Population Pharmacokinetics of Danofloxacin in Yellow River Carp (Cyprinus carpio haematopterus) After One Single Oral Dose

In-feed oxolinic acid induces oxidative stress and histopathological alterations in Nile tilapia Oreochromis niloticus

The aquaculture industry urgently requires effective bacterial disease management strategies, necessitating better regulation of antibiotic application. This study investigated the effects of oral oxolinic acid (OA) administration on Oreochromis niloticus at the recommended dose of 12 mg (1 ×) and overdose of 36 mg (3 ×)/kg biomass/day for 7 consecutive days in terms of growth, oxidative stress, residue accretion and histopathology relative to the control. The 1 × and 3 × groups experienced dose-dependent mortalities (3.33-8.33 %). The OA residues peaked in the liver and kidney tissues with dosing and declined upon discontinuation. The residues persisted in the kidney even on day 35 post-dosing. Elevated malondialdehyde and total nitric oxide levels signified oxidative stress and correlated with the tissue level changes in various organs. Histologically, glycogen-type vacuolation and cellular hypertrophy were observed in the liver. The kidney had hydropic swelling, renal epithelium degradation, nephrocalcinosis, vacuolation, and necrosis. Splenic alterations were confined to necrosis and a slight increase in sinusoidal space. Intestinal tissues exhibited a depletion of absorptive vacuoles, epithelial layer degradation, mucinous degeneration, and necrosis. Gills displayed epithelial hyperplasia, thickening of secondary lamellae, and erosion. Nevertheless, the cohort administered the recommended dose exhibited recovery with OA discontinuation. However, none of the assessed parameters normalized in the overdosed group even after 35 days of dose suspension. The results indicated that O. niloticus can safely adapt to and tolerate the toxic effects of OA. As the recommended dose of OA elicited reversible bioresponses effectively in tilapia, it can be utilized in aquaculture with due caution following regulations.

Population Pharmacokinetics of Enrofloxacin in Micropterus salmoides Based on a Nonlinear Mixed Effect Model After Intravenous and Oral Administration

This study aimed to investigate the PPK of EF in largemouth bass after oral and intravenous administration based on a nonlinear mixed effect model. Samples were collected using the sparse sampling method at pre-designed time points determined by high-performance liquid chromatography with a fluorescent detector. The initial PK parameters were estimated by reference search and the calculation of a naïve pooled approach. The covariate model included a variation in body weight. The oral dose data were best fitted by a one-compartment model. The injection dose data were best fitted by a two-compartment model. The results demonstrated that body weight had no marked effect on the parameters of PPK. Finally, the bioavailability was calculated to be 12.24%. The area under the concentration-time curve/minimum inhibitory concentration was estimated to be ≥408.16, indicating that EF at 20 mg/kg has high effectiveness for aquatic pathogens.

Population Pharmacokinetics of Enrofloxacin in Ctenopharyngodon idella Based on the Sparse Sampling Method and a Nonlinear Mixed Effect Model Following Intravenous and Oral Administration

The objective of this study was to implement population pharmacokinetic (PPK) of enrofloxacin (EF) in grass carp (Ctenopharyngodon idella) after a single oral administration and a single intravenous administration based on a nonlinear mixed effect model. The plasma samples collected by the sparse sampling method were detected by high-performance liquid chromatography with a fluorescent detector. The initial pharmacokinetic (PK) parameters were evaluated by reference search and the calculation of a naïve pooled method. After oral administration, the concentration-time profile was best described by a one-compartment open model. The absorption rate constant (Ka), apparent distribution volume (V), and systemic clearance (CL) were estimated to be 3.11/h, 4.36 L/kg, and 0.079 L/h/kg, respectively. After intravenous administration, the concentration-time curve was best simulated by a two-compartment open model. The apparent distribution volume of the central compartment (V1), apparent distribution volume of the peripheral compartment (V2), CL, and clearance from the central compartment to the peripheral compartment (CL2) were estimated to be 0.42, 2.05 L/kg, 0.067, and 2.94 L/h/kg, respectively. Finally, the bioavailability was calculated to be 84.81%. The parameter of AUC/minimum inhibitory concentration value was estimated to be more than 506.32 for Aeromonas hydrophila, Aeromonas sobria, and Flavobacterium columnare indicating that EF at 20 mg/kg has high effectiveness for these pathogens. This study supported a concise method for conducting PK study in aquatic animals that facilitated the development of PK methodology in aquaculture.

Pharmacokinetics and Tissue Distribution of Albendazole and Its Three Metabolites in Yellow River Carp (Cyprinus carpio haematopterus) after Single Oral Administration

This study aimed to evaluate the pharmacokinetics and tissue distribution of albendazole (ABZ) and its three metabolites─albendazole sulfoxide (ABZSO), albendazole sulfone (ABZSO2), and albendazole-2-aminosulfone (ABZ-2-NH2-SO2)─in Yellow River carp (Cyprinus carpio haematopterus) reared at 17.2 ± 1.1 °C after single oral administration of 12 mg/kg body weight (BW) ABZ. The concentrations of ABZ and its metabolites in different samples were measured using high performance liquid chromatography (HPLC). Pharmacokinetic parameters for ABZSO2 and ABZ-2-NH2-SO2 were not estimated due to their low levels. Pharmacokinetic analysis of ABZ and ABZSO was conducted using average concentration-time data with Phoenix software. The Cmax values (μg/mL or μg/g) of ABZ in skin-on muscle, plasma, bile, kidney, gills, liver, and intestine were 0.65, 0.70, 1.01, 1.61, 1.71, 2.42, and 3.34, respectively. The elimination half-life (t1/2λZ) of ABZ was longest in skin-on muscle (37.92 h), followed by the liver (32.07 h), gills (31.92 h), bile (31.51 h), kidney (26.96 h), intestine (20.81 h), and plasma (19.86 h). For ABZSO, the Cmax values (μg/mL or μg/g) in plasma, skin-on muscle, gills, intestine, liver, kidney, and bile were 0.46, 0.76, 0.89, 1.13, 1.54, 1.89, and 3.78, respectively. These findings indicate that ABZ and ABZSO are widely distributed and metabolized slowly in Yellow River carp after single oral administration. The higher ABZ concentrations in the liver and kidney suggest that these are the main metabolic organs for ABZ, while the elevated levels of ABZSO in bile indicate that bile excretion is the main pathway of ABZSO elimination. Based on the marker residue (ABZ-2-NH2-SO2) and its maximum residue limit (MRL) of 0.1 μg/g in skin-on muscle recommended by China, no withdrawal period was required for ABZ in Yellow River carp after a single oral dose of 12 mg/kg BW. However, using the marker residue (the sum of ABZ and its three metabolites) and the MRL of 0.1 μg/g for ruminants recommended by the EU, the withdrawal period was calculated to be 7 days or 118 °C-day under the same dosing regimen.

Effect of Body Size on Plasma and Tissue Pharmacokinetics of Danofloxacin in Rainbow Trout (Oncorhynchus mykiss)

Danofloxacin is a fluoroquinolone antibiotic approved for use in fish. It can be used for bacterial infections in fish of all body sizes. However, physiological differences in fish depending on size may change the pharmacokinetics of danofloxacin and therefore its therapeutic efficacy. In this study, the change in the pharmacokinetics of danofloxacin in rainbow trout of various body sizes was revealed for the first time. The objective of this investigation was to compare the plasma and tissue pharmacokinetics of danofloxacin in rainbow trout of different body sizes. The study was conducted at 14 ± 0.5 °C in fish of small, medium, and large body size and danofloxacin was administered orally at a dose of 10 mg/kg. Concentrations of this antimicrobial in tissues and plasma were quantified by high performance liquid chromatography with ultraviolet detector. The plasma elimination half-life (t1/2ʎz), volume of distribution (Vdarea/F), total clearance (CL/F), peak concentration (Cmax), and area under the plasma concentration-time curve (AUC0-last) were 27.42 h, 4.65 L/kg, 0.12 L/h/kg, 2.53 µg/mL, and 82.46 h·µg/mL, respectively. Plasma t1/2ʎz, AUC0-last and Cmax increased concomitantly with trout growth, whereas CL/F and Vdarea/F decreased. Concentrations in liver, kidney, and muscle tissues were higher than in plasma. Cmax and AUC0-last were significantly higher in large sizes compared to small and medium sizes in all tissues. The scaling factor in small, medium, and large fish was 1.0 for bacteria with MIC thresholds of 0.57, 0.79, and 1.01 µg/mL, respectively. These results show that therapeutic efficacy increases with body size. However, since increases in danofloxacin concentration in tissues of large fish may affect withdrawal time, attention should be paid to the risk of tissue residue.

In vitro antibacterial activity of danofloxacin against Escherichia coli in Gushi chickens and its residue depletion following multiple oral administration

This study aimed to investigate the in vitro antibacterial activity of danofloxacin against Escherichia coli isolated from Gushi chickens, as well as the tissue distribution and residue depletion of danofloxacin in Gushi chickens following multiple oral administration. A total of 42 clinical E. coli strains were isolated from the cloaca of locally farmed Gushi chickens between August and October 2023. Then the minimum inhibitory concentration (MIC) of danofloxacin against these isolates was determined by broth microdilution method. Additionally, 42 healthy Gushi chickens were randomly divided into 6 groups, and danofloxacin was orally administered at a dose of 5 mg/kg body weight (BW) for 3 consecutive days. Plasma, intestinal content, and tissue samples, including muscle, skin + fat, liver, kidney, lung, and intestine, were collected at 4, 12, 24, 48, 72, and 120 h after the last administration. Danofloxacin concentrations in all samples were determined using a high-performance liquid chromatography (HPLC) method. The average concentration vs. time data were then subjected to noncompartmental analysis using Phoenix software, and withdrawal periods for danofloxacin in Gushi chickens were further determined with WT1.4 software, setting a 95% confidence interval. Results indicated a notable inhibitory effect of danofloxacin on E. coli, with an MIC50 of 0.5 μg/mL. Additionally, danofloxacin exhibited widespread distribution in Gushi chickens, detectable in all collected samples. Among all tissues, the liver exhibited the highest concentration, followed by the intestine. Even on the fifth day postadministration, danofloxacin persisted in skin + fat, liver, and lung. The elimination half-lives (t1/2λzs) of danofloxacin varied across samples: skin + fat (47.87 h), lung (30.61 h), liver (22.07 h), plasma (16.05 h), muscle (12.53 h), intestine (9.83 h), and kidney (6.34 h). Considering residue depletion and the maximum residue limit (MRL) of danofloxacin in poultry set by Chinese regulatory authorities, withdrawal periods for the kidney, muscle, liver, and skin + fat were determined as 1.03, 1.38, 3.34, and 5.85 d, respectively, rounded to a final withdrawal time of 6 d.

Establishment and characterization of Yellow River carp (Cyprinus carpio haematopterus) muscle cell line and its application to fish virology and immunology

The Yellow River carp (Cyprinus carpio haematopterus) is a vital economically farmed fish of the Cyprinidae family. With the development of intensive aquaculture, carp production has increased dramatically, leading to the frequent occurrence of various diseases. Cell lines are considered the most cost-effective resource for in vitro studies and are widely used for physiological and pathological studies because of accessibility and convenience. This research established a novel immortal cell line CCM (Yellow River carp muscle cells) derived from the carp muscle. CCM has been passed over 71 generations for 1 year. The morphology of CCM and the adhesion and extension processes were captured by light and electron microscopy. CCM were passaged every 3 days with 20% FBS DMEM/F12 at 1:3. The optimum conditions for CCM growth were 28 °C and 20% FBS concentration. DNA sequencing of 16S rRNA and COI showed that CCM was derived from carp. CCM positively reacts to anti-PAX7 and anti-MyoD antibodies of carp. Analysis of chromosomes revealed that the chromosomal pattern number of CCM was 100. Transfection experiment demonstrated that CCM might be utilized to express foreign genes. Furthermore, cytotoxicity testing showed that CCM was susceptible to Aeromonas hydrophila, Aeromonas salmonicida, Aeromonas veronii, and Staphylococcus Aureus. The organophosphate pesticides (chlorpyrifos and glyphosate) or heavy metals (Hg, Cd, and Cu) exhibited dose-dependent cytotoxicity against CCM. After LPS treatment, the MyD88-IRAKs-NFκB pathway stimulates inflammatory-related factor il1β, il8, il10, and nfκb expression. LPS did not seem to cause oxidative stress in CCM, and the expression of cat and sod was not affected. Poly (I:C) through TLR3-TRIF-MyD88-TRAF6-NFκB and TRIF-TRAF3-TBK1-IRF3 activated the transcription of related factors, increased expression of anti-viral protein, but no changes in apoptosis-related genes. To our knowledge, this is the first muscle cell line in Yellow River carp and the first study on the immune response signal pathways of Yellow River carp based on the muscle cell line. CCM cell line provides a more rapid and efficient experimental material for fish immunology research, and this study preliminarily elucidated its immune response strategy to LPS and poly (I:C).

Population Pharmacokinetics of Difloxacin in Crucian Carp (Carassius auratus) after a Single Oral Administration

This study aimed to investigate the population pharmacokinetics of difloxacin in crucian carp (Carassius auratus) orally provided a single dose of 20 mg/kg body weight (BW). To achieve this, fish were sampled at various intervals using a sparse sampling strategy, and plasma samples were analyzed using the high-performance liquid chromatography (HPLC) method. Subsequently, naïve average data were analyzed using a non-compartmental method, and a population model was developed based on the nonlinear mixed effects approach. The covariate of BW and the relationship between covariances were sequentially incorporated into the population model. However, it was found that only covariance and not BW affected the population parameters. Therefore, the covariance model was taken as the final population model, which revealed that the typical values of the absorption rate constant (tvKa), apparent volume of distribution per bioavailability (tvV), and clearance rate per bioavailability (tvCl) were 1.18 1/h, 14.18 L/kg, and 0.20 L/h/kg, respectively. Based on the calculated free AUC/MIC values, the current oral dose of difloxacin (20 mg/kg BW) cannot generate adequate plasma concentrations to inhibit pathogens with MIC values above 0.83 μg/mL. Further study should be carried out to collect the pathogens from crucian carp and determine the MIC data of difloxacin against them. Pharmacodynamic experiments must also be further carried out to determine the optimal therapeutic dose for the treatment of Aeromonas hydrophila infection.

Pharmacokinetics of danofloxacin after single oral and intravenous administration in non-laying hens

The current study aimed to explore the pharmacokinetics of danofloxacin in non-laying hens after a single oral (PO) and intravenous (IV) dose, both at 5 mg/kg body weight (BW). Eighteen 13-week-old healthy hens were equally and randomly divided into two groups. After both doses, blood samples (approximately 1 ml) were collected at different time points. Danofloxacin concentrations were quantified by a validated high-performance liquid chromatography (HPLC) method followed by a non-compartmental analysis using the software of WinNonLin. The elimination half-lives (t1/2λz s) after PO and IV routes were determined as 8.15 ± 3.37 and 7.69 ± 3.40 h, respectively. After IV administration, danofloxacin had an initial concentration (C0 ) of 3.62 μg/ml, a volume of distribution at steady state (VSS ) of 3579.72 ± 454.29 ml/kg, and a total body clearance (Cl) of 0.49 ml/h/g. After PO administration, the absolute bioavailability and absorption half-life (t1/2ka ) were calculated as 100.99% ± 23.10% and 0.82 ± 0.58 h, respectively. Based on the calculated ratio values of AUC/MIC and Cmax /MIC, an oral dose of 5 mg/kg danofloxacin would be expected to successfully treat hens infected with strains with MIC values ≤0.1 μg/ml.