Waste control by waste: A new approach for antibiotic removal and metal reuse from livestock wastewater using ascorbic acid-enhanced CaO2/Cu(II) system.

Aiming at the coexistence of antibiotics and Cu(II) in livestock wastewater, a novelty strategy for the simultaneous removal of antibiotics and Cu ions by in-situ utilization of Cu(II) (i.e., CP/Cu(II) and CP/Cu(II)/ascorbic acid (AA) systems) was proposed. The removal rate of florfenicol (FF) in the CP/Cu(II)/AA system was 6.9 times higher than that of the CP/Cu(II) system. CP/Cu(II)/AA system was also effective in removing antibiotics from real livestock tailwater. Simultaneously, the removal of Cu ions in CP/Cu(II) and CP/Cu(II)/AA systems could reach 54.5 % and 15.7 %, respectively. The added AA could significantly enhance the antibiotics degradation but inhibit the Cu ions removal. HO•, O2•-, Cu(III), and •C-R were detected in the CP/Cu(II)/AA system, in which HO• was confirmed as the predominant contributor for FF degradation, and Cu(III) and •C-R also participated in FF elimination. The role of AA could accelerate HO• production and Cu(I)/Cu(II)/Cu(III) cycle, and form •C-R. The degradation products and pathways of FF in the CP/Cu(II)/AA system were proposed and the toxicity of the degradation products was evaluated by the toxicity analysis software (T.E.S.T). The results of this work suggest that without introducing complex catalysts, the feasibility of in-situ utilization of Cu(II) inherently or artificially introduced in livestock wastewater activating CP for antibiotic degradation and Cu ions removal was verified.

Quantification of florfenicol and its metabolites in fillets of Nile tilapia: Synthesis of metabolites and validation of an on-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry method.

This study concerns the synthesis of the florfenicol (FF) metabolites florfenicol amine (FFA), florfenicol alcohol (FFOH), and monochloroflorfenicol (FFCl), for their subsequent use as reference standards in On-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS) analysis. The metabolites were characterized using 1H and 13C NMR, as well as HRMS, and their purities were confirmed by quantitative NMR to ensure analytical reliability. Validation of the developed analytical method showed that it presented acceptable performance, with linearity >0.99 for all the target analytes, accuracies within ±10 % of nominal concentrations, and intra- and inter-day precisions within 15 %. Application of this method to fillets from fish that had been treated with florfenicol (dose of 10 mg/kg bw daily) demonstrated its effectiveness in consistently detecting FF and its metabolites throughout the treatment. The results emphasized the utility of the method for enhancing pharmacokinetic and residue depletion research. The ability to precisely monitor the drug and its metabolites in treated fish provides important insights into florfenicol metabolism, laying the groundwork for further comprehensive profiling studies of metabolites in fish tissue.

Florfenicol core-shell composite nanogels as oral administration for efficient treatment of bacterial enteritis.

To reduce the bitterness of florfenicol, avoid its degradation by gastric acid, and enhance its antibacterial activity against Escherichia coli by targeting and slowly releasing drugs at the site of intestinal infection, with pectin as an anion carrier and chitosan oligosaccharides (COS) as a cationic carrier, florfenicol-loaded COS@pectin core nanogels were self-assembled by electrostatic interaction and then encapsulated in sodium carboxymethylcellulose (CMCNa) shell nanogels through the complexation of CMCNa and Ca2+ to prepare florfenicol core-shell composite nanogels in this study. The florfenicol core-shell composite nanogels were investigated for their formula choice, physicochemical characterization, pH-responsive performances, antibacterial activity, therapeutic efficacy, and in vitro and in vivo biosafety studies. The results indicated that the optimized formula was 0.6 g florfenicol, 0.79 g CMCNa, 0.30 g CaCl2, 0.05 g COS, and 0.10 g pectin, respectively. In addition, the mean particle diameter, polydispersity index, zeta potential, loading capacity, and encapsulation efficiency were 124.0 ± 7.2 nm, -22.9 ± 2.5 mV, 0.42 ± 0.03, 43.4 % ± 3.1 %, and 80.5 % ± 3.4 %, respectively. The appearance, lyophilized mass, resolvability, scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and fourier transform infrared (FTIR) showed that the florfenicol core-shell composite nanogels were successfully prepared. Florfenicol core-shell composite nanogels had satisfactory stability, rheology, and pH-responsiveness, which were conducive to avoid degradation by gastric acid and achieve targeted and slow release at intestinal infection sites. More importantly, florfenicol core-shell composite nanogels had excellent antibacterial activity against Escherichia coli, a satisfactory therapeutic effect, and good palatability. In vitro and in vivo biosafety studies suggested the great promise of florfenicol core-shell composite nanogels. Therefore, the prepared florfenicol core-shell composite nanogels may be helpful for the treatment of bacterial enteritis as a biocompatible oral administration.

Electrochemical oxidation of Florfenicol in aqueous solution with mixed metal oxide electrode: Operational factors, reaction by-products and toxicity evaluation.

Veterinary antibiotics have become an emerging pollutant in water and wastewater sources due to excess usage, toxicity and resistance to traditional water and wastewater treatment. The present study explored the degradation of a model antibiotic- Florfenicol (FF) using electrochemical oxidation (EO) with Ti-RuO2/IrO2 anode. The anode material was characterized using SEM-EDS studies expressing stable structure and optimal interaction of the neighboring metal oxides with each other. The EDS results showed the presence of Ru, Ir, Ti, O and C elements with 6.44%, 2.57%, 9.61%, 52.74% and 28.64% atomic weight percentages, respectively. Optimization studies revealed pH 5, 30 mA cm-2 current density and 0.05 M Na2SO4 for 5 mg L-1 FF achieved 90% TOC removal within 360 min treatment time. The degradation followed pseudo-first order kinetics. LC-Q-TOF-MS studies revealed six predominant byproducts illustrating hydroxylation, deflourination, and dechlorination to be the major degradation mechanisms during the electrochemical oxidation of FF. Ion chromatography studies revealed an increase in Cl-, F- and NO3- ions as treatment time progressed with Cl- decreasing after the initial phase of the treatment. Toxicity studies using Zebrafish (Danio rerio) embryo showed the treated sample to be toxic inducing developmental disorders such as pericardial edema, yolk sac edema, spinal curvature and tail malformation at 96 h post fertilization (hpf). Compared to control, delayed hatching and coagulation were observed in treated embryos. Overall, this study sets the stage for understanding the effect of mixed metal oxide (MMO) anodes on the degradation of veterinary antibiotic-polluted water and wastewater sources using electrochemical oxidation.

Biochar reduces antibiotic transport by altering soil hydrology and enhancing antibiotic sorption.

The performance of biochar (BC) in reducing the transport of antibiotics under field conditions has not been sufficiently explored. In repacked sloping boxes of a calcareous soil, the effects of different BC treatments on the discharge of three relatively weakly sorbing antibiotics (sulfadiazine, sulfamethazine, and florfenicol) via runoff and drainage were monitored for three natural rain events. Surface application of 1 % BC (1 %BC-SA) led to the most effective reduction in runoff discharge of the two sulfonamide antibiotics, which can be partly ascribed to the enhanced water infiltration. The construction of 5 % BC amended permeable reactive wall (5 %BC-PRW) at the lower end of soil box was more effective than the 1 %BC-SA treatment in reducing the leaching of the most weakly sorbing antibiotic (florfenicol), which can be mainly ascribed to the much higher plant available and drainable water contents in the 5 %BC-PRW soil than in the unamended soil. The results of this study highlight the importance of BC's ability to regulate flow pattern by modifying soil hydraulic properties, which can make a significant contribution to the achieved reduction in the transport of antibiotics offsite or to groundwater.

Improving intestinal absorption and antibacterial effect of florfenicol via nanocrystallisation technology.

To study the effects of nanocrystallisation technology on the intestinal absorption properties and antibacterial activity of florfenicol (FF). The florfenicol nanocrystals (FF-NC) were prepared by wet grinding and spray drying. Additionally, changes in particle size, charge, morphology, and dissolution of FF-NC in the long-term stability were monitored by laser particle sizer, TEM, SEM, paddle method, and the structure of FF-NC powder was characterised by nuclear magnetic resonance (NMR) test. The antibacterial activity, intestinal absorption and intestinal histocompatibility of FF-NC were investigated by the stiletto, mini broth dilution susceptibility test, in situ single-pass intestinal perfusion (SPIP) and haematoxylin-eosin (H-E) staining. After 12 months of storage, the particle size and zeta potential of FF-NC were 280.43 ± 8.21 nm and -19.64 ± 3.45 mV, and the electron microscopy results showed that FF-NC were nearly circular with no adhesion between particles. In addition, the drug loading, encapsulation efficiency, and dissolution of FF-NC did not change significantly during storage. The inhibition zone of FF-NC against Escherichia coli and Staphylococcus aureus was 21.37 ± 1.70 mm and 25.17 ± 2.47 mm, respectively. Compared with the FF, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of FF-NC are reduced, and the absorption rate constant (Ka) and efficient permeability coefficient (Peff) of FF-NC in the three intestinal segments were increased by 1.28, 0.25, and 9.10 times and 0.59, 0.17, and 6.0 times, respectively. The results of tissue sections showed that FF-NC had little damage to the small intestinal. Nanocrystallisation technology is an effective method to increase the intestinal absorption and antibacterial activity of FF.

Chitosan Oligosaccharides Coupling Inhibits Bacterial Biofilm-Related Antibiotic Resistance against Florfenicol.

The formation of bacterial biofilms has increased the resistance of bacteria to various environmental factors and is tightly associated with many persistent and chronic bacterial infections. Herein we design a strategy conjugating florfenicol, an antibiotic commonly used in the treatment of streptococcus, with the antimicrobial biomaterial, chitosan oligosaccharides. The results demonstrated that the florfenicol-COS conjugate (F-COS) efficiently eradicated the mature Streptococcus hyovaginalis biofilm, apparently inhibiting drug resistance to florfenicol. A quantity of 250 µg/mL F-COS showed effective inhibitory activity against planktonic cells and biofilm of the bacteria, and a 4-fold improvement of the F-COS compared to unmodified florfenicol was observed. Furthermore, the conjugate showed a broad-spectrum activity against both Gram-positive and Gram-negative bacteria. It suggested that F-COS might have a potential for application in the treatment of biofilm-related infections.

Pharmacokinetics of thiamphenicol in Japanese quails (Coturnix japonica) after single intravenous and oral administrations.

Thiamphenicol (TP) pharmacokinetics were studied in Japanese quails (Coturnix japonica) following a single intravenous (IV) and oral (PO) administration at 30 mg/kg BW. Concentrations of TP were determined with HPLC and were analyzed by a noncompartmental method. After IV injection, elimination half-life (t1/2λz ), total body clearance (Cltot ) volume of distribution at steady state (Vdss ), and mean residence time (MRT) of TP were 3.83 hr, 0.19 L/hr/kg, 0.84 L/kg, and 4.37 hr, respectively. After oral administration of TP, the peak plasma concentration (Cmax ) was 19.81 µg/ml and was obtained at 2.00 hr (tmax ) postadministration. Elimination half-life (t1/2λz ) and mean absorption time (MAT) were 4.01 hr and 1.56 hr, respectively. The systemic bioavailability following oral administration of TP was 78.10%. TP therapy with an oral dosage of 30 mg/kg BW is suggested for a beneficial clinical effect in quails.

Increased bioaffinity and anti-inflammatory activity of florfenicol nanocrystals by wet grinding method.

Context: The main objective of the current study is to improve the water solubility of florfenicol (FF) and evaluate changes in its pharmacokinetics and anti-inflammatory activity.Materials and methods: Florfenicol nanocrystals (FF-NC) were prepared by wet grinding combined with spray drying. The characterisations, pharmacokinetics, and anti-inflammatory activity of FF-NC were evaluated.Results: The particle size, polydispersity index (PDI), and zeta potential of FF-NC were 276.4 ± 19.4 nm, 0.166 ± 0.011, and -18.66 ± 5.25 mV, respectively. Compared with FF, FF-NC showed a better dissolution rate in media at different pH. Pharmacokinetic experiments showed the area under the curve (AUC0-t), maximum concentration (Cmax), and mean residence time (MRT) of FF-NC were about 4.62-fold, 2.86-fold, and 1.68-fold higher compared with FF, respectively. In vitro anti-inflammatory experiments showed that FF inhibited the secretion of tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), and synthesis of NO in a dose-dependent manner, while FF-NC showed a stronger anti-inflammatory effect than FF under the same dose.Conclusion: FF-NC are an effective way to improve the bioaffinity and anti-inflammatory effects of FF.

Comparative muscle irritation and pharmacokinetics of florfenicol-hydroxypropyl-ß-cyclodextrin inclusion complex freeze-dried powder injection and florfenicol commercial injection in beagle dogs.

Florfenicol (FF) is a novel animal-specific amidohydrin broad-spectrum antibiotic. However, its aqueous solubility is extremely poor, far below the effective dose required for veterinary clinic. Thus, FF is often used in large doses, which significantly limits its preparation and application. To overcome these shortcomings, the FF-hydroxypropyl-ß-cyclodextrin (FF-HP-ß-CD) inclusion complexes were developed using the solution-stirring method. The physical properties of FF-HP-ß-CD were characterized. A comparison was conducted between FF and FF-HP-ß-CD freeze-dried powder injection of their muscle irritation and the pharmacokinetics. The drug loading and saturated solubility of FF-HP-ß-CD at 37 °C were 11.78% ± 0.04% and 78.93 ± 0.42 mg/mL, respectively (35.4-fold compared with FF). Results of scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, and Fourier transform infrared showed that FF was entrapped in the inner cavity of HP-ß-CD, and the inclusion complex formed in an amorphous state. In comparison with FF commercial injection, FF-HP-ß-CD increased the elimination half-life (t1/2ß), transport rate constant (K10, K12, K21), and maximum concentration (Cmax) after intramuscular injection in beagle dogs. Conversely, it decreased the distribution half-life (t1/2α), absorption rate constant (Ka), apparent volume of distribution (V1/F), and peak time (Tmax). These results suggest that FF-HP-ß-CD freeze-dried powder injection is a promising formulation for clinical application.

Sustained-release microparticle dry powders of chloramphenicol palmitate or thiamphenicol palmitate prodrugs for lung delivery as aerosols.

The purpose of this study was to design inhalable sustained-release nanoparticle-in-microparticles, i.e. nano-embedded microparticles, for the lung delivery of chloramphenicol or thiamphenicol as aerosols. The palmitate ester prodrugs of the two antibiotics were used to prepare PLGA-based nanoparticles or to form pure prodrug nanoparticles. Prodrug-loaded PLGA nanoparticles or pure prodrug nanoparticles were prepared using the emulsion-solvent evaporation method. Dry microparticle powders for inhalation were then produced by spray-drying the nanoparticle suspensions supplemented with lactose as a bulking agent and L-leucine as a dispersing enhancer. Examined under the scanning electron microscopy, the obtained microparticles appeared to be spherical and shriveled, with no crystal-like structures. Drug loading was satisfactory (14 to 34% (m/m)) and the aerodynamic properties determined with a Next Generation Impactor were appropriate for lung delivery, with mass median aerodynamic diameters close to 3 µm. The in vitro release profiles showed that sustained released was achieved with these formulations, with an almost complete release over 14 days.

Determination of total florfenicol residues as florfenicol amine in bovine tissues and eel by liquid chromatography-tandem mass spectrometry using external calibration.

A reliable liquid chromatography-tandem mass spectrometry method was developed to determine total florfenicol residues in bovine tissues and eel. Florfenicol and its metabolites (florfenicol amine, monochloroflorfenicol, florfenicol oxamic acid, and florfenicol alcohol) were analyzed as the marker residue, florfenicol amine, as defined by several regulatory agencies. After hydrolysis with hydrochloric acid, samples were defatted and subjected to solid-supported liquid extraction and Oasis MCX-cartridge cleanup before analysis. The method was validated for florfenicol and its metabolites at two levels in eel and bovine muscle, fat, and liver. Excellent recoveries were obtained (93-104%), with relative standard deviations of <6% for all compounds. Negligible matrix effects and minimal analyte loss during sample preparation enabled accurate quantification by external calibration using solvent standards. No interfering peaks were observed around the retention time of florfenicol amine, indicating the high selectivity of the method. Retention times in the spiked samples corresponding to that of the calibration standard in solvent did not exceed ±0.1 min. Ion ratios from the spiked sample were within ±10% (relative) of the calibration standards. Calibration curves were linear in the range of 0.5 to 100 ng/mL, with coefficients of determination higher than 0.998. The limits of quantification and limits of detection of the proposed method were estimated to be 0.01 mg/kg and 0.0005 mg/kg, respectively, in all food samples. Thus, the developed method is considered reliable and suitable for regulatory use.

Biochar-mediated sorption of antibiotics in pig manure.

Using manure contaminated with antibiotics as fertilizer is a primary source of soil pollution with antibiotics and concomitantly with antibiotic resistance genes (ARG). Bioavailable antibiotics trigger further ARG amplification during manure storage. Consequently it is aimed to facilitate the immobilization of antibiotics in manure. To this end, five biochars derived from pine cone (BCP), rice husk, sewage sludge, digestate and Miscanthus were tested as additional sorbents in liquid pig manure for sulfamethazine, ciprofloxacin, oxytetracycline and florfenicol. Non-linear sorption was best-fit using the Freundlich isotherm (R2 > 0.82) and the pseudo-second-order model best described sorption kinetics (R2 > 0.94). Antibiotics' sorption onto manure increased in the order sulfamethazine < florfenicol < ciprofloxacin < oxytetracycline. Admixtures of BCP to manure changed the order to sulfamethazine < oxytetracycline < florfenicol = ciprofloxacin. Generally, with the addition of biochar, sorption coefficients of florfenicol increased most (by factors>2.7) followed by sulfamethazine and ciprofloxacin. Yet, oxytetracycline was mostly mobilized probably due to competitive adsorption. Effects depended on the proportion of biochar added and the type of biochar, whereby plant-derived biochar exhibited better immobilization of antibiotics. Depending on the type and portion of biochar, admixtures to manure can be used to lower the mobility and hence bioavailability of fenicols, fluoroquinolones and sulfonamides.

pH-Controlled Drug Release by Diffusion through Silica Nanochannel Membranes.

We report in this work the fabrication of a flow-through silica nanochannel membrane (SNM) for controlled drug release applications. The ultrathin SNM consists of parallel nanochannels with a uniform diameter of ∼2.3 nm and a density of 4 × 1012 cm-2, which provide simultaneously high permeability and size selectivity toward small molecules. The track-etched porous polyethylene terephthalate film premodified with silane on its surface was used to support the ultrathin SNM via irreversible covalent bond formation, thus offering mechanical strength, flexibility, and stability to the ultrathin SNM for continuous and long-term use. Alkylamines were subsequently grafted onto the SNM surface to modulate the "on" and "off" state of nanochannels by medium pH for controlled drug release. Thiamphenicol glycinate hydrochloride (TPG), an intestinal drug, was studied as a model to permeate through an ultrathin SNM in both simulated gastric fluid (pH = 1.2) and simulated intestinal fluid (pH = 7.5). The release in the latter case was 178 times faster than that in the former. Moreover, a nearly zero-order constant release of TPG via single-file diffusion was achieved up to 24 h, demonstrating the feasibility of sustained and continuous release of small-molecule drugs in a pH-controlled manner.

Preparation, characterization, and pharmacokinetics in swine of a florfenicol enteric formulation prepared using hot-melt extrusion technology.

The objective of this work was to manufacture an enteric formulation of florfenicol (FF) using hot-melt extrusion (HME) technology and to evaluate its in vitro dissolution and in vivo pharmacokinetics. For the HME process, hypromellose acetate succinate LG (HPMCAS-LG) was the enteric polymer mixed with FF, and the two components were extruded with a standard screw configuration at a speed of 50 rpm. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and Fourier transform infrared spectroscopy (FT-IR) were performed to characterize the HME extrudate. The release percentage of the enteric formulation in the acidic stage was <10% of the loaded FF, whereas that in the phosphate buffer stage was >80%. Pharmacokinetic evaluations in swine revealed that the enteric formulation had a longer t1/2λ and MRT than commercially available FF powder (FULAIKA® ), indicating that the novel formulation exhibited enteric and sustained release properties. Compared with the commercial product, the relative bioavailability of the enteric formulation reached up to 117.2%. This study suggests that this formulation may have potential for future commercialization.

Medicinal Plants Based Products Tested on Pathogens Isolated from Mastitis Milk.

Bovine mastitis a major disease that is commonly associated with bacterial infection. The common treatment is with antibiotics administered intramammary into infected quarters of the udder. The excessive use of antibiotics leads to multidrug resistance and associated risks for human health. In this context, the search for alternative drugs based on plants has become a priority in livestock medicine. These products have a low manufacturing cost and no reports of antimicrobial resistance to these have been documented. In this context, the main objective of this study was to determine the antimicrobial effect of extracts and products of several indigenous, or acclimatized plants on pathogens isolated from bovine mastitis. A total of eleven plant alcoholic extracts and eight plant-derived products were tested against 32 microorganisms isolated from milk. The obtained results have shown an inhibition of bacterial growth for all tested plants, with better results for Everniaprunastri, Artemisiaabsinthium, and Lavandulaangustifolia. Moreover, E.prunastri, Populus nigra, and L. angustifolia presented small averages of minimum inhibitory and bactericidal concentrations. Among the plant-derived products, three out of eight have shown a strong anti-microbial effect comparable with the effect of florfenicol and enrofloxacin, and better than individual plant extracts possibly due to synergism. These results suggest an important anti-microbial effect of these products on pathogens isolated from bovine mastitis with a possible applicability in this disease.

Preparation and Performance of Poly(D,L-lactic acid)­Polyethylene Glycol­Poly(D,L-lactic acid) Electrospun Fibrous Membranes for Drug Release.

In this study, poly(D,L-lactic acid)­polyethylene glycol­poly(D,L-lactic acid), hereafter referred to as PDLLA­PEG­PDLLA, triblock copolymer membranes were prepared by electrospinning. Scanning electron microscopy images revealed the morphology of the microfibers, which had a diameter ranging from 300 to 900 nm. Fourier transform infrared spectroscopy was employed for structural analysis of the PDLLA­PEG­PDLLA/florfenicol (FF) membranes, which exhibited three absorption peaks at 3455, 1684, and 1533 cm−1, respectively, indicating that the triblock copolymer and FF are very well blended in the composite membranes. Differential scanning calorimetry revealed that weak interaction possibly decreased the activity of the segment and elevated the T g from 43 °C to 46 °C. From the in vitro dissolution tests, PDLLA as a biodegradable and biocompatible polymer can improve the solubility of FF. The rate of drug release increased with increasing PEG proportion. Furthermore, tensile and nanoindentation tests demonstrated that nanofibers exhibit mechanical properties such as tensile stress (700­2800 KPa), strain (40­120%), and good toughness (0.28­0.98 GPa). In conclusion, PDLLA­PEG­PDLLA nanofibers as a carrier improve the solubility of FF and control drug release.

Advances on the chromatographic determination of amphenicols in food.

Antibiotics are widely used in veterinary medicine to treat and prevent diseases and their residues can remain in food of animal origin causing adverse effects to human health. Amphenicols (chloramphenicol, thiamphenicol, and florfenicol) may be found in foodstuffs, although the use of chloramphenicol has been prohibited in many countries due to its high toxicity. Since these antibiotics are usually present at trace levels in food, sensitive and selective techniques are required to detect them. This paper reviews analytical methods used since 2002 for the quantitative analysis of amphenicols in food. Sample preparation and separation/detection techniques are described and compared. The advantages and disadvantages of these procedures are discussed. Furthermore, the worldwide legislation and occurrence of these antibiotics in food matrices as well as future trends are also presented.

Depletion of florfenicol in lactating dairy cows after intramammary and subcutaneous administration.

Eighteen Holstein dairy cows ranging in body weight from 500-700 kg and with an average milk yield of 37 ± 6 kg/day were used to investigate the depletion of florfenicol (FFL) in milk and plasma of dairy cows. Three groups of six were administered FFL: Group A, intramammary (IMM) infusion of ~2.5 mg FFL/kg BW at three consecutive milking intervals (total amount of ~7.5 mg/kg BW); Group B, one IMM infusion (20 mg/kg BW) into one quarter and Group C, one subcutaneous (SC) treatment (40 mg/kg BW). IMM infusions were into the right front quarter. Cows were milked daily at 06:00 and 18:00 h. The highest concentrations (Cmax ) and time to Cmax (Tmax ) were: 1.6 ± 2.2 µg·FFL/mL milk at 22 h (Group A), 5.5 ± 3.6 µg·FFL/mL milk at 12 h (Group B), and 1.7 ± 0.4 µg·FFL/mL milk at 12 h (Group C). The half-lives (t1/2 ) were ~19, 5.5, and 60 h, for Groups A, B, and C, respectively. FFL was below the limit of detection (LOD) by 60 h in three Group B cows, but above the LOD at 72, 84, and 120 h in three cows. FFL was above the LOD in milk from Group C's cows for 432-588 h. Plasma values followed the same trends as milk. The results demonstrate that IMM-infused FFL is bioavailable and below the LOD within 72-120 h. The concentration of FFL was detectable in both plasma and milk over the course of 2-3 weeks after SC administration. The absence of residue depletion data presents problems in determining safe levels of FFL residues in milk and edible tissues. The data presented here must not be construed as approval for extra-label use in food animals.

Effects of thiamphenicol on nitrate reduction and N2O release in estuarine and coastal sediments.

Nitrate overload is an important driver of water pollution in most estuarine and coastal ecosystems, and thus nitrate reduction processes have attracted considerable attention. Antibiotics contamination is also an emerging environmental problem in estuarine and coastal regions as a result of growing production and usage of antibiotics. However, the effects of antibiotics on nitrate reduction remain unclear in these aquatic ecosystems. In this study, continuous-flow experiments were conducted to examine the effects of thiamphenicol (TAP, a common chloramphenicol antibiotic) on nitrate reduction and greenhouse gas N2O release. Functional genes involved in nitrogen transformation were also quantified to explore the microbial mechanisms of the TAP influence. Production of N2 were observed to be inhibited by TAP treatment, which implied the inhibition effect of TAP on nitrate reduction processes. As intermediate products of nitrogen transformation processes, nitrite and N2O were observed to accumulate during the incubation. Different TAP inhibition effects on related functional genes may be the microbial mechanism for the changes of nutrient fluxes, N2 fluxes and N2O release rates. These results indicate that the antibiotics residues in estuarine and coastal ecosystems may contribute to nitrate retention and N2O release, which could be a major factor responsible for eutrophication and greenhouse effects.