Antibiotics pollution in Jiulong River estuary: source, distribution and bacterial resistance

Typical antibiotic resistance genes and their association with driving factors in the coastal areas of Yangtze River Estuary

The massive use of antibiotics has led to the escalation of microbial resistance in aquatic environment, resulting in an increasing concern regarding antibiotic resistance genes (ARGs), posing a serious threat to ecological safety and human health. In this study, surface water samples were collected at eight sampling sites along the Yangtze River Estuary. The seasonal and spatial distribution patterns of 10 antibiotics and target genes in two major classes (sulfonamides and tetracyclines) were analyzed. The findings indicated a high prevalence of sulfonamide and tetracycline resistance genes along the Yangtze River Estuary. Kruskal-Wallis analysis revealed significant seasonal variations in the abundance of all target genes. The accumulation of antibiotic resistance genes in the coastal area of the Yangtze River Estuary can be attributed to the influence of urban instream runoff and the discharge of effluents from wastewater treatment plants. ANISOM analysis indicated significant seasonal differences in the microbial community structure. VPA showed that environmental factors contribute the most to ARG variation. PLS-PM demonstrate that environmental factors and microbial communities pose direct effect to ARG variation. Analysis of driving factors influencing ARGs in this study may shed new insights into the mechanism of the maintenance and propagation of ARGs.

Fabrication of magnetic MnFe2O4@HL composites with an in situ Fenton-like reaction for enhancing tetracycline degradation

Novel magnetic MnFe2O4@honey locust-derived carbon (MnFe2O4@HL) composites were synthesized via an in-situ hydrothermal precipitation method, and were characterized as an excellent Fenton-like catalyst for tetracycline (TC) degradation. Results showed that the vast majority of TC was mineralized in hydrogen peroxide (H2O2)/MnFe2O4@HL system after 120 min of reaction time with 92.3% of removal efficiency and the removal of 71.3% of total organic carbon (TOC). Systematic characterization approaches including scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM) were introduced to reveal the microstructure and properties of magnetic MnFe2O4@HL composites. Hydroxyl radicals (•OH) were identified as the major reactive oxygen species (ROS) via the quenching experiments and electron spin resonance (ESR) analysis, while superoxide radicals (·O2-) played a negligible role. The dual cycles of both Fe3+/Fe2+ and Mn3+/Mn2+ were significant enhanced through the bimetallic redox effect and the electron transfer effect of the carbon-based functional group, accelerating the generation of •OH. The removal of TC was still up to 79.3% after five reuses of magnetic composites, demonstrating the MnFe2O4@HL with excellent stability and reuse performance. The influence of various experimental control conditions involving initial pH, catalyst and H2O2 dosage, temperature, as well as common anions (Cl-, NO3-, and HCO3-) on the degradation of TC were finally evaluated. This study provides an efficient in-situ generation method of emerging magnetic materials, and systematically reveals its mechanism of homogeneous Fenton-like catalysis, which shows promising applications for the degradation of environmental contaminants.

The photo- and microbial degradation kinetics and pathways of sulfadoxine in seawater elucidated by liquid chromatography coupled with time-of-flight mass spectrometry

Sulfadoxine (SDX) is a broad-spectrum veterinary antibiotic, which was used alone for the treatment of various infections in the past, and detected ubiquitously in the aqueous environment. However, understanding SDX's photo- and microbial degradation within the environment, especially in marine matrixes, remains limited. This research hones in on SDX's degradation dynamics in seawater. Photodegradation emerges as the dominant process, surpassing microbial degradation in speed and efficiency. Notably, 90% of SDX is photo-degraded within 12 h, while only 52% is removed via microbial degradation over two weeks. Time-of-flight mass spectrometry provides high-resolution molecular mass information on degradation products. The molecular structures of hydrolysis, photo-, and microbial degradation products are deduced from accurate precursor and fragment ion masses, alongside an integrated data processing workflow. Six hydrolysis products arise from the treatment, and photodegradation and microbial degradation yield nine and eighteen products, respectively. Molecular insights from these products inform plausible degradation pathways involving hydrolysis, photodegradation, and microbial degradation. Processes like bond cleavage, methylation, hydroxylation, oxidation, reduction, and methoxylation are identified and associated with degradation. This study presents a comprehensive workflow for acquiring and processing degradation product data linked to emerging organic pollutants. Moreover, it contributes to our comprehension of the environmental fate of veterinary drugs in marine ecosystems.

Antibiotics resistance removal from piggery wastewater by an integrated anaerobic-aerobic biofilm reactor: Efficiency and mechanism

Antibiotic resistance residual in piggery wastewater poses serious threat to environment and human health. Biological treatment process is commonly installed to remove nutrient from piggery wastewater and also effective in removing antibiotics to varying degrees. But the specific pathways and mechanisms involved in the removal of antibiotic resistance are not yet well-understood. An integrated anaerobic-aerobic biofilm reactor (IAOBR) has been demonstrated efficient in removing conventional nutrients. It is here shown that the IAOBR effectively removed 79.0% of Sulfonamides, 55.7% of Tetracyclines and 53.6% of Quinones. Antibiotic resistance bacteria (ARB) were simultaneously inactivated by ~0.5 logs. Antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) were decreased by 0.51 logs and 0.42 logs, respectively. The antibiotics were mainly removed through aerobic compartments of the IAOBR. The mass loss of antibiotics in the reactor was achieved by biodegradation and adsorption, accounting for 52.1% and 47.9%, respectively. An obvious accumulation of ARGs was observed in the activated sludge. The potential host of ARGs was analyzed via microbial community and network. Partial least squares-structural equation model and correlation analysis revealed that the enrichment of ARGs was positively affected by MGEs, followed by bacterial community and ARBs, but the effect of antibiotics on ARGs was negative. Outcomes of this study provide valuable insights into the mechanisms of antibiotic resistance removal in biological treatment processes.

Permeability decides the effect of antibiotics on sedimentary nitrogen removal in Jiulong River Estuary

Sedimentary denitrification takes place beneath the oxic layer at the sediment-water interface, where nitrate and antibiotics need to diffuse through the overlying water. However, the antibiotics' effect on sedimentary N removal and associated N2O production has not been adequately investigated under in situ conditions. Here, isotope pairing techniques, including slurry incubations (potential) and intact core incubations (in situ), combined with metagenomic analysis were applied to investigate the impacts of two protein-inhibiting antibiotics (oxytetracycline and thiamphenicol) on sediment nitrogen removal in a subtropical estuary. Slurry incubations showed that the two antibiotics significantly inhibited denitrification (67-98%) and anammox (49-99%), while intact core incubations presented no antibiotic effect at upstream but significant inhibition (23%-52%) at downstream. Meanwhile, N2O yields were stimulated up to 20 folds in slurry incubations yet showing insignificant response in intact cores. Such contrasting results between up- and down-stream and between slurry and intact core incubations strongly indicated that permeability, which determines diffusion of antibiotics to microbes, is the key to exert the effect of antibiotics on in situ sedimentary nitrogen removal processes regardless the existence of antibiotics resistance genes. This diffusive obstruction may mitigate the toxic effect of antibiotics on nitrogen removal related microbes in natural environments.

Carbon nanotube-loaded copper-nickel ferrite activated persulfate system for adsorption and degradation of oxytetracycline hydrochloride

In this study, a new composite (MWCNTs-CuNiFe₂O₄) prepared by loading magnetic CuNiFe₂O₄ particles onto carboxylated carbon nanotubes (MWCNTs) through co-precipitation was applied to remove oxytetracycline hydrochloride (OTC-HCl) in solution. The magnetic properties of this composite could address of the issue of difficulty associated with the separation of MWCNTs from mixtures when applied as an adsorbent. In addition to the good adsorption properties recorded for MWCNTs-CuNiFe₂O₄ towards OTC-HCl, this developed composite could be used to activate potassium persulfate (KPS) for an efficient degradation of OTC-HCl. The MWCNTs-CuNiFe₂O₄ was systematically characterized using Vibrating Sample Magnetometer (VSM), Electron Paramagnetic Resonance (EPR) and X-ray Photoelectron Spectroscopy (XPS). The influence of dose of MWCNTs-CuNiFe₂O₄, the initial pH, the amount of KPS and the reaction temperature on the adsorption and degradation of OTC-HCl by MWCNTs-CuNiFe₂O₄ were discussed. The adsorption and degradation experiments showed that MWCNTs-CuNiFe₂O₄ exhibited an adsorption capacity of 270 mg·g^-1 for OTC-HCl with the removal efficiency 88.6% at 303 K (at an initial pH 3.52, 5 mg KPS, 10 mg composite, 10 mL reaction concentration 300 mg·L^-1 of OTC-HCl). The Langmuir and Koble-Corrigan models were used to describe the equilibrium process while the Elovich equation and Double constant model were suitable to describe the kinetic process. The adsorption process was based on single-molecule layer reaction and non-homogeneous diffusion process. The mechanisms of adsorption were complexation and hydrogen bond whereas active species such as SO₄^‧-, ^‧OH and ¹O₂ were confirmed to have played a major role in the degradation of OTC-HCl. The composite was also found to be very stable with good reusability property. These results confirm the good potential associated with the use of MWCNTs-CuNiFe₂O₄/KPS system for the removal of some typical pollutants from wastewater.

Ceftriaxone sodium degradation by carbon quantum dots (CQDs)-decorated C-doped α-Bi2O3 nanorods

A novel carbon quantum dots decorated C-doped α-Bi₂O₃ photocatalyst (CBO/CQDs) was synthesized by solvothermal method. The synergistic effect of adsorption and photocatalysis highly improved contaminants removal efficiencies. The ceftriaxone sodium degradation rate constant (k) of CBO/CQDs was 11.4 and 3.2 times that of pure α-Bi₂O₃ and C-doped α-Bi₂O₃, respectively. The interstitial carbon doping generated localized states above the valence band, which enhanced the utilization of visible light and facilitated the separation of photogenerated electrons and holes; the loading of CQDs improved the charge carrier separation and extended the visible light response; the reduced particle size of CBO/CQDs accelerated the migration of photogenerated carriers. The •O₂ ^- and h⁺ were identified as the dominant reactive species in ceftriaxone sodium degradation, and the key role of •O₂ ^- was further investigated by NBT transformation experiments. The Fukui index was applied to ascertain the molecular bonds of ceftriaxone sodium susceptible to radical attack, and intermediates analysis was conducted to explore the possible degradation pathways. The toxicity evaluation revealed that some degradation intermediates possessed high toxicity, thus the contaminants require sufficient mineralization to ensure safe discharge. The present study makes new insights into synchronous carbon dopping and CQDs decoration on modification of α-Bi₂O₃, which provides references for future studies.

Shewanella spp. from wastewater treatment plant-affected environment: isolation and characterization

Bacteria from the genus Shewanella are inhabitants of marine and freshwater ecosystems, recognized fish spoilage bacteria, but less known as fish disease agents. Shewanella spp. isolated from fish living in waters close to effluents of a wastewater treatment plant (WWTP) were not previously characterized. We have tested Shewanella isolates from WWTP-affected waters and related fish. Genotypic characterization identified most strains as S. baltica and S. oneidensis. In order to investigate the sensibility and accuracy of their MALDI-TOF MS identification, they were grown on two culture media enriched by various NaCl concentrations, incubated at different temperatures and duration. We analyzed their antimicrobial susceptibility on a panel of antimicrobial drugs and capacity for biofilm production. With a view to demonstrate their capacity to produce fatty acids, we assessed the impact of different culture media on their lipid profile. We performed zebrafish embryotoxicity tests to simulate the environmental infection of the earliest life stages in S. baltica-contaminated waters. The best MALDI-TOF MS identification scores were for strains cultivated on TSA for 24 h at 22 °C and with supplementation of 1.5% NaCl. Less than 17% of isolates demonstrated antimicrobial resistance. Most isolates were weak biofilm producers. Strain-to-strain variation of MIC and MBC was low. The major fatty acids were C15:0, C16:0, C16:1, C17:1, and iC15:0. Exposure of Danio rerio to different S. baltica concentrations induced severe effects on zebrafish development: decreased heartbeat rate, locomotor activity, and melanin pigmentation. S. baltica passed through chorionic pores of zebrafish.

Occurrence and Distribution of Antibiotics in the Water, Sediment, and Biota of Freshwater and Marine Environments: A Review

Antibiotics, as pollutants of emerging concern, can enter marine environments, rivers, and lakes and endanger ecology and human health. The purpose of this study was to review the studies conducted on the presence of antibiotics in water, sediments, and organisms in aquatic environments (i.e., seas, rivers, and lakes). Most of the reviewed studies were conducted in 2018 (15%) and 2014 (11%). Antibiotics were reported in aqueous media at a concentration of <1 ng/L−100 μg/L. The results showed that the highest number of works were conducted in the Asian continent (seas: 74%, rivers: 78%, lakes: 87%, living organisms: 100%). The highest concentration of antibiotics in water and sea sediments, with a frequency of 49%, was related to fluoroquinolones. According to the results, the highest amounts of antibiotics in water and sediment were reported as 460 ng/L and 406 ng/g, respectively. In rivers, sulfonamides had the highest abundance (30%). Fluoroquinolones (with an abundance of 34%) had the highest concentration in lakes. Moreover, the highest concentration of fluoroquinolones in living organisms was reported at 68,000 ng/g, with a frequency of 39%. According to the obtained results, it can be concluded that sulfonamides and fluoroquinolones are among the most dangerous antibiotics due to their high concentrations in the environment. This review provides timely information regarding the presence of antibiotics in different aquatic environments, which can be helpful for estimating ecological risks, contamination levels, and their management.

Spatial-temporal distribution of total organic carbon and its transportation in the Jiulong River Estuary

Spatial and temporal distributions of total organic carbon (TOC) in the Jiulong River Estuary (JRE) were determined using data collected during three cruises in summer 2010, autumn 2010, and spring 2011. The TOC concentration influencing factors were identified, and the export fluxes were calculated. TOC concentration ranges were 0.73-4.17 mg/L in summer, 0.90-5.32 mg/L in autumn, and 1.78-8.03 mg/L in spring, respectively. TOC concentrations of the surface water and nearshore area were higher than those of the bottom water and offshore area, respectively, and the maximum TOC content occurred in the JRE upper reaches. The TOC concentration decreased with increasing salinity and exhibited a significant positive correlation with petroleum and dissolved inorganic nitrogen (DIN), indicating the influence of terrestrial input. A weak relationship between TOC and chlorophyll-a indicated that phytoplankton was not the dominant source of TOC. TOC fluxes discharged into the JRE were 50.39 × 10³ t/a in 2010 and 46.08 × 10³ t/a in 2011, and those transported into the sea were 38.46 × 10³ t/a in 2010 and 33.66 × 10³ t/a in 2011, respectively, accounting for approximately 75% of the total estuary fluxes. This study elucidates the biogeochemical processes of estuarine organic carbon and provides a quantitative basis for the land-sea integration of carbon dioxide emission reduction and sink increase projects.

Electrocatalytic oxidation of low concentration cefotaxime sodium wastewater using Ti/SnO2-RuO2 electrode: Feasibility analysis and degradation mechanism

In this research, Ti/SnO₂-RuO₂ stable anode was successfully prepared by thermal decomposition method, and low concentration cefotaxime sodium (CFX) was degraded by green and sustainable electrocatalytic oxidation technology. The electrocatalytic activity and stability of the Ti/SnO₂-RuO₂ coating electrode were studied according to the polarization curve of oxygen and chlorine evolution. The effects of current density, initial concentration, pH, electrolyte concentration, and other technological parameters on the degradation efficiency were discussed. Orthogonal experiment results indicated that when the current density was 25 mA cm^-2, concentration of electrolyte was 5 mM and the pH value was 7, the best CFX removal rate of 86.33% could be obtained. The degradation efficiency of electrocatalytic oxidation was discussed through electrochemical analysis. Fourier transform infrared spectroscopy was used to analyze the different inlet and outlet stages before and after the degradation of CFX, and the possible degradation process was discussed. Therefore, the electrocatalytic oxidation of Ti/SnO₂-RuO₂ electrode was a clean and efficient technology, which could be widely used in the treatment of CFX wastewater.

Abundance, fate, and effects of pharmaceuticals and personal care products in aquatic environments

Pharmaceuticals and personal care products (PPCPs) are found in wastewater, and thus, the environment. In this study, current knowledge about the occurrence and fate of PPCPs in aquatic systems-including wastewater treatment plants (WWTPs) and natural waters around the world-is critically reviewed to inform the state of the science and highlight existing knowledge gaps. Excretion by humans is the primary route of PPCPs entry into municipal wastewater systems, but significant contributions also occur through emissions from hospitals, PPCPs manufacturers, and agriculture. Abundance of PPCPs in raw wastewater is influenced by several factors, including the population density and demography served by WWTPs, presence of hospitals and drugs manufacturers in the sewershed, disease burden of the population served, local regulations, and climatic conditions. Based on the data obtained from WWTPs, analgesics, antibiotics, and stimulants (e.g., caffeine) are the most abundant PPCPs in raw wastewater. In conventional WWTPs, most removal of PPCPs occurs during secondary treatment, and overall removal exceeds 90% for treatable PPCPs. Regardless, the total PPCP mass discharged with effluent by an average WWTP into receiving waters (7.35-20,160 g/day) is still considerable, because potential adverse effects of some PPCPs (such as ibuprofen) on aquatic organisms occur within measured concentrations found in surface waters.

Antibiotics, antibiotic-resistant bacteria, and resistance genes in aquaculture: risks, current concern, and future thinking

Aquaculture is remarkably one of the most promising industries among the food-producing industries in the world. Aquaculture production as well as fish consumption per capita have been dramatically increasing over the past two decades. Shifting of culture method from semi-intensive to intensive technique and applying of antibiotics to control the disease outbreak are the major factors for the increasing trend of aquaculture production. Antibiotics are usually present at subtherapeutic levels in the aquaculture environment, which increases the selective pressure to the resistant bacteria and stimulates resistant gene transfer in the aquatic environment. It is now widely documented that antibiotic resistance genes and resistant bacteria are transported from the aquatic environment to the terrestrial environment and may pose adverse effects on human and animal health. However, data related to antibiotic usage and bacterial resistance in aquaculture is very limited or even absent in major aquaculture-producing countries. In particular, residual levels of antibiotics in fish and shellfish are not well documented. Recently, some of the countries have already decided the maximum residue levels (MRLs) of antibiotics in fish muscle or skin; however, many antibiotics are yet not to be decided. Therefore, an urgent universal effort needs to be taken to monitor antibiotic concentration and resistant bacteria particularly multiple antibiotic-resistant bacteria and to assess the associated risks in aquaculture. Finally, we suggest to take an initiative to make a uniform antibiotic registration process, to establish the MRLs for fish/shrimp and to ensure the use of only aquaculture antibiotics in fish and shellfish farming globally.

Source-specific risk apportionment and critical risk source identification of antibiotic resistance in Fenhe River basin, China

A comprehensive understanding of the sources and distribution of antibiotic resistance risk is essential for controlling antibiotic pollution and resistance. Based on surface water samples collected from the Fenhe River basin in the flood season, using the positive matrix factorization (PMF) model, the risk quotient (RQ) method and the multiple attribute decision making (MADM) method, the resistance risk and source-specific resistance risk of antibiotics were analyzed in this study. The results showed that sulfonamides (SAs) were the dominant antibiotics with a mean concentration of 118.30 ng/L, whereas tetracyclines (TCs) and macrolides (MLs) had the highest detection frequencies (100%). The significant resistance risk rate of antibiotics in the entire river basin was 48%, but no high risk occurred. The significant resistance risk rate of quinolones (QNs) was the highest (100%), followed by that of MLs and TCs. Owing to human activities, the most serious resistance risk occurred in the midstream of the river basin. The resistance risk was the lowest upstream. The antibiotics were mainly contributed by six sources. Pharmaceutical wastewater was the main source, accounting for 30%, followed by livestock discharge (22%). The resistance risk from the six sources showed clear differences, but none of the sources caused a high risk of antibiotic resistance. Pharmaceutical wastewater poses the greatest risk of antibiotic resistance in the Fenhe River basin and is widely distributed. The second greatest source was livestock discharge, which was mainly concentrated in the upstream and midstream areas. The critical sources upstream, midstream, and downstream were all pharmaceutical wastewater, whereas the sequences of other sources were different because different areas were affected by different human activities. The proposed method might provide an important reference for the identification the key source of antibiotics and management of antibiotic pollution, as well as help for the management of antibiotics in Fenhe and Shanxi Province.

Antibiotics florfenicol and flumequine in the water column and sediments of Puyuhuapi Fjord, Chilean Patagonia

Chile is a major global producer of farmed salmon in the fjords of Patagonia, and therefore a major consumer of antibiotics. We tested whether the antibiotics florfenicol and flumequine persisted in the large Puyuhuapi Fjord after the six months following mandatory concerted treatment by all salmon farms present in the fjord. Antibiotics were detected in 26% of analyzed samples, but only within the particulate phase, with concentrations of florfenicol of up to 23.1 ng L^-1, where detected. Flumequine was present in one sample at trace concentration, and neither antibiotic was detected in the dissolved phase nor in surface sediments. A fugacity-based model predicted that flumequine should theoretically remain in surface sediments at the sub-Minimal Inhibiting Concentrations (sub-MIC) previously shown to promote selection for antibiotic resistance in bacteria. Our observations suggest that surface sediments might act as a reservoir for antibiotic resistomes of bacteria, and that bacteria bearing antibiotic resistance genes could eventually become a risk for human health through the consumption of marine products.

Decomposition process of cefotaxime sodium from antibiotic wastewater by Up-flow Blanket Filter (UBF) reactor: Reactor performance, sludge characteristics and microbial community structure analysis

In this study, a novel Up-flow Blanket Filter (UBF) reactor was applied to the degradation of antibiotic wastewater. The experiments showed that when the hydraulic retention time (HRT) was 24 h and the ratio of volatile fatty acids (VFA) to alkalinity (ALK) was 0.3, the best removal efficiency was achieved in the combined packing UBF reactor, and the COD removal efficiency reached 80.1%-84.6%, exhibiting a significant difference in reaction performance from the other two reactors (P < 0.05) and a good efficiency of cefotaxime sodium removal. Moreover, the microstructure and surface characteristics of the reactor fillers were studied through scanning electron microscope (SEM) analysis, which showed that three fillers all had biofilm adhesion, but the combined packing gave best performance. Energy dispersive spectrometer (EDS) tests indicated abundant element components in the combined packing. The particle size distribution of sludge was also considered in the experiment, and the result showed the particle size of sludge increased with the operation of the reactor. In addition, microbial community structures of sludge and biofilm with the combined packing were analyzed. High-throughput sequencing confirmed the existence of Pseudomonas, which had good adaptability to antibiotic wastewater and became the dominant bacteria. Decomposition process of cefotaxime sodium after hydrolysis and anaerobic treatment was analyzed through Fourier transform infrared spectroscopy (FTIR). The reactor, which is economical, exhibited favorable performance in degrading the pollutions in the antibiotic wastewater.

Statistical approach reveals tidal effect on the antibiotics and environmental relationship with the case study of Yongjiang Estuary, China

We used statistical approach by coupling redundancy analysis with linear regression analysis, which is useful to understand potential sources of antibiotics in the tide rising and ebbing of surface water in the Yongjiang Estuary, China. This study aimed to investigate the relationship between 29 antibiotics at five sites over four seasons and 13 environmental parameters during the tide rising and ebbing durations. The results found that dissolved organic carbon (DOC), salinity, temperature and chlorophyll a (Chla) were the main factors to impact antibiotics. The concentrations of macrolides were increasing with DOC, suggesting DOC may influence the adsorption capacity of antibiotics. The concentrations of tetracyclines had significant correlation with temperature and Chla during the tide rising period. This study demonstrated a method of exploring the relationship between the concentrations of antibiotics and environmental parameters, which is beneficial to future antibiotics research in estuaries.

Occurrence, spatiotemporal variation, and ecological risk of antibiotics in the water of the semi-enclosed urbanized Jiaozhou Bay in eastern China

The occurrence, temporal variation, and spatial variation of antibiotics in coastal bays and estuaries worldwide are not well documented or understood. Fifteen target antibiotics within the five classes of β-lactams, amphenicols, macrolides, fluoroquinolones, and sulfonamides were measured during the summer and winter in the water of Jiaozhou Bay in China, which is a semi-enclosed urbanized bay. Fourteen antibiotics (excluding tylosin) were detected, thus demonstrating the widespread occurrence of their residues in the bay. The total antibiotic concentration ranged from 71.8 ng L^-1 to 840 ng L^-1 for the estuarine water, which was significantly higher than that for the bay water (38.7-181 ng L^-1). The antibiotic classes in the bay water were dominated by fluoroquinolones and β-lactams, which accounted for nearly 90% of the total antibiotic concentration. In addition, amoxicillin contamination was the most prominent among the 14 detected antibiotics as it accounted for ~44% of the total antibiotic concentration. The concentrations of amoxicillin, leucomycin, enrofloxacin, and sulfamonomethoxine in the bay water were usually higher than those reported for coastal bays and estuaries worldwide. The average total antibiotic concentration in the bay water was 84.7 ng L^-1 during the summer, which was significantly lower than that during the winter (129.0 ng L^-1). This was mainly due to high dilution by runoff during the summer. The florfenicol concentration in the bay water was significantly higher during the summer than in winter due to its higher usage in aquaculture during the summer. Spatially, the total antibiotic concentration (both summer and winter) was higher in the water along the eastern coast of the bay, where the population and hospital densities are high. However, the sum of the veterinary antibiotic concentrations was higher in the northeastern aquaculture area of the bay during the summer. A risk assessment revealed that amoxicillin and enrofloxacin could pose high risks (risk quotient of > 1) to algae in the bay. The synergic effects of pharmaceutical mixtures and the bioaccumulation of antibiotics through the food web should be considered in future studies.

Isolation and characterization of a marine bacterium Vibrio diabolicus strain L2-2 capable of biotransforming sulfonamides

Sulfonamides (SAs) have attracted much attention because of their high detection rates in natural water. In this study, a marine bacterium Vibrio diabolicus strain L2-2 was isolated which could metabolize 9 SAs to a different extent. Compared with SAs and their analogs, SAs with N-oxides of heterocyclic structure were easier to be transformed to their N⁴-acetylated metabolites or their isoxazole ring rearrangement isomers by strain L2-2. And, gene vdnatA and vdnatG were likely to be the key genes in SAs acetylation process, which might code Arylamine N-acetyltransferase. The biotransformation rates of sulfathiazole(STZ), sulfamonomethoxine(SMT), sulfadiazine(SDZ), sulfamethoxazole(SMX) and sulfisoxazole(SIX) could reach 29.39 ± 5.63, 24.97 ± 4.45, 79.41 ± 4.05, 64.64 ± 1.71, 32.82 ± 4.46% in 6 days, respectively. Besides, the overall optimal conditions for SAs biotransformation were less than 100 mg/L for total SAs in neutral or weakly alkaline medium with the salinity of 10-20‰ and additional nutrients like glucose, sucrose or glycerine. Furthermore, toxicity was demonstrated to be significantly reduced after biotransformation. Together, this study introduced a strategy to use V. diabolicus strain L2-2 to realize simultaneous removal and detoxification of multiple SAs in freshwater and seawater, and revealed SAs removal pathways and relevant molecular mechanism.

Community, Distribution, and Ecological Roles of Estuarine Archaea

Archaea are diverse and ubiquitous prokaryotes present in both extreme and moderate environments. Estuaries, serving as links between the land and ocean, harbor numerous microbes that are relatively highly active because of massive terrigenous input of nutrients. Archaea account for a considerable portion of the estuarine microbial community. They are diverse and play key roles in the estuarine biogeochemical cycles. Ammonia-oxidizing archaea (AOA) are an abundant aquatic archaeal group in estuaries, greatly contributing estuarine ammonia oxidation. Bathyarchaeota are abundant in sediments, and they may involve in sedimentary organic matter degradation, acetogenesis, and, potentially, methane metabolism, based on genomics. Other archaeal groups are also commonly detected in estuaries worldwide. They include Euryarchaeota, and members of the DPANN and Asgard archaea. Based on biodiversity surveys of the 16S rRNA gene and some functional genes, the distribution and abundance of estuarine archaea are driven by physicochemical factors, such as salinity and oxygen concentration. Currently, increasing amount of genomic information for estuarine archaea is becoming available because of the advances in sequencing technologies, especially for AOA and Bathyarchaeota, leading to a better understanding of their functions and environmental adaptations. Here, we summarized the current knowledge on the community composition and major archaeal groups in estuaries, focusing on AOA and Bathyarchaeota. We also highlighted the unique genomic features and potential adaptation strategies of estuarine archaea, pointing out major unknowns in the field and scope for future research.

Eutrophication and Related Antibiotic Resistance of Enterococci in the Minjiang River, China

Antimicrobial resistance (AMR) in the aquatic environment has received increasing attention in recent years, and growing eutrophication problems may contribute to AMR in aquatic ecosystems. To evaluate whether and how eutrophication affects AMR, 40 surface water samples were collected from the Minjiang River, Fujian Province, China. Total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD_Mn) were measured as eutrophication factors. Additionally, enterococci species were isolated and their resistance to six common antibiotics was tested. Eutrophication generally showed a trend of increasing with the flow direction of the Minjiang River, with 25 sites (62.5%) having a TN/TP value over the Redfield value (16:1), which indicated that eutrophication in this region was of phosphorus limitation. High nutrition sites were in or near urban areas. Poor quality water was found in the middle and lower reaches of the Minjiang River system. The resistance frequency of 40 enterococci isolates to the six antibiotics tested was as follows: oxytetracycline > erythromycin > ciprofloxacin > chloramphenicol > ampicillin > vancomycin (70, 50, 17.5, 12.5, 2.5, 0%), and the multi-resistant rate reached 50% with eight resistance phenotypes. AMR also increased along the direction of water flow downstream, and most of the sites with the highest AMR were in or near urban areas, as was true for nutrition levels. Positive correlations between AMR and eutrophication factors (TN, TP, and COD_Mn) were identified using the Pearson's correlation coefficient, and TN/TP generally was negatively related to AMR. These results indicated that eutrophication may induce or selective for resistance of water-borne pathogens to antibiotics, with a high resistance level and a wide resistance spectrum.

Accumulation characteristics and biological response of ginger to sulfamethoxazole and ofloxacin

The potential risk to human health of antibiotics that pass through the food chain has become an important global issue, but there are few reports on the response of ginger (Zingiber officinale) to antibiotic pollution. In this study, we investigated the enrichment characteristics and biological response of ginger to sulfamethoxazole (SMZ) and ofloxacin (OFL) residues, which are common in the environment. Lower levels of SMZ, OFL and their combined duplex treatment (SMZ+OFL) promoted the growth of ginger, but the critical doses necessary to stimulate growth differed among treatments: 10 mg L-1 SMZ, 1 mg L-1 OFL and 1 mg L-1 (SMZ+OFL) had the strongest stimulating effects. At higher dosages, the root growth and light energy utilization efficiency of ginger were impaired, and (SMZ+OFL) had the strongest inhibitory effect. Treatments with lower levels of antibiotics had no significant effect on reactive oxygen species and antioxidant enzyme activities. However, when SMZ, OFL and SMZ+OFL concentrations exceeded 10 mg L-1, the contents of H2O2, O2- and MDA continued to increase, while the activities of SOD, POD, CAT first increased and then decreased, especially in SMZ+OFL. Ginger accumulated more SMZ and OFL in rhizomes and less in leaves, and accumulation increased significantly as antibiotic concentration increased. When SMZ concentration was 1 mg L-1, the SMZ concentrations in rhizomes, roots, and leaves were 0.23, 0.15, and 0.05 mg kg-1, respectively, and the residual SMZ in the rhizome was 2.3 times higher than the maximum residue limit. The abundance of the resistance genes sul1, sul2, qnrS, and intI1 increased with increasing antibiotic concentrations, and intI1 abundance was the highest. OFL induced higher levels of intI1 expression than did SMZ.

Time-dependent synergism of five-component mixture systems of aminoglycoside antibiotics to Vibrio qinghaiensis sp.-Q67 induced by a key component

A large number of antibiotics are entering the aquatic environment accompanying human and animal excreta, which will threaten the survival of aquatic organisms and even human health. It has been found that binary mixtures of aminoglycoside (AG) exhibit additive action and can be evaluated well by a classical model, concentration addition (CA) in our past study. Therefore, to investigate the toxicity interaction within multi-component mixtures of AG antibiotics, five antibiotics, kanamycin sulfate (KAN), neomycin sulfate (NEO), tobramycin (TOB), streptomycin sulfate (STS), and gentamicin sulfate (GEN), were selected to construct five-component mixture systems by a uniform design ray method. The toxic effects (luminescence inhibition) of single antibiotic and five-antibiotic mixture systems towards a photobacterium Vibrio qinghaiensis sp.-Q67 (V. qinghaiensis) in different exposure time (0.25, 2, 4, 8, and 12 h) were determined by the time-dependent microplate toxicity analysis method. The concentration-effect data were fitted by a nonlinear least square method, toxicity interaction within mixture systems was analyzed by a CA model, and the interaction intensity was characterized by deviation from the CA model (dCA). Besides, the toxicity mechanism of five antibiotics and their five-component mixtures to V. qinghaiensis was analyzed by electron microscopy. The results show that toxicity of five antibiotics and their five-component mixture systems to V. qinghaiensis is time-dependent and has strong long-term toxicity. Different from binary AG antibiotic mixture systems, five-antibiotic mixture systems exhibit obviously time-dependent synergism. In addition, toxicity of the five-antibiotic mixtures can be 1.4 times higher than that of the mixtures without synergisms at the same concentration level. According to dCA, synergism intensity (dCA) curves of rays move slowly from the high concentration region to the medium or lower one and the maximum dCA values also increase, decrease, or first increase, then decrease with the lengthening of exposure time. The inhibition activity and synergism intensity of mixture rays have good correlation with the concentration ratios of STS, the key component for synergism. The cell morphology of V. qinghaiensis indicates the strong toxicity of five antibiotics and their mixture rays is not due to the destruction of cell structure, but the inhibition of the light-emitting activity of the photobacterium.

Multidrug resistance and diversity of resistance profiles in carbapenem-resistant Gram-negative bacilli throughout a wastewater treatment plant in Colombia

OBJECTIVES

Carbapenem-resistant Gram-negative bacilli (CRGNB) have been reported in different wastewater treatment plants (WWTPs) throughout the world; however, few studies have described the antimicrobial resistance profile in different CRGNB throughout WWTPs, information that would identify points of selection of resistant bacteria. The objective of this work was to characterize the resistance profile of CRGNB harbouring blaKPC-2 from a Colombian WWTP.

METHODS

Six samples were taken from four points of a WWTP. CRGNB were selected in chromID® CARBA and identified by 16S rRNA. Carbapenemases were determined by polymerase chain reaction (PCR), and susceptibility was assessed using VITEK2.

RESULTS

One hundred and forty-two CRGNB harbouring blaKPC-2 were detected: 41% corresponded to Aeromonas spp. (n = 58) and 59% to Enterobacteriaceae. To establish the resistance profile, 50% of the isolates were selected proportionally by family and sampling point (26 Aeromonadaceae and 45 Enterobacteriaceae). All Enterobacteriaceae showed resistance to carbapenems and penicillins + inhibitors, high percentages of resistance to ceftriaxone (88.9%), and ciprofloxacin (44.4%), and low resistance to other antibiotics (>30%). In Aeromonadaceae, 76.9% were resistant to ceftriaxone, 58% to carbapenems, and 65.4% to ciprofloxacin. Twenty-one resistance profiles were observed, the most common of which were resistant to penicillins + inhibitor, cephalosporins (third to fourth generation), and carbapenems (19%). The percentage of multidrug resistance was 91% and was similar at all points of the WWTP.

CONCLUSIONS

The high frequency of multidrug resistance and great diversity of resistance profiles observed throughout the WWTP is of concern, and shows the role of WWTP as a reservoir and dissemination source of antimicrobial resistance to water sources.

Anthropogenic impacts on the contamination of pharmaceuticals and personal care products (PPCPs) in the coastal environments of the Yellow and Bohai seas

Pharmaceuticals and personal care products (PPCPs) are recognized as one emerging group of environmental contaminants, capturing worldwide attention. These chemicals, closely connected to anthropogenic activities, are mainly transported through aquatic environments and reach coastal areas, eventually entering ocean offshore. Thus, this study concentrated on the 30 PPCPs in coastal waters of the Yellow and Bohai seas (77 sites), a fast-growing area with intensive anthropogenic activities. In general, the total concentrations of PPCPs in Chinese coastal waters (0.880-1194 ng L^-1) greatly varied and were relatively greater than those (9.91-442 ng L^-1) in Korean coastal waters. Sulfamethoxazole, sulfamethazine, oxytetracycline, ofloxacin, roxithromycin, anhydro-erythromycin, and caffeine were the seven predominant PPCPs in the coastal waters of study area. Further, we established the Predicted PPCPs Contamination Indicator (PPCI) to address potential anthropogenic activities being associated with site-specific PPCPs contamination. Three anthropogenic factors to PPCPs contamination were proven as the most influential, including (1) quantity of wastewater discharge, (2) gross product of meat, poultry, eggs and milk, and (3) gross aquatic product. The relatively high PPCI values appeared in Tianjin, Dalian, Tangshan, Yantai, and Qingdao in China and Gyeonggi and Jeonbuk in South Korea, which exhibited fairly good consistency with the corresponding PPCPs concentrations. A mini-review of the global PPCPs distributions revealed that seven priority PPCPs found in this study distributed widely in Asia rather than Europe, North America, and Australia. In general, global PPCPs contamination also reflected site- and region-specific distributions, suggesting varying usages and sources cross the region and/or country. Finally, the risk assessment suggested that ofloxacin and anhydro-erythromycin, with 36.4% and 23.4% sites higher than medium risks respectively, posed relatively high risks to sensitive algal species, Microcystis aeruginosa and Selenastrum capricornutum. Overall, the ecological risks of exposure of PPCPs in the Yellow and Bohai seas were higher compared to other regions of the world, thus the bilateral management of PPCPs between China and South Korea needs an immediate attention.

Amino-functionalized alginate/graphene double-network hydrogel beads for emerging contaminant removal from aqueous solution

Inorganic-organic composite hydrogels have attracted much attention in recent years. In this study, an amino-functionalized graphene/alginate double-network hydrogel (NH₂-DN) with excellent mechanical and adsorption properties was successfully prepared. Triethylenetetramine (TETA) was used as a crosslinker which promotes random few-layer graphene sheets stacking and resulted in a reduced graphene oxide (rGO) network, containing mesopore and macropore structures on the hydrogel surface. Compared to single network hydrogel, enhanced thermal stability and mechanical properties were achieved in NH₂-DN. The elasticity modulus was improved by approximately 3 times due to the formation of the double-network. More importantly, NH₂-DN exhibited excellent adsorption properties for typical emerging contaminants (Cu²⁺ and ciprofloxacin (CIP)). Compared with that of an ordinary graphene/alginate single-network hydrogel (SN), the adsorption capacity of the NH₂-DN for Cu²⁺ and CIP reached 153.91 mg g^-1 and 301.36 mg g^-1, respectively, which was increased by 130% and 182%, respectively. Adsorption isotherm and kinetic analyses reveal that the adsorption process of CIP onto the NH₂-DN was dominated by chemical affinity. Adsorption properties were comprehensively examined, including the effects of the solid-liquid ratios, pH, and ionic strength. NH₂-DN retained 94% of its adsorption capacity when the ionic strength was 0.5 mol L^-1 and maintained at least 87% of its adsorption capacity in weak acidic and alkaline solutions. This novel amino-functionalized organic-inorganic hydrogel has great potential in environmental applications owing to its outstanding physicochemical, mechanical, and adsorption properties for emerging contaminants in wastewater.

Individual and combined mechanistic toxicity of sulfonamides and their implications for ecological risk assessment in the Three Gorges Reservoir Area (TGRA), China

Sulfonamides (SAs) are conventional veterinary antibiotics that pose ecological risks in the aquatic environment. This study aims to evaluate the environmental concerns of SAs in the Three Gorges Reservoir Area (TGRA) and their toxicogenetic implications. Here, we employed various in vitro and in vivo bioassays to determine the combine toxicogenetic effects of SAs, which were further confirmed through applying Combination Index (CI) and Independent Action (IA) models. Among the investigated SAs, sulfamethoxazole (SMX) appeared as the individual chemical with relatively high environmental effects and elevated in vitro and in vivo toxicity. Importantly, exposure to the binary mixtures of SAs induced higher developmental toxicity and significantly perturbed the detoxification pathway in zebrafish, compared to that of individual compound exposure. Moreover, the CI and IA models indicated greater synergistic effects of SAs binary mixtures as SMX-SMR, SMX-ST, and SPY-ST on the Acinetobacter sp. Tox2 at Fa = 0.5. Contrarily, IA model predicted the additive, antagonistic and synergistic effects of SAs mixtures on the transcriptional responses of detoxification pathways in zebrafish, implying the different mode of actions (MoAs) for SAs to induce mixture toxicity in vivo. Thus, the nature of toxicological interactions of SAs should be considered while performing their ecological risk assessment.

Occurrence of antibiotics and their associations with antibiotic resistance genes and bacterial communities in Guangdong coastal areas

The concentration of 8 antibiotics and 21 antibiotic resistance genes were investigated in the coastal areas of Guangdong, China. Total concentrations of antibiotics ranged from 0.43 ng/L to 1040.31 ng/L. The concentrations of tetracyclines were much higher than that of sulfonamides in most sampling sites. The abundance of target antibiotic resistance genes ranged from 1.82 × 10⁵ to 5.9 × 10⁹ copies/mL and tetM accounted for the highest percentages of detected antibiotic resistance genes in most sampling sites. Furthermore, the dominant phyla in water samples were Proteobacteria, Bacteroidetes and Actinobacteria. The relationship between antibiotics, antibiotic resistance genes, and bacterial communities was also investigated. As a result, the abundance of sul1 was positively correlated with the concentration of sulfadiazine, sulfamethoxazole and sulfonamide p-methyl oxypyrimidine. Besides, sulfonamide p-methyl oxypyrimidine, sulfadiazine and p-aminobenzenesulfonamide were significantly correlated with the bacterial communities. These findings suggested that the residues of antibiotics in coastal areas of Guangdong affect the distribution of antibiotic resistance genes and alter the microbial communities.

Sulfadiazine biodegradation by Phanerochaete chrysosporium: Mechanism and degradation product identification

Antibiotic contaminants have become a severe environmental problem in recent years and finding effective ways to deal with this issue is of great importance. In this study, Phanerochaete chrysosporium was used to degrade sulfadiazine (SDZ), which is frequently detected in the culture medium of isolates from soil and surface water systems. The results demonstrate that 10 mg L^-1 SDZ can be completely degraded by P. chrysosporium under conditions of pH 5.7 and 30 °C within 6 days. The Q-Exactive-MS/MS analysis identified and confirmed several different SDZ degradation intermediates, and four proposed degradation pathways of SDZ were deduced. Moreover, enzyme activity tests revealed that manganese peroxidase and ligninolytic peroxidase played important roles in SDZ degradation. Moreover, a transcriptome analysis method was performed to explore the mechanism and pathways of SDZ degradation by P. chrysosporium in greater detail. The results of GO and KEGG analysis strongly suggest that the metabolism pathway is significantly activated and plays an important role in antibiotic degradation. Further, this is the first study to identify SDZ degradation intermediates and two main intermediates were found to be involved in possible SDZ degradation pathways. This study is also the first report results from RNA sequencing to evaluate genome-wide changes of P. chrysosporium to further explore SDZ degradation mechanism.

Fate of antibiotics and antibiotic resistance genes in a full-scale restaurant food waste treatment plant: Implications of the roles beyond heavy metals and mobile genetic elements

Is our food safe and free of the crisis of antibiotics and antibiotic resistance (AR)? And will the derived food waste (FW) impose AR risk to the environment after biological treatment? This study used restaurant FW leachates flowing through a 200 tons-waste/day biological treatment plant as a window to investigate the fate of antibiotics and antibiotic-resistance genes (ARGs) during the acceptance and treatment of FW. Sulfonamides (sulfamethazine, sulfamethoxazole) and quinolones (ciprofloxacin, enrofloxacin, ofloxacin) were detected during FW treatment, while tetracyclines, macrolides and chloramphenicols were not observable. ARGs encoding resistance to sulfonamides, tetracyclines and macrolides emerged in FW leachates. Material flow analysis illustrated that the total amount of antibiotics (except sulfamethazine) and ARGs were constant during FW treatment processes. Both the concentration and total amount of most antibiotics and ARGs fluctuated during treatment, physical processes (screening, centrifugation, solid-liquid and oil-water separation) did not decrease antibiotic or ARGs concentrations or total levels permanently; the affiliated wastewater treatment plant appeared to remove sulfonamides and most ARGs concentrations and total amount. Heavy metals Ni, Co and Cu were important for disseminating antibiotics concentrations and MGEs for distributing ARGs concentrations. Humic substances (fulvic acids, hydrophilic fractions), C-associated and N-associated contents were essential for the distribution of the total amounts of antibiotics and ARGs. Overall, this study implied that human food might not be free of antibiotics and ARGs, and FW was an underestimated AR pool with various determinants. Nonetheless, derived hazards of FW could be mitigated through biological treatment with well-planned daily operations.

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.

Direct photo transformation of tetracycline and sulfanomide group antibiotics in surface water: Kinetics, toxicity and site modeling

The direct photo-transformation of widely used antibiotics, including Tetracycline (TTC), chlortetracycline (CTC), sulfamethoxazole (SMX) and sulfamethazine (SMZ) were quantified for surface water by using artificial UV irradiation. The photolysis rate is directly proportional to the overlap between the absorption spectrum of the solution and the spectrum of the terrestrial sunlight. Increasing overlap fraction of Tetracycline (TC) group than Sulfanomide (Sulfa) group, the transformation of TC group is certified much faster than the sulfa group. The speciation of TC and Sulfa group antibiotics are pH-dependent and consequently influence its light adsorption spectrum. And the toxicity of the four target antibiotics along the photo-transformation was assessed. In field aquatic environment, a temporal- and spatial half-life model described the behavior of the antibiotics in water column of victoria harbour could be validated by using experimentally obtained quantum yield with the target field meteorological data. The modeling results indicated the photolysis rate of different kind of antibiotics varied differently along season, daily time and water depth. Summer, midday and surface layer of water body would be the time- and space-highlight spot in which the phototransformation are the dominant process for antibiotics concentration depletion. Seasonal variety would be enhanced for sulfa-group kind antibiotics, which having only tail overlapped with irradiation spectrum. Daily averaged half-lives of TC group were relatively stable, while the sulfa group antibiotics were found to vary from about 300 to 750 h, dependent on the seasonal change.

Spatial and seasonal variations of antibiotics in river waters in the Haihe River Catchment in China and ecotoxicological risk assessment

Concentrations of widely used antibiotics were predicted to be the highest in the Haihe River Catchment across China previously, potentially resulting in high ecotoxicological risks in this region. As a result of growing usage and regulation of antibiotic use in animals, the pattern of use may have altered temporally for different antibiotics. It is important to monitor the occurrence of antibiotics within different categories for understanding their mass loading to the catchment and the potential ecotoxicological risks involved. This study investigated the seasonal occurrence and spatial variation of 15 antibiotics in the Haihe River Catchment during 2016-2017. The investigated compounds included veterinary antibiotics, human-use antibiotics, and those intended for both human and animal use. Measurements reported from previous studies were compared with the results of this study and indicated that the use of veterinary antibiotics is probably increasing around the catchment. The ∑antibiotics concentration (i.e. the summed concentration of the 15 target antibiotics) ranged from 414 to 1951 ng/L, with an average of 821 ng/L. Discharges from wastewater treatment plants were the main sources of these compounds. The mass loading of antibiotics to the river waters was higher during wet seasons than during dry seasons. The mass fluxes of the antibiotics continuously increased towards the lower reaches of the rivers. The total annual input of the antibiotics from the Haihe River and Yongdingxin River into the Bohai Bay was 5008 kg/yr. Ofloxacin, trimethoprim, leucomycin, anhydro erythromycin and florfenicol were the predominant antibiotics, whilst amoxicillin, anhydro erythromycin, ofloxacin, norfloxacin and enrofloxacin may pose high ecotoxicological risks to the investigated aquatic ecosystem. Several antibiotics selected in this study were reported for the first time in this catchment. This study provides important information for chemical management and indicates that further monitoring is needed on the more harmful and veterinary antibiotics in the catchment.

Occurrence, fate and health risk assessment of 10 common antibiotics in two drinking water plants with different treatment processes

The occurrence of antibiotics in drinking water has become a serious problem worldwide as they are a potential and real threat to human health. In this study, the variability of 10 typical antibiotics in two drinking water plants was investigated in two seasons (n = 12). The total concentrations of target antibiotics in raw water were significantly higher in winter than in summer, which may be attributed to the more frequent occurrence of colds and respiratory diseases as well as less rainfall in winter. The efficiency in removing the antibiotics varied from -46.5% to 45.1% in water plant A (WP-A) using a conventional process and 40.3% to 70.3% in water plant B (WP-B) with an advanced treatment process. Results indicated that the antibiotics in WP-A were mainly removed via the coagulation process. However in WP-B, the ultraviolet + chlorination process played a key role in antibiotics removal, followed by the pre-ozone + coagulation process. According to the human health risk assessment, it was suggested that the risk of drinking water was significantly higher than that of skin contact. However, the risk of carcinogenesis and non-carcinogenesis caused by antibiotics was at an acceptable level.

Occurrence and ecological risk assessment of pharmaceuticals and personal care products in Taihu Lake, China: a review

The rationale behind this paper was to review the available data regarding the current knowledge on the levels and trends of pharmaceuticals and personal care products (PPCPs) in Taihu Lake. The ecological risk associated with some of the PPCPs was also assessed. 36 PPCPs have been detected in the water, sediment and biota of Taihu Lake. These contaminants primarily emanate from anthropogenic activities in and around the lake. The northern part of the lake is highly polluted as compared to other parts because it receives most effluents from wastewater treatment plants (WWTPs), and domestic and industrial waste discharge from developed cities nearby. Based on the risk quotient (RQ) values, ciprofloxacin, ofloxacin, 17β-estradiol, roxithromycin and tetracycline may present a high ecological risk to organisms living in Taihu Lake. Regular monitoring is required to check the levels of PPCPs as they are regularly released into the lake. Investigations into the joint toxicities of PPCPs to aquatic organisms and the spread of antibiotic-resistant bacteria and genes in Taihu Lake are highly recommended. Special attention in terms of policy and research should be given to the northern part of the lake.

Temporal trends and transport of perfluoroalkyl substances (PFASs) in a subtropical estuary: Jiulong River Estuary, Fujian, China

The seasonal variations and spatial distributions of fifteen perfluoroalkyl substances (PFASs) were investigated in the water of the subtropical Jiulong River Estuary (JRE) in Fujian, China. The concentrations and composition profiles of PFASs showed significant seasonal variations. ∑PFASs concentrations ranged from 4.8 to 37.6 ng L^-1, 12.2 to 110 ng L^-1 and 3.3 to 43.0 ng L^-1 in the dry, medium and wet seasons, respectively. Perfluorooctane sulfonate (PFOS) was found to be the most abundant PFAS in the dry season, with a composition of 33% ± 5%, Perfluorohexanoic acid PFHxA (47% ± 13%) and perfluoropentanoic acid (PFPeA) (52% ± 15%) were the dominant compounds in the medium and wet seasons, respectively. Seasonal and spatial distributions of ∑PFASs were different in the upstream and downstream sections. High concentration of PFHxA occurred in the medium season, and showed a linear decreasing trend from upstream to downstream. The majority of other PFASs did not show clear seasonal variation. Composition profiles indicated that the JRE was mainly contaminated by short-chain perfluoroalkyl carboxylic acids (PFCAs), shipbuilding industry, multiple wastewater and river runoff were identified as major potential sources.

Exploring the differences of antibiotic resistance genes profiles between river surface water and sediments using metagenomic approach

To better understand the potential genic communication and dissemination of antibiotic resistance genes (ARGs) in different environmental matrices, the differences of ARG profiles between river surface water and sediments were explored. Metagenomic analysis was applied to investigate the comprehensive ARG profiles in water and sediment samples collected from the highly human-impacted catchment of the Beijiang River and its river source. A total of 135 ARG subtypes belonging to 18 ARG types were identified. Generally, ARGs in surface water were more diverse and abundant than those in sediments. ARG profiles in the surface water and sediment samples were distinct from each other, but some ARGs were shared by the surface water and sediments. Results revealed that multidrug and bacitracin resistance genes were the predominant ARGs types in both surface water (0.30, 0.17 copies/cell) and sediments (0.19, 0.15 copies/cell). 73 ARG subtypes were shared by the water and sediment samples and had taken over 90% of the total detected ARG abundance. Most of the shared ARGs are resistant to the clinically relevant antibiotics. Furthermore, significant correlations between the ARGs and 21 shared genera or mobile genetic elements (MGEs) (plasmids and integrons) were found in surface water and sediments, suggesting the important role of genera or MGEs in shaping ARGs profiles, propagation and distribution. These findings provide deeper insight into mitigating the propagation of ARGs and the associated risks to public health.

Antimicrobial activity of trans-cinnamic acid and commonly used antibiotics against important fish pathogens and nonpathogenic isolates

AIMS

Antibiotics and several other chemicals have been used to prevent fish diseases. However, this situation results in economic loss for the companies in the aquaculture industry and most importantly it pollutes the environment. Cinnamic acid is a naturally occurring aromatic acid and is considered to be safe for human consumption. Therefore, in this study, the antibacterial activity of trans-cinnamic acid and commonly used antibiotics, namely chloramphenicol, vancomycin, streptomycin and erythromycin, were tested against 32 bacteria, including fish pathogens, nonpathogenic isolates and collection strains.

METHODS AND RESULTS

Trans-cinnamic acid was applied against the bacteria using the disc diffusion and microdilution method under in vitro conditions. Antibiotics were also tested under similar conditions against all tested bacteria using the disc diffusion method. The results show that among 32 bacterial strains trans-cinnamic acid exhibited potent inhibitory effect on the Gram-negative fish pathogen Aeromonas sobria. In addition, a moderate inhibition of trans-cinnamic acid of fish pathogens Aeromonas salmonicida, Vibrio (Listonella) anguillarum, Vibrio crassostreae and Yersinia ruckeri was also observed for trans-cinnamic acid in our study. On the contrary, the majority of nonpathogenic intestinal isolates were resistant to trans-cinnamic acid.

CONCLUSIONS

To the best of our knowledge, this is the first report on the antimicrobial activity of trans-cinnamic acid on 24 of the studied bacteria isolated from fish. In conclusion, trans-cinnamic acid can be used as an environmentally friendly alternative additive to prevent and control primarily A. sobria, as well as other pathogenic bacteria such as A. salmonicida, V. anguillarum, V. crassostreae and Y. ruckeri.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study indicated that trans-cinnamic acid may present an environmentally friendly alternative therapeutic agent against A. sobria infections in the aquaculture industry.

Microplastics and polycyclic aromatic hydrocarbons (PAHs) in Xiamen coastal areas: Implications for anthropogenic impacts

Microplastics and polycyclic aromatic hydrocarbons (PAHs) were investigated to study the influence of human activities and to find their possible relationship on the coastal environments, where the coastal areas around Xiamen are undergoing intensive processes of industrialization and urbanization in the southeast China. The abundance of microplastics in Xiamen coastal areas was 103 to 2017particles/m³ in surface seawater and 76 to 333 particles/kg in sediments. Concentrations of dissolved PAHs varied from 18.1 to 248ng/L in surface seawater. The abundances of microplastics from the Western Harbor in surface seawater and sediments were higher than those from other areas. Foams were dominated in surface seawater samples, however, no foams were found in sediments samples. The microscope selection and FTIR analysis suggested that polyethylene (PE) and polypropylene (PP) were dominant microplastics. The cluster analysis results demonstrated that fibers and granules had the similar sources, and films had considerably correlation with all types of PAHs (3 or 4-ring PAHs and alkylated PAHs). Plastic film mulch from agriculture practice might be a potential source of microplastics in study areas. Results of our study support that river runoff, watershed area, population and urbanization rate influence the distribution of microplastics in estuarine surface water, and the prevalence of microplastic pollution calls for monitoring microplastics at a national scale.

Characterizing the antibiotic resistance genes in a river catchment: Influence of anthropogenic activities

Previous studies on environmental antibiotics resistance genes (ARGs) have focused on the pollution sources such as wastewater treatment plants, aquaculture and livestock farms, etc. Few of them had addressed this issue in a regional scale such as river catchment. Hence, the occurrence and abundances of 23 ARGs were investigated in surface water samples collected from 38 sites which located from the river source to estuary of the Beijiang River. Among them, 11 ARGs were frequently detected in this region and 5 ARGs (sulI, sulII, tetB, tetC, and tetW) were selected for their distribution pattern analysis. The abundances of the selected ARGs were higher in the upstream (8.70×10⁶copies/ng DNA) and downstream areas (3.17×10⁶copies/ng DNA) than those in the midstream areas (1.23×10⁶copies/ng DNA), which was positively correlated to the population density and number of pollution sources. Pollution sources of ARGs along the Beijiang River not only had a great impact on the abundances and diversity, but also on the distribution of specific ARGs in the water samples. Both sulI and sulII were likely originated from aquaculture farms and animal farms, tetW gene was possibly associated with the mining/metal melting industry and the electric waste disposal and tetC gene was commonly found in the area with multiple pollution sources. However, the abundance of tetB was not particularly related to anthropogenic impacts. These findings highlight the influence of pollution sources and density of population on the distribution and dissemination of ARGs at a regional scale.

Antibiotics and antibiotic resistance genes in global lakes: A review and meta-analysis

Lakes are an important source of freshwater, containing nearly 90% of the liquid surface fresh water worldwide. Long retention times in lakes mean pollutants from discharges slowly circulate around the lakes and may lead to high ecological risk for ecosystem and human health. In recent decades, antibiotics and antibiotic resistance genes (ARGs) have been regarded as emerging pollutants. The occurrence and distribution of antibiotics and ARGs in global freshwater lakes are summarized to show the pollution level of antibiotics and ARGs and to identify some of the potential risks to ecosystem and human health. Fifty-seven antibiotics were reported at least once in the studied lakes. Our meta-analysis shows that sulfamethoxazole, sulfamerazine, sulfameter, tetracycline, oxytetracycline, erythromycin, and roxithromycin were found at high concentrations in both lake water and lake sediment. There is no significant difference in the concentration of sulfonamides in lake water from China and that from other countries worldwide; however, there was a significant difference in quinolones. Erythromycin had the lowest predicted hazardous concentration for 5% of the species (HC₅) and the highest ecological risk in lakes. There was no significant difference in the concentration of sulfonamide resistance genes (sul1 and sul2) in lake water and river water. There is surprisingly limited research on the role of aquatic biota in propagation of ARGs in freshwater lakes. As an environment that is susceptible to cumulative build-up of pollutants, lakes provide an important environment to study the fate of antibiotics and transport of ARGs with a broad range of niches including bacterial community, aquatic plants and animals.

Antibiotics in the aquatic environments: A review of lakes, China

The potential threat of antibiotics to the environment and human health has raised significant concerns in recent years. The consumption and production of antibiotics in China are the highest in the world due to its rapid economic development and huge population, possibly resulting in the high detection frequencies and concentrations of antibiotics in aquatic environments of China. As a water resource, lakes in China play an important role in sustainable economic and social development. Understanding the current state of antibiotics in lakes in China is important. Closed and semi-closed lakes provide an ideal medium for the accumulation of antibiotics and antibiotic resistance genes (ARGs). This review summarizes the current levels of antibiotic exposure in relevant environmental compartments in lakes. The ecological and health risks of antibiotics are also evaluated. This review concludes that 39 antibiotics have been detected in the aquatic environments of lakes in China. The levels of antibiotic contamination in lakes in China is relatively high on the global scale. Antibiotic contamination is higher in sediment than water and aquatic organisms. Quinolone antibiotics (QNs) pose the greatest risks. The contents of antibiotics in aquatic organisms are far lower than their maximum residual limits (MRLs), with the exception of the organisms in Honghu Lake. The lakes experience high levels of ARG contamination. A greater assessment of ARG presence and antibiotic exposure are urgent.

Highly Stable Zr(IV)-Based Porphyrinic Metal-Organic Frameworks as an Adsorbent for the Effective Removal of Gatifloxacin from Aqueous Solution

Water stable Zr-metal–organic framework nanoparticles (PCN-224 NPs, PCN refers to porous coordination network) have been solvothermally synthesized. PCN-224 NPs show spherical shape with smooth surface and particle size of approximately 200 nm. PCN-224 NPs can be stable in acid and aqueous solutions, as confirmed by powder X-ray diffraction. Gatifloxacin (GTF) adsorption measurements showed that PCN-224 NPs exhibit a high adsorption capacity of 876 mg·g⁻¹. Meanwhile, the adsorption factors, adsorption characteristics, and mechanisms of GTF were investigated in batch adsorption experiments.

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.