Tissue distribution, bioaccumulation characteristics and health risk of antibiotics in cultured fish from a typical aquaculture area

Spatiotemporal dynamics, bioaccumulation, and critical influencing factors of antibiotics in tilapia aquaculture: A study on source identification and environmental fate within typical farming systems

This study investigated the spatiotemporal dynamics, bioaccumulation, and critical influencing factors of antibiotics in tilapia aquaculture, focusing on source identification and environmental fate within typical farming systems. The results revealed a progressive increase in antibiotic concentrations in pond water and sediments over the cultivation period, with suspended solids and chemical oxygen demand identified as significant environmental factors influencing the distribution and dissemination of antibiotics. The aquaculture water source was the primary contributor of antibiotics in the farming system. Furthermore, the bioaccumulation factor (BAF) calculations indicated varying degrees of antibiotic enrichment in tilapia tissues, with sulfadimethoxine exhibiting the highest BAFs. Correlation analyses, redundancy analysis, and multivariate linear regression analysis provided insights into the relationship between environmental factors and antibiotics, identifying key antibiotics and influencing factors. The study highlighted the importance of managing and treating water sources to reduce the inflow of antibiotics into aquaculture systems and emphasized the need for non-antibiotic aquaculture practices to minimize the impact on the environment and public health. In conclusion, this research contributes valuable information for the development of effective management strategies and policies aimed at curbing antibiotic pollution in aquaculture environments, ensuring the sustainability of the aquaculture industry, and protecting ecosystem and consumer health.

Horizontal gene transfer plays a crucial role in the development of antibiotic resistance in an antibiotic-free shrimp farming system

Antibiotic selective pressure in aquaculture systems often results in the antibiotic resistance genes (ARGs) proliferation. Nonetheless, a paucity of data exists concerning the mechanisms of ARGs development in aquaculture systems without the influences of antibiotics. This study utilized metagenomic approaches to elucidate the dynamics and transfer mechanisms of ARGs throughout the aquaculture of Pacific white shrimp. A marked change in the resistome was observed throughout the aquaculture without antibiotics. The total ARGs relative abundance increased from 0.05 to 0.33 by day 90 of cultivation, with even higher in mixed wastewater (0.44). Both bacterial communities and mobile genetic elements play pivotal roles in the development of ARGs. Metagenome-assembled genomes showed enrichment of environmentally intrinsic ARGs on chromosomes including macB and mdtK. The plasmid-mediated horizontal transfer was recognized as a principal factor contributing to the rise of ARGs, particularly for tetG and floR, and this led to an escalation of resistance risk, peaking at a risks core of 35.43 on day 90. This study demonstrates that horizontal gene transfer plays a crucial role in ARGs development without antibiotic pressure, which can provide a theoretical foundation for controlling ARGs proliferation in aquaculture systems.

Antibiotic residue contamination in the aquatic environment, sources and associated potential health risks

Antibiotic residues are widely recognized as major pollutants in the aquatic environment on a global scale. As a significant class of pharmaceutically active compounds (PhACs), antibiotics are extensively consumed worldwide. The primary sources of these residues include hospitals, municipal sewage, household disposal, and manures from animal husbandry. These residues are frequently detected in surface and drinking waters, sewage effluents, soils, sediments, and various plant species in countries such as China, Japan, South Korea, Europe, the USA, Canada, and India. Antibiotics are used medicinally in both humans and animals, with a substantial portion excreted into the environment as metabolites in feces and urine. With the advancement of sensitive and quantitative analytical techniques, antibiotics are consistently reported in environmental matrices at concentrations ranging from nanograms per liter (ng/L) to milligrams per liter (mg/L). Agricultural soils, in particular, serve as a significant reservoir for antibiotic residues due to their strong particle adsorption capacities. Plants grown in soils irrigated with PhAC-contaminated water can uptake and accumulate these pharmaceuticals in various tissues, such as roots, leaves, and fruits, raising serious concerns regarding their consumption by humans and animals. There is an increasing need for research to understand the potential human health risks associated with the accumulation of antibiotics in the food chain. The present reviews aims to shed light on the rising environmental pharmaceutical contamination concerns, their sources in the environment, and the potential health risks as well as remediation effort. To discuss the main knowledge gaps and the future research that should be prioritized to achieve the risk assessment. We examined and summarized the available data and information on the antibiotic resistance associated with antibiotic residues in the environment. As studies have indicated that vegetables can absorb, transport, and accumulate antibiotics in edible parts when irrigated with wastewater that is either inadequately treated or untreated. These residues and their metabolites can enter the food chain, with their persistence, bioaccumulation, and toxicity contributing to drug resistance and adverse health effects in living organisms.

Occurrence, distribution and potential environmental risks of pollutants in aquaculture ponds during pond cleaning in Taihu Lake Basin, China

During the process of cleaning aquaculture ponds, the drainage contributes significantly to antibiotic pollution in the surrounding water environment. Therefore, we conducted a study on the distribution of 26 antibiotics in 57 ponds within the Taihu Lake basin. The results revealed that the detection frequency of antibiotics ranged from 1.75 % to 80.7 %, with the overall detection concentrations ranging from 3.27 to 708.72 ng/L. Among them, the detection rate of 8 antibiotics exceeded 50 %. Regarding the spatial distribution, the concentration of antibiotics was relatively high in aquaculture ponds located in the Changzhou area, with the highest concentration reaching 708.72 ng/L. This observation is likely due to the large size and intensive breeding practices in Changzhou. Fish ponds exhibited a significantly higher total antibiotic concentration of 3.27 to 445.57 ng/L compared to crab ponds (13.01 to 206.30 ng/L) and shrimp ponds (23.17 to 107.40 ng/L). Quinolones and sulfonamides were the predominant antibiotic classes found in fish ponds, accounting for 51.49 % of the total antibiotic concentration. Notably, sulfamethoxazole (SMX) and enrofloxacin (ENR) exhibited the highest antibiotic concentrations. Risk assessments demonstrated that SMX, ENR, and ofloxacin (OFX) contributed significantly to ecological risks. Furthermore, the study found that the tertiary constructed wetland treatment process achieved a remarkable removal rate of 92.44 % for antibiotics in aquaculture wastewater, while other treatment processes displayed limited effectiveness in removing antibiotics. This study addresses the knowledge gap concerning antibiotic pollution during the cleaning process of aquaculture ponds within the Taihu Lake basin.

Polyvinyl chloride microplastics in the aquatic environment enrich potential pathogenic bacteria and spread antibiotic resistance genes in the fish gut

Microplastics and antibiotics coexist in aquatic environments, especially in freshwater aquaculture areas. However, as the second largest production of polyvinyl chloride (PVC) in the world, the effects of co-exposure to microplastics particles and antibiotics on changes in antibiotic resistance gene (ARG) profiles and the microbial community structure of aquatic organism gut microorganisms are poorly understood. Therefore, in this study, carp (Cyprinus carpio) were exposed to single or combined PVC microplastic contamination and oxytetracycline (OTC) or sulfamethazine (SMZ) for 8 weeks. PVC microplastics can enrich potential pathogenic bacteria, such as Enterobacter and Acinetobacter, among intestinal microorganisms. The presence of PVC microplastics enhanced the selective enrichment and dissemination risk of ARGs. PVC microplastics combined with OTC (OPVC) treatment significantly increased the abundance of tetracycline resistance genes (1.40-fold) compared with that in the OTC exposure treatment, revealing an obvious co-selection effect. However, compared with those in the control group, the total abundance of ARGs and MGEs in the OPVC treatment groups were significantly lower, which was correlated with the reduced abundances of the potential host Enterobacter. Overall, our results emphasized the diffusion and spread of ARGs are more influenced by PVC microplastics than by antibiotics, which may lead to antibiotic resistance in aquaculture.

Cytotoxicity of pharmaceuticals and their mixtures toward scaffold-free 3D spheroid cultures of rainbow trout (Oncorhynchus mykiss) hepatocytes

Pharmaceutical residues are widely detected in surface waters all around the world, causing a range of adverse effects on environmental species, such as fish. Besides population level effects (mortality, reproduction), pharmaceutical residues can bioaccumulate in fish tissues resulting in organ-specific toxicities. In this study, we developed in vitro 3D culture models for rainbow trout (Oncorhynchus mykiss) liver cell line (RTH-149) and cryopreserved, primary rainbow trout hepatocytes (RTHEP), and compared their spheroid formation and susceptibility to toxic impacts of pharmaceuticals. The rapidly proliferating, immortalized RTH-149 cells were shown to form compact spheroids with uniform morphology in just three days, thus enabling higher throughput toxicity screening compared with the primary cells that required acclimation times of about one week. In addition, we screened the cytotoxicity of a total of fourteen clinically used human pharmaceuticals toward the 3D cultures of both RTH-149 cells (metabolically inactive) and primary RTHEP cells (metabolically active), to evaluate the impacts of the pharmaceuticals' own metabolism on their hepatotoxicity in rainbow trout in vitro. Among the test substances, the azole antifungals (clotrimazole and ketoconazole) were identified as the most cytotoxic, with hepatic metabolism indicatively amplifying their toxicity, followed by fluoxetine, levomepromazine, and sertraline, which were slightly less toxic toward the metabolically active primary cells than RTH-149 spheroids. Besides individual pharmaceuticals, the 3D cultures were challenged with mixtures of the eight most toxic substances, to evaluate if their combined mixture toxicities can be predicted based on individual substances' half-maximal effect (EC50) concentrations. As a result, the classical concentration addition approach was concluded sufficiently accurate for preliminarily informing on the approximate effect concentrations of pharmaceutical mixtures on a cellular level. However, direct read-across from human data was proven challenging and inexplicit for prediction of hepatotoxicity in fish in vitro.

A systematic review of antibiotics and antibiotic resistance genes (ARGs) in mariculture wastewater: Antibiotics removal by microalgal-bacterial symbiotic system (MBSS), ARGs characterization on the metagenomic

Antibiotic residues in mariculture wastewater seriously affect the aquatic environment. Antibiotic Resistance Genes (ARGs) produced under antibiotic stress flow through the environment and eventually enter the human body, seriously affecting human health. Microalgal-bacterial symbiotic system (MBSS) can remove antibiotics from mariculture and reduce the flow of ARGs into the environment. This review encapsulates the present scenario of mariculture wastewater, the removal mechanism of MBSS for antibiotics, and the biomolecular information under metagenomic assay. When confronted with antibiotics, there was a notable augmentation in the extracellular polymeric substances (EPS) content within MBSS, along with a concurrent elevation in the proportion of protein (PN) constituents within the EPS, which limits the entry of antibiotics into the cellular interior. Quorum sensing stimulates the microorganisms to produce biological responses (DNA synthesis - for adhesion) through signaling. Oxidative stress promotes gene expression (coupling, conjugation) to enhance horizontal gene transfer (HGT) in MBSS. The microbial community under metagenomic detection is dominated by aerobic bacteria in the bacterial-microalgal system. Compared to aerobic bacteria, anaerobic bacteria had the significant advantage of decreasing the distribution of ARGs. Overall, MBSS exhibits remarkable efficacy in mitigating the challenges posed by antibiotics and resistant genes from mariculture wastewater.

Metagenomic approach revealed the mobility and co-occurrence of antibiotic resistomes between non-intensive aquaculture environment and human

BACKGROUND

Aquaculture is an important food source worldwide. The extensive use of antibiotics in intensive large-scale farms has resulted in resistance development. Non-intensive aquaculture is another aquatic feeding model that is conducive to ecological protection and closely related to the natural environment. However, the transmission of resistomes in non-intensive aquaculture has not been well characterized. Moreover, the influence of aquaculture resistomes on human health needs to be further understood. Here, metagenomic approach was employed to identify the mobility of aquaculture resistomes and estimate the potential risks to human health.

RESULTS

The results demonstrated that antibiotic resistance genes (ARGs) were widely present in non-intensive aquaculture systems and the multidrug type was most abundant accounting for 34%. ARGs of non-intensive aquaculture environments were mainly shaped by microbial communities accounting for 51%. Seventy-seven genera and 36 mobile genetic elements (MGEs) were significantly associated with 23 ARG types (p < 0.05) according to network analysis. Six ARGs were defined as core ARGs (top 3% most abundant with occurrence frequency > 80%) which occupied 40% of ARG abundance in fish gut samples. Seventy-one ARG-carrying contigs were identified and 75% of them carried MGEs simultaneously. The qacEdelta1 and sul1 formed a stable combination and were detected simultaneously in aquaculture environments and humans. Additionally, 475 high-quality metagenomic-assembled genomes (MAGs) were recovered and 81 MAGs carried ARGs. The multidrug and bacitracin resistance genes were the most abundant ARG types carried by MAGs. Strikingly, Fusobacterium_A (opportunistic human pathogen) carrying ARGs and MGEs were identified in both the aquaculture system and human guts, which indicated the potential risks of ARG transfer.

CONCLUSIONS

The mobility and pathogenicity of aquaculture resistomes were explored by a metagenomic approach. Given the observed co-occurrence of resistomes between the aquaculture environment and human, more stringent regulation of resistomes in non-intensive aquaculture systems may be required. Video Abstract.

Unraveling the nexus: Microplastics, antibiotics, and ARGs interactions, threats and control in aquaculture - A review

In recent years, aquaculture has expanded rapidly to address food scarcity and provides high-quality aquatic products. However, this growth has led to the release of significant effluents, containing emerging contaminants like antibiotics, microplastics (MPs), and antibiotic resistance genes (ARGs). This study investigated the occurrence and interactions of these pollutants in aquaculture environment. Combined pollutants, such as MPs and coexisting adsorbents, were widespread and could include antibiotics, heavy metals, resistance genes, and pathogens. Elevated levels of chemical pollutants on MPs could lead to the emergence of resistance genes under selective pressure, facilitated by bacterial communities and horizontal gene transfer (HGT). MPs acted as vectors, transferring pollutants into the food web. Various technologies, including membrane technology, coagulation, and advanced oxidation, have been trialed for pollutants removal, each with its benefits and drawbacks. Future research should focus on ecologically friendly treatment technologies for emerging contaminants in aquaculture wastewater. This review provided insights into understanding and addressing newly developing toxins, aiming to develop integrated systems for effective aquaculture wastewater treatment.

Effects of dietary fermented Saccharomyces cerevisiae extract (Hilyses) supplementation on growth, hematology, immunity, antioxidants, and intestinal health in Nile tilapia

This study investigated the effects of dietary supplementation with the product Hilyses on growth performance, feed utilization, nutrient composition, hematological parameters, serum biochemistry, immune function, antioxidant status, and digestive enzyme activity in juvenile Nile tilapia (Oreochromis niloticus, initial body weight 4.24 ± 0.01 g). The fish were fed diets supplemented with Hilyses at concentrations of 0, 1, 2, or 3 g/kg for a period of 8 weeks. The results showed that supplementation with Hilyses at levels up to 2 g/kg diet significantly improved final body weight, weight gain, specific growth rate, feed efficiency ratio, protein efficiency ratio, apparent protein utilization, and energy utilization compared to the control diet without Hilyses. Carcass crude protein content and moisture were significantly higher in Hilyses-fed groups, while crude lipid content decreased at the 3 g/kg supplementation level. Hilyses supplementation enhanced various hematological parameters, including increased red blood cell count, total leukocyte count, hemoglobin concentration, hematocrit, and mean corpuscular volume. Serum biochemistry and immune function markers like total protein, albumin, complement component C3, IgM, and IgG were significantly elevated in the 2 and 3 g/kg Hilyses groups. Antioxidant enzyme activities (catalase, glutathione peroxidase, total superoxide dismutase) were enhanced, and lipid peroxidation was reduced, in the 2 g/kg Hilyses group. Digestive enzyme activities, particularly protease and lipase, were also improved with Hilyses supplementation. Histological examination showed reduced lipid deposition in the liver and increased branching of intestinal villi at the 2 g/kg Hilyses level. Overall, these results indicated that dietary Hilyses supplementation at 2 g/kg diet optimizes growth, feed utilization, nutrient composition, hematology, immunity, antioxidant status, and digestive function in juvenile Nile tilapia.

Source apportionment and predictable driving factors contribute to antibiotics profiles in Changshou Lake of the Three Gorges Reservoir area, China

Lakes, crucial antibiotic reservoirs, lack thorough exploration of quantitative relationships between antibiotics and influencing factors. Here, we conducted a comprehensive year-long investigation in Changshou Lake within the Three Gorges Reservoir area, China. The concentrations of 21 antibiotics spanned 35.6-200 ng/L, 50.3-348 ng/L and 0.57-57.9 ng/g in surface water, overlying water and sediment, respectively. Compared with abundant water period, surface water and overlying water displayed significantly high antibiotic concentrations in flat and low water periods, while sediment remained unchanged. Moreover, tetracyclines, fluoroquinolones and erythromycin posed notable risks to algae. Six primary sources were identified using positive matrix factorization model, with aquaculture contributing 21.2%, 22.7% and 25.4% in surface water, overlying water and sediment, respectively. The crucial predictors were screened through machine learning, redundancy analysis and Mantel test. Our findings emphasized the pivotal roles of water quality parameters, including water temperature (WT), pH, dissolved oxygen, electrical conductivity, inorganic anions (NO3⁻, Cl⁻ and F⁻) and metal cations (Ca, Mg, Fe, K and Cr), with WT influencing greatest. Total nitrogen (TN), cation exchange capacity, K, Al and Cd significantly impacted sediment antibiotics, with TN having the most pronounced effect. This study can promise valuable insights for environmental planning and policies addressing antibiotic pollution.

Morinda citrifolia fruit extract enhances the resistance of Penaeus vannamei to Vibrio parahaemolyticus infection

Vibrio parahaemolyticus is a gram-negative facultative anaerobic bacterium implicated as the causative agent of several shrimp diseases. As part of the effort to provide biocontrol and cost-effective treatments, this research was designed to elucidate the effect of Morinda citrifolia fruit extract on the immunity of Penaeus vannamei postlarvae (PL) to V. parahaemolyticus. The methanol extract of M. citrifolia was vacuum evaporated, and the bioactive compounds were detected using gas chromatography‒mass spectrometry (GC‒MS). Thereafter, P. vannamei PL diets were supplemented with M. citrifolia at different concentrations (0, 10, 20, 30, 40, and 50 mg/g) and administered for 30 days before 24 h of exposure to the bacterium V. parahaemolyticus. A total of 45 bioactive compounds were detected in the methanol extract of M. citrifolia, with cyclononasiloxane and octadecamethyl being the most abundant. The survival of P. vannamei PLs fed the extract supplement was better than that of the control group (7.1-26.7% survival greater than that of the control group) following V. parahaemolyticus infection. Shrimp fed 50 mg/g M. citrifolia had the highest recorded survival. The activities of digestive and antioxidant enzymes as well as hepatopancreatic cells were significantly reduced, except for those of lipase and hepatopancreatic E-cells, which increased following challenge with V. parahaemolyticus. Histological assessment of the hepatopancreas cells revealed reduced cell degeneration following the administration of the plant extracts (expecially those fed 50 mg/g M. citrifolia) compared to that in the control group. Therefore, the enhanced immunity against V. parahaemolyticus infection in P. vannamei could be associated with the improved hepatopancreas health associated with M. citrifolia fruit extract supplementation.

New insight into the bioaccumulation and trophic transfer of free and conjugated antibiotics in an estuarine food web based on multimedia fate and model simulation

The substantial utilization of antibiotics causes their "pseudo-persistence" in offshore environments. Published studies on antibiotic surveillance in food webs have primarily emphasized on parent forms; however, the compositions and concentrations of conjugated antibiotics in aquatic organisms remain largely unexplored. This study systematically examined the distribution characteristics and trophodynamics of free antibiotics and their conjugated forms in an estuarine food web. Total antibiotic levels differed insignificantly between the surface and bottom waters. The total mean values of free antibiotics in crabs, fish, shrimps, sea cucumbers, and snails varied from 0.77 to 1.4 ng/g (wet weight). The numbers and values of antibiotics rose in these biological samples after enzymatic hydrolysis. Conjugated antibiotics accounted for 23.8-76.9% of the total antibiotics in the biological samples, revealing that conjugated forms play a non-negligible role in aquatic organisms. More number of antibiotics exhibited bioaccumulation capabilities after enzymatic hydrolysis. In the food web, the free forms of anhydroerythromycin and conjugated forms of trimethoprim and ciprofloxacin underwent trophic dilution, whereas the free forms of trimethoprim and conjugated forms of ofloxacin underwent trophic amplification. The present work provides new insights into the bioaccumulation and trophic transfer of free and conjugated antibiotics in food webs.

Cross-contamination and ecological risk assessment of antibiotics between rivers and surrounding open aquaculture ponds

Antibiotics are causing widespread concern as one of the emerging contaminants. There is the abuse of antibiotics in high-density open aquaculture, and the tailwater is often discharged into surrounding rivers. At the same time, the water replenishment of open aquaculture ponds from nearby rivers containing antibiotic contamination from different sources may result in cross-contamination. However, it is still unclear which pollution intensity is greater in rivers or in open aquaculture. So in this paper, the levels of 20 antibiotics (i.e., Fluoroquinolones (FQs), Sulfonamides (SAs), Tetracyclines (TCs), Macrolides (MLs) and Lincosamides (LCs)) in rivers and high-density open aquaculture ponds were investigated in the Baini River basin in the suburbs of Guangzhou, China. The results showed that norfloxacin (NFX) was the predominant antibiotic in river and aquaculture water, with concentrations ranging from 6.12 to 156.04 ng/L and from 7.47 to 82.62 ng/L in both aquatic systems, respectively. As for the pollution intensity of antibiotics, the annual pollution contribution (28.64 kg/a) of the river water supply to open aquaculture is higher than that (10.81 kg/a) of open aquaculture to the river, which means river pollution has a greater impact on aquaculture ponds. The risk quotient (RQ) showed that the ecological risk of lincomycin (LIN), erythromycin (ERY), sulfamethoxazole (SMX), norfloxacin (NFX), ciprofloxacin (CFX) and chlortetracycline (CTC) in rivers and aquaculture environments had high ecological risks from 1.21 to 1.81. Water interactions with contaminated rivers will result in a corresponding increase in the ecological risk of antibiotics in the aquaculture environment. Overall, according to the results, the risk of polluted rivers to open aquaculture cannot be ignored, and it is recommended that open aquaculture should use these water sources with caution, and that the water quality evaluation of aquaculture water should be increased with monitoring indicators for emerging contaminants such as antibiotics.

The enrofloxacin pollution control from fish to environment

Enrofloxacin (ENR) is used to prevent and treat fish diseases widely. However, its pollution is increasing public concern on human health and aquatic ecosystem safety. This review aims to find its pollution mechanisms and control way. It is found: (1) The excessive ENR administration is the main source, the sediment ENR escaping from photolysis is the secondary ENR pollution source; (2) The ENR-rich fishes were benthic lipid-rich fishes which can simultaneously absorb administration ENR and sediment ENR, the ENR bioaccumulation is positively related to the fish habitats ENR level and fish lipids content; (3) The ENR t1/2 varies with fish age, body weight, feedstuff lipids and crude fiber level, temperature, salinity, administration mode and dose; Consequently, the first control way is to conduct the minimum inhibitory concentration ENR, combining herbal medicines with antibacterial and detoxification functions. The second way is to develop the enrichment and removal techniques for sediment ENR.

Multimodal Model to Predict Tissue-to-Blood Partition Coefficients of Chemicals in Mammals and Fish

Tissue-to-blood partition coefficients (Ptb) are key parameters for assessing toxicokinetics of xenobiotics in organisms, yet their experimental data were lacking. Experimental methods for measuring Ptb values are inefficient, underscoring the urgent need for prediction models. However, most existing models failed to fully exploit Ptb data from diverse sources, and their applicability domain (AD) was limited. The current study developed a multimodal model capable of processing and integrating textual (categorical features) and numerical information (molecular descriptors/fingerprints) to simultaneously predict Ptb values across various species, tissues, blood matrices, and measurement methods. Artificial neural network algorithms with embedding layers were used for the multimodal modeling. The corresponding unimodal models were developed for comparison. Results showed that the multimodal model outperformed unimodal models. To enhance the reliability of the model, a method considering categorical features, weighted molecular similarity density, and weighted inconsistency in molecular activities of structure-activity landscapes was used to characterize the AD. The model constrained by the AD exhibited better prediction accuracy for the validation set, with the determination coefficient, root mean-square error, and mean absolute error being 0.843, 0.276, and 0.213 log units, respectively. The multimodal model coupled with the AD characterization can serve as an efficient tool for internal exposure assessment of chemicals.

Maternal or Paternal Antibiotics? Intergenerational Transmission and Reproductive Toxicity in Zebrafish

Despite the known direct toxicity of various antibiotics to aquatic organisms, the potential chronic impact through intergenerational transmission on reproduction remains elusive. Here, we exposed zebrafish to a mixture of 15 commonly consumed antibiotics at environmentally relevant concentrations (1 and 100 μg L-1) with a cross-mating design. A high accumulation of antibiotics was detected in the ovary (up to 904.58 ng g-1) and testis (up to 1704.49 ng g-1) of F0 fish. The transmission of antibiotics from the F0 generation to the subsequent generation (F1 offspring) was confirmed with a transmission rate (ki) ranging from 0.11 to 2.32. The maternal transfer of antibiotics was significantly higher, relative to paternal transfer, due to a greater role of transmission through ovarian enrichment and oviposition compared to testis enrichment. There were similar impairments in reproductive and developmental indexes on F1 eggs found following both female and male parental exposure. Almost all antibiotics were eliminated in F2 eggs in comparison to F1 eggs. However, there were still reproductive and developmental toxic responses observed in F2 fish, suggesting that antibiotic concentration levels were not the only criterion for evaluating the toxic effects for each generation. These findings unveil the intergenerational transmission mechanism of antibiotics in fish models and underscore their potential and lasting impact in aquatic environments.

Multi-task machine learning models for simultaneous prediction of tissue-to-blood partition coefficients of chemicals in mammals

Tissue-to-blood partition coefficients (Ptb) are crucial for assessing the distribution of chemicals in organisms. Given the lack of experimental data and laborious nature of experimental methods, there is an urgent need to develop efficient predictive models. With the help of machine learning algorithms, i,e., random forest (RF), and artificial neural network (ANN), this study developed multi-task (MT) models that can simultaneously predict Ptb values for various mammalian tissues, including liver, muscle, brain, lung, and adipose. Single-task (ST) models using partial least squares regression, RF, and ANN algorithms for each endpoint were established for comparison. Overall, the performances of MT models were superior to those of ST models. The MT model using ANN algorithms showed the highest prediction accuracy with determination coefficients ranging from 0.704 to 0.886, root mean square errors between 0.223 and 0.410, and mean absolute errors ranging from 0.178 to 0.285 log units. Results showed that lipophilicity and polarizability of molecules significantly influence their partition behavior in organisms. Applicability domains (ADs) of the models were characterized by weighted molecular similarity density, and weighted inconsistency in molecular activities of structure-activity landscapes. When constrained by ADs, the models displayed enhanced predictive accuracy, making them valuable tools for the risk assessment and management of chemicals.

An update on the prevalence of colistin and carbapenem-resistant Gram-negative bacteria in aquaculture: an emerging threat to public health

Aquaculture has been recognized as a hotspot for the emergence and spread of antimicrobial resistance genes conferring resistance to clinically important antibiotics. This review gives insights into studies investigating the prevalence of colistin and carbapenem resistance (CCR) among Gram-negative bacilli in aquaculture. Overall, a high incidence of CCR has been reported in aquatic farms in several countries, with CCR being more prevalent among opportunistic human pathogens such as Acinetobacter nosocomialis, Shewanella algae, Photobacterium damselae, Vibrio spp., Aeromonas spp., as well as members of Enterobacteriaceae family. A high proportion of isolates in these studies exhibited wide-spectrum profiles of antimicrobial resistance, highlighting their multidrug-resistance properties (MDR). Several mobile colistin resistance genes (including, mcr-1, mcr-1.1, mcr-2, mcr-2.1, mcr-3, mcr-3.1, mcr-4.1, mcr-4.3, mcr-5.1, mcr-6.1, mcr-7.1, mcr-8.1, and mcr-10.1) and carbapenemase encoding genes (including, blaOXA-48, blaOXA-55, blaNDM, blaKPC, blaIMI, blaAIM, blaVIM, and blaIMP) have been detected in aquatic farms in different countries. The majority of these were carried on MDR Incompatibility (Inc) plasmids including IncA/C, and IncX4, which have been associated with a wide host range of different sources. Thus, there is a risk for the possible spread of resistance genes between fish, their environments, and humans. These findings highlight the need to monitor and regulate the usage of antimicrobials in aquaculture. A multisectoral and transdisciplinary (One Health) approach is urgently needed to reduce the spread of resistant bacteria and/or resistance genes originating in aquaculture and avoid their global reach.

Comprehensive assessment of occurrence, temporal-spatial variations, and ecological risks of heavy metals in Jiaozhou Bay, China: A comprehensive study

Heavy metals play a significant role in marine ecosystems, exerting notable impacts on the environment and human health. In this study, water, sediment, and aquatic organism samples from Jiaozhou Bay were investigated to comprehensively assess the distribution, temporal-spatial variations, and ecological risks of heavy metals. The results indicate that pollution from industrial wastewater discharge contributes to regional differences in the distribution of heavy metals, possibly being a major source of Zn, Cr, Cd, and Hg (r > 0.7, p < 0.05). Biological and physicochemical processes influence the distribution of Zn, Cr, and Pb in the water and sediment. Hg exhibits a polluted state in both the water and sediment, with As and Hg being the two highest-risk heavy metals in water and sediment, respectively. Among the organisms, crustaceans show significantly higher levels of heavy metal content and accumulation compared to mollusks and fish (p < 0.05), and the bioamplification of heavy metals occurs in the sediment-Rapana venosa-Portunus trituberculatus biological pathway. Portunus trituberculatus, Charybdis japonica, Oratosquilla oratoria, and Octopus ocellatus could pose risks to human health, especially for children and vulnerable populations. This study aims to enhance our understanding of the current status of heavy metal pollution in Jiaozhou Bay and to provide a scientific basis and favorable support for the ecological environmental protection and prevention of ecological risks associated with heavy metal pollution in Jiaozhou Bay and other bays in China.

Occurrence, Distribution, and Trophic Transfer of Pharmaceuticals and Personal Care Products in the Bohai Sea

The ubiquitous presence of pharmaceuticals and personal care products (PPCPs) in environments has aroused global concerns; however, minimal information is available regarding their multimedia distribution, bioaccumulation, and trophic transfer in marine environments. Herein, we analyzed 77 representative PPCPs in samples of surface and bottom seawater, surface sediments, and benthic biota from the Bohai Sea. PPCPs were pervasively detected in seawater, sediments, and benthic biota, with antioxidants being the most abundant PPCPs. PPCP concentrations positively correlated between the surface and bottom water with a decreasing trend from the coast to the central oceans. Higher PPCP concentrations in sediment were found in the Yellow River estuary, and the variations in the physicochemical properties of PPCPs and sediment produced a different distribution pattern of PPCPs in sediment from seawater. The log Dow, but not log Kow, showed a linear and positive relationship with bioaccumulation and trophic magnification factors and a parabolic relationship with biota-sediment accumulation factors. The trophodynamics of miconazole and acetophenone are reported for the first time. This study provides novel insights into the multimedia distribution and biomagnification potential of PPCPs and suggests that log Dow is a better indicator of their bioaccumulation and trophic magnification.

Health Risk Assessment of Antibiotic Pollutants in Large Yellow Croakers from Zhejiang Aquaculture Sites

Intensive aquaculture combatting the decline of large yellow croaker populations can trigger bacterial outbreaks, resulting in extensive antibiotic use. In this study, we screened 5 aquaculture sites in the coastal areas of Zhejiang and identified 17 antibiotics in large yellow croakers using UPLC-MS/MS. The distribution and occurrence of antibiotic pollutants were different in the different tissues of large yellow croakers, being primarily dominated by quinolones. Relatively higher average residue levels of enrofloxacin and ciprofloxacin were detected in the inedible parts, specifically the gills (37.29 μg/kg). Meanwhile, relatively high average residue levels of enrofloxacin and ciprofloxacin were also found in the edible parts, particularly in the muscle (23.18 μg/kg). We observed that the residue levels detected in the swim bladder exceeded the prescribed limit for fish muscle, but there is currently no specific regulatory limit established for this particular tissue. Despite the HI values of enrofloxacin and ciprofloxacin being below 0.01, the health risks should not be disregarded. The findings of this research provide significant practical implications for assessing antibiotic contamination and enhancing the risk management of coastal regions.

pH-Driven Efficacy of the Ferrate(VI)-Peracetic Acid System in Swift Sulfonamide Antibiotic Degradation: A Deep Dive into Active Species Evolution and Mechanistic Insights

In the realm of wastewater treatment, the power of ferrate (Fe(VI)) and peracetic acid (PAA) as oxidants stands out. But their combined might is where the enhancement truly lies. Their collaborative effect intensifies, but the underlying mechanics, especially across varying pH levels and pollutant types, still lurks in obscurity. Our study delved into the sophisticated oxidation interplay among Fe(VI)-PAA, Fe(VI)-H2O2, and standalone Fe(VI) systems. Notably, at a pH of 9.0, boasting a kinetic constant of ∼0.127 M-1·s-1, the Fe(VI)-PAA system annihilated the pollutant sulfamethoxazole, outpacing its counterparts by a staggering 48.73-fold when compared to the Fe(VI)-H2O2 system and 105.58-fold when using Fe(VI) individually. The behavior of active species─such as the dynamic •OH radicals and high-valent iron species (Fe(IV)/Fe(V))─shifted with pH variations, leading to distinct degradation pathways. Our detailed exploration pinpoints the behaviors of certain species across pH levels from 3.0 to 9.0. In more acidic environments, the •OH species proved indispensable for the system's reactivity. Conversely, as the pH inclined, degradation was increasingly steered by high-valent iron species. This intensive probe demystifies Fe(VI) interactions, deepening our understanding of the capabilities of the Fe(VI)-centered system and guiding us toward cleaner water solutions. Importantly, pH value, often underappreciated, holds the reins in organic wastewater decontamination. Embracing this key player is vital as we strategize for more expansive systems in upcoming ventures.

Distribution, removal and ecological risk assessment of antibiotics in leachate from municipal solid waste incineration plants in Shanghai, China

Leachate from Municipal Solid Waste (MSW) incineration plants contains multiple antibiotics. However, current knowledge of antibiotics in such leachate is very limited compared to landfill leachate. In this study, the distribution, removal and ecological risks of 8 sulfonamides (SAs), 4 quinolones (FQs), and 4 macrolides (MLs) antibiotics in leachate from three MSW incineration plants in Shanghai were investigated. The results showed that 12 types of target antibiotics were detected at high concentrations (7737.3-13,758.7 ng/L) in the fresh leachate, exceeding the concentrations reported for landfill leachate. FQs were the dominant antibiotics detected in all three fresh leachates, accounting for >60 % of the total detected concentrations. The typical "anaerobic-anoxic/aerobic-anoxic/aerobic-ultrafiltration" treatment process removed the target antibiotics effectively (89.0 %-93.4 %), of which the anaerobic unit and the primary anoxic/aerobic unit were the most important antibiotic removal units. Biodegradation was considered to be the dominant removal mechanism, removing 78.11 %-92.37 % of antibiotics, whereas sludge adsorption only removed 1.02 %-10.89 %. Antibiotic removal was significantly correlated with leachate COD, pH, TN, and NH3-N, indicating that they may be influential factors for antibiotic removal. Ecological risk assessment revealed that ofloxacin (OFX) and enrofloxacin (EFX) in the treated leachate still posed high risks to algae and crustaceans. This research provides insights into the fate of antibiotics in leachate.

The neurobehavioral impacts of typical antibiotics toward zebrafish larvae

Due to the widely usage in livestock, aquaculture and clinics, antibiotic residues are existed in aqueous environments and their potential toxicity to aquatic organisms is concerning. Here, we used zebrafish as the model to investigate the neurotoxicity and involved mechanism of seven antibiotics that were frequently detected in surface waters. The results revealed that the short-term exposure to clarithromycin (CLA), chlortetracycline (CTC) and roxithromycin (ROX) induced behavioral effects, with effective concentration of 1 μg/L (CTC and ROX) and 100 μg/L (CLA, CTC and ROX) respectively. A significant decrease in the travel distance and velocity as well as an increase in turn angle was measured. TUNEL assay identified increased cell apoptosis in brain sections of larvae exposed to three neurotoxic antibiotics, which raised the possibility that the behavioral symptoms were associated with neural damage. Transcriptome sequencing showed that the three antibiotics could affect the nervous system of zebrafish including the alteration of synaptogenesis and neurotransmission. Additionally, ROX and CTC affected pathways involved in mitochondrial stress response and endocrine system in zebrafish larvae. Besides, BDNF, ASCL1, and CREBBP are potential upstream regulatory factors that mediated these impacts. These findings indicated that exposure of CTC, ROX and CLA may cause abnormal behavior toward zebrafish larvae under environmental relevant concentration and revealed the potential role of neural cell apoptosis and synaptogenesis signaling in mediating this effect.

Preconception exposure to environmental antibiotics among childbearing couples in Anhui and health risk assessment: A multicenter population-based representative study

Only few studies have assessed the health effects due to preconception exposure to antibiotics among childbearing couples. This study investigated the status of preconception exposure to antibiotics among childbearing couples in Anhui, associated with health risks, and influencing factors. Overall, 1500 childbearing couples were randomly selected from the Reproductive Health of Childbearing Couples - Anhui Cohort (RHCC-AC). The urinary levels of 40 antibiotics and 2 metabolites were determined, and specific gravity (SG) adjusted concentrations of antibiotics were measured to assess health risks. Generalized linear models were used to assess the associations of urinary SG-adjusted concentration of antibiotics with demographic parameters and diet frequency. The total detection rates of all antibiotics were 98.9 % and 99.3 % in wives and husbands, respectively. The detection rates of veterinary antibiotics (VAs) and preferred as VAs (PVAs) were above 90 %. Among eight antibiotics, sulfonamides (95.1 %) and fluoroquinolones (87.6 %) had the highest detection rates in couples. Approximately four-fifths of couples were simultaneously exposed to at least three different antibiotics, and more than half of them were exposed to low concentrations of antibiotics. 8.9 % and 9.2 % of wives and husbands had hazard index value of antibiotics exposure greater than 1. Antibiotic concentrations were associated with residence, sampling season, and diet frequency. In Anhui, nearly 98 % of childbearing couples have environmental exposure to antibiotics, and VAs and PVAs are the primary antibiotics. More than 8 % of couples had health risks due to antibiotic exposure. Several potential determinants of urinary antibiotics deserve more attention in future research.

Phytoplankton Biological Pump Controls the Spatiotemporal Bioaccumulation and Trophic Transfer of Antibiotics in a Large Subtropical River

The spatiotemporal bioaccumulation, trophic transfer of antibiotics, and regulation of the phytoplankton biological pump were quantitatively evaluated in the Pearl River, South China. The occurrence of antibiotics in organisms indicated a significant spatiotemporal trend associated with the life cycle of phytoplankton. Higher temporal bioaccumulation factors (BAFs) were found in phytoplankton at the bloom site, while lower BAFs of antibiotics in organisms could not be explained by phytoplankton biomass dilution but were attributed to the low bioavailability of antibiotics, which was highly associated with distribution coefficients (R2 = 0.480-0.595, p < 0.05). Such lower BAFs of antibiotics in phytoplankton at higher biomass sites hampered the entry of antibiotics into food webs, and trophic dilutions were subsequently observed for antibiotics except for ciprofloxacin (CFX) and sulfamerazine (SMZ) at sites with blooms in all seasons. Distribution of CFX, norfloxacin (NFX), and sulfapyridine (SPD) showed further significant positive relationships with the plasma protein fraction (R2 = 0.275-0.216, p < 0.05). Both mean BAFs and trophic magnification factors (TMFs) were significantly negatively correlated with phytoplankton biomass (R2 = 0.661-0.741, p < 0.05). This study highlights the importance of the biological pump in the regulation of spatiotemporal variations in bioaccumulation and trophic transfer of antibiotics in anthropogenic-impacted eutrophic rivers in subtropical regions.

The genome of Symbiodiniaceae-associated Stutzerimonas frequens CAM01 reveals a broad spectrum of antibiotic resistance genes indicating anthropogenic drift in the Palk Bay coral reef of south-eastern India

An increase in antibiotic pollution in reef areas will lead to the emergence of antibiotic-resistant bacteria, leading to ecological disturbances in the sensitive coral holobiont. This study provides insights into the genome of antibiotics-resistant Stutzerimonas frequens CAM01, isolated from Favites-associated Symbiodiniaceae of a near-shore polluted reef of Palk Bay, India. The draft genome contains 4.67 Mbp in size with 52 contigs. Further genome analysis revealed the presence of four antibiotic-resistant genes, namely, adeF, rsmA, APH (3")-Ib, and APH (6)-Id that provide resistance by encoding resistance-nodulation-cell division (RND) antibiotic efflux pump and aminoglycoside phosphotransferase. The isolate showed resistance against 73% of the antibiotics tested, concurrent with the predicted AMR genes. Four secondary metabolites, namely Aryl polyene, NRPS-independent-siderophore, terpenes, and ectoine were detected in the isolate, which may play a role in virulence and pathogenicity adaptation in microbes. This study provides key insights into the genome of Stutzerimonas frequens CAM01 and highlights the emergence of antibiotic-resistant bacteria in coral reef ecosystems.

Identification and Characterization of a Potential Probiotic, Clostridium butyricum G13, Isolated from the Intestine of the Mud Crab (Scylla paramamosain)

The butyrate-producing bacterium Clostridium butyricum has been proven to be important in improving the growth and health benefits of aquatic animals. In this study, C. butyricum G13 was isolated for the first time from the gut of the mud crab (Scylla paramamosain). The results of this study showed that C. butyricum G13 could produce a high concentration of butyric acid and grow well in a wide range of pHs (4 to 9) and NaCl (1 to 2.5%) and bile salt (0.2 to 1.0%) concentrations. In vitro characterization revealed that C. butyricum G13 is a Gram-positive and gamma-hemolytic bacterium sensitive to most antibiotics and shows hydrophobicity and the capacity to degrade starch. In vitro fermentation using mud crab gut contents showed that C. butyricum G13 alone or in combination with galactooligosaccharides (GOS) and/or resistant starch (RS) significantly increased butyric acid production and beneficially affected the abundance and diversity of intestinal microbiota. In addition, C. butyricum G13 can improve the survival rate of mud crabs and effectively maintain the normal structure of gut morphology after infection with Vibrio parahaemolyticus. In conclusion, C. butyricum G13 can be considered a potential probiotic that improves the immune capacity and confers health benefits on mud crabs. IMPORTANCE With the development of society, more and more aquatic animals are demanded. Intensification in the aquaculture scale is facing problems, such as disease outbreaks, eutrophication of water bodies, and misuse of antibiotics. Among these challenges, disease outbreak is the most important factor directly affecting aquaculture production. It is crucial to explore new approaches effective for the prevention and control of diseases. Probiotics have been widely used in aquaculture and have shown beneficial effects on the host. In this study, the butyrate-producing bacterium Clostridium butyricum G13 was isolated for the first time from the intestine of the mud crab through in vitro fermentation. The bacterium has probiotic properties and changes the gut microbiota to be beneficial to hosts in vitro as well as protecting hosts from Vibrio parahaemolyticus infection in vivo. The outcomes of this study indicate that C. butyricum G13 can be used as a potential probiotic in mud crab aquaculture.

A colorimetric aptasensor fabricated with group-specific split aptamers and complex nanozyme for enrofloxacin and ciprofloxacin determination

Developing simultaneous detection methods for multiple targets is crucial for the field of food analysis. Herein, enrofloxacin (ENR) and ciprofloxacin (CIP) were taken as model targets. For the first time, a strategy to generate group-specific split aptamers was established by revealing and splitting the critical binding domain, and the split aptamers were exploited to design a four-way DNA junction (4WJ) which could regulate the enzymatic activity of chitosan oligosaccharide (COS)-AuNPs nanozyme to develop a colorimetric aptasensor. A pair of split aptamers were obtained for ENR (K_d = 15.00 nM) and CIP (K_d = 4.870 nM). The mechanism of COS binding with double-stranded DNA in the 4WJ was elucidated. Under optimal conditions, the colorimetric aptasensor enabled a wide linear detection range of 1.4-1400 nM and a limit of detection (LOD) of 321.1 pM and 961.0 pM towards ENR and CIP, respectively, which exhibited excellent sensitivity, selectivity, and availability in detecting ENR/CIP in seafood. This study expands the general strategies for generating robust aptamers and nanozyme complex and provides a good reference for developing multi-target detection methods.

Repurposing chitin-rich seafood waste for warm-water fish farming

The pisciculture industry has grown multi-fold over the past few decades. However, a surge in development and nutrient demand has led to the establishment of numerous challenges. Being a potential solution, chitosan has gained attention as a bio nanocomposite for its well-acclaimed properties including biodegradability, non-toxicity, immunomodulatory effects, antimicrobial activity, and biocompatibility. This biopolymer and its derivatives can be transformed into various structures, like micro and nanoparticles, for various purposes. Consequently, with regards to these properties chitin and its derivatives extend their application into drug delivery, food supplementation, vaccination, and preservation. This review focuses on the clinical advancements made in fish biotechnology via chitosan and its derivatives and highlights its prospective expansion into the pisciculture industry-in particular, warm-water species.

Assessment of the benefits of essential fatty acids and risks associated with antimicrobial residues in aquatic products: A case study of Chinese mitten crab (Eriocheir sinensis)

Much attention has been given to the safety and quality of aquatic products, including consuming Chinese mitten crab (Eriocheir sinensis), which offers both nutritional benefits and toxicological risks. Eighteen sulfonamides, 9 quinolones and 37 fatty acids were analyzed in 92 crab samples from primary aquaculture provinces in China. Enrofloxacin and ciprofloxacin have been mentioned as typical antimicrobials occurring at the greatest concentrations (>100 μg/kg, wm). By use of an in vitro method, the proportions of enrofloxacin, ciprofloxacin and essential fatty acids (EFAs, DHA and EPA) in ingested nutrients were determined to be 12 %, none and 95 %, respectively. The risk-benefit quotient (HQ) between the adverse effects of antimicrobials and nutritional benefits of EFAs in crabs found that HQs based on data after digestion were significantly less (HQ = 0.0086) than that of the control group where no digestion occurred (HQ = 0.055). This result suggested that (1) there was less risk posed by antimicrobials due to the consumption of crab, and (2) ignoring the bioaccessible fraction of antimicrobials in crabs might overestimate risks to the health of humans due to dietary exposure. Meaning bioaccessibility can improve the accuracy of the risk assessment process. Realistic risk evaluation should be recommended to achieve a quantified assessment of the dietary risks and benefits of aquatic products.

Study effect and mechanism of levofloxacin on the neurotoxicity of Rana nigromaculata tadpoles exposed to imidacloprid based on the microbe-gut-brain axis

Aquatic organisms may be simultaneously exposed to antibiotics and pesticides. After levofloxacin (LVFX), imidacloprid (IMI) exposure and co-exposure at environmental levels, we found LVFX and IMI had antagonistic effect on the neurotoxicity of tadpoles. IMI-induced neurotoxicity on tadpoles can be explained by oxidative stress and hormone levels in some degree. By regulating ornithine, l-asparagine, putrescine and tryptamine in the intestine, LVFX affected glutathione metabolism, arginine and proline metabolism, alanine, aspartate and glutamate metabolism, tyrosine metabolism and aminoacyl tRNA biosynthesis, so then eased the neurotoxicity caused by IMI. More interestingly, Fusobacteriota and Cetobacterium might play an important role on easing the neurotoxicity caused by IMI. In addition, LVFX might have a laxation effect on the increased relative abundance of Bacteroidota caused by IMI. In conclusion, IMI not only affected oxidative stress and hormone levels in the brain, but also affected the synthesis of neurotransmitters in the intestine by regulating intestinal microbiota. In LVFX and IMI co-exposed groups, LVFX alleviated the neurotoxicity caused by IMI through regulating the intestinal microbiota, showing as an antagonistic effect. Our results provided a new perspective for aquatic ecological risk assessment under co-exposure of antibiotics and pesticides.

Occurrence, distribution and risk assessment of antibiotics at various aquaculture stages in typical aquaculture areas surrounding the Yellow Sea

The pollution of antibiotics commonly existed throughout the entire aquaculture process, but the residues of antibiotics at different aquaculture stages have rarely been studied. This study investigated the occurrence, distribution and risk assessment of antibiotics at different aquaculture stages (the non-aquaculture stage, the early aquaculture stage, the middle aquaculture stage, and the late aquaculture stage) in two typical marine aquaculture areas (Mahegang River and Dingzi Bay) surrounding the Yellow Sea. Fluoroquinolones and tetracyclines were commonly used antibiotics in the aquaculture of these areas with high detection frequencies (17% to 83%). Compared among four aquaculture stages, the highest concentration of antibiotics (9032.08 ng/L) in aquaculture ponds was detected at the late aquaculture stage. And the antibiotic pollution level of natural water was directly related to the aquaculture stages. Similarly, at the aquaculture stages, the detection frequency of antibiotics in sediments was higher than that at the non-aquaculture stage. Based on the correlation analysis, the concentration of main antibiotics in water showed a positive correlation with total nitrogen (p<0.05) and chlorophyll a (p<0.01), while it showed a negative correlation with salinity (p<0.01) in coastal water of the Dingzi Bay. According to the risk assessment, with the development of aquaculture stages, the selection pressure of fluoroquinolones and tetracyclines on resistant bacteria had increased. And the ecological risks caused by sulfonamides and tetracyclines to aquatic organisms had also increased markedly. Overall, this study may provide a reference for formulating regulatory policies regarding antibiotic use at different aquaculture stages.

Occurrence and risk assessment of antibiotics in feces of elderly individuals in Shenzhen

The occurrence of antibiotics in the feces of elderly individuals in Shenzhen, China, was investigated by monitoring 78 compounds to understand the adverse effects and its association with antibiotic residues in animal products collected from local markets. In total, 18 compounds belonging to 5 classes of antibiotics were identified in 74 of 140 fecal samples. Furthermore, 17.9% of the fecal samples contained at least two antibiotics, and 14.3% of the samples showed antibiotic concentrations higher than 100 μg/kg. Cephalothin exhibited the highest detection frequency (22.1%), followed by azithromycin (15.7%) and tilmicosin (12.9%). Oxytetracycline, norfloxacin, and azithromycin showed extremely high concentrations (> 1000 μg/kg). Eight antibiotics were detected in the animal products, with detection frequencies ranging from 4.8 to 40.0%. Five antibiotics exhibited similar detection frequencies and strong correlations between the human fecal and animal product samples. Health risk assessment based on hazard quotients showed that ciprofloxacin in animal products and human feces posed a medium and high risk, respectively. The hazard quotients of oxytetracycline, norfloxacin, and azithromycin in the feces were greater than 1, indicating a high health risk. These findings suggest that the elderly individuals were frequently exposed to antibiotics via the food chain and faced health risks posed by these antibiotics.

Salvinia molesta phytoremediation capacity as a nature-based solution to prevent harmful effects and accumulation of ciprofloxacin in Neotropical catfish

Phytoremediation has been a potential solution for the removal of pharmaceuticals from water. Here, we evaluated the toxicological safety of ciprofloxacin-contaminated water treated by 96 h with Salvinia molesta. The Neotropical catfish Rhamdia quelen was used as a model, and the potential of the phytoremediation technique for mitigating the drug accumulation in the fishes was also studied. Fish exposed to Cipro (1 and 10 µg·L^-1) in untreated water showed toxic responses (alteration of hematological, genotoxicity, biochemical, and histopathological biomarkers) and accumulated Cipro in their muscles at concentrations high for human consumption (target hazardous quotient > 1). Fish exposed to water treated with S. molesta showed no toxic effect and no accumulation of Cipro in their tissues. This must be related to the fact that S. molesta removed up to 97% of Cipro from the water. The decrease in Cipro concentrations after water treatment with S. molesta not only prevented the toxic effects of Cipro on R. quelen fish but also prevented the antimicrobial accumulation in fish flesh, favouring safe consumption by humans. For the very first time, we showed the potential of phytoremediation as an efficiently nature-based solution to prevent environmental toxicological effects of antimicrobials to nontarget organisms such as fish and humans. The use of S. molesta for Cipro-removal from water is a green technology to be considered in the combat against antimicrobial resistance.

Improved LC/MS/MS Quantification Using Dual Deuterated Isomers as the Surrogates: A Case Analysis of Enrofloxacin Residue in Aquatic Products

Extensive and high residue variations in enrofloxacin (ENR) exist in different aquatic products. A novel quantitative method for measuring ENR using high-performance liquid chromatography-tandem mass spectrometry was developed employing enrofloxacin-d₅ (ENR-d₅) and enrofloxacin-d₃ (ENR-d₃) as isotope surrogates. This reduced the deviation of detected values, which results from the overpass of the linear range and/or the large difference in the residue between the isotope standard and ENR, from the actual content. Furthermore, high residue levels of ENR can be directly diluted and re-calibrated by the corresponding curve with the addition of high levels of another internal surrogate without repeated sample preparation, avoiding the overflow of the instrument response. The validation results demonstrated that the method can simultaneously determine ENR residues from MQL (2 µg/kg) to 5000 × MQL (method quantification limit) with recoveries between 97.1 and 106%, and intra-precision of no more than 2.14%. This method realized a wide linear calibration range with dual deuterated isomers, which has not been previously reported in the literature. The developed method was successfully applied to the analysis of ENR in different aquatic products, with ENR residue levels varying from 108 to 4340 μg/kg and an interval of precision in the range of 0.175~6.72%. These results demonstrate that batch samples with a high variation in ENR residues (over the linear range with a single isotope standard) can be detected by the dual isotope surrogates method in a single sample preparation process.

Crosstalk between imbalanced gut microbiota caused by antibiotic exposure and rotavirus replication in the intestine

Objective

Rotavirus (RV), one of non-enveloped double-strained RNA viruses, can cause infantile diarrheal illness. It is widely accepted that RV is transmitted mainly via feces-oral route. However, infected asymptomatic adults are becoming the source of infection. It is necessary to explore the underlying mechanism of RV replication in adult's intestine.

Methods

After recruiting healthy volunteers and RV asymptomatic carriers, we firstly investigated the association of animal-derived food intake with antibiotic level in urine samples. Secondly, we compared the difference in the structure of gut microbiota, and identified the taxa that most likely explained the difference. Finally, we investigated the impact of lipopolysaccharide (LPS), produced by gram-negative bacteria, on RV replication in vivo and in vitro.

Results

We found that 10% of participants were RV asymptomatic carriers in our study. High intake of animal-derived food was positively correlated to antibiotic level in urine samples. The disrupted gut microbiota in RV carriers was characterized by high abundance of antibiotic resistant gram-negative bacteria and high level of LPS. The disrupted gut microbiota caused by penicillin treatment was benefit to RV replication in vivo. LPS enhanced RV thermal stability in vitro.

Conclusions

Our findings suggest that the imbalanced gut microbiota caused by antibiotic exposure plays an important role in RV replication, and brings risk to health complications.

Residual analysis of QoI fungicides in multiple (six) types of aquatic organisms by UPLC-MS/MS under acutely toxic conditions

In view of the significance of food safety and the possible relationship between residual enrichment and acute toxicity for pesticides in different aquatic organisms, it is essential to establish a sensitive and reliable determination method for pesticides in different aquatic organisms to analyze the enrichment levels. Quinone outside inhibitor fungicides (QoIs) are lipophilic fungicides that pose environmental threats to aquatic organisms. Previous research has mainly focused on QoI residues in aquatic organisms under chronic toxicity, whereas less is known about how pesticide residues differ among aquatic organism under acutely toxic conditions. In the present study, the residues of QoIs in aquatic organisms (Danio rerio, Rana pipiens, Cherax quadricarinatus, Misgurnus anguillicaudatus, Corbicula fluminea, and Ampullaria gigas) were analyzed by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) coupled with a proposed QuEChERS method. The proposed method was validated in terms of linearity (coefficients of determination of 0.9980-0.9999), the limits of quantification (0.01 μg·kg^-1), the relative standard deviation (0.6-4.4%), and recovery (70.12-118.15%). The results demonstrated that the proposed method fulfilled the requirements for pesticide analysis in all tested aquatic organisms. The residues of QoIs in the same aquatic organism exposed to QoI concentrations of 5 and 500 μg L^-1 decreased in the order pyraoxystrobin > pyraclostrobin > triclopyricarb > picoxystrobin > azoxystrobin > fluoxastrobin. Furthermore, the acute toxicity was strongly correlated with the enrichment level of the QoIs in aquatic organisms. This study provides the first documentation of a correlation between the enrichment level of QoIs and acute toxicity in aquatic organisms, which provides a basis for the management of agrochemicals considering aquatic ecological risks.

Growth Performance, Survival, Blood Chemistry, and Immune Gene Expression of Channel Catfish (Ictalurus punctatus) Fed Probiotic-Supplemented Diets

The channel catfish (Ictalurus punctatus) farming industry is the largest and one of the oldest aquaculture industries in the United States. Despite being an established industry, production issues stemming from disease outbreaks remain problematic for producers. Supplementing fish diets with probiotics to enhance the immune system and growth potential is one approach to mitigating disease. Although considerable laboratory data demonstrate efficacy, these results do not always translate to natural modes of disease transmission. Hence, the present work was conducted in the laboratory but incorporated flow-through water from large catfish pond production systems, allowing for natural exposure to pathogens. Two feeding trials were conducted in an 18-tank aquaria system housing two different sizes, 34.8 ± 12.5 g and 0.36 ± 0.03 g, of channel catfish. Channel catfish in the first trial were fed three experimental diets over six weeks. Commercial diets were top-coated with two selected spore-forming Bacillus spp. probiotics, Bacillus velezensis AP193 (1 × 106 CFU g−1) and BiOWiSH (3.6 × 104 CFU g−1), or a basal diet that contained no dietary additive. In the second eight-week trial, diets were top-coated with BiOWiSH at three concentrations (1.8, 3.6, and 7.3 × 104 CFU g−1), along with one basal diet (no probiotic). At the completion of these studies, growth performance, survival, hematocrit, blood chemistry, and immune expression of interleukin 1β (il1β), tumor necrosis factor-alpha (tnf-α), interleukin-8 (il8), transforming-growth factor β1 (tgf-β1), and toll-like receptor 9 (tlr9) were evaluated using qPCR. Trial results revealed no differences (p > 0.05) among treatments concerning growth, survival, or hematological parameters. For immune gene expression, interesting trends were discerned, with substantial downregulation observed in B. velezensis AP193-fed fish for il1β, tnf-α, and tlr9 expression within splenic tissue, compared to that of the basal and BiOWiSH diets (p < 0.05). However, the results were not statistically significant for anterior kidney tissue in the first trial. In the second trial, varied levels of probiotic inclusion revealed no significant impact of BiOWiSH’s products on the expression of il1β, tnf-α, il8, and tgf-β1 in both spleen and kidney tissue at any rate of probiotic inclusion (p > 0.05). Based on these findings, more research on utilizing probiotics in flow-through systems with natural infection conditions is crucial to ensure consistency from a controlled laboratory scale to real-world practices.

Occurrence, source tracking and removal of antibiotics in recirculating aquaculture systems (RAS) in southern China

The recirculating aquaculture system (RAS) has attracted much attention in China as a way to rapidly transform and upgrade aquaculture ponds to realize zero-emissions of pollutants in aquaculture tail water. Tail water purification ponds (TWPPs) play an important role in the treatment of aquaculture wastewater. However, until now, there have been few reports on the occurrence of antibiotics in RAS and the removal of antibiotics from the TWPPs of RAS. Therefore, this study focused on the occurrence of antibiotics in a typical ecological RAS. For comparison, the same measurements were simultaneously carried out in nearby open aquaculture ponds and rivers. The pollution level and spatial distribution of antibiotics in the RAS and the removal of antibiotics in the TWPPs were explored. The results showed that (1) eleven and twelve antibiotics were detected in water and sediment samples in the RAS, respectively, but no antibiotics were found in fish muscles and feed. Erythromycin (ERY), lincomycin (LIN), and ciprofloxacin (CFX) were the three main types of antibiotics found in water and sediment samples. (2) The TWPPs of the RAS can effectively remove antibiotics in aquaculture water. The antibiotic concentration in recirculating aquaculture ponds of the RAS was as high as 180 ng/L. After treatments in the TWPPs, the antibiotic concentration of aquaculture water decreased to 81.6 ng/L (3) The antibiotic concentrations in recirculating aquaculture ponds (25.2-180 ng/L) were lower than those in the nearby open aquaculture ponds (126-267.3 ng/L), and the concentration of antibiotics in the sediments of recirculating aquaculture ponds was up to 22.9 ng/g, while that in TWPPs was as high as 56.1 ng/g. In conclusion, the antibiotic residues in the RAS were low after antibiotics were banned in feed in China, and the removal of antibiotics in the TWPPs was more pronounced. Furthermore, cross-contamination was found between the RAS, surrounding open aquaculture ponds and the river, and the water supply of the RAS was likely to be the main contributor of antibiotics in the aquaculture environments. This study can help the government formulate discharge standards for antibiotics in aquaculture and also provide a reference for the transformation and upgrading of aquaculture ponds to achieve a zero-emission aquaculture mode.

Updated knowledge, partitioning and ecological risk of pharmaceuticals and personal care products in global aquatic environments

Over the last few decades, the occurrence of pharmaceuticals and personal care products (PPCPs) in aquatic environments has generated increasing public concern. In this review, data on the presence of PPCPs in environmental compartments from the past few years (2014-2022) are summarized by carrying out a critical survey of the partitioning among water, sediment, and aquatic organisms. From the available articles on PPCP occurrence in the environment, in Web of Science and Scopus databases, 185 articles were evaluated. Diclofenac, carbamazepine, caffeine, ibuprofen, ciprofloxacin, and sulfamethoxazole were reported to occur in 85% of the studies in at least one of the mentioned matrices. Risk assessment showed a moderate to high environmental risk for these compounds worldwide. Moreover, bioconcentration factors showed that sulfamethoxazole and trimethoprim can bioaccumulate in aquatic organisms, while ciprofloxacin and triclosan present bioaccumulation potential. Regarding spatial distribution, the Asian and European continents presented most studies on the occurrence and effects of PPCPs on the environment, while Africa and Asia are the most contaminated continents. In addition, the impact of COVID-19 on environmental contamination by PPCPs is discussed.

Toxicological differences of trifloxystrobin and kresoxim-methyl on zebrafish in various levels of exposure routes, organs, cells and biochemical indicators

Trifloxystrobin (TRI) and kresoxim-methyl (KRE), as quinone outside inhibitor fungicides (QoIs), have broad applications due to their effective activity against fungi. Excessive usages of agrochemicals trigger environmental risks, such as aquatic organisms (fish). Research performed in recent years has focused on the ecotoxicology of TRI and KRE in fish containing histologic morphology, enzyme activity, protein and gene expression under chronic toxicity conditions, whereas less is known about the underlying mechanisms of toxicity and differences between TRI and KRE in fish under acute toxicity conditions. In the present study, in comparison to different exposure routes [whole-body exposure (WBE), head exposure (HE), trunk exposure (TE), and Oral administration (OA)], the external substances TRI and KRE entered the fish body mainly via gill organs and led to fish toxicity. Furthermore, gill organs and gill cells were vulnerable to TRI and KRE exposure, which indicated that the gill is a vital impaired organ. The 96 h-LC₅₀ (sublethal concentration) value of KRE was 289.8 μg L^-1 (R² = 0.9855) with an approximate 10-fold difference in TRI toxicity. The cytotoxicity exposed to TRI was higher than that in KRE at the same concentration. The potential mechanisms of toxic differences could be various toxic effects in terms of MCIII (mitochondrial complex III) activity, ATP (Adenosine triphosphate) content, MA (mitochondrial activity), ROS (reactive oxygen species) levels, and cellular respiration. Furthermore, the disorder in MCIII activity was probably the main potential mechanisms of toxic differences. To some extent, this research provides not only new insight into the underlying toxic mechanism of TRI and KRE in fish but also a basis for the guidance of agrochemicals considering aquatic risks.

Residue, biotransformation, risk assessment and withdrawal time of enrofloxacin in red swamp crayfish (Procambarus clarkii)

Crayfish is a very popular aquatic food in many countries, and enrofloxacin (ENR) and ciprofloxacin (CIP) was the most frequently detected in aquatic products. However, limited information is available on the residue characterization, biotransformation rate and withdrawal period (WT) of ENR and CIP in crayfish and health risk via consumption of ENR and CIP remained crayfish. Herein, a comprehensive investigation was conducted to study residue depletion, biotransformation, ingestion risk, and WT of ENR and its predominate metabolite CIP in crayfish following different routes with repeated doses. The results showed that the elimination half-life (T_1/2) of target compounds in crayfish were all in order of hepatopancreas > muscle > gill, and the order of T_1/2 in different crayfish tissues were intramuscular (IM) route > oral (PO) treatment > immersion (IMMR) administration. The biotransformation rates from ENR to CIP varied from 0.75% to 3.45% in crayfish tissues following different exposure routes. The high dietary risk (RQ > 1) consuming muscle and hepatopancreas of ENR and CIP remained crayfish occurred at early after different administrations. WT is the key to control the drug residue risk, and the longest WT of marker residue of ENR in crayfish was calculated to be 51 d (1275 °C-day).

Quinolone distribution, trophodynamics, and human exposure risk in a transit-station lake for water diversion in east China

Quinolone antibiotics (QNs) pollution in lake environments is increasingly raising public concern due to their potential combined toxicity and associated risks. However, the spatiotemporal distribution and trophodynamics of QNs in transit-station lakes for water diversion are not well documented or understood. In this study, a comprehensive investigation of QNs in water, sediment, and aquatic fauna, including norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), and ofloxacin (OFL), was conducted in Luoma Lake, a major transit station for the eastern route of the South-to-North Water Diversion Project in China. The target QNs were widely distributed in the water (∑QNs: 70.12 ± 62.79 ng/L) and sediment samples (∑QNs: 13.35 ± 10.78 ng/g dw) in both the non-diversion period (NDP) and the diversion period (DP), where NOR and ENR were predominant. All the QNs were detected in all biotic samples in DP (∑QNs: 80.04 ± 20.59 ng/g dw). The concentration of ∑QNs in the water in NDP was significantly higher than those in DP, whereas the concentration in the sediments in NDP was comparable to those in DP. ∑QNs in the water-sediment system exhibited decreasing trends from northwest (NW) to southeast (SE) in both periods; however, the K_oc (organic carbon normalized partition coefficients) of individual QNs in DP sharply rose compared with those in NDP, which indicated that water diversion would alter the environmental fate of QNs in Luoma Lake. In DP, all QNs, excluding NOR, were all biodiluted across the food web; whereas their bioaccumulation potentials in the SE subregion were higher than those in the NW subregion, which was in contrast to the spatial distribution of their exposure concentrations. The estimated daily QN intakes via drinking water and aquatic products suggested that residents in the SE side were exposed to greater health risks, despite less aquatic pollution in the region.

Ciprofloxacin and enrofloxacin can cause reproductive toxicity via endocrine signaling pathways

Ciprofloxacin (CIP) and enrofloxacin (ENR) are veterinary antibiotics commonly utilized to treat and prevent animal diseases. Environmental and dietary antibiotic residues can directly and indirectly affect the reproductive development of animals and humans. This article investigated the reproductive toxicity of CIP in male zebrafish, showing that it could decrease the spermatogonial weight and damage the spermatogonial tissue. The sex hormone assays showed that CIP decreased fshb and lhb gene expression and plasma testosterone (T). In addition, transcriptome analysis indicated that the effect of CIP on zebrafish might be related to the endocrine signaling pathways. ENR, which was selected for further study, inhibited mouse Leydig (TM3) and Sertoli (TM4) cell proliferation and caused cell cycle arrest. The sperm concentration, serum luteotropic hormone (LH) and follicle-stimulating hormone (FSH), and T levels decreased in adolescent mice after ENR treatment for 30d in vivo. Hematoxylin and eosin (H&E) staining showed that ENR exposure potentially induced testicular injury, while the real-time quantitative PCR (qPCR) results indicated that ENR inhibited the mRNA expression of key genes in the Leydig cells (cyp11a1, 3β-HSD, and 17β-HSD), Sertoli cells (Inhbβ and Gdnf) and spermatogenic cells (Plzf, Stra8 and Dmc1). In conclusion, these findings indicated that ENR exposure might influence the development of the testes of pubescent mice.

Exposure to Veterinary Antibiotics via Food Chain Disrupts Gut Microbiota and Drives Increased Escherichia coli Virulence and Drug Resistance in Young Adults

Exposure to veterinary antibiotics (VAs) and preferred as veterinary antibiotics (PVAs) via the food chain is unavoidable for their extensive use not only for treating bacterial infections, but also for use as growth promoters in livestock and aquaculture. One of the consequences is the disturbance of gut microbiota. However, its impact on the virulence and drug resistance of opportunistic pathogens is still unclear. In this study, a total of 26 antibiotics were detected in the urine of 300 young undergraduates in Anhui Province. We found that excessive intake of milk was positively correlated to high levels of VAs and PVAs. It led to the dysbiosis of gut microbiota characterized by high abundance of Bacteroidetes and Proteobacteria. The increase in Proteobacteria was mainly due to a single operational taxonomic unit (OTU) of Escherichia coli (E. coli). We isolated several E. coli strains from participants and compared their drug resistance and virulence using PCR assay and virulence-related assays. We observed that exposure to high levels of VAs and PVAs induced more resistant genes and drove E. coli strain to become more virulent. At last, we conducted transcriptome analysis to investigate the molecular mechanism of virulent and drug-resistant regulators in the highly virulent E. coli strain. We noted that there were multiple pathways involved in the drug resistance and virulence of the highly virulent strain. Our results demonstrated that participants with high-level VAs and PVAs exposure have a disrupted gut microbiota following the appearance of highly drug-resistant and virulent E. coli and, therefore may be at elevated risk for long-term health complications.

Polycyclic aromatic hydrocarbons (PAHs) and antibiotics in oil-contaminated aquaculture areas: Bioaccumulation, influencing factors, and human health risks

Polycyclic aromatic hydrocarbon (PAH) pollution caused by marine oil spills and antibiotic pollution caused by aquaculture industries were common environmental problems in the Yellow River Estuary, China. But few data are reported on the bioaccumulation and influencing factors of these two types of contaminants in aquaculture simultaneously. This study investigated the occurrence and bioaccumulation of PAHs and antibiotics in aquaculture areas of the Yellow River Estuary, and explored the factors affecting the bioaccumulation. 3-ring PAHs and fluoroquinolones were dominant contaminants in the study area. The concentrations of PAHs and antibiotics in lipid-rich tissues (fish viscus, shrimp head, and crab ovary) was higher than that in muscle. It indicated that the lipid content was an important factor affecting the bioaccumulation capacity. Physicochemical parameters (K_ow and D_lipw) and the concentrations of PAHs or antibiotics also affected the bioaccumulation capacity of them. Meanwhile, biotransformation was a factor affecting the bioaccumulation of PAHs and antibiotics. The biotransformation (pyrene to 1-hydroxypyrene and enrofloxacin to ciprofloxacin) might explain the poor correlation between log bioaccumulation factor and log K_ow/log D_lipw in fish. Risk assessment indicated that PAHs in mature aquatic products posed carcinogenic risks to human and enoxacin in sea cucumbers posed health risks to human.