Antibiotic resistance genes in lakes from middle and lower reaches of the Yangtze River, China: Effect of land use and sediment characteristics

Multiple antibiotic resistance and herbicide catabolic profiles of bacteria isolated from Lake Villarrica surface sediments (Chile)

Antibiotics and herbicides are contaminants of emerging concern in aquatic environments. Lake Villarrica is a relevant freshwater body in Chile and was recently designated a 'saturated nutrient zone'. Here, we investigated the occurrence of multiple antibiotic resistance (MAR) and herbicide catabolic profiles among bacteria present in the surface sediments of Lake Villarrica. The occurrence of antibiotic-resistant genes (ARGs; blaTEM, catA and tetM) and herbicide-catabolic genes (HCGs; phnJ and atzA) was investigated by qPCR. Subsequently, the presence of culturable bacteria with multiple resistance to amoxicillin (AMX), chloramphenicol (CHL) and oxytetracycline (OXT) was studied. Forty-six culturable MAR (AMX+CHL+OXT) strains were isolated and characterized with respect to their resistance to 11 antibiotics by using a disc diffusion assay and testing their ability to use herbicides as a nutrient source. qPCR analyses revealed that ARGs and HCGs were present in all sediment samples (101 to 103 gene copies g-1), with significant (P ≤ 0.05) higher values in sites near Villarrica city and cattle pastures. The plate method was used to recover MAR isolates from sediment (103 to 106 CFU g-1), and most of the 46 isolates also showed resistance to oxacillin (100%), cefotaxime (83%), erythromycin (96%) and vancomycin (93%). Additionally, 54 and 57% of the MAR isolates were able to grow on agar supplemented (50 mg L-1) with atrazine and glyphosate as nutrient sources, respectively. Most of the MAR isolates were taxonomically close to Pseudomonas (76.1%) and Pantoea (17.4%), particularly those isolated from urbanized sites (Pucón city). This study shows the presence of MAR bacteria with herbicide catabolic activity in sediments, which is valuable for conservation strategies and risk assessments of Lake Villarrica. However, major integrative studies on sediments as reservoirs or on the fate of MAR strains and traces of antibiotics and herbicides as a result of anthropic pressure are still needed.

Occurrence and distribution of antibiotic resistance genes in urban rivers with black-odor water of Harbin, China

Antibiotic resistance gene contamination in polluted rivers remains a widely acknowledged environmental issue. This study focused on investigating the contamination conditions of antibiotic resistance genes (ARGs) in Harbin's urban black-odor rivers, specifically Dongfeng Ditch and Hejia Ditch. The research employed a SmartChip Real-Time PCR System to explore the types, abundance, and distribution of ARGs in diverse habitats, such as surface water and sediment. Additionally, the study examined the correlation of ARGs with mobile genetic elements (MGEs) and various environmental factors. It was found that antibiotic resistance genes were prevalent in both water and sediment within the black-odor ditches. The dominant types of ARGs identified included aminoglycoside, sulfonamide, multidrug-resistant, and β-lactam ARGs. Notably, the top four ARGs, in terms of relative abundance, were sul1, fox5, qacEdelta1-01 and aadA1. Most categories of ARGs have significant positive connections with MGEs, indicating that the enrichment and spreading of ARGs in rivers are closely related to MGEs. Based on the correlation analysis, it is found that environmental factors such as dissolved oxygen (DO), ammonia nitrogen (NH4-N), and phosphate (PO4-P) played a substantial role in influencing the variations observed in ARGs. By employing a risk assessment framework based on the human association, host pathogenicity, and mobility of ARGs, the identification of seven high-risk ARGs was achieved. In addition, it is important to assess the environmental risk of ARGs from multiple perspectives (abundance,detection rateand mobility). This study provides a significant reference regarding the presence of ARGs contamination in urban inland black-odor rivers, essential for assessing the health risks associated with ARGs and devising strategies to mitigate the threat of antibiotic resistance.

Tracking the impact of perfluoroalkyl acid emissions on antibiotic resistance gene profiles in receiving water by metagenomic analysis

The ecological risks posed by perfluoroalkyl acids (PFAAs) to the aquatic environment have recently been of great concern. However, little information was available on the impact of PFAAs on antibiotic resistance genes (ARGs) profiles. In this study, the receiving river of the largest fluoropolymer production facility in China was selected to investigate the effects of PFAAs on ARGs profiles. The highest PFAAs concentration for water samples near the industrial effluent discharge point was 310.9 μg/L, which was thousands times of higher than the average concentration collected at upstream sites. Perfluorooctanoic acid accounted for more than 67.2 % of ∑PFAAs concentration in water samples collected at the downstream sites, followed by perfluorohexanoic acid (3.6 %-15.9 %). 145 ARG subtypes including high-risk ARGs were detected by metagenomic technology. The results indicated that the discharge of PFAA-containing effluents had a significant impact on the abundance and diversity of ARGs in receiving waters, and PFAAs and water quality parameters (e.g., pH, NH3N, CODMn, TP) could largely affect ARG profiles. Specifically, short-chain PFAAs had similar impacts on ARG profiles compared to the restricted long-chain PFAAs. This study confirmed the potential effects of PFAAs on ARGs in aquatic environment and provided more insights into the ecological risk raised by PFAAs.

Antibiotic resistance genes profile in the surface sediments of typical aquaculture areas across 15 major lakes in China

Aquatic farming is considered as a major source of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) for the natural environment of the lakes. ARB and ARGs in the natural environment have increased quickly because of the human activities. Here, we have profiled the diversity and abundance of ARGs in sediments from the typical aquaculture areas around 15 major lakes in China using PCR and qPCR, and further assessed the risk factor shaping the occurrence and distribution of ARGs. And class 1, 2 and 3 integrons were initially detected by PCR with specific primers. ARGs were widely distributed in the lakes: Weishan Lake and Poyang Lake showed high diversity of ARGs, followed by Dongting Lake, Chao Lake and Tai Lake. Generally, the ARGs in the Middle-Lower Yangtze Plain were more abundant than those in the Qinghai-Tibet Plateau. Tetracycline resistance genes (tet(C), tet(A) & tet(M)) were prominent in sediments, and the next was AmpC β-lactamase gene group BIL/LAT/CMY, and the last was the genes resistance to aminoglycoside (strA-strB). Partial least squares path modeling analysis (PLS-PMA) revealed that livestock had a significant direct effect on the distribution of ARGs in lakes, and population might indirectly influence the profiles of ARGs by affecting the scale of livestock and aquaculture. The detectable rate of class 1, 2 and 3 integrons were 80%, 100% and 46.67%, respectively. The prevalence of integrons might play a key role in promoting more frequent horizontal gene transfer (HGT) events, resulting in the environmental mobilization and dissemination of ARGs between bacteria.

Adsorption characteristics of ciprofloxacin hydrochloride on polystyrene microplastics in freshwater

In order to reveal the adsorption mechanism of microplastics (MPs) on antibiotics, polystyrene (PS) was chosen as a typical microplastic, Fenton and high-temperature aging methods were used to obtain aged MPs particles. The adsorption behavior and mechanism of ciprofloxacin hydrochloride (CIP) on PS before and after aging were studied by batch adsorption experiments, and other influencing environmental conditions were evaluated concurrently. The results showed that the adsorption of CIP on PS was an exothermic reaction, the pseudo-second-order model and Freundlich isothermal models could fit the adsorption of CIP on PS. Aging treatment enhanced the adsorption capacity of PS to CIP, and Fenton aging for 7 days had the best effect. The highest adsorption was observed when the solution pH was 6. The adsorption capacity of microplastics gradually decreased with increasing ionic strength and the concentration of fulvic acid, while the aging microplastics changed little with the concentration of fulvic acid. The presence of both Cu (II) and CIP inhibits the adsorption of each other on microplastics. Based on the above findings, the adsorption of CIP on PS is dominated by physical adsorption, and electrostatic interactions and hydrogen bonding interactions are also important mechanisms for the adsorption of CIP on microplastics.

Adsorption of clarithromycin on polystyrene nanoplastics surface and its combined adverse effect on serum albumin

Emerging contaminants, such as antibiotics and nanoplastics, have garnered significant attention due to their potential adverse effects on diverse ecosystems. Antibiotic adsorption on the surface of nanoplastics potentially facilitates their long-range transport, leading to the synergistic effects of the complex. This research aims to examine the adsorption behavior of clarithromycin binding with polystyrene nanoplastics surface as well as their interaction between drug adsorbed polystyrene nanoplastics with serum albumin. Different spectroscopic methods were used to find out the interaction between clarithromycin and nanoplastics, under stimulated physiological conditions UV-vis spectroscopy showed a maximum of 22.8% percentage of the drug adsorbed with the polystyrene nanoplastics surface after 6 h of incubation. The fluorescence spectroscopic results demonstrated that the fluorescence intensity of serum albumin was quenched by the clarithromycin-polystyrene nanoplastics (CLA-PSNP) complex through static quenching. We calculated the number of binding stoichiometry, binding constants, and thermodynamic parameters. This study revealed that the CLA-PSNP binds to serum albumin spontaneously and its hydrophobic interactions played a significant role. The conformational changes in the structure of serum albumin were revealed from the findings of synchronous fluorescence spectra, CD spectra, and 3D fluorescence spectra, leading to the disturbance in functional activity. This study focuses valuable insights into the intermolecular interactions between clarithromycin-adsorbed polystyrene nanoplastics and serum albumin and its potential molecular-level biological toxicity.

Large-Scale Biogeographical Shifts of Abundance of Antibiotic Resistance Genes and Marine Bacterial Communities as Their Carriers along a Trophic Gradient

The role of marine environments in the global spread of antibiotic resistance still remains poorly understood, leaving gaps in the One Health-based research framework. Antibiotic resistance genes (ARGs) encoding resistance to five major antibiotic classes, including sulfonamides (sul1, sul2), tetracyclines (tetA, tetB), β-lactams (blaCTX-M, blaTEMblaVIM), macrolides (ermB, mphA), aminoglycosides (aac3-2), and integrase gene (intl1) were quantified by RT-qPCR, and their distribution was investigated in relation to environmental parameters and the total bacterial community in bottom layer and surface waters of the central Adriatic (Mediterranean), over a 68 km line from the wastewater-impacted estuary to coastal and pristine open sea. Seasonal changes (higher in winter) were observed for antibiotic resistance frequency and the relative abundances of ARGs, which were generally higher in eutrophic coastal areas. In particular, intl1, followed by blaTEM and blaVIM, were strongly associated with anthropogenic influence and Gammaproteobacteria as their predominant carriers. Water column stratification and geographic location had a significant influence on ARGs distribution in the oligotrophic zone, where the bacterial community exhibited a seasonal shift from Gammaproteobacteria in winter to Marine group II in summer.

Ecotoxicological effects of antibiotic adsorption behavior of microplastics and its management measures

Microplastics adsorb heavy metals and organic pollutants to produce combined pollution. Recently, the adsorption behavior of antibiotics on microplastics has received increasing attention. Exploring the sorption behavior of pollutants on microplastics is an important reference in understanding their ecological and environmental risk studies. In this paper, by reviewing the academic literature in recent years, we clarified the current status of research on the adsorption behavior of antibiotics on microplastics, discussed its potential hazards to ecological environment and human health, and summarized the influence of factors on the adsorption mechanisms. The results show that the adsorption behavior of antibiotics on microplastics is controlled by the physical and chemical properties of antibiotics, microplastics, and water environment. Antibiotics are adsorbed on microplastics through physical and chemical interactions, which include hydrophobic interaction, partitioning, electrostatic interaction, and other non-covalent interactions. Intensity of adsorption between them is mainly determined by their physicochemical properties. The basic physicochemical properties of the aqueous environment (e.g., pH, salinity, ionic strength, soluble organic matter content, and temperature) will affect the physicochemical properties of microplastics and antibiotics (e.g., particle size, state of dispersibility, and morphology), leading to differences in the type and strength of their interactions. This paper work is expected to provide a meaningful perspective for better understanding the potential impacts of antibiotic adsorption behavior of microplastics on aquatic ecology and human health. In the meantime, some indications for future related research are provided.

Assessing the nonlinear association of environmental factors with antibiotic resistance genes (ARGs) in the Yangtze River Mouth, China

The emergence of antibacterial resistance (ABR) is an urgent and complex public health challenge worldwide. Antibiotic resistant genes (ARGs) are considered as a new pollutant by the WHO because of their wide distribution and emerging prevalence. The role of environmental factors in developing ARGs in bacterial populations is still poorly understood. Therefore, the relationship between environmental factors and bacteria should be explored to combat ABR and propose more tailored solutions in a specific region. Here, we collected and analyzed surface water samples from Yangtze Delta, China during 2021, and assessed the nonlinear association of environmental factors with ARGs through a sigmoid model. A high abundance of ARGs was detected. Amoxicillin, phosphorus (P), chromium (Cr), manganese (Mn), calcium (Ca), and strontium (Sr) were found to be strongly associated with ARGs and identified as potential key contributors to ARG detection. Our findings suggest that the suppression of ARGs may be achieved by decreasing the concentration of phosphorus in surface water. Additionally, Group 2A light metals (e.g., magnesium and calcium) may be candidates for the development of eco-friendly reagents for controlling antibiotic resistance in the future.

Occurrence, distribution and their correlation with different parameters of antibiotics and antibiotic resistance genes in lakes of China: A review

The exposure of antibiotics and antibiotic resistance genes (ARGs) as potential threats to the environment has raised global concern. This study provides discussion on the emergence and distribution of antibiotics and ARGs in lakes. The correlation of critical water quality parameters with antibiotics and ARGs are evaluated along with their integrative potential ecological risk. Sulfonamides (∼67.18 ng/L) and quinolones (∼77.62 ng/L) were the dominant antibiotics distributed in the aqueous phase, while the quinolones and tetracyclines were the primary contamination factors in the sediment phase. The temporal and spatial distribution revealed that the antibiotic concentrations were significantly lower in summer than other seasons and the lakes in Hebei and Jiangsu provinces exhibited the highest antibiotic pollution. The detection frequency and relative abundance of sul1 gene have been the highest among all detected ARGs. Moreover, ARGs in lakes were driven by several factors, with bacterial communities and mobile genetic elements that prevailed the positive distribution of ARGs. Antibiotics have been identified as critical factors in inducing the propagation of ARGs, which could be further enhanced by chemical contaminants (e.g., heavy metals and nutrients). Involving the risk assessment strategies, research attention should be paid on three antibiotics (ofloxacin, sulfamethoxazole and erythromycin) to strengthen the policy and management of Baiyangdian Lake and East Dongting Lake. This review analysis will provide in-depth understanding to the researchers and policy-makers in formulation of strategies for remediation of antibiotic contamination in the lakes.

Characteristics of antibiotic resistance genes and microbial community distribution in Wanfeng Lake, upper Pearl River, China

Wanfeng Lake, a highland lake in the upper part of the Pearl River Basin, China, has long been disturbed by aquaculture and human activities, resulting in the accumulation of antibiotics and antibiotic resistance genes (ARGs), which pose a major threat to humans and animals. In this study, 20 antibiotics, 9 ARGs, 2 mobile genetic elements (intl1 and intl2), and microbial community structure were investigated in Wanfeng Lake. The results of the study showed that the total concentration of antibiotics in surface water was 372.72 ng/L, with ofloxacin (OFX) having the highest concentration (169.48 ng/L), posing a high ecological risk to aquatic organisms. The total concentration of antibiotics in sediments was 235.86 ng/g, with flumequine (FLU) having the highest concentration (122.54 ng/g). This indicates that the main type of antibiotics in Wanfeng Lake are quinolones. QPCR analysis results of the relative abundance of ARGs in both surface water and sediments showed that sulfonamide resistance genes > macrolide resistance genes > tetracycline resistance genes > quinolone resistance genes, indicating that sulfonamide resistance genes were the dominant type. The metagenomic results showed that the predominant microorganisms in the sediment under the phylum level were Planctomycetes, Proteobacteria, Euryarchaeota, and Chloroflexi. Pearson's correlation analysis showed a significantly positive correlation between antibiotics and environmental factors with ARGs in Wanfeng Lake and a significant positive correlation between antibiotics and ARGs with microorganisms in sediments. This suggests that there is a potential pressure of antibiotics on ARGs, while microorganisms provide the driving force for the evolution and spread of ARGs. This study provides a basis for further research on the occurrence and spread of antibiotics and ARGs in Wanfeng Lake. A total of 14 antibiotics were detected in surface water and sediments. OFX poses a high ecological risk in all points of surface water. Antibiotics and ARGs were significantly positively correlated in Wanfeng Lake. Antibiotics and ARGs in sediments were positively correlated with microorganisms.

Insight into the spatiotemporal distribution of antibiotic resistance genes in estuarine sediments during long-term ecological restoration

In this study, we aimed to investigate the long-term spatiotemporal changes in hydrodynamics, antibiotics, nine typical subtypes of antibiotic resistance genes (ARGs), class 1 integron gene (intI1), and microbial communities in the sediments of a semi-enclosed estuary during ecological restoration with four treatment stages (influent (#1), effluent of the biological treatment area (#2), oxic area (#3), and plant treatment area (#4)). Ecological restoration of the estuary reduced common pollutants (nitrogen and phosphorus) in the water, whereas variations in ARGs showed noticeable seasonal and spatial features. The absolute abundance of ARGs at sampling site #2 considerably increased in autumn and winter, while it significantly increased at sampling site #3 in spring and summer. The strong intervention of biological treatment (from #1 to #2) and aerators (from #2 to #3) in the estuary substantially affected the distribution of ARGs and dominant antibiotic-resistant bacteria (ARB). The dominant ARB (Thiobacillus) in estuarine sediments may have low abundance but important dissemination roles. Meanwhile, redundancy and network analysis revealed that the microbial communities and intl1 were key factors related to ARG dissemination, which was affected by spatial and seasonal ecological restoration. A positive correlation between low flow velocity and certain ARGs (tetM, tetW, tetA, sul2, and ermC) was observed, implying that flow optimization should also be considered in future ecological restoration to remediate ARGs. Furthermore, the absolute abundance of ARGs can be utilized as an index to evaluate the removal capacity of ARGs by estuarine restoration.

Spatiotemporal distributions of sulfonamide and tetracycline resistance genes and microbial communities in the coastal areas of the Yangtze River Estuary

In this paper, water and sediments were sampled at eight monitoring stations in the coastal areas of the Yangtze River Estuary in summer and autumn 2021. Two sulfonamide resistance genes (sul1 and sul2), six tetracycline resistance genes (tetM, tetC, tetX, tetA, tetO, and tetQ), one integrase gene (intI1), 16 S rRNA genes, and microbial communities were examined and analyzed. Most resistance genes showed relatively higher abundance in summer and lower abundance in autumn. One-way analysis of variance (ANOVA) showed significant seasonal variation of some ARGs (7 ARGs in water and 6 ARGs in sediment). River runoff and WWTPs are proven to be the major sources of resistance genes along the Yangtze River Estuary. Significant and positive correlations between intI1 and other ARGs were found in water samples (P < 0.05), implying that intI1 may influence the spread and propagation of resistance genes in aquatic environments. Proteobacteria was the dominant phylum along the Yangtze River Estuary, with an average proportion of 41.7%. Redundancy analysis indicated that the ARGs were greatly affected by temperature, dissolved oxygen, and pH in estuarine environments. Network analysis showed that Proteobacteria and Cyanobacteria were the potential host phyla for ARGs in the coastal areas of the Yangtze River Estuary.

Behavior and mechanisms of ciprofloxacin adsorption on aged polylactic acid and polyethlene microplastics

Microplastics (MPs) and antibiotics are emerging pollutants in aquatic environments. MPs can absorb antibiotics, resulting in compound pollution. Batch adsorption experiments were used to investigate the adsorption behavior of CIP on polylactic (PLA) and polyethlene (PE) under various environmental conditions. After a lengthy aging process, both MPs underwent significant physicochemical changes. The equilibrium adsorption capacities of aged PLA and PE were 0.382 mg/g and 0.28 mg/g, respectively, which increased by 18.06% and 75% compared to pristine PLA and PE. The sorption capacity of MPs increased when the pH of the solution approached the dissociation constant (6.09, 8.74) of CIP. When the salinity of the solution was 3.5%, the adsorption capacity of MPs was reduced by more than 65%. The adsorption capacity of MPs rapidly decreased when 20 mg/L fulvic acid was added. Because norfloxacin (NOR) competes for adsorption sites on the microplastic, CIP adsorption is inhibited. Based on the adsorption models, FTIR, and XPS spectra, we demonstrated that the process was monolayer adsorption, with chemical and physical mechanisms including hydrogen bonding, π-π conjugation, ion exchange, and electrostatic interactions controlling it. Thus, PLA and PE microplastics may be a potential vector for CIP in water, and their interaction is mainly influenced by the physicochemical properties of the MPs and environmental factors.

Occurrence and influencing factors of antibiotics and antibiotic resistance genes in sediments of the largest multi-habitat lakes in Northern China

Baiyangdian Lake is a typical and largest multi-habitat lake in the North plain of China. To understand the generation and transmission of antibiotics resistance genes (ARGs) in multi-habitat lakes, the contents of nutrients (TC, TOC, TN, TP and TS), heavy metals (Zn, Cr, Ni, Cu, Pb, As, Cd and Hg), 22 antibiotics, 16S-rRNA(16S), Class I integron (intI1) and 20 ARGs were determined. Samples were taken from the Fuhe river, river estuaries, reed marshes, living area, fish ponds and open water of Baiyangdian Lake. The results showed that quinolones were the main pollutants in six habitats, and the content range was ND-104.94 ng/g. Thereinto, aac (6') -IB, blaTEM-1, ermF, qnrA, qnrD, tetG, sul1, sul2 and tetM were detected in all the analyzed samples. The absolute abundance of sul1 was the highest (5.25 × 10⁵ copies/g-6.21 × 10⁷ copies/g) in most of the samples. In these different habitats, the abundance of antibiotics and ARGs in river estuary was the highest, and that in reed marshes was the lowest. There was a significant positive correlation between the abundance of heavy metals (Cu, Pb, Zn, Ni, Cd, Hg) and the absolute abundance of 11 ARGs (P < 0.01). Redundancy analysis showed that Cu, Zn, intI1, TP and macrolides were the important factors affecting the distribution of ARGs. Our finding provides a more likely driving and influencing factor for the transmission of ARGs in lakes with complex and diverse habitats.

Field ponding water exacerbates the dissemination of manure-derived antibiotic resistance genes from paddy soil to surrounding waterbodies

Farmlands fertilized with livestock manure-derived amendments have become a hot topic in the dissemination of antibiotic resistance genes (ARGs). Field ponding water connects rice paddies with surrounding water bodies, such as reservoirs, rivers, and lakes. However, there is a knowledge gap in understanding whether and how manure-borne ARGs can be transferred from paddy soil into field ponding water. Our studies suggest that the manure-derived ARGs aadA1, bla1, catA1, cmlA1-01, cmx(A), ermB, mepA and tetPB-01 can easily be transferred into field ponding water from paddy soil. The bacterial phyla Crenarchaeota, Verrucomicrobia, Cyanobacteria, Choloroflexi, Acidobacteria, Firmicutes, Bacteroidetes, and Actinobacteria are potential hosts of ARGs. Opportunistic pathogens detected in both paddy soil and field ponding water showed robust correlations with ARGs. Network co-occurrence analysis showed that mobile genetic elements (MGEs) were strongly correlated with ARGs. Our findings highlight that manure-borne ARGs and antibiotic-resistant bacteria in paddy fields can conveniently disseminate to the surrounding waterbodies through field ponding water, posing a threat to public health. This study provides a new perspective for comprehensively assessing the risk posed by ARGs in paddy ecosystems.

Systematic review: External carbon source for biological denitrification for wastewater

Nitrogen mitigation is serious environmental issue around the globe. Several methods for wastewater treatment have been introduced, but biological denitrification has been recommended, particularly with addition of the best external carbon source. The key sites of denitrification are wetlands; it can be carried out with different methods. To highlight the aforementioned technology, this paper deals to review the literature to evaluate biological denitrification and to demonstrate cost effective external carbon sources. The results of systematic review disclose the denitrification process and addition of different external carbon sources. The online literature exploration was accomplished using the most well-known databases, that is, science direct and the web of science database, resulting 625 review articles and 3084 research articles, published in peer-reviewed journals between 2015 and 2021 were identified in first process. After doing an in-depth literature survey and exclusion criteria, we started to shape the review from selected review and research articles. A number of studies confirmed that both nitrification and denitrification are significant for biological treatment of wastewater. The studies proved that the carbon source is the main contributor and is a booster for the denitrification. Based on the literature reviewed it is concluded that biological denitrification with addition of external carbon source is cost effective and best option in nitrogen mitigation in a changing world. Our study recommends textile waste for recovery of carbon source.

Construction of titanium-aluminum xerogel composite coagulant for removal of tetracycline in water: synergy effects and improvement mechanisms insight

Titanium xerogel coagulant (TXC) is a new type of coagulant that has attracted much attention in recent years. However, the tetracycline removal performance of TXC was not satisfactory because low isoelectric point (pH_iep) inhibited the electrical neutralization efficiency of TXC in an alkaline environment. To overcome this shortcoming, a composite xerogel coagulant (titanium-aluminum xerogel composite coagulant) was prepared. The removal of tetracycline and turbidity was used as evaluation indexes. It was proved that the combination of aluminum (III) and titanium (IV) enhanced the resistance of TXC to pH. The synthesized titanium-aluminum xerogel composite coagulant (TXAC) has an excellent removal ability of tetracycline in a wide pH range (pH = 5-10). At pH 8.8, the dosage required to remove 80% tetracycline from water decreased from 93 (TXC) to 35 mg/L (TXAC). The reason for this improvement could be attributed to (i) aluminum (III) enhanced the electric neutralization of TXC to negatively charged pollutants in an alkaline environment; (ii) the complexing ability of organic matter and aluminum (III) was enhanced. This work provides a feasible scheme for the pretreatment of tetracycline in water to meet the pretreatment requirements of special water.

Distribution of antibiotic resistance genes in the sediments of Erhai Lake, Yunnan-Kweichow Plateau, China: Their linear relations with nonpoint source pollution discharges from 26 tributaries

Erhai Lake, a typical plateau deep water lake, experienced long-term nonpoint source (NPS) pollution discharge from 26 tributaries, which significantly affected the abundance and spread of resistance genes. In this study, 25 antibiotic resistance genes (ARGs), classified into six types, and NPS pollution discharges were investigated throughout around the Erhai basin. FCA (mexF) and sulfonamide resistance genes (sul1, sul2 and sul3) were the most common. Although the absolute overall abundance of ARGs there was low so far, the individual gene like sulfonamide resistance gene was high. Regression analysis using an ordinary least squares model (OLS) showed that the discharge of NPS pollution into Erhai Lake would have an obvious effect on the distribution of ARGs. And the relations between them were linear. Concretely speaking, the total nitrogen (TN) pollution input from tributaries could significantly correlated with the increasing of ARG abundance, while the total phosphorus (TP) pollution input showed the opposite correlation, and ultimately affect the distribution of ARGs. Moreover, the effect of TP on ARG distribution was more significant than TN. This study provides a geographical profile of ARG distribution in a subtropical deep lake on Yunnan-Kweichow Plateau. The results are beneficial for predicting the distribution characteristics of ARGs and controlling their pollution in plateau lakes.

Deterministic assembly process dominates bacterial antibiotic resistome in wastewater effluents receiving river

Antibiotic resistance has become a concerning global health challenge, such as the dissemination of bacteria and genes between humans and the environments. Wastewater treatment plants (WWTPs) effluents, as significant reservoirs for antimicrobial resistant bacteria and antibiotic resistance genes (ARGs), pose critical risks to public health. However, whether wastewater effluent prominently contributes to the abundance of ARGs and their community assembly processes in receiving river has yet been unclear. Here we investigated the effects of the effluent discharge on the ARGs and their associate microbial community in the receiving river (Qinhuai River, Nanjing) of upstream and 2000 m downstream of one WWTPs discharge point. Results revealed that the total antibiotic concentrations of all sediment samples ranged from 37.86 to 76.11 µg/kg dw, while antibiotic concentrations and ARG abundances in the river near the wastewater discharge site were significantly higher than that of the downstream receiving river. The metagenomic assembly obtained 245 ARGs associated with 19 antibiotic types in the receiving river. Network analyses confirmed that Proteobacteria, Firmicutes, Acidobacteria, and Bacteroides were the key phylum and positively correlated with the antibiotic resistome. Additionally, the bacterial pathogens of the receiving river were identified as the most frequent strains of clinically relevant antibacterial resistance, such as Streptococcus pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Using null modeling analysis to determine the quantification of ecological processes, the results showed that heterogeneous environmental selection (81.81%) was a dominate role of the ecological mechanisms determining the ARG community reconstruction in the receiving river. Our results may contribute to control the environmental dissemination of antimicrobial resistance risks in aquatic environments.

Non-corresponding contaminants in marine surface sediments as a factor of ARGs spread in the Sea of Azov

The present study aims to analyze the level and total toxicity of the most common pollutants in surface sediments and assess their impact on the occurrence of antibiotic resistance genes (ARGs) in the Sea of Azov. Biotesting using the whole-cell bacterial lux-biosensors showed high integral toxicity of surface sediments and the presence of genotoxicants and substances that cause oxidative stress and protein damage. Using cluster analysis, it was shown that the distribution of pollutants in the Sea of Azov depends on the type of surface sediments. The relative abundance and distribution of 14 ARGs in surface sediments were shown. Principle component analyses results suggest that non-corresponding contaminants do not exert direct influence on the ARGs abundance in the surface sediments of the Sea of Azov. Thus, the need to investigate the significance of non-corresponding pollutants in the selection and distribution of ARGs in the aquatic environment remains a pressing problem.

Aquatic Environments as Hotspots of Transferable Low-Level Quinolone Resistance and Their Potential Contribution to High-Level Quinolone Resistance

The disposal of antibiotics in the aquatic environment favors the selection of bacteria exhibiting antibiotic resistance mechanisms. Quinolones are bactericidal antimicrobials extensively used in both human and animal medicine. Some of the quinolone-resistance mechanisms are encoded by different bacterial genes, whereas others are the result of mutations in the enzymes on which those antibiotics act. The worldwide occurrence of quinolone resistance genes in aquatic environments has been widely reported, particularly in areas impacted by urban discharges. The most commonly reported quinolone resistance gene, qnr, encodes for the Qnr proteins that protect DNA gyrase and topoisomerase IV from quinolone activity. It is important to note that low-level resistance usually constitutes the first step in the development of high-level resistance, because bacteria carrying these genes have an adaptive advantage compared to the highly susceptible bacterial population in environments with low concentrations of this antimicrobial group. In addition, these genes can act additively with chromosomal mutations in the sequences of the target proteins of quinolones leading to high-level quinolone resistance. The occurrence of qnr genes in aquatic environments is most probably caused by the release of bacteria carrying these genes through anthropogenic pollution and maintained by the selective activity of antimicrobial residues discharged into these environments. This increase in the levels of quinolone resistance has consequences both in clinical settings and the wider aquatic environment, where there is an increased exposure risk to the general population, representing a significant threat to the efficacy of quinolone-based human and animal therapies. In this review the potential role of aquatic environments as reservoirs of the qnr genes, their activity in reducing the susceptibility to various quinolones, and the possible ways these genes contribute to the acquisition and spread of high-level resistance to quinolones will be discussed.

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.

Seasonal dynamics survey and association analysis of microbiota communities, antibiotic resistance genes distribution, and biotoxicities characterization in landfill-leachate

OBJECTIVE

To reflect the potential and intrinsic association among microbiota structure, antibiotic resistance genes distribution and biological toxicity of landfill-leachate according to seasonal change, and accurately assess the potential threat of leachate to the surrounding environment.

METHODS

On the basis of the leachate water quality monitoring data from January to December 2020, principal component analysis (PCA) was used to identify the main pollutants in the leachate; Vibrio fischeri luminescence inhibition test was used to detect the comprehensive biotoxicity of the leachate; 16S rDNA amplicon sequencing was used for leachate microbiota. q-PCR was used to detect the class 1 integron (intI1), and eight antibiotic resistance genes (sul1, sul2, tetA, tetB, tetM, tetQ, mefA, and mexF); Canonical correspondence (CCA) analysis was carried out for the association analysis.

RESULT

The biotoxicity of leachate in the second quarter was the highest. The dominant phylum of leachate microbiota from 1st quarters to 4th quarters was Proteobacteria (94.97 %, 85.43 %, 88.20 %, and 84.11 %), and the dominant genera were Thiomonas (60.41 %, 26.83 %, 25.66 %, and 30.51 %), Pseudomonas (5.89 %, 1.86 %, 0.68 %, and 4.72 %), Desulfurella (8.52 %, 0.57 %, 3.81 %, and 8.25 %), and Acidithiobacillus (4.71 %, 0.69 %, 0.87 %, and 5.91 %); Nitrospirillum was negatively correlated with chemical oxygen demand (COD) (R=-0.561, P = 0.008) and five-day biochemical oxygen demand (BOD₅) (R=-0.591, P = 0.005); Limnohabitans was positively correlated with pH (R=0.444, P = 0.044). Four AR genes (sul1, sul2，tetM, and tetQ) were detected in all the samples, while the second quarter had the highest concentration of sul1(6.31 ± 0.49 lg copies/ng DNA), tetM (3.01 ± 1.38 lg copies/ng DNA) and tetQ (3.64 ± 0.90 lg copies/ng DNA).

CONCLUSION

As the mature landfill, the quality of this leachate met the pollution control standards for domestic waste landfills. Thiomycetes, Pseudomonas, Desulfurization, and Thiopterus acidophyllum constitute the dominant microbiota. However, leachate in the second quarter had more serious contamination, the higher biotoxicity, higher concentration of AR genes, together with higher microbiota richness and diversity, which deserved more attention for the potential threat to the surrounding environment.

Diversity and abundance of antibiotic resistance genes and their relationship with nutrients and land use of the inflow rivers of Taihu Lake

Taihu Lake is the third largest freshwater lake in China and an important source for drinking water, flood protection, aquaculture, agriculture, and other activities. This lake is connected to many principal and small rivers with inflow from west and outflow on the eastern side of the lake and these inflow rivers are believed to significantly contribute to the water pollution of the lake. This study was aimed at assessing the diversity and abundance of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), and their relationship with water quality parameters and land use patterns. Water samples were collected from 10 major inflow rivers and the source water protection area of the Taihu Lake in spring and summer 2019. High-throughput profiling was used to detect and quantify 384 ARGs and MGEs and in addition, 11 water quality parameters were analyzed. The results showed that the number of ARGs/MGEs detected in each inflow river ranged from 105 to 185 in spring and 107 to 180 in summer. The aminoglycoside resistance genes were the most dominant types ARGs detected followed by beta-lactam resistance, multidrug resistance, macrolide-lincosamide-streptogramin B (MLSB) resistance genes, which contributed to 65% of the ARGs. The water quality parameters showed significant correlation with absolute abundance of ARGs. Furthermore, significant correlation between ARGs and MGEs were also observed which demonstrates potential gene transfer among organisms through horizontal gene transfer via MGEs. ARGs showed strong positive correlation with cultivated and industrial lands whereas, negative correlation was observed with river, lake, forest, land for green buffer, and land for port and harbor. The overall results indicate that the inflow rivers of Taihu Lake are polluted by various sources including multiple nutrients and high abundance of ARGs, which needs attention for better management of the inflow rivers of this lake.

Distribution and model prediction of antibiotic resistance genes in Weishan Lake based on the indication of Chironomidae larvae

The widespread contamination of antibiotic resistance genes (ARGs) in freshwater environment are becoming a serious challenge to human health and ecological safety. Rapid and efficient monitoring of ARGs pollution is of great significance to ARGs control. Water, bottom mud, and fish have all been used to indicate ARG contamination in aquatic environments. However, it is unclear whether macrobenthic invertebrates in the food chain of aquatic environments can be indicators of ARG contamination. In this study, we demonstrated that ARGs including tetA gene, sul2 gene, and km gene were distributed in Chironomidae larvae in Weishan Lake. The ARG distribution was related to animal species, body parts, sampling sites, time, urban environment, animal farming, south-to-north water diversion, food chain, antibiotics, and water storage. Mathematical model predictions of ARG contamination in Weishan Lake were constructed based on the structural equation model (SEM) and the distribution of ARG sul2 in Chironomidae larvae. Influencing factors such as water storage, metal elements, antibiotic, and temperature were found to be closely related to the prediction of ARG contamination. This study provided a new indicator for ARG contamination in freshwater environments and a method to predict ARGs contamination.

Metagenomics-based antibiotic resistance genes diversity and prevalence risk revealed by pathogenic bacterial host in Taihu Lake, China

In recent decades, antibiotics and antibiotic resistance genes (ARGs) have been regarded as emerging pollutants. In Taihu Lake, as a typical representative of freshwater system in China, the ARGs occurrence and abundance was of great importance for ecological risk control and public health protection. In this research, high-throughput sequencing and metagenomics technique were used to investigate the seasonal ARGs profile in overlying water and sediment at typical area of Taihu Lake. Besides, taxonomy pattern of ARGs host bacteria and potential pathogens were identified. The results showed that 33 ARG subtypes and 11 ARG types were detected in research area, among which bacitracin, multidrug and sulfonamides resistance gene were with the highest abundance. The relative abundance of ARGs in overlying water and sediment ranged from 1.68 to 661.05 ppm and from 1.93 to 49.47 ppm, respectively. ARG host (18 bacteria genus) were identified and annotated, among which Clostridium botulinum, Pseudomonas aeruginosa and Klebsiella pneumonia were pathogenic bacteria. The pathogens were mostly detected at Xukou Bay in spring and fall, which might be caused by the inlet water from aquaculture area of Yangcheng Lake. Pseudomonas was the most abundant ARGs host (ant2ib, baca, bl2d_oxa2,mexb, mexf, mexw and oprn), which may facilitate the propagation of ARGs in freshwater system.

Antibiotic resistance genes and their links with bacteria and environmental factors in three predominant freshwater aquaculture modes

Rapid development of aquaculture industry and increasing demand of various inputs (especially antibiotics), are suspected to promote the occurrence and spread of ARGs in aquaculture related environments. However, the occurrences of ARGs under different freshwater aquaculture practices are rarely known. Here, we investigated the seasonal profiles of the main ARGs, intI1 and bacteria in waters from three kinds of predominant freshwater aquaculture practices around the Honghu Lake (China), as well as their co-occurrences and interrelationships with antibiotics, heavy metals and general water quality. The results indicate that quinolone resistance genes (qnrB), tetracycline resistance genes (tetB and tetX) and sulfonamide resistance genes (sul1 and sul2) were the top five predominant ARGs with seasonal variations of abundance. Fish ponds were of the highest absolute abundances of tested ARGs than the other two modes. Crayfish ponds and their adjacent ditches shared similar ARGs profile. Different subtypes of ARGs belonging to the same class of resistance were varied in abundances. Some bacteria were predicted to carry different ARGs, which indicating multi-antibiotic resistances. Moreover, the combined environmental factors (antibiotics, heavy metals and water quality) partially shaped the profiles of ARGs and bacteria composition. Overall, this study provides new comprehensive understanding on the characterization of ARGs contamination in different freshwater aquaculture practices from the perspectives of environmental chemistry, microbiology and ecology. The results would benefit the optimization of aquaculture practices toward environmental integrity and sustainability.

Distribution of Sulfonamide Antibiotics and Resistance Genes and Their Correlation with Water Quality in Urban Rivers (Changchun City, China) in Autumn and Winter

With the extensive use of antibiotics, antibiotics, and antibiotic resistance genes (ARGs), contamination in the water environment is becoming severe in recent years. This study examined the distribution characteristics of sulfonamide antibiotics and resistance genes in the urban section of the Yitong River in autumn and winter. In addition, the correlation between them and water quality parameters was analyzed using Pearson correlation analysis. The surface water from the Yitong River was sampled in September and November for this experiment. The results of 32 samples showed that seven sulfonamides were detected in the surface water and sediments of this reach, and the concentrations were generally at the levels of ng/L and ng/g. The total concentration range was 11–161 ng/L and ND-85.7 ng/g. The concentrations of different antibiotics were similar in autumn and winter, and the concentration of sulfamethoxazole (SMX) was higher than that of other antibiotics. The results of the Risk Quotients (RQs) showed that SMX and sulfadiazine (SDZ) had moderate acute risk to the corresponding sensitive species in river water, sulfapyridine (SPD) and sulfisoxazole (SIZ) had low acute risk, while the rest had no risk. The total bacterial abundance in surface water and sediment was in the range of 104–105 copies/mL and 108–1011 copies/g, respectively. The detection rates of three sulfonamide resistance genes were 100%; the relative abundance was in the range of 10−3–10−1 copies/16S rRNA, and sul1 was the primary resistance gene. The results of correlation analysis showed that there was a significant positive correlation between sulfamethazine (SMZ), sulfathiazole (STZ), and SIZ and water quality indexes such as total nitrogen (TN) and total phosphorus (TP), ammonia nitrogen (NH3-N) and chlorophyll a (Chl-a). The river‘s change of water quality environment could significantly affect the antibiotics’ spatial distribution characteristics and content. The higher the level of nutrients, the higher the concentration of antibiotics. The abundance of sulfa resistance genes was positively correlated with the concentration of sulfa antibiotics. Frequent human activities can increase antibiotic concentration, leading to the production of more resistance genes induced by antibiotics, but the main reason for the formation of resistance genes was not apparent. Therefore, exploring the occurrence and pollution characteristics of antibiotics and ARGs in the environment of the Yitong River Basin in Changchun City and analyzing their sources, transmission, and ecological risks in the environment provided an essential scientific basis for pollution prevention and ecological protection of urban rivers in northern China.

Comparative analysis of antibiotic resistance genes on a pig farm and its neighboring fish ponds in a lakeside district

Antibiotics usage in animal production is considered a primary driver of the occurrence, supply and spread of antibiotic resistance genes (ARGs) in the environment. Pig farms and fish ponds are important breeding systems in food animal production. In this study, we compared and analyzed broad ARGs profiles, mobile genetic elements (MGEs) and bacterial communities in a representative pig farm and neighboring fish ponds around Poyang Lake, the largest freshwater lake in China. The factors influencing the distribution of ARGs were also explored. The results showed widespread detection of ARGs (from 57 to 110) among 283 targeted ARGs in the collected water samples. The differences in the number and relative abundance of ARGs observed from the pig farm and neighboring fish ponds revealed that ARG contamination was more serious on the pig farm than in the fish ponds and that the water treatment plant on the pig farm was not very effective. Based on the variance partition analysis (VPA), MGEs, bacterial communities and water quality indicators (WIs) codrive the relative abundance of ARGs. Based on network analysis, we found that total phosphorus and Tp614 were the most important WIs and MGEs affecting ARG abundance, respectively. Our findings provide fundamental data on farms in lakeside districts and provide insights into establishing standards for the discharge of aquaculture wastewater.

Metagenomic analysis of microbial community structure and distribution of resistance genes in Daihai Lake, China

The emergence of resistance genes is a global phenomenon that poses a significant threat to both animals and humans. Lakes are important reservoirs of genes that confer resistant to antibiotics and metals. In this study, we investigated the distribution and diversity of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) in the sediment of Daihai Lake using high-throughput sequencing and metagenomic analysis. The results indicated that all sampling sites had similar bacterial community structures, with Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes being the most abundant. A total of 16 ARG types containing 111 ARG subtypes were deposited in the sediment. Among the resistance genes to bacitracin, multidrug, macrolide-lincosamide-streptogramin (MLS), tetracycline, beta-lactam, and sulfonamide were the dominant ARG types, accounting for 89.9-94.3% of the total ARGs. Additionally, 15 MRG types consisting of 146 MRG subtypes were identified. In all samples, MRGs of the same type presented resistance to Pb, Ni, Hg, W, Zn, Ag, Cr, Fe, As, Cu, and multimetals. Overall, the distribution and diversity of antibiotic and metal resistance genes showed no significant differences in the samples. Plasmids (91.03-91.82%) were the most dominant mobile genetic elements in the sediments of Daihai Lake. Network analysis indicated that the target ARGs and MRGs were significantly positively correlated with the microorganisms. Potential hosts for various ARGs and MRGs include Proteobacteria, Euryarchaeota, Actinobacteria, Chloroflexi, and Bacteroidetes.

Monitoring and evaluation of antibiotic resistance genes in three rivers in northeast China

Antibiotic resistance genes (ARGs) have become an important public health problem. In this study, we used metagenomic sequencing to analyze the composition of ARGs in selected original habitats of northeast China, comprising three different rivers and riverbank soils of the Heilongjiang River, Tumen River, and Yalu River. Twenty types of ARG were detected in the water samples. The major ARGs were multidrug resistance genes, at approximately 0.5 copies/16S rRNA, accounting for 57.5% of the total ARG abundance. The abundance of multidrug, bacitracin, beta-lactam, macrolide-lincosamide-streptogramin, sulfonamide, fosmidomycin, and polymyxin resistance genes covered 96.9% of the total ARG abundance. No significant ecological boundary of ARG diversity was observed. The compositions of the resistance genes in the three rivers were very similar to each other, and 92.1% of ARG subtypes were shared by all water samples. Except for vancomycin resistance genes, almost all ARGs in riverbank soils were detected in the river water. About 31.05% ARGs were carried by Pseudomonas. Opportunistic pathogenic bacteria carrying resistance genes were mainly related to diarrhea and respiratory infections. Multidrug and beta-lactam resistance genes correlated positively with mobile genetic elements (MGEs), indicating a potential risk of diffusion. The composition of ARGs in three different rivers was similar, indicating that climate plays an important role in ARG occurrence. ARG subtypes in river water were almost completely the same as those in riverbank soil. ARGs had no significant geographical distribution characteristics. Many ARGs were carried by human pathogenic bacteria related to diarrhea and respiratory infections, such as Pseudomonas aeruginosa and Aeromonas caviae. In general, our results provide a valuable dataset of river water ARG distribution in northeast China. The related ecological and geographical distribution characteristics should be further explored.

Linkage and driving mechanisms of antibiotic resistome in surface and ground water: Their responses to land use and seasonal variation

Antibiotic resistance in the environment, mostly mediated by antibiotic resistance genes (ARGs), has posed a threat to ecological and human health. Contamination of surface water and groundwater with ARGs has become a serious environmental concern. However, the distinctions and similarities across ARG profiles, the various ecological processes associated with ARGs, the driving mechanisms for ARG profiles in surface water and groundwater, and how they respond to land use and seasonal variation remain unknown. To tackle these issues, the contamination of ARGs in surface water and groundwater in central China was investigated using metagenomic technology. The results indicated that seasonal changes in ARG abundance and diversity were inconsistent across surface water and groundwater, and that the relationship between ARGs in surface water and groundwater was stronger during the rainy season. Land use had a greater effect on ARGs in surface water than in groundwater and was stronger during the dry season than during the rainy season. More interestingly, the ideal buffer zones with the greatest impact of land use on the ARGs of surface water and groundwater had distinct radii: 1500 m for both dry and rainy seasons in surface water, and 1000 m for dry season and 500 m for rainy season in groundwater. Furthermore, stochastic mechanisms mediated by mobile gene elements (MGEs) contribute significantly more to ARG assemblages than deterministic processes, particularly in groundwater. Furthermore, our results also showed that ARG enrichment in microbial communities was host- dependent, and the risk of ARGs in groundwater was greater both during the rainy season and dry season. In conclusion, the findings have improved our understanding of the relationship and driving mechanisms of ARGs in surface and ground water, as well as their responses to land use and seasonal variation, which may be beneficial for limiting ARG pollution in a watershed with high levels of anthropogenic activity.

Fate of land-based antibiotic resistance genes in marginal-sea sediment: Territorial differentiation and corresponding drivers

No large-scale investigations on fate of land-based antibiotic resistance genes (ARGs) in marginal sea have been reported. The Yellow Sea which is an important marginal sea was selected to investigate the fate, territorial differentiation, and drivers of target ARGs in marginal-sea sediments. ARGs might spread from land to sea with the average absolute abundance of total ARGs in marine/coastal sediments reaching 1.23 × 10⁴/9.79 × 10⁴ copies/g. The Yellow Sea Cold Water Mass was firstly observed to possibly have potential inhibition effect on occurrence of ARGs in marine sediments. Marine sediments showed significant difference from coastal sediments by considering ARGs, microbial community, and sediment features. Network analysis showed that interaction between ARGs and microbial community in coastal sediments was more frequent than that in marine sediment. The anthropogenic factors posed high positive effect on ARGs in marine/coastal sediments with contribution coefficient of 0.524/1.094 while bacterial community mainly posed positive effect on ARGs in marine sediments with contribution coefficient of 0.475, illustrating that spread and proliferation of land-based ARGs in marine sediments might be mainly affected by anthropogenic and microbial factors. These findings provided new information on fate and drivers of ARGs in marginal sea.

Assessing the role of polyethylene microplastics as a vector for organic pollutants in soil: Ecotoxicological and molecular approaches

Microplastics (MPs), pharmaceuticals and pesticides are emerging pollutants with proposed negative impacts on the environment. Rising interest in investigations of MPs is likely related to their potential to accumulate in agricultural systems as the base of the food chain. We applied an integrated approach using classic bioassays and molecular methods to evaluate the impact associated with a mixture of three types of polyethylene (PE) microbeads, namely, white (W), blue (B), and fluorescent blue (FB), and their interactions with pollutants (OCs), including ibuprofen (IB), sertraline (STR), amoxicillin (AMX) and simazine (SZ), on different soil organisms. PE-MPs exhibited different abilities for the adsorption of each OC; W selectively adsorbed higher amounts of SZ, whereas B and FB preferably retained AMX. Standard soil was artificially contaminated with OCs and MPs (alone or combined with OCs) and incubated for 30 days. The presence of MPs or MPs and OCs (MIX) in soil did not produce any effect on Caenorhabditis elegans endpoint growth, reproduction, or survival. Inhibition of leaf growth in Zea mays was detected, but this negative effect declined over time, while the inhibition of root growth increased, especially when OCs (32%) or MIX (47%) were added. Moreover, the expression of the antioxidant genes CAT 1, SOD-1A and GST 1 on plants was affected by the treatments studied. The addition of MPs or MIX significantly affected the soil bacterial phylogenetic profile, which selectively enriched members of the bacterial community (particularly Proteobacteria). The predicted functional profiles of MP/MIX samples indicated a potential impact on the carbon and nitrogen cycle within the soil environment. Our results indicate that MPs and their capability to act as pollutant carriers affect soil biota; further studies should be carried out on the bioavailability of OCs adsorbed by microplastics and how long it takes to leach these OCs into different organisms and/or ecosystems.

Relationship between water quality, heavy metals and antibiotic resistance genes among three freshwater lakes

Urban recreational lakes are impacted by consistent anthropogenic activities and are significant sources of heavy metals and antibiotic resistance genes (ARGs). In this study, three urban lakes of varying size and anthropogenic impact in Nanjing, China, were investigated for the abundance of ten ARGs, six physicochemical factors and four heavy metals. Correlations between heavy metals and physicochemical parameters against ARGs were performed to investigate the presence of ARGs in the lakes. The water quality data indicated that the lakes were on par with levels 3 and 4 of the Chinese surface water environmental standards, signifying disturbing pollution levels in the lakes. The lakes were dominant with high amounts of sul1, sul2 and strA genes, and the sum of these three genes appropriated over 38.9-84.4% in all three lakes, while the sum of tetM, tetQ and ermB genes occupied a minor proportion (0.1-1.4%). High levels of vancomycin resistance genes were found in the three lakes. Spearman analysis indicated that Chlα, cadmium, lead and copper had a significant positive correlation with sul2 and strB. The results of redundancy analysis displayed that Chlα and co-selection with certain heavy metals were the major factors driving the propagation of specific genes in three lakes. We believe our study contributes by adding further knowledge to existing antibiotic resistance gene abundance studies in recreational urban lakes with significant anthropogenic impacts.

Abundance and Dynamic Distribution of Antibiotic Resistance Genes in the Environment Surrounding a Veterinary Antibiotic Manufacturing Site

Background: Antibiotics releasing from the manufacturing sites to the surrounding environment has been identified as a risk factor for the development of antibiotic resistance of bacterial pathogens. However, the knowledge of the abundance and distribution of antibiotic resistance genes (ARGs) influenced by antibiotic pollution is still limited. Methods: In this work, the contamination by resistance genes of the environmental media including an urban river and soil along the river located near the sewage outlet of a veterinary antibiotic manufacturing site in Shijiazhuang, China, was assessed. The abundance and dynamic distribution of ARGs in different sampling points and during different seasons were analyzed using fluorescent quantitative PCR method (qPCR). Results: A total of 11 resistance genes, one integron and one transposon were detected in water and soils around the pharmaceutical factory, and among which, the sulfonamide resistance genes sul1 and β-lactam resistance genes blaSHV were the most abundant genes. The relative abundance of ARGs in both river water and soil samples collected at the downstream of the sewage outlet was higher than that of samples collected at the upstream, non-polluted areas (p < 0.05). The mobile genetic elements (MGEs) integron in river was significantly correlated (p < 0.05) with the relative abundance of ARGs. Conclusions: The results indicate that the discharge of waste from antibiotic manufacturing site may pose a risk of horizontal transfer of ARGs.

Distribution of antibiotic resistance genes in the environment

The prevalence of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the microbiome is a major public health concern globally. Many habitats in the environment are under threat due to excessive use of antibiotics and evolutionary changes occurring in the resistome. ARB and ARGs from farms, cities and hospitals, wastewater treatment plants (WWTPs) or as water runoffs, may accumulate in water, soil, and air. We present a global picture of the resistome by examining ARG-related papers retrieved from PubMed and published in the last 30 years (1990-2020). Natural Language Processing (NLP) was used to retrieve 496,640 papers, out of which 9374 passed the filtering test and were further analyzed to determine the distribution and diversity of ARG subtypes. The papers revealed seven major antibiotic families together with their respective ARG subtypes in different habitats on six continents. Asia, especially China, had the highest number of ARGs related papers compared to other countries/regions/continents. ARGs belonging to multidrug, glycopeptide, and β-lactam families were the most common in reports from hospitals and sulfonamide and tetracycline families were common in reports from farms, WWTPs, water and soil. We also highlight the 'omics' tools used in resistome research, describe some factors that shape the development of resistome, and suggest future work needed to better understand the resistome. The goal was to show the global nature of ARB and ARGs in order to encourage collaborate research efforts aimed at reducing the negative impacts of antibiotic resistance on the One Health concept.

Profiles of antibiotic resistance genes in an inland salt-lake Ebinur Lake, Xinjiang, China: The relationship with antibiotics, environmental factors, and microbial communities

Lakes in arid northwestern China, as the main pollutant-holding water bodies in the typical ecologically fragile areas, are facing the unknown risk of exposure to antibiotics and antibiotic resistance genes (ARGs). In this study, five ARGs and one mobile genetic element (intI1) and their relation with antibiotics, microbial communities and water quality were investigated in Ebinur Lake Basin, a typical salt-lake of China. Quantitative PCR analysis indicated that ARGs decreasing order in both surface water and sediment was sul1 >sul2 >tetW>ermB>qnrS, which means sulfonamide resistance genes were the main pollution ARGs. Macrolide antibiotics were the predominant antibiotics in the surface water and sediment in winter, while sulfonamides and quinolones accounted for a high proportion in summer. There was a non-corresponding relationship between ARGs and antibiotics. Moreover, the relationship between ARGs and microbial communities were defined. Sulfonamide resistance genes were carried by a greater diversity of potential host bacteria (76 genera) than other ARGs (9 genera). And their positive correlation with intI1 (p < 0.05) which promotes their migration and provides possibility of their co-occurrence in bacterial populations (e.g., Nitrospira). Bacterial genera were the main driver of ARGs distribution pattern in highly saline lake sediment. Environmental factors like salinity, total nitrogen and organic matter could have a certain influence on the occurrence of ARGs by affecting microorganisms. The results systematically show the distribution and propagation characteristics of ARGs in typical inland salt-lakes in China, and preliminarily explored the relationship between ARGs and antibiotics, resistance genes and microorganisms in lakes in ecologically fragile areas.

The fate of tetracycline in vegetated mesocosmic wetlands and its impact on the water quality and epiphytic microbes

The fate of antibiotics and their impact on antibiotic resistance genes (ARGs) and microbial communities are far from clear in wetlands. The fate and impact of tetracycline (TC) on the nutrient degradation of wetlands and epiphytic microbes were investigated. This study showed that after TC spiking, 99.7% of TC were removed from the surface water of wetlands containing Vallisneria spiralis within 4 days post-treatment. TC spiking impaired the nutrient removal capacity and disrupted epiphytic microbial community structure while enhancing the abundance of 11 ARGs subtypes, including tetracycline resistance genes, tetX, tetM, tetO, tetQ, tetS, and tet36. TC decreased bacterial biodiversity but amplified the relative abundance of Proteobacteria and Firmicutes by 4% and 61%, respectively, and increased eukaryotic diversity. 16 metabolic pathways including Carbohydrate, Energy, Amino acid, 'cofactor and vitamins' metabolisms were significantly (p < 0.01) increased in TC treatment. Phylogenetic, functional prediction analysis indicated that Flavobacterium was positively related with xenobiotics, cell motility, 'terpenoids and polyketides' metabolism but negatively related to nucleotide metabolism, while Rhodobacter showed a reverse trend but positively related with nucleotide and 'glycan biosynthesis' and metabolism. These data highlighted that TC has negative impacts on epiphytic microbial community and nutrients removal in wetlands.

Agricultural land-use change exacerbates the dissemination of antibiotic resistance genes via surface runoffs in Lake Tai Basin, China

Agricultural runoff is an important antibiotic resistance genes (ARGs) dissemination pathway from farmlands to water environment, however few studies have focused on the influence of agricultural land-use change on the pattern of ARGs in runoff and assess the health risk to public. Lake Tai Basin which experiences agricultural land-use change was selected to elucidate this concern. Our findings revealed that the pattern of ARGs was more diverse and the gene abundance was higher in orchard runoffs by comparison with conventional cropland runoffs. Co-occurrence network analysis between mobile genetic elements and ARGs demonstrated that after agricultural land-use change, ARG dissemination via runoffs became more threatened. In addition, this study illustrated the correlations between the antibiotic resistome and microbiome in runoffs, finding that non-dominant microbial taxa were the limiting factor which determined the pattern of ARGs in surface runoffs. In summary, the pattern and dissemination risk of ARGs in the surface runoff after agricultural land-use change in Lake Tai Basin were clarified via this study.

The variation of antibiotic resistance genes and their links with microbial communities during full-scale food waste leachate biotreatment processes

The prevalence of antibiotic resistance genes (ARGs) has been widely reported in various environments. However, little is known of them in food waste (FW) leachate with high organic content and how their distribution is influenced by biotreatment processes. Here, twelve ARGs, two integrase genes and bacterial communities were investigated during two full-scale FW biotreatment processes. High ARGs abundances (absolute: 1.03 × 10⁷-2.82 × 10⁹copies/mL; relative: 0.076-2.778copies/16S rRNA) were observed across all samples. Although biotreatment effectively reduced absolute abundance of ARGs, additional bacteria acquiring ARGs caused an increase in their relative abundance, which further increased the transmission risk of ARGs. mexF, blaCTX-M, sul1 played crucial roles and sul1 might be considered as an indicator for the prediction of total ARGs. It is worrying that the discharge (effluent and sludge) included highly abundant ARGs (5.09 × 10¹⁴-4.83 × 10¹⁵copies/d), integrons (1.11 × 10¹⁴-6.04 × 10¹⁴copies/d) and potential pathogens (such as Pseudomonas and Streptococcus), which should be given more attentions. blaCTX-M and tetQ possessed most potential hosts, Proteobacteria-L and Firmicutes-W were predominant contributors of ARGs-hosts at genus level. This study suggested FW leachate biotreatment systems could be reservoirs of ARGs and facilitated the proliferation of them. The exploration of effective removal methods and formulation of emission standard are necessary for future ARGs mitigation.

Microplastic particles in the aquatic environment: A systematic review

Microplastics (MPs) pollution has become one of the most severe environmental concerns today. MPs persist in the environment and cause adverse effects in organisms. This review aims to present a state-of-the-art overview of MPs in the aquatic environment. Personal care products, synthetic clothing, air-blasting facilities and drilling fluids from gas-oil industries, raw plastic powders from plastic manufacturing industries, waste plastic products and wastewater treatment plants act as the major sources of MPs. For MPs analysis, pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), Py-MS methods, Raman spectroscopy, and FT-IR spectroscopy are regarded as the most promising methods for MPs identification and quantification. Due to the large surface area to volume ratio, crystallinity, hydrophobicity and functional groups, MPs can interact with various contaminants such as heavy metals, antibiotics and persistent organic contaminants. Among different physical and biological treatment technologies, the MPs removal performance decreases as membrane bioreactor (> 99%) > activated sludge process (~98%) > rapid sand filtration (~97.1%) > dissolved air floatation (~95%) > electrocoagulation (> 90%) > constructed wetlands (88%). Chemical treatment methods such as coagulation, magnetic separations, Fenton, photo-Fenton and photocatalytic degradation also show moderate to high efficiency of MP removal. Hybrid treatment technologies show the highest removal efficacies of MPs. Finally, future research directions for MPs are elaborated.

Agricultural land-use change and rotation system exert considerable influences on the soil antibiotic resistome in Lake Tai Basin

In this study, we use high-throughput quantitative polymerase chain reaction approaches to comprehensively assess the effects of agricultural land-use change on the antibiotic resistome of agricultural runoffs after rainfalls in Lake Tai Basin. For the first time in this region, our findings show that orchard runoffs harbored more diverse and abundant antibiotic resistance genes (ARGs) than traditional cropland runoffs. Network analysis demonstrated that orchard runoffs possessed a strong ability for ARG dissemination via horizontal gene transfer. These results suggest that residents might be exposed to a higher public health threat than before. Moreover, the present study confirmed that the rice-wheat rotation system plays a key role in regulating the soil antibiotic resistome profile. Using 16S rRNA high-throughput sequencing technology, this study clarified the relationships between the antibiotic resistome and soil microbiome composition. Finally, we discuss the key environmental factors driving changes in the soil antibiotic resistome. In summary, this study gives insight into the dissemination of environmental ARGs to the people living in the Lake Tai Basin.

Mobile genetic elements are the Major driver of High antibiotic resistance genes abundance in the Upper reaches of huaihe River Basin

Rivers are considered a vital reservoir of antibiotic resistance genes (ARGs) and are critical to disseminate ARGs. The present study delved into the ARGs pollution of the sediments in the upper reaches of Huaihe river, one of the seven longest rivers in China, by high-throughput quantitative PCR. Subsequently, the relationship between ARGs and the bacterial community/mobile genetic elements (MGEs) was determined. As revealed from the results, the overall ARGs ranged from 2.65×10^-3 to 6.14×10^-2/16S copies, and the abundance of ARGs in the tributaries was significantly higher than that in the mainstreams (p<0.05). Moreover, the ARGs introduced by tributaries were capable of affecting the whole mainstream of Huaihe river. As suggested from the results of co-occurrence analysis and pRDA analysis, MGEs were reported as the major driver to disseminate ARGs in the upper reaches of Huaihe river basin. The larger the MGEs proportion, the higher the likelihood of ARGs transferring from antibiotic resistance bacteria to human pathogens in Huaihe river.

Occurrence of antibiotics and antibiotic resistance genes in the Fuxian Lake and antibiotic source analysis based on principal component analysis-multiple linear regression model

In recent years, the dramatic increase in antibiotic use has led to the evolution of antibiotic resistant genes (ARGs), posing a potential risk to human and aquatic ecological safety. In this study, source contribution and correlations between twelve antibiotics and their corresponding ARGs were firstly investigated in surface water in the Fuxian Lake. The results showed that sulfamethoxazole (SMX) (0.98-14.32 ng L^-1) and ofloxacin (OFL) (0.77-7.3 ng L^-1) were the dominant antibiotics in surface water, whereas erythromycin-H₂O (EM-H₂O), SMX and OFL posed the medium risk to aquatic organisms. Meanwhile, the mean concentrations of MLs in inflowing rivers were 5.6 times more than those in the lake, which was related to dilution and degradation. Moreover, the facter1 (co-sources L (Living quarters), M (Mining area), A (Agricultural district) and T (tourist area)) contributed 78% of antibiotic concentrations, and the source L was predominant. The results also revealed the prevalence of intL1, sul1 and sul2 in all the sampling sites, and that the abundance of ARGs in the lake was significantly lower (P < 0.01) than that in inflowing rives. Additionally, significant correlations (p < 0.0001) between intL1 and sulfanilamide resistance genes (sul1, sul2) were detected, indicating that intL1 promoted the propagation and they originated from the same anthropogenic sources. Overall, our findings revealed the presence of antibiotics and ARGs and their inconsistent correlations in the Fuxian Lake, which provides a foundation to support further exploration of the occurrence and transmission mechanisms of antibiotics and ARGs.

Occurrence of antibiotic resistance genes and microbial source tracking markers in the water of a karst spring in Germany

The emergence of antimicrobial resistances causes serious public health concerns worldwide. In recent years, the aquatic ecosystem has been recognized as a reservoir for antibiotic-resistant bacteria and antibiotic resistance genes (ARGs). The prevalence of 11 ARGs, active against six antibiotic classes (β-lactams, aminoglycosides, tetracycline, macrolides, trimethoprim, and sulfonamides), was evaluated at a karst spring (Gallusquelle) in Germany, using molecular biological methods. In addition, fecal indicator bacteria (FIB), turbidity, electrical conductivity, spring discharge, and microbial source tracking markers specific for human, horse, chicken, and cow were determined. The ARGs most frequently detected were ermB (42.1%), tet(C) (40.8%), sul2 (39.5%), and sul1 (36.8%), which code for resistance to macrolides, tetracycline and sulfonamides, respectively. After a heavy rain event, the increase in FIB in the spring water was associated with the increase in ARGs and human-specific microbial source tracking (MST) markers. The determined correlations of the microbiological parameters, the observed overflow of a combined sewer overflow basin a few days before the increase of these parameters, and the findings of previous studies indicate that the overflow of this undersized basin located 9 km away from the spring could be a factor affecting the water quality of the karst spring. Our results provide a scientific basis for minimization of the input of fecal pollution and thus ARGs into the karst spring.

Critical roles of cyanobacteria as reservoir and source for antibiotic resistance genes

The widespread occurrence of antibiotic resistance genes (ARGs) throughout aquatic environments has raised global concerns for public health, but understanding of the emergence and propagation of ARGs in diverse environmental media remains limited. This study investigated the occurrence and spatio-temporal patterns of six classes of ARGs in cyanobacteria isolated from Taihu Lake. Tetracycline and sulfonamide resistance genes were identified as dominant ARGs. The abundance of ARGs in cyanobacteria was significantly higher in the bloom period than in the non-bloom period. The contribution and persistence of ARGs were higher in extracellular DNA (eDNA) than in intracellular DNA (iDNA) from cyanobacteria. Cyanobacteria-associated eDNA carrying ARGs was more stable at lower temperature. The relative abundances of ARGs in Microcystis and Synechococcus, the dominant genera of cyanobacterial blooms in Taihu Lake, were significantly higher than those in other cyanobacterial strains. The conjugative transfer efficiency for bacterial assimilation of ARGs in cyanobacteria was facilitated by increasing temperature and cyanobacterial cell concentration. Our results demonstrated that cyanobacteria could act as a significant reservoir and source for the acquisition and dissemination of ARGs in aquatic environments, hence the definition of negative ecological effects of cyanobacterial blooms was expanded.