Pharmacokinetic/pharmacodynamic relationship of enrofloxacin against Aeromonas hydrophila in crucian carp (Carassius auratus gibelio)

Disruption of sex steroid hormones biosynthesis by short-term enrofloxacin antibiotic exposure in Carassius auratus var. Pengze

BACKGROUND

It has been reported that antibiotic enrofloxacin can impair reproductive function of mammals, induces multi-generational oscillatory effects on reproduction of Caenorhabditis elegans, and disturbes endocrine system in grass carp.

OBJECTIVES

This study aims to explore the effect of short-term enrofloxacin exposure on sex steroid hormones biosynthesis in Carassius auratus var. Pengze through assessing the contents of growth hormone (GH), thyroid hormone 4 (T4), estradiol (E2) and testosterone (T) in plasma, and investigating sex steroid hormones biosynthesis based on targeted metabonomics analysis, and determining expression level of some important genes, gonadotropin-releasing hormone (gnrh), gonadotropin hormone 1-β (gth1-β), gonadotropin hormone 2-β (gth2-β) and cyp19a1a in hypothalamus-pituitary-ovary axis (HPOA).

RESULTS

We found that short-term exposure of enrofloxacin disordered contents of E2 and T in plasma of fish determined by ELISA detection, T content elevation and E2 content decline, which was confirmed by the following data from targeted metabonomics analysis of plasma. The metabonomic results showed that both T and its upstream intermediate products during the process of sex steroid hormones biosynthesis in fish were increased significantly, but E2 content was decreased markedly. At the exposure 24 h of enrofloxacin, expression of gnrh in hypothalamus, gth1-β and gth2-β in pituitary were promoted. Meanwhile GH and T4 contents in plasma, two inducers of sex steroid hormones synthesis, were augmented, which indicated that sex steroid hormones biosynthesis was improved. However cyp19a1a expression in ovary was repressed, and content of estriol (E3) was upregulated. These data suggested that enrofloxacin promoted sex steroid hormones biosynthesis and conversion of E2 to estriol (E3), but inhibited the conversion of T to E2. Finally, content of E2 was declined sharply.

DISCUSSION

Animal specific antibacterial enrofloxacin is widely detectable in aquatic ecosystem, exposure of the agent can induce adverse effects on plants and animals. This study firstly evidenced induction of disruption of sex steroid hormones by enrofloxacin in fish, which indicates enrofloxacin is an endocrine disruption compound that can induce endocrine disruption of animals, including fish.

The Combination of β-Glucan and Astragalus Polysaccharide Effectively Resists Nocardia seriolae Infection in Largemouth Bass (Micropterus salmoides)

Effectively treating and preventing outbreaks is crucial for improving the economic benefits of aquaculture. Therefore, utilizing immunostimulants, either alone or in combination, is regarded as a promising strategy. In this study, β-glucan + APS (200 mg/kg + 200 mg/kg), β-glucan (200 mg/kg), APS (200 mg/kg), enrofloxacin (15 mg/kg), and sulfadiazine (15 mg/kg) were added to feed to assess the effects against Nocardia seriolae infection in largemouth bass (Micropterus salmoides) within 14 days. The survival rates did not differ between the enrofloxacin group and the β-glucan + APS group, but both were significantly higher than that of the control group. Additionally, the enrofloxacin group and the β-glucan + APS group exhibited the lowest bacterial loads and tissue damage. Importantly, the β-glucan + APS treatment significantly improved serum enzyme activities (total superoxide dismutase, lysozyme, total protein) and the expression of immune genes (IL-1β, TNF-α, IFN-γ, IgM) compared to the other treatment groups. The enrofloxacin group showed similar efficacy to the β-glucan + APS group in combating N. seriolae infection, but N. seriolae in the enrofloxacin group developed drug resistance. In summary, the combined use of β-glucan and APS is a promising strategy for treating bacterial diseases, thereby contributing to the promotion of sustainable aquaculture development.

Combined impacts of microplastics and cadmium on the liver function, immune response, and intestinal microbiota of crucian carp (Carassius carassius)

Microplastics (MPs) and the heavy metal cadmium (Cd) have attracted global attention for their toxicological interactions in aquatic organisms. The purpose of this investigation was evaluating the effect of MPs (1 mg L^-1) and Cd (5 mg L^-1) on the liver function, immune response of crucian carp (Carassius carassius) after 96 h exposure, and intestinal microbiota after 21 days, respectively. Co-exposure to MPs and Cd significantly enhanced MP accumulation in the liver of the crucian carp compared to the accumulation with exposure to MPs alone. Co-exposure to MPs and Cd triggered notable histopathological alterations accompanied by increased hepatic cell necrosis and inflammation, and was associated with higher aspartate aminotransferase and alanine aminotransferase levels, lower superoxide dismutase and catalase activity levels, but higher malondialdehyde content and total antioxidant capacity in the liver. Moreover, the combined treatment of MPs and Cd led to the up-regulated transcription of genes related to immune response, such as interleukin 8 (il-8), il-10, il-1β, tumor necrosis factor-α, and heat shock protein 70, both in the liver and spleen. Co-exposure to MPs and Cd reduced the variety and abundance of the intestinal microbiota in the crucian carp. Our research indicates that the combined exposure to MPs and Cd may exert synergistic toxic effects on crucian carp, which could impede the sustainable growth of the aquaculture industry and pose potential risks to food safety.

Plasma and tissue kinetics of enrofloxacin and its metabolite, ciprofloxacin, in yellow catfish (Pelteobagrus fulvidraco) after a single oral administration at different temperatures

The objective of this study was to examine the pharmacokinetic (PK) properties of enrofloxacin (EF) and its metabolite, ciprofloxacin (CF), in yellow catfish (Pelteobagrus fulvidraco) after a single oral dose of EF at 20 mg/kg at 20, 25, and 30 °C. Samples were collected at pre-designed time points and determined by high-performance liquid chromatography with a fluorescent detector. Results showed that most concentrations of EF and CF in plasma and tissues at the same time point at different temperatures were statistically significant. With the increase in temperature, the terminal half-life (T_1/2λz) of EF and CF was first reduced from 20 to 25 °C but elevated from 25 to 30 °C in plasma, muscle + skin, gill, liver, and kidney, respectively. The area under the plasma concentration-time curves (AUC_last) of EF were all decreased in plasma, muscle + skin, and gill except for that of EF in the liver and kidney. However, the AUC_last and the apparent metabolic rate of CF were exhibited first elevated and then decreased trend. The apparent volume of distribution (Vz_F) of EF was first reduced from 20 to 25 °C but increased at 30 °C. The apparent total body clearance (CL_F) of EF was increased from 0.15 to 0.32 L/h·kg with the temperature elevation. These indicated that increased temperature markedly affected the PKs of EF and CF in yellow catfish. Through in-depth analysis, the EF dosage of 20 mg/kg is appropriate to use in yellow catfish at 20 and 25 °C but 30 °C.

6His-tatritin promotes antimicrobial defense via regulating immune ability and intestinal microbial community in grass carp (Ctenopharyngodon idella)

Antimicrobial peptides are small, cationic, and amphiphilic peptides found in most organisms, and many of these peptides have broad antimicrobial activity against Gram-negative, -positive bacteria and fungi. In the present study, a derivative of antimicrobial peptide Tatritin, 6His-Tatritin, was designed and expressed by Pichia pastoris using a constitutive vector pGAPZαA with the promoter of pGAP. The 6His-Tatritin had a broad-spectrum antibacterial activity based on the Oxford cup method and the micro broth dilution test. In addition, to explore the role of 6His-Tatritin in vivo, grass carps (Ctenopharyngodon idellus) were infected with Aeromonas hydrophila after they were fed with 6His-Tatritin as feed additives for 28 days. The results revealed that 6His-Tatritin could significantly up-regulate the expression levels of Hepcidin, Leap-2b, Nrf-2, CuZn-SOD and LZM (P < 0.05). In addition, 6His-Tatritin could significantly reduce the mortality (P < 0.05) and the intestinal injury of grass carps infected with bacteria. The 16S sequencing analysis showed that the structure of microbial community in intestine of fish was more diversified compared with control after treatment with 6His-Tatritin. In summary, the peptide of 6His-Tatritin could promote antimicrobial defense via regulating immune ability and intestinal microbial community in grass carp. This study provides an effective method and approach for the application of antimicrobial peptide Tatritin in aquaculture, and also provides insights into the function of antimicrobial peptides in immunity against pathogens in fish.

Metabolism and residue differences of Enrofloxacin between the brain and peripheral tissues and the resulting brain damages in crucian carp (Carassius auratus var. Pengze)

This study aimed to explore the metabolism and residue differences of Enrofloxacin (ENR) at two doses between the brain and peripheral tissues (liver, kidney, and muscle) along with the brain damages caused by ENR in crucian carp (Carassius auratus var. Pengze). The concentrations of ENR in tissues were determined using a validated high-performance liquid chromatography (HPLC) analysis. Relying on the hematoxylin-eosin (HE) staining method, brain damages caused by the drug were evaluated by the section of pathological tissue. Metabolism and residue results showed that ENR could be detected in the brain throughout the experiment both at median lethal dose (LD₅₀ at 96 h, 1949.84 mg/kg) and safe dose (SD, 194.98 mg/kg), as well as in the three peripheral tissues. The maximum residue at LD₅₀ followed the decreasing order of liver >kidney > brain > muscle. Although the C_max of ENR at SD in the brain was significantly lower than that in other peripheral tissues (p < .05), it still reached 41.91 μg/g. The T_1/2 of ENR in brain tissue at the same dose was both shorter than that in peripheral tissues. At LD₅₀ , the amount of ENR residues in brain was lower than that in peripheral tissues on the whole, except that it had been higher than in the muscle for the first 3 h. At SD, the drug residue in brain tissue was lower than that in peripheral tissues from 12 h to 960 h, but it exceeded the muscle and kidney at 1 h and 6 h, respectively. At 960 h, the residual amount of ENR at SD in the brain was 0.09 μg/g, while it was up to 0.15 μg/g following the oral administration at LD₅₀ . Demonstrated by the HE staining, there were pathological lesions caused by ENR in the brain at LD₅₀ , which were characterized by sparse neural network and increased staining of glial cells. The present results indicated that metabolism and residue of ENR in crucian carp were affected by the tissue type and drug dosage, and the ENR could also bring about histopathological changes in the brain.

Plasma and muscle tissue disposition of enrofloxacin in Nile tilapia (Oreochromis niloticus) after intravascular, intraperitoneal, and oral administrations

The aim of the study was to investigate the plasma and muscle pharmacokinetic of enrofloxacin (ENR) and its active metabolite ciprofloxacin (CIP) in Nile tilapia (Oreochromis niloticus) following single intravascular (IV), intraperitoneal (IP), or oral (PO) administration at 30 ± 1 °C. In this study, 234 healthy Nile tilapia (120-150 g) were used. The fish received a single IV, IP, or PO treatment of ENR at a dose of 10 mg/kg. The plasma and muscle tissue concentrations of ENR and CIP were measured using high-performance liquid chromatography with fluorescence detection and were evaluated using non-compartmental analysis. The elimination half-life, volume of distribution at steady state, and total body clearance of ENR were 21.7 h, 2.69 L/kg, and 0.09 L/h/kg, respectively. The peak plasma concentrations of ENR after IP or PO administration were 6.11 and 4.21 µg/mL at 0.25 and 2 h, respectively. The bioavailability of ENR for IP or PO routes was 78% and 86%, respectively. AUC_{(0-120)muscle}/AUC_{(0-120)plasma} ratios following the IV, IP, or PO administrations were 1.43, 1.49, and 1.07, respectively. CIP was detected after all routes, but the AUC_0-last ratios of CIP to ENR were <1.0% for plasma and muscle. ENR was detected up to 120 h following the IV, IP, or PO administrations. The long residence time of ENR after single IV, IP, or PO administration ensured the plasma concentration was ≥1 × MIC for bacteria with threshold MIC values of 0.92, 0.72, and 0.80 μg/mL over the whole 120 h observed. However, further studies are necessary to determine the optimum pharmacokinetic/pharmacodynamics data of ENR for the treatment of infections caused by susceptible bacteria in tilapia.

Pharmacokinetics and Tissue Residue Profiles of Enrofloxacin in Crucian Carp (Carassius auratus gibelio) Following Single and Multiple Oral Administration

The pharmacokinetics, tissue distribution, and elimination of enrofloxacin (ENR) and its metabolite ciprofloxacin (CIP) were investigated to the crucian carp (Carassius auratus gibelio) after single (20 mg/kg b. w.) and multiple oral administration (20 mg/kg b.w. one time daily for 5 days) at 28°C. The concentrations of ENR and CIP in the plasma and tested tissues (muscle/skin, liver, and kidney) were detected simultaneously by high-performance liquid chromatography (HPLC), and the pharmacokinetic data were analyzed with a non-compartmental model using WinNonLin 6.1 PK software (Pharsight Corporation, Mountain View, CA, USA). The pharmacokinetic characteristics of ENR in crucian carp exhibited slow absorption, wide tissue distribution, and long elimination half-life. In the single-dose group, the peak concentrations (Cmax) of ENR in the plasma, muscle/skin, liver, and kidney were 8.93 μg/mL, 13.9 μg/g, 31.2 μg/g, and 27.3 μg/g, respectively, observed at 3 h, 6 h, 1 h, and 3 h after dosing. The elimination half-lives (T1/2λz ) of ENR in plasma, muscle/skin, liver, and kidney were calculated to be 67.4, 82.8, 94.4, and 114 h, respectively. In the multiple-dose group, the Cmax of ENR in the plasma, muscle/skin, liver, and kidney were 18.4 μg/mL, 26.8 μg/g, 82.8 μg/g, and 74.5 μg/g, respectively, achieved at 3 h, 6 h, 1 h, and 1 h after the last dose. The T1/2λz of ENR in the plasma, muscle/skin, liver, and kidney were calculated to be 76.4 h, 91.5 h, 114 h, and 148 h, respectively. During the multiple-dose administration, significant accumulations of ENR and CIP were observed in the plasma and tissues of crucian carp, possibly due to their long elimination half-lives. In both dose groups, the AUC0-∞ for both ENR and CIP followed the order of liver > kidney > muscle/skin > plasma. The finding suggested that the liver may play an important role in the metabolism of ENR. According to the calculated PK/PD indices of Cmax/minimum inhibitory concentrations (MIC) and AUC24h/MIC, the multiple-dose regimen would be highly effective against pathogenic bacteria with a MIC value of ≤ 1.84 μg/ml. Depletion studies indicated that a withdrawal period of at least 29 or 32 days was necessary to guarantee food security after single or multiple oral gavage administration at 28°C.

Development and application of a physiologically based pharmacokinetic model for orbifloxacin in crucian carp (Carassius auratus)

A flow-limited physiologically based pharmacokinetic (PBPK) model consisting of seven compartments was established for orbifloxacin in crucian carp to predict drug concentrations after intravenous or intramuscular injections. Physiological and anatomical parameters, including tissue weights and blood flow through different tissues, were obtained from previous literature. The tissue/plasma partition coefficients for orbifloxacin were calculated using the area method or parameter optimization. In addition, their values were 0.9326, 1.1204, 1.1644, 1.3514, and 2.0057 in the liver, skin, muscle, kidney, and the rest of the body compartment, respectively. Based on the current PBPK model, orbifloxacin concentrations were predicted and compared with those previously reported for further validation. In addition, the mean absolute percentage error (MAPE) values were also calculated, with values ranging from 10.21% in plasma to 42.37% in kidneys, indicating acceptable predictions for all tissues and plasma. A local sensitivity analysis was performed, which showed that the parameters related to elimination and distribution were most influential on orbifloxacin concentrations in muscle. This model was finally used to predict plasma and tissue concentrations after multiple intramuscular dosing. The current PBPK model provided a valuable tool for predicting the tissue residues of orbifloxacin in crucian carp following intramuscular injection.

Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Integration of Enrofloxacin Following Single Oral Administration of Different Doses in Brown Trout (Salmo trutta)

Simple Summary

The pharmacokinetic/pharmacodynamic studies report the use of enrofloxacin at higher doses than 10 mg/kg in fish. Pharmacokinetic data for increasing doses of enrofloxacin can facilitate suggestions regarding the dose for the treatment of infections in brown trout. This study aims to determine single oral pharmacokinetics of enrofloxacin at 10, 20, and 40 mg/kg doses in brown trout and pharmacodynamics against Aeromonas hydrophila and A. sobria. Enrofloxacin exhibited non-linear and dose-disproportional pharmacokinetics. The long action of enrofloxacin following the single oral administration at 10 and 20 mg/kg doses may provide the unique dosage regimen to minimize handling, thereby reducing the cost of administration and stress in brown trout.

Abstract

The pharmacokinetic of enrofloxacin was investigated in brown trout (Salmo trutta) following oral administration of 10, 20, and 40 mg/kg doses at 11 ± 1.5 °C. Furthermore, MICs of enrofloxacin against Aeromonas hydrophila and A. sobria were determined. The plasma concentrations of enrofloxacin and ciprofloxacin were determined using HPLC–UV and analyzed by non-compartmental method. Following oral administration at dose of 10 mg/kg, total clearance (CL/F), area under the concentration–time curve (AUC_0−∞) and peak plasma concentrations (C_max) were 41.32 mL/h/kg, 242.02 h*μg/mL and 4.63 μg/mL, respectively. When compared to 10 mg/kg dose, the dose-normalized AUC_0–∞ and C_max were increased by 56.30% and 30.08%, respectively, while CL/F decreased by 38.4% at 40 mg/kg dose, suggesting the non-linearity. Ciprofloxacin was not detected in the all of plasma samples. The MIC values of enrofloxacin were ranged 0.0625–4 μg/mL for A. hydrophila and 0.0625–2 μg/mL for A. sobria. The oral administration of enrofloxacin at 10 (for 192 h) and 20 (for 240 h) mg/kg doses provided the AUC of enrofloxacin equal to 1.23 and 1.96-fold MICs, respectively, for A. hydrophila and A. sobria with the MIC₉₀ values of 1 µg/mL. However, further researches are needed on the PK/PD study of enrofloxacin for the successful treatment of infections caused by A. hydrophila and A. sobria in brown trout.

Determination of Pharmacokinetic and Pharmacokinetic-Pharmacodynamic Parameters of Doxycycline against Edwardsiella ictaluri in Yellow Catfish (Pelteobagrus fulvidraco)

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 (AUC_0-96) values were considerably increased in gill, kidney, muscle and skin, and plasma, except in liver. C_max 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 AUC_0-96 to minimum inhibitory concentration (AUC_0-96h/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 AUC_0-96h/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 AUC_0-96h/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.

Pharmacokinetic-pharmacodynamic modelling for the determination of optimal dosing regimen of florfenicol in Nile tilapia (Oreochromis niloticus) at different water temperatures and antimicrobial susceptibility levels

Optimized dosing regimen is key to the effective use of antibacterials and to minimizing drug-related side effects. The current study established a pharmacokinetic-pharmacodynamic (PK-PD) model for the determination of optimal antibacterial dosing regimen in fish taken into consideration the temperature-dependent PK and the pathogen-dependent antimicrobial susceptibility, using florfenicol (FF) in Nile tilapia as an example. The calculated optimal dosages significantly varied by temperature and target MIC levels, ranging from 2.23 (MIC 1 µg/ml at 24°C) to 34.88 mg kg^-1  day^-1 (MIC 4 µg/ml at 32°C). The appropriateness of the calculated dosages was successfully verified by the in vivo studies. After 5 days of oral administration of the calculated optimal dosage at 24°C, the predicted plasma drug values were in line with the mean observed C_min(ss) while at 28 and 32°C underestimation of the C_min(ss) in a dose-dependent manner was observed and likely due to the occurrence of non-linear PK at high dosages. The averaged serum protein binding of FF was 19.1%. Our results demonstrated the appropriateness and clinical applicability of the developed PK-PD approach for the determination of optimal dosing regimens at given temperatures and MICs. Saturation metabolism and PK non-linearity of FF in tilapia warrant further study.

Pharmacokinetics and tissue residues of enrofloxacin in the largemouth bass (Micropterus salmoides) after oral administration

The study was carried out to evaluate the pharmacokinetic disposition of enrofloxacin (ENF) with a single dose of 20 mg/kg after oral administration in largemouth bass (Micropterus salmoides) at 28°C. The concentrations of ENF and of its metabolite ciprofloxacin (CIP) in plasma, liver, and muscle plus skin in natural proportions were determined using HPLC. The concentration-time data for ENF in plasma were best described by a two-compartment open model. After oral administration, the maximum ENF concentration (C_max ) of 10.99 μg/ml was obtained at 0.60 hr. The absorption half-life (T_1/2Ka ) of ENF was calculated to be 0.07 hr whereas the elimination half-life (T_1/2β ) of the drug was 90.79 hr. The estimates of area under the plasma concentration-time curve (AUC) and apparent volume of distribution (Vd/F) were 1,185.73 μg hr/ml and 2.21 L/kg, respectively. ENF residues were slowly depleted from the liver and muscle plus skin of largemouth bass with the T_1/2β of 124.73 and 115.14 hr, respectively. Very low levels of ciprofloxacin were detected in the plasma and tissues. A withdrawal time of 24 days was necessary to ensure that the residues of ENF + CIP in muscle plus skin were less than the maximal residue limit (MRL) of 100 μg/kg established by the European Union.