Occurrence and distribution of antibiotic resistance genes in the coastal area of the Bohai Bay, China

Simulated Discharge of Ballast Water Reveals Potential Contribution to Spread of Antibiotic Resistance Genes in Geographically Isolated Receiving Waters

Background/Objectives: The propagation of antibiotic resistance genes (ARGs) poses a huge threat to environmental and human health. The ballast water from ships has been recognized as an important vector of ARGs. However, little is known about how ballast water from geographically isolated water affects ARGs in receiving waters. Methods: Herein, we investigated the changes in ARGs in receiving water by microcosm experiments simulating the discharge of ballast water. Results: The simulated discharge of ballast water increased the abundances of target ARGs, which were 1.3-5.6-fold higher in the mixture of ballast water and receiving water (microcosm M) than in receiving water at the end of the experiment. The enrichment of target ARGs was significantly associated with MGEs. Moreover, the discharge of ballast water changed the microbial communities in receiving water. Further network analysis identified potential ARG hosts, such as Pseudohongiellaa and Amphritea, with the abundance in microcosm M (0.23% and 0.036%) being higher than in receiving water (0.09% and 0.006%), the changes of which might be responsible for ARG variations. Conclusions: Overall, our findings suggest the discharge of ballast water might promote the spread of ARGs in different geographical waters and the corresponding ecological risks should not be ignored.

Antibiotic resistance genes (ARGs) and their eco-environmental response in the Bohai Sea sediments

Antibiotic resistance genes (ARGs) are an important class of pollutants in the environment. This study investigated the characteristics and ecological effects of ARGs in the Bohai Sea sediments. The results showed that ARGs are widely distributed, and exhibit significant spatial and subtype variations, with absolute abundance following the decreasing order of Liaodong Bay, Laizhou Bay, Bohai Bay, and Bohai Strait. Tetracycline ARGs dominated, comprising 50 % to 62 % of all ARGs, with tetM having the highest abundance at 1.43 × 107 copies/g. Symbiotic network analysis revealed that the phyla Deinococcota, Dadabacteria were serve as the primary likely host of ARGs. The ARGs have a wide range of potential hosts, and bacteria often carry multiple ARGs, enhancing the mobility and ecological niche adaptation of ARGs. This study will provide an important reference for assessing ARGs pollution in semi-enclosed seas.

Microbial Metagenomics Revealed the Diversity and Distribution Characteristics of Groundwater Microorganisms in the Middle and Lower Reaches of the Yangtze River Basin

Groundwater is one of the important freshwater resources on Earth and is closely related to human activities. As a good biological vector, a more diverse repertory of antibiotic resistance genes in the water environment would have a profound impact on human medical health. Therefore, this study conducted a metagenomic sequencing analysis of water samples from groundwater monitoring points in the middle and lower reaches of the Yangtze River to characterize microbial community composition and antibiotic resistance in the groundwater environment. Our results show that different microbial communities and community composition were the driving factors in the groundwater environment, and a diversity of antibiotic resistance genes in the groundwater environment was detected. The main source of antibiotic resistance gene host was determined by correlation tests and analyses. In this study, metagenomics was used for the first time to comprehensively analyze microbial communities in groundwater systems in the middle and lower reaches of the Yangtze River basin. The data obtained from this study serve as an invaluable resource and represent the basic metagenomic characteristics of groundwater microbial communities in the middle and lower reaches of the Yangtze River basin. These findings will be useful tools and provide a basis for future research on water microbial community and quality, greatly expanding the depth and breadth of our understanding of groundwater.

Occurrence and distribution of antibiotic pollution and antibiotic resistance genes in seagrass meadow sediments based on metagenomics

Seagrass meadows are one of the most important coastal ecosystems that provide essential ecological and economic services. The contamination levels of antibiotic and antibiotic resistance genes (ARGs) in coastal ecosystems are severely elevated owing to anthropogenic disturbances, such as terrestrial input, aquaculture effluent, and sewage discharge. However, few studies have focused on the occurrence and distribution of antibiotics and their corresponding ARGs in this habitat. Thus, we investigated the antibiotic and ARGs profiles, microbial communities, and ARG-carrying host bacteria in typical seagrass meadow sediments collected from Swan Lake, Caofeidian shoal harbor, Qingdao Bay, and Sishili Bay in the Bohai Sea and northern Yellow Sea. The total concentrations of 30 detected antibiotics ranged from 99.35 to 478.02 μg/kg, tetracyclines were more prevalent than other antibiotics. Metagenomic analyses showed that 342 ARG subtypes associated with 22 ARG types were identified in the seagrass meadow sediments. Multidrug resistance genes and RanA were the most dominant ARG types and subtypes, respectively. Co-occurrence network analysis revealed that Halioglobus, Zeaxanthinibacter, and Aureitalea may be potential hosts at the genus level, and the relative abundances of these bacteria were higher in Sishili Bay than those in other areas. This study provided important insights into the pollution status of antibiotics and ARGs in typical seagrass meadow sediments. Effective management should be performed to control the potential ecological health risks in seagrass meadow ecosystems.

Fish skin mucosal surface becomes a barrier of antibiotic resistance genes under apramycin exposure

Antibiotic resistance genes (ARGs) are a kind of emerging environmental contamination, and are commonly found in antibiotic application situations, attracting wide attention. Fish skin mucosal surface (SMS), as the contact interface between fish and water, is the first line of defense against external pollutant invasion. Antibiotics are widely used in aquaculture, and SMS may be exposed to antibiotics. However, what happens to SMS when antibiotics are applied, and whether ARGs are enriched in SMS are not clear. In this study, Zebrafish (Danio rerio) were exposed to antibiotic and antibiotic resistant bacteria in the laboratory to simulate the aquaculture situation, and the effects of SMS on the spread of ARGs were explored. The results showed that SMS maintained the stability of the bacterial abundance and diversity under apramycin (APR) and bacterial exposure effectively. Until 11 days after stopping APR exposure, the abundance of ARGs in SMS (mean value was 3.32 × 10-3 copies/16S rRNA copies) still did not recover to the initial stage before exposure, which means that enriched ARGs in SMS were persistently remained. Moreover, non-specific immunity played an important role in resisting infection of external contamination. Besides, among antioxidant proteins, superoxide dismutase showed the highest activity. Consequently, it showed that SMS became a barrier of antibiotic resistance genes under APR exposure, and ARGs in SMS were difficult to remove once colonized. This study provided a reference for understanding the transmission, enrichment process, and ecological impact of antibiotics and ARGs in aquatic environments.

A review of spatial distribution of typical antibiotic resistance genes in marine environment surrounding China

Antibiotic resistance genes (ARGs) have been steadily increasing due to the extensive overuse of antibiotics in the marine environment. Currently, the research considering ARGs distribution in marine ecosystems gains more interest. As the coastal sea has been regarded as one of the most polluted areas by antibiotic contaminants in China. However, no comprehensive review of the spatial distribution of ARGs in marine environment surrounding China. The main objective of this review is to investigate the level, characteristic, and spatial distribution of ARGs in the marine environment (seawater and sediments) surrounding China. Key sea areas, such as Bohai Sea, Yellow Sea, East China Sea, and South China Sea were selected in this review. The marine environment was the reservoir of ARGs, and ARGs in seawater were generally 1 to 2 orders of magnitude higher than that in sediments. Total ARGs were more abundant in the Yellow Sea, followed by the Bohai Sea, the East China Sea, and the South China Sea. This study raises questions regarding the spread and distribution for antibiotic resistance in marine environments.

Sulfamethoxazole stress endangers the gut health of sea cucumber (Apostichopus japonicus) and affects host metabolism

Sulfamethoxazole (SMZ) is a frequently detected antibiotic in the environment, and there is a growing concern about its potential toxic effects on aquatic organisms. sea cucumber (Apostichopus japonicas) is a benthic invertebrate whose gut acts as a primary immune defense and serves critical protective barrier. In this study, growth performance, histology, gut microbiota, and metabolomics analyses were performed to investigate the toxic response in the intestine of sea cucumber effects caused by SMZ stress for 56 d by evaluating with different concentrations of SMZ (0, 1.2×10-3, and 1.2 mg/L). The weight gain rate of sea cucumbers under SMZ stress showed significant decrease, indicating that the growth of sea cucumbers was hindered. Analysis of the intestinal morphological features indicated that SMZ stimulation resulted in atrophy of the sea cucumber gut. In the 1.2×10-3 mg/L concentration, the thickness of muscle and mucosal layers was reduced by 12.40% and 21.39%, while in the 1.2 mg/L concentration, the reductions were 35.08% and 26.98%. The abundance and diversity of sea cucumber intestinal bacteria decreased significantly (P < 0.05) under the influence of SMZ. Notably, the intestinal bacteria of sea cucumber became homogenized with the increase in SMZ concentration, and the relative abundance of Ralstonia reached 81.64% under the stress of 1.2 mg/L concentration. The SMZ stress significantly impacted host metabolism and disrupted balance, particularly in L-threonine, L-tyrosine, neuronic acid, piperine, and docosapentaenoic acid. SMZ leads to dysregulation of metabolites, resulting in growth inhibition and potential inflammatory responses that could adversely affect the normal activities of aquatic organisms. Further metabolic pathway enrichment analyses demonstrated that impaired biosynthesis of unsaturated fatty acids and aminoacyl-tRNA biosynthesis metabolic pathway were major reasons for SMZ stress-induced intestinal bacteria dysbiosis. This research aims to provide some theoretical evidence for the ecological hazard assessment of antibiotics in water.

Wastewater surveillance for antibiotics and resistance genes in a river catchment: Spatiotemporal variations and the main drivers

Wastewater-based epidemiology (WBE) is used for mining information about public health such as antibiotics resistance. This study investigated the distribution profiles of six types of antibiotic resistance genes (ARGs) in wastewater and rivers in Wuhu City, China. The levels of ARGs found in the Qingyijiang River were significantly higher than other rivers, and were comparable to effluent levels. Among the ARGs, sulfonamides ARGs and intI1 were the predominant in both wastewaters and rivers. Additionally, the concentrations of ARGs were higher on weekends as opposed to weekdays. Their distribution patterns remained consistent inter-week and inter-season using linear regression analysis (p < 0.001). Interestingly, the occurrence levels of ARGs in wastewaters during spring were significantly higher than in autumn, although insignificant in rivers. The apparent removal rate of ARGs in domestic wastewater sources ranged from 61.52-99.29%, except for qepA (-1.91% to 81.09%), whereas the removal rates in mixed domestic and industrial wastewaters showed a marked decrease (-92.94% to 76.67%). A correlation network analysis revealed that azithromycin and erythromycin were key antibiotics, while blaNDM-1, tetM, tetB, and ermB were identified as key ARGs. Sulfonamide and fluoroquinolone antibiotics, and tetracycline and macrolide ARGs were the primary contributors. Linear mixed models demonstrated that socio-economic variables positively impacted the occurrence levels of ARGs, whereas wastewater flow and river runoff were the negative drivers for their concentrations in wastewaters and surface waters, respectively. Overall, this WBE study contributes to the understanding of spatiotemporal profiles and main drivers of the occurrence of ARGs in wastewater and receiving water.

Distribution characteristics of antibiotic resistance genes and microbial diversity in the inshore aquaculture area of Wenchang, Hainan, China

The rapid development of marine aquaculture has led to the increased use and release of antibiotics into the marine environment, consequently contributing to the emergence of antibiotic resistance. Information on antibiotic resistance in nearshore marine aquaculture areas remains limited, and research on the microbial composition and potential hosts of antibiotic resistance genes (ARGs) in marine aquaculture areas is scarce. This study used SmartChip real-time fluorescent quantitative PCR and qPCR to quantitatively analyze 44 ARGs and 10 mobile genetic elements (MGEs) genes in 12 sampling points in the nearshore aquaculture area of Wenchang. High-throughput sequencing of 16S rRNA was used to study microbial diversity in the study area, to clarify the correlation between ARGs, MGEs, and microbial diversity, and to determine the possible sources and potential hosts of ARGs. The results showed that a total of 37 ARGs and 8 MGEs were detected in the study area. The detection rate of 9 ARGs (aac(6')-Ib(aka aacA4)-02, catA1, cmlA, cfr, sul1, sul2, sulA/folP-01, tetC, tetX) was 100 %. The absolute abundance of ARGs in the 12 sampling points ranged from 2.75 × 107 to 3.79 × 1010 copies·L-1, and the absolute abundance of MGEs was 1.30 × 105 to 2.54 × 107 copies·L-1, which was relatively high compared to other research areas. ARGs and MGEs were significantly correlated, indicating that MGEs play an important role as a mediator in the spread of ARGs. At the phylum level, Proteobacteria and Cyanobacteria were the dominant bacteria in the study area, with HIMB11 and unidentifiedChloroplast being the dominant levels, respectively. Network analysis of ARGs and microorganisms (genus level) revealed that Cognatishimia, Thalassobius, Aestuariicoccus, Thalassotalea, and Vibrio were significantly correlated with multiple ARGs and were the main potential hosts of ARGs in the nearshore waters of Wenchang.

Investigation of the antimicrobial susceptibility patterns of marine cyanobacteria in Bohai Bay: Cyanobacteria may be important hosts of antibiotic resistance genes in marine environment

Marine cyanobacteria, as widely distributed and photosynthetically autotrophic bacteria in the ocean, may contribute to the global dissemination of antibiotic resistance genes (ARGs) and develop a different antimicrobial susceptibility pattern from heterotrophic bacteria and cyanobacteria from freshwater environments. However, studies on antimicrobial susceptibility and the carriage of ARGs in marine cyanobacteria are still very limited. In this study, the antibiotic resistance characteristics of cyanobacteria in nearshore waters were examined through field monitoring and laboratory investigations, which included PCR detection and ARG transformation. The results showed a positive correlation between marine cyanobacteria and some ARGs in the nearshore waters of Bohai Bay. Moreover, most screened cyanobacteria showed high minimum inhibitory concentration (MIC) values for polymyxins, tetracyclines, kanamycin, and sulfonamides, moderate MIC values for streptomycin, chloramphenicol, rifampicin, and norfloxacin, and low MIC values for roxithromycin and cephalosporins. The blaTEM, blaKPC, sul1, sul2, strA, tetA, tetB, tetC, tetM, mdfA, and intI1 genes were detected in the screened marine cyanobacteria. The highest detection rates were observed for blaTEM (93.3 %), sul1 (56.6 %), sul2 (90 %), and strA (73.3 %). The detection rate of tetA (33.3 %) was the highest among the tetracycline resistance genes, and mdfA, a multidrug-resistant pump gene with resistance to tetracycline, also showed a high detection level (23.3 %). Overall, most of the screened marine cyanobacteria were found to tolerate multiple antibiotics in seawater, and the condition of the ARGs carriage was serious. Furthermore, the screened marine Synechocystis sp. C12-2 demonstrated the ability to accept ARGs on the RP4 plasmid through natural transformation and showed reduced sensitivity to ampicillin, suggesting the possibility that some marine cyanobacteria could acquire ARGs from the environment through horizontal gene transfer. Thus, marine cyanobacteria may play an important role in the propagation of marine ARGs.

Adsorption Performance and Mechanisms of Tetracycline on Clay Minerals in Estuaries and Nearby Coastal Areas

Clay minerals in sediments have strong adsorption capacities for pollutants, but their role in the distribution of antibiotics in estuaries and nearby coastal areas is unclear. We evaluated the clay mineral montmorillonite (SWy-2) adsorption capacity for tetracycline (TC). We assessed the adsorption capacity of SWy-2 for TC by measuring the removal percentage of 30 mg/L TC over time. The effects of pH and ionic strength on the TC adsorption onto SWy-2 were investigated. We analyzed the kinetics of TC adsorption using a pseudo-second-order model and determined the adsorption isotherm using the Langmuir equation. SWy-2 particles were characterized using zeta potential, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analyses before and after TC adsorption. The removal percentage of 30 mg/L TC by SWy-2 reached 70.76% within 0.25 h and gradually increased to 78.64% at 6 h. TC adsorption was influenced by pH and ionic strength, where low pH enhanced and high ionic strength reduced the adsorption. The kinetics of TC adsorption followed a pseudo-second-order model, and the adsorption isotherm adhered to the Langmuir equation. The saturated adsorption capacity (qmax) of SWy-2 for TC was 227.27 mg/g. Zeta potential, FTIR, and XRD analyses confirmed that electrostatic interactions and chemical bonds played a significant role in the TC adsorption by SWy-2. SWy-2 clay mineral exhibits a substantial adsorption capacity for TC, indicating its potential as an effective sorbent to mitigate antibiotic contamination in estuaries and nearby coastal areas. The observed effects of pH and ionic strength on TC adsorption have implications for the environmental fate and transport of antibiotics. The pseudo-second-order kinetic model and Langmuir isotherm equation provide valuable insights into the adsorption behavior and capacity of TC on SWy-2. Characterization analyses support the involvement of electrostatic interactions and chemical bonds in the SWy-2-TC adsorption mechanism.

Modelling based study on the occurrence characteristics and influencing factors of the typical antibiotics in Bohai Bay

Previous studies have demonstrated that antibiotics have the potential impacts to ecosystems and human health. However, due to their various classes and distinct characteristics, creating comprehensive, integrated and dynamic simulations has proven to be a challenging task. In this study, a 3D hydrodynamic-contaminant model was developed to gain a better understanding of the transportation and prevalence of antibiotics in the Bohai Bay. Specifically, we focused on four types of antibiotics as examples. To accurately capture the dynamic distribution of antibiotics, both transport and biochemical processes were taken into account. Based on this model, the antibiotics' spatial and temporal distribution was examined, the potential impact of the future antibiotics consumption and climate change was also analyzed. The study found that human activity has a greater impact on the presence of antibiotics in Bohai Bay than temperature rise. Based on the current consumption rate, the total amount of antibiotics in Bohai Bay may increase by 10 ng/L and affect nearly one third of the study area within the next 20-30 years. The significant impact of human activity on water contamination in coastal areas may also have implications for other coastal regions. This finding can provide a valuable framework for pollution prevention and control.

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.

A global atlas of marine antibiotic resistance genes and their expression

Oceans serve as global reservoirs of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs). However, little is known about the traits and expression of ARGs in response to environmental factors. We analyzed 347 metagenomes and 182 metatranscriptomes to determine the distribution, hosts, and expression of ARGs in oceans. Our study found that the diversity and abundance of ARGs varied with latitude and depth. The core marine resistome mainly conferred glycopeptide and multidrug resistance. The hosts of this resistome were mainly limited to the core marine microbiome, with phylogenetic barriers to the horizontal transfer of ARGs, transfers being more frequent within species than between species. Sixty-five percent of the marine ARGs identified were expressed. More than 90% of high-risk ARGs were more likely to be expressed. Anthropogenic activity might affect the expression of ARGs by altering nitrate and phosphate concentrations and ocean temperature. Machine-learning models predict >97% of marine ARGs will change expression by 2100. High-risk ARGs will shift to low latitudes and regions with high anthropogenic activity, such as the Pacific and Atlantic Oceans. Certain ARGs serve a dual role in antibiotic resistance and potentially participate in element cycling, along with other unknown functions. Determining whether changes in ARG expression are beneficial to ecosystems and human health is challenging without comprehensive understanding of their functions. Our study identified a core resistome in the oceans and quantified the expression of ARGs for the development of future control strategies under global change.

Metagenomic analysis to determine the characteristics of antibiotic resistance genes in typical antibiotic-contaminated sediments

Comprehensive studies of the effects of various physical and chemical variables (including heavy metals), antibiotics, and microorganisms in the environment on antibiotic resistance genes are rare. We collected sediment samples from the Shatian Lake aquaculture area and surrounding lakes and rivers located in Shanghai, China. The spatial distribution of sediment ARGs was assessed by metagenomic analysis that revealed 26 ARG types (510 subtypes), dominated by Multidrug, β-lactam, Aminoglycoside, Glycopeptides, Fluoroquinolone, and Tetracyline. Redundancy discriminant analysis indicated that antibiotics (SAs and MLs) in the aqueous environment and sediment along with water TN and TP were the key variables affecting the abundance distribution of total ARGs. However, the main environmental drivers and key influences differed among the different ARGs. For total ARGs, the environmental subtypes affecting their structural composition and distribution characteristics were mainly antibiotic residues. Procrustes analysis showed a significant correlation between ARGs and microbial communities in the sediment in the survey area. Network analysis revealed that most of the target ARGs were significantly and positively correlated with microorganisms, and a small number of ARGs (e.g., rpoB, mdtC, and efpA) were highly significantly and positively correlated with microorganisms (e.g., Knoellia, Tetrasphaera, and Gemmatirosa). Potential hosts for the major ARGs included Actinobacteria, Proteobacteria, and Gemmatimonadetes. Our study provides new insight and a comprehensive assessment of the distribution and abundance of ARGs and the drivers of ARG occurrence and transmission.

Microbial community structure and antibiotic resistance profiles in sediments with long-term aquaculture history

The aim of this investigation was to examine the microbial populations and their resistance patterns towards antibiotics, including the impact of nitrogen metabolism in response to the reintroduction of antibiotics, as well as the presence of resistance genes in sediments from shrimp ponds that have been utilized for extended periods of 5, 15, and over 30 years. Results showed that the sediments exhibited a high prevalence of Proteobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, and Oxyphotobacteria as the most abundant bacterial phyla, accounting for 70.35-77.43% of the total bacterial community. The five most abundant phyla of fungi detected in all sediments, namely Rozellomycota, Ascomycota, Aphelidiomycota, Basidiomycota, and Mortierellomycota, constituted 24.26-32.54% of the total fungal community. It was highly probable that the Proteobacteria and Bacteroidetes phyla serve as the primary reservoir of antibiotic-resistant bacteria (ARB) in the sediment, which included various genera like Sulfurovum, Woeseia, Sulfurimonas, Desulfosarcina, and Robiginitalea. Among these genera, Sulfurovum appeared to be the most widespread in the sediment of aquaculture ponds that have been in operation for more than three decades, while Woeseia dominated in ponds that have been recently reclaimed and have a 15-year aquaculture history. Antibiotic resistance genes (ARGs) were categorized into seven distinct groups according to their mechanism of action. The prevalence of multidrug-resistant ARGs was found to be the highest among all types, with an abundance ranging from 8.74 × 10^-2 to 1.90 × 10^-1 copies per 16S rRNA gene copies. The results of a comparative analysis of sediment samples with varying aquaculture histories indicated that the total relative abundance of ARGs was significantly diminished in sediment with a 15-year aquaculture history as opposed to sediment with either a 5-year or 30-year aquaculture history. Another assessment of antibiotic resistances in aquaculture sediments involved an examination of the effects of reintroducing antibiotics on nitrogen metabolism processes. The findings revealed that the rates of ammonification, nitrification, and denitrification in the sediment with a history of 5 years and 15 years, decreased as the concentration of oxytetracycline increased from 1 to 300, and 2000 mg/kg, and inhibitory effects were found to be less pronounced in sediments with a 5-year history compared to those with a 15-year history. In contrast, oxytetracycline exposure led to a significant decrease in the rates of these processes in aquaculture pond sediments with a >30 years of aquaculture history across all the concentrations tested. The emergence and dissemination of antibiotic resistance profiles in aquaculture environments requires attention in future aquaculture management.

Response characteristics of antibiotic resistance genes and bacterial communities during agricultural waste composting: Focusing on biogas residue combined with biochar amendments

This research investigated biogas residue and biochar addition on antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and changes in bacterial community during agricultural waste composting. Sequencing technique investigated bacterial community structure and ARGs, MGEs changes. Correlations among physicochemical factors, ARGs, MGEs, and bacterial community structure were determined using redundancy analysis. Results confirmed that biochar and biogas residue amendments effectively lowered the contents of ARGs and MGEs. The main ARGs detected was sul1. Proteobacteria and Firmicutes were the main host bacteria strongly associated with the dissemination of ARGs. The dynamic characteristics of the bacterial community were strongly correlated with pile temperature and pH (P < 0.05). Redundancy and network analysis revealed that nitrate, intI1, and Firmicutes mainly affected the in ARGs changes. Therefore, regulating these key variables would effectively suppress the ARGs spread and risk of compost use.

The reasons for the spatial and media distribution variations of ARGs in a typical semi-enclosed bay

Antibiotic resistance genes (ARGs) are considered a newly emerging contaminant. This study aimed to investigate the spatial and media distribution patterns of ARGs in Jiaozhou Bay, as well as the reasons behind these patterns. The results revealed that aminoglycoside and MLSB resistant genes predominated in all samples, and the relative abundance of ARGs ranging from 10^-6 to 10^-2, 10^-6 to 10^-3 and 10^-5 to 10^-2 copies/16S rRNA in coastal water, bay water, and sediments, respectively. The significant spatial variation of ARGs was explained by the fact that the coastal water was more susceptible to human activities, whereas environmental physicochemical factors played a crucial role in the bay water. The intrinsic reason for the media distribution variation was the different assembly processes in the two media, while the external reason was that the ARGs in the water and sediments were mainly influenced by environmental physicochemical factors and heavy metals, respectively.

A Comprehensive Contamination Investigation of Bohai Bay Seawater: Antibiotics Occurrence, Distribution, Ecological Risks and Their Interactive Factors

A comprehensive, large-scale coastal investigation of antibiotics in seawater from Bohai Bay is lacking. Therefore, in this study, we investigated the occurrence and ecological risks of 45 antibiotics belonging to 5 classes in seawater from Bohai Bay, as well as their inter-relation with trace elements and other contaminants. The results show that tetracyclines (TCs) were detected in the highest concentration among the five classes (in the range of 0.6−2.0 μg/L). The total concentrations of the five classes of antibiotics were detected in the following order: tetracyclines (TCs) > quinolones (QAs) > sulfonamides (SAs) > macrolides (MAs) > lactams (LAs). Higher antibiotic concentrations were detected at the sampling sites closest to the coast or the shipping port. Among seven trace elements, four were quantitatively detected, with Zn representing the highest concentration. Antibiotic residuals were found to be positively correlated with total organic carbon (TOC), conductivity (Ec) and suspended solids (SS); pH and NH4+-N usually showed a negative correlation with antibiotics; TN and TP also exhibited relationships with antibiotics. The risk quotient (RQ) was calculated for different antibiotics at different sites. It was found that antibiotics pose higher risks to algae than to invertebrates or fish; sulfamethoxazole, enrofloxacin and ofloxacin were all found to pose high risk to algae at some of the sampling sites. Structural equation model (SEM) results show that trace elements, antibiotic levels and EC50 are the main factors affecting the ecological risks of antibiotics.

Irrigation Ponds as Sources of Antimicrobial-Resistant Bacteria in Agricultural Areas with Intensive Use of Poultry Litter

Poultry litter is widely used worldwide as an organic fertilizer in agriculture. However, poultry litter may contain high concentrations of antibiotics and/or antimicrobial-resistant bacteria (ARB), which can be mobilized through soil erosion to water bodies, contributing to the spread of antimicrobial resistance genes (ARGs) in the environment. To better comprehend this kind of mobilization, the bacterial communities of four ponds used for irrigation in agricultural and poultry production areas were determined in two periods of the year: at the beginning (low volume of rainfall) and at the end of the rainy season (high volume of rainfall). 16S rRNA gene sequencing revealed not only significantly different bacterial community structures and compositions among the four ponds but also between the samplings. When the DNA obtained from the water samples was PCR amplified using primers for ARGs, those encoding integrases (intI1) and resistance to sulfonamides (sul1 and sul2) and β-lactams (blaGES, blaTEM and blaSHV) were detected in three ponds. Moreover, bacterial strains were isolated from CHROMagar plates supplemented with sulfamethoxazole, ceftriaxone or ciprofloxacin and identified as belonging to clinically important Enterobacteriaceae. The results presented here indicate a potential risk of spreading ARB through water resources in agricultural areas with extensive fertilization with poultry litter.

Occurrence and distribution of antibiotics in coastal water of the Taizhou Bay, China: impacts of industrial activities and marine aquaculture

The occurrence, spatial distribution, and source analysis of antibiotics in global coastal waters and estuaries are not well documented or understood. Therefore, the distribution of 14 antibiotics in inflowing river and bay water of Taizhou Bay, East China Sea, was studied. Thirteen antibiotics, excluding roxithromycin (ROM), were all detected in inflowing river and bay water. The total antibiotic concentrations in bay water ranged from 3126.62 to 26,531.48 ng/L, which were significantly higher than those in the inflowing river (17.20-25,090.25 ng/L). Macrolides (MAs) and sulfonamides (SAs) were dominant in inflowing river (accounting for 24.40% and 74.9% of the total antibiotic concentrations, respectively), while SAs in bay water (93.6% of the total concentrations). Among them, clindamycin (CLI) (concentration range: ND-8414 ng/L, mean 1437.59 ng/L) and sulfadimidine (SMX) (ND-25,184.00 ng/L, mean concentrations: 9107.88 ng/L) were the highest in those surface water samples. Source analysis showed that MAs and SAs in the inflowing river mainly came from the wastewater discharge of the surrounding residents and pharmaceutical companies, while SAs in the bay water mainly came from surrounding industrial activities and mariculture. However, the contribution of the inflowing river to the bay water cannot be ignored. The risk assessment showed that SMX and ofloxacin (OFX) have potential ecological risks. These data will support the various sectors of the environment in developing management strategies and to prevent antibiotic pollution.

Distribution and co-occurrence patterns of antibiotic resistance genes in black soils in Northeast China

Black soils (Mollisols) are among the most important soil resources for crop production and food security. In China, they are mainly distributed in the northeastern region. To investigate soil antibiotic resistance distribution patterns and monitor soil quality, we randomly chose nine corn fields in Northeast China and analyzed the antibiotic resistance gene (ARG) distribution and co-occurrence patterns on the basis of high-throughput approaches and network analyses. High genetic diversity (136 unique genes) and low ARG abundances (10^-5-10^-2 copies/16S rRNA gene copy) were detected, with relatively few interactions among ARGs. Type I integron genes were prevalent in the soil and were positively correlated with ARGs, which may increase the risk of ARG transmission. Most ARGs were strongly associated with microorganisms. Moreover, several ARGs were significantly correlated with antibiotics, nutrients, and metal elements. The generation and dissemination of ARGs, which were most likely mediated by mobile genetic elements (MGEs) and bacteria, were affected by environmental conditions. These results provide insights into the widespread co-occurrence patterns in soil resistomes.

Mechanism of enrofloxacin-induced multidrug resistance in the pathogenic Vibrio harveyi from diseased abalones

Vibrio harveyi infection had caused severe economic losses in aquaculture. A pathogenic V. harveyi strain had been successfully induced to be a multiple-resistant strain by enrofloxacin (EFX), then the mechanism of multidrug resistance was analyzed. It suggested that the minimum inhibitory concentration of EFX increased by 32-folds. Results of the Kirby-Bauer test showed that the inhibitory zone diameter was 25.3 mm for the sensitive strain (labeled as HL-S) and 8.5 mm for the resistant strain (labeled as HL-R). After 20 serial passages, even when the stress of EFX was removed, the resistance persisted. After induction of EFX, HL-R resisted to other fluoroquinolones, it even resisted to furazolidone and streptomycin, although it was sensitive to these antibiotics initially. Its sensitivity to rifampicin and doxycycline also decreased obviously. Results showed that 3522 differentially expressed genes were identified. Expression of the multidrugs efflux resistance-nodulation-cell division was significantly upregulated (164.61-folds) in HL-R. Other key genes connected with drug efflux were also upregulated significantly (p<0.05). Notably, recA encoded for recombination protein was upregulated significantly, lexA was downregulated significantly in HL-R. Research results showed that the efflux system and the save our souls system have played crucial roles during the development of multidrug resistance of V. harveyi.

Unveiling the occurrence, hosts and mobility potential of antibiotic resistance genes in the deep ocean

As emerging microbial contaminants, antibiotic resistance genes (ARGs) are widely reported in the neritic zone. However, the profiles of ARGs in the deep ocean have not yet been fully resolved. In this study, the distribution, hosts, and mobility potential of ARGs at different water depths in the Western Pacific (WP) were investigated and compared to those in Bohai Sea (BH) waters using environmental parameter measurements, amplicon sequencing, metagenomic assembly and binning approaches. Our results showed that the top eight most abundant known ARG types in WP and BH waters were multidrug (39.85%), peptide (14.98%), aminoglycoside (11.33%), macrolide-lincosamide-streptogramin (MLS, 4.06%), tetracycline (3.74%), beta-lactam (3.12%), fluoroquinolone (1.79%) and rifamycin (1.24%). The ARGs observed in mesopelagic and bathypelagic waters were abundant and diverse as those observed in neritic waters, indicating that deep-sea water could be another environmental reservoir for ARGs. For deep-sea ARGs, members from classes Gammaproteobacteria (70%) and Alphaproteobacteria (21.1%) were the most important potential hosts. In addition, mobile genetic element analysis suggested that the ARG migration potential in dee sea water (> 1000 m) was relatively high. Overall, our findings expanded the understanding of ARGs in deep seawater and provided guidance for ARG pollution control and risk prediction.

Occurrence and distribution of antibiotics and antibiotic resistance genes in the guts of shrimp from different coastal areas of China

With the continuous increase in shrimp (Litopenaeus vannamei) aquaculture production, the widespread use of antibiotics as a means of preventing and treating diseases has adversely affected the environment, animal health and symbiotic microorganisms in gut environments. At the same time, antibiotic resistance genes (ARGs) are widespread in aquaculture and pose a great threat to aquatic organisms and humans. Therefore, in the present study, the occurrence and distribution of 17 antibiotics, ARGs and mobile genetic elements (MGEs) were detected in the guts of shrimp collected from 12 coastal regions of China. The results showed that sulfadiazine, ciprofloxacin and norfloxacin were detectable in the guts of L. vannamei at all sampling sites. Sul1, sul2, floR and intI-1 were also detected in the guts of L. vannamei at all sampling sites. The total relative abundances of ARGs and MGEs were significantly positively correlated according to Pearson correlation analysis. Sulfonamide resistance genes (sul1 and sul2) were significantly positively correlated with intI-1. These results indicated that MGEs could increase the risk of horizontal gene transfer of ARGs in a gut environment. MGEs are the most important factors promoting the spread of ARGs. Correlation analysis showed that sulfadiazine was significantly positively correlated with sul1 and sul2 and that fluoroquinolone antibiotics were significantly positively correlated with floR, indicating that antibiotics could induce the production of ARGs. Network analysis indicated that Iamia and Alkaliphilus species may harbor the most antibiotic resistance genes, and these bacteria were closely related to the proliferation and spread of ARGs in a gut environment. Antibiotic use and the spread of ARGs in mariculture systems may have negative effects on shrimp and human health. The use of antibiotics should be strictly regulated to control contaminants in mariculture systems, including pathogens and ARGs, thereby reducing potential risks to human health.

Antibiotics and resistant genes in the gut of Chinese nine kinds of freshwater or marine fish

Antibiotic resistance genes (ARGs) may lead to bacterial resistance and using antibiotics will promote ARGs spread. Large amounts of antibiotics were used in aquaculture, but little attention was paid to the antibiotic resistant in fish gut. In this study, nine kinds of Chinese freshwater and marine fish were acquired in a city of northern China to test the amount of antibiotics and ARGs residues in their intestinal contents. The results showed that 4 kinds of antibiotics were detected from the intestinal contents, including Doxycycline (DOX), Tetracycline (TC), Sulfamethoxazole (SMX) and Roxithromycin (ROX), and the antibiotics with the largest detected amount was ROX in Sardinops sagax (2.83 μg kg^-1). Ten kinds of ARGs were detected from the intestinal contents, including strA, strB, ermB, bla_TEM, oxa-30, qnrB, qnrD, sul1, sul2 and tetB, as well as one type of integron intI1. The most abundant ARGs were bla_TEM. Correlation analysis showed huge difference between freshwater fish and marine fish. The results can improve our understanding of the antibiotics and ARGs residues in edible fish.

Distribution, transfer, ecological and human health risks of antibiotics in bay ecosystems

Antibiotics have been widely detected in bay ecosystems, yet little is known regarding their distribution, composition, sources, ecological and human health risks at the regional scale. We developed a systematic framework to mine data from existing publications and compiled an antibiotic concentration-based dataset containing 439 samples from 30 bays, and compared antibiotics across bays and matrices (water, sediment, and biota). Antibiotic concentrations varied considerably between bays, with hotspots occurring in East Asia. The main categories of antibiotics in waters included sulfonamide and macrolide, while tetracycline, quinolone, and macrolide antibiotics were prevalent in sediments. The main sources of antibiotics in bays included sewage treatment plant effluent, domestic sewage, agriculture runoff, and discharges from mariculture activities. Antibiotics with high ecological risks mainly included sulfamethoxazole, erythromycin, clarithromycin, and oxytetracycline. Erythromycin posed a considerable risk to human health, and the human health risks presented by other antibiotics were negligible. Regional variations of concentrations correspond to the uneven geographic consumption of antibiotics and their removal rate during wastewater treatment. Differences in antibiotics' composition between matrices are associated mainly with the physicochemical properties of antibiotics (e.g., molecular structure, solubility, and stability) and the content of total organic carbon, metal ions, chlorophyll a, and clay minerals in the sediments. To reduce the ecological and human health implications, priority should be given to the removal of erythromycin, sulfamethoxazole, oxytetracycline, and clarithromycin, with a special focus on their treatment in the Asian bay areas.

Evidence for Long-Term Anthropogenic Pollution: The Hadal Trench as a Depository and Indicator for Dissemination of Antibiotic Resistance Genes

Knowledge of the distribution and dissemination of antibiotic resistance genes (ARGs) is essential for understanding anthropogenic impacts on natural ecosystems. The transportation of ARGs via aquatic environments is significant and has received great attention, but whether there has been anthropogenic ARG pollution to the hadal ocean ecosystem has not been well explored. For investigating ecological health concerns, we profiled the ARG occurrence in sediments of the Mariana Trench (MT) (10 890 m), the deepest region of the ocean. Metagenomic-based ARG profiles showed a sudden increase of abundance and diversity in the surface layer of MT sediments reaching 2.73 × 10^-2 copy/cell and 81 subtypes, and a high percentage of ∼63.6% anthropogenic pollution sources was predicted by the Bayesian-modeling classification method. These together suggested that ARG accumulation and anthropogenic impacts have already permeated into the bottom of the deepest corner on the earth. Moreover, six ARG-carrying draft genomes were retrieved using a metagenomic binning strategy, one of which assigned as Streptococcus was identified as a potential bacterial host to contribute to the ARG accumulation in MT, carrying ermF, tetM, tetQ, cfxA2, PBP-2X, and PBP-1A. We propose that the MT ecosystem needs further long-term monitoring for the assessment of human impacts, and our identified three biomarkers (cfxA2, ermF, and mefA) could be used for the rapid monitoring of anthropogenic pollution. Together our findings imply that anthropogenic pollution has penetrated into the deepest region of the ocean and urge for better pollution control to reduce the risk of ARG dissemination to prevent the consistent accumulation and potential threat to the natural environment.

Persisting antibiotic resistance gene pollution and its association with human sewage sources in tropical marine beach waters

Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are pollutants of worldwide concern that threaten human health and ecosystems. Anthropogenic activities and wastewater could be ARB and ARG pollution sources; however, research on ARG abundance and microbial source tracking (MST) of contamination in tropical marine waters is limited. This study examined spatiotemporal variations of six ARGs (bla_NDM, bla_TEM, bla_VIM, mcr-1, sul1, and tetQ) against the widely used antibiotic groups and a class 1 integron-integrase gene (intI1) at two Thai tropical recreational beaches (n = 41). Correlations between ARGs and sewage-specific MST markers (i.e., crAssphage and human polyomaviruses [HPyVs]) and fecal indicator bacteria (i.e., total coliforms, fecal coliforms, and enterococci) were also investigated. Bla_TEM, intI1, sul1, and tetQ were ubiquitous at both beaches (85.4-100% detection rate); intI1 was the most abundant (3-6 orders in log₁₀ copies/100 mL), followed by bla_TEM (2-4 orders), sul1 (2-3 orders), and tetQ (2-4 orders). Bla_NDM was found in 7.3% (up to 4 orders), and no mcr-1 was detected. Interestingly, bla_VIM was prevalent at one beach (2-5 orders; n = 17), but found in only one sample at the other (4 orders). Temporal, but not spatial, differences were noticed; bla_TEM was at higher levels in the wet season. IntI1 correlated with sul1 and tetQ (Spearman's rho = 0.47-0.97), suggesting potential horizontal gene transfer. CrAssphage, but not HPyVs, correlated with intI1, sul1, and tetQ (Spearman's rho = 0.50-0.74). Higher numbers of ARGs tended to co-occur in samples with higher crAssphage concentrations, implying sewage contribution to the marine water, with a persisting ARG background. This study provides insight into the ARG pollution status of tropical coastal waters and suggests crAssphage as a proxy for ARG pollution, which could facilitate effective management policies to minimize ARG dissemination in marine environments.

A systematic review of antibiotics and antibiotic resistance genes in estuarine and coastal environments

Antibiotics and antibiotic resistance genes (ARGs) are prevalent in estuarine and coastal environments due to substantial terrestrial input, aquaculture effluent, and sewage discharge. In this article, based on peer-reviewed papers, the sources, spatial patterns, driving factors, and environmental implications of antibiotics and ARGs in global estuarine and coastal environments are discussed. Riverine runoff, WWTPs, sewage discharge, and aquaculture, are responsible for the prevalence of antibiotics and ARGs. Geographically, pollution due to antibiotics in low- and middle-income countries is higher than that in high-income countries, and ARGs show remarkable latitudinal variations. The distribution of antibiotics is driven by antibiotic usage and environmental variables (heavy metals, nutrients, organic pollutants, etc.), while ARGs are affected by antibiotics residues, environmental variables, microbial communities, and mobile genetic elements (MGEs). Antibiotics and ARGs alter microbial communities and biogeochemical cycles, as well as pose threats to marine organisms and human health. Our results provide comprehensive insights into the transport and environmental behaviors of antibiotics and ARGs in global estuarine and coastal environments.

Technologies towards antibiotic resistance genes (ARGs) removal from aquatic environment: A critical review

Antibiotic resistance genes (ARGs) have been recognized as emerging pollutants that are widely distributed and accumulated in most of aquatic environment. Although many ARGs-removal technologies are employed, a corresponding discussion of merits and limitations of known technologies is still currently lacking. More importantly, the removal mechanisms of ARGs remain unclear, hindering their ecological feasibility. Thus, further in-depth studies are highly required. In this review, the occurrence and risk of ARGs in aquatic environment are introduced, and the main routes and potential impacts of ARGs dissemination are enumerated. In addition, several novel ARGs detection methods are critically reviewed. Notably, to ensure greater applicability of these technologies, systematic information on how recent technologies impact the ARGs removal and control are comprehensively compared and summarized. Finally, future research directions to alleviate the risk of ARGs in aquatic environment are briefly introduced. Taken together, this review provides useful information to facilitate the development of innovative and feasible ARGs removal technologies and increase their economic viability and ecological sustainability.

Interactions of microplastics and antibiotic resistance genes and their effects on the aquaculture environments

Microplastics (MPs) and antibiotic resistance genes (ARGs) have become the increasing attention and global research hotpots due to their unique ecological and environmental effects. As susceptible locations for MPs and ARGs, aquaculture environments play an important role in their enrichment and transformation. In this review, we focused on the MPs, ARGs, and the effects of their interactions on the aquaculture environments. The facts that antibiotics have been widely applied in different kinds of agricultural productions (e.g., aquaculture) and that most of antibiotics enter the water environment with rainfall and residual in the aquaculture environment have been resulting in the emergence of antibiotic resistance bacteria (ARB). Moreover, the water MPs are effective carriers of the environmental microbes and ARB, making them likely to be continuously imported into the aquaculture environments. As a result, the formation of the compound pollutions may also enter the aquatic organisms through the food chains and eventually enter the human body after a long-term enrichment. Furthermore, the compound pollutions result in the joint toxic effects on the human health and the ecological environment. In summary, this review aims to emphasize the ecological effects and the potential hazards on the aquaculture environments where interactions between MPs and ARGs results, and calls for to reduce the use of the plastic products and the antibiotics in the aquaculture environments.

Contamination, distribution, and risk assessment of antibiotics in the urban surface water of the Pearl River in Guangzhou, South China

To assess the impact of antibiotic pollution to the ecosystem in urban water, the occurrence, seasonal, and spatial distributions, potential sources, and ecological risks of 18 targeted antibiotics in urban river, Pearl River located in Guangzhou city, were investigated. Surface water samples were sampled from 24 sites in Guangzhou center of Pearl River during dry and wet seasons. The results indicated that the concentrations of antibiotic residues were at the nanogram per liter level, except sulfamethazine (SMD) (μg/L). Sulfonamides (SAs) were the dominant antibiotics, contributing 60.4-65.0% to the total antibiotics. The concentrations of SAs, fluoroquinolones (QUs), macrolides (MLs), tetracyclines (TCs), and lincosamides (LCs) were higher in dry season than those in wet season at most sampling sites, which possibly resulted from the dilution effect of heavy rainfall. The concentrations of the antibiotic residues in Guangzhou were comparable or higher than other urban rivers. The calculation on risk quotients indicated that erythromycin-H₂O (ETM-H₂O) and tetracycline (TC) were of high risks. The source identification by the Pearson correlation analysis and principal component analysis-multiple linear regression (PCA-MLR) method suggested that municipal wastewater treatment plants were primary sources of antibiotics. These results would provide important information for the environmental protect.

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.

Air pollution could drive global dissemination of antibiotic resistance genes

Antibiotic-resistant pathogens pose a significant threat to human health. Several dispersal mechanisms have been described, but transport of both microbes and antibiotic resistance genes (ARGs) via atmospheric particles has received little attention as a pathway for global dissemination. These atmospheric particles can return to the Earth's surface via rain or snowfall, and thus promote long-distance spread of ARGs. However, the diversity and abundance of ARGs in fresh snow has not been studied and their potential correlation with particulate air pollution is not well explored. Here, we characterized ARGs in 44 samples of fresh snow from major cities in China, three in North America, and one in Europe, spanning a gradient from pristine to heavily anthropogenically influenced ecosystems. High-throughput qPCR analysis of ARGs and mobile genetic elements (MGEs) provided strong indications that dissemination of ARGs in fresh snow could be exacerbated by air pollution, severely increasing the health risks of both air pollution and ARGs. We showed that snowfall did effectively spread ARGs from point sources over the Earth surface. Together our findings urge for better pollution control to reduce the risk of global dissemination of antibiotic resistance genes.

Antibiotic resistance genes in sediments of the Yangtze Estuary: From 2007 to 2019

To better understand the occurrence and succession of antibiotic resistance genes (ARGs) in the environment, the investigation of ARGs in sediment for a long time scale is urgently needed. In this study, sediment samples were taken in the Yangtze Estuarine area from 2007 to 2019, and the interannual variations in ARGs and their possible physicochemical and socioeconomic influencing factors were analyzed. The results showed that the abundance of ARGs, including sul1, sul2, tetM, tetW, aac(6')-Ib and qnrS, was higher in recent years (from 2015 to 2019) than that in earlier years (from 2007 to 2011), and heavier ARG pollution was found in Wusongkou (WSK) samples than in Liuhekou (LHK) samples. According to the redundancy discriminant analysis (RDA) and correlation analysis, the antibiotics (especially individual antibiotic categories, including oxytetracycline, doxycycline hyclate and norfloxacin), metals and a metal resistance gene (zntA) and total organic carbon (TOC) showed significant correlations to ARGs. In addition, antibiotics, metals, TOC and ARGs were also significantly correlated with several socioeconomic indices. Furthermore, the extended STIRPAT model analysis revealed that the second industry product and the first industry product were the major socioeconomic driver factors for the ARG distribution at WSK and LHK, respectively. Overall, with socioeconomic development, antibiotics, metals, TOC and ARGs increased in sediment. In addition, antibiotics, metals and TOC may participate in the regulation of the occurrence and distribution of ARGs in the Yangtze Estuary for the long time scale.

Persistence of antibiotic resistance genes from river water to tap water in the Yangtze River Delta

Antibiotic resistance genes (ARGs) raise public concern as emerging contaminants. The abundance and variation of 11 ARGs, intI1 and 16S rRNA gene were deciphered using quantitative PCR (qPCR) in two drinking water treatment systems that include river, wetland, drinking water treatment plants (DWTPs) and tap water from the Yangtze River Delta. The influencing factors for ARG abundance in river water were also explored. All investigated genes were detected in river water and there was no significant difference between the two systems, with sulfonamide ARGs occupying the highest abundance. Temperature had a significant effect on the ARG distribution based on permutational multivariate analysis of variance (PERMANOVA). Further Spearman analysis demonstrated that temperature was strongly correlated with the abundance of sul1, sul2, tetA and tetC, and these genes were significantly correlated with environmental factors (including temperature, total organic carbon (TOC) and dissolved oxygen (DO)). Considering the frequency and abundance of ARGs, as well as their correlation with other genes, sul1, sul2, tetA and tetC could be used as indicators of ARGs in river water. No significant reduction was noted for the absolute abundance of ARGs from river water to wetland water. Principle coordinates analysis (PCoA) combined with PERMANOVA revealed that drinking water treatment was responsible for reducing 16S rRNA gene and ARG abundance resulting in 3-log reductions. However, it should be noted that after transportation of distribution pipeline, both 16S rRNA gene and ARGs still detected in tap water, which indicated persistence of ARGs and will require further research.

Source tracking of antibiotic resistance genes in the environment - Challenges, progress, and prospects

Antibiotic resistance has become a global public health concern, rendering common infections untreatable. Given the widespread occurrence, increasing attention is being turned toward environmental pathways that potentially contribute to antibiotic resistance gene (ARG) dissemination outside the clinical realm. Studies during the past decade have clearly proved the increased ARG pollution trend along with gradient of anthropogenic interference, mainly through marker-ARG detection by PCR-based approaches. However, accurate source-tracking has been always confounded by various factors in previous studies, such as autochthonous ARG level, spatiotemporal variability and environmental resistome complexity, as well as inherent method limitation. The rapidly developed metagenomics profiles ARG occurrence within the sample-wide genomic context, opening a new avenue for source tracking of environmental ARG pollution. Coupling with machine-learning classification, it has been demonstrated the potential of metagenomic ARG profiles in unambiguously assigning source contribution. Through identifying indicator ARG and recovering ARG-host genomes, metagenomics-based analysis will further increase the resolution and accuracy of source tracking. In this review, challenges and progresses in source-tracking studies on environmental ARG pollution will be discussed, with specific focus on recent metagenomics-guide approaches. We propose an integrative metagenomics-based framework, in which coordinated efforts on experimental design and metagenomic analysis will assist in realizing the ultimate goal of robust source-tracking in environmental ARG pollution.

Evaluating the Potential Antibiotic Resistance Status in Environment Based on the Trait of Microbial Community

The overuse of antibiotics has promoted the propagation and dissemination of antibiotic resistance genes (ARGs) in environment. Due to the dense human population and intensive activities in coastal areas, the health risk of ARGs in coastal environment is becoming a severe problem. To date, there still lacks of a quantitative method to assess properly the gross antibiotic resistance at microbial community level. Here, we collected sediment samples from Hangzhou Bay (HB), Taizhou Bay (TB), and Xiangshan Bay (XB) of the East China Sea for community-level ARGs analysis. Based on the 16S rRNA genes and predictive metagenomics, we predicted the composition of intrinsic ARGs (piARGs) and some related functional groups. Firstly, a total of 40 piARG subtypes, belonging to nine drug classes and five resistance mechanisms, were obtained, among which the piARGs encoding multidrug efflux pumps were the most dominant in the three bays. Secondly, XB had higher relative abundances of piARGs and pathogens than the other two bays, which posed higher potential health risk and implied the heavier impact of long-term maricultural activities in this bay. Thirdly, the co-occurrence network analysis identified that there were more connections between piARGs and some potential pathogenic bacteria. Several piARG subtypes (e.g., tetA, aacA, aacC, and aadK) distributed widely in the microbial communities. And finally, the microbial diversity correlated negatively with the relative abundance of piARGs. Oil, salinity, and arsenic had significant effects on the variations of piARGs and potential pathogenic bacteria. The abundance-weighted average ribosomal RNA operon (rrn) copy number of microbial communities could be regarded as an indicator to evaluate the antibiotic resistance status. In conclusion, this study provides a new insight on how to evaluate antibiotic resistance status and their potential risk in environment based on a quantitative analysis of microbial communities.

A critical review on the occurrence of resistomes in the environment and their removal from wastewater using apposite treatment technologies: Limitations, successes and future improvement

Recent reports are pointing towards the potential increasing risks of resistomes in human host. With no permissible limit in sight, resistomes are continually multiplying at an alarming rate in the ecosystem, with a disturbing level in drinking water source. The morphology and chemical constituent of resistomes afford them to resist degradation, elude membrane and counter ionic charge, thereby, rendering both conventional and advanced water and wastewater treatment inefficient. Water and wastewater matrix may govern the propagation of individual resistomes sub-type, co-selection and specific interaction towards precise condition may have enhanced the current challenge. This review covers recent reports (2011-2019) on the occurrence of ARB/ARGs and ease of spread of resistance genes in the aquatic ecosystem. The contributions of water matrix to the spread and mitigation, treatment options, via bulk removal or capture, and intracellular and extracellular DNA lysis were discussed. A complete summary of recent occurrences of ARB/ARGs, fate after disinfection and optimum conditions of individual treatment technology or in tandem, including process limitations, with a brief assessment of removal or degradation mechanism were highlighted.

Vessel transport of antibiotic resistance genes across oceans and its implications for ballast water management

The emergence and spread of antibiotic resistance are major threats to ecosystems and human health. Transoceanic channels (e.g., ship ballast water) can transfer harmful aquatic organisms across geographically isolated waters. However, the occurrence of antibiotic resistance genes (ARGs) in ship ballast water and their relationship with microbial communities and environmental factors remain unknown. In this study, ballast water from 28 vessels sailing to Shanghai and Jiangyin (China) were collected, and the ARGs in these water samples were investigated. Considerable levels of ARGs and integrase of the class-I integrons (intI1) were detected in all ballast water samples. sul1 and tetQ were the most and least abundant ARGs in ballast water samples, respectively. The ARGs were strongly correlated with those of the 16S rRNA and intI1 genes. Ballast water exchange can reduce the absolute abundance of some kinds of ARGs while increasing the relative abundance of several ARGs (e.g., mefA, mexF, strB, sul1, and tetQ). Moreover, the bacterial hosts of ARGs were generally different in the unexchanged ballast water (UEBW) and exchanged ballast water (EBW). In particular, Leisingera and unclassified_Erythrobacteraceae were the main ARGs-associated genera in the EBW, while Pseudohongiella, Cycloclasticus, OM43_clade, norank_f_Rhodospirillaceae, and norank_f_Rhodobacteraceae were the dominant ARGs hosts in the UEBW. Overall, ship ballast water is an effective moving carrier for the global transference of ARGs, and its sufficient management is required for mitigating ARGs propagation across oceans.

Spatial and seasonal variations of antibiotic resistance genes and antibiotics in the surface waters of Poyang Lake in China

Antibiotic resistance genes (ARGs) and antibiotics in the aquatic environment raise health concerns particularly on the dispersal and persistence of antibiotic resistance. Large lakes, which serve as catch basins of anthropogenic inputs provide an ideal environment for understanding the occurrence and accumulation of ARGs and antibiotics in freshwater environments. Here, the largest freshwater lake in China, Poyang Lake, located in the developing district of Yangtze valley was used to study the characterization of the spatial and seasonal variation of both ARGs and antibiotics. Results showed that twelve tested ARGs (sul1, sul2, sul3, tetA, tetB, tetC, tetH, tetW, tetO, tetM, qnrS, and qnrB) were detected in the surface waters of Poyang Lake, with a detection frequency ranging from 19.2% to 100%, and sul2 and tetA genes were identified as potential indicators of ARG pollution in this region. Among the 11 analyzed antibiotics, sulfonamides were the predominant antibiotics with a contribution of more than 50% to the total concentrations of tested antibiotics. The total concentrations of both ARGs and antibiotics were higher in the dry season than those in the wet season. Furthermore, ARGs and antibiotics in the surface waters also varied with sampling locations, being consistently at riverine tributaries. Positive correlations were also observed between the concentrations of ARGs and antibiotics, as well as the integron gene (intI1), indicating that antibiotics and intI1 may be playing important roles in the occurrence and dispersal of ARGs in the surface waters. Lastly, our results suggest that intensive anthropogenic activities related to antibiotic usage have substantially contributed to the occurrence and persistence of ARGs and antibiotics in Poyang Lake.

Continental-scale spatio-temporal distribution of antibiotic resistance genes in coastal waters along coastline of China

Antibiotic resistance genes (ARGs) have been frequently detected in various matrices all over the world to attract wide attention due to the potential risks. Rare information is available on the pollution of ARGs in the waters of critical ecologically fragile regions such as the coastal zone at a continental scale. Therefore, this study performed field sampling during winter and summer along 18000 km coastline of China to investigate the distribution of target ARGs in coastal waters at a continental scale. The absolute abundances of ARGs in coastal waters showed drastic spatio-temporal variation with a mean value of 8.79 × 10⁴/1.39 × 10⁵ copies/mL in summer/winter, much lower than those in tail water from the maricultural zone or wastewater. The average absolute abundance of class 1 integron-integrase gene (intI1) in coastal waters was 9.68 × 10³/4.15 × 10⁴ copies/mL in summer/winter, still lower than that in tail water or wastewater. Quinolone resistance genes were the dominant ARGs in coastal waters to account for over 50% of total ARGs in most of sampling sites. Bacterial communities in coastal waters showed significant difference both at phylum and genus levels. Abundances of ARGs in coastal waters of this study were comparable with those in other regions previously reported. Tail water and wastewater might be the essential sources of ARGs in coastal waters. The findings of this study provided comprehensive information on the pollution status of ARGs in coastal waters at a continental scale, indicating that ARGs pollution has become a crucial stress affecting the sustainable development of coastal regions.

Concerted Efforts Are Needed to Control and Mitigate Antibiotic Pollution in Coastal Waters of China

Antibiotics have been applied for decades and antibiotic pollution is of great concern due to the risk for promoting resistant genes. Human activities such as mariculture and land-based discharge can lead to the antibiotic pollution in coastal area and it is of importance to assess the pollution and risks of antibiotics in this area. In this mini-review, the pollution status of antibiotics in Chinese coastal waters is summarized and some perspectives are put forward for future efforts to mitigate the pollution.

Wastewater discharge drives ARGs spread in the coastal area: A case study in Hangzhou Bay, China

The distribution of 14 ARGs, intI1, and 16S rDNA were analysed in 4 wastewater treatment plants (WWTPs), 2 effluent receiving areas (ERAs), and Hangzhou Bay (HZB). The results showed that each integrated WWTP (IWWTP) received higher abundance of ARGs than pharmaceutical WWTPs (PWWTPs), and IWWTPs removed ARGs more efficiently than PWWTPs. The WWTP effluents greatly contributed to the ARGs pollution in the water environments of the ERAs and HZB, and the total abundance of the ARGs displayed a distance decay pattern. In coastal sediments, more ARGs were accumulated in remote sites. The correlation analysis showed that the occurrence of ARGs was more related to 16S rDNA and intI1 in the WWTPs. Three macrolides resistance genes (ermB, mphA, and vatB) had strong correlations with 16S rDNA and intI1 in all the sample groups. Our study clearly reveals the link between land WWTPs discharge and emerging pollution of ARGs in coastal environments.

Biogeochemical characteristics and ecological risk assessment of pharmaceutically active compounds (PhACs) in the surface seawaters of Jiaozhou Bay, North China

The occurrence and distribution of 168 pharmaceutically active compounds (PhACs) in the surface seawater of Jiaozhou Bay (JZB) were investigated using ultra-high-performance liquid chromatography in tandem with a triple-quadrupole mass spectrometer equipped with an electrospray ionization source (UHPLC-ESI-MS-MS). Thirty-six compounds were detected, and 17 of these compounds were first detected in seawater, including sulfabenzamide, sulphacetamide, cephalonium, desacetyl-cefotaxime, cefminox, cefotaxime, cephradine, cefazolin, carprofen, nabumetone, glibenclamide, glimepiride, glipizide, prednisone, fluoromethalone, diazepam and amantadine. The total concentration of PhACs in the surface seawater ranged from 23.6 ng/L to 217 ng/L. The compounds found at the highest mean concentrations included amantadine (24.7 ng/L), lincomycin (8.55 ng/L), carprofen (8.30 ng/L), and tetracycline (7.48 ng/L). The PhAC concentration was higher in the inner bay than in the outside of the bay. In the inner bay, the eastern district showed higher concentrations of PhACs than the western district. Input from the Licun River may be the primary source of pollution. A statistically significant positive correlation was observed between nutrients and PhACs in seawater. Phosphate can be used to indicate the distribution of PhACs in JZB. Based on the individual risk quotient (RQ) values, lincomycin and ofloxacin posed high risks to the relevant aquatic organisms in JZB, especially in the eastern parts. Regular monitoring is required to evaluate the levels of PhACs as they are constantly released into JZB.

The occurrence of sulfonamide and quinolone resistance genes at the Fildes Peninsula in Antarctica

Antibiotic resistance pollution is globalizing. However, little quantitative data exists regarding the occurrence of antibiotic resistance genes (ARGs) in Antarctica, which is central to assessing the level of global contamination of ARGs. Soil, sediment, and animal feces were sampled from 12 sites in the Fildes Peninsula in January and February 2017. The occurrence and distribution of qnrS, sul1 and sul2 were investigated. The results showed that sul1 was the predominant ARG and that all the ARGs were detected in animal feces. The total absolute abundance of the ARGs in animal feces (5.86 × 10⁷ copies) was the highest. Strong and positive correlations between sul1 and int1 were found, indicating that int1 might play an important role in the creation and spread of ARGs. This data and the analysis are critical for filling the data gap regarding ARGs in Antarctica and for improving understanding of the globalization of antibiotic resistance pollution.

How long-term exposure of environmentally relevant antibiotics may stimulate the growth of Prorocentrum lima: A probable positive factor for red tides

Antibiotics have been widely detected in the ocean and have various impacts on the environment, while knowledge of their chronic influence on phytoplankton, especially red tide algae, is still limited. Dinoflagellates and green algae are common phytoplankton in marine ecosystems. The former is the main red tide algae, and the latter is an important primary producer. We investigated the long-term responses of two representative algae, Prorocentrum lima and Chlorella sp., to two common antibiotics (sulfamethoxazole (SMX) and norfloxacin (NFX)) at environmentally relevant levels (10 and 100 ng/L) during simulated natural conditions. The cell density and activities of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) were analyzed. The results showed that the influence of each antibiotic on Chlorella sp. was not significant (p > 0.05) during the first 10 days, but the influence of the antibiotics later began to show significant inhibition (p < 0.05) compared with the control group, especially during mixed exposure. P. lima was not inhibited, but its cell density increased. SMX had a superior stimulation effect on P. lima. The three enzymes activities of P. lima increased, and the antioxidant mechanism was not seriously impacted. However, for Chlorella sp., the activity of SOD increased while the activities of CAT and POD decreased, suggesting that this algae's antioxidant system was unbalanced due to oxidative stress. Based on our results, the growth of P. lima was different from green algae Chlorella sp. as well as other inhibited marine algae (such as diatom, golden algae) studied in previous studies. Therefore, as a typical pollutant in the ocean, antibiotics may play a positive role in the bloom of dinoflagellate red tides.

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

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

Occurrence and distribution of antibiotic resistance genes in the sediments of the East China Sea bays

The coastal area of the East China Sea has experienced rapid urbanization and industrialization in China since 1980s, resulting in severe pollution of its environments. Antibiotic resistance genes (ARGs) are regarded as a kind of emerging pollutant with potential high risk. The sediment samples were collected from Hangzhou Bay (HB), Xiangshan Bay (XB), and Taizhou Bay (TB) to investigate the spatial occurrence and distribution of 27 ARGs and class I integron-integrase gene (intI1) in the coastal area of the East China Sea. The PCR results showed the frequent presence of 11 ARGs and intI1 in the sediments of the three bays. The qPCR results further showed that sulfonamide resistance was the most prevalent ARG type and antibiotic target replacement and protection were the most important resistance mechanisms in the sediments. Regarding the subtype of ARGs, sulI, tetW, and dfrA13 were the most abundant ARGs, in which sulI was higher in TB (based on both the absolute and relative abundances) and dfrA13 was higher in HB (based on the relative abundances). The network analysis revealed that intI1 had significant correlations with tetC, sulI, sulII, and bla_PSE-1. Oil was the key connected factor, which had positive connections with sulI, sulII, and bla_PSE-1. In addition, the joint effect of heavy metals and nutrients & organic pollutants might be crucial for the fate of ARGs in the coastal sediments.