A physiologically based pharmacokinetic model to optimize the dosage regimen and withdrawal time of cefquinome in pigs.

Cefquinome is widely used to treat respiratory tract diseases of swine. While extra-label dosages of cefquinome could improve clinical efficacy, they might lead to excessively high residues in animal-derived food. In this study, a physiologically based pharmacokinetic (PBPK) model was calibrated based on the published data and a microdialysis experiment to assess the dosage efficiency and food safety. For the microdialysis experiment, in vitro/in vivo relative recovery and concentration-time curves of cefquinome in the lung interstitium were investigated. This PBPK model is available to predict the drug concentrations in the muscle, kidney, liver, plasma, and lung interstitial fluid. Concentration-time curves of 1000 virtual animals in different tissues were simulated by applying sensitivity and Monte Carlo analyses. By integrating pharmacokinetic/pharmacodynamic target parameters, cefquinome delivered at 3-5 mg/kg twice daily is advised for the effective control of respiratory tract infections of nursery pig, which the bodyweight is around 25 kg. Based on the predicted cefquinome concentrations in edible tissues, the withdrawal interval is 2 and 3 days for label and the extra-label doses, respectively. This study provides a useful tool to optimize the dosage regimen of cefquinome against respiratory tract infections and predicts the concentration of cefquinome residues in edible tissues. This information would be helpful to improve the food safety and guide rational drug usage.

Ceftiofur in swine manure contributes to reducing pathogens and antibiotic resistance genes during composting.

Aerobic composting is a common way for the disposal of feces produced in animal husbandry, and can reduce the release of antibiotic resistance genes (ARGs) from feces into the environment. In this study, we collected samples from two distinct treatments of swine manure compost with and without ceftiofur (CEF), and identified the ARGs, mobile genetic elements (MGEs), and bacterial community by metagenomic sequencing. The impacts of CEF on the bacterial community composition and fate of ARGs and MGEs were investigated. With increasing composting temperature and pH, the concentration of CEF in the manure decreased rapidly, with a degradation half-life of 1.12 d and a 100% removal rate after 10 d of aerobic composting. Metagenomics demonstrated that CEF in the manure might inhibit the growth of Firmicutes and Proteobacteria, thereby reducing some ARGs and MGEs hosted by these two bacteria, which was further confirmed by the variations of ARGs and MGEs. A further redundancy analysis suggested that pH and temperature are key environmental factors affecting ARG removal during composting, and intI1 and bacterial communities also have significant influence on ARG abundance. These results are of great significance for promoting the removal of some ARGs from animal manure by controlling some key environmental factors and the type of antibiotics used in animals.

Optimization and Validation of Dosage Regimen for Ceftiofur against Pasteurella multocida in Swine by Physiological Based Pharmacokinetic-Pharmacodynamic Model.

Model informed drug development is a valuable tool for drug development and clinical application due to its ability to integrate variability and uncertainty of data. This study aimed to determine an optimal dosage of ceftiofur against P. multocida by ex vivo pharmacokinetic/pharmacodynamic (PK/PD) model and validate the dosage regimens by Physiological based Pharmacokinetic-Pharmacodynamic (PBPK/PD) model. The pharmacokinetic profiles of ceftiofur both in plasma and bronchoalveolar lavage fluid (BALF) are determined. PD performance of ceftiofur against P. multocida was investigated. By establishing PK/PD model, PK/PD parameters and doses were determined. PBPK model and PBPK/PD model were developed to validate the dosage efficacy. The PK/PD parameters, AUC0-24 h/MIC, for bacteriostatic action, bactericidal action and elimination were determined as 44.02, 89.40, and 119.90 h and the corresponding dosages were determined as 0.22, 0.46, and 0.64 mg/kg, respectively. AUC24 h/MIC and AUC 72 h/MIC are simulated by PBPK model, compared with the PK/PD parameters, the therapeutic effect can reach probability of target attainment (PTA) of 90%. The time-courses of bacterial growth were predicted by the PBPK/PD model, which indicated the dosage of 0.46 mg/kg body weight could inhibit the bacterial growth and perform good bactericidal effect.

The adsorption-desorption characteristics and degradation kinetics of ceftiofur in different agricultural soils.

Cephalosporins are one of the most widely used antibiotics. When cephalosporins are discharged into the environment, they not only induce the production of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARBs) but also cause toxic effects on animals and plants. Due to their complicated environmental behavior and lack of relevant data, the environmental behavior remains unclear. In this study, the adsorption-desorption and degradation characteristics of the third-generation cephalosporin drug ceftiofur (CEF) were investigated in three agricultural soils (sandy loam, loam and clay). According to the relevant parameters of the Freundlich adsorption isotherm (the Kf range was 57.63-122.44 µg1-1/n L1/n kg-1), CEF was adsorbed moderately in the soils and had the potential to migrate into groundwater. CEF exhibited low persistence in the soils and faster degradation than other antibiotics, such as tetracyclines and fluoroquinolones. The degradation half-lives (DT50) of CEF in soils ranged from 0.76 days to 4.31 days. Adding feces, increasing the water content, providing light and increasing the temperature significantly accelerated the degradation of CEF in soils. The DT50 values of CEF in soils were significantly prolonged when the soils were sterilized, indicating that both physical degradation and biodegradation played important roles in the degradation of CEF in soils. The DT50 values of CEF in soils were significantly prolonged at high concentrations, indicating that the degradability of CEF in soils was affected by the initial concentration. No significant differences were observed in the DT50 values for the different soil types (p > 0.05). This study provides useful information about the environmental behavior of CEF and improves the environmental risk assessment of CEF.

Adsorption/desorption and degradation of doxycycline in three agricultural soils.

Veterinary antibiotics are widely used in animal agriculture. Owing to its good absorption in the gastrointestinal tract, strong tissue permeability, and long biological half-life, doxycycline (DOX) is widely used to treat bacterial infections; however, this use can pose an environmental risk. The adsorption/desorption and degradation of DOX in three agricultural soils were investigated. DOX rapidly adsorbed to the soils, with an adsorption equilibrium time of 12 h for the three soils. The Freundlich equation was used to fit the adsorption and desorption of DOX in soils. A high Freundlich affinity coefficient (KF) was obtained from Freundlich isotherms, indicating strong sorption of DOX to agricultural soils and weak mobility to aquatic environment. Soil organic matter, the clay ratio and the cation exchange capacity were significantly positively correlated with KF (P < 0.05). The half-life (DT50) of DOX degradation in the soils ranged from 2.51 to 25.52 d. Soil microorganisms, soil moisture, temperature, the initial concentration, illumination and soil texture all significantly affected the degradation of DOX in soil (P < 0.05). When 8% (w/w) manure was added, DOX degradation was significantly accelerated (P < 0.05). Biotic and abiotic factors affected the degradation of DOX in soils. These results indicated that soil properties and environmental conditions greatly affected the fate and transport of DOX into agricultural soils.

Application of physiologically based pharmacokinetic models to promote the development of veterinary drugs with high efficacy and safety.

Physiologically based pharmacokinetic (PBPK) models have become important tools for the development of novel human drugs. Food-producing animals and pets comprise an important part of human life, and the development of veterinary drugs (VDs) has greatly impacted human health. Owing to increased affordability of and demand for drug development, VD manufacturing companies should have more PBPK models required to reduce drug production costs. So far, little attention has been paid on applying PBPK models for the development of VDs. This review begins with the development processes of VDs; then summarizes case studies of PBPK models in human or VD development; and analyzes the application, potential, and advantages of PBPK in VD development, including candidate screening, formulation optimization, food effects, target-species safety, and dosing optimization. Then, the challenges of applying the PBPK model to VD development are discussed. Finally, future opportunities of PBPK models in designing dosing regimens for intracellular pathogenic infections and for efficient oral absorption of VDs are further forecasted. This review will be relevant to readers who are interested in using a PBPK model to develop new VDs.

Single and ternary competitive adsorption-desorption and degradation of amphenicol antibiotics in three agricultural soils.

The widespread usage of veterinary antibiotics results in antibiotic contamination and increases environmental risks. This study was evaluated the single and ternary competitive adsorption-desorption and degradation of three amphenicol antibiotics (AMs): chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in three agricultural soils. The adsorption capacity of amphenicol antibiotics in the soil was weak, and the Kf value was in the range of 0.15-3.59 µg1-1/nL1/n kg-1. In the single adsorption-desorption experiment, the ranked order of adsorption capacity was TAP > FF > CAP. However, in the ternary competitive adsorption experiment, the order was changed to be CAP > FF > TAP. The degradation of AMs in soils was performed at various conditions. All AMs were vulnerable to microbial degradation in soils. A higher initial concentration would reduce the degradation rate and enhance the persistence of AMs in soil. The degradation of AMs was positively influenced by changes in soil moisture content and culture temperatures up to 30 °C and decreased at higher temperatures. An equation was used to predict the leachability of AMs in soils and assess their risk to the water environment. The weak adsorption capacity and poor persistence of FF indicated that it may have a strong effect on groundwater based on the equation. It is imperative to further assess the biological impacts of FF at environmentally relevant concentrations given its mobility and extensive use in the livestock industry.

Clinical efficacy of celecoxib for osteoarthritis and bone anchor assisted knee extensor reconstruction.

Celecoxib is the most recent non steroidal anti-inflammatory analgesic, and has been gradually used in the treatment of acute pain, rheumatism and osteoarthritis. This paper analyzes the analgesic effect of celecoxib in the treatment of knee osteoarthritis and put forward a new mechanism of knee joint extensor reconstruction assisted by bone anchor. The experimental group was given celecoxib 200 mg/ time and 1 time /d. The results showed that VAS (Visual Analogue Scale) decreased gradually in both groups on the 1st, 3rd and 7th day of treatment and VAS in experimental group was lower than that in control group at the same time point (P<0.05). At the 1 year follow-up, experience group had a significant improvement on the Lysholm (69.33 ± 8.38 preoperatively and 88.65 ± 12.93 postoperatively) and Kujula (69.33 ± 8.38 preoperatively and 88.65 ±12.93 postoperatively) knee scores (P<0.05). The results showed that celecoxib had a good analgesic effect in patients with knee osteoarthritis and reducing the release of inflammatory factors may be its mechanism..

Metagenomic analysis reveals impact of acyl homoserine endolipid-like signaling molecules on the aqueous sediment resistome under florfenicol stress.

Quorum sensing potentially helps microorganisms adapt to antibiotic stress encountered in the environment. This experiment investigated the effect of acyl homoserine endolipid-like signaling molecules on microbial antibiotic resistance gene structures in aqueous sediments under florfenicol stress. Additional acyl homoserine endolipid-like signaling molecules (AHLs) alter the structure of multidrug resistance genes in florfenicol-stressed sediments, particularly the multidrug resistance efflux pump gene family. Prophages and integrative and conjugative elements (ICEs) determined the resistance genes structure, and pathways related to mobile genetic elements (MGEs) transfer may play an essential role in this process. The practical application of AHLs to regulate quorum sensing systems may alter bacterial stress responses to environmental florfenicol residues, thereby reducing the development of antibiotic resistance in the environment.

Co-selection mechanism for bacterial resistance to major chemical pollutants in the environment.

Bacterial resistance is an emerging global public health problem, posing a significant threat to animal and human health. Chemical pollutants present in the environment exert selective pressure on bacteria, which acquire resistance through co-resistance, cross-resistance, co-regulation, and biofilm resistance. Resistance genes are horizontally transmitted in the environment through four mechanisms including conjugation transfer, bacterial transformation, bacteriophage transduction, and membrane vesicle transport, and even enter human bodies through the food chain, endangering human health. Although the co-selection effects of bacterial resistance to chemical pollutants has attracted widespread attention, the co-screening mechanism and co-transmission mechanisms remain unclear. Therefore, this article summarises the current research status of the co-selection effects and mechanism of environmental pollutants resistance, emphasising the necessity of studying the co-selection mechanism of bacteria against major chemical pollutants, and lays a solid theoretical foundation for conducting risk assessment of bacterial resistance.

Biodegradation strategies of veterinary medicines in the environment: Enzymatic degradation.

One Health closely integrates healthy farming, human medicine, and environmental ecology. Due to the ecotoxicity and risk of transmission of drug resistance, veterinary medicines (VMs) are regarded as emerging environmental pollutants. To reduce or mitigate the environmental risk of VMs, developing friendly, safe, and effective removal technologies is an important means of environmental remediation for VMs. Many previous studies have proved that biodegradation has significant advantages in removing VMs, and biodegradation based on enzyme catalysis presents higher operability and specificity. This review focused on biodegradation strategies of environmental pollutants and reviewed the enzymatic degradation of VMs including antimicrobial drugs, insecticides, and disinfectants. We reviewed the sources and catalytic mechanisms of peroxidase, laccase, and organophosphorus hydrolases, and summarized the latest research status of immobilization methods and bioengineering techniques in improving the performance of degrading enzymes. The mechanism of enzymatic degradation for VMs was elucidated in the current research. Suggestions and prospects for researching and developing enzymatic degradation of VMs were also put forward. This review will offer new ideas for the biodegradation of VMs and have a guide significance for the risk mitigation and detoxification of VMs in the environment.

Interpretation of vaginal metagenomic characteristics in different types of vaginitis.

Although vaginitis is closely related to vaginal microecology in females, the precise composition and functional potential of different types of vaginitis remain unclear. Here, metagenomic sequencing was applied to analyze the vaginal flora in patients with various forms of vaginitis, including cases with a clue cell proportion ranging from 1% to 20% (Clue1_20), bacterial vaginitis (BV), vulvovaginal candidiasis (VVC), and BV combined with VVC (VVC_BV). Our results identified Prevotella as an important biomarker between BV and Clue1_20. Moreover, a gradual decrease was observed in the relative abundance of shikimic acid metabolism associated with bacteria producing indole as well as a decline in the abundance of Gardnerella vaginalis in patients with BV, Clue1_20, and healthy women. Interestingly, the vaginal flora of patients in the VVC_BV group exhibited structural similarities to that of the VVC group, and its potentially functional characteristics resembled those of the BV and VVC groups. Finally, Lactobacillus crispatus was found in high abundance in healthy samples, greatly contributing to the stability of the vaginal environment. For the further study of L. crispatus, we isolated five strains of L. crispatus from healthy samples and evaluated their capacity to inhibit G. vaginalis biofilms and produce lactic acid in vitro to select the potential probiotic candidate for improving vaginitis in future clinical studies. Overall, we successfully identified bacterial biomarkers of different vaginitis and characterized the dynamic shifts in vaginal flora between patients with BV and healthy females. This research advances our understanding and holds great promise in enhancing clinical approaches for the treatment of vaginitis. IMPORTANCE: Vaginitis is one of the most common gynecological diseases, mostly caused by infections of pathogens such as Candida albicans and Gardnerella vaginalis. In recent years, it has been found that the stability of the vaginal flora plays an important role in vaginitis. Furthermore, the abundant Lactobacillus-producing rich lactic acid in the vagina provides a healthy acidic environment such as Lactobacillus crispatus. The metabolites of Lactobacillus can inhibit the colonization of pathogens. Here, we collected the vaginal samples of patients with bacterial vaginitis (BV), vulvovaginal candidiasis (VVC), and BV combined with VVC to discover the differences and relationships among the different kinds of vaginitis by metagenomic sequencing. Furthermore, because of the importance of L. crispatus in promoting vaginal health, we isolated multiple strains from vaginal samples of healthy females and chose the most promising strain with potential probiotic benefits to provide clinical implications for treatment strategies.

Salmonella antimicrobials inherited and the non-inherited resistance: mechanisms and alternative therapeutic strategies.

Salmonella spp. is one of the most important foodborne pathogens. Typhoid fever and enteritis caused by Salmonella enterica are associated with 16-33 million infections and 500,000 to 600,000 deaths annually worldwide. The eradication of Salmonella is becoming increasingly difficult because of its remarkable capacity to counter antimicrobial agents. In addition to the intrinsic and acquired resistance of Salmonella, increasing studies indicated that its non-inherited resistance, which commonly mentioned as biofilms and persister cells, plays a critical role in refractory infections and resistance evolution. These remind the urgent demand for new therapeutic strategies against Salmonella. This review starts with escape mechanisms of Salmonella against antimicrobial agents, with particular emphasis on the roles of the non-inherited resistance in antibiotic failure and resistance evolution. Then, drug design or therapeutic strategies that show impressive effects in overcoming Salmonella resistance and tolerance are summarized completely, such as overcoming the barrier of outer membrane by targeting MlaABC system, reducing persister cells by limiting hydrogen sulfide, and applying probiotics or predatory bacteria. Meanwhile, according to the clinical practice, the advantages and disadvantages of above strategies are discussed. Finally, we further analyze how to deal with this tricky problems, thus can promote above novel strategies to be applied in the clinic as soon as possible. We believed that this review will be helpful in understanding the relationships between tolerance phenotype and resistance of Salmonella as well as the efficient control of antibiotic resistance.

Migration and toxicity of toltrazuril and its main metabolites in the environment.

Veterinary drugs heavily used in livestock are passed into the environment through different ways, resulting in risks to terrestrial environments and humans. The migration of toltrazuril (TOL), an important anticoccidial drug used intensively in livestock, and its main metabolites between the chicken manure compost, soil and vegetables was investigated, and then the impacts of TOL on the soil bacterial community and ARGs, soil enzyme activities and phytotoxicity were detected. In the process of aerobic composting for 80 days, except for toltrazuril sulfoxide (the degradation half-life was 59.74 d), TOL and ponazuril (PON) were not significantly degraded. However, TOL and its metabolites were significantly degraded in fertilized soil, and the degradation half-life was 28.17-346.50 d. Among the three drugs, only PON could migrate from soil to vegetables, and the residual concentrations of PON in lettuce and radish were 2.64-70.02 µg kg-1 and 0-2.80 µg kg-1, respectively. Moreover, TOL and its main metabolisms had no significant effect on the bacterial community structure and the abundance of antibiotic resistance genes during composting, but affected the microbial activity in the soil. The presence of TOL and its main metabolites reduced soil urease activity, increased catalase activity, and decreased alkaline phosphatase activity at the beginning and then increased slightly. They had negative effects on plant growth. Compared with the control group, the inhibition rates of TOL and its metabolites on lettuce and radish seed germination were 8.33% and 26.74% respectively, and the inhibition rates of root elongation length were 25.88% and 34.45% respectively. These results showed that TOL and its main metabolites were ineffectively removed by aerobic composting, and could be migrated from composting to soil and vegetables, which had adverse effects on soil enzyme activity and plant growth. Therefore, its environmental ecological risk and human health risk needs to be further evaluated.

Fate and exposure risk of florfenicol, thiamphenicol and antibiotic resistance genes during composting of swine manure.

Livestock manure is an important source of antibiotic resistance genes (ARGs) spreading to the environment, posing a potential threat to human health. Here, we investigated the dissipation of florfenicol (FF) and thiamphenicol (TAP), and their effects on the bacterial community, mobile genetic elements (MGEs), and ARGs during composting. The results indicated that FF and TAP dissipated rapidly in compost, with half-life values of 5.1 and 1.6 d, respectively. However, FF could not be completely removed during composting. The FF and TAP residues in manure could reduce the elimination of ARGs and MGEs during composting, and had a negative effect on the physicochemical factors of the compost. Significant correlations were found between floR and intI1, indicating that floR in manure may more easily diffuse to the soil environment. Meanwhile, the presence of FF in manure could increase the abundance of floR. Network analysis showed that Proteobacteria and Firmicutes were the dominant bacterial communities and important potential pathogen hosts carrying ARGs. The predicted environmental concentration of FF in the soil was over 100 µg kg-1, which indicates that FF poses a potential risk to the natural environment, and we verified this result through field experiments. The results showed that FF dissipated in the soil after it migrated from manure to soil. In contrast, TAP in manure posed lower environmental risk. This study highlights that changed in composting conditions may control the rate of removal of ARGs. Further studies are needed to investigate the best environmental conditions to achieve a faster degradation of FF and a more comprehensive elimination of ARGs during composting.

Effects of composting on the fate of doxycycline, microbial community, and antibiotic resistance genes in swine manure and broiler manure.

Aerobic composting is an economical and effective technology that is widely used to treat animal manure. To study the fate of doxycycline (DOX), the microbial community, and antibiotic resistance genes (ARGs) during composting, aerobic composting of broiler manure and swine manure was carried out under natural environmental conditions. Aerobic composting effectively removed DOX (with a removal rate > 97%) and most ARGs from animal manure. The microbial diversity and the numbers of ARGs were higher in composted swine manure compared with composted broiler manure. The microbial community structure changed during composting, and the dominant phyla of broiler manure and swine manure changed from Firmicutes to Bacteroidetes and Proteobacteria, respectively. DOX changed the structure and relative abundance of the microbial community during composting, and the relative abundance of multidrug resistance genes and mobile genetic elements (MGEs) increased, which might lead to the risk of transmission of resistance in the environment. The C / N ratio, DOX concentration, Firmicutes, intl1, and intl2 were the key factors driving the change in ARGs during composting. These results help to reveal the effects of DOX on microbial communities, ARGs, and MGEs during composting and clarify the possible ways to reduce the risk of resistance gene transmission in the environment.

Application of Semi-Mechanistic Pharmacokinetic and Pharmacodynamic Model in Antimicrobial Resistance.

Antimicrobial resistance is a major public health issue. The pharmacokinetic/pharmacodynamic (PK/PD) model is an essential tool to optimize dosage regimens and alleviate the emergence of resistance. The semi-mechanistic PK/PD model is a mathematical quantitative tool to capture the relationship between dose, exposure, and response, in terms of the mechanism. Understanding the different resistant mechanisms of bacteria to various antibacterials and presenting this as mathematical equations, the semi-mechanistic PK/PD model can capture and simulate the progress of bacterial growth and the variation in susceptibility. In this review, we outline the bacterial growth model and antibacterial effect model, including different resistant mechanisms, such as persisting resistance, adaptive resistance, and pre-existing resistance, of antibacterials against bacteria. The application of the semi-mechanistic PK/PD model, such as the determination of PK/PD breakpoints, combination therapy, and dosage optimization, are also summarized. Additionally, it is important to integrate the PD effect, such as the inoculum effect and host response, in order to develop a comprehensive mechanism model. In conclusion, with the semi-mechanistic PK/PD model, the dosage regimen can be reasonably determined, which can suppress bacterial growth and resistance development.

Application of a Physiologically Based Pharmacokinetic Model to Develop a Veterinary Amorphous Enrofloxacin Solid Dispersion.

Zoonotic intestinal pathogens threaten human health and cause huge economic losses in farming. Enrofloxacin (ENR) shows high antibacterial activity against common intestinal bacteria. However, its poor palatability and low aqueous solubility limit the clinical application of ENR. To obtain an ENR oral preparation with good palatability and high solubility, a granule containing an amorphous ENR solid dispersion (ENR-SD) was prepared. Meanwhile, a PBPK model of ENR in pigs was built based on the physiological parameters of pigs and the chemical-specific parameters of ENR to simulate the pharmacokinetics (PK) of ENR-SD granules in the intestinal contents. According to the results of parameter sensitivity analysis (PSA) and the predicted PK parameters at different doses of the model, formulation strategies and potential dose regimens against common intestinal infections were provided. The DSC and XRD results showed that no specific interactions existed between the excipients and ENR during the compatibility tests, and ENR presented as an amorphous form in ENR-SD. Based on the similar PK performance of ENR-SD granules and the commercial ENR soluble powder suggesting continued enhancement of the solubility of ENR, a higher drug concentration in intestinal contents could not be obtained. Therefore, a 1:5 ratio of ENR and stearic acid possessing a saturated aqueous solubility of 1190 ± 7.71 µg/mL was selected. The predictive AUC24h/MIC90 ratios against Campylobacter jejuni, Salmonella, and Escherichia coli were 133, 266 and 8520 (>100), respectively, suggesting that satisfactory efficacy against common intestinal infections would be achieved at a dose of 10 mg/kg b.w. once daily. The PSA results indicated that the intestinal absorption rate constant (Ka) was negatively correlated with the Cmax of ENR in the intestine, suggesting that we could obtain higher intestinal Cmax using P-gp inducers to reduce Ka, thus obtaining a higher Cmax. Our studies suggested that the PBPK model is an excellent tool for formulation and dose design.

Apply a Physiologically Based Pharmacokinetic Model to Promote the Development of Enrofloxacin Granules: Predict Withdrawal Interval and Toxicity Dose.

Enrofloxacin (ENR) granules were developed to prevent and control the infections caused by foodborne zoonotic intestinal pathogens in our previous studies. To promote the further development of ENR granules and standardize their usage in pigs, a physiologically based pharmacokinetic (PBPK) model of the ENR granule in pigs was built to determine the withdrawal time (WT) and evaluate the toxicity to pigs. Meanwhile, the population WT was determined by a Monte Carlo analysis to guarantee pork safety. The fitting results of the model showed that the tissue residual concentrations of ENR, ciprofloxacin, and ENR plus ciprofloxacin were all well predicted by the built PBPK model (R2 > 0.82). When comparing with the EMA's WT1.4 software method, the final WT (6 d) of the ENR granules in the population of pigs was well predicted. Moreover, by combining the cytotoxicity concentration (225.9 µg/mL) of ENR against pig hepatocytes, the orally safe dosage range (≤130 mg/kg b.w.) of the ENR granules to pigs was calculated based on the validated PBPK model. The well-predicted WTs and a few uses in animals proved that the PBPK model is a potential tool for promoting the judicious use of antimicrobial agents and evaluating the toxicity of the veterinary antimicrobial products.

Characterization, antioxidativity, and anti-carcinoma activity of exopolysaccharide extract from Rhodotorula mucilaginosa CICC 33013.

The water-soluble exopolysaccharide REPS2-A was isolated and characterized from R. mucilaginosa CICC 33013. REPS2-A was composed of galactose, arabinose, glucose, and mannose at a molar ratio of 63.1:0.2:18.3:18.3, respectively, with a molecular weight of 7.125×106Da. Based on FT-IR, NMR, and methylation analysis, REPS2-A was identified to be a highly branched polysaccharide with a backbone of (1→3)-linkedGal with Man, Gal, and Ara terminals. The branches were identified as (1→2)-linked Glc, (1→4)-linked Man, (1→3)-linked Glc, (1→4,6)-linked Man, and (1→2,3,4)-linked Ara. In addition, REPS2-A exhibited excellent free radical scavenging (DPPH, ABTS, and reducing power) and antitumor activities. These results indicate its activity against growth of the human hepatocarcinoma cell HepG2 with IC50 values of 1.0mg/mL, compared to lower cytotoxic effects on normal human hepatocyte cell L02. Studying the underlying mechanisms indicated that REPS2-A induced both dose- and time-dependent cell cycle arrest at the G1/S phase.