Depletion of florfenicol and florfenicol amine residues in chicken eggs

A review on the antibiotic florfenicol: Occurrence, environmental fate, effects, and health risks

Florfenicol, as a replacement for chloramphenicol, can tightly bind to the A site of the 23S rRNA in the 50S subunit of the 70S ribosome, thereby inhibiting protein synthesis and bacterial proliferation. Due to the widespread use in aquaculture and veterinary medicine, florfenicol has been detected in the aquatic environment worldwide. Concerns over the effects and health risks of florfenicol on target and non-target organisms have been raised in recent years. Although the ecotoxicity of florfenicol has been widely reported in different species, no attempt has been made to review the current research progress of florfenicol toxicity, hormesis, and its health risks posed to biota. In this study, a comprehensive literature review was conducted to summarize the effects of florfenicol on various organisms including bacteria, algae, invertebrates, fishes, birds, and mammals. The generation of antibiotic resistant bacteria and spread antibiotic resistant genes, closely associated with hormesis, are pressing environmental health issues stemming from overuse or misuse of antibiotics including florfenicol. Exposure to florfenicol at μg/L-mg/L induced hormetic effects in several algal species, and chromoplasts might serve as a target for florfenicol-induced effects; however, the underlying molecular mechanisms are completely lacking. Exposure to high levels (mg/L) of florfenicol modified the xenobiotic metabolism, antioxidant systems, and energy metabolism, resulting in hepatotoxicity, renal toxicity, immunotoxicity, developmental toxicity, reproductive toxicity, obesogenic effects, and hormesis in different animal species. Mitochondria and the associated energy metabolism are suggested to be the primary targets for florfenicol toxicity in animals, albeit further in-depth investigations are warranted for revealing the long-term effects (e.g., whole-life-cycle impacts, multigenerational effects) of florfenicol, especially at environmental levels, and the underlying mechanisms. This will facilitate the evaluation of potential hormetic effects and construction of adverse outcome pathways for environmental risk assessment and regulation of florfenicol.

Veterinary pharmaceuticals and declining Cape Griffon Vulture (Gyps coprotheres) numbers: A potential threat to developing embryos

Cape Vultures (Gyps coprotheres) are a vulnerable Old-World Vulture species in southern Africa. Of the numerous threats to their survival, malicious and accidental poisonings remain a major concern. Despite the dangers of poisonings little is however known about the more insidious effects of toxins on egg survival, despite the species known to have a long generational length. For this study, an extensive literature review focusing on veterinary pharmaceuticals was undertaken. Literature for vultures was scarce, with most studies focusing on the domestic chicken. Using information for domestic chickens, the risk was characterised from likely vulture exposure to production animal carcasses with residues of said drugs. From this various antibiotics, medetomidine and albendazole were identified with embryotoxic or teratogenic effects. We suggest that these drugs be tested to elucidate their dose-response relationship and/or mitigation measures to minimise vulture exposure.

A generic avian physiologically-based kinetic (PBK) model and its application in three bird species

Physiologically-based kinetic (PBK) models are effective tools for designing toxicological studies and conducting extrapolations to inform hazard characterization in risk assessment by filling data gaps and defining safe levels of chemicals. In the present work, a generic avian PBK model for male and female birds was developed using PK-Sim and MoBi from the Open Systems Pharmacology Suite (OSPS). The PBK model includes an ovulation model (egg development) to predict concentrations of chemicals in eggs from dietary exposure. The model was parametrized for chicken (Gallus gallus), bobwhite quail (Colinus virginianus) and mallard duck (Anas platyrhynchos) and was tested with nine chemicals for which in vivo studies were available. Time-concentration profiles of chemicals reaching tissues and egg compartment were simulated and compared to in vivo data. The overall accuracy of the PBK model predictions across the analyzed chemicals was good. Model simulations were found to be in the range of 22-79% within a 3-fold and 41-89% were within 10- fold deviation of the in vivo observed data. However, for some compounds scarcity of in-vivo data and inconsistencies between published studies allowed only a limited goodness of fit evaluation. The generic avian PBK model was developed following a "best practice" workflow describing how to build a PBK model for novel species. The credibility and reproducibility of the avian PBK models were scored by evaluation according to the available guidance documents from WHO (2010), and OECD (2021), to increase applicability, confidence and acceptance of these in silico models in chemical risk assessment.

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.

Prenatal environmental antibiotics and fetal and postnatal growth: A biomonitoring-based prospective study in Eastern China

Thus far, the effect of environmental antibiotics exposure to offspring's growth remains unclear. Here we aimed to evaluate whether and to what extent environmental antibiotics exposure is associated with fetal and postnatal growth. A total of 735 pregnant women and their full-term offspring from the Shanghai Obesity Birth Cohort were involved in the study. Maternal urine specimen was collected during the third trimester, and urinary concentration of fifteen environmental antibiotics was measured by liquid chromatography-tandem mass spectrometry and enzymatic method. Children were followed at birth, 12, 24 and 60 months, and growth parameters of the weight and height of children were recorded. Linear regression model was applied, and it was found that maternal veterinary antibiotic (VA) concentration was negatively associated with birth weight and ponderal index [per natural-logarithm (ln)-unit: adjusted β (95% confidence interval, CI) = - 42.1 (- 74.0, - 10.3) for birth weight, -0.11 (- 0.19, - 0.02) for birth weight z-score, and - 0.03 (- 0.05, - 0.002) for ponderal index]. Regarding specific VA, each ln-unit increment of florfenicol concentrations was likely to be associate with 39.7 g (95%CI: - 69.3, - 10.1) reduced birth weight, 0.10 (95%CI: - 0.18, - 0.02) reduced birth weight z-score, and 0.02 g/cm³ (95%CI: - 0.04, - 0.00) reduced ponderal index. Ciprofloxacin, a preferred-as-veterinary antibiotic, showed a similar dose-response relationship with neonatal anthropometric parameters to florfenicol. However, these adverse effects diminished as children grew up to 12-, 24- and 60-month-old. Larger prospective cohort studies and animal experiments are warranted to verify the hypothesis that environmental antibiotics exposure in early life, even at low doses, may cause fetal growth restriction.

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.

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.

Validation of an UHPLC-MS/MS Method for Screening of Antimicrobial Residues in Eggs and Their Application to Analyses of Eggs from Laying Hens Subjected to Pharmacological Treatment

A multiresidue method by UHPLC/MS-MS was optimized and validated for the screening and semiquantitative detection of antimicrobials residues from tetracyclines, aminoglycosides, quinolones, lincosamides, β-lactams, sulfonamides, and macrolides families in eggs. A qualitative approach was used to ensure adequate sensitivity to detect residues at the level of interest, defined as maximum residue limit (MRL), or less. The applicability of the methods was assessed by analyzing egg samples from hens that had been subjected to pharmacological treatment with neomycin, enrofloxacin, lincomycin, oxytetracycline, and doxycycline during five days and after discontinuation of medication (10 days). The method was adequate for screening all studied analytes in eggs, since the performance parameters ensured a false-compliant rate below or equal to 5%, except for flumequine. In the analyses of eggs from laying hens subjected to pharmacological treatment, all antimicrobial residues were detected throughout the experimental period, even after discontinuation of medication, except for neomycin, demonstrating the applicability of the method for analyses of antimicrobial residues in eggs.

Florfenicol induces more severe hemotoxicity and immunotoxicity than equal doses of chloramphenicol and thiamphenicol in Kunming mice

Amphenicols are effective, broad-spectrum antibiotics that function by inhibiting the peptidyl transferase activity of bacteria, while the drugs can also inhibit mitochondrial protein synthesis in eukaryotes through the same mechanism, which leads to multi-organ toxicity. Some side effects of each drug have been studied, while differences in the severity of the hemotoxicities and immunotoxicities of amphenicols have not been reported. Thus, it is important to identify, evaluate, and compare the potential hemotoxicities and immunotoxicities to guide their proper use in humans and animals, which will guarantee food safety and animal welfare. Ovalbumin-immunized Kunming mice were gavaged daily with amphenicols for seven days. Blood samples were collected for hematology analysis, and measuring anti-ovalbumin antibody levels and serum intereukin-2 concentrations. The bone marrow, spleen and thymus were collected for histopathology and apoptosis analyzes. Bone marrow nucleated cells (BMNCs) and splenocytes were harvested to determine their cell cycle stages and to analyze lymphocyte proliferation. The results demonstrated that amphenicols, especially florfenicol (FLO), induced cell cycle arrest and apoptosis of hematopoietic cells, and it changed the bone marrow hematopoietic microenvironment by decreasing the number of peripheral blood cells. Moreover, amphenicols, especially FLO, induced hypoplasia and atrophy of the spleen and thymus, induced cell cycle arrest, as well as splenocyte apoptosis, and decreased the proliferation and viability of lymphocytes and the humoral and cellular immunity of the treated mice. These results suggest that amphenicols induce hemotoxicity and immunotoxicity to some extent, and that FLO induces more severe toxicity than equal doses of chloramphenicol (CAP) and thiamphenicol (TAP).