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Simple Summary: In commercial aquaculture, aquatic animals are generally administered medicine ad libitum (at one's pleasure) via medicated feed. However, the estimation of withdrawal times for aquatic medicine is mostly carried out through the forced administration of medicine via oral gavage, which is not consistent with commercial aquaculture. This process may influence the absorption, distribution, metabolism, and excretion of medicine in aquatic animals and further affect the calculation of withdrawal times (WTs) for medicines. Therefore, in the current study, we selected the important aquatic medicine enrofloxacin (EF) to estimate its WTs in largemouth bass (Micropterus salmoides) after the administration of medicated feed. This study will obtain practical estimations of the WT of EF in actual aquaculture to aid in the surveillance of medication residue in fish products. The present study investigated the residue depletion and WTs of EF and its main metabolite, ciprofloxacin, in largemouth bass after ad libitum administration in commercial fish farming based on statistical approaches. Samples collected at pre-determined time points were assessed using high-performance liquid chromatography. If the concentrations of medicine were less than the quantitative limit, they were set to be half of the limit of quantitative. The terminal elimination of the target compound was assumed to fit a one-compartment model. The statistical methods of Bartlett's test and Cochran's test were used to inspect the homogeneity of the log-transformed data. The lack-of-fit test and F-test were used to check the linearity of the regression line. Outliers were assessed using standardized residuals. The final WT was estimated using the 95% percentile with a 95% confidence level. The WTs of EF were calculated to be 46, 29, 33, 46, and 20 days for the muscle + skin, plasma, gill, kidney, and liver, respectively. After the risk assessment, the values of the hazard quotient were calculated to be far less than 1, indicating that the risk of residual EF was particularly low in the edible tissues of largemouth bass after medicine depletion for various WTs. [ABSTRACT FROM AUTHOR]

The purpose of this study was to measure organ blood flow (OBF) in yellow catfish (YC, Pelteobagrus fulvidraco), largemouth bass (LB, Micropterus salmoides), and grass carp (GC, Ctenopharyngodon idella) using the method of fluorescent microspheres. Yellow–green microspheres were injected into the fish via cardiac catheterization using a syringe pump at a rate of 0.8 mL/min. Reference blood samples were collected from the dorsal aorta, and fish tissues were harvested after 5 min and processed for fluorescence spectrophotometric analysis. The results showed that the OBF of the heart increased significantly with the increase in temperature from 20 to 30 °C, while there was no significant difference in the OBF of other organs/tissues in YC. The OBFs of different species of LB and GC were also determined at 25 °C. In GC, the blood flow rates of the heart, spleen, kidney, liver, others, gills, swim bladder, intestines, muscles, and skin were 9.55, 1.00, 10.3, 6.92, 6.70, 6.04, 2.06, 2.81, 1.78, and 3.72 (mL/min/g), respectively. In LB, the blood flow rates of the same organs were 8.80, 2.33, 1.01, 0.71, 4.11, 2.72, 1.22, 0.54, 9.47, and 0.40 (mL/min/g), respectively. Compared to the OBFs of YC at 25 °C, the OBFs in GC were the highest, followed by LB. These results reflect that OBF in fish has significant species differences. These studies provide fundamental physiological data on OBFs in YC, GC, and LB, which has practical implications for improving the development of disciplines associated with fish physiology. [ABSTRACT FROM AUTHOR]

Simple Summary: Tilapia is the second-most-farmed fish worldwide which plays a critical role in providing high-quality proteins to human. However, infections caused by S. agalactiae result in huge economic losses. Moreover, the spreads of antibiotic resistance restrict the use of antibiotics in treating S. agalactiae infections. Here, we tried to develop anti-S. agalactiae drugs by inhibiting SrtA to overcome infections caused by resistant bacterial strains. Sortase A (SrtA) is responsible for anchoring surface proteins to the cell wall, and has been identified as a promising target developing anti-infective drugs of Gram-positive bacteria. The aim of the study was to identify inhibitors of Streptococcus agalactiae (S. agalactiae) SrtA from natural compounds to overcome the spread of antibiotic resistance in aquaculture. Here, we found that the MIC of fraxetin against S. agalactiae was higher than 256 μg/mL, indicating that fraxetin had no anti- S. agalactiae activity. But fraxetin could dose-dependently decrease the activity of SrtA in vitro at concentrations ranging between 4–32 μg/mL by a fluorescence resonance energy transfer (FRET) assay. Moreover, the inhibition of SrtA by fraxetin decreased the anchoring of surface proteins with the LPXTG motif to the cell wall by detecting the immunofluorescence change of serine-rich repeat protein 1 (Srr1) on the bacterial cell surface. The results of fibronectin binding and cell adhesion assays indicated that fraxetin could significantly decrease the adhesion ability of S. agalactiae in a dose-dependent manner. The results were further proven by immunofluorescence staining. Animal challenge results showed that treatment with fraxetin could reduce the mortality of tilapia infected with S. agalactiae to 46.67%, indicating that fraxetin could provide a significant amount of protection to tilapia by inactivating SrtA. Taken together, these findings provided a novel inhibitor of S. agalactiae SrtA and a promising candidate for treating S. agalactiae infections in aquaculture. [ABSTRACT FROM AUTHOR]

Simple Summary: Sulfamethoxazole is a commonly used antimicrobial drug in aquaculture. In order to understand its effect on the liver transcriptome of channel catfish, we orally administered a certain proportion of sulfamethoxazole into the fish and analyzed the changes in the transcriptome to determine the effect of the drug on the fish. By studying changes in the transcriptome, we found that the drug acted on drug metabolizing functions in the liver. Stimulated fish try to ensure the normal expression of their physiological functions by accelerating the operation of various metabolisms. The detoxification process is facilitated by promoting glucuronidation in the fish liver; while lipid metabolism is increased, the antioxidant pathway is affected, and the glucose xenobiotic pathway is enhanced in order to maintain energy homeostasis and to ensure a normal energy supply for metabolism. Other cellular metabolisms are also carried out to repair damaged normal organisms. This study provides a reference for understanding drug metabolism in channel catfish and provides a warning about the use of the drug. Sulfamethoxazole is a widely used antimicrobial drug used to treat bacterial diseases in aquaculture. To understand the gene expression in channel catfish liver after treatment with sulfamethoxazole, in this study, the treatment group received sulfamethoxazole (100 mg/kg bw), which was administered orally once, and samples were taken at 5 h, 12 h, and 6 d after the administration of sulfamethoxazole, while the control group was orally administered sterile water. To further identify potentially significant genes, a transcriptome analysis using RNA-seq was carried out. More than 50 million high-quality reads were found. After filtering and quality analysis, these reads were identified as 54,169,682, 51,313,865, 51,608,845, and 49,333,491. After counting 23,707 of these transcripts for gene expression, it was discovered that 14,732 of them had genes with differential expression. Moreover, we found that the annotation with the most GO variation was "cellular process" (1616 genes), "metabolic process" (1268 genes), "binding" (1889 genes), and "catalytic activity" (1129 genes). KEGG pathways showed that the "metabolic pathway" was the pathway that was significantly enriched in both experimental groups when comparing the experimental groups: 5 h and 12 h (128 genes); 5 h and 6 d (332 genes); and 12 h and 6 d (348 genes). Also, UDP- glucuronosyltransferase (ugt), which is associated with glucuronidation, and UDP-glucuronosyltransferase 2C1-like (ugt2a1) showed significant upregulation. Carboxylesterase 5A-like (ces3), which promotes fatty acyl and cholesteryl ester metabolism, and the glutathione transferase family were upregulated in the expression of sulfamethoxazole metabolism in the liver, which significantly affected the metabolic effects of the drug. Meanwhile, dypd, uck2b, and rrm2, which are related to nucleotide synthesis and metabolism, were upregulated. Our study extends the knowledge of gene expression in drug metabolism in channel catfish and further provides insight into the molecular mechanism of sulfamethoxazole metabolism. [ABSTRACT FROM AUTHOR]

Simple Summary: Chlorpheniramine hydrochloride (ROBH) is a synthetic anticoccidial drug in global aquaculture. The abuse and inappropriate use of ROBH may result in mortality in animals and drug residues in foodborne animals. Mass balance studies not only provide insights into the drug disposal process in animals, but also provide information on the metabolite composition and elimination pathways, leading to the identification of pharmacological metabolites. However, there are no related reports of mass balance studies for ROBH in fish. In addition to prodrugs, ROBH may include PCBA and PCHA as major metabolites. Therefore, this study was conducted to monitor ROBH levels and possible metabolites in Channel catfish (Ictalurus punctatus) to provide a theoretical basis for the development of maximum residue limits (MRLs) for ROBH in aquatic animals. This study aims to determine the mass balance of chlorpheniramine hydrochloride (ROBH) in the body of Channel catfish (Ictalurus punctatus). ROBH was administered orally at a dose of 20 mg/kg; following drug administration, the water samples were collected at predetermined time points (12, 24, 48, 72, 96, 120, 144, and 168 h), the experimental fish were executed after the water samples were obtained at 168 h, and the tissue samples were collected separately from the bones. The water and tissue samples were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC–MS/MS) for concentrations of ROBH and its potential major metabolites, 4-chlorohippuric acid (PCHA) and 4-chlorobenzoic acid (PCBA). The tissue samples were prepared using a modified QuEChERS procedure; the water samples were prepared using a liquid–liquid extraction (LLE) procedure. The results show that the recovery rate of ROBH in fish is very low, less than 2% of the total amount of the drug, and the recovery in water can reach 80.7% of the total amount of the drug. The content of PCBA accounted for 42.4% of the total amount of the drug; the content of ROBH accounted for 38.3% of the total amount of the drug. The content of PCHA accounted for less than 1% of the total amount of the drug. The results show that, after a single administration, ROBH is rapidly metabolized in vivo and excreted in the form of ROBH as well as metabolite PCBA. ROBH and PCBA can be used as the main targets for the metabolism detection of ROBH in Channel catfish. [ABSTRACT FROM AUTHOR]

Simple Summary: Enrofloxacin (EF) is an important antibiotic in global aquaculture. Due to the abuse and the emergence of drug resistance, the excess use of EF has occurred in recent years to result in residue exceeding in the edible tissues of aquatic animals. Withdrawal time (WT) is a red line to ensure food safety for humans. However, there is no related report of WT for EF in yellow catfish (Pelteobagrus fulvidraco). In addition to yellow catfish being sensitive to temperature, it can alter the disposition and elimination of EF and its main metabolite in fish bodies, ciprofloxacin (CF), thereby changing the WT in tissues. Therefore, we will conduct a WT estimation of EF in yellow catfish at different temperatures to establish related regulations to help residue surveillance in fish products. The objective of the present study was to investigate the residue depletion of EF and CF in yellow catfish to estimate its WTs in plasma and tissues after multiple oral doses for 3 days at 20 mg/kg at 15, 20, and 25 °C. Samples were collected at pre-designed time points after oral doses. A validated method was performed to quantify EF and CF in plasma and tissues by high-performance liquid chromatography. Statistical differences were conducted using one-way ANOVA analysis. According to the maximum residue limit of China and Europe considering 95% percentile with 95% confidence, the WTs were estimated to be 44, 72, 66, 99, and 95 days at 15 °C; 32, 66, 65, 86, and 73 days at 20 °C; and 32, 61, 64, 55, and 59 days at 25 °C in the plasma, muscle and skin, gill, liver, and kidney, respectively. We found that increased temperature shortened the WTs in plasma and tissues. Therefore, this study can help the risk assessment of EF in aquatic products for human health at different temperatures to avoid residue violation. [ABSTRACT FROM AUTHOR]

IL-10 and IL-6 play important roles in protecting against inflammation and clearing pathogens from the body. In this study, homologous compounds of IL-10 and IL-6 were identified in channel catfish, and their immune responses were analyzed. The CDS sequences of IL-10 and IL-6 were 549 bp and 642 bp, respectively, and showed the highest homology with Ameiurus melas. In addition, the expression of the IL-10 and IL-6 genes was ubiquitous in 10 tissues examined. IL-10 is highly expressed in the liver and slightly expressed in the gill. The high expression of the IL-6 gene was observed in the spleen, heart, and gonad, with the lowest levels in the liver. LPS, Poly(I:C), PHA, and PMA showed a highly significant increase in IL-10 and IL-6 expression 48 h after CCK stimulation (p < 0.01). Otherwise, Yersinia ruckeri, Streptococcus iniae, channel catfish virus, and deltamethrin induced IL-10 and IL-6 expression, varying in intensity between different organs. Our results suggest that IL-10 and IL-6 are involved in the immune response of the host against the pathogen. [ABSTRACT FROM AUTHOR]

Simple Summary: Enrofloxacin (EF) is a commonly used broad-spectrum antibiotic in aquaculture against Gram-negative and Gram-positive bacteria. Ciprofloxacin (CF) has similar antibacterial activities to EF and has been developed as an aquatic medicine. It is well known that only the free concentration of a drug is effective for killing challenging pathogens. Hence, the plasma protein binding ratio (PPBR) of drugs is an important parameter in clinical medicine. Although PPBRs of EF and CF have been reported in several livestock animals, little information is available on aquatic animals. Moreover, environmental temperatures may influence the PPBR of drugs used for aquatic animals. Therefore, this study investigates PPBRs of EF and CF in the plasma of several finfish species such as yellow catfish (Pelteobagrus fulvidraco), grass carp (Ctenopharyngodon idella), and largemouth bass (Micropterus salmoides) at different concentrations with different temperatures. The present study facilitates the design of therapeutic regimens of EF for different aquatic animals at different concentrations. The objective of this study was to investigate the PPBRs of EF and CF in the plasma of yellow catfish, grass carp, and largemouth bass at different temperatures with different concentrations. A fast and simple ultrafiltration method was used to determine the PPBRs of EF and CF. Results showed that PPBRs of EF decreased from 37.71% to 9.66%, from 46.10% to 13.52%, and from 43.90% to 4.36% in the plasma of yellow catfish with the increase of concentration from 15 to 25 °C. The same trends of PPBRs of EF were presented in the plasma of grass carp and largemouth bass. In comparison to the data at the same concentration of EF at disparate temperatures, the PPBRs of EF at a concentration of 1 µg/mL increased from 37.71% to 46.10% and then decreased to 43.90% in the plasma of yellow catfish with elevated temperature from 15 to 25 °C. There is no obvious regularity with the rise of temperature, and the same phenomenon also were found in other concentrations and species. Meanwhile, the PPBRs of CF also decreased in the three species with the rise in concentration. Under the consistent concentration, the temperature-dependent regularities were not found in the PPBRs of CF. Overall, the increased concentration reduced the PPBRs of EF and CF in the plasma of three fish species, and the alteration in temperature only has a certain effect on the PPBRs of EF and CF. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the potential adverse effects of the practical application of copper sulfate on yellow catfish (Pelteobagrus fulvidraco) and to provide insights into the gill toxicity induced by copper sulphate. Yellow catfish were exposed to a conventional anthelmintic concentration of copper sulphate (0.7 mg/L) for seven days. Oxidative stress biomarkers, transcriptome, and external microbiota of gills were examined using enzymatic assays, RNA-sequencing, and 16S rDNA analysis, respectively. Copper sulphate exposure led to oxidative stress and immunosuppression in the gills, with increased levels of oxidative stress biomarkers and altered expression of immune-related differentially expressed genes (DEGs), such as IL-1β, IL4Rα, and CCL24. Key pathways involved in the response included cytokine–cytokine receptor interaction, NOD-like receptor signaling pathway, and Toll-like receptor signaling pathway. The 16S rDNA analysis revealed copper sulphate altered the diversity and composition of gill microbiota, as evidenced by a significant decrease in the abundance of Bacteroidotas and Bdellovibrionota and a significant increase in the abundance of Proteobacteria. Notably, a substantial 8.5-fold increase in the abundance of Plesiomonas was also observed at the genus level. Our findings demonstrated that copper sulphate induced oxidative stress, immunosuppression, and gill microflora dysbiosis in yellow catfish. These findings highlight the need for sustainable management practices and alternative therapeutic strategies in the aquaculture industry to mitigate the adverse effects of copper sulphate on fish and other aquatic organisms. [ABSTRACT FROM AUTHOR]

Antibiotics were the main fishery drugs for treating Aeromonas hydrophila (A. hydrophila) infection, which would generate selective pressure and result in the appearance of antibiotic-resistant bacteria. The bacterial quorum sensing (QS) system provides a new alternative strategy against A. hydrophila infection. QS inhibitors can reduce bacterial virulence behaviors by disrupting QS, which has no effect on bacterial growth. Therefore, we studied the effect of cinnamaldehyde from a natural plant extract on the QS of A. hydrophila aiming to reduce its pathogenicity. The efficacy of cinnamaldehyde against A. hydrophila was evaluated from various aspects, including the effects on aerolysin, lipase, protease, swarming motility, biofilm formation, acyl-homoserine lactones (AHLs), and QS-related genes. Moreover, the therapeutic effect of cinnamaldehyde in vitro and in vivo was studied. The results showed that cinnamaldehyde could decrease the virulence phenotypes of A. hydrophila regulated by QS. Moreover, the transcriptions of related genes (aerA, ahyR, and ahyI) were downregulated following the addition of cinnamaldehyde. The in vitro and in vivo therapeutic assays show that cinnamaldehyde could reduce the aerolysin-mediated A549 cell injury and increase the survival rate of crucian carp infected with A. hydrophila. These results indicate that cinnamaldehyde would be a candidate QS inhibitor against A. hydrophila infection. [ABSTRACT FROM AUTHOR]

In this study, a fast, concise and reliable ultra-high performance liquid chromatography-fluorescence (UHPLC/FLD) detection method for simultaneous quantification of avermectins (AVMs), including avermectin (AVM), ivermectin (IVM), emamectin (EMM), moxidectin (MOX) and doramectin (DOR) in six aquatic foods was established. Based on the QuEChERS pretreatment method, the samples were extracted with 0.2% (v/v) ammonia acetonitrile. N-methyl imidazole mixed with acetonitrile (1:1, v/v) and trifluoroacetic anhydride with acetonitrile (1:2, v/v) were used as derivatization reagents. The mobile phase consists of acetonitrile and water with a flow rate of 1.0 mL/min. An Infinity Lab Poroshell 120 EC-C18 column was used for optimum chromatographic separation of target analytes at 40 °C; the excitation and emission wavelengths were set at 365 nm and 465 nm, respectively. In six kinds of aquatic foods, the limits of detection (LODs) of AVM, IVM, EMM, MOX, and DOR were 2.7 μg/kg, 1.8 μg/kg, 2.1 μg/kg, 1.2 μg/kg, and 2.7 μg/kg, respectively, and the limits of quantification (LOQs) of AVM, IVM, EMM, MOX, and DOR were 5 μg/kg, 4.5 μg/kg, 4.5 μg/kg, 3.5 μg/kg and 5.0 μg/kg, respectively. The recoveries were all above 85.38% when the samples were spiked with the target compounds at the concentration level of 5, 10, 50, and 100 μg/kg. The intra-day and inter-day relative standard deviations (RSDs) were all less than 15%. This method considers the requirements of sensitivity, accuracy, and economics of the instrument. [ABSTRACT FROM AUTHOR]

Herein, we isolated the pathogenic strain ZZ051 from hemorrhagic channel catfish (Ictalurus punctatus). Physiological and biochemical identification, 16S rRNA gene sequence analysis, and MALDI-TOF-MS showed that the ZZ051 strain was Aeromonas veronii. After artificial infection, the diseased fish showed symptoms similar to the natural disease, and the characteristics of the bacteria reisolated from the tissues were the same as those of the original infection, indicating that the isolated strain ZZ051 was the pathogen responsible for the channel catfish disease. The ZZ051 isolate was highly sensitive to enrofloxacin but resistant to florfenicol. This study provided a theoretical basis for preventing and controlling hemorrhagic disease in channel catfish. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila, an opportunistic aquatic pathogen widely spread in aquatic environments, is responsible for a number of infectious diseases in freshwater aquaculture. In addition, A. hydrophila can transmit from diseased fish to humans and results in health problems. The occurrence of antibiotic-resistant bacterial strains restricts the application of antibiotics and is responsible for failure of the treatment. Moreover, residues of antibiotics in aquatic products often threaten the quality and safety. Therefore, alternative strategies are called to deal with infections caused by antibiotic-resistant bacteria. Aerolysin, one of the most important virulence factors of A. hydrophila, is adopted as a unique anti-virulence target on the basis of the anti-virulence strategy to battling infections caused by A. hydrophila. Palmatine, an isoquinoline alkaloid from a variety of herbal medicines that showed no anti-A. hydrophila activity, could reduce hemolysis of the bacterium by decreasing aerolysin production. The results of the qPCR assay demonstrated that the transcription of the aerA gene was suppressed. Moreover, cell viability and in vivo study showed that palmatine treatment could decrease the pathogenicity of A. hydrophila both in vitro and in vivo. In summary, palmatine is a leading compound against A. hydrophila-associated infection in aquaculture by inhibiting the expression of aerolysin. [ABSTRACT FROM AUTHOR]

Simple Summary: Aquaculture is an important source of animal protein. However, in recent years, with an intensification of farming, the risk of infectious diseases is increasing, especially the diseases caused by monogeneans, resulting in huge economic losses to aquaculture. Currently, the prevention and control of monogenean in fish mainly rely on some chemical drugs, such as formaldehyde, rotenone, and praziquantel. However, prolonged and frequent use of these chemicals leads to the occurrence of drug resistance, some adverse environmental impacts, and even contamination of fish products with drug residues. Therefore, it is urgent to develop efficient and environment-friendly drugs for the control of monogeneans in aquaculture. Natural plant-derived medicines are one of the alternative options. Therefore, in this study, anthelmintic efficacy of various essential oils was evaluated. The results indicated that palmarosa oil and curcuma oil showed potent anthelmintic activity against monogenean, and curcuma oil also had an anesthetic effect on monogenean. Moreover, these two essential oils displayed a high safety for fish. Therefore, palmarosa oil and curcuma oil could be viable alternatives for the prevention and control of monogenean infection in aquaculture. Monogeneans are a serious threat to the development of aquaculture due to the severe economic losses they cause. The prevention and treatment of this disease are increasingly difficult because of the environmental and health concerns caused by the use of chemical anthelmintics and the emergence of drug resistance. It is thus necessary to search for effective alternatives for the treatment of monogenean infections. In the current study, anthelmintic efficacy of 16 selected essential oils (EOs) was investigated using the goldfish (Carassius auratus)–Gyrodactylus kobayashii model. The screening experiment indicated that palmarosa oil and curcuma oil had satisfactory anthelmintic activity against G. kobayashii with EC100 values of 10 and 12 mg/L after 24-h exposure, respectively. The in vivo and in vitro assays indicated anthelmintic efficacy of palmarosa oil against G. kobayashii was in a time and dose-dependent manner. Interestingly, curcuma oil showed an anesthetic effect on G. kobayashii, and its anthelmintic activity was dose-dependent rather than time-dependent in the concentration range tested in this study. Additionally, the 24-h LC50 (50% lethal concentration) against goldfish of these two EOs was 8.19-fold and 5.54-fold higher than their corresponding EC50 (50% effective concentration) against G. kobayashii, respectively. Moreover, exposure to these two EOs at 100% effective concentration against G. kobayashii had no serious physiological and histopathological influence on goldfish. These results demonstrated a high safety for goldfish of these two EOs. Overall, palmarosa oil and curcuma oil could be potential candidates for the treatment of G. kobayashii infections in aquaculture. [ABSTRACT FROM AUTHOR]

This study investigated elimination of the herbicide pendimethalin using an integrated rice and Procambarus clarkii breeding model of indoor and outdoor (pond culture) exposure tests. The pendimethalin levels in 484 samples from the primary rice and P. clarkii integrated breeding areas in Hubei province were monitored, and dietary risk assessments of pendimethalin were calculated. Pendimethalin was quantified using high-performance liquid chromatography tandem mass spectrometry, and detection levels were linear in the range of 1.0 to 10.0 μg/L, and peak areas were positively correlated with concentration, with a correlation coefficient of 0.9996. Recoveries ranged from 86.9 to 103.5%, and the limit of quantitation was 2.5 × 10−4 μg/L in water, and 1 × 10−2 μg/kg in tissues, sediments, and waterweeds. The dissipation rate of pendimethalin in tissues and water followed first-order kinetics, with half-lives of 0.51–5.64 d. In 484 samples taken from aquaculture farms, pendimethalin was detected in 8.67% of the samples at levels in the range of 1.95 to 8.26 μg/kg in Hubei province from 2018 to 2020. The maximum residue limit of pendimethalin in P. clarkii has not been established in China, but our dietary risk assessments indicated that consumption of P. clarkii from integrated rice farms was acceptable. [ABSTRACT FROM AUTHOR]

In this study, the plasma pharmacokinetics and tissue disposition of sulfadiazine (SDZ) and its main metabolite, N4-acetyl sulfadiazine (ACT-SDZ), were compared between 18 and 24 °C following a single oral administration of SDZ at 50 mg/kg in grass carp (Ctenopharyngodon idella). The plasma and tissues were sampled from 0.167 h up to 96 h and analyzed by ultra-performance liquid chromatography with an ultraviolet detector. The pharmacokinetic parameters were estimated using a one-compartmental approach. Results showed that pharmacokinetics of SDZ and ACT-SDZ in plasma and tissues were notably influenced by the increase of temperature. The increased temperature shortened the absorption half-life (K01_HL) of SDZ and ACT-SDZ in gill, kidney, and plasma, but increased in liver and muscle + skin. The elimination half-life (K10_HF) and the area under concentration-time curve (AUC0–∞) of SDZ and ACT-SDZ all presented a declined trend. The apparent volume of distribution (V_F) of SDZ in plasma was increased from 0.93 to 1.64 L/kg, and the apparent systemic total body clearance (Cl_F) was also increased from 0.01 to 0.05 L/h/kg. Overall, the rise of temperature decreased K10_HF, AUC0–∞ of SDZ, and ACT-SDZ in plasma and tissues, but increased V_F and Cl_F in the plasma for SDZ. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is a pathogenic bacterium that can cause serious infections both in humans and aquatic animals. Antibiotics are the main approach for fighting against the pathogen. However, the emergence of antibiotic resistance has resulted in treatment failure. Therefore, drugs with novel strategies need to be developed. Quorum sensing has been recognized as a promising method for identifying anti-virulence drugs against bacterial infections. The aim of this study was to identify novel drugs targeting quorum sensing of A. hydrophila as alternatives of antibiotics in aquaculture. Thus, hemolytic activity, biofilm formation, qPCR and experimental therapeutics assays were conducted. The results showed that sanguinarine inhibited the growth of A. hydrophila at concentrations higher than 16 μg/mL, but the production of aerolysin and biofilm formation was significantly inhibited at sub-inhibitory concentrations by disrupting the quorum sensing system. Cell viability results showed that sanguinarine could provide protection for A549 cells from aerolysin-induced cell injury. In addition, the mortality of channel catfish administered with sanguinarine at a dosage of 20 mg/kg decreased to 40%, which showed a significant decrease compared with fish in positive group. Taken together, these findings demonstrated that anti-virulence strategies can be a powerful weapon for fighting against bacterial pathogens and sanguinarine appears to be a promising candidate in the treatment of A. hydrophila infections. [ABSTRACT FROM AUTHOR]

This correction notice addresses errors in the original publication titled "Mass Balance Studies of Robenidine Hydrochloride in the Body of Channel Catfish (Ictalurus punctatus)." The errors include miswriting the word "Chlorpheniramine" and using it instead of the correct term "Robenidine." The title, summary, abstract, keywords, reagents section, recovery section, and reference have been corrected to reflect the accurate information. The authors assure that the scientific conclusions remain unaffected. [Extracted from the article]

Limited information on residue depletion of doxycycline (DC) is available in yellow catfish (Pelteobagrus fulvidraco) using the determination of LC-MS/MS based upon a rapid and simple method of sample preparation. This study collected plasma and tissue samples of yellow catfish at pre-determined time points following 3-day consecutive oral administration of DC at 20 mg/kg. The samples were prepared using a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) approach. The limit of detection and the limit of quantitation were 2.5 and 5 µg/kg or µg/L, respectively, for DC in plasma and tissues (e.g., muscle + skin, liver, kidney, and gill). The recoveries of DC ranged from 67.2% to 86.2%. The decision limit (CCα) and the detection capability (CCβ) were from 106.2 to 127.8 μg/kg or μg/L. The withdrawal times of DC in muscle + skin were estimated to be 22 d based on the guidelines in China and Europe and 27 d based on Japan's standard. Overall, this study not only provides an efficient method to rapidly determine the DC concentrations in fish-derived tissues but also provides important information on the safety assessment of DC in aquatic animal-derived food products. [ABSTRACT FROM AUTHOR]

Simple Summary: Trichloroisocyanuric acid (TCCA) has been widely used in public health and aquaculture for the prevention and treatment of diseases. As a strong oxidative disinfectant, TCCA may cause adverse influences on aquatic organisms and further poses a threat to the aquatic ecosystems. Nonetheless, the toxicological influences of TCCA on aquatic animals are still scarce and the mechanisms of the toxicity at the molecular levels in goldfish (Carassius auratus) have not been illustrated. The current study investigated the influences of sublethal concentration of TCCA on transcriptomic responses, the molecular indices of oxidative stress, and histopathological alterations in the hepatic and gill tissues of goldfish. The results indicated that TCCA exposure induced the disturbance of energy metabolism and the detoxification process. Furthermore, TCCA exposure also induced oxidative stress in the liver and caused pathological damage in gills. These findings could be useful to help understand the toxicological influences of TCCA on goldfish. In this study, goldfish (Carassius auratus) were exposed to 0 (control group) and 0.81 mg/L TCCA for four consecutive days. The liver transcriptome, the molecular indices of oxidative stress, and gills histopathology were investigated. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that energy metabolism-related pathways such as glycolysis/gluconeogenesis were significantly enriched, suggesting their perturbation in the liver of goldfish. Additionally, TCCA exposure also caused pathological damage in gills, which compromised physiological function and decreased oxygen intake capacity of gills, thus leading to the enhancement of anaerobic metabolism. This finding was confirmed by the significant upregulation of lactate dehydrogenase in the liver of goldfish. Moreover, many phase I and phase II metabolic enzymes might be activated to alleviate TCCA-induced toxicity in goldfish, and glutathione S-transferases (GSTs) and cytochrome P450s (CYPs) play a crucial role in the metabolism of TCCA in the liver of goldfish. Furthermore, the antioxidant enzyme analysis showed that TCCA exposure induced oxidative damage in the liver and partially impaired the antioxidant defense system of goldfish, evidenced by decreased superoxide dismutase (SOD) and catalase (CAT), and increased malondialdehyde (MDA) level. In summary, this study will improve our understanding of the molecular mechanisms of the TCCA-induced toxicity in goldfish. [ABSTRACT FROM AUTHOR]

This study aimed to examine the pharmacokinetics of doxycycline (DC) in yellow catfish (Pelteobagrus fulvidraco) and to calculate related pharmacokinetic–pharmacodynamic (PK/PD) parameters of DC against Edwardsiella ictaluri. The minimum inhibitory concentration of DC against E. ictaluri was determined to be 500 µg/L. As the increase of oral dose from 10 to 40 mg/kg, the area under the concentration vs. time curve from 0 to 96 h (AUC0–96) values were considerably increased in gill, kidney, muscle and skin, and plasma, except in liver. Cmax values exhibited a similar dose-dependent increase trend in plasma and tissues except in liver, but other PK parameters had no apparent dose-dependence. The PK/PD parameter of the ratio of AUC0–96 to minimum inhibitory concentration (AUC0–96h/MIC) was markedly increased in plasma and tissues dose-dependently except in liver, but %T > MIC values were increased only moderately at some dose groups. After receiving the same dose with disparate time intervals from 96 to 12 h, the AUC0–96h/MIC was distinctly increased in plasma and tissues, but the %T > MIC had a decreasing trend. When administering 20 mg/kg with a time interval of 96 h, the AUC0–96h/MIC values were consistently >173.03 h and the %T > MIC values were above 99.47% in plasma and all tissues. These results suggest that administration of DC at 20 mg/kg every 96 h is a preferable regimen in yellow catfish. [ABSTRACT FROM AUTHOR]

We developed a method for determination of imidacloprid and its metabolites 5-hydroxy imidacloprid, olefin imidacloprid, imidacloprid urea and 6-chloronicotinic acid in Procambarus clarkii (crayfish) tissues using quick, easy, cheap, effective, rugged, and safe (QuEChERS) and high-performance liquid chromatography-triple quadrupole mass spectrometry. Samples (plasma, cephalothorax, hepatopancrea, gill, intestine, and muscle) were extracted with acetonitrile containing 0.1% acetic acid and cleaned up using a neutral alumina column containing a primary secondary amine. The prepared samples were separated using reverse phase chromatography and scanned in the positive and negative ion multiple reaction-monitoring modes. Under the optimum experimental conditions, spiked recoveries for these compounds in P. clarkii samples ranged from 80.6 to 112.7% with relative standard deviations of 4.2 to 12.6%. The limits of detection were 0.02–0.5 μg·L−1, the limits of quantification were 0.05–2.0 μg·L−1 and the method of quantification was 0.05–2.0 μg·kg−1. The method is rapid, simple, sensitive and suitable for rapid determination and analysis of imidacloprid and its metabolites in P. clarkii tissues. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is an opportunistic pathogen responsible for a number of diseases in freshwater farming. Moreover, the bacterium has been identified as a zoonotic pathogen that threatens human health. Antibiotics are widely used for treatments of infectious diseases in aquaculture. However, the abuse of antibiotics has led to the emergence of antimicrobial resistant strains. Thus, novel strategies are required against resistant A. hydrophila strains. The quorum sensing (QS) system, involved in virulence factor production and biofilm formation, is a promising target in identifying novel drugs against A. hydrophila infections. In this study, we found that thymol, at sub-inhibitory concentrations, could significantly reduce the production of aerolysin and biofilm formation by inhibiting the transcription of genes aerA, ahyI, and ahyR. These results indicate that thymol inhibits the quorum sensing system. The protective effects of thymol against A. hydrophila mediated cell injury were determined by live/dead assay and lactate dehydrogenase (LDH) release assay. Moreover, the in vivo study showed that thymol could significantly decrease the mortality of channel catfish infected with A. hydrophila. Taken together, these findings demonstrate that thymol could be chosen as a phytotherapeutic candidate for inhibiting quorum sensing system-mediated aerolysin production and biofilm formation in A. hydrophila. [ABSTRACT FROM AUTHOR]