Withdrawal time of four pharmaceutical formulations of enrofloxacin in poultry according to different maximum residues limits

Assessment of Enrofloxacin Usage and Residue Levels of Enrofloxacin-Ciprofloxacin in Breast and Liver Tissues of Commercial Broilers Sold in Kampala-Uganda

Background

Human exposure to veterinary drugs like fluoroquinolones occurs due to the presence of their residues in foods from animal sources in varying concentrations. The existence of antibiotic residues in foodstuffs can pose great public health problems to consumers. This study aimed to assess enrofloxacin use patterns and assess residue levels of enrofloxacin/ciprofloxacin in breast muscle and liver tissues of broiler chickens sold for consumption in Kampala capital city.

Methods

This was a cross-sectional study that involved both field survey and laboratory-based methods. The field study involved the use of qualitative and semi-quantitative data collection tools to interview 34 broiler farmers and 10 veterinary drugs vendors. For the determination of enrofloxacin/ciprofloxacin levels, 68 chicken breast and liver tissue samples were collected from main markets in Kampala over one month and analyzed using HPLC-UV.

Results

Enrofloxacin was the most used antibiotic (100%) for the management of poultry diseases, majorly respiratory diseases (100%), salmonella infections (40%), and disease prevention (60%). Over 76% of the farmers knew the meat withdrawal time (WDT) for enrofloxacin, but none of them adhered to this. Over 70% of the farmers reported that the veterinary drugs vendors were not providing meat WDT information. Enrofloxacin/ciprofloxacin residues were identified in 35.3% (12/34) of the muscle and 38.2% (13/34) of the liver tissues analyzed. Of those muscle and liver tissue samples that tested positive, 25% (3/12) and 38.5% (5/13) respectively had drug concentrations higher than the recommended Maximum Residue Limits. The overall mean enrofloxacin/ciprofloxacin concentration in the chicken muscle and liver tissues was 83.6 (±34.5) µg/kg and 171.5 (±75.9) µg/kg.

Conclusion

This observed presence of enrofloxacin/ciprofloxacin levels above safety requirements is attributable to inadequate medicines use information provided by veterinary drugs vendors to farmers and also to the non-compliance of some farmers to meat WDT due to the economic implications.

Occurrence and Risk Assessment of Fluoroquinolone Residues in Chicken and Pork in China

Antibiotics, especially fluoroquinolones, have been exhaustively used in animal husbandry. However, very limited information on the occurrence and exposure assessment of fluoroquinolone residues in chicken and pork in China is available to date. Thus, a total of 1754 chicken samples and 1712 pork samples were collected from 25 provinces in China and tested by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS) for residual determination of six common fluoroquinolones. The results revealed that the detection frequencies of fluoroquinolone residues were 3.99% and 1.69% in chicken and pork samples. The overall violation frequencies were 0.68% and 0.41% for chicken and pork. Enrofloxacin and its metabolite ciprofloxacin were found to be the most predominant fluoroquinolones. The occurrence of these antibiotics in different sampling regions and market types was analyzed. The %ADI values of enrofloxacin and ciprofloxacin were far less than 100, indicating the health risk associated with the exposure to these aforementioned fluoroquinolone residues via chicken and pork for Chinese children, adolescents, and adults was acceptable. The results provided useful references for Chinese consumers, and helped to appropriately use these antibiotics in poultry and livestock industry.

Fluorescence Polarization Immunoassay for Determination of Enrofloxacin in Pork Liver and Chicken

Enrofloxacin (ENR) is a widely used fluoroquinolone (FQ) antibiotic for antibacterial treatment of edible animal. In this study, a rapid and highly specific fluorescence polarization immunoassay (FPIA) was developed for monitoring ENR residues in animal foods. First, ENR was covalently coupled to bovine serum albumin (BSA) to produce specific polyclonal antibodies (pAbs). Three fluorescein-labeled ENR tracers (A, B, and C) with different spacers were synthesized and compared to obtain higher sensitivity. Tracer C with the longest arm showed the best sensitivity among the three tracers. The developed FPIA method showed an IC₅₀ (50% inhibitory concentration) of 21.49 ng·mL⁻¹ with a dynamic working range (IC₂₀–IC₈₀) of 4.30–107.46 ng·mL⁻¹ and a limit of detection (LOD, IC₁₀) of 1.68 ng·mL⁻¹. The cross-reactivity (CR) of several structurally related compounds was less than 2%. The recoveries of spiked pork liver and chicken samples varied from 91.3% to 112.9%, and the average coefficients of variation were less than 3.83% and 5.13%, respectively. The immunoassay took only 8 min excluding sample pretreatment. This indicated that the established method had high sensitivity, specificity, and the advantages of simplicity. Therefore, the proposed FPIA provided a useful screening method for the rapid detection of ENR residues in pork liver and chicken.

Clinical Efficacy and Residue Depletion of 10% Enrofloxacin Enteric-Coated Granules in Pigs

A new, more palatable formulation of 10% enrofloxacin enteric-coated granules was investigated to evaluate the pharmacokinetic effect in plasma, the residue elimination in tissues and the clinical efficacy against Actinobacillus pleuropneumonia (APP) and Mycoplasam suis (MS) in pigs. In this study, the enrofloxacin concentrations in plasma and tissues were detected using high-performance liquid chromatography with phosphate buffer (pH = 3) and acetonitrile. The pharmacokinetics and elimination of enrofloxacin enteric-coated granules were performed after oral administration at a single dose of 10 mg/kg body weight (bw) and 5 mg/kg twice per day for 5 consecutive days, respectively. The in vivo antibacterial efficacy and clinical effectiveness of enrofloxacin enteric-coated granules against APP and MS were assayed at 2.5, 5, 10 mg/kg, compared with tiamulin (8 mg/kg) based on establishment of APP and MS infection models. 56 APP strains were selected and tested for in vitro antibacterial activity of enrofloxacin enteric-coated granules. The main parameters of elimination half-life (t_1/2β), T_max, and area under the curve (AUC) were 14.99 ± 4.19, 3.99 ± 0.10, and 38.93 ± 1.52 μg h/ml, respectively, revealing that the enrofloxacin concentration remained high and with a sustainable distribution in plasma. Moreover, the analysis on the evaluation of enrofloxacin and ciprofloxacin in muscle, fat, liver and kidney showed that the recovery were more than 84% recovery in accordance with the veterinary drug residue guidelines of United States pharmacopeia, and the withdrawal periods were 4.28, 3.81, 4.84, and 3.51 days, respectively, suggesting that the withdrawal period was 5 d after oral administration of 5 mg/kg twice per day. The optimal dosage of enrofloxacin enteric-coated granules against APP and MS was 5 mg/kg, with over 90% efficacy, which was significantly different (p < 0.05) to the 2.5 mg/kg group, but not to the 10 mg/kg group or the positive control group (tiamulin). In conclusion, 10% enrofloxacin enteric-coated granules had significant potential for treating APP and MS, and it provided an alternative enrofloxacin palatability formulation.

Residue depletion of oxytetracycline (OTC) and 4-epi-oxytetracycline (4-epi-OTC) in broiler chicken's claws by liquid chromatography-tandem mass spectrometry (LC-MS/MS)

Antibiotics are widely used in poultry production for the treatment of bacterial diseases. However, residues may remain in products and by-products destined for human consumption or animal feeding. The claws of chickens, which are a by-product of the poultry industry, can directly or indirectly enter the food chain as meals destined to feed other productive animals. Thus, it becomes necessary to determine and quantify antimicrobial residues present in this matrix. The objective of the study was to assess the depletion of oxytetracycline (OTC) and its metabolite 4-epi-OTC in broiler chicken's claws. Claws of 32 broilers treated with a therapeutic dosage of 10% OTC during 7 days were analysed. Samples were taken at days 3, 9, 15 and 19 post-treatment. As for the control group, eight broiler chickens were raised under the same conditions. Extraction was carried out through EDTA-McIlvaine buffer, and clean-up employed a SPE C-18 Sep-Pak®. Instrumental analysis was performed through LC-MS/MS. The concentrations of both analytes were determined in claw samples until day 19 post-treatment. Average concentrations were within the LOD (20 μg kg^-1) and LOQ (22 µg kg^-1) for OTC and 84 μg kg^-1 for 4-epi-OTC. Withdrawal times (WDTs) of 39 days for OTC and 54 days for 4-epi-OTC were established in claws based on 95% confidence. These findings demonstrate that claws can be a source of antimicrobial residue entry into the food chain, since the results showed that OTC and its metabolite can be found in chicken's claws for long periods, even exceeding the average lifespan of a broiler chicken.

Investigation of enrofloxacin residues in broiler tissues using ELISA and LC-MS/MS

This study investigated the efficiency of an enrofloxacin ELISA test kit to detect the presence of enrofloxacin residues in broiler tissues compared with LC-MS/MS. Broiler tissues from 72 samples consisting of 60 breast muscle, six pools of livers (500 g each) and six pools of kidneys (500 g each) were obtained from six different slaughterhouses. Breast muscle from 10 carcasses and pools of livers and kidneys from approximately 200 carcasses of the same flock were collected from each slaughterhouse. ELISA and HPLC were used to identify and quantify the contamination of the samples with enrofloxacin. A total of 72% of the analysed samples contained enrofloxacin residues detected by the ELISA and 22.2% were detected by LC-MS/MS. The mean values of enrofloxacin contamination found in chicken breast by ELISA and HPLC were 8.63 and 12.25 μg kg(-1), respectively. None of the samples exceeded the maximum limit of 100 μg kg(-1) by both methods set by the European Union as well as the Brazilian Agriculture Ministry. All positive samples for enrofloxacin residues detected by LC-MS/MS were also positive by ELISA. These data confirm the efficiency of the ELISA test, and suggest its use as a screening method for enrofloxacin residues in poultry tissues due to its quick results, low price and ease of applicability.

Investigation of enrofloxacin and chloramphenicol residues in broiler chickens carcasses collected from local markets of tabriz, northwestern iran

BACKGROUND

The present study was aimed to determine the residual amounts of chloramphenicol and enrofloxacin in broiler chickens muscle and liver sam-ples gathered from local markets of Tabriz City, northwestern Iran.

METHODS

Ninety broiler chickens carcasses were collected from different local markets of Tabriz, during July/August 2013. Random samples of thigh and breast muscle and liver were gathered and kept at -80(°)C until analyzes. The samples were then assayed using enzyme-linked immunosorbent assay (ELISA) according to the protocol of each antibiotic kit. Data were statistically analyzed using the computer program SAS 9.1.

RESULTS

Eighty two samples (91/1 %) contained residues of enrofloxacin, alt-hough mean (±SD)of enrofloxacin concentration was lower than the European Union maximum residue limits(MRLs) value (P<0.001). Moreover, 28 (31/1 %) had detectable concentrations of chloramphenicol while it was not defined any MRLs value for chloramphenicol because its using has been forbidden in food animals.

CONCLUSION

The frequency of contamination with enrofloxacin was considerable for the analyzed samples. Furthermore, the existence of chloramphenicol in almost one third of samples seems to be a public health threat due to its illegal use in food animals including poultry.

Physicochemical characterization and pharmacokinetics in broiler chickens of a new recrystallized enrofloxacin hydrochloride dihydrate

Enrofloxacin, a key antimicrobial agent in commercial avian medicine, has limited bioavailability (60%). This prompted its chemical manipulation to yield a new solvate-recrystallized enrofloxacin hydrochloride dihydrate entity (enroC ). Its chemical structure was characterized by means of mass spectroscopy, Fourier transformed infrared spectroscopy, X-ray powder diffraction, and thermal analysis. Comparative oral pharmacokinetics (PK) of reference enrofloxacin (enroR ) and enroC in broiler chickens after oral administration revealed noticeable improvements in key parameters and PK/PD ratios. Maximum serum concentration values were 2.61 ± 0.21 and 5.9 ± 0.42 μg/mL for enroR and enroC , respectively; mean residence time was increased from 5.50 ± 0.26 h to 6.20 ± 0.71 h and the relative bioavailability of enroC was 336%. Considering Cmax /MIC and AUC/MIC ratios and the MIC values for a wild-type Escherichia coli O78/H12 (0.25 μg/mL), optimal ratios will only be achieved by enroC (Cmax /MIC = 23.6 and AUC/MIC = 197.7 for enroC ; vs. Cmax /MIC = 10.4 and AUC/MIC = 78.1 for enroR ). Furthermore, enroC may provide in most cases mutant prevention concentrations (Cmax /MIC ≥ 16). Ready solubility of powder enroC in drinking water at concentrations regularly used (0.01%) to provide an additional advantage of enroC in the field. Further development of enroC is warranted before it can be recommended for clinical use in veterinary medicine.

Optimization of condition for conjugation of enrofloxacin to enzymes in chemiluminescence enzyme immunoassay

In this study, in order to find out a proper method for conjugation of enrofloxacin to label enzymes, two methods were compared and carbodiimide condensation was proved to be better. The results showed that the binding ratio of enrofloxacin and alkaline phosphatase (ALP) was 8:1 and that of enrofloxacin and horseradish peroxidase (HRP) was 5:1. This indicated that conjugate synthesized by carbodiimide condensation was fit for chemiluminescence enzyme immunoassay (CLEIA). Furthermore, data revealed that dialysis time was an important parameter for conjugation and 6days was best. Buffer to dilute conjugate had little effect on CLEIA. The storage condition for conjugates was also studied and it was shown that the conjugate was stable at 4°C with no additive up to 30days. These data were valuable for establishing CLEIA to quantify enrofloxacin.

Integrated pharmacokinetics/pharmacodynamics parameters-based dosing guidelines of enrofloxacin in grass carp Ctenopharyngodon idella to minimize selection of drug resistance

BACKGROUND

Antibiotic resistance has become a serious global problem and is steadily increasing worldwide in almost every bacterial species treated with antibiotics. In aquaculture, the therapeutic options for the treatment of A. hydrophila infection were only limited to several antibiotics, which contributed for the fast-speed emergence of drug tolerance. Accordingly, the aim of this study was to establish a medication regimen to prevent drug resistant bacteria. To determine a rational therapeutic guideline, integrated pharmacodynamics and pharmacokinetics parameters were based to predict dose and dosage interval of enrofloxacin in grass carp Ctenopharyngodon idella infected by a field-isolated A. hydrophila strain.

RESULTS

The pathogenic A. hydrophila strain (AH10) in grass carp was identified and found to be sensitive to enrofloxacin. The mutant selection window (MSW) of enrofloxacin on isolate AH10 was determined to be 0.5-3 μg/mL based on the mutant prevention concentration (MPC) and minimum inhibitory concentration (MIC) value. By using high-performance liquid chromatography (HPLC) system, the Pharmacokinetic (PK) parameters of enrofloxacin and its metabolite ciprofloxacin in grass carp were monitored after a single oral gavage of 10, 20, 30 μg enrofloxacin per g body weight. Dosing of 30 μg/g resulted in serum maximum concentration (Cmax) of 7.151 μg/mL, and concentration in serum was above MPC till 24 h post the single dose. Once-daily dosing of 30 μg/g was determined to be the rational choice for controlling AH10 infection and preventing mutant selection in grass carp. Data of mean residue time (MRT) and body clearance (CLz) indicated that both enrofloxacin and its metabolite ciprofloxacin present similar eliminating rate and pattern in serum, muscle and liver. A withdraw time of more than 32 d was suggested based on the drug eliminating rate and pharmacokinetic model described by a polyexponential equation.

CONCLUSIONS

Based on integrated PK/PD parameters (AUC/MIC, Cmax/MIC, and T>MPC), the results of this study established a principle, for the first time, on drawing accurate dosing guideline for pharmacotherapy against A. hydrophila strain (AH10) for prevention of drug-resistant mutants. Our approach in combining PK data with PD parameters (including MPC and MSW) was the new effort in aquaculture to face the challenge of drug resistance by drawing a specific dosage guideline of antibiotics.

Effects of aflatoxin B1 on tissue residues of enrofloxacin and its metabolite ciprofloxacin in broiler chickens

The impact of subchronic exposure of aflatoxin B1 on the tissue residues of enrofloxacin and its metabolite ciprofloxacin was examined in broiler chickens. Broiler chickens given either normal or aflatoxin B1 (750 μg/kg diet) supplemented diets for 6 weeks received enrofloxacin (10 mg/kg/day, p.o.) for 4 days and thereafter, residue levels were determined. Aflatoxin B1 induced alterations in serum marker enzymes. As compared to unexposed broiler chickens, enrofloxacin concentrations in aflatoxin B1-exposed broiler chickens were significantly higher in all tissues (0.62-4.53 μg/g) analyzed except muscle 24h after termination of enrofloxacin administration. Ciprofloxacin was detectable in tissues of only mycotoxin-exposed broiler chickens. Enrofloxacin residues in liver, kidney and skin plus fat persisted for 10 days in mycotoxin-exposed broiler chickens whereas it was detectable only in liver of unexposed broiler chickens. Our results indicate that subchronic aflatoxin B1 exposure markedly influences the residue levels of enrofloxacin and ciprofloxacin in tissues of broiler chickens.

A sensitive chromatographic strip test for the rapid detection of enrofloxacin in chicken muscle

A sensitive colloidal gold immunochromatography assay using a specific monoclonal antibody was developed for the rapid detection of enrofloxacin (ENR) residues in chicken muscles. Anti-ENR antibodies with high sensitivity and specificity are generated by immunising BALB/c mice with well-characterised ENR-bovine serum albumin conjugate. An orthogonal L₉(3)³ test was designed, and various parameters that influenced the assay performance were investigated and optimised. Under the optimised conditions, the cut-off limits of semi-quantitative test strips for ENR were found to be 3 ng/mL in phosphate-buffered saline and 8 µg/kg in chicken muscle. The ENR test strips showed a 6% cross-reactivity with ciprofloxacin, 3% with norfloxacin, less than 1% with ofloxacin and sarafloxacin and 0.1% with the other eight fluoroquinolones including enoxacin, difloxacin, danofloxacin, pefloxacin, lomefloxacin, sparfloxacin, oxolinic acid and flumequine. Consistent results are produced from the parallel analysis of ENR-contaminated chicken muscle extracts using test strips and ELISA.

Evaluation of linear regression statistical approaches for withdrawal time estimation of veterinary drugs

The safety of foods of animal origin requires the determination of the time at which veterinary drug residues in edible tissues are below a given maximum residue limit (MRL). For this reason, a certain withdrawal time estimate is determined for drugs based on statistical evaluation of concentrations determined by analytical analysis of residues in target organs of healthy animals. The purposes of this paper is to evaluate the linear regression statistical approach for the estimation of withdrawal time of veterinary drugs as recommended by Food and Drug Administration (FDA) and European Union/Committee for Medicinal Products for Veterinary use (EU/CVMP) and compare the application with a real model example. The withdrawal time estimate of the model has shown 2-5 days difference for the increase in tolerance limit from 95% (EU) to 99% (FDA) when calculated including censored data. But when it was excluded the range increased to 2-8 days for the same increase in tolerance. Furthermore, wider range of difference (3-21 days) and variation in significance was observed with inclusion/exclusion of censored data at the same level of tolerance. In conclusion, this study suggests inclusion/exclusion of censored data should be dependent on satisfying the statistical assumptions required rather than always including/excluding.