exposure to the antibiotic than in soil that did not. Taken together, these results indicate that streptomycin is amenable to biodegradation in agricultural soils with DT50s of several days when temperature is permissive.

Source apportionment and predictable driving factors contribute to antibiotics profiles in Changshou Lake of the Three Gorges Reservoir area, China

Lakes, crucial antibiotic reservoirs, lack thorough exploration of quantitative relationships between antibiotics and influencing factors. Here, we conducted a comprehensive year-long investigation in Changshou Lake within the Three Gorges Reservoir area, China. The concentrations of 21 antibiotics spanned 35.6-200 ng/L, 50.3-348 ng/L and 0.57-57.9 ng/g in surface water, overlying water and sediment, respectively. Compared with abundant water period, surface water and overlying water displayed significantly high antibiotic concentrations in flat and low water periods, while sediment remained unchanged. Moreover, tetracyclines, fluoroquinolones and erythromycin posed notable risks to algae. Six primary sources were identified using positive matrix factorization model, with aquaculture contributing 21.2%, 22.7% and 25.4% in surface water, overlying water and sediment, respectively. The crucial predictors were screened through machine learning, redundancy analysis and Mantel test. Our findings emphasized the pivotal roles of water quality parameters, including water temperature (WT), pH, dissolved oxygen, electrical conductivity, inorganic anions (NO3⁻, Cl⁻ and F⁻) and metal cations (Ca, Mg, Fe, K and Cr), with WT influencing greatest. Total nitrogen (TN), cation exchange capacity, K, Al and Cd significantly impacted sediment antibiotics, with TN having the most pronounced effect. This study can promise valuable insights for environmental planning and policies addressing antibiotic pollution.

Antibiotics soil-solution chemistry: A review of environmental behavior and uptake and transformation by plants

The increased use of antibiotics by humans for various purposes has left the environment polluted. Antibiotic pollution remediation is challenging because antibiotics exist in trace amounts and only highly sensitive detection techniques could be used to quantify them. Nevertheless, their trace quantity is not a hindrance to their transfer along the food chain, causing sensitization and the development of antibiotic resistance. Despite an increase in the literature on antibiotic pollution and the development and transfer of antibiotic-resistant genes (ARGs), little attention has been given to the behavior of antibiotics at the soil-solution interface and how this affects antibiotic adsorption-desorption interactions and subsequent uptake and transformation by plants. Thus, this review critically examines the interactions and possible degradation mechanisms of antibiotics in soil and the link between antibiotic soil-solution chemistry and uptake by plants. Also, different factors influencing antibiotic mobility in soil and the transfer of ARGs from one organism to another were considered. The mechanistic and critical analyses revealed that: (a) the charge characteristics of antibiotics at the soil-root interface determine whether they are adsorbed to soil or taken up by plants; (b) antibiotics that avoid soil colloids and reach soil pore water can be absorbed by plant roots, but their translocation to the stem and leaves depends on the ionic state of the molecule; (c) few studies have explored how plants adapt to antibiotic pollution and the transformation of antibiotics in plants; and (d) the persistence of antibiotics in cropland soils can be influenced by the content of soil organic matter, coexisting ions, and fertilization practices. Future research should focus on the soil/solution-antibiotic-plant interactions to reveal detailed mechanisms of antibiotic transformation by plants and whether plant-transformed antibiotics could be of environmental risk.

Tracing COVID-19 drugs in the environment: Are we focusing on the right environmental compartment?

The Coronavirus Disease 2019 (COVID-19) pandemic led to over 770 million confirmed cases, straining public healthcare systems and necessitating extensive and prolonged use of synthetic chemical drugs around the globe for medical treatment and symptom relief. Concerns have arisen regarding the massive release of active pharmaceutical ingredients (APIs) and their metabolites into the environment, particularly through domestic sewage. While discussions surrounding this issue have primarily centered on their discharge into aquatic environments, particularly through treated effluent from municipal wastewater treatment plants (WWTPs), one often overlooked aspect is the terrestrial environment as a significant receptor of pharmaceutical-laden waste. This occurs through the disposal of sewage sludge, for instance, by applying biosolids to land or non-compliant disposal of sewage sludge, in addition to the routine disposal of expired and unused medications in municipal solid wastes. In this article, we surveyed sixteen approved pharmaceuticals for treating COVID-19 and bacterial co-infections, along with their primary metabolites. For this, we delved into their physiochemical properties, ecological toxicities, environmental persistence, and fate within municipal WWTPs. Emphasis was given on lipophilic substances with log Kow >3.0, which are more likely to be found in sewage sludge at significant factions (25.2%-75.0%) of their inputs in raw sewage and subsequently enter the terrestrial environment through land application of biosolids, e.g., 43% in the United States and as high as 96% in Ireland or non-compliant practices of sewage sludge disposal in developing communities, such as open dumping and land application without prior anaerobic digestion. The available evidence underscores the importance of adequately treating and disposing of sewage sludge before its final disposal or land application in an epidemic or pandemic scenario, as mismanaged sewage sludge could be a significant vector for releasing pharmaceutical compounds and their metabolites into the terrestrial environment.

Dissipation of twelve organic micropollutants in three different soils: Effect of soil characteristics and microbial composition

The dissipation kinetics and half-lives of selected organic micropollutants, including pharmaceuticals and others, were systematically investigated and compared among different soil types. While some pollutants (e.g., atorvastatin, valsartan, and bisphenol S) disappeared rapidly in all the tested soils, many of them (e.g., telmisartan, memantine, venlafaxine, and azithromycin) remained persistent. Irrespective of the soil characteristics, venlafaxine showed the lowest dissipation kinetics and the longest half-lives (250 to approximately 500 days) among the stable compounds. The highest first and second-order kinetics were, however, recorded for valsartan (k1; 0.262 day-1) and atorvastatin (k2; 33.8 g μg-1 day-1) respectively. Nevertheless, more than 90% (i.e., DT90) of all the rapidly dissipated compounds (i.e., atorvastatin, bisphenol S, and valsartan) disappeared from the tested soils within a short timescale (i.e., 5-36 days). Dissipation of pollutants that are more susceptible to microbial degradation (e.g., atorvastatin, bisphenol S, and valsartan) seems to be slower for soils possessing the lowest microbial biomass C (Cmic) and total phospholipid fatty acids (PLFAtotal), which also found statistically significant. Our results revealing the persistence of several organic pollutants in agricultural soils, which might impact the quality of these soils, the groundwater, and eventually on the related biota, is of high environmental significance.

Interactions of anthelmintic veterinary drugs with the soil microbiota: Toxicity or enhanced biodegradation?

Anthelmintic (AH) compounds are used to control gastrointestinal nematodes (GINs) in livestock production. They are only partially metabolized in animals ending in animal excreta whose use as manures leads to AH dispersal in agricultural soils. Once in soil, AHs interact with soil microorganisms, with the outcome being either detrimental, or beneficial. We aimed to disentangle the mechanisms of these complex interactions. Two soils previously identified as « fast » or « slow», regarding the degradation of albendazole (ABZ), ivermectin (IVM), and eprinomectin (EPM), were subjected to repeated applications at two dose rates (1, 2 mg kg-1and 10, 20 mg kg-1). We hypothesized that this application scheme will lead to enhanced biodegradation in «fast » soils and accumulation and toxicity in «slow » soils. Repeated application of ABZ resulted in different transformation pathways in the two soils and a clear acceleration of its degradation in the «fast » soil only. In contrast residues of IVM and EPM accumulated in both soils. ABZ was the sole AH that induced a consistent reduction in the abundance of total fungi and crenarchaea. In addition, inhibition of nitrification and reduction in the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) by all AHs was observed, while commamox bacteria were less responsive. Amplicon sequencing analysis showed dose-depended shifts in the diversity of bacteria, fungi, and protists in response to AHs application. ABZ presented the most consistent effect on the abundance and diversity of most microbial groups. Our findings provide first evidence for the unexpected toxicity of AHs on key soil microbial groups that might have to be considered in a regulatory context.

Biodegradation of COVID19 antibiotic; azithromycin and its impact on soil microbial community in the presence of phenolic waste and with temperature variation

The increase in using antibiotics, especially Azithromycin have increased steadily since the beginning of COVID19 pandemic. This increase has led to its presence in water systems which consequently led to its presence upon using this water for irrigation. The aim of the present work is to study the impact of irrigation using Azithromycin containing water on soil microbial community and its catabolic activity in the presence of phenolic wastes as compost. Wild berry, red grapes, pomegranate, and spent tea waste were added to soil and the degradation was monitored after 5 and 7 days at ambient and high temperatures. The results obtained show that at 30 °C, soil microbial community collectively was able to degrade Azithromycin, while at 40 °C, addition of spent tea as compost was needed to reach higher degradation. To ensure that the degradation was biotic and depended on degradation by indigenous microflora, a 25 kGy irradiation dose was used to kill the microorganisms in the soil and this was used as negative control. The residual antibiotic was assayed using UV spectroscopy and High Performance Liquid Chromatography (HPLC). Indication of Azithromycin presence was studied using Fourier Transform Infrared Spectroscopy (FTIR) peaks and the same pattern was obtained using the 3 used detection methods, the ability to assign the peaks even in the presence of soil and not to have any overlaps, gives the chance to study this result in depth to prepare IR based sensor for quick sensing of antibiotic in environmental samples.

Urbanization-land-use interactions predict antibiotic contamination in soil across urban-rural gradients

Antibiotics ubiquitously occur in soils and pose a potential threat to ecosystem health. Concurrently, urbanization and land-use intensification have transformed soil ecosystems, but how they affect antibiotic contamination remain largely unknown. Therefore, we profiled a broad-scale pattern of antibiotics in soil from agricultural lands and green spaces across urbanization gradients, and explored the hypothetical models to verify the effects of urbanization and land-use intensity on antibiotic contamination. The results showed that antibiotic concentrations and seasonality were higher in agricultural soil than in green spaces, which respectively showed linear or hump-shaped declines along with the increasing distance to urban centers. However, the response of antibiotic pollution to land-use intensity depended strongly on the urbanization level. More importantly, interactions between urbanization and land-use explained, on average, 59.6 % of the variation in antibiotic concentrations in soil across urbanization gradients. The proposed interactions can predict the non-linear changes in soil vulnerability to antibiotic contamination. Our study revealed that the urbanization can modulate the effects of land-use intensity on antibiotic concentration and seasonality in the soil environment, and that there is high stress on peri-urban soil ecosystems due to ongoing land-use changes arising from rapid urbanization processes.

Co-composting of cattle manure and wheat straw covered with a semipermeable membrane: organic matter humification and bacterial community succession

Semipermeable membrane-covered composting is one of the most commonly used composting technologies in northeast China, but its humification process is not yet well understood. This study employed a semipermeable membrane-covered composting system to detect the organic matter humification and bacterial community evolution patterns over the course of agricultural waste composting. Variations in physicochemical properties, humus composition, and bacterial communities were studied. The results suggested that membrane covering improved humic acid (HA) content and degree of polymerization (DP) by 9.28% and 21.57%, respectively. Bacterial analysis indicated that membrane covering reduced bacterial richness and increased bacterial diversity. Membrane covering mainly affected the bacterial community structure during thermophilic period of composting. RDA analysis revealed that membrane covering may affect the bacterial community by altering the physicochemical properties such as moisture content. Correlation analysis showed that membrane covering activated the dominant genera Saccharomonospora and Planktosalinus to participate in the formation of HS and HA in composting, thus promoting HS formation and its structural complexity. Membrane covering significantly reduced microbial metabolism during the cooling phase of composting.

Simultaneous determination of erythromycin and its transformation products in treated erythromycin fermentation residue and amended soil

Erythromycin fermentation residue (EFR) is a solid waste generated from the fermentation process of erythromycin A production. Some byproducts are produced during the fermentation process of erythromycin A production, and erythromycin A can also undergo hydrolysis and biodegradation reactions in the environment with the formation of transformation products. Herein, an accurate analytical method was established and validated to quantify erythromycin A, two byproducts and five hydrolysis or biodegradation products, in solid or semi-solid media of waste EFR and the amended soil. The method mainly included ultrasonic solvent extraction, solid phase extraction, and ultra-performance liquid chromatography-tandem mass spectrometry quantification. All analytes could be effectively extracted in a single process, and the recoveries ranged from 76% to 122% for different matrices. Low matrix effects and excellent precision were achieved by optimizing the mass spectrometry parameters, extraction solution, number of extractions and eluent. This method was applied to evaluate the residual analytes in EFR, treated EFR after industrial-scale hydrothermal treatment, and the subsequent soil application. Seven analytes were detected in the EFR, while six were found in the treated EFR and amended soils. The concentration of erythromycin A in EFR was 1,629 ± 100 mg/kg·TS, and the removal efficiency of hydrothermal treatment (180 °C, 60 min) was about 99.6%. Three hydrolysis products were the main residuals in treated EFR, with anhydroerythromycin A showing the highest concentration. The concentrations of the analytes in soil ranged from 2.17 ± 1.04 to 92.33 ± 20.70 μg/kg·TS, and anhydroerythromycin A contributed 65%-77% of the total concentration. Erythromycin B, a byproduct, was still detected in soil. This work provides an accurate analytical method which would be useful to evaluate the potential risk of byproducts and transformation products of erythromycin A in environment.

A critical review on retaining antibiotics in liquid digestate: Potential risk and removal technologies

Substantial levels of antibiotics remain in liquid digestate, posing a significant threat to human safety and the environment. A comprehensive assessment of residual antibiotics in liquid digestate and related removal technologies is required. To this end, this review first evaluates the potential risks of the residual antibiotics in liquid digestate by describing various anaerobic digestion processes and their half-lives in the environment. Next, emerging technologies for removing antibiotics in liquid digestate are summarized and discussed, including membrane separation, adsorption, and advanced oxidation processes. Finally, this study comprehensively and critically discusses these emerging technologies' prospects and challenges, including techno-economic feasibility and environmental impacts.

Azithromycin Adsorption onto Different Soils

The antibiotic azithromycin (AZM) is one of the most persistent in the environment, with potential to cause serious health and environmental problems. As some polluting discharges containing this antibiotic can reach the soil, it is clearly relevant determining the ability of soils with different characteristics to retain it. In this research, AZM adsorption and desorption were studied for a variety of soils, using batch-type experiments. The results show that, at low doses of antibiotic added (less than or equal to 50 µmol L−1), the adsorption always reached 100%, while when higher concentrations were added (between 200 and 600 µmol L−1) the highest adsorption corresponded to soils with higher pH values. Adsorption data were fitted to the Linear, Langmuir and Freundlich models, with the latter showing the best fit, in view of the determination coefficient. No desorption was detected, indicating that AZM is strongly adsorbed to the soils evaluated, suggesting that the risks of environmental problems due to this contaminant are minimized for these edaphic media. These results can be considered relevant with respect to risk assessment and possible programming of measures aimed at controlling environmental contamination by emerging contaminants, especially from the group of antibiotics, and in particular from AZM.

Chemical similarity and machine learning-based approaches for the prediction of aquatic toxicity of binary and multicomponent pharmaceutical and pesticide mixtures against Aliivibrio fischeri

Different classes of chemicals are present in the environment as mixtures. Among them, pharmaceuticals and pesticides are of major concern due to their improper use and disposal, and subsequent additive and non-additive effects. To assess the environmental risk posed by the mixtures of pharmaceuticals and pesticides, a quantitative structure-activity relationship (QSAR) model has been developed in this study using the pEC₅₀ values of 198 binary and multi-component mixtures against the marine bacterium Aliivibrio fischeri. The developed partial least squares (PLS) model has been rigorously validated and proved to be a robust and extremely predictive one. To address the chances of overestimation of validation metrics, three cross-validation tests (mixtures out, compounds out, and everything out) have been applied, and the results were satisfactory. The use of simple 2-dimensional descriptors makes the prediction much quick, and also makes the model easily interpretable. A machine learning-based chemical read-across prediction has also been performed to justify the effectiveness of selected structural features in this study. In a nutshell, this study proves QSAR and chemical read-across as effective alternative approaches for the toxicity prediction of pharmaceutical and pesticide mixtures and also approves the use of mixture descriptors for modelling mixtures successfully.

Natural detoxification of antibiotics in the environment: A one health perspective

The extended concept of one health integrates biological, geological, and chemical (bio-geo-chemical) components. Anthropogenic antibiotics are constantly and increasingly released into the soil and water environments. The fate of these drugs in the thin Earth space ("critical zone") where the biosphere is placed determines the effect of antimicrobial agents on the microbiosphere, which can potentially alter the composition of the ecosystem and lead to the selection of antibiotic-resistant microorganisms including animal and human pathogens. However, soil and water environments are highly heterogeneous in their local composition; thus the permanence and activity of antibiotics. This is a case of "molecular ecology": antibiotic molecules are adsorbed and eventually inactivated by interacting with biotic and abiotic molecules that are present at different concentrations in different places. There are poorly explored aspects of the pharmacodynamics (PD, biological action) and pharmacokinetics (PK, rates of decay) of antibiotics in water and soil environments. In this review, we explore the various biotic and abiotic factors contributing to antibiotic detoxification in the environment. These factors range from spontaneous degradation to the detoxifying effects produced by clay minerals (forming geochemical platforms with degradative reactions influenced by light, metals, or pH), charcoal, natural organic matter (including cellulose and chitin), biodegradation by bacterial populations and complex bacterial consortia (including "bacterial subsistence"; in other words, microbes taking antibiotics as nutrients), by planktonic microalgae, fungi, plant removal and degradation, or sequestration by living and dead cells (necrobiome detoxification). Many of these processes occur in particulated material where bacteria from various origins (microbiota coalescence) might also attach (microbiotic particles), thereby determining the antibiotic environmental PK/PD and influencing the local selection of antibiotic resistant bacteria. The exploration of this complex field requires a multidisciplinary effort in developing the molecular ecology of antibiotics, but could result in a much more precise determination of the one health hazards of antibiotic production and release.

Mobile resistome of microbial communities and antimicrobial residues from drinking water supply systems in Rio de Janeiro, Brazil

Antibiotic resistance genes (ARGs) are widespread in the environment due to the overuse of antibiotics and other pollutants, posing a threat to human and animal health. In this study, we evaluated antimicrobial residues, bacterial diversity and ARGs in two important watersheds, Guandu and São João, that supply drinking water to Rio de Janeiro city, Brazil. In addition, tap water samples were collected from three different cities in Rio de Janeiro State, including the metropolitan area of Rio de Janeiro city. Clarithromycin, sulfamethoxazole and azithromycin were found in untreated water and drinking water in all samples. A greater abundance of Proteobacteria was observed in Guandu and São João watersheds, with most of the sequences belonging to the Gammaproteobacteria class. A plasmidome-focused metagenomics approach revealed 4881 (Guandu), 3705 (São João) and 3385 (drinking water) ARGs mainly associated with efflux systems. The genes encoding metallo-β-lactamase enzymes (blaAIM, blaGIM, blaIMP, and blaVIM) were detected in the two watersheds and in drinking water samples. Moreover, we demonstrated the presence of the colistin resistance genes mcr-3 and mcr-4 (both watersheds) and mcr-9 (drinking water and Guandu) for the first time in Brazil. Our data emphasize the importance of introducing measures to reduce the disposal of antibiotics and other pollutants capable of promoting the occurrence and spread of the microbial resistome on aquatic environments and predicting possible negative impacts on human health.

Biodegradation of anthelmintics in soils: does prior exposure of soils to anthelmintics accelerate their dissipation?

Anthelmintics (AHs) control animal infections with gastrointestinal nematodes. They reach soil through animal faeces deposited on soils or through manuring. Although soil constitutes a major AH sink, we know little about the mechanisms controlling their soil dissipation. We employed studies with fumigated and non-fumigated soils collected from 12 sheep farms with a variable record of albendazole (ABZ), ivermectin (IVM) and eprinomectin (EPM) use. From each farm, we collected soils from inside small ruminant barn facilities (series A, high exposure) and the associated grazing pastures (series B, low exposure). We asked the following questions: (a) What is the role of soil microorganisms in AH dissipation? (b) Does repeated exposure of soils to AHs lead to their accelerated biodegradation? (c) Which soil physicochemical properties control AH dissipation? Soil fumigation significantly retarded ABZ (DT₅₀ 1.9 and 4.33 days), IVM (34.5 and 108.7 days) and EPM dissipation (30 and 121 days) suggesting a key role of soil microorganisms in AH dissipation. No significant acceleration in AH dissipation was evident in soils from units with a record of the administration of AHs or in soil series A vs series B, suggesting that the level of prior exposure was not adequate to induce their enhanced biodegradation. Significant positive and negative correlations of soil total organic carbon (TOC) and ABZ and IVM dissipation, respectively, were observed. Soil adsorption of AHs increased in the order IVM > ABZ > EPM. TOC controlled soil adsorption of IVM and EPM, but not of ABZ, in support of the contrasting effect of TOC on IVM and ABZ dissipation.

Responses of the Soil Bacterial Community, Resistome, and Mobilome to a Decade of Annual Exposure to Macrolide Antibiotics

Biosolids that are applied to agricultural soil as an organic fertilizer are frequently contaminated with pharmaceutical residues that have persisted during wastewater treatment and partitioned into the organic phase. Macrolide antibiotics, which serve as a critically important human medicine, have been detected within biosolids. To determine the impacts of macrolide antibiotics on soil bacteria, every year for a decade, a series of replicated field plots received an application of a mixture of erythromycin, clarithromycin, and azithromycin at a realistic (0.1 mg kg soil^-1) or an unrealistically high (10 mg kg soil^-1) dose or were left untreated. The effects of repeated antibiotic exposure on the soil bacterial community, resistome, mobilome, and integron gene cassette content were evaluated by 16S rRNA and integron gene cassette amplicon sequencing, as well as whole-metagenome sequencing. At the unrealistically high dose, the overall diversity of the resistome and mobilome was altered, as 21 clinically important antibiotic resistance genes predicted to encode resistance to 10 different antibiotic drug classes were increased and 20 mobile genetic element variants (tnpA, intI1, tnpAN, and IS91) were increased. In contrast, at the realistic dose, no effect was observed on the overall diversity of the soil bacterial community, resistome, mobilome, or integron gene cassette-carrying genes. Overall, these results suggest that macrolide antibiotics entrained into soil at concentrations anticipated with biosolid applications would not result in major changes to these endpoints. IMPORTANCE Biosolids, produced from the treatment of sewage sludge, are rich in plant nutrients and are a valuable alternative to inorganic fertilizer when applied to agricultural soil. However, the use of biosolids in agriculture, which are frequently contaminated with pharmaceuticals, such as macrolide antibiotics, may pose a risk to human health by selecting for antibiotic resistance genes that could be transferred to plant-based food destined for human consumption. The consequences of long-term, repeated macrolide antibiotic exposure on the diversity of the soil bacterial community, resistome, and mobilome were evaluated. At unrealistically high concentrations, macrolide antibiotics alter the overall diversity of the resistome and mobilome, enriching for antibiotic resistance genes and mobile genetic elements of concern to human health. However, at realistic antibiotic concentrations, no effect on these endpoints was observed, suggesting that current biosolids land management practices are unlikely to pose a risk to human health due to macrolide antibiotic contamination alone.

Effect of antibiotic mixtures on the characteristics of soluble microbial products and microbial communities in upflow anaerobic sludge blanket

Two upflow anaerobic sludge blanket reactors (UASBs) were used to investigate the effects of three antibiotic mixtures (erythromycin, sulfamethoxazole, and tetracycline) on reactor performance, soluble microbial products (SMPs) composition and microbial community. One reactor (UASB_antibiotics) was fed with antibiotic mixtures, whereas another reactor (UASB_control) was used as a control without the addition of antibiotic mixtures. Compared with those in UASB_control, UASB_antibiotics show lower chemical oxygen demand removal efficiency and biogas content. A higher removal efficiency of antibiotic mixtures was obtained in first few stages in UASB_antibiotics. The SMPs composition of effluent from the two reactors did not differ significantly, and the main components were protein-like substances, which produced higher fluorescence intensity in UASB_antibiotics. Gas chromatography-mass spectrometry analysis revealed that the main compounds identified as SMPs (<580 Da) were alkanes, aromatics and esters, with only 20% similarity of SMPs between UASB_antibiotics and UASB_control. Antibiotics had a significant effect on the microbial community structure. Notably, in UASB_control, hydrogenotrophic methanogens, key microorganisms in anaerobic digestion, had an obvious advantage at all stages compared with UASB_antibiotics, whereas acetoclastic methanogen exhibited the opposite pattern. The above results demonstrated that antibiotic mixtures influenced the effluent quality during anaerobic treatment of synthetic wastewater, resulting in changes in the microbial community structure. This study clarified the effect of antibiotic mixtures on the operation of UASBs. It could contribute to identifying potential strategies for improving effluent quality in anaerobic treatment.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Rhodococcus equi in horses

Rhodococcus equi (R. equi) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for horses in a previous scientific opinion. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9 and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR R. equi can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (10-66% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1 and 2 (Categories A and B; 5-10% and 10-33% probability of meeting the criteria, respectively), and the AHAW Panel is uncertain whether it meets the criteria in Sections 3, 4 and 5 (Categories C, D and E; 10-66% probability of meeting the criteria in all three categories). The animal species to be listed for AMR R. equi according to Article 8 criteria are mainly horses and other species belonging to the Perissodactyla and Artiodactyla orders.

Antibiotic fate in an artificial-constructed urban river planted with the algae Microcystis aeruginosa and emergent hydrophyte

The behavior and removal of six antibiotics, that is, azithromycin, clarithromycin, sulfathiazole, sulfamethoxazole, ciprofloxacin, and tetracycline, in an artificial-controllable urban river (ACUR) were investigated. The ACUR was constructed to form five artificial eco-systems by planting three emergent hydrophytes and Microcystis aeruginosa: (1) Control; (2) MA: M. aeruginosa only; (3) MA-J-C: M. aeruginosa combined with Juncus effusus and Cyperus alternifolius; (4) MA-C-A: M. aeruginosa combined with C. alternifolius and Acorus calamus L.; (5) MA-A-J: M. aeruginosa combined with A. calamus L. and J. effusus. The MA-C-A system achieved the best removal of azithromycin and clarithromycin after 15-day test with the final concentrations 0.92 and 0.83 μg/L. The contents of ciprofloxacin and tetracycline in sediment were highest, up to 1453 and 1745 ng/g. The antibiotic plant bioaccumulation was higher in roots rather than the shoots (stem and leaves). No target antibiotics were detected in algae cells. The combination of hybrid hydrophytes had a certain effect on the removal of antibiotics, and thus selecting appropriate hydrophytes in urban rivers could greatly improve water quality. The overall removal of six antibiotics was greatly improved by the ACUR containing the hybrid hydrophytes and the algae, indicating a synergistic effect on antibiotic removal. PRACTITIONER POINTS: Controllable-mobile artificial eco-systems were developed with emergent hydrophytes and M. aeruginosa. The M. aeruginosa + Cyperus alternifolius + Acorus calamus L. system removed azithromycin and clarithromycin most at the end of tests. Emergent hydrophytes and M. aeruginosa have a synergistic effect on the removal of antibiotics. The combination of emergent hydrophytes did play an important role in the removal of antibiotics. The artificial eco-systems containing the hybrid hydrophytes and the algae could greatly improve the overall removal of antibiotics.

Ecotoxicological risk assessment of wastewater irrigation on soil microorganisms: Fate and impact of wastewater-borne micropollutants in lettuce-soil system

The implementation of the new Water Reuse regulation in the European Union brings to the forefront the need to evaluate the risks of using wastewater for crop irrigation. Here, a two-tier ecotoxicological risk assessment was performed to evaluate the fate of wastewater-borne micropollutants in soil and their ecotoxicological impact on plants and soil microorganisms. To this end, two successive cultivation campaigns of lettuces were irrigated with wastewater (at agronomical dose (not spiked) and spiked with a mixture of 14 pharmaceuticals at 10 and 100 µg/L each) in a controlled greenhouse experiment. Over the two cultivation campaigns, an accumulation of PPCPs was observed in soil microcosms irrigated with wastewater spiked with 100 μg/L of PPCPs with the highest concentrations detected for clarithromycin, hydrochlorothiazide, citalopram, climbazole and carbamazepine. The abundance of bacterial and fungal communities remained stable over the two cultivation campaigns and was not affected by any of the irrigation regimes applied. Similarly, no changes were observed in the abundance of ammonium oxidizing archaea (AOA) and bacteria (AOB), nor in clade A of commamox no matter the cultivation campaign or the irrigation regime considered. Only a slight increase was detected in clade B of commamox bacteria after the second cultivation campaign. Sulfamethoxazole-resistant and -degrading bacteria were not impacted either. The irrigation regimes had only a limited effect on the bacterial evenness. However, in response to wastewater irrigation the structure of soil bacterial community significantly changed the relative abundance of Acidobacteria, Chloroflexi, Verrucomicrobia, Beta-, Gamma- and Deltaprotebacteria. Twenty-eight operational taxonomic units (OTUs) were identified as responsible for the changes observed within the bacterial communities of soils irrigated with wastewater or with water. Interestingly, the relative abundance of these OTUs was similar in soils irrigated with either spiked or non-spiked irrigation solutions. This indicates that under both agronomical and worst-case scenario the mixture of fourteen PPCPs had no effect on soil bacterial community.

Characterization and mechanism analysis of tylosin biodegradation and simultaneous ammonia nitrogen removal with strain Klebsiella pneumoniae TN-1

A novel bacterial strain that exhibited a high capacity for the simultaneous degradation and removal of tylosin and ammonia nitrogen, respectively, was isolated from tylosin fermentation dregs (TFDs) and identified as Klebsiella pneumoniae TN-1. The removal efficiencies of tylosin and ammonia nitrogen reached 95.31% and 83.26%, respectively, at initial concentrations of 300 mg/L for both. Three identified intermediates with less toxicity indicated that de-sugarization and hydrolysis were the proposed biodegradation pathways. The results also suggested that strain TN-1 could reduce nitrogen loss by transforming ammonium into nitrate nitrogen according to the transcriptional expression of nitrogen transformation-related genes and the activities of functional enzymes. Moreover, strain TN-1 effectively reduced ammonia volatilization by 65.20% and facilitated tylosin degradation, with a maximum removal efficiency of 57.35% in the simulated fermentation process of TFDs. This work provides an efficient bioaugmentation for simultaneous antibiotic degradation and nitrogen conservation during the composting process.

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.

The Effect of Clarithromycin Toxicity on the Growth of Bacterial Communities in Agricultural Soils

The presence of antibiotics in different environmental matrices is a growing concern. The introduction of antibiotics into the soil is mainly due to sewage treatment plants. Once in the soil, antibiotics may become toxic to microbial communities and, as a consequence, can pose a risk to the environment and human health. This study evaluates the potential toxicity of the antibiotic clarithromycin (CLA) in relation to the bacterial community of 12 soils with different characteristics. Bacterial community growth was evaluated in soils spiked in the laboratory with different concentrations of CLA after 1, 8, and 42 incubation days. The results indicated that the addition of clarithromycin to the soil may cause toxicity in the bacterial communities of the soil. In addition, it was observed that toxicity decreases between 1 and 8 incubation days, while the bacterial community recovers completely in most soils after 42 incubation days. The results also show that soil pH and effective cation exchange capacity may influence CLA toxicity.

Impact of long-term irrigation with municipal reclaimed wastewater on the uptake and degradation of organic contaminants in lettuce and leek

A two years drip irrigation of lettuce and leek crops with treated municipal wastewater without and with spiking with fourteen wastewater relevant contaminants at 10 μg/L concentration level was conducted under greenhouse cultivation conditions to investigate their potential accumulation in soil and leaves and to assess human health related risks. Lettuce and leek crops were selected as a worse-case scenario since leafy green vegetable has a high potential for organic contaminants uptake. The results revealed limited accumulation of contaminants in soil and plant leaves, their concentration levels being in the range of 1-30 ng/g and 1-660 ng/g range in soil and leaves, respectively. This was likely related to abiotic and biotic transformation or simply binding processes in soil, which limited contaminants plant uptake. This assumption was underpinned by studies of the enantiomeric fractionation of chiral compounds (e.g. climbazole and metoprolol) in soil as pieces of evidence of biodegradation and by the identification of transformation products or metabolites in leaves by means of liquid chromatography - high resolution - mass spectrometry using a suspect screening workflow. The high bioconcentration factors were not limited to compounds with intermediate Dow (100 to 1000) such as carbamazepine but also observed for hydrophilic compounds such as clarithromycin, hydrochlorothiazide and the food additives acesulfame and sucralose. This result assumed that accumulation was not only driven by passive processes (e.g. lipoidal diffusion through lipid bilayer cell membranes or Casparian strip) but might be supported by carrier-mediated transporters. As a whole, this study confirmed earlier reports on the a de minimis human health risk related to the consumption of raw leafy green vegetable irrigated with domestic TWW containing organic contaminants residues.

The impact and fate of clarithromycin in anaerobic digestion of waste activated sludge for biogas production

Clarithromycin retained in waste activated sludge (WAS) inevitably enters the anaerobic digestion system. So far, the complex impacts and fate of clarithromycin in continuous operated WAS anaerobic digestion system are still unclear. In this study, two semi-continuous long-term reactors were set up to investigate the effect of clarithromycin on biogas production and antibiotic resistance genes (ARGs) during WAS anaerobic digestion, and a batch test was carried out to explore the potential metabolic mechanism. Experimental results showed that clarithromycin at lower concentrations (i.e., 0.1 and 1.0 mg/L) did not affect biogas production, whereas the decrease in biogas production was observed when the concentration of clarithromycin was further increased to 10 mg/L. Correspondingly, the relative abundance of functional bacteria in WAS anaerobic digestion (i.e., Anaerolineaceae and Microtrichales) was reduced with long-term clarithromycin exposure. The investigation of ARGs suggested that the effect of methylation belonging to the target site modification played a critical role for the anaerobic microorganisms in the expression of antibiotic resistance, and ermF, played dominated ARGs, presented the most remarkable proliferation. In comparison, the role of efflux pump was weakened with a significant decrease of two detected efflux genes. During WAS anaerobic digestion, clarithromycin could be partially degraded into metabolites with lower antimicrobial activity including oleandomycin and 5-O-desosaminyl-6-O-methylerythronolide and other metabolites without antimicrobial activity.

Application of Erythromycin and/or Raoultella sp. Strain MC3 Alters the Metabolic Activity of Soil Microbial Communities as Revealed by the Community Level Physiological Profiling Approach

Erythromycin (EM), a macrolide antibiotic, by influencing the biodiversity of microorganisms, might change the catabolic activity of the entire soil microbial community. Hence, the goal of this study was to determine the metabolic biodiversity in soil treated with EM (1 and 10 mg/kg soil) using the community-level physiological profiling (CLPP) method during a 90-day experiment. In addition, the effect of soil inoculation with antibiotic-resistant Raoultella sp. strain MC3 on CLPP was evaluated. The resistance and resilience concept as well as multifactorial analysis of data was exploited to interpret the outcomes obtained. EM negatively affected the metabolic microbial activity, as indicated by the values of the CLPP indices, i.e., microbial activity expressed as the average well-color development (AWCD), substrate richness (R), the Shannon-Wiener (H) and evenness (E) indices and the AWCD values for the six groups of carbon substrate present in EcoPlates until 15 days. The introduction of strain MC3 into soil increased the degradative activity of soil microorganisms in comparison with non-inoculated control. In contrast, at the consecutive sampling days, an increase in the values of the CLPP parameters was observed, especially for EM-10 + MC3-treated soil. Considering the average values of the resistance index for all of the measurement days, the resistance of the CLPP indices and the AWCD values for carbon substrate groups were categorized as follows: E > H > R > AWCD and polymers > amino acids > carbohydrates > miscellaneous > amines > carboxylic acids. The obtained results suggest a low level of resistance of soil microorganisms to EM and/or strain MC3 at the beginning of the exposure time, but the microbial community exhibited the ability to recover its initial decrease in catabolic activity over the experimental period. Despite the short-term effects, the balance of the soil ecosystem may be disturbed.

Reclaimed wastewater as a viable water source for agricultural irrigation: A review of food crop growth inhibition and promotion in the context of environmental change

The geographical and temporal distribution of precipitation has and is continuing to change with changing climate. Shifting precipitation will likely require adaptations to irrigation strategies, and because 35% of rainfed and 60% of irrigated agriculture is within 20 km of a wastewater treatment plant, we expect that the use of treated wastewater (e.g., reclaimed wastewater) for irrigation will increase. Treated wastewater contains various organic and inorganic substances that may have beneficial (e.g., nitrate) or deleterious (e.g., salt) effects on plants, which may cause a change in global food productivity should a large change to treated wastewater irrigation occur. We reviewed literature focused on food crop growth inhibition or promotion resulting from exposure to xenobiotics, engineered nanoparticles, nitrogen, and phosphorus, metals, and salts. Xenobiotics and engineered nanoparticles, in nearly all instances, were detrimental to crop growth, but only at concentrations much greater than would be currently expected in treated wastewater. However, future changes in wastewater flow and use of these compounds and particles may result in phytotoxicity, particularly for xenobiotics, as some are present in wastewater at concentrations within approximately an order of magnitude of concentrations which caused growth inhibition. The availability of nutrients present in treated wastewater provided the greatest overall benefit, but may be surpassed by the detrimental impact of salt in scenarios where either high concentrations of salt are directly deleterious to plant development (rare) or in scenarios where soils are poorly managed, resulting in soil salt accumulation.

Impacts of multi-year field exposure of agricultural soil to macrolide antibiotics on the abundance of antibiotic resistance genes and selected mobile genetic elements

Exposure of environmental bacteria to antibiotics may be increasing the global resistome. Antibiotic residues are entrained into agricultural soil through the application of animal and human wastes, and irrigation with reclaimed water. The impact of a mixture of three macrolide antibiotics on the abundance of selected genes associated with antibiotic resistance and genetic mobility were determined in a long-term field experiment undertaken in London, Canada. Replicated plots received annual applications of a mixture of erythromycin, clarithromycin and azithromycin every spring since 2010. Each antibiotic was added directly to the soil at a concentration of either 0.1 or 10 mg kg soil^-1 and all plots were cropped to soybeans. By means of qPCR, no gene targets were enriched in soil exposed to the 0.1 mg kg soil^-1 dose compared to untreated control. In contrast, the relative abundance of several gene targets including int1, sul2 and mphE increased significantly with the annual exposure to the 10 mg kg soil^-1 dose. By means of high-throughput qPCR, numerous gene targets associated with resistance to aminoglycosides, sulfonamides, trimethoprim, streptomycin, quaternary ammonium chemicals as well as mobile genetic elements (tnpA, IS26 and IS6100) were detected in soil exposed to 10 mg kg soil^-1, but not the lower dose. Overall, exposure of soil to macrolide antibiotics increased the relative abundance of numerous gene targets associated with resistance to macrolides and other antibiotics, and mobile genetic elements. This occurred at an exposure dose that is unrealistically high, but did not occur at the lower more realistic exposure dose.

Assessing the effects of tylosin fermentation dregs as soil amendment on macrolide antibiotic resistance genes and microbial communities: Incubation study

Tylosin fermentation dregs (TFDs) are biosolid waste of antibiotics tylosin production process which contain nutritious components and may be recycled as soil amendments. However, the specific ecological safety of TFDs from the perspective of bacterial resistance in soil microenvironment is not fully explored. In the present study, a series of replicated lab-scale work were performed using the simulated fertilization to gain insight into the potential environmental effects and risks of macrolide antibiotic resistance genes (ARGs) and the soil microbial communities composition via quantitative PCR and 16S rRNA sequencing following the TFDs land application as the soil amendments. The results showed that bio-processes might play an important role in the decomposition of tylosin which degraded above 90% after 20 days in soil. The application of TFDs might induce the development of antibiotic-resistant bacteria, change soil environment and reduce the microbial diversity. Though the abundances of macrolide ARGs exhibited a decreasing trend following the tylosin degradation, other components in TFDs may have a lasting impact on both macrolide ARGs abundance and soil bacterial communities. Thus, this study pointed out the fate of TFDs on soil ecological environment when directly applying into soil, and provide valuable scientific basis for TFDs management.

Effect of biosolids characteristics on retention and release behavior of azithromycin and ciprofloxacin

Azithromycin (AZ) and ciprofloxacin (CIP) are commonly prescribed antibiotics frequently detected in municipal biosolids and identified by the USEPA as contaminants of emerging concern. The land application of municipal biosolids is an agronomically beneficial practice but is also a potential pathway of CIP and AZ release into the environment. Understanding retention-release behavior is crucial for assessing the environmental fate of and risks from land-applied biosolids-borne target antibiotics. Here, we used batch equilibrations to assess retention and release of environmentally relevant concentrations of CIP and AZ in ten different biosolids. The biosolids included Class A and Class B materials with a range of physiochemical characteristics (e.g. pH, cation exchange capacity (CEC), organic matter content (OM), and iron (Fe) and aluminum (Al)) expected to influence retention and release of AZ and CIP. Retention was linear (R² > 0.99 for AZ and >0.96 for CIP) and sorption coefficients (K_d) ranged from 52 to 370 L kg^-1 for AZ and 430-2300 L kg^-1 for CIP. Desorption also varied but was highly hysteretic, with hysteresis coefficients (H) ranging 0.01 to 0.15 for AZ and ≤0.01 for CIP, suggesting limited bioaccessibility. The penalized and shrinkage method least absolute shrinkage and selection operator (LASSO) was used to produce models describing AZ and CIP sorption behavior based on any given biosolids physiochemical characteristics. Multiple linear regression analysis linked AZ sorption behavior to total Fe content, likely due to a predisposition of AZ to participate in reactions with in situ Fe species. CIP sorption behavior was linked to oxalate extractable Al and total phosphorus (P) content, suggesting CIP bonding with amorphous forms of Al and a potential relationship between CIP sorption to biosolids and biosolids production processes, as manifested by correlation of CIP sorption with total P content.

Zoonosis: An Emerging Link to Antibiotic Resistance Under "One Health Approach"

Current scenario in communicable diseases has generated new era that identifies the "One health" approach to understand the sharing and management of etiological agents with its impact on ecosystem. Under this context the relevance of zoonotic diseases generates major concern. The indiscriminate and higher use of antibiotics in animal husbandry creates substantial pressure on the gut microbiome for development of resistance due to shorter generation time and high density. Thus, gut works as a bioreactor for the breeding of ARBs in this scenario and are continuously released in different niches. These ARBs transfer resistance genes among native flora through horizontal gene transfer events, vectors and quorum sensing. About 60% of infectious diseases in human are caused by zoonotic pathogens have potential to carry ARGs which could be transmitted to humans. The well documented zoonotic diseases are anthrax cause by Bacillus anthracis, bovine tuberculosis by Mycobacterium tuberculosis, brucellosis by Brucella abortus, and hemorrhagic colitis by Escherichia coli. Similarly, most of the antibiotics are not completely metabolized and released in unmetabolized forms which enters the food chain and affect various ecological niches through bioaccumulation. The persistence period of antibiotics ranges from < 1 to 3466 days in environment. The consequences of misusing the antibiotic in livestock and their fate in various ecological niches have been discussed in this review. Further the light sheds on antibiotics persistence and it biodegradation through different abiotic and biotic approaches in environment. The knowledge on personnel hygiene and strong surveillance system for zoonotic disease including ARBs transmission, prevention and control measures should be established to regulate the spread of AMR in the environment and subsequently to the human being through a food web.

Assessment of bacterial and fungal communities in a full-scale thermophilic sewage sludge composting pile under a semipermeable cover

Bacterial and fungal communities in a full-scale composting pile were investigated, with sewage sludge and a vegetal bulking agent as starting materials. Bacillales and Actinomycetales were predominant throughout the process, showing significant abundance. Ascomycota was the predominant fungal phylum during the thermophilic phase, with a shift to Basidiomycota at the end of the process. The bulking material was the principal contributor to both communities by the end of the process, with a signal above 50%. The presence of genera, such as Pedomicrobium, Ureibacillus and Tepidimicrobium at the end of the process, and Chaetomium and Arthrographis in the maturation phase, showed an inverse correlation with indicators of organic matter stabilisation. A semipermeable cover was an effective technology for excluding pathogens. These results indicate that changes in the microbial population and their interrelation with operational variables could represent a useful tool for monitoring composting processes.

Occurrence and Behavior of Macrolide Antibiotics in Municipal Wastewater Treatment: Possible Importance of Metabolites, Synthesis Byproducts, and Transformation Products

A one-year study on the occurrence and fate of macrolide antibiotics and their metabolites, synthesis byproducts, and transformation products (TPs) was performed in the wastewater treatment plant of the city of Zagreb (Croatia). The target compounds were found in all analyzed influent and effluent samples with the total concentrations of azithromycin-, clarithromycin-, and erythromycin-related compounds reaching up to 25, 12, and 0.25 μg/L, respectively. The most prominent individual constituents were the parent macrolides azithromycin and clarithromycin. However, a substantial contribution of their derivatives, formed by deglycolysation and microbial phosphorylation, was also detected. In addition, widespread presence of several linearized nontarget TPs was confirmed for the first time in real wastewater samples by suspect screening analysis. Complex characterization of macrolide-derived compounds enabled decoupling of industrial and therapeutic sources from the in situ transformations. Due to the high inputs and incomplete removal and/or formation of several TPs during the conventional wastewater treatment, the average mass load of azithromycin-related compounds in secondary effluents exceeded 3.0 g/day/1000 inhabitants. This is the first study to reveal the importance of metabolites, byproducts, and TPs for the overall mass balance of macrolide antibiotics in urban wastewater systems.

Antibiotics in the Soil Environment-Degradation and Their Impact on Microbial Activity and Diversity

Antibiotics play a key role in the management of infectious diseases in humans, animals, livestock, and aquacultures all over the world. The release of increasing amount of antibiotics into waters and soils creates a potential threat to all microorganisms in these environments. This review addresses issues related to the fate and degradation of antibiotics in soils and the impact of antibiotics on the structural, genetic and functional diversity of microbial communities. Due to the emergence of bacterial resistance to antibiotics, which is considered a worldwide public health problem, the abundance and diversity of antibiotic resistance genes (ARGs) in soils are also discussed. When antibiotic residues enter the soil, the main processes determining their persistence are sorption to organic particles and degradation/transformation. The wide range of DT50 values for antibiotic residues in soils shows that the processes governing persistence depend on a number of different factors, e.g., physico-chemical properties of the residue, characteristics of the soil, and climatic factors (temperature, rainfall, and humidity). The results presented in this review show that antibiotics affect soil microorganisms by changing their enzyme activity and ability to metabolize different carbon sources, as well as by altering the overall microbial biomass and the relative abundance of different groups (i.e., Gram-negative bacteria, Gram-positive bacteria, and fungi) in microbial communities. Studies using methods based on analyses of nucleic acids prove that antibiotics alter the biodiversity of microbial communities and the presence of many types of ARGs in soil are affected by agricultural and human activities. It is worth emphasizing that studies on ARGs in soil have resulted in the discovery of new genes and enzymes responsible for bacterial resistance to antibiotics. However, many ambiguous results indicate that precise estimation of the impact of antibiotics on the activity and diversity of soil microbial communities is a great challenge.

Veterinary pharmaceuticals and antibiotics in manure and slurry and their fate in amended agricultural soils: Findings from an experimental field site (Baix Empordà, NE Catalonia)

The fate and transport of 34 veterinary pharmaceuticals (PhACs) is investigated in swine slurry and dairy cattle manure-amended agricultural soils, from an experimental field site, by using both analytical and modelled data. Potential differences on PhACs fate, attributed to the application of distinct swine slurry fractions (total, solid, and liquid), are herein assessed for the first time. Surface and deep soil layers, up to a depth of 120 cm, were analyzed at different periods after an annual fertilization event. Using input data representing typical agricultural soil conditions and the PhACs concentration measured in organic fertilizers the transport of these pollutants was modelled for a period of 10 years, including the monitored annual fertilization event. Fluoroquinolone, tetracycline and pleuromutilin antibiotics, together with anti-helmintics and analgesic and anti-inflammatories, were detected in manure-amended soils, at average concentrations ranging from 0.078 to 150 μg/kg dw in surface layers, with the highest levels found in the fields fertilized with the swine slurry solid fraction. Even though severe disagreements were observed between experimental and simulated PhACs concentrations along the soil column, both approaches pointed out that target compounds strongly adsorb onto surface layers, showing limited mobility along the soil profile. Thus, repeated manure and slurry fertilizations will contribute in building up persistent PhACs residues in the uppermost layers of the soil, while leaching will be a minor process governing their fate towards the subsurface. The ecotoxicological risks posed by the occurrence of PhACs in soils were estimated to be low for terrestrial organisms. Nevertheless the antibiotic enrofloxacin showed some potential to induce negative effects to crops.

Bioavailability of biosolids-borne ciprofloxacin and azithromycin to terrestrial organisms: Microbial toxicity and earthworm responses

Information on bioavailability of two antibiotic TOrCs, ciprofloxacin (CIP) and azithromycin (AZ), to terrestrial organisms is severely limited, especially in the biosolids context. Responses of two terrestrial organisms, earthworms and microbes, to a range of environmentally relevant concentrations of biosolids-borne CIP and AZ were assessed in laboratory incubation studies involving ³H-labeled compounds. Earthworm assessments were based on the Earthworm Sub-chronic Toxicity Test (OCSPP 850.3100). Microbial impacts were assessed using respiration and reverse transcriptase-quantitative PCR (mRNA) analyses of nutrient (N and P) cycling genes as toxicity markers. Antibiotic extractability and stability during incubations were assessed using sequential extractions with CaCl₂, methanol:water, and accelerated solvent extraction and analyses using thin layer chromatography. Subsample combustion, in addition to sequential extraction, recovered nearly 100% of the added antibiotic. The two compounds persisted (estimated half-lives ≥ 3 y), but extractable fractions (especially of CIP) decreased over time. Neither biosolids-borne antibiotic significantly impacted overall respiration or N and P cycling. Microbial toxicity responses were minimal; complementary DNA (cDNA) concentrations of ammonia oxidizing bacterial genes were affected, but only initially. Similarly, earthworms showed no apparent response related to toxicity to environmentally relevant (and much greater) concentrations of biosolids-borne CIP and AZ. Earthworms, however, accumulated both compounds, and the bioaccumulation factor (BAF) values (dry weight basis) were ~4 (CIP) and ~7 (AZ) in depurated worms and ~20 (CIP and AZ) in un-depurated worms. The microbial and earthworm responses strongly to moderately correlated with "bioaccessible" fractions of the target TOrCs. The results suggest that biosolids-borne CIP and AZ toxicity to terrestrial microbes and earthworms is minimal, but there is a potential for target TOrC entry into ecological food web.

Occurrence of seventeen veterinary antibiotics and resistant bacterias in manure-fertilized vegetable farm soil in four provinces of China

This study focused on the occurrence of seventeen veterinary antibiotics and six resistant bacterias in soils from the vegetable farms fertilized with animal manure in China. Seventeen veterinary antibiotics, including sulfonamides, quinolones, tetracyclines, macrolides and amphenicols, were detected by high performance liquid chromatography/tandem mass spectrometer in all the 53 soil samples collected in four provinces during August 2016. The concentrations of target antibiotics in the soil samples ranged from not detectable to 415.00 μg/kg dry weight with the mean residual levels of the five classes followed order: tetracyclines (82.75 μg/kg) > quinolones (12.78 μg/kg) > macrolides (12.24 μg/kg) > sulfonamides (2.61 μg/kg) > amphenicols (0.06 μg/kg). Moreover, the highest antibiotic levels were found mainly in soil from organic vegetable farms. Risk assessment by using the methods of risk quotient, suggested that oxytetracycline, chlortetracycline, enrofloxacin and ciprofloxacin could pose severe ecological risk in sampled soils. Resistant strains were isolated in 30 samples, with Escherichia coli and Klebsiella pneumonia found the dominant bacterial hosts with resistance genes. Antibiotic resistance genes, including tetA, tetB, qnrS, oqxA, sul1, sul2, ermA and floR, were detected in the strains resistant to: tetracyclines, quinolones, sulfonamides, macrolides and amphenicols resistance, respectively. Overall, there was a correlation between the results of antibiotic risk assessment with the detection of resistance genes from isolated strains in the soils.

Performance evaluation of gaseous emissions and Zn speciation during Zn-rich antibiotic manufacturing wastes and pig manure composting

In this study, the co-composting performance of Zn-rich antibiotic manufacturing wastes (AMW) and pig manure (PM) was evaluated. Four treatments, representing 2.5%, 5%, 10% and 20% of AMW (of PM dry weight) and control without AMW, were established during composting. Results suggested that the temperature, pH, electrical conductivity, NH4+-N and germination index in end product met the maturity and sanitation requirement. More than 99% of residual antibiotic was removed. Compared with PM composting alone, the cumulative CH4 and N2O emissions in AMW composting increased by 13.46-79.00% and 10.78-65.12%, respectively. While the higher mixing ratios of AMW (10% and 20%) presented a negative impact on composing by inhibiting organic matter (OM) degradation and higher NH3 emissions. The AMW had highly bioavailable Zn, but the exchangeable faction of Zn significantly decreased with the composting progress.

Characteristics of removal of waste-water marking pharmaceuticals with typical hydrophytes in the urban rivers

The investigations on their variation and distribution of 13 called waste-water marking pharmaceuticals (WWMPs) were conducted under 4 hydrophyte conditions (without plants, with submerged aquatic plant (Myriophyllum verticillatum L.), emergent aquatic plant cattail (Typha orientalis Presl) and floating aquatic plant (Lemna minor L.)) in a simulated urban river system. By the calculation of mass balance, the quantitative distribution of WWMPs in water phase, sediment and plant tissues was identified, and the overall removal efficiencies of target pharmaceuticals in the whole system could be determined. Without plants, high persistence of atenolol (ATL) (97.7%), carbamazepine (CBM) (102.8%), clofibric acid (CLF) (101.8%) and ibuprofen (IBU) (80.9%) was detected in water phase, while triclosan (TCS) (53.5%) displayed strong adsorption affinity in sediment. The removal under the planted conditions was considerably raised, compared with no plant condition for most WWMPs. However, TCS did not show obvious differences among the hydrophyte conditions due to its strong adsorption affinity and high hydrophobicity. The relatively higher removal was found for the hydrophilic (logK_ow<1) or moderately hydrophobic (1<logK_ow<3) pharmaceuticals with submerged and emergent aquatic plants. The highly hydrophobic pharmaceuticals (logK_ow>4.0) did not show significant differences among the whole tests in sediment. Mass balance calculation displayed the removal of CBM (5.6%-13.6%), CLF (4.0%-17.8%) and caffeine (8.4%-17.2%) through the plant uptake was relatively higher. For the rest WWMPs, only small parts (<6.0%) of the initial concentrations were found in plant tissues. The higher removal efficiencies of most WWMPs under the planted conditions indicated that aquatic plants indeed played an important role in the removal of WWMPs although the direct uptakes might not be a dominant pathway to the overall removal of WWMPs. Besides, the floating aquatic plant removed most WWMPs from the water phase efficiently. In contrast, submerged and emergent aquatic plants could effectively remove them in sediment.