The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
W Kurzatkowski - One of the best experts on this subject based on the ideXlab platform.
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Affinity of exocellular DD-carboxypeptidase/transpeptidase from Saccharopolyspora erythraea PZH TZ-575 to beta-lactam compounds
Medycyna doswiadczalna i mikrobiologia, 1999Co-Authors: J Solecka, W KurzatkowskiAbstract:The DD-carboxypeptidase/transpeptidases (DD-peptidases) involved in bacterial cell wall metabolism, catalyse the attack of C-terminal D-alanyl-D-alanine peptide bond of the peptydoglycan precursor. These enzymes are inactivated by beta-lactam antibiotics. DD-peptidase from Saccharopolyspora erythraea PZH TZ 64-575 was purified by the use of DEAE-cellulose, Sephadex G-100, Q-Sepharose resins and FPLC (Mono Q). After each step the effluent was concentrated by Amicon ultrafiltration. The purified enzyme showed DD-carboxypeptidase specific activity of 50.9 U/mg. The enzyme exhibited high affinity to beta-lactam compounds e.g. cefamandole, Cefapirin, cefradin 1.5-2.6 x 10(-8) M. It was used to screen strains from the Culture Collection of the National Institute of Hygiene in Warsaw for the production of DD-peptidase inhibitors.
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affinity of exocellular dd carboxypeptidase transpeptidase from saccharopolyspora erythraea pzh tz 575 to beta lactam compounds
Medycyna doświadczalna i mikrobiologia, 1999Co-Authors: J Solecka, W KurzatkowskiAbstract:The DD-carboxypeptidase/transpeptidases (DD-peptidases) involved in bacterial cell wall metabolism, catalyse the attack of C-terminal D-alanyl-D-alanine peptide bond of the peptydoglycan precursor. These enzymes are inactivated by beta-lactam antibiotics. DD-peptidase from Saccharopolyspora erythraea PZH TZ 64-575 was purified by the use of DEAE-cellulose, Sephadex G-100, Q-Sepharose resins and FPLC (Mono Q). After each step the effluent was concentrated by Amicon ultrafiltration. The purified enzyme showed DD-carboxypeptidase specific activity of 50.9 U/mg. The enzyme exhibited high affinity to beta-lactam compounds e.g. cefamandole, Cefapirin, cefradin 1.5-2.6 x 10(-8) M. It was used to screen strains from the Culture Collection of the National Institute of Hygiene in Warsaw for the production of DD-peptidase inhibitors.
Xi Xia - One of the best experts on this subject based on the ideXlab platform.
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Determination of 82 veterinary drugs in swine waste lagoon sludge by ultra-high performance liquid chromatography-tandem mass spectrometry.
Journal of chromatography. A, 2017Co-Authors: Ping Guo, Yawen Shan, Yingyu Wang, Tianhe Liu, Xi XiaAbstract:This work reports the development of a multi-residue method for the identification and quantification of 82 veterinary drugs belonging to different chemical classes in swine waste lagoon. The proposed method applies a solid-phase extraction procedure with Oasis PRiME HLB cartridges that combines isolation of the compounds and sample clean-up in a single step. Analysis is performed by ultra-high performance liquid chromatography-tandem mass spectrometry, in one single injection with a chromatographic run time of only 9.5min. Linearity was studied in the range between 1 and 500μgkg-1 using standards prepared both in pure solvent and in the presence of matrix, showing coefficients of determination higher than 0.99 for all the analytes except for Cefapirin in matrix. The average recoveries were in the range of 60-110% for most of the compounds tested with inter-day relative standard deviations below 17%. More than 97% of the investigated compounds had less or equal to a 5μgkg-1 quantitation limit in the studied matrix. Finally, the method was used with success to detect and quantify veterinary drugs residues in real samples with sulfonamides, quinolones, and tetracyclines being the most frequently determined compound groups.
Ting Yang - One of the best experts on this subject based on the ideXlab platform.
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Development and validation of an ultra high performance liquid chromatography tandem mass spectrometry method for determination of 10 cephalosporins and desacetylCefapirin in milk.
Journal of chromatography. B Analytical technologies in the biomedical and life sciences, 2013Co-Authors: Xiao-lin Hou, Jian Zhao, Ting YangAbstract:A simple, sensitive and reliable analytical method was developed for the simultaneous determination of 10 cephalosporins and desacetylCefapirin in bovine milk by ultra high performance liquid chromatography-positive electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS). Samples were directly purified through HLB cartridge after dilution with 50mM phosphate buffer solution (pH 8.5). Then the eluate was dried under nitrogen and the residue was redissolved in mobile phase. Samples were analyzed by LC-MS/MS on an Acquity UPLC BEH Shield RP18 column with gradient elution. The samples were quantified using ceftiofur-D3 as internal standard. The proposed method was validated according to the European Commission Decision 2002/657/EC. The CCα values were 111, 0.04, 140, 55, 55, 67, 23, 23, 68, 0.10 and 113μg/kg for cefalexin, cefradine, cefacetrile, cefazolin, cefoperazone, Cefapirin, cefalonium, cefquinome, desacetylCefapirin, cefotaxime and ceftiofur, respectively. The mean recoveries, repeatability (expressed as coefficient of variation, CVr), and reproducibility (CVR) varied from 94.6% to 117.1%, from 5.6% to 13.6% (CVr), and from 5.9% to 27.9% (CVR), respectively. The method is demonstrated to be suitable for the determination of 10 cephalosporins and desacetylCefapirin in bovine milk. The total time required for the analysis of one sample, including sample preparation, was about 40min.
Reinhard Neubert - One of the best experts on this subject based on the ideXlab platform.
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Intestinal Transport of β-Lactam Antibiotics: Analysis of the Affinity at the H+/Peptide Symporter (PEPT1), the Uptake into Caco-2 Cell Monolayers and the Transepithelial Flux
Pharmaceutical Research, 1999Co-Authors: Beate Bretschneider, Matthias Brandsch, Reinhard NeubertAbstract:Purpose . This study on the intestinal transport of β-lactam antibiotics was undertaken to investigate the correlation between cellular transport parameters and the bioavailability. Methods . Transport of 23 β-lactam antibiotics was characterized by measuring their ability to inhibit the uptake of glycylsarcosine into Caco-2 cells, their uptake into the cells and their total flux across the cell monolayers. Results . Ceftibuten and cyclacillin were recognized by PEPT1 with affinity constants comparable to those of natural dipeptides (K_i = 0.3 and 0.5 mM, respectively). Cefadroxil, cefamandole, cephradine, cefaclor, cefuroxime-axetil, cefixime, cephalotin, cephalexin and ampicillin also interacted with PEPT1 (K_i = 7-14 mM). In contrast, Cefapirin, cefodizime, cefuroxime, cefmetazole, ceftazidime, benzyl-penicillin, ceftriaxone, cefpirome, cefotaxime, cefepime, cephaloridine and cefsulodin displayed no affinity to the transport system (K_i > 20 mM). The uptake into the cells and the transepithelial flux was highest for those β-lactam antibiotics, which showed the strongest inhibition of [^14C]Gly-Sar transport (p < 0.0001). Exceptions were cefuroxim-axetil and cephalotin. Conclusions . The probability of oral bioavailability for β-lactam antibiotics is mainly determined by their affinity to PEPT1. A threshold K_i value of 14 mM with respect to Gly-Sar uptake is required.
Evelyne Meyer - One of the best experts on this subject based on the ideXlab platform.
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The intramammary efficacy of first generation cephalosporins against Staphylococcus aureus mastitis in mice.
Veterinary microbiology, 2012Co-Authors: Dieter Demon, Carolin Ludwig, Koen Breyne, David Guédé, Julia-charlotte Dörner, Robrecht Froyman, Evelyne MeyerAbstract:Staphylococcus aureus-induced mastitis in cattle causes important financial losses in the dairy industry due to lower yield and bad milk quality. Although S. aureus is susceptible to many antimicrobials in vitro, treatment often fails to cure the infected udder. Hence, comprehensive evaluation of antimicrobials against S. aureus mastitis is desirable to direct treatment strategies. The mouse mastitis model is an elegant tool to evaluate antimicrobials in vivo while circumventing the high costs associated with bovine experiments. An evaluation of the antimicrobial efficacy of the intramammary (imam) applied first generation cephalosporins cefalexin, cefalonium, Cefapirin and cefazolin, was performed using the S. aureus mouse mastitis model. In vivo determination of the effective dose 2log(10) (ED(2log10)), ED(4log10), protective dose 50 (PD(50)) and PD(100) in mouse mastitis studies, support that in vitro MIC data of the cephalosporins did not fully concur with the in vivo clinical outcome. Cefazolin was shown to be the most efficacious first generation cephalosporin to treat S. aureus mastitis whereas the MIC data indicate that cefalonium and Cefapirin were more active in vitro. Changing the excipient for imam application from mineral oil to miglyol 812 further improved the antimicrobial efficacy of cefazolin, confirming that the excipient can influence the in vivo efficacy. Additionally, statistical analysis of the variation of S. aureus-infected, excipient-treated mice from fourteen studies emphasizes the strength of the mouse mastitis model as a fast, cost-effective and highly reproducible screening tool to assess the efficacy of antimicrobial compounds against intramammary S. aureus infection.