Pharmacokinetics of florfenicol in serum and seminal plasma in beef bulls

The objectives of this study were to compare the serum and seminal plasma pharmacokinetic profiles of florfenicol (FLO) and florfenicol amine (FLA) after the administration of FLO either by IM or SC routes in beef bulls. Four clinically healthy Hereford bulls underwent a comprehensive physical exam, including breeding soundness examination, CBC, and chemistry profile panel. Bulls were healthy and classified satisfactory potential breeders. In one group (n = 2), a single dose of FLO was administered SC in the middle of the neck at a dose of 40 mg/kg of body weight. In the second group (n = 2), a single dose was administered IM in the muscles of the neck at a dose of 20 mg/kg. Concentrations of FLO and FLA in serum and seminal plasma were determined by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Blood and semen samples were collected before the administration of FLO and at 12, 24, 36, 48, 72, 96, 120, 144, and 168 h after injection. The blood was collected from the coccygeal vessels, and semen was collected by electroejaculation. All samples were immediately refrigerated, processed within the first hour after collection, and finally stored at -80 °C. The mean level of total FLO in serum was higher when administered by the SC route (1,415.5 ng/mL) than by the IM route (752.4 ng/mL; P = 0.001). Differences were observed between the percentage of FLA in serum (1.8%; ranging from 1.3 to 2.9) and in seminal plasma (27.5%; ranging from 15.9 to 34.2; P = 0.0001). The mean level (±SD) of FLA was higher in seminal plasma compared to serum (467 ± 466 ng/mL and 18 ± 16 ng/mL, respectively; P = 0.001). The mean level of total FLO in seminal plasma was 1,454.8 ng/mL for the SC route and 1,872.9 ng/mL for the IM route without differences between the two routes (P = 0.51). Differences in the mean level of total FLO between serum and seminal plasma were detected (1,187 ± 2,069 ng/mL and 1,748 ± 1,906 ng/mL, respectively; P = 0.04). From the present investigation, it was concluded that FLO is a suitable antibiotic based on its pharmacokinetic attributes and may be employed for the treatment of bull genital infections when its use is indicated. To study the pharmacokinetics of FLO in seminal plasma, the analysis of FLA should be incorporated.

A Novel UHPLC-MS/MS Method for the Measurement of 25-Hydroxyvitamin D3 in Canine Serum and Its Application to Healthy Dogs

Several studies have shown the importance of vitamin D3 supplementation in small animals. In dogs, a low vitamin D3 status is associated not only with bone metabolism but also with different kinds of disorders, such as congestive heart failure, gastrointestinal diseases, chronic kidney diseases, and some types of cancer. However, it is crucial to maintain balance and monitor the introduction of this essential nutrient through the diet because over-supplementation can result in toxicity. Due to the clinical importance of assessing the vitamin D3 status in small animal patients, a quick, simple, and highly performing analytical method for its measurement is needed. In this study, we describe the development of a novel liquid chromatography-tandem mass spectrometry method for 25-hydroxyvitamin D3 quantification in canine serum. The approach was successfully validated following current European guidelines, proving excellent linearity (R2 always ≥0.996), accuracy (always within ±13%) and precision (always <10%). The application of the validated approach to samples collected from 40 healthy dogs made possible the definition of a reliable reference interval for 25-hydroxyvitamin D3, the main biomarker of vitamin D3. In addition, variations below 5% in the results obtained quantifying the same samples using a water-based calibration curve demonstrated that a surrogate matrix may be used without affecting data accuracy. Thanks to its simplicity, the proposed technique represents a useful tool for supporting clinical routine and investigating correlations between serum concentrations of this metabolite and multiple diseases. Additionally, it could enable the monitoring of supplementation in small animal patients in veterinary clinical practice.

Discovering the Protective Effects of Quercetin on Aflatoxin B1-Induced Toxicity in Bovine Foetal Hepatocyte-Derived Cells (BFH12)

Aflatoxin B1 (AFB1) induces lipid peroxidation and mortality in bovine foetal hepatocyte-derived cells (BFH12), with underlying transcriptional perturbations associated mainly with cancer, cellular damage, inflammation, bioactivation, and detoxification pathways. In this cell line, curcumin and resveratrol have proven to be effective in mitigating AFB1-induced toxicity. In this paper, we preliminarily assessed the potential anti-AFB1 activity of a natural polyphenol, quercetin (QUE), in BFH12 cells. To this end, we primarily measured QUE cytotoxicity using a WST-1 reagent. Then, we pre-treated the cells with QUE and exposed them to AFB1. The protective role of QUE was evaluated by measuring cytotoxicity, transcriptional changes (RNA-sequencing), lipid peroxidation (malondialdehyde production), and targeted post-transcriptional modifications (NQO1 and CYP3A enzymatic activity). The results demonstrated that QUE, like curcumin and resveratrol, reduced AFB1-induced cytotoxicity and lipid peroxidation and caused larger transcriptional variations than AFB1 alone. Most of the differentially expressed genes were involved in lipid homeostasis, inflammatory and immune processes, and carcinogenesis. As for enzymatic activities, QUE significantly reverted CYP3A variations induced by AFB1, but not those of NQO1. This study provides new knowledge about key molecular mechanisms involved in QUE-mediated protection against AFB1 toxicity and encourages in vivo studies to assess QUE's bioavailability and beneficial effects on aflatoxicosis.

Florfenicol and Florfenicol Amine Quantification in Bull Serum and Seminal Plasma by a Single Validated UHPLC-MS/MS Method

Florfenicol is a broad-spectrum antibiotic belonging to the amphenicols class that inhibits protein synthesis by binding to bacteria's ribosomal subunits. This drug is commonly used in veterinary medicine to treat bacterial infectious diseases in cattle, swine, poultry, and fish. The proposed method uses a quick protein precipitation with acetonitrile for the extraction of florfenicol and florfenicol amine in serum and seminal plasma, followed by analysis in UHPLC-MS/MS for their simultaneous quantification. A BEH C18 reversed-phase column was chosen for analyte separation, allowing to obtaining sharp and symmetrical peak shapes in a chromatographic run of just 3.5 min under programmed conditions. Two specific transitions were observed for each analyte, and florfenicol-d3 was used as the internal standard. The approach was fully validated in each matrix over ranges suitable for field concentrations of florfenicol and florfenicol amine, showing good linearity during each day of testing (R² always >0.99). Excellent accuracy and precision were demonstrated, for both analytes, by calculated bias always within ±15% and CV% always below 15% at all QC levels tested. The satisfactory outcomes obtained during recovery, matrix effect, and process efficiency investigations in serum and seminal plasma confirmed the strength of the method for the quantification of target compounds. To our knowledge, this is the first LC-MS/MS-validated approach for the quantification of florfenicol and florfenicol amine in serum and seminal plasma and was successfully applied for the determination of their concentration-time profiles in bulls. This paves the way to understanding the pharmacokinetics of this antibiotic and its active metabolite in bull's seminal plasma, which will enable the design of more appropriate treatment protocols.

Plant Essential Oils as a Tool in the Control of Bovine Mastitis: An Update

Bovine mastitis is a major concern for the dairy cattle community worldwide. Mastitis, subclinical or clinical, can be caused by contagious or environmental pathogens. Costs related to mastitis include direct and indirect losses, leading to global annual losses of USD 35 billion. The primary treatment of mastitis is represented by antibiotics, even if that results in the presence of residues in milk. The overuse and misuse of antibiotics in livestock is contributing to the development of antimicrobial resistance (AMR), resulting in a limited resolution of mastitis treatments, as well as a serious threat for public health. Novel alternatives, like the use of plant essential oils (EOs), are needed to replace antibiotic therapy when facing multidrug-resistant bacteria. This review aims to provide an updated overview of the in vitro and in vivo studies available on EOs and their main components as an antibacterial treatment against a variety of mastitis causing pathogens. There are many in vitro studies, but only several in vivo. Given the promising results of treatments with EOs, further clinical trials are needed.

The Use of Antibiotics and Antimicrobial Resistance in Veterinary Medicine, a Complex Phenomenon: A Narrative Review

As warned by Sir Alexander Fleming in his Nobel Prize address: “the use of antimicrobials can, and will, lead to resistance”. Antimicrobial resistance (AMR) has recently increased due to the overuse and misuse of antibiotics, and their use in animals (food-producing and companion) has also resulted in the selection and transmission of resistant bacteria. The epidemiology of resistance is complex, and factors other than the overall quantity of antibiotics consumed may influence it. Nowadays, AMR has a serious impact on society, both economically and in terms of healthcare. This narrative review aimed to provide a scenario of the state of the AMR phenomenon in veterinary medicine related to the use of antibiotics in different animal species; the impact that it can have on animals, as well as humans and the environment, was considered. Providing some particular instances, the authors tried to explain the vastness of the phenomenon of AMR in veterinary medicine due to many and diverse aspects that cannot always be controlled. The veterinarian is the main reference point here and has a high responsibility towards the human–animal–environment triad. Sharing such a burden with human medicine and cooperating together for the same purpose (fighting and containing AMR) represents an effective example of the application of the One Health approach.

Deepening the Whole Transcriptomics of Bovine Liver Cells Exposed to AFB1: A Spotlight on Toll-like Receptor 2

Aflatoxin B1 (AFB1) is a food contaminant metabolized mostly in the liver and leading to hepatic damage. Livestock species are differently susceptible to AFB1, but the underlying mechanisms of toxicity have not yet been fully investigated, especially in ruminants. Thus, the aim of the present study was to better characterize the molecular mechanism by which AFB1 exerts hepatotoxicity in cattle. The bovine fetal hepatocyte cell line (BFH12) was exposed for 48 h to three different AFB1 concentrations (0.9 µM, 1.8 µM and 3.6 µM). Whole-transcriptomic changes were measured by RNA-seq analysis, showing significant differences in the expression of genes mainly involved in inflammatory response, oxidative stress, drug metabolism, apoptosis and cancer. As a confirmatory step, post-translational investigations on genes of interest were implemented. Cell death associated with necrosis rather than apoptosis events was noted. As far as the toxicity mechanism is concerned, a molecular pathway linking inflammatory response and oxidative stress was postulated. Toll-Like Receptor 2 (TLR2) activation, consequent to AFB1 exposure, triggers an intracellular signaling cascade involving a kinase (p38β MAPK), which in turn allows the nuclear translocation of the activator protein-1 (AP-1) and NF-κB, finally leading to the release of pro-inflammatory cytokines. Furthermore, a p38β MAPK negative role in cytoprotective genes regulation was postulated. Overall, our investigations improved the actual knowledge on the molecular effects of this worldwide relevant natural toxin in cattle.

Enantiospecific pharmacokinetics of intravenous dexmedetomidine in beagles

The goal of this study was to investigate the pharmacokinetic (PK) behaviour of dexmedetomidine in dogs administered as a pure enantiomer versus as part of a racemic mixture. Eight unmedicated intact purpose‐bread beagles were included. Two intravenous treatments of either medetomidine or dexmedetomidine were administered at 10‐ to 14‐day intervals. Atipamezole or saline solution was administered intramuscularly 45 min later. Venous blood samples were collected into EDTA collection tubes, and the quantification of dexmedetomidine and levomedetomidine was performed by chiral LC–MS/MS. All dogs appeared sedated after each treatment without complication. Plasma concentrations of levomedetomidine were measured only in the racemic group and were 51.4% (51.4%–56.1%) lower than dexmedetomidine. Non‐compartmental analysis (NCA) was performed for both drugs, while dexmedetomidine data were further described using a population pharmacokinetic approach. A standard two‐compartment mammillary model with linear elimination with combined additive and multiplicative error model for residual unexplained variability was established for dexmedetomidine. An exponential model was finally retained to describe inter‐individual variability on parameters of clearance (Cl₁) and central and peripheral volumes of distribution (V₁, V₂). No effect of occurrence, levomedetomidine or atipamezole could be observed on dexmedetomidine PK parameters. Dexmedetomidine did not undergo significantly different PK when administered alone or as part of the racemic mixture in otherwise unmedicated dogs.

A single LC-MS/MS validated method for tulathromycin quantification in plasma, seminal plasma and urine to be applied in a pharmacokinetic study in bull

Tulathromycin is a macrolide antibiotic generally used for the treatment of respiratory diseases in cattle and swine. This work proposes an improvement of a previously published LC‐MS/MS method for tulathromycin determination in pig serum, here validated in three different bull matrices: plasma, seminal plasma, and urine. The approach is based on a quick protein precipitation with acetonitrile, filtration, and sample dilution before injection, allowing to rapidly process large batches of samples. Analytes separation was obtained using a BEH C18 (50 × 2.1 mm, 1.7 μm) column, maintained at 40°C with a chromatographic run of 5 min. The method was fully validated over concentration ranges suitable for field levels of tulathromycin found in each matrix (0.01–1 μg/ml for plasma, 0.05–5 μg/ml for seminal plasma, and 0.1–10 μg/ml for urine), showing good linearity during each day of testing (R² always >0.99). Accuracy and precision were within ±15% at all QC concentrations in all the three matrices. Furthermore, the use of tulathromycine‐d7 as internal standard mitigated the potential impacts of matrix effect. The validated technique was successfully applied to samples collected during a pharmacokinetic study in bulls, allowing to monitor tulathromycin concentrations over time in the three matrices. To our knowledge, this is the first validated approach for LC‐MS/MS quantification of tulathromycin in seminal plasma and urine.

Validation of a single UHPLC-MS/MS approach for oxytetracycline determination in bull plasma, seminal plasma and urine

Oxytetracycline is a broad‐spectrum antibiotic, which inhibits protein synthesis and is generally used for the treatment of pneumonia, shipping fever, leptospirosis and wound infections in cattle and swine. The present work proposes a novel liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for oxytetracycline quantification in bull plasma, seminal plasma and urine, requiring limited sample treatment before analysis. Extraction with trichloroacetic acid followed by dilution of the supernatant in mobile phase proved to be effective in all three matrices, allowing to rapidly process large batches of samples. Sharp and symmetrical peak shape was obtained using a BEH C18 reversed‐phase column in a chromatographic run of just 3.5 min. The mass spectrometer operated in positive electrospray ionization mode and monitored specific transitions for oxytetracycline (461.1 → 425.8) and the internal standard demeclocycline (465.0 → 447.6). The method was validated over concentration ranges suitable for field concentrations of oxytetracycline found in each matrix, showing good linearity during each day of testing (R² always >0.99), as also confirmed by analysis of variance (ANOVA) and lack‐of‐fit tests. Excellent accuracy and precision were demonstrated by calculated bias always within ±15% and CV% below 10% at all quality control (QC) levels in the three matrices. Matrix effect and recovery were investigated for both analytes, which showed consistent and comparable behaviour in each matrix. To our knowledge, this is the first validated approach for mass spectrometric determination of oxytetracycline in seminal plasma and urine. The method was successfully applied to samples collected during a pharmacokinetic study in bulls, allowing to assess the oxytetracycline concentration–time profile in plasma, seminal plasma and urine.

A critical point in chiral chromatography-mass spectrometry analysis of ketamine metabolites

Ketamine is a widely used dissociative drug, whose quantification in plasma and urine can be of pharmacological, toxicological, and clinical interest. Although tandem mass spectrometry allows the reliable determination of ketamine and its metabolites in biological matrices, the structural similarity between norketamine (main active metabolite) and dehydronorketamine (a less relevant metabolite) can represent a critical aspect. These compounds differ exclusively in two hydrogen atoms, but the consequent two‐unit difference in their mass/charge ratio is partially nullified by the isotopic abundance of the chlorine atom present in their structure. This, along with their similar fragmentation pattern, can result in the incorrect identification of the enantiomers of these ketamine metabolites even with triple quadrupole instruments, if shared transitions are monitored after chiral chromatography. The key to prevent norketamine overestimation is therefore observing analyte‐specific MS/MS transitions. Here, we describe in detail how we investigated this issue, during the development of an analytical method for ketamine and norketamine enantiomer determination in plasma.

A quick approach for medetomidine enantiomer determination in dog plasma by chiral liquid chromatography-tandem mass spectrometry and application to a pharmacokinetic study

In the present study, a rapid, sensitive and high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of medetomidine enantiomers in dog plasma was developed and validated. The separation and individual quantification of chiral compounds can be a tricky task in LC. This is particularly true when target analytes have a relatively small mass, as is the case with medetomidine, a potent and highly specific α2-adrenoceptor agonist widely used in both human and veterinary medicine. The proposed approach is based on a quick liquid-liquid extraction with ethyl acetate and filtration prior to injection. The optimized mobile phase composition allowed to perfectly separate the two enantiomers of medetomidine in a short chromatographic run time, using a cellulose tris(4-methylbenzoate)-based chiral column. A lower limit of quantification of 0.1 ng/mL was reached for both analytes thanks to the high sensitivity and selectivity of MS/MS and the use of racemic medetomidine-d3 as internal standard prevented potential matrix effect. Linearity was satisfying (R²  > 0.99) over the range 0.1-25 ng/mL, as well as within- and between-session accuracy and precision, both always <15%. This method was also applied with success to a series of samples from a pharmacokinetic (PK) study aimed at comparing dex- and levomedetomidine behaviour after administration of the racemic mixture in dogs. The simple extraction procedure, which allows reduced solvent and time consumption without compromising analytical performances, makes this technique a useful tool for this kind of applications even when small animals are involved, due to the small amount of sample required.