Contamination of sulfonamide antibiotics and sulfamethazine-resistant bacteria in the downstream and estuarine areas of Jiulong River in Southeast China

The Combination of β-Glucan and Astragalus Polysaccharide Effectively Resists Nocardia seriolae Infection in Largemouth Bass (Micropterus salmoides)

Effectively treating and preventing outbreaks is crucial for improving the economic benefits of aquaculture. Therefore, utilizing immunostimulants, either alone or in combination, is regarded as a promising strategy. In this study, β-glucan + APS (200 mg/kg + 200 mg/kg), β-glucan (200 mg/kg), APS (200 mg/kg), enrofloxacin (15 mg/kg), and sulfadiazine (15 mg/kg) were added to feed to assess the effects against Nocardia seriolae infection in largemouth bass (Micropterus salmoides) within 14 days. The survival rates did not differ between the enrofloxacin group and the β-glucan + APS group, but both were significantly higher than that of the control group. Additionally, the enrofloxacin group and the β-glucan + APS group exhibited the lowest bacterial loads and tissue damage. Importantly, the β-glucan + APS treatment significantly improved serum enzyme activities (total superoxide dismutase, lysozyme, total protein) and the expression of immune genes (IL-1β, TNF-α, IFN-γ, IgM) compared to the other treatment groups. The enrofloxacin group showed similar efficacy to the β-glucan + APS group in combating N. seriolae infection, but N. seriolae in the enrofloxacin group developed drug resistance. In summary, the combined use of β-glucan and APS is a promising strategy for treating bacterial diseases, thereby contributing to the promotion of sustainable aquaculture development.

Sub-lethal concentration of sulfamethoxazole affects the growth performance of milkfish (Chanos chanos), the microbial composition of antibiotic-resistant bacteria and the prevalence of sulfonamide-resistance genes in mariculture

To investigate the impacts of sub-lethal concentrations of antibiotic agents in mariculture, culturable approach and DNA based detection were employed to isolate and analyse resistant bacteria and resistant genes in this study. Milkfish (Chanos chanos), the target rearing animal was exposed to sulfamethoxazole (SMX; 2 mg/L) for 8 weeks and resulted in reduced survival rate and weight gain to 61.9 % and 28.4 %, respectively compared to control milkfish (p < 0.001). The composition of SMX-resistant bacteria isolated from the culture water and the gastrointestinal tracts of milkfish underwent changes in response to SMX treatment with a reduced diversity. The prevalence of SMX resistant genes sul in bacterial isolates was elevated from 2.8 % of control to 100 % of SMX-administrated water. Exposure to SMX at a sub-lethal dosage enhanced the prevalence of resistance genes sul1 and sul2 in resistant bacteria, thus implying high frequency of resistance dissemination in the marine environment and surrounding ecosystems.

Comparison of disinfection by-products formed by preoxidation of sulfamethazine by K2FeO4 and O3 and the influence on cytotoxicity and biological toxicity

This study researched the formation of disinfection by-products (DBPs) in sulfamethazine (SMZ) chlorination after preoxidation by K2FeO4 and O3 and the influence of preoxidation on cytotoxicity and biological toxicity. Then, the study emphatically analyzed the influencing factors such as NaClO dosage, pH value, reaction temperature, fulvic acid (FA), and bromide and iodide ions. The results showed that preoxidation by K2FeO4 effectively inhibited the formation of DBPs of haloketones (HKS) and trihalomethanes (THMs), with an average inhibition rate of over 60%. The formation of DBPs after preoxidation by O3 was higher than that by K2FeO4; preoxidation by K2FeO4 reduced the influence of NaClO dosage, temperature, and pH value on the production of DBPs after SMZ chlorination. The cytotoxicity and biological toxicity of SMZ chlorination after preoxidation were evaluated and compared by calculating the LC50 value of DBPs and the luminescent bacteria method. The results of both calculation methods showed that the toxicity of DBPs after preoxidation by K2FeO4 was lower than that by O3 preoxidation. K2FeO4 and O3 preoxidation improved the SMZ removal efficiency by 8.41 and 10.49%, respectively, and inhibited the formation of most DBPs, but the preoxidation promoted the formation of highly toxic DBPs (HANs). The toxicity of DBPs formed in SMZ chlorination after preoxidation by K2FeO4 and O3 was slightly higher than that of chlorination disinfection alone, but it was still within the safe range. This study provides more new details about the formation and toxicity changes of DBPs in the process of SMZ chlorination after preoxidation.

A review on the ecotoxicological effect of sulphonamides on aquatic organisms

Antibiotics are extensively used to treat human and animal diseases and are especially used in animal production to promote the growth performance of livestock and aquatic animals. Sulphonamides, as important drugs for aquatic animals, are often used in aquaculture to prevent and treat diseases. However, various antibiotics found in the aquatic environment exhibit varying degrees of toxicity to aquatic organisms. Antibiotics in wastewater produced in industrial and agricultural processes are not thoroughly removed by sewage treatment and are released into water, which results in varying degrees of pollution of the surrounding water environment, forcing people to pay attention towards the ecosystem. Several studies have investigated the impact of antibiotics on aquatic organisms in water environment; however, only a few studies have investigated the underlying mechanism. Antibiotics persisting in an aquatic environment for a long time can cause genotoxicity and histopathological changes in various aquatic organisms. Therefore, this paper reviews the sources of antibiotics in aquatic environment, the pollution status of sulfonamides in aquatic environment at home and abroad, and focuses on the research status of ecotoxicological effects of sulfonamides on aquatic organisms. Because there are not only antibiotic pollution, but also many other pollutants, such as heavy metals, micro plastics and other chemicals, it will be a challenge to determine the combined effects of antibiotics or other pollutants on aquatic organisms in future environmental toxicity studies.

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Sulphonamides are ubiquitously detected in the water environment.

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Sulfamethoxazole is one of the least efficient antibiotics removed in wastewater treatment plants.

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Interaction of sulphonamides with other antibiotics needs more attention.

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Multigeneration studies related to the water environment are needed.

Perspectives on the antibiotic contamination, resistance, metabolomics, and systemic remediation

Antibiotics have been regarded as the emerging contaminants because of their massive use in humans and veterinary medicines and their persistence in the environment. The global concern of antibiotic contamination to different environmental matrices and the emergence of antibiotic resistance has posed a severe impact on the environment. Different mass-spectrometry-based techniques confirm their presence in the environment. Antibiotics are released into the environment through the wastewater steams and runoff from land application of manure. The microorganisms get exposed to the antibiotics resulting in the development of antimicrobial resistance. Consistent release of the antibiotics, even in trace amount into the soil and water ecosystem, is the major concern because the antibiotics can lead to multi-resistance in bacteria which can cause hazardous effects on agriculture, aquaculture, human, and livestock. A better understanding of the correlation between the antibiotic use and occurrence of antibiotic resistance can help in the development of policies to promote the judicious use of antibiotics. The present review puts a light on the remediation, transportation, uptake, and antibiotic resistance in the environment along with a novel approach of creating a database for systemic remediation, and metabolomics for the cleaner and safer environment.

Biodegradation of sulfonamides in both oxic and anoxic zones of vertical flow constructed wetland and the potential degraders

The pollution of wastewater with antibiotics and antibiotics resistance genes has attracted public concerns about ecosystem and global health. Swine wastewater can contain high concentrations of antibiotics, especially sulfonamides, even after full-scale wastewater treatment. In this study, mesocosm-scale vertical flow constructed wetlands (VF-CWs) were applied to abate nutrients and antibiotics in swine wastewater containing sulfonamides. VF-CWs performed well in the removal of both nutrients and antibiotics. Sulfonamides did not influence total organic carbon (TOC) and total phosphorus (TP) removal, and even slightly enhanced NH₄⁺-N removal. High removal efficiencies (26.42-84.05%) were achieved for sulfadiazine (SDZ), sulfamethoxazole (SMX) and sulfamethazine (SMZ). Together with lab-scale sorption and biodegradation experiments, microbial degradation was found to be the most important removal mechanism for sulfonamides in VF-CWs. Sulfonamides addition increased bacterial alpha-diversity and changed microbial community structure. Moreover, antibiotics promoted antibiotic-resistant or -degrading bacteria. Bacillus, Geobacter and other seven genera were correlated with sulfonamides reduction under either aerobic or anaerobic condition. In summary, VF-CW is a suitable alternative for swine wastewater treatment, and biodegradation plays the key role in sulfonamides abatement. Main findings of the work. This was the first work to combine bacterial community analysis with microcosm experiments to uncover the major removal mechanism of sulfonamides in constructed wetlands.

Contamination profile of antibiotic resistance genes in ground water in comparison with surface water

Dissemination of antibiotic resistance genes (ARGs) in the water environment has become an increasing concern. There have been many reports on ARGs in surface water, but little is known about ARGs in groundwater. In this study, we investigated the profiles and abundance of ARGs in groundwater in comparison with those in surface water of Maozhou River using high-throughput quantitative PCR (HT-qPCR). Totally 127 ARGs and 10 MGEs were detected by HT-qPCR, and among them the sulfonamides, multidrug and aminoglycosides resistance genes were the dominant ARG types. According to the results of HT-qPCR, 18 frequently detected ARGs conferring resistance to 6 classes of antibiotics and 3 MGEs were further quantified by qPCR in the wet season and dry season. The absolute abundance ranged from 1.23 × 10⁵ to 8.89 × 10⁶ copies/mL in wet season and from 8.50 × 10² to 2.65 × 10⁶ copies/mL in the dry season, with sul1 and sul2 being the most abundant ARGs. The absolute abundance of ARGs and MGEs has no significant difference between the wet season and dry season while the diversity of ARGs in the dry season was higher than that in the wet season (p < 0.05). Totally 141 and 150 ARGs were detected in the water and sediments of Maozhou River, respectively. A total of 116 ARGs were shared among the groundwater, river water, and sediment, which accounted for 67.1% of all detected genes. Redundancy analysis further demonstrated that the environmental factors contributed 70.7% of the total ARG variations. The findings of large shared ARGs, abundant Total Coliforms and large wastewater burden in the groundwater provide a clear evidence that anthropogenic activities had a significant impact on groundwater.

Quorum Quenching Properties and Probiotic Potentials of Intestinal Associated Bacteria in Asian Sea Bass Lates calcarifer

Quorum quenching (QQ), the enzymatic degradation of N-acyl homoserine lactones (AHLs), has been suggested as a promising strategy to control bacterial diseases. In this study, 10 AHL-degrading bacteria isolated from the intestine of barramundi were identified by 16S rDNA sequencing. They were able to degrade both short and long-chain AHLs associated with several pathogenic Vibrio species (spp.) in fish, including N-[(RS)-3-Hydroxybutyryl]-l-homoserine lactone (3-oh-C₄-HSL), N-Hexanoyl-l-homoserine lactone (C₆-HSL), N-(β-Ketocaproyl)-l-homoserine lactone (3-oxo-C₆-HSL), N-(3-Oxodecanoyl)-l-homoserine lactone (3-oxo-C₁₀-HSL), N-(3-Oxotetradecanoyl)-l-homoserine lactone (3-oxo-C₁₄-HSL). Five QQ isolates (QQIs) belonging to the Bacillus and Shewanella genera, showed high capacity to degrade both synthetic AHLs as well as natural AHLs produced by Vibrio harveyi and Vibrio alginolyticus using the well-diffusion method and thin-layer chromatography (TLC). The genes responsible for QQ activity, including aiiA, ytnP, and aaC were also detected. Analysis of the amino acid sequences from the predicted lactonases revealed the presence of the conserved motif HxHxDH. The selected isolates were further characterized in terms of their probiotic potentials in vitro. Based on our scoring system, Bacillus thuringiensis QQ1 and Bacillus cereus QQ2 exhibited suitable probiotic characteristics, including the production of spore and exoenzymes, resistance to bile salts and pH, high potential to adhere on mucus, appropriate growth abilities, safety to barramundi, and sensitivity to antibiotics. These isolates, therefore, constitute new QQ probiotics that could be used to control vibriosis in Lates calcalifer.

Seasonal variation and spatial transport of polycyclic aromatic hydrocarbons in water of the subtropical Jiulong River watershed and estuary, Southeast China

Riverine runoff is one of the most important pathways of pollutants entering the oceans. To study the seasonal variations, spatial transports, sources and mass fluxes of polycyclic aromatic hydrocarbons (PAHs) from the subtropical Jiulong River watershed to estuary, water samples were collected in wet and dry seasons. PAH concentrations showed significant temporal-spatial variations (ANOVA, p < 0.05). In the watershed, PAH concentrations in wet season (48.6 ± 18.2 ng L^-1) were significantly lower than in dry season (90.3 ± 18.5 ng L^-1). In contrast, estuarine PAH concentrations in wet season (67.1 ± 24.6 ng L^-1) were significantly higher than in dry season (27.4 ± 10.6 ng L^-1) (p < 0.0001). The spatial variations of PAH concentrations in wet and dry seasons reflected positive and restricted transport processes occurred in the river. These findings might be subjected to seasonal changes in precipitation, water discharge, hydrodynamic conditions, and human activities. The compositional patterns of PAHs illustrated that fluorene and phenanthrene were the dominant compounds in the watershed, while phenanthrene was predominant in the estuary. Source analysis by molecular diagnostic ratios and PMF model indicated that fossil fuel and biomass combustion and petroleum both contributed to the presence of PAHs, and the high contributions of pyrogenic PAHs might be related to urban rainstorm runoff in winter and atmospheric inputs in winter. Although the estimated flux of PAHs from watershed to estuary was about 676 kg yr^-1 with a low level by comparing the data obtained in the worldwide, continue concern of PAHs in the Jiulong River is recommended due to the intense human activities.

Annual changes in the occurrence of antibiotic-resistant coliform bacteria and enterococci in municipal wastewater

Wastewater contains subinhibitory concentrations of different micropollutants such as antibiotics that create selective pressure on bacteria. This phenomenon is also caused by insufficient wastewater treatment technology leading to the development and spread of antibiotic-resistant bacteria and resistance genes into the environment. Therefore, this work focused on monitoring of antibiotic-resistant coliform bacteria and enterococci in influent and effluent wastewaters taken from the second biggest wastewater treatment plant (Petržalka) in the capital of Slovakia during 1 year. Antibiotic-resistant strains were isolated, identified, and characterized in terms of susceptibility and biofilm production. All of 27 antibiotic-resistant isolates were identified mainly as Morganella morganii, Citrobacter spp., and E. coli. Multidrug-resistance was detected in 58% of isolated strains. All tested isolates could form biofilm; two strains were very strong producers, and 74% formed biofilm by strong intensity. The flow rate of the influent wastewater had a more significant impact on the number of studied bacteria than the temperature. Graphical abstract.

Transformation of sulfamethazine during the chlorination disinfection process: Transformation, kinetics, and toxicology assessment

Various disinfection byproducts (DBPs) form during the process of chlorination disinfection, posing potential threats to drinking water safety and human health. Sulfamethazine (SMT), the most commonly used and frequently detected veterinary antibiotic, was investigated in detail with regard to its transformation and kinetics in reactions with free available chlorine (FAC). Using liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry, several DBPs were identified based on different confidence levels, and a variety of reaction types, including desulfonation, S-N cleavage, hydroxylation, and chlorine substitution, were proposed. The kinetic experiments indicated that the reaction rate was FAC- and pH-dependent, and SMT exhibits low reactivity toward FAC in alkaline conditions. The DBPs exhibited a much higher acute toxicity than SMT, as estimated by quantitative structure activity relationship models. More importantly, we observed that the FAC-treated SMT reaction solution might increase the genotoxic potential due to the generation of DBPs. This investigation provides substantial new details related to the transformation of SMT in the chlorination disinfection process.

Contribution of biotic and abiotic factors in the natural attenuation of sulfamethoxazole: A path analysis approach

Sulfamethoxazole (SMX) is a sulfonamide antibiotic, widely used as curative and preventive drug for human, animal, and aquaculture bacterial infections. Its residues have been ubiquitously detected in the surface waters and sediments. In the present study, SMX dissipation and kinetics was studied in the natural water samples from Jiulong River under simulated complex natural conditions as well as conditions to mimic various biotic and abiotic environmental conditions in isolation. Structural equation modeling (SEM) by employing partial least square technique in path coefficient analysis was used to investigate the direct and indirect contributions of different environmental factors in the natural attenuation of SMX. The model explained 81% of the variability in natural attenuation as a dependent variable under the influence of sole effects of direct photo-degradation, indirect photo-degradation, hydrolysis, microbial degradation and bacterial degradation. The results of SEM suggested that the direct and indirect photo-degradation were the major pathways in the SMX natural attenuation. However, other biotic and abiotic factors also play a mediatory role during the natural attenuation and other processes. Furthermore, the potential transformation products of SMX were identified and their toxicity was evaluated.

Antibiotic resistance genes in China: occurrence, risk, and correlation among different parameters

Antibiotic resistance has become a widely concerned issue due to the huge risk on the ecological environment and human health. China has the highest production and consumption of antibiotics than other countries. Thus, antibiotic resistance genes (ARGs) have been detected in various environmental settings (e.g., surface water, wastewater, sediment) in China. The occurrence of ARGs in these matrixes was summarized and discussed in this review. Sulfonamide resistance genes and tetracycline resistance genes were the most frequently detected ARGs in China. According to the abundance of these two classes of ARGs in the natural environment, sulfonamide resistance genes seem to be more stable than tetracycline resistance genes. Furthermore, the relationships between ARGs and antibiotics, antibiotic resistance bacteria (ARB), heavy metals, and environmental parameters (e.g., pH, organics) were also investigated. Specifically, relative abundance of total ARGs was found to correlate well with concentration of total antibiotics in aqueous phase but not in the solid phase (soil, sediment, sludge, and manure). As for relationship between ARGs and ARB, metals, and environmental parameters in different media, due to complex and variable environment, some exhibit positive correlation, some negative, while others no correlation at all. Three potential risks are discussed in the text: transmission to human, synergistic effect of different ARGs, and variability of ARGs. However, due to the complexity of the environment, more work is needed to establish a quantitative approach of ARG risk assessment, which can provide a theoretical support for the management of antibiotics and the protection of human health.

Simultaneous determination of sulfonamides and fluoroquinolones from environmental water based on magnetic double-template molecularly imprinting technique

In this work, a fast and selective method based on magnetic extraction is presented for the simultaneous extraction of sulfonamides (SAs) and fluoroquinolones (FQs), followed by liquid chromatography-tandem mass spectrometry detection. In this method, magnetic surface double-template molecularly imprinted polymers (MSdt-MIPs) with superparamagnetic property and high selectivity toward both SAs and FQs were synthesized and directly applied to the simultaneous extraction of SAs and FQs from environmental water as magnetic adsorbents. The extraction and enrichment procedures could be accomplished in one single step by stirring the mixture of MSdt-MIPs and water sample, and the MSdt-MIPs with adsorbed analytes were easily separated from the water sample by a magnet afterwards. The adsorption mechanism of MSdt-MIPs was investigated by employing the adsorption thermodynamic and kinetic studies, and the selectivity of the MSdt-MIPs toward target analytes was evaluated through the selectivity test. For validation of the proposed method, the matrix effect was evaluated and compared to that of the traditional SPE method. Excellent linearity (R > 0.9990) for both SAs and FQs were obtained in the concentration range of 20-2000 ng L^-1, and the limits of detection are in the range of 3.0-4.7 ng L^-1 for SAs while 4.1-6.1 ng L^-1 for FQs. Finally, the proposed method was successfully applied to the simultaneous determination of SAs and FQs in several environmental water samples.

A duodecennial national synthesis of antibiotics in China's major rivers and seas (2005-2016)

The occurrence of 94 antibiotics in water and sediments from seven major rivers and four seas in China during 2005-2016 was reviewed. Twelve antibiotics were most frequently detected in both water and sediment samples, including 3 sulfonamides (SAs), 2 tetracyclines (TCs), 4 fluoroquinolones (FQs), and 3 macrolides (MLs). Their median concentrations were below 100ng/L and 100ng/g in river water and sediments, respectively. The highest median concentrations were found in water (1.30-176ng/L) and sediments (0.15-110ng/g) in the Hai River, due to its larger population density, higher consumption of antibiotics, and lower water flow. The concentrations of TCs and FQs were higher in the Pearl River sediments, due to their extensive use in aquaculture. The Yangtze River showed lower median concentrations of antibiotics in both water (1.33-17.3ng/L) and sediments (0.31-14.8ng/g), resulting from its larger catchment size, and higher precipitation and water flow. The Yellow River exhibited lower median concentrations of antibiotics in sediments (0.04-9.04ng/g), probably due to low organic matter content in sediments and high suspended particle content in water. Organic carbon normalized distribution coefficients (K_oc) of antibiotics were positively correlated with the octanol/water partition coefficients (K_ow) of antibiotics, and the correlation for MLs with a macrocyclic lactone ring was different from that of SAs, FQs, and TCs, likely due to their much larger molecular size. Among China's major rivers, the Hai River had the highest ecotoxicological risk from antibiotics to algae, invertebrate, fish, and plant.

Catalytic degradation of sulfaquinoxalinum by polyester/poly-4-vinylpyridine nanofibers-supported iron phthalocyanine

Iron (II) phthalocyanine (FePc) supported on electrospun polyester/poly-4-vinylpyridine nanofibers (PET/P4VP NFs) was prepared by stirring in tetrahydrofuran. The resulting product was confirmed and characterized by ultraviolet-visible diffuse reflectance spectroscopy, attenuated total reflection Fourier transform infrared spectra, X-ray photoelectron spectroscopy, gas chromatography/mass spectrometry, and ultra-performance liquid chromatography. More than 95% of sulfaquinoxalinum (SQX) could be removed by the activation of hydrogen peroxide in the presence of FePc-P4VP/PET with a PET and P4VP mass ratio of 1:1. This system exhibited a high catalytic activity across a wide pH and temperature range. The degradation rates of SQX achieved 100, 95, and 78% at a pH of 3, 7, and 9, respectively, and the degradation rates of SQX are more than 80% at the temperature ranging from 35 to 65 °C. DMSO₂ could be detected by gas chromatography/mass spectrometry after the addition of DMSO, suggesting the formation of the high-valent iron intermediates in this catalytic system. In addition, the electron paramagnetic resonance experiments proved that free radicals did not dominate the reaction in our system. Therefore, the high-valent iron intermediates were proposed to the main active species in the FePc-P4VP/PET/hydrogen peroxide system. In summary, the heterogeneous catalytic processes with non-radical catalytic mechanism might have better catalytic performance for the removal of organic pollutants, which can potentially be used in wastewater treatment.

Monitoring tylosin and sulfamethazine in a tile-drained agricultural watershed using polar organic chemical integrative sampler (POCIS)

This study evaluated the influence of temporal variation on the occurrence, fate, and transport of tylosin (TYL) and sulfamethazine (SMZ); antibiotics commonly used in swine production. Atrazine (ATZ) was used as a reference analyte to indicate the agricultural origin of the antibiotics. We also assessed the impact of season and hydrology on antibiotic concentrations. A reconnaissance study of the South Fork watershed of the Iowa River (SFIR), was conducted from 2013 to 2015. Tile drain effluent and surface water were monitored using polar organic integrative sampler (POCIS) technology. Approximately 169 animal feeding operations (AFOs) exist in SFIR, with 153 of them being swine facilities. All analytes were detected, and detection frequencies ranged from 69 to 100% showing the persistence in the watershed. Antibiotics were detected at a higher frequency using POCIS compared to grab samples. We observed statistically significant seasonal trends for SMZ and ATZ concentrations during growing and harvest seasons. Time weighted average (TWA) concentrations quantified from the POCIS were 1.87ngL^-1 (SMZ), 0.30ngL^-1 (TYL), and 754.2ngL^-1 (ATZ) in the watershed. SMZ and TYL concentrations were lower than the minimum inhibitory concentrations (MIC) for E. coli. All analytes were detected in tile drain effluent, confirming tile drainage as a pathway for antibiotic transport. Our results identify the episodic occurrence of antibiotics, and highlights the importance identifying seasonal fate and occurrence of these analytes.

Review of antibiotic resistance in China and its environment

Antibiotic resistance is a global health crisis linked to increased, and often unrestricted, antibiotic use in humans and animals. As one of the world's largest producers and consumers of antibiotics, China is witness to some of the most acute symptoms of this crisis. Antibiotics and antibiotic resistance genes (ARGs) are widely distributed in surface water, sewage treatment plant effluent, soils and animal wastes. The emergence and increased prevalence of ARGs in the clinic/hospitals, especially carbapenem-resistant gram negative bacteria, has raised the concern of public health officials. It is important to understand the current state of antibiotic use in China and its relationship to ARG prevalence and diversity in the environment. Here we review these relationships and their relevance to antimicrobial resistance (AMR) trends witnessed in the clinical setting. This review highlights the issues of enrichment and dissemination of ARGs in the environment, and also future needs in mitigating the spread of antibiotic resistance in the environment, particularly under the 'planetary health' perspective, i.e., the systems that sustain or threaten human health.

Selective determination of sulfonamides from environmental water based on magnetic surface molecularly imprinting technology

In the study, a simple and selective method based on magnetic separation technology is presented for the extraction of sulfonamides (SAs) from environmental water, followed by liquid chromatography-tandem mass spectrometry. In this method, magnetic surface molecularly imprinted polymers (Fe₃O₄@SiO₂@MIPs) with super-paramagnetic property and high selectivity toward SAs were developed as magnetic adsorbents. The Fe₃O₄@SiO₂@MIPs were then applied to the selective extraction of SAs from environmental water. The extraction and enrichment were accomplished simultaneously in a single step by simply stirring the mixture of adsorbents and water samples. The Fe₃O₄@SiO₂@MIPs were characterized by scanning electron microscopy, Fourier-transform infrared spectrometry, and vibrating sample magnetometry. The adsorption thermodynamics and kinetics were employed to study the adsorption mechanism of the Fe₃O₄@SiO₂@MIPs. And the matrix effect of the method was evaluated. Calibration curves obtained by analyzing matrix-matched standards show excellent linear relationship (R = 0.9994-0.9999) in the concentration range of 10-1000 ng L^-1, and the limits of detection are in the range of 1.4-2.8 ng L^-1. The relative standard deviations of intra- and inter-day obtained are in the range of 2.8 to 7.8 and 3.1 to 7.9%, respectively. The proposed method was successfully applied to determine SAs in six environmental water samples, and SAs were detectable in four of them with the concentration from 10.5 to 120.2 ng L^-1.

Detection, Occurrence and Fate of Emerging Contaminants in Agricultural Environments

A total of 59 papers published in 2015 were reviewed ranging from detailed descriptions of analytical methods, to fate and occurrence studies, to ecological effects and sampling techniques for a wide variety of emerging contaminants likely to occur in agricultural environments. New methods and studies on veterinary pharmaceuticals, steroids, antibiotic resistance genes in agricultural environments continue to expand our knowledge base on the occurrence and potential impacts of these compounds. This review is divided into the following sections: Introduction, Analytical Methods, Steroid Hormones, Pharmaceutical Contaminants, Transformation Products, and "Antibiotic Resistance, Drugs, Bugs and Genes".

Density functional theory study of direct and indirect photodegradation mechanisms of sulfameter

Sulfonamide antibiotics (SAs) have been observed to undergo direct and indirect photodegradation in natural water environments. In this study, the density functional theory (DFT) method was employed for the study of direct and indirect photodegradation mechanisms of sulfameter (SME) with excited triplet states of dissolved organic matter ((3)DOM(*)) and metal ions. SME was adopted as a representative of SAs, and SO2 extrusion product was obtained with different energy paths in the triplet-sensitized photodegradation of the neutral (SME(0)) and the anionic (SME(-)) form of SME. The selected divalent metal ions (Ca(2+), Mg(2+), and Zn(2+)) promoted the triplet-sensitized photodegradation of SME(0) but showed an inhibitory effect in triplet-sensitized photodegradation of SME(-). The triplet-sensitized indirect photodegradation mechanism of SME was investigated with the three DOM analogues, i.e., 2-acetonaphthone (2-AN), fluorenone (FN), and thioxanthone (TN). Results indicated that the selected DOM analogues are highly responsible for the photodegradation via attacking on amine moiety of SME. According to the natural bond orbital (NBO) analysis, the triplet-sensitized photodegradation mechanism of SME(0) with 2-AN, FN, and TN was H-transfer, and the SME(-) was proton plus electron transfer with these DOM analogues.