In vitro and in vivo metabolite profiling of valnemulin using ultraperformance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry

Antimicrobial resistance characteristics and phylogenetic relationships of pleuromutilin-resistant Enterococcus isolates from different environmental samples along a laying hen production chain

Antimicrobial resistance in the laying hen production industry has become a serious public health problem. The antimicrobial resistance and phylogenetic relationships of the common conditional pathogen Enterococcus along the laying hen production chain have not been systematically clarified. 105 Enterococcus isolates were obtained from 115 environmental samples (air, dust, feces, flies, sewage, and soil) collected along the laying hen production chain (breeding chicken, chick, young chicken, and commercial laying hen). These Enterococcus isolates exhibited resistance to some clinically relevant antibiotics, such as tetracycline (92.4%), streptomycin (92.4%), and erythromycin (91.4%), and all strains had multidrug resistance phenotypes. Whole genome sequencing characterized 29 acquired antibiotic resistance genes (ARGs) that conferred resistance to 11 classes of antibiotics in 51 pleuromutilin-resistant Enterococcus isolates, and lsa(E), which mediates resistance to pleuromutilins, always co-occurred with lnu(B). Alignments with the Mobile Genetic Elements database identified four transposons (Tn554, Tn558, Tn6261, and Tn6674) with several ARGs (erm(A), ant(9)-la, fex(A), and optrA) that mediated resistance to many clinically important antibiotics. Moreover, we identified two new transposons that carried ARGs in the Tn554 family designated as Tn7508 and Tn7492. A complementary approach based on conventional multi-locus sequence typing and whole genome single nucleotide polymorphism analysis showed that phylogenetically related pleuromutilin-resistant Enterococcus isolates were widely distributed in various environments on different production farms. Our results indicate that environmental contamination by antimicrobial-resistant Enterococcus requires greater attention, and they highlight the risk of pleuromutilin-resistant Enterococcus and ARGs disseminating along the laying hen production chain, thereby warranting effective disinfection.

UPLC-MS/MS Method for Simultaneous Determination of Valnemulin and Its Metabolites in Crucian Carp: In Vivo Metabolism and Tissue Distribution Analyses

Valnemulin (VML) is a semi-synthetic pleuromutilin derivative widely used to treat animal bacterial diseases. However, no study has comprehensively evaluated VML metabolism in aquatic animals, including crucian carp. This study aimed to investigate VML metabolism in crucian carp. VML metabolites in crucian carp were quantified via intraperitoneal injection and analyzed via ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Three VML metabolites were detected in crucian carp via ultra-performance liquid chromatography-tandem quadrupole and time-of-flight mass spectrometry (UPLC-Q-TOF/MS) structural analysis. The enrichment and metabolism rules of the metabolites were summarized based on tissue distribution and concentration changes of the three metabolites. The metabolites were mainly found in the liver at 0.1 h after VML injection. The levels of the metabolites were abundant in the bile from 4 h to 12 h and in the skin after 72 h. The levels of the metabolites in the bile first increased, then decreased. The metabolism in the liver was completed at 72 h. The metabolites were detected in the skin following a 72 h period, which increased with time.

Metabolic profiling of bisphenol A diglycidyl ether in vitro and in vivo

Bisphenol A diglycidyl ethers (BADGE) is one class of human-made chemicals, and it is one of the most widely used raw materials for epoxy resins. As an active compound, BADGE undergoes biotransformation in vitro and in vivo. However, there is a limited understanding of the biotransformation of BADGE and toxicity studies on transformation products. We conducted comprehensive research on the metabolic transformation of BADGE in vitro and in vivo. The results showed that 12 metabolites and 7 metabolites were identified in vitro and in vivo, respectively. Four biotransformation products, including M1 (hydrolysis), M3 (dehydroxylation), M10 (carboxylation), and M11 (glucose conjugation), can be found in both in vitro and in vivo samples. The main metabolic pathways were hydroxylation, carboxylation, cysteine (Cys) conjugation, and glucose conjugation. Besides, our results suggested the existence of metabolic differences in BADGE between species and gender. Further, we investigated toxicities of BADGE metabolites in-silico. Importantly, some hydrolysis (M1, M2), hydroxylation (M7), and oxidation (M8) products showed similar or even higher potential toxicity than BADGE depending on the endpoint. These results enrich the biotransformation profiles of BADGE and provide useful information for understanding its biotransformation in humans and a reference for the comprehensive assessment for human health risk.

Background ions into exclusion list: A new strategy to enhance the efficiency of DDA data collection for high-throughput screening of chemical contaminations in food

Foods contaminated with hazardous compounds, could pose potential risks for human health. To date, there is still a big challenge in accurate identification. In this study, a novel data-dependent acquisition (DDA) approach, based on a combination of inclusion list and exclusion list, was proposed to acquire more effective MS/MS spectra. This strategy was successfully applied in a large-scale screening survey to detect 50 mycotoxins in oats, 155 veterinary drugs in dairy milk, and 200 pesticides in tomatoes. Compared with traditional acquisition modes, this new strategy has higher detection rate, particularly at ultra-low concentration by eliminating background influence, thereby generating the MS/MS spectra for more potential hazardous materials instead of matrix interference. Additionally, the obtained MS/MS spectra are simpler and more likely to be traced back than DIA. Moreover, this new strategy would be more comprehensively applied in food safety monitoring with the improvement of HRMS and post-acquisition techniques.

A highly sensitive monoclonal antibody-based paper sensor for simultaneously detecting valnemulin and tiamulin in porcine liver

Valnemulin (VAL) and tiamulin (TIA) are pleuromutilin antibiotics used primarily for treating bacterial infections in swine or other food animals. Furthermore, VAL and TIA are also employed as feed additives to promote animal growth. However, the illegal use of VAL and TIA could cause a series of hazards to consumers. Here, VAL was designed to be conjugated with bovine serum protein to prepare immunogen. A highly sensitive monoclonal antibody that recognized both VAL and TIA has been successfully produced. Moreover, an immunochromatographic strip assay for rapidly screening VAL and TIA in porcine liver was established with visual detection limits (cutoff values) of 50 and 25 ng/g, respectively. The IC₅₀ values calculated from the equation of the standard curve were 6.06 and 3.45 ng/g and the limits of detection were 0.96 and 0.29 ng/g for VAL and TIA. According to the recovery experiment results, the test strip exhibited acceptable accuracy and precision. Generally, the proposed strip provided a practical tool for the detection of VAL and TIA. PRACTICAL APPLICATION: We produced a highly sensitive monoclonal antibody and developed an immunoassay strip for simultaneously monitoring TIA and VAL. Additionally it was preliminarily confirmed that the rapid detection tool was suitable for screening TIA and VAL in porcine liver.

Boron-Pleuromutilins as Anti- Wolbachia Agents with Potential for Treatment of Onchocerciasis and Lymphatic Filariasis

A series of pleuromutilins modified by introduction of a boron-containing heterocycle on C(14) of the polycyclic core are described. These analogs were found to be potent anti- Wolbachia antibiotics and, as such, may be useful in the treatment of filarial infections caused by Onchocerca volvulus, resulting in Onchocerciasis or river blindness, or Wuchereria bancrofti and Brugia malayi and related parasitic nematodes resulting in lymphatic filariasis. These two important neglected tropical diseases disproportionately impact patients in the developing world. The lead preclinical candidate compound containing 7-fluoro-6-oxybenzoxaborole (15, AN11251) was shown to have good in vitro anti- Wolbachia activity and physicochemical and pharmacokinetic properties providing high exposure in plasma. The lead was effective in reducing the Wolbachia load in filarial worms following oral administration to mice.

Unraveling the Metabolic Routes of Retapamulin: Insights into Drug Development of Pleuromutilins

Retapamulin, a semisynthetic pleuromutilin derivative, is exclusively used for the topical short-term medication of impetigo and staphylococcal infections. In the present study, we report that retapamulin is adequately and rapidly metabolized in vitro via various metabolic pathways, such as hydroxylation, including mono-, di-, and trihydroxylation, and demethylation. Like tiamulin and valnemulin, the major metabolic routes of retapamulin were hydroxylation at the 2β and 8α positions of the mutilin moiety. Moreover, in vivo metabolism concurred with the results of the in vitro assays. Additionally, we observed significant interspecies differences in the metabolism of retapamulin. Until now, modifying the side chain was the mainstream method for new drug discovery of the pleuromutilins. This approach, however, could not resolve the low bioavailability and short efficacy of the drugs. Considering the rapid metabolism of the pleuromutilins mediated by cytochrome P450 enzymes, we propose that blocking the active metabolic site (C-2 and C-8 motif) or administering the drug in combination with cytochrome P450 enzyme inhibitors is a promising pathway in the development of novel pleuromutilin drugs with slow metabolism and long efficacy.

Development of Indirect Competitive Enzyme-Linked Immunosorbent and Immunochromatographic Strip Assays for Tiamulin Detection in Chicken

Tiamulin (TML) is a diterpenoid antibiotic used in animals. In this study, a gold nanoparticle immunochromatographic strip assay and an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) were developed to detect the residue of TML in chicken. TML aminobutyric was synthesized and conjugated to keyhole limpet hemocyanin by mixed anhydride method as immunogen, whereas TML was connected to ovalbumin with 1,1'-carbonyldiimidazole as coating antigen. Under optimized conditions, the ultrasensitive monoclonal antibody-based ic-ELISA exhibited a half-maximal inhibitory concentration (IC₅₀) value of 0.36 ng/mL with a working range of 0.14-0.9 ng/mL for TML. A rapid and sensitive immunochromatographic strip assay was developed with a TML cutoff value of 2.5 ng/mL. On the basis of these results, both developed methods are useful for TML detection in chicken.

Metabolic Profile of Zearalenone in Liver Microsomes from Different Species and Its in Vivo Metabolism in Rats and Chickens Using Ultra High-Pressure Liquid Chromatography-Quadrupole/Time-of-Flight Mass Spectrometry

To explore differences of zearalenone (ZEN) metabolism between various species, phase I and II metabolism by liver microsomes of animals and human were investigated using ultra high-pressure liquid chromatography-quadrupole/time-of-flight mass spectrometry (UHPLC-Q/TOF MS). A total of 24 metabolites were identified, among which 12 were reported for the first time. Reduction, hydroxylation, and glucuronidation were the major metabolic pathways of ZEN, and significant differences in various species were also observed. Reduction was the main reaction in swine and human, whereas hydroxylation was predominant in rats, chickens, goats, and cows in in vitro systems. Furthemore, in vivo metabolism of ZEN in rats and chickens was investigated, and 23 and 6 metabolites were identified in each species, respectively. Reduction, hydroxylation, and glucuronidation were the major metabolic pathways in rats, while reduction and sulfation predominated in chickens. These results further enrich the biotransformation profile of ZEN, providing a helpful reference for assessing the risks to animals and humans.

Metabolic profile of the masked mycotoxin T-2 toxin-3-glucoside in rats (in vitro and in vivo) and humans (in vitro)

The metabolic profile of T-2 toxin-3-glucoside (T2-Glc) in humans and rats was investigated using ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF). When rat and human liver microsomes were incubated with T2-Glc, a total of five metabolites were detected. T2-Glc exposed a higher metabolic stability in rats and human than T-2 toxin (T-2). The metabolism of T2-Glc by the intestinal microbiota of human and rats was also investigated, and three metabolites were observed. T2-Glc was reconverted to T-2 during incubation with fresh faeces. Furthermore, in vivo metabolism of T2-Glc in rats after oral administration was carried out, and three metabolites were detected in rat urine and faeces (T-2, HT-2 toxin and 3'-OH-T2-Glc). In vivo metabolism results indicated that T2-Glc was mainly metabolised in the gastro-intestinal tract with a low absorption level in rats. The results demonstrated that hydroxylation (C-3' and C-4'), hydrolysis (C-4 and C-8) and deconjugation are the main metabolic pathways of T2-Glc in mammals.

Metabolism of T-2 Toxin in Farm Animals and Human In Vitro and in Chickens In Vivo Using Ultra High-Performance Liquid Chromatography- Quadrupole/Time-of-Flight Hybrid Mass Spectrometry Along with Online Hydrogen/Deuterium Exchange Technique

After being incubated with animal and human liver microsomes, metabolites of phase I and II were investigated. A comparison was performed by ultrahigh performance liquid chromatography-quadrupole/time-of-flight coupled to mass spectrometry (UHPLC-Q/TOF). Consequently, a total of four phase I metabolites and three glucuronide binding metabolites of T-2 toxin were discovered. Although a significant metabolic difference was observed among six species, HT-2 toxin was the major product in all species. In addition, the in vivo metabolism of T-2 toxin after oral administration was also investigated in chickens, In total, 18 metabolites were detected, of which 13 were novel, to our knowledge, and reported for the first time. To elucidate the structures of these metabolites, besides accurate mass data from their MS and MS² spectra, online hydrogen/deuterium (H/D) exchange technique was also carried out. These new metabolites were regarded as 3'-hydroxy-T-2 3-sulfate, 3'-hydroxy-HT-2 3-sulfate, 4'-hydroxy-HT-2, 3',4'-dihydroxy-HT-2, 4'-carboxyl-T-2, 4'-carboxyl-HT-2, 4'-carboxyl-4'-hydroxy-T-2, and their isomers, implying that T-2 toxin was metabolized more extensively in animals than previously thought. Furthermore, 3'-hydroxy-HT-2, 4'-carboxyl-T-2, 3'-hydroxy-T-2, HT-2 toxin, and neosolaniol were identified to be the major metabolites of T-2 toxin in chickens. The present study expands existing knowledge about T-2 toxin metabolism, informing assessments of the impact T-2 toxin exposure and metabolism on health.

A New Combination of a Pleuromutilin Derivative and Doxycycline for Treatment of Multidrug-Resistant Acinetobacter baumannii

Multidrug-resistant (MDR) Acinetobacter baumannii is one of the most difficult Gram-negative bacteria to treat and eradicate. In a cell-based screening of pleuromutilin derivatives against a drug sensitive A. baumannii strain, new molecules (2-4) exhibit bacteriostatic activity with 3.13 μg/mL concentration and 1 shows bactericidal activity with an MBC of 6.25 μg/mL. The pleuromutilin derivative 1 displays strong synergistic effects with doxycycline in a wide range of concentrations. A 35/1 ratio of 1 and doxycycline (1-Dox 35/1) kills drug susceptible A. baumannii with the MBC of 2.0 μg/mL and an MDR A. baumannii with the MBC of 3.13 μg/mL. In vitro anti-Acinetobacter activity of 1-Dox 35/1 is superior to that of clinical drugs such as tobramycin, tigecycline, and colistin. The efficacy of 1-Dox 35/1 is evaluated in a mouse septicemia model; treatment of the infected C57BL/6 mice with 1-Dox 35/1 protects from lethal infection of A. baumannii with an ED50 value of <2.0 mg/kg.

Exploring the Role of CYP3A4 Mediated Drug Metabolism in the Pharmacological Modulation of Nitric Oxide Production

Nitric-oxide synthase, the enzyme responsible for mammalian nitric oxide generation, and cytochrome P450, the major enzymes involved in drug metabolism, share striking similarities. Therefore, it makes sense that cytochrome P450 drug mediated biotransformations might play an important role in the pharmacological modulation of nitric oxide synthase. In this work, we have undertaken an integrated in vitro assessment of the hepatic metabolism and nitric oxide modulation of previously described dual inhibitors (imidazoles and macrolides) of these enzymes in order assess the implication of CYP450 activities over production of nitric oxide. In vitro systems based in human liver microsomes and activated mouse macrophages were developed for these purposes. Additionally in vitro production the hepatic metabolites of dual inhibitor, roxithromycin, was investigated achieving the identification and isolation of main hepatic biotransformation products. Our results suggested that for some macrolide compounds, the cytochrome P450 3A4 derived drug metabolites have an important effect on nitric oxide production and might critically contribute to the pharmacological immunomodulatory activity observed.

Pharmacokinetics of valnemulin after intravenous, intramuscular, and oral administration in layer chickens

The pharmacokinetic characteristics of valnemulin in layer chickens were studied after single intravenous, intramuscular, and oral administration at a dose of 15 mg/kg body weight. Plasma samples at certain time points were collected and the drug concentrations in them by ultra high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS). The concentration-time data for each individual were plotted by noncompartmental analysis for the whole three routes. Following intravenous administration, the plasma concentration showed tiny fluctuation. The elimination half-life (T1/2λz), total body clearance (Cl), and area under the plasma concentration-time curve (AUC) were 1.85 ± 0.43 h, 2.2 ± 0.9 L/h, and 7.52 ± 2.46 μg·h/mL, respectively. Following intramuscular administration, the peak concentration (C_max , 1.40 ± 0.43 μg/mL) was achieved at the time of 0.34 h. A multiple-peak phenomenon existed after oral administration, and the first peak and secondary peak were at 10 min and during 2-4 h, respectively, while the tertiary peak appeared during 5-15 h. The bioavailability (F %) for intramuscular and oral administration was 68.60% and 52.64%, respectively. In present study, the detailed pharmacokinetic profiles showed that this drug is widely distributed and rapidly eliminated, however has a low bioavailability, indicating that valnemulin is likely to be a favorable choice in the clinical practice.

Comprehensive Analysis of Tiamulin Metabolites in Various Species of Farm Animals Using Ultra-High-Performance Liquid Chromatography Coupled to Quadrupole/Time-of-Flight

Tiamulin is an antimicrobial widely used in veterinary practice to treat dysentery and pneumonia in pigs and poultry. However, knowledge about the metabolism of tiamulin is very limited in farm animals. To better understand the biotransformation of tiamulin, in the present study, in vitro and in vivo metabolites of tiamulin in rats, chickens, swine, goats, and cows were identified and elucidated using ultra-high performance liquid chromatography coupled to quadrupole/time-of-flight. As a result, a total of 26 metabolites of tiamulin, identified in vitro and in vivo, and majority of metabolites were revealed for the first time. In all farm animals, tiamulin undergoes phase I metabolic routes of hydroxylation in the mutilin part (the ring system), S-oxidation and N-deethylation on side chain, and no phase II metabolite was detected. Among these, 2β- and 8α-hydroxylation and N-deethylation were the main metabolic pathways of tiamulin in farm animals. In addition, we have put forward that 8a-hydroxy-tiamulin and 8a-hydroxy-N-deethyl-tiamulin could be hydroxylated into 8a-hydroxy-mutilin, the marker residue of tiamulin in swine. Furthermore, a significant interspecies difference was observed on the metabolism of tiamulin among various farm animals. The possible marker residues for tiamulin in swine were 8α-hydroxy-tiamulin, N-deethyl-tiamulin, and 8α-hydroxy-N-deethyl-tiamulin, which were consistent with the hypothesis proposed by the European Agency for the Evaluation of Medicinal Products. However, results in present study indicated that three metabolites (2β-hydroxy-tiamulin, N-deethyl-tiamulin, and 2β-hydroxy-N-deethyl-tiamulin) of tiamulin in chickens had larger yields, which implied that 2β-hydroxy-mutilin or N-deethyl-tiamulin was more likely to be regarded as the potential marker residue of tiamulin in chickens.

Identification of Echinacoside Metabolites Produced by Human Intestinal Bacteria Using Ultraperformance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry

Echinacoside (ECH) is one of the representative phenylethanoid glycosides. It is widely present in plants and exhibits various bioactivities. However, the extremely low oral bioavailability of ECH in rats implies that ECH may go through multiple hydrolysis steps in the gastrointestinal tract prior to its absorption into the blood. Therefore, the gastrointestinal metabolites of ECH are more likely to be the bioactive components. This study established an approach combining ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) with MS(E) technology and MetaboLynx software for rapid analysis of the ECH metabolic profile produced by human intestinal bacteria. As a result, 13 ECH metabolites and 5 possible metabolic pathways (including deglycosylation, dehydroxylation, reduction, hydroxylation, and acetylation) were identified. Furthermore, hydroxytyrosol (HT) and 3-hydroxyphenylpropionic acid (3-HPP) were found to be the two bioactive metabolites of ECH produced by human intestinal bacteria.

Comparative metabolism of Lappaconitine in rat and human liver microsomes and in vivo of rat using ultra high-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry

Lappaconitine (LAP), a non-addictive potent analgesic drug, is broadly used to treat cancer and postoperative pain in many countries, and it also has antibiotic activity against Pseudomonas aeruginosa and Salmonella Typhi. Despite its widespread usage and potential for expanded use, its metabolism was poorly investigated. In this work, the metabolic fate of LAP in liver microsomes of the rat and human was compared, and after oral administration, the metabolites in the rat were investigated using ultra high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q/TOF-MS). As a result, a total of 51 metabolites were identified, including 48 metabolites that were reported here for the first time. Based on accurate MS/MS spectra and the known structure of LAP, the metabolites structures and their fragment ions were readily characterized. The biotransformations of LAP in vitro and in vivo were shown to involve hydroxylation, N-deacetylation, O-demethylation, N-deethylation, and hydrolysis. Furthermore, the results indicated a quantitative species difference in the metabolites for LAP between the rat and human. However, 16-DMLAP, DAL and 5'-OH-DAL were the main in vitro and in vivo metabolites. This work provides the LAP metabolite profiles in rat and human, which will help better understand the pharmacological and toxicological activities of LAP.

Ex vivo pharmacokinetic and pharmacodynamic analysis of valnemulin against Mycoplasma gallisepticum S6 in Mycoplasma gallisepticum and Escherichia coli co-infected chickens

Pharmacokinetic and pharmacodynamic (PK/PD) indices against Mycoplasma gallisepticum (MG) S6 were investigated in an ex vivo PK/PD model following oral administration of valnemulin to chickens co-infected with M. gallisepticum and Escherichia coli. The minimum inhibitory concentrations (MICs) for valnemulin against MG S6 in artificial medium and chicken serum were determined. In vitro time-killing curves were established according to a series of multiples of the MIC value in an artificial medium, and ex vivo time-killing curves were established in serum samples obtained from infected chickens at different time points after oral administration with an initial titer of 1 × 10(6) color change units (CCU)/mL MG S6. The sigmoid Emax model was used to provide 24 h area under concentration-time curve/minimum inhibitory concentration ratios (AUC0-24h/MIC) for mycoplasmastasis, mycoplasmacidal activity and mycoplasmal elimination, respectively. The inoculum size and micro or macro methods exhibited little effect on MIC determination of MG, whereas matrix had a large effect. The rapid killing activity observed in in vitro time-killing curves seems to indicate that valnemulin was mycoplasmacidal and concentration dependent against MG. The AUC0-24h/MIC ratio for mycoplasmacidal activity and mycoplasmal elimination was 1321 h and 1960 h, respectively. A dosage regimen of 12.4 mg/kg/day and 18.3 mg/kg/day valnemulin was calculated for mycoplasmacidal activity and mycoplasmal elimination against MG S6, respectively.