Profiles of ARGs and their relationships with antibiotics, metals and environmental parameters in vertical sediment layers of three lakes in China

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

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

Effects of cadmium exposure on gut microbiota and antibiotic resistance genes in Haliotis diversicolor abalone

Heavy metals in soil, water, and industrial production can affect the antibiotic resistance of bacteria. Antibiotic resistance in gut microbiota has been extensively researched. The effects of cadmium (Cd) was investigated on the gut microbiota and antibiotic resistance genes (ARGs) of Haliotis diversicolor, a commercially important abalone species. By exposing H. diversicolor to four concentrations of Cd (0 μg L-1 (control), 6.5 μg L-1 (low), 42.25 μg L-1 (medium), and 274.63 μg L-1 (high)) for 30 and 60 days, 16 types of ARG (aadA-01, aadA-02, cfr, dfrA1, ermB, floR, folA, mecA, sul2, tetB-01, tetC-01, tetD-01, tetG-01, tetM-02, tetQ, vanC-01), and 1213 genus and 27 phylum microbiomes were detected. ARGs can be resistant to aminoglycoside, beta-lactamase, macrolide-lincosamide-streptogramin B, multidrug, florfenicol, macrolide, sulfonamides, tetracyclines, and vancomycin. Cadmium exposure significantly alters the abundance of tetC-01, tetB-01, tetQ, sul2, and aadA-01. About 5% (61) of genus-level microorganisms were significantly affected by Cd exposure. Microbiota alpha and beta diversities in the 60-day 42.25 μg L-1 Cd treatment differed significantly from those in other treatments. In addition, 26 pathogens were detected, and two pathogens (Vibrio and Legionella) were significantly affected by Cd exposure. Significant correlations between pathogens and ARGs increased with increased Cd concentration after 60 days of Cd exposure. Cadmium exposure may cause gut microbiota disturbance in H. diversicolor and increase the likelihood of ARG transfer to pathogens, increasing potential ecological and economic risks.

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.

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.

Spatial variability, source identification and risks assessment of antibiotics in multimedia of North China's largest freshwater lake using positive matrix factorization and Monte Carlo simulation

Antibiotics are widely found in aquatic ecosystems and pose a serious threat to human and the ecological system. Samples of surface water (SW), overlying water (OW), pore water (PW) and sediments (Sedi) were collected to investigate the spatial variability, potential sources, ecological risk (RQs) and health risks (HQs) of nine common antibiotics in Baiyangdian Lake using positive matrix factorization (PMF), and Monte Carlo simulation. Significant spatial autocorrelation of most antibiotics were observed in PW and Sedi samples rather than in SW and OW samples, and higher antibiotic levels were found in the northwest of waters and the southwest of sediments. Livestock (26.74-35.57%) and aquaculture (21.62-37.70%) were identified as primary sources of antibiotics in the water and sediments. Norfloxacin and roxithromycin showed high levels of RQ and HQ in more than 50% of samples, respectively. The combined RQ (ΣRQ) in the PW can be used as a sign of across multimedia risk. Notably, appreciable health risks were observed for the combined HQ (ΣHQ) in about 80% of samples, indicating the importance of taking health risk of antibiotics into consideration. The findings of this work provides a reference for antibiotics pollution control and risk management in shallow lake.

Unexpected enrichment of antibiotic resistance genes and organic remediation genes in high-altitude lakes at Eastern Tibetan Plateau

Elevation has a strong effect on aquatic microbiome. However, we know little about the effects of elevation on functional genes, especially antibiotic resistance genes (ARGs) and organic remediation genes (ORGs) in freshwater ecosystems. In this study, we analyzed five classes of functional genes including ARGs, metal resistance genes (MRGs), ORGs, bacteriophages, and virulence genes between two high-altitude lakes (HALs) and two low-altitude lakes (LALs) in Mountain Siguniang at Eastern Tibetan Plateau by means of GeoChip 5.0. No differences (Student's t-test, p > 0.05) of gene richness including ARGs, MRGs, ORGs, bacteriophages, and virulence genes in HALs and LALs were found. The abundance of most ARGs and ORGs was higher in HALs than in LALs. For MRGs, the abundance of macro metal resistance genes of potassium, calcium, and aluminum was higher in HALs than in LALs (Student's t-test, p < 0.05; all Cohen's d > 0.8). The abundance of some heavy metal resistance genes of lead and mercury was lower in HALs than in LALs (Student's t-test, p < 0.05; all Cohen's d < -0.8). The composition of these functional genes in HALs differed significantly from in LALs. The functional gene network in HALs was also more complex than that in LALs. We speculate that enrichment of ARGs and ORGs in HALs is related to different microbial communities, exogenous ARGs, and enriched persistent organic pollutants through long-range atmospheric transport driven by the Indian monsoon. This study highlights the unexpected enrichment of ARGs, MRGs, and ORGs in remote lakes at high elevations.

Inhomogeneous antibiotic distribution in sediment profiles in anthropogenically impacted lakes: Source apportionment, fate drivers, and risk assessment

Antibiotic residues in lake ecosystems have been widely reported; however, the vertical distribution of antibiotics in lake sediment profiles have rarely been examined. This study systematically revealed the vertical distribution pattern, sources, and risks of antibiotics in sediments of four typical agricultural lakes in central China. Nine of 33 target antibiotics were detected with a total concentration range of 39.3-18,250.6 ng/g (dry weight), and the order of average concentration was erythromycin (1447.4 ng/g) > sulfamethoxazole (443.7 ng/g) > oxytetracycline (62.6 ng/g) > enrofloxacin (40.7 ng/g) > others (0.1-2.1 ng/g). The middle-layer sediments (9-27 cm) had significantly higher antibiotic detected number and concentration than those in the top layer (0-9 cm) and bottom layer (27-45 cm) (p < 0.05). Correlation analysis showed that significant relationships existed between antibiotic concentrations and the octanol-water partition coefficients (K_ow) of antibiotics (p < 0.05). Redundancy analysis indicated that Pb, Co, Ni, water content, and organic matter (p < 0.05) jointly affected the distribution of antibiotics in sediment profiles. Risk assessment showed that the highest potential ecological and resistance selection risks of antibiotics occurred in the middle-layer sediments, and oxytetracycline, tetracycline, and enrofloxacin had the most extensive potential risks in the sediment profiles. Additionally, the positive matrix factorization model revealed that human medical wastewater (54.5%) contributed more antibiotic pollution than animal excreta (45.5%) in sediment. This work highlights the inhomogeneous distribution of antibiotics in sediment profiles and provides valuable information for the prevention and control of antibiotic contamination in lakes.

The Use of Antibiotics and Antimicrobial Resistance in Veterinary Medicine, a Complex Phenomenon: A Narrative Review

As warned by Sir Alexander Fleming in his Nobel Prize address: “the use of antimicrobials can, and will, lead to resistance”. Antimicrobial resistance (AMR) has recently increased due to the overuse and misuse of antibiotics, and their use in animals (food-producing and companion) has also resulted in the selection and transmission of resistant bacteria. The epidemiology of resistance is complex, and factors other than the overall quantity of antibiotics consumed may influence it. Nowadays, AMR has a serious impact on society, both economically and in terms of healthcare. This narrative review aimed to provide a scenario of the state of the AMR phenomenon in veterinary medicine related to the use of antibiotics in different animal species; the impact that it can have on animals, as well as humans and the environment, was considered. Providing some particular instances, the authors tried to explain the vastness of the phenomenon of AMR in veterinary medicine due to many and diverse aspects that cannot always be controlled. The veterinarian is the main reference point here and has a high responsibility towards the human–animal–environment triad. Sharing such a burden with human medicine and cooperating together for the same purpose (fighting and containing AMR) represents an effective example of the application of the One Health approach.

Antibiotic Resistance Genes in Interconnected Surface Waters as Affected by Agricultural Activities

Pastures have become one of the most important sources of antibiotic resistance genes (ARGs) pollution, bringing risks to human health through the environment and the food that is grown there. Another significant source of food production is greenhouse horticulture, which is typically located near pastures. Through waterways, pasture-originated ARGs may transfer to the food in greenhouses. However, how these pasture-originated ARGs spread to nearby waterways and greenhouses has been much less investigated, while this may pose risks to humans through agricultural products. We analyzed 29 ARGs related to the most used antibiotics in livestock in the Netherlands at 16 locations in an agricultural area, representing pastures, greenhouses and lakes. We found that ARGs were prevalent in all surface waters surrounding pastures and greenhouses and showed a similar composition, with sulfonamide ARGs being dominant. This indicates that both pastures and greenhouses cause antibiotic resistance pressures on neighboring waters. However, lower pressures were found in relatively larger and isolated lakes, suggesting that a larger water body or a non-agricultural green buffer zone could help reducing ARG impacts from agricultural areas. We also observed a positive relationship between the concentrations of the class 1 integron (intl1 gene)-used as a proxy for horizontal gene transfer-and ARG concentration and composition. This supports that horizontal gene transfer might play a role in dispersing ARGs through landscapes. In contrast, none of the measured four abiotic factors (phosphate, nitrate, pH and dissolved oxygen) showed any impact on ARG concentrations. ARGs from different classes co-occurred, suggesting simultaneous use of different antibiotics. Our findings help to understand the spatial patterns of ARGs, specifically the impacts of ARGs from pastures and greenhouses on each other and on nearby waterways. In this way, this study guides management aiming at reducing ARGs' risk to human health from agricultural products.

Occurrence, bioaccumulation and ecological risks of antibiotics in the water-plant-sediment systems in different functional areas of the largest shallow lake in North China: Impacts of river input and historical agricultural activities

Antibiotics are widely used and ubiquitous in the environment, which in turn poses potential threat to human health. However, the effects of agricultural activities and river input on the fate and ecological risks of antibiotics in shallow lake are still poorly understood. Surface water, overlying water and pore water, sediments and aquatic plant samples in the historical planting subarea (PA), historical aquaculture subarea (AU), inflow subarea (IW), discharge subarea (DC), and conservation subarea (CK) of Baiyangdian Lake were collected and analyzed. Our results revealed that the total antibiotic concentrations ranged from 85.33 ng/L to 1631.47 ng/L in waters and from 66.90 ng/g to 177.03 ng/g in sediments. Generally, the total antibiotic concentrations introduced by planting activity in surface water, overlying water and sediments were higher and the levels of total antibiotics in pore water were more affected by river input. In addition, three quinolones (QNs) and two tetracyclines (TCs) were dominant antibiotics in almost five subareas. The pseudo-partitioning coefficient k_d(pw) and bioaccumulation factor (BAF) of antibiotics varied according to the effects of river input and historical agricultural activities. The ecological risk (RQ) of antibiotics from agricultural activities was higher than that from river input. The norfloxacin (NOR) in pore water showed high RQ, which contributed to a large proportion (>50 %) of the combined ecological risks (∑RQs) except for surface water. Therefore, NOR should be used as the primary ecological risk control index for antibiotic contamination management in the BYD. ∑RQs showed high risk in water in the five subareas. This study can act as a reference for governments to formulate effective management strategies for protecting the ecological health of lakes.

Structure, mechanism, and toxicity in antibiotics metal complexation: Recent advances and perspectives

Antibiotic-metal complexes (AMCs) formed by antibiotics and metal ions have attracted considerable attentions in recent years. Although different removal methods for AMCs have been reported in the literature, very few investigations have focused on the mechanisms and toxic effects of antibiotic-metal coordination. This review briefly describes the structural characteristics of various commonly used antibiotics and the coordination mechanisms with metal ions. Considering the complexity of the real environment, various environmental factors affecting AMC formation are highlighted. The effects of AMCs on microbial community structure and the role of metal ions in influencing resistant genes from the molecular perspective are of interest within this work. The toxicities and mechanisms of AMCs on different species of biota are also discussed. These findings underline the need for more targeted detection and analysis methods and more suitable toxicity markers to verify the combination of antibiotics with metal ions and reveal environmental toxicities in future. This review presents an innovative idea that antibiotics combined with metal ions will change the toxicity and environmental behavior of antibiotics.

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.

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.

Accelerated spread of antibiotic resistance genes (ARGs) induced by non-antibiotic conditions: Roles and mechanisms

The global spread of antibiotic resistance genes (ARGs) has wreaked havoc with the treatment efficiency of antibiotics and, ultimately, anti-microbial chemotherapy, and has been conventionally attributed to the abuse and misuse of antibiotics. However, the ancient ARGs have alterative functions in bacterial physiology and thus they could be co-regulated by non-antibiotic conditions. Recent research has demonstrated that many non-antibiotic chemicals such as microplastics, metallic nanoparticles and non-antibiotic drugs, as well as some non-antibiotic conditions, can accelerate the dissemination of ARGs. These results suggested that the role of antibiotics might have been previously overestimated whereas the effects of non-antibiotic conditions were possibly ignored. Thus, in an attempt to fully understand the fate and behavior of ARGs in the eco-system, it is urgent to critically highlight the role and mechanisms of non-antibiotic chemicals and related environmental factors in the spread of ARGs. To this end, this timely review assessed the evolution of ARGs, especially its function alteration, summarized the non-antibiotic chemicals promoting the spread of ARGs, evaluated the non-antibiotic conditions related to ARG dissemination and analyzed the molecular mechanisms related to spread of ARGs induced by the non-antibiotic factors. Finally, this review then provided several critical perspectives for future research.

Fate and ecological risks of antibiotics in water-sediment systems with cultivated and wild Phragmites australis in a typical Chinese shallow lake

River carrying antibiotics from upstream posed serious threats to receiving lake, and plants might had effects on antibiotics. Therefore, samples of waters, sediments and tissues of cultivated and wild Phragmites australis were collected to analyse antibiotics fate and ecological risks (RQs) in Zaozhadian Lake. Our results revealed that the total antibiotics showed an increasing tendency in surface/pore water and P. australis tissues and a decreasing tendency in overlying water and sediments from the lake entrance to the centre. The bioaccumulation factors (BAFs) of two sulfonamides (SAs) and three quinolones (QNs) increased in sediments and decreased in those of erythromycin in pore water from Site 1 to Site 11. Three QNs and two tetracyclines (TCs) were dominant antibiotics in pore water/sediment and surface/overlying water respectively. Higher levels of two SAs in surface/pore water and two macrolides (MAs) in overlying/pore water and sediments were observed in the wild P. australis region, while higher values of two TCs in overlying/pore water and three QNs in sediment were observed in the cultivated P. australis region. Higher BAFs of SAs and QNs in sediments were observed in the cultivated and wild P. australis region respectively. The RQs of oxytetracycline and two MAs posed moderate risks in surface/overlying water from more than 50% of sampling sites. Norfloxacin exhibited moderate RQ and low ∑RQ levels in sediments, and showed high risk in pore water. Our findings imply that much more attention should be given to the antibiotics from river inputs and management normatives to control antibiotic pollution.

Tracking the influence of antibiotics, antibiotic resistomes, and salinity gradient in modulating microbial community assemblage of surface water and the ecological consequences

The ecological impacts of antibiotics and antibiotic resistance genes (ARGs) on water ecology remain elusive in natural environments. We investigated the influence of antibiotics, ARGs and salinity gradient on the surface water ecosystem. Cefquinome (104.2 ± 43.6 ng/L) and cefminox (16.2 ± 7.50 ng/L) cephalosporins were predominant in all sites. Antibiotic contamination was increased in the estuary ecosystems compared to the freshwater ecosystems by 6%. Bacterial diversity could resist changes in salinity, but the relative abundance of some bacterial genera; Pseudoalteromonas, Glaciecola, norank_f__Arcobacteraceae, and Pseudohongiella was increased in the estuary zone (salinity>0.2%). The eukaryotic composition was increased in the subsaline environments (<0.2%), but the higher salinity in the saline zone inhibited the eukaryotic diversity. The relative abundance of ARGs was significantly higher in the estuary than in freshwater ecosystems, and ARGs interactions and mobile elements (aac(6')-Ib(aka_aacA4)-01, tetR-02, aacC, intI1, intI-1(clinic), qacEdelta1-01, and strB) were the predominant factors responsible for the ARGs propagation. Antibiotics associated with corresponding and non-corresponding ARGs and potentially created an adverse environment that increased the predation and pathogenicity of the aquatic food web and inhibited the metabolic functions. Surface water are first-line-ecosystems receiving antibiotics and ARGs hence our findings provided vital insights into understanding their ecological consequences on surface water ecosystems.

Receptor model-oriented sources and risks evaluation of metals in sediments of an industrial affected riverine system in Bangladesh

Toxic metals in river sediments may represent significant ecological concerns, although there has been limited research on the source-oriented ecological hazards of metals in sediments. Surface sediments from an industrial affected Rupsa River were utilized in this study to conduct a complete investigation of toxic metals with source-specific ecological risk assessment. The findings indicated that the average concentration of Ni, Cr, Cd, Zn, As, Cu, Mn and Pb were 50.60 ± 10.97, 53.41 ± 7.76, 3.25 ± 1.73, 147.76 ± 36.78, 6.41 ± 1.85, 59.78 ± 17.77, 832.43 ± 71.56 and 25.64 ± 7.98 mg/kg, respectively and Cd, Ni, Cu, Pb and Zn concentration were higher than average shale value. Based on sediment quality guidelines, the mean effective range median (ERM) quotient (1.29) and Mean probable effect level (PEL) quotient (2.18) showed medium-high contamination in sediment. Ecological indexes like toxic risk index (20.73), Nemerow integrated risk index (427.59) and potential ecological risk index (610.66) posed very high sediment pollution. The absolute principle component score-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) model indicated that Zn (64.21%), Cd (51.58%), Cu (67.32%) and Ni (58.49%) in APCS-MLR model whereas Zn (49.5%), Cd (52.7%), Cu (57.4%) and Ni (44.6%) in PMF model were derived from traffic emission, agricultural activities, industrial source and mixed sources. PMF model-based Nemerow integrated risk index (NIRI) reported that industrial emission posed considerable and high risks for 87.27% and 12.72% of sediment samples. This work will provide a model-based guidelines for identifying and assessing metal sources which would be suitable for mitigating future pollution hazards in Riverine sediments in Bangladesh.

The combined effect of an integrated reclaimed water system on the reduction of antibiotic resistome

The reuse of urban reclaimed water is conducive to alleviate the current serious shortage of water resources. However, antibiotic resistance genes (ARGs) in reclaimed water have received widespread attention due to their potential risks to public health. Deciphering the fate of ARGs in reclaimed water benefits the development of effective strategies to control resistome risk and guarantees the safety of water supply of reclaimed systems. In this study, the characteristics of ARGs in an integrated reclaimed water system (sewage treatment plant-constructed wetland, STP-CW) in Beijing (China) have been identified using metagenomic assembly-based analysis, as well as the combined effect of the STP-CW system on the reduction of antibiotic resistome. Results showed a total of 29 ARG types and 813 subtypes were found in the reclaimed water system. As expected, the STP-CW system improved the removal of ARGs, and about 58% of ARG subtypes were removed from the effluent of the integrated STP-CW system, which exceeded 43% for the STP system and 37% for the CW system. Although the STP-CW system had a great removal on ARGs, abundant and diverse ARGs were still found in the downstream river. Importantly, network analysis revealed the co-occurrence of ARGs, mobile genetic elements and virulence factors in the downstream water, implying potential resistome dissemination risk in the environment. Source identification with SourceTracker showed the STP-effluent was the largest contributor of ARGs in the downstream river, with a contribution of 45%. Overall, the integrated STP-CW system presented a combined effect on the reduction of antibiotic resistome, however, the resistome dissemination risk was still non-negligible in the downstream reclaimed water. This study provides a comprehensive analysis on the fate of ARGs in the STP-CW-river system, which would benefit the development of effective strategies to control resistome risk for the reuse of reclaimed water.

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.

Hormetic dose-response of halogenated organic pollutants on Microcystis aeruginosa: Joint toxic action and mechanism

Quinolones (QNs), dechloranes (DECs), and chlorinated paraffins (CPs) are three kinds of new halogenated organic pollutants (HOPs), which originate from the use of flame retardants, lubricants and pesticides. Since QNs, DECs, and CPs are frequently detected in waters and sediments, it is necessary to investigate the toxic effects of these HOPs with dwelling phytoplankton, especially for cyanobacteria, to explore their potential hormetic effects and contributions to algal blooms. In the present study, we investigate single and joint toxicity of QNs, DECs and CPs on Microcystis aeruginosa (M. aeruginosa), a cyanobacterium that is frequently implicated with algal blooms. The results indicate single QNs and DECs induce marked hormetic effects on the proliferation of M. aeruginosa but CPs do not. The stimulatory effect of hormesis is linked with accelerated replication of DNA, which is considered to stem from the moderate rise in intracellular reactive oxygen species (ROS). Joint toxicity tests reveal that both QNs & CPs mixtures and DECs & CPs mixtures show hormetic effects on M. aeruginosa, but QNs & DECs mixtures show no hormetic effect. QNs & DECs mixtures exhibit synergistic toxic actions, which may be caused by a sharp rise in intracellular ROS simultaneously produced by the agents. Joint toxic actions of both QNs & CPs, and DECs & CPs shift from addition to antagonism as concentration increases, and this shift may mainly depend on the influence of CPs on cell membrane hydrophobicity of M. aeruginosa. This study provides data and toxic mechanisms for the hormetic phenomenon of single and joint HOPs on M. aeruginosa. The hormetic effects of HOPs may benefit the proliferation of M. aeruginosa in the aquatic environment, aggravating the formation of algal blooms. This study also reflects the important role of hormesis in environmental risk assessment of pollutants.

The prevalence and removal of antibiotic resistance genes in full-scale wastewater treatment plants: Bacterial host, influencing factors and correlation with nitrogen metabolic pathway

This study investigated the prevalence of antibiotic resistance genes (ARGs) in the influent, effluent, and waste activated sludge (WAS) of eight full-scale municipal wastewater treatment plants (WWTPs) in Shanghai, China. A comprehensive understanding of the correlation between various influencing factors (characteristics of wastewater and WAS, antibiotics, metals, mobile genetic elements) and ARGs was explored. Among the eight full-scale WWTPs, the Unitank process was inefficient in removing typical ARGs compared with continuous-flow anaerobic-anoxic-aerobic and oxidation ditch processes. Antibiotic was identified as the most influential factor affecting the occurrence of ARGs in wastewater, followed by flow rate and nutrients. Positive correlations were observed between antibiotics and their corresponding ARGs in the influent, while this correlation disappeared in the WAS. Class I integron, wastewater characteristics (nitrogen and flow rate), antibiotics (ofloxacin, sulfamethazine, and erythromycin), metals (Mg, Al, Fe, and Mn) were identified as crucial factors comprehensively affecting the distribution of ARGs in WAS. Dissimilatory nitrate reduction profoundly influenced the fate of ARGs during wastewater treatment processes, and K04561 (norB), K02567 (napA), K00262 (gdhA), K00284 (gltS) were identified as the most significant genes in the nitrogen metabolism pathway (ko00910). This study provides a new perspective for comprehensively understanding the occurrence and dissemination of ARGs in WWTPs.

Occurrence and distribution of antibiotic resistant bacteria and genes in the Fuhe urban river and its driving mechanism

Antibiotic resistance genes (ARGs) in urban rivers can affect human health via the food chain and human pathogenic bacteria diffusion. Sediment can be a sink for ARGs, causing second sources of ARG contamination through diffusion. Therefore, we evaluated the effects of total petroleum hydrocarbons (TPHs) and phytoplankton on the distribution of the ARGs in the sediment and water of Fuhe river in Baoding city, China. The ARGs and human pathogenic bacteria in urban river were analyzed, and the phytoplankton and bacterial abundance, TPH, and physicochemical parameters ranked using the partial least squares path modelling (PLS-PM) and aggregated boosted tree (ABT) analysis. The main ARGs in Fuhe river sediment were sulfonamide and tetracycline resistance genes, with sul2 exhibiting the highest level. The main human pathogenic bacteria in the pathogens pool were Clostridium, Bacillus and Burkholderiaceae, with Clostridium demonstrating a positive correlation with SulAfolP01. The PLS-PM analysis confirmed that, among the multiple drivers, water physicochemical factors, TPH, phytoplankton, and heavy metals positively and directly affected the ARG profiles in sediment while sediment heavy metals and bacterial communities did the similar effect. These factors (nutrient factors, heavy metals, and TPH) in water and sediment posed the opposite total effect on ARGs in the sediment, suggesting medium factors should have a conclusive effect on the distribution of ARGs in the sediment. The ABT analysis showed that dissolved oxygen (DO), total nitrogen (TN) and Chlorophyta were the most important factors affecting the ARGs distribution in the water, while TN affected the distribution of the genes in the sediment.

A dataset of distribution of antibiotic occurrence in solid environmental matrices in China

While there is growing global concern about the impact of antibiotic residues on emergence and enhancement bacteria’s resistance, toxicity to natural organisms, and, ultimately, public health, a concise picture of measured environmental concentrations of antibiotic occurrence in multiple environmental matrices, particularly in solid matrices (e.g., sludge, soil, and sediments) is still elusive, especially for China. In this paper, we present an up-to-date dataset of the distribution of antibiotic occurrence in solid environmental matrices in China, derived from 210 peer-reviewed literature published between 2000 and 2020. We extracted geographical sampling locations and measured concentration associated with antibiotic occurrence reported in English and Chinese original publications, and applied quality-control procedures to remove duplicates and ensure accuracy. The dataset contains 6929 records of geo-referenced occurrences for 135 antibiotics distributed over 391 locations distinguished at four levels of scale i.e., provincial, prefectural, county, and township or finer. The geographical dataset provides an updated map of antibiotic occurrence in solid environmental matrices in China and can be used for further environmental health risk assessment.

Measurement(s)	Scientific Publication
Technology Type(s)	digital curation
Factor Type(s)	location • matrices • antibiotics
Sample Characteristic - Environment	solid environmental material
Sample Characteristic - Location	China

Spatial distribution of antibiotic resistance genes of the Zaohe-Weihe Rivers, China: exerting a bottleneck in the hyporheic zone

The hyporheic zone (HZ) is an active biogeochemical region where groundwater and surface water mix and a potential reservoir for antibiotic resistance genes (ARGs). In this paper, the relative abundance and spatial distribution of ARGs in the HZ media were investigated, taking into consideration both the five speciation of six metals and the local characteristics. The samples of surface water, groundwater, and sediment were collected from Zaohe-Weihe Rivers of Xi'an City, which is a representative city with characteristics of the northwest region of China. Of 271 ARGs associated with 9 antibiotics, 228 ARGs were detected, with a total detection rate of 84%. Sulfonamide and aminoglycoside ARGs were the dominant types of ARGs. The top 6 ARGs and mobile genetic elements (MGEs) in terms of abundance were tnpA-04, cepA, sul1, aadA2-03, sul2 and intI1. The results of principal component analysis (PCA) showed that the distribution characteristics of ARGs were not associated with the sampling sites but with the environmental medias. Similarity in the water phases and significant differences in the water and sediment phases were found. The redundancy analysis (RDA) identified the key factors controlling ARG pollution, including dissolved oxygen (DO) in surface water, total nitrogen (TN) in groundwater, and total organic carbon (TOC) in sediment. In terms of the speciation of heavy metals, we further revealed the promotion effect between ARGs and heavy metals, especially the residual fraction of Ni. In terms of horizontal transfer mechanism, ARGs were significantly correlated with tnpA-03 in water phase and tnpA-04 in sediment. In the three media, intI1 and ARGs all show a significant correlation. These findings showed that hyporheic zone exerted a bottleneck effect on the distribution and transfer of ARGs.

Intervention of antimicrobial peptide usage on antimicrobial resistance in aquaculture

Antibiotic resistance genes (ARGs) widely exist in diverse matrices to pose potential risks and attract global attention. This study performed tilapia-cultivation experiment to discuss the intervention of antimicrobial peptide usage on antimicrobial resistance in aquaculture by analyzing 29 target ARGs in water, residue, and fish muscle samples. The sul1 gene was the dominant ARG in most of samples while absolute abundances of total ARGs were in the range of 1.5 × 10²-2.3 × 10⁷ copies/mL in water samples and 2.1 × 10⁸-3.9 × 10⁹ copies/g in the residue and fish muscle samples. Compared with antibiotic treatment, the cecropin treatment could significantly reduce the absolute abundance of ARGs and intI1 in all samples. Proteobacteria were the dominant phylum for most of samples while Aeromonas/Cetobacterium served as the dominant genus for samples with antibiotic/cecropin treatment. Network analysis showed that cecropin treatment could significantly reduce occurrence of multi-drug resistant bacteria and the correlation between genera and ARGs. Results of partial least squares structural equation modeling which was used to discuss the influential factors of ARGs exhibited that antibiotics could increase ARGs, further proving that cecropin peptide could effectively reduce ARGs in aquaculture. This study will provide important information on controlling ARGs in aquaculture in terms of antimicrobial peptide application.

A new insight into the ARG association with antibiotics and non-antibiotic agents-antibiotic resistance and toxicity

Although concerns have been raised about co-selection for antibiotic resistance and various antibiotics and non-antibiotic agents, the data on their association in urban sludge is still limited. In addition, antibiotic contamination can result in not only the toxicity but also the antibiotic resistance. In this study, the first large-scale identification of antibiotics and non-antibiotic agents concern for co-selection of resistance against antibiotics was conducted in urban sludge. Co-occurrence analysis showed that antibiotic resistance genes (ARGs) had no significant correlation with the corresponding antibiotics. Therefore, the results of co-occurrence analysis based on antibiotic concentration and ARG abundance were always ambiguous and difficult to interpret. However, antibiotic resistance was positively correlated with highly toxic compounds such as diclofenac, enrofloxacin and nicotine, suggesting that environmental contaminants might influence antibiotic resistance while exerting toxicity through mechanisms such as changes in microbial community and enzyme activity. The close correlation between class 1 integrase gene (intI1) and diclofenac/enrofloxacin indicated that the co-selection scenario between environmental contaminants and ARGs was likely mediated via intI1. In total, the derived co-occurrence patterns improve our understanding of the co-selection between ARGs, antibiotics and non-antibiotic agents, and also reaffirm the importance of potential role of non-antibiotic agents in the global spread of antibiotic resistance.

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.

Interactions between heavy metals and bacteria in mangroves

Environmental heavy metal pollution has become a serious problem in recent years. Therefore, our study investigated seven heavy metal-contaminated mangroves (Beihai, Fangchenggang, Hainan, Hongkong, Shenzhen, Yunxiao, and Zhanjiang) in southern China, and found that they were particularly polluted with Zn and Pb. These heavy metals were mainly distributed in the surface sediments of the mangroves. Among these seven mangroves, the Shenzhen mangrove was the most polluted site, whereas the Beihai mangrove was the least polluted. Moreover, the bacterial communities in the mangroves were significantly associated with heavy metal contamination. For instance, Fusibacter was significantly correlated with Pb, Zn, Cu, Co, Ni, Cd, and Ag (P < 0.05, R = -0.47). Syntrophorhabdus was also significantly correlated with heavy metals (P < 0.05, R = 0.63). Furthermore, Geo-Chip analyses were conducted to demonstrate the involvement of many functional genes in heavy metal transport, particularly Ni transport. Our results also demonstrated that the heavy metals could be transported by various bacteria. For example, Pseudomonas and Burkholderia were involved in various heavy metal transportation mechanisms, particularly for Ni and Zn, suggesting that these bacteria could be used for heavy metal remediation. Therefore, our study provides insights into the interactions between bacterial communities and heavy metals, which could enable the development of novel mangrove protection strategies.

Ecological impact of antibiotics on bioremediation performance of constructed wetlands: Microbial and plant dynamics, and potential antibiotic resistance genes hotspots

Constructed wetlands (CWs) are nature-based solutions for treating domestic and livestock wastewater which may contain residual antibiotics concentration. Antibiotics may exert selection pressure on wetland's microbes, thereby increasing the global antibiotics resistance problems. This review critically examined the chemodynamics of antibiotics and antibiotics resistance genes (ARGs) in CWs. Antibiotics affected the biogeochemical cycling function of microbial communities in CWs and directly disrupted the removal efficiency of total nitrogen, total phosphorus, and chemical oxygen demand by 22%, 9.3%, and 24%, respectively. Since changes in microbial function and structure are linked to the emergence and propagation of antibiotic resistance, antibiotics could adversely affect microbial diversity in CWs. The cyanobacteria community seemed to be particularly vulnerable, while Proteobacteria could resist and persist in antibiotics contaminated wetlands. Antibiotics triggered excitation responses in plants and increased the root activities and exudates. Microbes, plants, and substrates play crucial roles in antibiotic removal. High removal efficiency was exhibited for triclosan (100%) > enrofloxacin (99.8%) > metronidazole (99%) > tetracycline (98.8%) > chlortetracycline (98.4%) > levofloxacin (96.69%) > sulfamethoxazole (91.9%) by the CWs. This review showed that CWs exhibited high antibiotics removal capacity, but the absolute abundance of ARGs increased, suggesting CWs are potential hotspots for ARGs. Future research should focus on specific bacterial response and impact on microbial interactions.

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.

Comparative study on the bacterial diversity and antibiotic resistance genes of urban landscape waters replenished by reclaimed water and surface water in Xi'an, China

Pathogenic bacteria and antibiotic resistance genes (ARGs) in urban landscape waters may pose a potential threat to human health. However, the investigation of their occurrence in the urban landscape waters replenished by reclaimed water (RW) and surface water (SW) is still insufficient. The water samples collected from six urban landscape waters replenished by RW or SW were used to analyze bacterial diversity using high-throughput sequencing of 16S rRNA gene and to detect 18 ARGs and 2 integron-integrase genes by means of quantitative PCR array. Results indicated that Proteobacteria was the dominant phylum in all six urban landscape waters. The bacterial species richness was lower in urban landscape waters replenished by RW than that by SW. Sulfonamide resistance genes (sulI and sulIII) were the major ARGs in these urban landscape waters. No significant difference in the relative abundance of sulfonamide resistance genes, tetracycline resistance genes, and most of beta-lactam resistance genes was observed between RW-replenished and SW-replenished urban landscape waters. By contrast, the relative abundance of bla_ampC gene and qnrA gene in RW-replenished urban landscape waters was significantly higher than that in SW-replenished urban landscape waters (p < 0.05), which suggested that use of RW may increase the amount of specific ARGs to urban landscape waters. Interestingly, among six urban landscape waters, RW-replenished urban landscape waters had a relatively rich variety of ARGs (12-15 of 18 ARGs) but a low relative abundance of ARGs (458.90-1944.67 copies/16S × 10⁶). The RW replenishment was found to have a certain impact on the bacterial diversity and prevalence of ARGs in urban landscape waters, which provide new insight into the effect of RW replenishment on urban landscape waters.

Occurrence, Distribution, and Ecological Risk Assessment of Antibiotics in Different Environmental Media in Anqing, Anhui Province, China

The widespread usage of antibiotics in human and animal medication has brought global concerns over environmental contamination of antibiotic residues. In this study, 16 kinds of antibiotics in different environmental media of water, sediments, and soils in Anqing city, Anhui province were determined by ultra-performance liquid chromatography tandem mass spectrometry. A total of fourteen kinds of antibiotics were detected in surface water, with a total concentration up to 479 ng·L⁻¹, while six kinds of antibiotics were detected in sediment and soil with concentrations ranging from 15.1 to 108 μg·kg⁻¹. Ciprofloxacin (12.8–99.5 ng·L⁻¹) and tetracycline (17.2–225 μg·kg⁻¹) antibiotics exhibited the highest concentration in water and soil, respectively. In spatial distribution, the total concentration of antibiotics in surface water from the highest to the lowest followed the order of urban area, mainstream of Wan River, suburbs, tributaries of Wan River, indicating that the level of antibiotic concentration in surface water is positively associated with the frequency of human activities. In addition, the antibiotic mass fraction in agriculture land and fishpond were found higher than that in other sampling sites. Moreover, the environmental risk assessment results showed that ciprofloxacin, erythromycin, ofloxacin, enrofloxacin and tetracycline might pose medium to high risks to algae and bacteria in aquatic ecosystem.

Antibiotic resistance genes in surface water and groundwater from mining affected environments

Mining activities are known to generate a large amount of mine tailings and acid mine drainage which contain varieties of heavy metals. Heavy metals play an important role in co-selection for bacterial antibiotic resistance. However, the characteristics of antibiotic resistance genes (ARGs) in mining-affected water environments are still unclear. Here we investigated the pollution of metals, profiles of ARGs, mobile genetic elements (MGEs) and microbial community in mining-affected surface water and groundwater. The results showed that in the tested water samples, the concentrations of Zn and Mn were the highest, and Ni was the lowest. Higher abundances of ARGs with great proportion of sulfonamides, chloramphenicols and tetracyclines resistance genes were found in mining-affected water when compared with those without mining activities. Additionally, there were positive correlations between heavy metals (especially Ni, Zn and Mn) and these ARGs. Linear regression analysis suggested that MGEs were positively correlated with ARGs. In addition, total phosphorus was correlated with ARGs (p < 0.05). The microbial community was different between the mining-affected water and the reference (p < 0.05). Proteobacteria, Bacteroidetes and Actinobacteria were dominant phyla in the surface water and groundwater. Network analysis showed that many ARGs were significantly associated with these dominant bacteria, which suggested they might be potential hosts for these ARGs. These findings provide a clear evidence that the mining activities in the study area had a significant impact on surface water and groundwater to different degrees.

Horizontal and vertical gene transfer drive sediment antibiotic resistome in an urban lagoon system

Rapid urbanization has resulted in pervasive occurrence of antibiotic resistance genes (ARGs) in urban aquatic ecosystems. However, limited information is available concerning the ARG profiles and the forces responsible for their assembly in urban landscape lagoon systems. Here, we employed high-throughput quantitative PCR (HT-qPCR) to characterize the spatial variations of ARGs in surface and core sediments of Yundang Lagoon, China. The results indicated that the average richness and absolute abundance of ARGs were 11 and 53 times higher in the lagoon sediments as compared to pristine reference Tibetan lake sediments, highlighting the role of anthropogenic activities in ARG pollution. Co-occurrence network analysis indicated that various anaerobic prokaryotic genera belonging to Alpha-, Deltaproteobacteria, Bacteroidetes, Euryarchaeota, Firmicutes and Synergistetes were the potential hosts of ARGs. The partial least squares-path modeling (PLS-PM) analysis revealed positive and negative indirect effects of physicochemical factors and heavy metals on the lagoon ARG profiles, via biotic factors, respectively. The horizontal (mediated by mobile genetic elements) and vertical (mediated by prokaryotic communities) gene transfer may directly contribute the most to drive the abundance and composition of ARGs, respectively. Furthermore, the neutral community model demonstrated that the assembly of sediment ARG communities was jointly governed by deterministic and stochastic processes. Overall, this study provides novel insights into the diversity and distribution of ARGs in the benthic habitat of urban lagoon systems and underlying mechanisms for the spread and proliferation of ARGs.

Ciprofloxacin increased abundance of antibiotic resistance genes and shaped microbial community in epiphytic biofilm on Vallisneria spiralis in mesocosmic wetland

This study investigated the fate of ciprofloxacin (CIP) in wetlands dominated by Vallisneria spiralis. About 99% of CIP was degraded from overlaying water within 4 days of treatment but significantly inhibited the nutrient removal capacity (TN, TP, and COD) by causing a drastic reduction in microbial aggregation in epiphytic biofilm and bacterial biodiversity. CIP triggered resistance mechanisms among dominant bacteria phyla such as Proteobacteria, Actinobacteria, and Planctomycetes causing their increased relative abundance. Additionally, the relative abundances of eukaryotic microorganisms (including; Chloroplastida, Metazoa, and Rhizaria) and 13 ARGs subtypes (including; Efflux pump, Tetracycline, Multi-drug, Rifampin, Beta-lactam, Peptide, Trimethoprim) were significantly increased. While dominant metabolic pathways such as Carbohydrate, amino acid, energy and nucleotide metabolism were inhibited. This study revealed that V. spiralis has great sorption capacity for CIP than sediment and though CIP was effectively removed from the overlying water, it caused a prolonged effect on the epiphytic biofilm microbial communities.

Presence of antibiotic resistance genes and its association with antibiotic occurrence in Dilúvio River in southern Brazil

It is known that antibiotics are widely used in human and veterinary medicine. In some countries the use is controlled, however few restrictions to their use are enforced in many countries. Antibiotics and their metabolites can reach the water bodies through sewage systems, especially in those countries with partial or absent wastewater treatment systems. The overuse and misuse of antibiotics has been linked with the increase of antibiotic resistant bacteria. The relation between the occurrence of antibiotics and resistance genes in surface waters has been widely studied worldwide evincing the great importance of this subject. In this work, a methodology for quantification of 40 antibiotics of 5 different classes, in river water, by SPE-LC-MS/MS was validated. Samples were taken during a two-year period from Dilúvio River, a stream that crosses the city of Porto Alegre (RS - Brazil) and receives in nature domestic effluent. The methodology met the requirements of validation, with Limit of Quantification varying from 20 ng L^-1 to 100 ng L^-1. A total of 48 samples was analyzed for the presence of antibiotics for two years. From the 40 antibiotics analyzed, 8 of them (Azithromycin, Cephalexin, ciprofloxacin, clindamycin, norfloxacin, sulfadiazine, sulfamethoxazole and trimethoprim) were present in all sampling points in the range of <LOQ to 344 ng L^-1. The occurrence of antibiotics resistance genes in the sampling points was determined using qPCR. Specific primers were utilized to detected resistance genes to the β-lactam cephalexin (bla_TEM gene), to the quilonones ciprofloxacin and norfloxacin (qnrS gene), to the macrolides azithromycin and clindamycin (ermB gene), and to the sulfonamides sulfadiazine and sulfamethoxazole (sulI gene), which were quantified the selected water samples. Quantitative PCR analysis revealed the presence of ARGs in all samples, with the highest concentration found for bla_TEM.