Pharmacokinetics of veterinary drugs in laying hens and residues in eggs: a review of the literature

Transfer and risk assessment of fipronil in laying hen tissues and eggs

Fipronil is a persistent insecticide known to transfer into hen eggs from exposure from animal drinking water and feed, but some questions remain regarding its transfer behavior and distribution characteristics. Therefore, the dynamic metabolism, residue distribution and transfer factor (TF) of fipronil were investigated in 11 edible tissues of laying hens and eggs over 21 days. After a continuous low-dose drinking water exposure scenario, the sum of fipronil and all its metabolites (defined as fipronilT) quickly transferred to each edible tissue and gradually increased with exposure time. FipronilT residue in eggs first appeared at 3 days and then gradually increased. After a single high-dose feed exposure scenario, fipronilT residue in edible tissues first appeared after 2 h, quickly peaked at 1 day, and then gradually decreased. In eggs, fipronilT residue first appeared at 2 days, peaked 6-7 days and then gradually decreased. The TF values followed the order of the skin (0.30-0.73) > egg yolk (0.30-0.71) > bottom (0.21-0.59) after drinking water exposure, and the order of the skin (1.01-1.59) > bottom (0.75-1.1) > egg yolk (0.58-1.10) for feed exposure. Fipronil sulfone, a more toxic compound, was the predominant metabolite with higher levels distributed in the skin and bottom for both exposure pathways. FipronilT was distributed in egg yolks rather than in albumen owing to its lipophilicity, and the ratio of egg yolk to albumen may potentially reflect the time of exposure. The distinction is that the residues after feed exposure were much higher than that after drinking water exposure in edible tissues and eggs. The study highlights the residual characteristics of two exposure pathways, which would contribute to the tracing of contamination sources and risk assessment.

Population Pharmacokinetics and Absolute Oral Bioavailability of Lasalocid after Single Intravenous and Intracrop Administration in Laying Hens

Lasalocid sodium is a polyether carboxylic ionophore agent authorized by the EU for use as a coccidiostat in broilers, turkeys, and pullets up to 16 weeks of age, except for laying hens. However, laying hens are the most common nontarget species exposed to lasalocid sodium, mainly due to cross-contamination from feed mills. This exposure may result in potential drug residue deposition in eggs, which could potentially expose consumers to the drug. The breeds commonly used for commercial egg production in Poland are Isa Brown and Green-legged Partridge hens, which have been found to significantly differ in egg-laying performance. This variability may also affect the pharmacokinetics of lasalocid. Data on lasalocid plasma pharmacokinetics in laying hens are lacking. In this study, we aimed to determine typical population pharmacokinetic parameters, absolute oral bioavailability, and how breed may influence the pharmacokinetics of lasalocid. Twenty-layer hens of the two breeds were used in this study. Lasalocid was administered orally at a single dose of either 1 mg or 5 mg/kg body weight or intravenously at a dose of 1 mg/kg body weight, in a crossover design with a three-week washout period between study periods. Blood samples were collected for 72 h, and lasalocid concentrations were measured using high-performance liquid chromatography with fluorescence detection. A population pharmacokinetic analysis was conducted using nonlinear mixed effects modeling. Standard numerical and graphical criteria were used to select the best model, and a stepwise covariate modeling approach was used to determine any influencing factors. The best model was a three-compartment mammillary model with first-order absorption, transit compartments, and linear elimination. The estimated absolute oral bioavailability was low (36%). It was found that breed significantly influenced not only absorption but also the elimination of lasalocid. This study revealed that lasalocid absorption and elimination varied between the two breeds. This variability in pharmacokinetics may result in breed-related differences in drug residue accumulation in eggs, and ultimately, the risk associated with consumer exposure to drug residues may also vary.

Efficient detection of aklomide/nitromide based on a sensor of MPA capped CdTe QDs using fluorescence quenching method

Based on the fluorescence sensor of 3-Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs), two novel detection methods for aklomide and nitromide were developed. The MPA-CdTe QDs were synthesized and characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), ultraviolet visible (UV-vis) and fluorescence (FL). The quenchings were all static. The binding constants (Ka) at different temperatures were obtained. Electrostatic forces were the main forces for the two bindings. For the detection of aklomide and nitromide, under the optimal conditions, the effects of some metal ions, glucose, bovine serum albumin (BSA) and congeneric drug on the determination were explored. The standard equations were established and the limits of detection (LOD) were 0.0215 and 0.0388 μg mL-1 (3S0/S), repectively. The methods were applied to analyse the samples of chicken and duck, the recoveries were 99.41 % - 101.24 % with RSDs of 0.29 % - 1.19 % (n = 5).

Unravelling taboos and cultural beliefs associated with hidden hunger among pregnant and breast-feeding women in Buyende district Eastern Uganda

BACKGROUND

Food taboos and cultural beliefs among pregnant and breast-feeding women influence their food consumption patterns and hence the health of women and unborn children. Cognizant of their neglect in programs aimed to ameliorate hidden hunger among pregnant and breast-feeding women in Buyende and other resource-poor communities in sub-Saharan Africa, we opted for a study to unravel them to inform program design.

METHODS

We documented food taboos and beliefs amongst pregnant and breast-feeding women from six sub-counties of Buyende district in Eastern Uganda. A mixed-methods approach was used, which was comprised of questionnaire interviews with 462 women, eight focus group discussions with 6-10 participants in each and a total of 15 key informant interviews.

RESULTS

The present study revealed that 129 (27.9%) of the respondents practice food taboos and adhere to cultural beliefs related to their dietary habits during pregnancy and breast-feeding that are fuelling the prevalence of hidden hunger. The most tabooed foods during pregnancy were sugarcane (17.8%), fishes which included lung fish, catfish and the Lake Victoria sardine (Rastrineobola argentea) (15.2%), oranges (6.6%), pineapples (5.9%), eggs (3.3%), chicken (3.3%) and cassava, mangoes and Cleome gynandra (each at 3%). Most foods were avoided for reasons associated with pregnancy and labour complications and undesirable effects on the baby. Most women learnt of the taboos and beliefs from the elders, their own mother, grandparents or mother-in-law, but there was also knowledge transmission in social groups within the community.

CONCLUSIONS

The taboos and cultural beliefs in the study area render pregnant and breast-feeding women prone to micronutrient deficiency since they are denied consumption of a diversity of nutritious foods. There is a need to educate such women about consumption of nutrient-rich foods like fish, eggs, fruits and vegetables in order to improve their health, that of the unborn and children being breast fed. Additionally, culturally appropriate nutrition education may be a good strategy to eliminate inappropriate food taboos and beliefs with negative impact on the health of pregnant and breast-feeding women.

Modulation of Immune Response and Cecal Microbiota by Dietary Fenugreek Seeds in Broilers

Fenugreek seeds (FSs) are a natural source of bioactive compounds that may modulate the immune system and gut microbiota in broilers. This study examined the effects of dietary fenugreek seed powder on immune-related gene expression and cecal microbiota composition in broilers. A total of 144 broiler chickens were randomly allocated to three dietary groups, CON (0 g/kg FS, FS5 (5 g/kg FS) and FS10 (10 g/kg FS), each with 6 replicates of 8 birds. Ileum tissues and cecal contents were collected on day 42 for the mRNA expression of inflammation and antimicrobial defense-related genes and cecal microbiome diversity, respectively. The results indicated that fenugreek seeds downregulated mRNA-level inflammation and antimicrobial defense-related genes: IL6, IL8L2, CASP6, PTGS2, IRF7, AvBD9, AvBD10, and AvBD11. Moreover, fenugreek seeds altered the cecal microbial community by increasing the population of Firmicutes and decreasing the population of Actinobacteriota, Gemmatimonadota and Verrucomicrobiota at the phylum level and increasing Alistipes, Bacteriodes and Prevotellaceae at the genera level. These findings suggest that fenugreek seeds have a positive impact on the immunological profile and microbiome of broiler chickens, possibly through the interplay of the immune system and the gut microbiome.

Oral bioavailability and egg drug residue of lincomycin in laying hens after different treatment

Lincomycin (LCM) is an antibiotic used to treat severe bacterial infections in livestock and companion animals. In this study, we aimed to investigate the oral bioavailability of LCM with PK data after IV and PO administration and to compare differences in drug residue patterns in eggs. To ensure food safety, an additional study on egg residue was conducted using 3 different commercial LCM drugs. For bioavailability study, laying hens were divided into oral and intravenous (n = 8/group) groups and received single dose (10 mg/kg) of LCM. The limits of quantification for LCM were 0.729 μg/mL and 0.009 mg/kg in plasma and eggs, respectively. The oral group exhibited a significantly lower average serum drug concentration than the IV group, with a bioavailability of 2.6%. Furthermore, the egg residue profiles confirmed reduced systemic drug exposure after oral administration. For the commercial LCM drug egg residue experiment, laying hens were divided into low- and high-dose groups (n = 12/group) for each drug and treated with the recommended dosage and administration method for each respective drug. The eggs were collected and analyzed until 14 d after the last drug treatment. Despite differences in the LCM content and formulation among commercial drugs, all the tested commercial drugs showed average concentrations below the MRL in eggs within approximately 3 d after the last drug treatment. In this study, we have confirmed that LCM has a low oral absorption rate in laying hens, and this was consistent with the findings from the egg residue profiles. Further studies are requested to elucidate the exact reasons for evidently low oral drug absorption in laying hens.

Dosage Optimisation of Trimethoprim and Sulfamethoxazole for the Treatment of an Avian Pathogenic Strain of Escherichia coli in Broiler Chickens

Based on pharmacokinetic studies carried out according to the methodologies defined by the European Medicines Agency (EMA) using mass spectrometry analysis, a new formulation of a veterinary drug for the treatment of broiler chickens is proposed. Currently, the traditional trimethoprim-sulfamethoxazole drug used for broilers is applied in a 1:5 ratio, and the recommended dose is 45 mg kg-1 of live weight administered at 24 h intervals for 3 to 5 days. In this study, we propose a novel combination containing similar active substances in a newly established ratio of 1:4, with a recommended dosage of 20 mg kg-1 of live weight administered at 24 h intervals for 3 to 5 days. With this method, the currently recommended dose of the traditional trimethoprim-sulfamethoxazole drug used for broilers can be reduced by more than half. The efficacy of the newly designed formulation and dosage of the drug was verified in a bioassay for the treatment of broilers experimentally infected with an avian pathogenic strain of Escherichia coli. In the experiment, we compared the newly designed dosage with the traditional dosage in terms of efficacy and dosage. There were no statistically significant differences between the two drugs in efficacy regarding the survival of chickens after experimental infection or changes in their health status. The experimental results suggest that a significant reduction in the recommended daily dose of drugs containing trimethoprim and sulfamethoxazole for the treatment of bacterial infections in broilers is possible and can support the prudent use of antimicrobials, including the limitation of their overuse.

Pharmacokinetic profiles and egg residue patterns of levamisole in laying hens at two dosing rates and two routes of administration

The levamisole maximum residue limit for edible fat, kidney, and muscle of chickens is 0.01 mg/kg. However, no maximum residue limit has been established for eggs. In the present study, the pharmacokinetic profile and levamisole residue in the eggs from laying hens were investigated using ultra-performance liquid chromatography-tandem mass spectrometry. A single dose of levamisole (30 mg/kg) was administered via the intramuscular or oral route, and an additional egg residue study was performed with 300 or 600 mg/kg commercial LEV drug (30 or 60 mg/kg as levamisole) orally. The limit of quantification was 0.0056 μg/mL and 0.0015 mg/kg for plasma and eggs, respectively. The plasma concentration was below the limit of quantification 10 and 12 h after intramuscular and oral administration, respectively. The half-life of the absorption phase was comparable between the intramuscular and oral routes, which was approximately 1 h, and the mean maximum concentration value was significantly higher in intramuscular (2.29 ± 0.30 μg/mL) than in oral (1.45 ± 0.38 μg/mL) route. The relative oral bioavailability after intramuscular administration was 92.3%. In the egg residue study, dose-dependent area under concentration and maximum concentration were observed after single oral administration of 30 and 60 mg/kg egg residue, and the calculated withdrawal period for both 30 and 60 mg/kg groups based on the positive list system standard (0.01 mg/kg) was 7 d after the treatment.

Vertical transmission of gut bacteria in commercial chickens is limited

The existence of vertical transmission in chickens under commercial settings, where chicks are raised separately from adults, is unclear. To answer this question, the fecal microbiota of chicks hatched and grown separately was compared with their mothers' microbiota. Most amplicon sequence variants (ASVs) identified in hens were not detected at all in chicks up to two weeks of age by 16S rDNA sequencing, and those that were detected had a low incidence among the chicks. Nevertheless, a few ASVs that were common with the hens were highly prevalent among the chicks, implying that they were efficiently transmitted to chicks. These ASVs were culturable from the reproductive tract of hens and eggshells. Furthermore, interventions attempting to disrupt transmission resulted in a reduction in the prevalence of specific phylogenetic groups in chicks. To conclude, vertical transmission in commercial poultry grown separately from adults likely exists but is not efficient, possibly resulting in impairment of microbiota function. This implies that artificial exposure to adult bacterial strains might improve microbiota functioning.

Screening and quantification of antibiotic residues in poultry products and feed in selected areas of Bangladesh

Background and Aim

Antibiotic residues in livestock farming have been identified as a potential cause of antimicrobial resistance in humans and animals. This study aimed to determine whether antibiotic residues were present in the chicken meat, eggs, feces, and feed collected from all four districts in the Mymensingh division of Bangladesh.

Materials and Methods

To detect antibiotic residues in the collected samples, qualitative thin-layer chromatography (TLC) and quantitative high-performance liquid chromatography (HPLC) were used. A total of 230 samples were analyzed for antibiotic residues of commonly used 11 antibiotics. Out of these, 40 meat and 40 feces samples were collected from broilers and layers, 30 egg samples from ducks and layers, and 120 feed samples from broilers and layers from the study area. Thin-layer chromatography was used to screen the presence of antibiotic residues; TLC-positive samples were then subjected to further HPLC analysis to determine the residue concentrations.

Results

Thin-layer chromatography analysis revealed that 23.5% of the tested samples contained residues from six different antibiotic classes (tetracyclines, quinolones, beta-lactams, sulfonamides, aminoglycosides, and macrolides). Thin-layer chromatography analysis showed that 35% and 25% of the meat samples were positive for residues from the broiler and layer, respectively. About 15% and 30% of layer and duck egg samples had positive residues, respectively. Out of 120 feed samples analyzed, about 15.8% had various antibiotic residues. In addition, feces samples from broilers and layers had 50% and 35% antibiotic residues, respectively. A total of 2.5% meat and 3.3% egg samples had antibiotic residues above the maximum residue limit (MRL). Based on the findings of this study, the highest percentage of oxytetracycline, followed by doxycycline and ciprofloxacin, were detected in feed samples, and oxytetracycline was detected in meat and egg samples.

Conclusion

This study clearly showed the misuse of antibiotics in the poultry sector in Bangladesh. Although antibiotic residues below the MRL level are suitable for human consumption, they may result in antimicrobial drug resistance to pathogens.

Egg residue and depletion of meloxicam in Jing Hong laying hens following multiple oral doses

Meloxicam is a nonsteroidal anti-inflammatory drug (NSAID) commonly used in an extra-label manner in commercial laying hens for the treatment of foot lesions, which are a common issue in this species. The present study aimed to determine the depletion profiles of meloxicam in eggs with multiple oral administration under 2 different dosing regimens and to further recommend reasonable withdrawal intervals (WDIs). Meloxicam (1 mg/kg) was administered orally to laying hens under 2 dosing schedules: 10 doses at 24-h intervals and 15 doses at 12-h intervals. Eggs were collected daily after the first dosing, and meloxicam concentrations in both yolk and white were determined by a high-performance liquid chromatography (HPLC) method. The weight ratio of white to yolk in the whole egg was 1.54 (the mean of 20 eggs with repeated tests), and this value combined with the meloxicam concentrations in white and yolk were used to calculate the drug concentrations in whole eggs. Meloxicam was quickly eliminated from egg white, and its concentrations could only be quantified at 2 time points during the elimination phase. The elimination half-lives in yolk and whole egg were 3.07 ± 1.00 and 2.98 ± 0.88 d, respectively, after 10 repeated doses. And the corresponding elimination half-lives were 2.30 ± 0.83 and 2.18 ± 0.67 d, respectively, after repeated 15 doses. Considering the time when meloxicam was not detectable in eggs with the time of ovum development and maturation, a withdrawal interval (WDI) was suggested as 17 d for both dosing schedules. The current results enriched the study on the residue of meloxicam in domestic Jing Hong laying hens and provided WDIs to help ensure animal-derived food safety.

Study on the Metabolic Transformation Rule of Enrofloxacin Combined with Tilmicosin in Laying Hens

There is often abuse of drugs in livestock and poultry production, and the improper use of drugs leads to the existence of a low level of residues in eggs, which is a potential threat to human safety. Enrofloxacin (EF) and tilmicosin (TIM) are regularly combined for the prevention and treatment of poultry diseases. The current studies on EF or TIM mainly focus on a single drug, and the effects of the combined application of these two antibiotics on EF metabolism in laying hens are rarely reported. In this study, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine the residual EF and TIM in laying hens and to investigate the effect of TIM on the EF metabolism in laying hens. In this paper, we first establish a method that can detect EF and TIM simultaneously. Secondly, the results showed that the highest concentration of EF in the egg samples was 974.92 ± 441.71 μg/kg on the 5th day of treatment. The highest concentration of EF in the egg samples of the combined administration group was 1256.41 ± 226.10 μg/kg on the 5th day of administration. The results showed that when EF and TIM were used in combination, the residue of EF in the eggs was increased, the elimination rate of EF was decreased, and the half-life of EF was increased. Therefore, the use of EF and TIM in combination should be treated with greater care and supervision should be strengthened to avoid risks to human health.

Ionophore coccidiostats - disposition kinetics in laying hens and residues transfer to eggs

Poultry production is linked with the use of veterinary medicinal products to manage diseases. Ionophore coccidiostats have been permitted for use as feed additives within the European Union (EU) for the prevention of coccidiosis in various species of poultry with except of laying hens. The presence of chemical residues in eggs is a matter of major concern for consumers' health. Despite such prohibition of use in laying hens, they were identified as the most common non-target poultry species being frequently exposed to these class of coccidiostats. Many factors can influence the presence of residues in eggs. Carryover of these class of coccidiostat feed additives in the feed of laying hens has been identified as the main reason of their occurrence in commercial poultry eggs. The physicochemical properties of individual compounds, the physiology of the laying hen, and the biology of egg formation are believed to govern the residue transfer rate and its distribution between the egg white and yolk compartments. This paper reviews the causes of occurrence of residues of ionophore coccidiostats in eggs within the EU with special emphasis on their disposition kinetics in laying hens, and residue transfer into eggs. Additional effort was made to highlight future modeling perspectives on the potential application of pharmacokinetic modeling in predicting drug residue transfer and its concentration in eggs.

Determination of extractable and non-extractable florfenicol residues as florfenicol amine in eggs by UPLC-MS/MS

Some florfenicol (FF) metabolites have a strong binding affinity towards biomolecules in the edible tissues of some food animals. These bound FF residues cannot be extracted directly from edible tissues with organic solvents and are present in higher concentrations even than solvent extractable residues. In this study, an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established to detect the total residues of FF in eggs, by quantifying the metabolite florfenicol amine (FFA). The sample was hydrolyzed at 95-100 °C for 4 hours to release sample-matrix bound residues and convert them all into FFA. The hydrolyzed sample was washed with ethyl acetate to remove interfering substances, extracted with ethyl acetate under alkaline conditions, purified by solid phase extraction and quantified by UPLC-MS/MS. The recoveries of FFA in eggs ranged from 91.2 to 102.4%, with an RSD ≤ 10.9%. The LOD and LOQ were 0.5 and 1.0 μg/kg, respectively. This method can be applied to the quantification of total FF residues in eggs.

Effect of Graded Levels of Fenugreek (Trigonella foenum-graecum L.) Seeds on the Growth Performance, Hematological Parameters, and Intestinal Histomorphology of Broiler Chickens

Two experiments were conducted to evaluate the effects of fenugreek seeds (FS) as a potential alternative to antibiotic growth promoters in broiler chickens. In the first experiment, one-day-old Ross (n = 160) straight-run broilers were fed FS at 0 g, 2.5 g, 5 g, and 10 g/kg of diet during the starter (from 1 to 21 days) and finisher phase (from 22 to 35 days) with four replicates of ten birds each. In the second experiment, one-day-old Ross (n = 144) male broilers were fed 0 g, 5 g, and 10 g FS per kilogram of diet during the starter (from 1 to 21 days) and finisher phase (from 22 to 42 days) with six replicates of eight birds each. In addition to growth performance, hematological parameters and intestinal histomorphology were measured in the second experiment. FS linearly reduced the body weight gain (BWG) (p < 0.001), feed intake (FI) (p < 0.05), and increased feed conversion ratio (FCR) (p < 0.05) during the starter phase in both experiments. However, no significant effects on BWG, FI, and FCR were observed during the finisher phase. Moreover, the overall BWG and FI were linearly reduced (p < 0.05) with the increasing levels of FS, but BWG and FI were similar in the 5 g/kg FS group and control group. The inclusion of FS had a linear increase in white blood cell (WBC), heterophil, and lymphocyte count (p < 0.005) and the decrease in hematocrit % (p = 0.004) and total bilirubin (p = 0.001). The villus height and villus height: crypt depth ratio of jejunum and ileum were significantly lower in 5 g FS and 10 g FS treatments (p < 0.001) compared to the control. The result indicates that the dietary inclusion of FS reduces the early growth performance, increases the WBC counts, and negatively affects the intestinal morphology of broiler chickens.

Quantitative Morphometric, Physiological, and Metabolic Characteristics of Chickens and Mallards for Physiologically Based Kinetic Model Development

Physiologically based kinetic (PBK) models are a promising tool for xenobiotic environmental risk assessment that could reduce animal testing by predicting in vivo exposure. PBK models for birds could further our understanding of species-specific sensitivities to xenobiotics, but would require species-specific parameterization. To this end, we summarize multiple major morphometric and physiological characteristics in chickens, particularly laying hens (Gallus gallus) and mallards (Anas platyrhynchos) in a meta-analysis of published data. Where such data did not exist, data are substituted from domesticated ducks (Anas platyrhynchos) and, in their absence, from chickens. The distribution of water between intracellular, extracellular, and plasma is similar in laying hens and mallards. Similarly, the lengths of the components of the small intestine (duodenum, jejunum, and ileum) are similar in chickens and mallards. Moreover, not only are the gastrointestinal absorptive areas similar in mallard and chickens but also they are similar to those in mammals when expressed on a log basis and compared to log body weight. In contrast, the following are much lower in laying hens than mallards: cardiac output (CO), hematocrit (Hct), and blood hemoglobin. There are shifts in ovary weight (increased), oviduct weight (increased), and plasma/serum concentrations of vitellogenin and triglyceride between laying hens and sexually immature females. In contrast, reproductive state does not affect the relative weights of the liver, kidneys, spleen, and gizzard.

Focused review: The role of drug combinations for the control of coccidiosis in commercially reared chickens

A survey of drug combinations employed by the poultry industry indicates that they have played an important role in the control of coccidiosis in chickens. The mode of action of their component drugs is described. Advantages that accrue from their use may include a reduction in potential toxicity, a broadening of their spectrum of activity against different species of Eimeria, activity against different stages of the life cycle, and improved efficacy due to synergism between component drugs. Integration of management procedures involving rotation of drug combinations with vaccination is desirable because this has been shown to result in a restoration of drug sensitivity where drug resistance is present and could contribute to the sustainable control of coccidiosis. Threats to the future use of the most widely used combinations, those that include ionophores, stem from the recent desire to eliminate antibiotics from poultry feeds.

Toxicity induced by ciprofloxacin and enrofloxacin: oxidative stress and metabolism

Ciprofloxacin (CIP) (human use) and enrofloxacin (ENR) (veterinary use) are synthetic anti-infectious medications that belong to the second generation of fluoroquinolones. They have a wide antimicrobial spectrum and strong bactericidal effects at very low concentrations via enzymatic inhibition of DNA gyrase and topoisomerase IV, which are required for DNA replication. They also have high bioavailability, rapid absorption with favorable pharmacokinetics and excellent tissue penetration, including cerebral spinal fluid. These features have made them the most applied antibiotics in both human and veterinary medicine. ENR is marketed exclusively for animal medicine and has been widely used as a therapeutic veterinary antibiotic, resulting in its residue in edible tissues and aquatic environments, as well as the development of resistance and toxicity. Estimation of the risks to humans due to antimicrobial resistance produced by CIP and ENR is important and of great interest. Moreover, in rare cases due to their overdose and/or prolonged administration, the development of CIP and ENR toxicity may occur. The toxicity of these fluoroquinolones antimicrobials is mainly related to reactive oxygen species (ROS) and oxidative stress (OS) generation, besides metabolism-related toxicity. Therefore, CIP is restricted in pregnant and lactating women, pediatrics and elderly similarly ENR do in the veterinary field. This review manuscript aims to identify the toxicity induced by ROS and OS as a common sequel of CIP and ENR. Furthermore, their metabolism and the role of metabolizing enzymes were reported.

Application of silanized melamine sponges in matrix purification for rapid multi-residue analysis of veterinary drugs in eggs by UPLC-MS/MS

Fast and convenient matrix purification is an important prerequisite for high-throughput analysis of drug multiresidues in food. In this study, a silanized melamine sponge was prepared and first applied in the rapid determination of multiclass veterinary drugs in eggs by ultrahigh-performance liquid chromatography-tandem mass spectrometry. Within five seconds, fast, convenient and efficient matrix separation could be achieved through simple soaking and squeezing. Compared to other matrix adsorbents, the developed material demonstrated equivalent or better purification performance. Good validation results were obtained in terms of drug recoveries (61.5%~97.0%, relative standard deviation (RSD) ≤ 10.8%), and linearities (R² ≥ 0.999), as well as low limits of quantitation (0.3 ~ 10.9 μg·kg^-1) and detection (0.1 ~ 3.8 μg·kg^-1). By analyzing 52 egg samples, high concentrations of ofloxacin, trimethoprim, metronidazole, and dimetridazole were found at 542.9, 121.2, 66.1 and 58.0 μg·kg^-1, respectively. The silanized melamine sponge has shown its great potential for rapid analysis of multiclass residues in food safety.

Antimicrobial agents in laying hens

The European Union permitted 6 antimicrobial agents that can be used in laying hens. These are colistin, tyrosine, neomycin, oxytetracycline, chlortetracycline, and erythromycin. Antimicrobial drugs are used today primarily for the prevention and treatment of diseases in poultry and often (not in the EU) to stimulate growth. Because these drugs are often used irrationally, there are good chances that their residues will be found not only in poultry meat but also in the eggs within a certain period after the termination of treatment. In addition to the administration of authorised VMPs, the residues in eggs can be the result of erroneously applied medicated food, the contamination of the food with some antimicrobial drug in the mixing unit, as well as ?extra-label? use of drugs in poultry. The antimicrobial agents are distributed in the body and deposited in the eggs, mainly in the yolk where they persist longer than in the albumen. Drugs that are poorly absorbed from the gastrointestinal tract (aminoglycosides, aminocyclitols, polymyxins) cannot be detected in the eggs, while the residues of some antimicrobial drugs can be detected for up to two months (chloramphenicol) after the last treatment. The rational use of drugs in veterinary medicine has manifold significance. When using drugs only when they are really necessary (indicated), in the right dose and route of administration, the potential damage can be reduced and efficiency increased, while the risk of microorganism resistance development would be significantly decreased. All of this becomes more important when these drugs are used in food animals.

Effects of Selenium Conjugated to Insect Protein on Pharmacokinetics of Florfenicol and Enrofloxacin in Laying Hens

In the context of increasing awareness on the dietary supplementation of organic selenium in commercial poultry production and ensuring safe egg production, the present study investigated the effects of selenium on the pharmacokinetics of the therapeutic use of florfenicol and enrofloxacin from perspectives of laying performance, selenium deposition in eggs, and drug residue in plasma, organs, and eggs. A 2 × 3 factorial arrangement with two kinds of drugs (florfenicol vs. enrofloxacin, 200 mg/kg) and three levels of dietary organic selenium SCIP (selenium conjugated to insect protein) (0, 2, and 5 mg/kg) was designed together with a blank control group. Healthy Hy-Line Brown laying hens (n = 252, 40-week-old and 90.0 ± 1.7% of egg production rate) were randomly allocated into one of seven treatments with six replicates and six hens per replicate. The experiment lasted for 42 days and consisted of three periods (adjusted stage, depositional stage, and eliminating stage) of 14 days each. These stages entail feeding of the laying hens with basal diets, addition of drugs and selenium synchronously into the diets, drug withdrawal from diet, and supply of selenium uninterruptedly in the diet. Egg production and feed intake were recorded on daily and weekly bases, respectively. The selenium content in egg yolk, egg white, and whole eggs and the drug residues in eggs, plasma, liver, kidney, and breast muscle were determined on days 2, 3, 5, 6, 7, 9, 11, and 14 of the depositional and eliminating stages. There was no significant difference (p > 0.05) in egg production among the dietary treatments, but feed intake decreased significantly (p < 0.05) in the drug treatment group compared to other groups. Dietary organic selenium decreased the residue of drugs in tissues and eggs, while the metabolism and deposition of selenium in laying hens were suppressed due to drug effects. The results of the present study are of significance to enrich the knowledge of the pharmacokinetics of florfenicol and enrofloxacin in laying hens and ensure the quality of poultry products.

Susceptibility of Commensal E. coli Isolated from Conventional, Antibiotic-Free, and Organic Meat Chickens on Farms and at Slaughter toward Antimicrobials with Public Health Relevance

The spread of resistant bacteria from livestock to the food industry promoted an increase of alternative poultry production systems, such as organic and antibiotic-free ones, based on the lack of antimicrobial use, except in cases in which welfare is compromised. We aimed to investigate the antibiotic susceptibility of commensal Escherichia coli isolated from organic, antibiotic-free, and conventional broiler farms and slaughterhouses toward several antimicrobials critically important for human health. To assess antimicrobial susceptibility, all E. coli isolates and extended spectrum beta-lactamase (ESBL) E. coli were analysed by the microdilution method. The prevalence of tigecycline, azithromycin and gentamicin E. coli-resistant strains was highest in organic samplings. Conversely, the lowest prevalence of resistant E. coli strains was observed for cefotaxime, ceftazidime and ciprofloxacin in organic systems, representing a significant protective factor compared to conventional systems. All E. coli strains were colistin-susceptible. Contamination of the external environment by drug-resistant bacteria could play a role in the presence of resistant strains detected in organic systems. Of interest is the highest prevalence of cephalosporin resistance of E. coli in conventional samplings, since they are not permitted in poultry. Our results suggest that monitoring of antibiotic resistance of the production chain may be helpful to detect "risks" inherent to different rearing systems.

Sports drug testing and the athletes' exposome

Similar to the general population, elite athletes are exposed to a complex set of environmental factors including chemicals and radiation and also biological and physical stressors, which constitute an exposome that is, unlike for the general population, subjected to specific scrutiny for athletes due to applicable antidoping regulations and associated (frequent) routine doping controls. Hence, investigations into the athlete's exposome and how to distinguish between deliberate drug use and different contamination scenarios has become a central topic of antidoping research, as a delicate balance is to be managed between the vital and continually evolving developments of sensitive analytical techniques on the one hand, and the risk of the athletes' exposome potentially causing adverse analytical findings on the other.

Controlling the causative agents of coccidiosis in domestic chickens; an eye on the past and considerations for the future

Coccidiosis is a potentially severe enteritis caused by species of obligate intracellular parasites of the genus Eimeria. These parasites cause significant economic losses to the poultry industry, predominantly due to compromised efficiency of production as well as the cost of control. These losses were recently estimated to cost chicken producers approximately £10.4 billion worldwide annually. High levels of Eimeria infection cause clinical coccidiosis which is a significant threat to poultry welfare, and a pre-disposing contributory factor for necrotic enteritis. Control of Eimeria parasites and coccidiosis is therefore an important endeavour; multiple approaches have been developed and these are often deployed together. This review summarises current trends in strategies for control of Eimeria, focusing on three main areas: good husbandry, chemoprophylaxis and vaccination. There is currently no "perfect solution" and there are advantages and limitations to all existing methods. Therefore, the aim of this review is to present current control strategies and suggest how these may develop in the future.

Depletion of clomiphene residues in eggs and muscle after oral administration to laying hens

The selective oestrogen receptor modulator (SERM) clomiphene is therapeutically used to induce ovulation. While prohibited as a doping agent in sports, it is frequently detected in sports drug testing urine samples. Few reports exist on clomiphene's (illicit) use in the farming industry to increase the egg production rate of laying hens, which creates a risk that eggs as well as edible tissue of these hens contain residues of clomiphene. To investigate the potential transfer of clomiphene into eggs and muscle tissue, laying hens were orally administered with clomiphene citrate at 10 mg/day for 28 days. To determine clomiphene residues in eggs, chicken breast and chicken thigh, the target analyte was extracted from homogenised material with acetonitrile and subjected to ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis. The test method reached a limit of quantification (LOQ) of 1 µg/kg and was characterised concerning specificity, precision, trueness and linearity. Analyses were performed on whole egg, egg white and yolk separately, and chicken muscle from breast and thigh. Clomiphene was detectable in eggs two days after the beginning of the drug administration period. The drug concentrations increased to 10-20 µg per egg within one week, and after withdrawal of clomiphene, residues decreased after 4 days, but traces of clomiphene were still detectable until the end of the study (14 days after the last administration). In the chicken's muscle tissue, clomiphene levels up to 150 µg/kg (thigh) and 36 µg/kg (breast) were found. Six days after the last dose, tissue clomiphene concentrations fell below the LOQ. Overall, these results underline the concerns that clomiphene may be transferred into animal-derived food and future research will therefore need to focus on assessing and minimising the risk of unintentional adverse analytical findings in doping controls.

Pharmacokinetics of Colistin in the Gastrointestinal Tract of Poultry Following Dosing via Drinking Water and Its Bactericidal Impact on Enteric Escherichia coli

Colistin, a last-line antibiotic of major importance in veterinary medicine and of critical importance in human medicine, is authorized to treat gastrointestinal (enteric) infections caused by non-invasive Escherichia coli in multiple veterinary species including poultry. Its use in veterinary medicine has been implicated in the widespread prevalence of mobilized colistin resistance. The objectives of this study were to determine the intestinal content reached in broiler chickens during 72-h treatment with colistin, to evaluate the associated impact on intestinal E. coli density, and to select less susceptible E. coli populations. In this study, 94 broiler chickens were administered a dose of 75,000 IU/kg/day via drinking water. Intestinal samples were collected pre-, during-, and post-dosing. Luminal intestinal content was assessed for colistin content by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), and E. coli were isolated and enumerated on UriSelect agar™. Minimum inhibitory concentration (MIC, for eight isolates per intestine per animal) was determined, and when higher than the epidemiological cutoff (ECOFF 2 mg/l), isolates were screened for mobilized colistin resistance (mcr)-1 to 5. Colistin content increased during treatment to a maximum of 5.09 mg/kg. During this time, the total population of E. coli showed an almost 1,000-fold reduction. An apparent increase in the relative abundance of E. coli with an MIC ≥ ECOFF, either mcr-negative (6.25–10.94%) or mcr-1-positive (4.16–31.25%) was observed, although this susceptibility shift was not maintained post-treatment. Indeed, following cessation of dosing, colistin was eliminated from the intestine, and content was below the limit of quantification (LOQ, 1.1 mg/kg) within 4 h, and the median MIC of E. coli isolates returned below baseline thereafter. Few isolates with a lower susceptibility (mcr-1-positive or negative) were however observed at the end of the study period, indicating maintained sub-populations in the chicken gut. The results of this study show a limited impact on long-term maintenance of less susceptible E. coli populations as a direct result of colistin treatment in individual birds.

Ameliorative role of trans-ferulic acid on induced oxidative toxicity of rooster semen by β-cyfluthrin during low temperature liquid storage

Current study was designed to evaluate the effects of β-cyfluthrin, as a toxicant substance, and trans-ferulic acid (trans-FA), as a protective agent, on different parameters of rooster semen upon liquid storage. For this purpose, semen samples of roosters (Ross 308, n = 10, 32-wk-old) were collected twice a week. Good quality samples (≥70% progressive motion) were diluted, pooled and then divided for the purposes of the study. In the first experiment, motility of spermatozoa was evaluated following exposure to different concentrations of β-cyfluthrin (1, 2.5, 5, 10, 20, 40, and 80 µM) at 0, 24, and 48 h of storage. In the second experiment, constant doses of β-cyfluthrin (10 µM) alone or in combination with trans-FA (10, 25 mM) were assessed on motility and viability of spermatozoa at 0, 24, and 48 h time points. Moreover, amounts of malondialdehyde (MDA), total antioxidant capacity (TAC), total nitrate-nitrite, total hydroperoxide (HPO), and activity of superoxide dismutase (SOD) were evaluated in the homogenate of spermatozoa-diluent at studied time points. Results of the first experiment showed that amounts of β-cyfluthrin greater than 5 µM, significantly reduced the motility of spermatozoa at 24 and 48 h of storage (P < 0.05). The second experiment demonstrated that, trans-FA especially at 10, 25 mM doses restored the motility and viability of spermatozoa compared to β-cyfluthrin treated group (P < 0.05). Amounts of MDA (10, 25 mM), hydroperoxide (10, 25, and 50 mM), and nitrate-nitrite (10, 25, and 50 mM) were lower and TAC (10 and 25 mM) were greater in trans-FA + β-cyfluthrin treated groups compared to β-cyfluthrin alone treated samples (P < 0.05). However, activity of SOD did not show significant changes by the treatment (P > 0.05). It seems that trans-FA could ameliorate toxic effect of β-cyfluthrin via reduction of peroxidative (as evident by measurement of MDA) and nitrosative (as evident by measurement of nitrate-nitrite) reactions over cold preservation of rooster semen.

Antibiotic Prescription in Veterinary Consultations in Bhutan: A Retrospective Cross-Sectional Study

The veterinary prescription of antibiotics in low- and middle-income countries (LMIC) remains largely undocumented. In Bhutan, however, the national veterinary service keeps records of their activities and prescriptions, which offer an opportunity to establish a benchmark to assess the use of these agents in this and other LMIC. A cross-sectional retrospective study was designed and 2,266 handwritten veterinary records from 2017 were sampled from 23 animal health premises (AHPs) to estimate individual and an overall proportion of consultations that resulted in an antibiotic prescription. The frequency of antibiotic prescription per species, type of AHP, and according to WHO's AWaRe index and OIE list of priority antimicrobials were also explored. It was estimated that 31% (95% confidence interval: 29–33%; intracluster correlation: 0.03) of the veterinary consultations resulted in an antibiotic prescription. The incidence of antibiotic prescription was highest in consultations of poultry across AHP. Across species, diarrhea and wounds were frequently treated with broad-spectrum antibiotics including sulfonamides, tetracyclines, trimethoprim + sulfa, and penicillin. Between 45% and 70% antibiotics prescribed correspond to AWaRe's access group and up to 25% to AWaRe's watch group. Over 70% of antibiotics dispensed in veterinary consultations for any species correspond to the OIE's veterinary critically important antimicrobial agents. Overall, the study demonstrated positive features of veterinary antimicrobial stewardship in Bhutan, given the conservative proportion of consultation that results in this type of prescription and the type of antibiotic prescribed. Although the veterinary service closely follows the Bhutanese Standard Treatment Guidelines, the prescription of antibiotics to key species should be closely monitored. Our study suggests that further improvements of antibiotic stewardship can be achieved through standardisation of antibiotic prescription to some species, a revision of the guidelines toward reducing the prescription of antibiotics of high relevance for human medicine, and by including details of clinical investigation, use of tests, and treatment outcomes in veterinary consultation records.

Egg residue and depletion in Rhode Island Red hens (Gallus gallus domesticus) following multiple oral doses of trimethoprim-sulfamethoxazole

Sulfamethoxazole-Trimethoprim residues in eggs can cause risks to human health. The most common cause of residues in eggs results from failure to meet an appropriate withdrawal interval. The aim of this study was to determine the quantity and duration of sulfamethoxazole-trimethoprim residues in eggs and evaluate the drug elimination parameters in egg components and whole egg to better estimate the withdrawal interval of sulfamethoxazole and trimethoprim following oral administration for 7 days at a purposed dosage regimen (time average 46 mg kg^-1 day^-1 for sulfamethoxazole, time average 25 mg kg^-1 day^-1 for trimethoprim). Residues of sulfamethoxazole and trimethoprim in albumen and yolk were analyzed by ultra-performance liquid chromatography mass spectrometry. A greater percentage of sulfamethoxazole was distributed into the albumen (91.53-96.74%) and a greater percentage of trimethoprim was distributed into yolk (63.92-77.36%) during treatment. The residues levels in whole egg declined below or reached the limit of quantification until 13 days for SMZ and TMP respectively. The withdrawal interval for SMZ and TMP were 43 days and 17 days respectively using the FDA tolerance method.

Novel spectrofluorimetric technique for determination of amoxicillin and ethopabate in chicken tissues, liver, kidney, eggs, and feed premix

A new smart spectrofluorometric method was developed for the quantitation of amoxicillin and ethopabate simultaneously for the first time. The method is based on measuring their first derivative synchronous amplitudes in water at Δλ = 80 nm. The peak amplitudes were recorded at their crossing points; 240 nm for amoxicillin and 280 nm for ethopabate. The method is linear over the concentration ranges of 100.0-1,000.0 ng/ml for amoxicillin and 2.0-20.0 ng/ml for ethopabate. The limits of detection were 20.0 ng/ml and 0.58 ng/ml and limits of quantitation were 60.0 ng/ml and 1.92 ng/ml for amoxicillin and ethopabate, respectively. The method sensitivity permitted the determination of the two drugs below their maximum residue limit stated by the federal regulations. The developed method was applicable to the analysis of both drugs in the veterinary powders, feed premix, chicken tissues, liver, kidney, and eggs samples with percentage recoveries ranging 93.72-104.71%.

Veterinary Drug Residues in Animal-Derived Foods: Sample Preparation and Analytical Methods

Veterinary drugs are used to treat livestock and aquatic diseases and thus are introduced into animal-derived foods, endangering consumer health and safety. Antibiotic resistance is rapidly becoming a major worldwide problem, and there has been a steady increase in the number of pathogens that show multi-drug resistance. Illegal and excessive use of veterinary drugs in animals and aquaculture has serious adverse effects on humans and on all other environmental organisms. It is necessary to develop simple extraction methods and fast analytical methods to effectively detect veterinary drug residues in animal-derived foods. This review summarizes the application of various sample extraction techniques and detection and quantification methods for veterinary drug residues reported in the last decade (2010-2020). This review compares the advantages and disadvantages of various extraction techniques and detection methods and describes advanced methods, such as those that use electrochemical biosensors, piezoelectric biosensors, optical biosensors, and molecularly imprinted polymer biosensors. Finally, the future prospects and trends related to extraction methods, detection methods and advanced methods for the analysis of veterinary drug residues in animal-derived foods are summarized.

Multi-Class Procedure for Analysis of 50 Antibacterial Compounds in Eggshells Using Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

In this work, for the first time, Ultra-High-Performance Liquid Chromatography–Tandem Mass Spectrometry (UHPLC–MS/MS) method was developed for qualitative and quantitative analysis of veterinary antibiotics (cephalosporins, diaminopyrimidines, fluoro(quinolones), lincosamides, macrolides, penicillins, pleuromutilins, sulfonamides, tetracyclines, and sulfones) in hen eggshells. The sample preparation method is based on a liquid–liquid extraction with a mixture of metaphosphoric acid, ascorbic acid, EDTA disodium salt dihydrate, and acetonitrile. The chromatographic separation was performed on Luna^® Omega Polar C18 10 column in gradient elution mode and quantitated in an 8 min run. Validation such as linearity, selectivity, precision, recovery, matrix effect, limit of quantification (LOQ), and limit of detection (LOD) was found to be within the acceptance criteria of the validation guidelines of the Commission Decision 2002/657/EC and EUR 28099 EN. Average recoveries ranged from 81–120%. The calculated LOQ values ranged from 1 to 10 µg/kg, the LOD values ranged from 0.3 to 4.0 µg/kg, depending on analyte. The developed method has been successfully applied to the determination of antibacterial compounds in hen eggshell samples obtained from different sources. The results revealed that enrofloxacin, lincomycin, doxycycline, and oxytetracycline were detected in hen eggshell samples.

Determination of residual enrofloxacin in eggs due to long term administration to laying hens. Analysis of the consumer exposure assessment to egg derivatives

The use of the antibiotic enrofloxacin (ENR) in poultry is controversial. A high-performance liquid chromatography coupled to fast-scanning fluorescence detection (HPLC-FSFD) method for the determination of ENR in egg white, egg yolk, and lyophilized samples was developed. In a first analysis, the long-term administration of ENR (100 days) to laying hens was carried out to determine its presence in egg white, yolk, or both. The predominance of ENR was observed in egg white and variations in the weight of egg white and eggshell was evidenced, showing a potential problem in the industry. Eventually, the presence of ENR was confirmed in commercial lyophilized egg white samples in concentration values around 350 µg kg^-1. The consumer exposure assessment was estimated for children, adolescents, and adults. The result displayed that, in an intake of lyophilized egg white with food-producing animals, the %ADI exceeds 100%, showing toxicological levels.

A Cross-Sectional Study of Antimicrobial Usage on Commercial Broiler and Layer Chicken Farms in Bangladesh

Commercial poultry production is growing rapidly in Bangladesh to address the increasing demand for poultry meat and eggs. Challenges faced by producers include the occurrence of poultry diseases, which are usually treated or controlled by antimicrobials. A cross-sectional study was conducted on 57 commercial layer and 83 broiler farms in eight subdistricts of the Chattogram district, Bangladesh, to assess antimicrobial usage in relation to clinical signs observed in chicken flocks on these farms. Of the 140 commercial chicken farms, 137 (97.9%) used antimicrobials and 24 different antimicrobial agents were administered. On layer farms, the most commonly used antimicrobials were ciprofloxacin (37.0% of farms, 20/54), amoxicillin (33.3%, 18/54), and tiamulin (31.5%, 17/54), while on broiler farms, colistin (56.6%, 47/83), doxycycline (50.6%, 42/83), and neomycin (38.6%, 32/83) were most commonly administered. Only 15.3% (21/137) of farmers used antimicrobials exclusively for therapeutic purposes, while 84.7% (116/137) of farmers used them prophylactically, administering them either for prophylactic purposes only (22.6% of farmers, 31/137) or in combination with therapeutic purposes (62.1% of farmers, 85/137). About 83.3% (45/54) of layer farmers were selling eggs while antimicrobials were being administered compared to 36.1% (30/83) of the broiler farmers selling broiler chickens while administering antimicrobials. Overall, 75.2% (103/137) of farmers reported clinical signs for which they administered antimicrobials, while 24.8% (34/137) of farmers reported no clinical signs but still administered antimicrobials. Respiratory signs (71.8% of farms with clinical signs, 74/103) were most commonly reported, followed by enteric signs (32.0%, 33/103) and increased mortality (16.5%, 17/103). About 37.2% (51/137) of farmers bought antimicrobials exclusively from feed and chick traders, followed by veterinary medical stores (35.0%, 48/137). Purchasing antimicrobials from feed and chick traders was more common among broiler than layer farmers. It is recommended that commercial poultry farmers should keep records of antimicrobials used with dosage and duration of administration along with indication of use. This would allow farmers and veterinarians to review if antimicrobial usage had the desired effects and to evaluate the appropriate use of antimicrobial agents under an antimicrobial stewardship approach.

Physiological parameter values for physiologically based pharmacokinetic models in food-producing animals. Part II: Chicken and turkey

Physiologically based pharmacokinetic (PBPK) models are growing in popularity due to human food safety concerns and for estimating drug residue distribution and estimating withdrawal intervals for veterinary products originating from livestock species. This paper focuses on the physiological and anatomical data, including cardiac output, organ weight, and blood flow values, needed for PBPK modeling applications for avian species commonly consumed in the poultry market. Experimental and field studies from 1940 to 2019 for broiler chickens (1-70 days old, 40 g - 3.2 kg), laying hens (4-15 months old, 1.1-2.0 kg), and turkeys (1 day-14 months old, 60 g -12.7 kg) were searched systematically using PubMed, Google Scholar, ProQuest, and ScienceDirect for data collection in 2019 and 2020. Relevant data were extracted from the literature with mean and standard deviation (SD) being calculated and compiled in tables of relative organ weights (% of body weight) and relative blood flows (% of cardiac output). Trends of organ or tissue weight growth during different life stages were calculated when sufficient data were available. These compiled data sets facilitate future PBPK model development and applications, especially in estimating chemical residue concentrations in edible tissues to calculate food safety withdrawal intervals for poultry.

Understanding of Colistin Usage in Food Animals and Available Detection Techniques: A Review

Progress in the medical profession is determined by the achievements and effectiveness of new antibiotics in the treatment of microbial infections. However, the development of multiple-drug resistance in numerous bacteria, especially Gram-negative bacteria, has limited the treatment options. Due to this resistance, the resurgence of cyclic polypeptide drugs like colistin remains the only option. The drug, colistin, is a well-known growth inhibitor of Gram-negative bacteria like Acinetobacter baumanni, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Technological advancements have uncovered the role of the mcr-1(mobilized colistin resistance) gene, which is responsible for the development of resistance in Gram-negative bacteria, which make them distinct from other bacteria without this gene. Additionally, food animals have been determined to be the reservoir for colistin resistance microbes, from which they spread to other hosts. Due to the adverse effects of colistin, many developed countries have prohibited its usage in animal foods, but developing countries are still using colistin in animal food production, thereby imposing a major risk to the public health. Therefore, there is a need for implementation of sustainable measures in livestock farms to prevent microbial infection. This review highlights the negative effects (increased resistance) of colistin consumption and emphasizes the different approaches used for detecting colistin in animal-based foods as well as the challenges associated with its detection.

Pharmacokinetics, bioavailability and tissue residues of doxycycline in Japanese quails (Coturnix coturnix japonica) after oral administration

This study aimed to determine the bioavailability, tissue residue and withdrawal time of doxycycline after oral administration in Japanese quails (Coturnix coturnix japonica). Japanese quails received doxycycline at 20 mg/kg dose following either single intravenous or oral administration, or 5-day oral administration. Doxycycline concentrations in plasma, liver, kidney, muscle, and skin + fat were determined using high-performance liquid chromatography-ultraviolet. The Withdrawal Time v1.4 software was used to calculate withdrawal times. Following single oral administration, terminal elimination half-life, area under the concentration-time curve from 0 to infinitive time, peak plasma concentration (C_max) and time to reach C_max were 10.98 h, 215.84 (h*µg)/mL, 15.33 μg/mL, and 2 h, respectively. The oral bioavailability was 25.84% in quails. In this study, the mean doxycycline concentration was below the maximum residue limit (MRL) at day 4 in skin + fat (0.120 µg/g), and at day 5 in kidney (0.41 µg/g), liver (0.26 µg/g), and muscle (<0.05 µg/g lowest limit of quantification). The highest concentrations of doxycycline after 5-day oral administration were found in kidney compared with other tissues and plasma. These results indicate that the withdrawal times required for doxycycline to reach concentrations <MRLs after 5-day oral administration at 20 mg/kg dose in Japanese quail are 6 days in Europe and China and 9 days in Japan.

High abundance of the colistin resistance gene mcr-1 in chicken gut-bacteria in Bangladesh

Colistin is considered a last-resort reserved drug for the treatment of critical human infections by Gram-negative bacteria. Phenotypic colistin-resistance is strongly associated with plasmid-mediated mobile colistin resistance (mcr) genes. The mcr-bearing Enterobacteriaceae have been detected in many countries from environments, animals, and humans. This study investigated phenotypic colistin-resistance and the distribution of mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5 genes in chicken-gut bacteria in Bangladesh. Bacteria were isolated from poultry- and native-chicken droppings, and their susceptibilities to colistin were determined by agar dilution and E-test minimal inhibitory concentration (MIC) measurements. Multiplex polymerase chain reactions detected mcr-1 to mcr-5 genes. Overall, 61.7% (92/149) of the isolates showed colistin resistance by agar dilution assessment (MIC > 2.0 μg/mL). The phenotypic resistance was observed considerably higher in poultry-chicken isolates (64.6%, 64/99) than in native-chicken isolates (56%, 28/50; p = 0.373). All the resistant isolates showed MIC levels between > 2 and > 128 μg/mL. The mcr-genes (mcr-1and mcr-2 combined) were detected more in poultry gut bacteria (36.4%) than native-chicken isolates (20%, p = 0.06). Despite bacteria sources, mcr-genes appeared to be significantly associated with phenotypic colistin-resistance phenomena (p < 0.001). Prior colistin usage led to a substantial increase in the proportion of bacteria with mcr-genes and phenotypic resistance (p < 0.001).

Fluoroquinolones and trace elements in poultry litter: estimation of environmental load based on nitrogen requirement for crops

Poultry litter soil application contributes to sustainability of agricultural systems and is in accordance with the United Nations Sustainable Development Goals (UN-SDG). Poultry litter recommended rates are based on crop nitrogen (N) needs, however, their application can be a potential source of antibiotics and trace elements overload. The aim of the study was to estimate the role of poultry litter application on soil contamination by fluoroquinolones [enrofloxacin (ENR) and ciprofloxacin (CIP)] and trace elements, based on N requirements for crops. Analytical and sampling techniques were used to estimate the loads from poultry litter application. Only CIP was found in poultry litter samples (283 ± 124 µg kg^-1) and its load was estimated to be of 9.89 ± 4.33 g ha^-1, for the poultry litter application (35 t ha^-1). The estimated loads (g ha^-1) of trace elements were: Cr 9.19 ± 3.26, Ni 12.3 ± 4.93, Pb 22.0 ± 8.26, Cu 229 ± 85.6, Mn 691 ± 259 and Zn 1,011 ± 378. These estimates were 900% higher than those recommended by the technical guidance, while N exceeded 600% the recommended application. In order to achieve UN-SDGs, local policies to disseminate knowledge and technologies are required for consolidating sustainable agricultural practices.

Characterization of Sunflower Oil Extracts from the Lichen Usnea barbata

The increasing global emergence of multidrug resistant (MDR) pathogens is categorized as one of the most important health problems. Therefore, the discovery of novel antimicrobials is of the utmost importance. Lichens provide a rich source of natural products including unique polyketides and polyphenols. Many of them display pharmaceutical benefits. The aim of this study was directed towards the characterization of sunflower oil extracts from the fruticose lichen, Usnea barbata. The concentration of the major polyketide, usnic acid, was 1.6 mg/mL extract as determined by NMR analysis of the crude mixture corresponding to 80 mg per g of the dried lichen. The total phenolics and flavonoids were determined by photometric assays as 4.4 mg/mL (gallic acid equivalent) and 0.27 mg/mL (rutin equivalent) corresponding to 220 mg/g and 13.7 mg/g lichen, respectively. Gram-positive (e.g., Enterococcus faecalis) and Gram-negative bacteria, as well as clinical isolates of infected chickens were sensitive against these extracts as determined by agar diffusion tests. Most of these activities increased in the presence of zinc salts. The data suggest the potential usage of U. barbata extracts as natural additives and mild antibiotics in animal husbandry, especially against enterococcosis in poultry.

Phenomenal Bombardment of Antibiotic in Poultry: Contemplating the Environmental Repercussions

Antibiotics have constantly been added at an unprecedented rate in order to enhance poultry meat production. Such antibiotics impose a negative impact on human health directly through meat and egg consumption. On the other hand, they also affect humans indirectly by affecting the normal key microbial processes in the agricultural environments, when used as poultry compost. For many years, farmers have been turning poultry litter into compost for agricultural use. Very few studies have addressed the fate of the unmetabolized antibiotic residues in poultry litter that could potentially affect microbial communities when used as poultry compost. We have also questioned the fate of residual antibiotic in poultry waste which may create possible negative environmental pressure on microbial communities that are involved in microbial mediated poultry litter composting processes. The incorporation of antibiotic degrading environmental isolates in poultry litter at the initial stage of composting in order to accelerate the process is addressed in this review as a future perspective.

Depletion of florfenicol and florfenicol amine in eggs of laying hens and growing pullets after oral administration

In this study, we carried out two experiments to evaluate depletion of florfenicol (FF) and its metabolite florfenicol amine (FFA) in eggs from growing pullets and laying hens. Eggs were collected, and the egg white and yolk were separated. FF and FFA were analysed by liquid chromatography-tandem mass spectrometry. In the first experiment, 30 laying hens were given FF capsules at 50 mg/kg·bw^-1 daily for 5 d. FF + FFA was detectable in egg white (1,190 µg/kg) on day 1 of treatment and increased slowly thereafter. After treatment, the residues decreased rapidly and were not detected by day 11. In yolk, residues were detected at a lower concentration on day 1 and increased dramatically to 3308 µg/kg at the end of treatment. The residues remained steady over the next 4 days post-treatment, followed by a rapid drop. Residues were not detectable on day 15 post-treatment. In the second experiment, four groups (B1 through B4) of growing pullets were treated in the same manner for 25, 20, 15, and 10 days before egg primiparity. FF and FFA were not detectable in the eggs of group B1; however, they were detectable in egg whites and yolks of groups B2, B3, and B4. The highest total concentrations of FF and FFA detected in egg white and yolk of group B4 were 3,190 µg/kg and 3,214 µg/kg, respectively. Thereafter, concentrations decreased until no more residues were detected in egg whites or yolks on days 17 and 21 post-treatment, respectively. Therefore, drug treatment should be stopped at least 21 d before primiparity of growing pullets to guarantee food safety.

Biomagnification and body distribution of ivermectin in dung beetles

A terrestrial test system to investigate the biomagnification potential and tissue-specific distribution of ivermectin, a widely used parasiticide, in the non-target dung beetle Thorectes lusitanicus (Jekel) was developed and validated. Biomagnification kinetics of ivermectin in T. lusitanicus was investigated by following uptake, elimination, and distribution of the compound in dung beetles feeding on contaminated faeces. Results showed that ivermectin was biomagnified in adults of T. lusitanicus when exposed to non-lethal doses via food uptake. Ivermectin was quickly transferred from the gut to the haemolymph, generating a biomagnification factor (BMF_k) three times higher in the haemolymph than in the gut after an uptake period of 12 days. The fat body appeared to exert a major role on the biomagnification of ivermectin in the insect body, showing a BMF_k 1.6 times higher than in the haemolymph. The results of this study highlight that the biomagnification of ivermectin should be investigated from a global dung-based food web perspective and that the use of these antiparasitic substances should be monitored and controlled on a precautionary basis. Thus, we suggest that an additional effort be made in the development of standardised regulatory recommendations to guide biomagnification studies in terrestrial organisms, but also that it is necessary to adapt existing methods to assess the effects of such veterinary medical products.

An open source physiologically based kinetic model for the chicken (Gallus gallus domesticus): Calibration and validation for the prediction residues in tissues and eggs

Xenobiotics from anthropogenic and natural origin enter animal feed and human food as regulated compounds, environmental contaminants or as part of components of the diet. After dietary exposure, a chemical is absorbed and distributed systematically to a range of organs and tissues, metabolised, and excreted. Physiologically based kinetic (PBK) models have been developed to estimate internal concentrations from external doses. In this study, a generic multi-compartment PBK model was developed for chicken. The PBK model was implemented for seven compounds (with log K_ow range -1.37-6.2) to quantitatively link external dose and internal dose for risk assessment of chemicals. Global sensitivity analysis was performed for a hydrophilic and a lipophilic compound to identify the most sensitive parameters in the PBK model. Model predictions were compared to measured data according to dataset-specific exposure scenarios. Globally, 71% of the model predictions were within a 3-fold change of the measured data for chicken and only 7% of the PBK predictions were outside a 10-fold change. While most model input parameters still rely on in vivo experiments, in vitro data were also used as model input to predict internal concentration of the coccidiostat monensin. Future developments of generic PBK models in chicken and other species of relevance to animal health risk assessment are discussed.

Procedure for the Screening of Eggs and Egg Products to Detect Oxolonic Acid, Ciprofloxacin, Enrofloxacin, and Sarafloxacin Using Micellar Liquid Chromatography

A method based on micellar liquid chromatography was developed to determine oxolinic acid, ciprofloxacin, enrofloxacin, and sarafloxacin in eggs and egg products. The antimicrobial drugs were obtained in a micellar solution which was directly injected. The analytes were resolved using a C18 column and a mobile phase of 0.05 M sodium dodecyl sulfate—7.5% 1-propanol—0.5% triethylamine, buffered at pH 3 with phosphate salt, running under the isocratic mode. The signal was monitored by fluorescence. Validation was successfully performed according to the EU Commission Decision 2002/657/EC in terms of specificity, calibration range (LOQ to 1 mg/kg), linearity (R² > 0.9991), limit of detection and decision limit (0.01–0.05 mg/kg), limit of quantification (0.025–0.150 mg/kg), detection capability (<0.4 times decision limit), trueness (−14.2% to +9.8%), precision (<14.0%), robustness, and stability. The procedure was environmentally friendly, safe, easy-to-conduct, inexpensive, and had a high sample throughput, thus it is useful for routine analysis as a screening method in a laboratory for food residue control.

Reducing Veterinary Drug Residues in Animal Products: A Review

A survey we conducted suggests that the ingestion of veterinary drug residues in edible animal parts constitutes a potential health hazard for its consumers, including, specifically, the possibility of developing multidrug resistance, carcinogenicity, and disruption of intestinal normal microflora. The survey results indicated that antibiotics, parasitic drugs, anticoccidial, or nonsteroidal anti-inflammatory drugs (NSAIDs) are broadly used, and this use in livestock is associated with the appearance of residues in various animal products such as milk, meat, and eggs. We observed that different cooking procedures, heating temperatures, storage times, fermentation, and pH have the potential to decrease drug residues in animal products. Several studies have reported the use of thermal treatments and sterilization to decrease the quantity of antibiotics such as tetracycline, oxytetracycline, macrolides, and sulfonamides, in animal products. Fermentation treatments also decreased levels of penicillin and pesticides such as dimethoate, malathion, Dichlorodiphenyldichloroethylene, and lindane. pH, known to influence decreases in cloxacillin and oxacillin levels, reportedly enhanced the dissolution of antimicrobial drug residues. Pressure cooking also reduced aldrin, dieldrin, and endosulfan in animal products. Therefore, this review provides updated information on the control of drug residues in animal products, which is of significance to veterinarians, livestock producers, and consumer health.