Florfenicol Concentrations Research Articles

Development and application of a population physiologically based pharmacokinetic model for florfenicol and its metabolite florfenicol amine in cattle

Florfenicol (FF) is used in cattle to treat respiratory diseases but could result in tissue residues. This study aimed to develop a population physiologically based pharmacokinetic (PBPK) model to predict the concentrations of FF and its metabolite, florfenicol amine (FFA), in cattle after four different routes of administration, and to calculate and compare the withdrawal intervals (WDIs) with approved withdrawal times based on different marker residues and their MRLs or tolerances. A flow-limited PBPK model including both FF and FFA sub-models were developed with published data using acslXtreme. This model predicted FF and FFA concentrations in tissues and plasma/serum after intramuscular or subcutaneous administration. Based on the model, the WDIs of 46 and 58 days were calculated to ensure that total residue concentrations (FF + FFA) in 95th percentile of the population after intramuscular and subcutaneous administration were below the MRL, respectively. WDIs were calculated as 44 and 47 days to ensure that FFA concentrations after intramuscular and subcutaneous administration fell below tolerances in 99th percentile of the population, respectively. WDIs were longer than the corresponding label in China, US, and EU. This model provides a useful tool to predict tissue residues of FF and FFA in cattle to improve food safety.

Pharmacokinetics of florfenicol and its metabolite florfenicol amine in crucian carp (Carassius auratus) at three temperatures after single oral administration

The pharmacokinetic profiles of florfenicol (FF) and florfenicol amine (FFA) following a single oral dose of FF at 10 mg·kg−1 body weight were compared in crucian carp reared at three different temperatures of fresh water. The concentrations of FF and FFA were determined simultaneously by high-performance liquid chromatography coupled with fluorescence detection, followed by compartmental analysis using a one-compartment open model. At water temperatures of 10 ± 0.5, 20 ± 0.5, and 25 ± 0.5 °C, the maximum concentration (Cmax) of FF was 2.435, 2.795, and 3.555 μg·mL−1, respectively, while that of FFA was 0.810, 0.945, and 1.063 μg·mL−1, respectively. The absorption half-life (t1/2ka) of FF was 0.72, 0.73, and 0.70 h, and the elimination half-life (t1/2kel) was 22.86 12.29, and 9.56 h, respectively. The volume of distribution per fraction absorbed (Vd/F) for FF at water temperatures of 10, 20, and 25 °C was 3.67, 2.99, and 2.29 L·kg−1, respectively. For FFA, the formation half-life (t1/2kf) was 2.13, 3.47, and 5.11 h, respectively, whereas the t1/2kel was 27.79, 20.33, and 15.44 h at water temperatures of 10, 20, and 25 °C, respectively. At higher water temperatures, FF was absorbed and eliminated more quickly and was more extensively distributed than at lower water temperatures; in addition, the formation and elimination of FFA were faster at higher water temperatures. From the values of time > minimum inhibitory concentration (T > MIC) calculated in the current study at 10 °C, an oral dose of FF at 10 mg·kg−1 body weight administered at 48-h intervals would be sufficient for the treatment of bacterial infection with an MIC of ≤0.5 μg·mL−1, whereas a 24-h interval would be necessary at 20 and 25 °C to treat bacterial infections with the same MIC.

Effects of anemoside B4 on pharmacokinetics of florfenicol and mRNA expression of CXR, MDR1, CYP3A37 and UGT1E in broilers.

Pulsatillae radix, a traditional Chinese medicine (TCM), is often used in combination with florfenicol for treatment of intestinal infection in Chinese veterinary clinics. Anemoside B4 (AB4) is the major effective saponin in Pulsatillae radix. This study aimed to investigate whether the pharmacokinetics of florfenicol in broilers was affected by the combination of AB4. In this study, broilers were given AB4 (50 mg/kg BW), or 0.9% sodium chloride solution by oral administration for 7 days. They were then fed florfenicol orally (30 mg/kg BW) on the eighth day. The results showed that the AUC(0-∞), MRT(0-∞), t1/2z and Cmax of florfenicol were significantly decreased, and the Vz/F and CLz/F were significantly increased by AB4; the mRNA expression levels of CXR, CYP3A37 and MDR1 (except CXR and CYP3A37 in the liver) were up-regulated by AB4. In conclusion, AB4 altered the pharmacokinetics of florfenicol, resulting in lower plasma concentrations of florfenicol, this was probably related to the mRNA expression of CXR, CYP3A37 and MDR1 in the jejunum and liver (except CXR and CYP3A37) increased by AB4. The implications of these findings on the effect of traditional Chinese medicine containing AB4 on the effectiveness of florfenicol in veterinary practice deserve study.

Temperature-dependent pharmacokinetics of florfenicol in Nile tilapia (Oreochromis niloticus) following single oral and intravenous administration

Temperature-dependent pharmacokinetics (PK) have rarely been reported in tilapia despite there are popularly cultured worldwide, ranging from tropical to temperate climates. The present study aims to investigate the PK characteristics of florfenicol (FF) in Nile tilapia at 3 temperature levels (24, 28, and 32 °C) after single intravenous (IV) and oral (PO) dose of 15 mg/kg to evaluate the effects of temperature on PK. The serum concentrations of FF were analyzed by HPLC-UV method and PK characteristics were analyzed by 2-compartmental model. It was revealed that temperature has profound influences on certain PK parameters. The results from both IV and PO experiments were generally similar. Increasing water temperature from 24 to 32 °C led to significantly increased elimination rate constant (β) from 0.056 to 0.095 1/h and shortened elimination half-life (t1/2β) from 12–13 h to 7–8 h. The absorption half-life (t1/2Ka) were decreased from 2.28 to 1.18 h as well as the maximum serum concentration (Cmax) from 23.14 to 16.71 μg/mL and time to reach Cmax (Tmax) from 1.40 to 0.75 h. The area under the serum concentration-time curves (AUC) were reduced by half while the clearances were doubled and the volume of distributions (Vd) were significantly increased. Our results also demonstrated that for FF in Nile tilapia the temperature coefficient (Q10) values could be applied to predict the CL and β at a specific temperature with high accuracy (94–116%). The temperature-sensitive PK parameters such as the increase in Ka, Vd, and β significantly affected the serum concentrations and its overall exposure (AUC), thereby could potentially implicate that proper dosing regimen should take water temperature into consideration. The study highlighted the possibility of water temperature effect on therapeutic outcome of FF used in tilapia and likely other cichlids.

Assessment of Three Antimicrobial Residue Concentrations in Broiler Chicken Droppings as a Potential Risk Factor for Public Health and Environment

Tetracyclines, sulfonamides and amphenicols are broad spectrum antimicrobial drugs that are widely used in poultry farming. However, a high proportion of these drugs can be excreted at high concentrations in droppings, even after the end of a therapy course. This work intended to assess and compare concentrations of florfenicol (FF), florfenicol amine (FFa), chlortetracycline (CTC), 4-epi-chlortetracycline (4-epi-CTC), and sulfachloropyridazine (SCP) in broiler chicken droppings. To this end, 70 chickens were housed under controlled environmental conditions, and assigned to experimental groups that were treated with therapeutic doses of either 10% FF, 20% CTC, or 10% SCP. Consequently, we implemented and designed an in-house validation for three analytical methodologies, which allowed us to quantify the concentrations of these three antimicrobial drugs using liquid chromatography coupled to mass spectrometry (LC-MS/MS). Our results showed that FF and FFa concentrations were detected in chicken droppings up to day 10 after ceasing treatment, while CTC and 4-epi-CTC were detected up to day 25. As for SCP residues, these were detected up to day 21. Noticeably, CTC showed the longest excretion period, as well as the highest concentrations detected after the end of its administration using therapeutic doses.

Intracellular Accumulation of Linezolid and Florfenicol in OptrA-Producing Enterococcus faecalis and Staphylococcus aureus.

The optrA gene, which confers transferable resistance to oxazolidinones and phenicols, is defined as an ATP-binding cassette (ABC) transporter but lacks transmembrane domains. The resistance mechanism of optrA and whether it involves antibiotic efflux or ribosomal protection remain unclear. In this study, we determined the MIC values of all bacterial strains by broth microdilution, and used ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry to quantitatively determine the intracellular concentrations of linezolid and florfenicol in Enterococcus faecalis and Staphylococcus aureus. Linezolid and florfenicol both accumulated in susceptible strains and optrA-carrying strains of E. faecalis and S. aureus. No significant differences were observed in the patterns of drug accumulation among E. faecalis JH2-2, E. faecalis JH2-2/pAM401, and E. faecalis JH2-2/pAM401+optrA, but also among S. aureus RN4220, S. aureus RN4220/pAM401, and S. aureus RN4220/pAM401+optrA. ANOVA scores also suggested similar accumulation conditions of the two target compounds in susceptible strains and optrA-carrying strains. Based on our findings, the mechanism of optrA-mediated resistance to oxazolidinones and phenicols obviously does not involve active efflux and the OptrA protein does not confer resistance via efflux like other ABC transporters.

Pharmacokinetic profiles of florfenicol in spotted halibut, Verasper variegatus, at two water temperatures.

The pharmacokinetic profiles of florfenicol in the spotted halibut (Verasper variegatus) were investigated at 15 and 20°C water temperatures, respectively. Florfenicol content in plasma samples was analyzed using an HPLC method. Drug concentration versus time data were best fitted to a three-compartment model after a single intravenous administration (15mg/kg BW), and fitted to a two-compartment model after an oral administration (30mg/kg BW) at 15 and 20°C. The florfenicol concentration in the blood increased slowly during the 12hr following an oral administration at 15°C, with a peak concentration (Cmax ) of 9.1mg/L, and then declined gradually. The half-lives of absorption, distribution, and elimination phase were 2.18, 5.66 and 14.25hr, respectively. The bioavailability (F) was calculated to be 24.14%. After an oral administration at 20°C, shorter half-lives of absorption (1.33hr), distribution (2.51hr) and elimination (9.71hr), a higher Cmax (12.2mg/L), and a similar F (23.98%) were found. Based on the pharmacokinetics and pharmacodynamics, an oral dose of 30mg/kg BW was suggested to be efficacious for bacterial disease control in spotted halibut farming.

Similar Gastro-Intestinal Exposure to Florfenicol After Oral or Intramuscular Administration in Pigs, Leading to Resistance Selection in Commensal Escherichia coli.

Florfenicol, which is licensed for veterinary use only, proves to be a potent antimicrobial for treatment of respiratory disease. However, the subsequent exposure of the gut microbiota to florfenicol is not well described. Hence, the effect of various administration protocols on both plasma and gastro-intestinal florfenicol concentrations in pigs was evaluated. In field situations were simulated by application of different administration routes and dosages [single oral bolus at 10 or 5 mg/kg body weight (BW), medicated feed at 10 or 5 mg/kg BW and intramuscular injections at 15 or 30 mg/kg BW]. After intramuscular administration of 30 mg florfenicol/kg BW, gastro-intestinal concentrations of florfenicol, quantified 10 h after the last administration, were significantly elevated in comparison with the other treatment groups and ranging between 31.5 and 285.8 μg/g over the different gut segments. For the other treatment groups, the influence of dose and administration route was not significantly different. Bacteriological analysis of the fecal samples from the animals at the start of the experiment, demonstrated the presence of both florfenicol susceptible (with minimal inhibitory concentration (MIC) values of 2–16 μg/mL) and florfenicol resistant (MIC ≥ 256 μg/mL) Escherichia coli isolates in all treatment groups. Following, at 10 h after the last administration the susceptible E. coli population was eradicated in all treatment groups due to the high intestinal florfenicol concentrations measured. Moreover, selection of the resistant E. coli strains during treatment occurred in all groups. This is likely related to the fact that the different treatment strategies led to high gastro-intestinal concentrations albeit not reaching the high magnitude of MIC values associated with florfenicol resistance (≥256 μg/mL). Conclusively, in our experimental setup the administration route and dose alterations studied, had no influence on monitored florfenicol resistance selection in E. coli from the microbiota.

Pharmacokinetics of florfenicol and its metabolite florfenicol amine in crucian carp (Carassius auratus) at three temperatures after one single intramuscular injection

The pharmacokinetic profiles of florfenicol (FF) or florfenicol amine (FFA) in crucian carp were compared at different water temperatures after single intramuscular administration of FF at 10mg/kg bodyweight. The concentrations of FF and FFA were determined by a high-performance liquid chromatography method, and then, the concentration versus time data were subjected to compartmental analysis using a one-compartment open model. At the water temperatures of 10, 20, and 25°C, the peak concentrations (Cmax s) of FF were 2.28, 2.29, and 2.34μg/ml, respectively, while those of FFA were 0.42, 0.71, and 0.82μg/ml, respectively. And the absorption half-life (t1/2ka ) of FF was 0.21, 0.19, and 0.21hr, while the elimination half-life (t1/2kel ) was 31.66, 24.77, and 21.48hr, respectively. For FFA, the formation half-life (t1/2kf ) was 3.85, 8.97, and 12.43hr, while the t1/2kel was 58.34, 30.27, and 21.22hr, respectively. The results presented here demonstrated that the water temperature had effects on the elimination of both FF and FFA and the formation of FFA. Based on the T>MIC values calculated here, to treat the infections of bacterial with MIC value≤0.5μg/ml, FF intramuscularly given at 10mg/kg bodyweight with a 72-hr interval is sufficient at the water temperature of 10°C, while the intervals of 60 and 48hr were needed at 20 and 25°C, respectively. But to treat bacterial with higher MIC values, more FF or FF at 10mg/kg BW but with shorter intervals should be intramuscularly given to the infected fish.

Bioequivalence evaluation of Florfenicol pharmaceutics in pigs using liquid chromatography-tandem mass spectrometry

ABSTRACTThe bioequivalence of two Florfenicol (FF) products in pigs was evaluated. A 2 × 2 crossover trial with a 14 days wash-out period was performed. The pigs were orally administered in a single dose (2 mg/kg b.w of FF). Serum samples were analyzed using a liquid chromatography-tandem mass spectrometry method. The limit of quantification was 0.1 ng/mL, and the calibration range was 1.0–100.0 ng/mL. Furthermore, intraday and interday were 5.43–9.09% and 6.23–9.68%, respectively. The areas under the curve (AUC0–48) for the test product B of FF and reference product A were 7289.61 ± 1750.44 and 6545.01 ± 2766.25 h × ng/mL, respectively. The highest concentrations of FF in the serum (Cmax) were 726.05 ± 211.77 and 641.97 ± 117.94 ng/mL. The mean retention times (MRT) was 7.91 ± 1.98 and 7.76 ± 2.89 h while the half-lives (T1/2) were 4.07 ± 1.71 and 4.99 ± 3.30 h. From the analysis of variance results, the p values of Cmax and AUC0–∞ for the 90% confidence interval were 0.492 and 0.320 (p > 0.05), respectively. A comparison between the test product and the reference product showed no significant difference. Both products showed bioequivalence after being administered in pigs.

Pharmacokinetics of florfenicol in turkey plasma, lung tissue, and pulmonary epithelial lining fluid after single oral bolus or continuous administration in the drinking water

Florfenicol (FF) is registered for treatment of bovine and swine respiratory diseases. Although, turkeys often suffer from bacterial respiratory tract infections, there is no registered formulation based on FF for poultry available in Europe. The aim of this study was to evaluate the pharmacokinetic behavior of FF in turkeys in plasma, lung tissue, and pulmonary epithelial lining fluid (PELF).The concentration and pharmacokinetic characteristics of FF in plasma, lung tissue, and PELF in turkeys were determined, either after a single oral bolus (30mg/kg body weight, BW) or during and after continuous drinking water medication (30mg/kg BW/d for 5 d). Plasma, lung tissue, and PELF samples were collected at different intervals after administration, and FF was quantified by liquid chromatography-tandem mass spectrometry. After single bolus administration, FF was rapidly absorbed in plasma (the time to maximum concentration, tmax, was 1.02h) and distributed to the respiratory tract (mean tmax = 1.00h). The mean t1/2el in plasma and lung tissue was similar, around 6h, whereas it was slightly higher in PELF, namely, 8.7hours. After oral bolus dosing, the mean maximum concentration in plasma was twice as high as in the lung tissue, 4.26μg/mL and 2.64μg/g, respectively, while in PELF it was much lower, 0.39μg/mL. During continuous drinking water medication, lung FF concentrations were slightly higher than plasma concentrations, with lung/plasma ratios of 2.01 and 1.27 after 24h and 72h, respectively. FF was not detected in PELF during continuous drinking water medication.

Chlortetracycline and florfenicol induce expression of genes associated with pathogenicity in multidrug-resistant Salmonella enterica serovar Typhimurium

BackgroundMultidrug-resistant (MDR) Salmonella enterica serovar Typhimurium (S. Typhimurium) is a serious public health threat as infections caused by these strains are more difficult and expensive to treat. Livestock serve as a reservoir for MDR Salmonella, and the antibiotics chlortetracycline and florfenicol are frequently administrated to food-producing animals to treat and prevent various diseases. Therefore, we evaluated the response of MDR S. Typhimurium after exposure to these two antibiotics.ResultsWe exposed four MDR S. Typhimurium isolates to sub-inhibitory concentrations of chlortetracycline (16 and 32 µg/ml) or florfenicol (16 µg/ml) for 30 min during early-log phase. Differentially expressed genes following antibiotic treatment were identified using RNA-seq, and genes associated with attachment and those located within the Salmonella pathogenicity islands were significantly up-regulated following exposure to either antibiotic. The effect of antibiotic exposure on cellular invasion and motility was also assessed. Swimming and swarming motility were decreased due to antibiotic exposure. However, we observed chlortetracycline enhanced cellular invasion in two strains and florfenicol enhanced invasion in a third isolate.ConclusionsChlortetracycline and florfenicol exposure during early-log growth altered the expression of nearly half of the genes in the S. Typhimurium genome, including a large number of genes associated with virulence and pathogenesis; this transcriptional alteration was not due to the SOS response. The results suggest that exposure to either of these two antibiotics may lead to the expression of virulence genes that are typically only transcribed in vivo, as well as only during late-log or stationary phase in vitro.

Derivative Spectrophotometric Determination of Florfenicol in Chicken Samples

A simple, rapid, and reliable derivative spectrophotometric method for determination of florfenicol was developed. Florfenicol belongs to amphenicol group antibiotics, the most widespread antibiotics used in poultry. Antibiotic residues in edible tissues of food-producing animals contribute to several reasons, such as a withdrawal period, overdose and long acting drugs. The analysis of the derivative spectra was done through the determination of the derivative values, using one of the four graphical methods, which included peak–to-baseline (peak height), peak-to- peak, and area under peak. Under the optimum experimental conditions for the first derivative spectrophotometric method, a good proportionality was found between florfenicol concentration and peak amplitude at 218.6 and 233.8 nm, over the concentration range of 1.0-53 μg/ml, 0.5-53 μg/ml, intervals of 211.2-224 nm and 224-249.2 nm, over the concentration range 0.7-53 μg/ml and 0.3-53 μg/ml, with detection limit of 0.7, 0.3, 0.1 μg/ml. The proposed method was applied for the determination of florfenicol in chicken tissues, thigh and arms, liver and kidney with recovery percentage of 95.81-114%.

PK-PD Integration Modeling and Cutoff Value of Florfenicol against Streptococcus suis in Pigs.

The aims of the present study were to establish optimal doses and provide an alternate COPD for florfenicol against Streptococcus suis based on pharmacokinetic-pharmacodynamic integration modeling. The recommended dose (30 mg/kg b.w.) were administered in healthy pigs through intramuscular and intravenous routes for pharmacokinetic studies. The main pharmacokinetic parameters of Cmax, AUC0-24h, AUC, Ke, t1/2ke, MRT, Tmax, and Clb, were estimated as 4.44 μg/ml, 88.85 μg⋅h/ml, 158.56 μg⋅h/ml, 0.048 h-1, 14.46 h, 26.11 h, 4 h and 0.185 L/h⋅kg, respectively. The bioavailability of florfenicol was calculated to be 99.14% after I.M administration. A total of 124 Streptococcus suis from most cities of China were isolated to determine the minimum inhibitory concentration (MIC) of florfenicol. The MIC50 and MIC90 were calculated as 1 and 2 μg/ml. A serotype 2 Streptococcus suis (WH-2), with MIC value similar to MIC90, was selected as a representative for an in vitro and ex vivo pharmacodynamics study. The MIC values of WH-2 in TSB and plasma were 2 μg/ml, and the MBC/MIC ratios were 2 in TSB and plasma. The MPC was detected to be 3.2 μg/ml. According to inhibitory sigmoid Emax model, plasma AUC0-24h/MIC values of florfenicol versus Streptococcus suis were 37.89, 44.02, and 46.42 h for the bactericidal, bacteriostatic, and elimination activity, respectively. Monte Carlo simulations the optimal doses for bactericidal, bacteriostatic, and elimination effects were calculated as 16.5, 19.17, and 20.14 mg/kg b.w. for 50% target attainment rates (TAR), and 21.55, 25.02, and 26.85 mg/kg b.w. for 90% TAR, respectively. The PK-PD cutoff value (COPD) analyzed from MCS for florfenicol against Streptococcus suis was 1 μg/ml which could provide a sensitivity cutoff value. These results contributed an optimized alternative to clinical veterinary medicine and showed that the dose of 25.02 mg/kg florfenicol for 24 h could have a bactericidal action against Streptococcus suis after I.M administration. However, it should be validated in clinical practice in the future investigations.

The Effects of Montmorillonite on Metabolism of Florfenicol in Pelteobagrus fulvidraco

To study the effects of montmorillonite on the metabolism and tissue elimination of florfenicol in Pelteobagrus fulvidrac, a total of 4 drug administration groups were set, namely the fluorfenicol group, the florfenicol + low-dose montmorillonite group, the florfenicol + medium-dose montmorillonite group and the florfenicol + high-dose montmorillonite group. Pelteobagrus fulvidrac was orally administered, with the plasma, muscle, liver and kidney of Pelteobagrus fulvidrac collected for detection of drug concentration using high performance liquid chromatography at 0.083 (only kidney), 0.5, 3, 4, 5, 6, 7, 9, 15, 24, 48, 72 and 96 hours, respectively. The results showed that comparing the florfenicol group, the peak plasma concentration of florfenicol in the plasma, muscle and kidney was increased in comparison with those of the other groups, while the concentration in the liver was decreased. The time to peak concentration in the plasma, muscle and liver was delayed. Montmorillonite can affect the metabolism of florfenicol in Pelteobagrus fulvidrac in sustained release and transportation manners.

Tilmicosin- and florfenicol-loaded hydrogenated castor oil-solid lipid nanoparticles to pigs: Combined antibacterial activities and pharmacokinetics.

The combined antibacterial effects of tilmicosin (TIL) and florfenicol (FF) against Actinobacillus pleuropneumoniae (APP) (n=2), Streptococcus suis (S.suis) (n=2), and Haemophilus parasuis (HPS) (n=2) were evaluated by chekerboard test and time-kill assays. The pharmacokinetics (PKs) of TIL- and FF-loaded hydrogenated castor oil (HCO)-solid lipid nanoparticles (SLN) were performed in healthy pigs. The results indicated that TIL and FF showed synergistic or additive antibacterial activities against APP, S.suis and HPS with the fractional inhibitory concentration (FIC) ranging from 0.375 to 0.75. The time-kill assays showed that 1/2 minimum inhibitory concentration (MIC) TIL combined with 1/2 MIC FF had a stronger ability to inhibit the growth of APP, S.suis, and HPS than 1 MIC TIL or 1 MIC FF, respectively. After oral administration, plasma TIL and FF concentrations could maintain about 0.1μg/ml for 192 and 176hr. The SLN prolonged the last time point with detectable concentrations (Tlast ), area under the concentration-time curve (AUC0-t ), elimination half-life (T½ke ), and mean residence time (MRT) by 3.1, 5.6, 12.7, 3.4-fold of the active pharmaceutical ingredient (API) of TIL and 11.8, 16.5, 18.1, 12.1-fold of the API of FF, respectively. This study suggests that the TIL-FF-SLN could be a useful oral formulation for the treatment of APP, S.suis, and HPS infection in pigs.

Development of a high-performance liquid chromatography method for the determination of florfenicol in animal feedstuffs.

An effective thin layer chromatography (TLC) purification procedure coupled to high-performance liquid chromatography (HPLC) method was developed for the determination of florfenicol (FF) in pig, chicken and fish feedstuffs. The feedstuff samples were extracted with ethyl acetate, defatted with n-hexane saturated with acetonitrile, and further purified by TLC. The chromatographic separation was performed on a Waters Symmetry C18 column using an isocratic procedure with acetonitrile-water (35:65, v/v) at 0.6mL/min. The ultraviolet (UV) detector was set at a wavelength of 225nm. The FF concentrations in feedstuff samples were quantified using a standard curve. Good linear correlations (y=159075x-15054, r>0.9999) were achieved within the concentration range of 0.05-200μg/mL. The recoveries of FF spiked at levels of 1, 100 and 1000μg/g ranged from 80.6% to 105.3% with the intra-day and inter-day relative standard deviation (RSD) less than 9.3%. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.02 and 0.06mg/kg for pig feedstuffs, 0.02 and 0.07mg/kg for chicken feedstuffs, and 0.02 and 0.05mg/kg for fish feedstuffs, respectively. This reliable, simple and cost-effective method could be applied to the routine monitoring of FF in animal feedstuffs.

Diffusion-limited PBPK model for predicting pulmonary pharmacokinetics of florfenicol in pig.

For most bacterial lung infections, the concentration of unbound antimicrobial agent in lung interstitial fluid has been thought to be responsible for antimicrobial efficacy. In this study, a diffusion-limited physiologically based pharmacokinetic (PBPK) model was developed to predict the pulmonary pharmacokinetics of florfenicol (FF) in pigs. The model included separate compartments corresponding to blood, diffusion-limited lung, flow-limited muscle, liver, and kidney and an extra compartment representing the remaining carcass. The absorption rate constant and renal and hepatic clearance of FF were determined in vivo. Other parameters were taken from the literature or optimized based on existing pharmacokinetic data. All mathematical operations during the development of the model were performed using acslXtreme version 3.0.2.1 (Aegis Technologies Group, Inc., Huntsville, AL, USA). The model accurately predicted the concentration-time courses of FF in lung interstitial fluid, serum, and plasma following different dosing schedules, except at the dose of 15mg/kg. When compared with the tissue residue data, the model generally underestimated the FF concentration at the injection site, whereas it gave good predictions of FF concentrations in lung, liver, and kidney at early time points. The model predictions provide a scientific basis for the dosage regimen design of FF.

Application of low-frequency sonophoresis and reduction of antibiotics in the aquatic systems.

A major concern in aquaculture is the use of chemical therapeutics, such as antibiotics, because of their impact on the environment as well as on the fish product. As a potential tool for reducing antibiotic use, we tested the application of low-frequency ultrasound as a method for enhancing antibiotic uptake. Rainbow trout juveniles (Oncorhynchus mykiss) were exposed to two different concentrations of oxytetracycline (OTC), flumequine (FLU) and florfenicol (FLO), administered by bath after the application of ultrasound. After exposure, concentrations of these substances were measured in the liver and blood of treated fish. Results showed that the ultrasound treatment can significantly increase the uptake for all three antibiotics. The uptake of OTC for example, in fish exposed to an OTC concentration of 20mgL-1 after prior treatment with ultrasound, was similar to the OTC concentrations in their liver and blood to fish exposed to 100mgL-1 without sonication. For FLU and FLO, the use of ultrasound caused significant differences of uptake in the liver at high antibiotic concentrations. This suggests that the use of ultrasound as a technique to deliver antibiotics to fish can ultimately reduce the amount of antibiotics discharged into the aquatic environment.

Effect of florfenicol on performance and microbial community of a sequencing batch biofilm reactor treating mariculture wastewater

ABSTRACTThe effects of florfenicol (FF) on the performance, microbial activity and microbial community of a sequencing batch biofilm reactor (SBBR) were evaluated in treating mariculture wastewater. The chemical oxygen demand (COD) and nitrogen removal were inhibited at high FF concentrations. The specific oxygen utilization rate (SOUR), specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR) and specific nitrate reduction rate (SNRR) were decreased with an increase in the FF concentration from 0 to 35 mg/L. The chemical compositions of loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS) could be affected with an increase in the FF concentration. The high-throughput sequencing indicated some obvious variations in the microbial community at different FF concentrations. The relative abundance of Nitrosomonas and Nitrospira showed a decreasing tendency with an increase in the FF concentration, suggesting that FF could affect the nitrification process of SBBR. Some genera capable of reducing nitrate to nitrogen gas could be inhibited by the addition of FF in the influent, such as Azospirillum and Hyphomicrobium.