Carbapenem resistance presents a major challenge for the global public health network, as clinical infections caused by carbapenem-resistant organisms(CRO) are frequently associated with significant morbidity and mort...Carbapenem resistance presents a major challenge for the global public health network, as clinical infections caused by carbapenem-resistant organisms(CRO) are frequently associated with significant morbidity and mortality. Ceftazidime–avibactam(CAZ–AVI) is a novel cephalosporin/β-lactamase inhibitor combination offering an important advance in the treatment of CRO infections. CAZ–AVI has been reported to inhibit the activities of Ambler classes A, C, and some class D enzymes. However, bacterial resistance has been emerging shortly after the introduction of this combination in clinical use, with an increasing trend. Understanding these resistance mechanisms is crucial for guiding the development of novel treatments and aiding in the prediction of underlying resistance mechanisms. This review aims to systematically summarize the epidemiology of CAZ–AVI-resistant strains and recently identified resistance mechanisms of CAZ–AVI, with a focus on the production of β-lactamase variants, the hyperexpression of β-lactamases, reduced permeability, and overexpressed efflux pumps. The various mechanisms of CAZ–AVI resistance that have emerged within a short timescale emphasize the need to optimize the use of current agents, as well as the necessity for the surveillance of CAZ–AVI-resistant pathogens.展开更多
A 1-b-methylcarbapenem analogue 6 was synthesized on polystyrene-diethylsilane resin (PS-DES) using 2-azetidinone bearing with 2-oxazolidone chiral auxiliary as starting material.
Three new alkaloids, griffithdionc 1, griffiazanone A 2 and griffiazanone B 3 were isolated from the rhizomes of Goniothalamus griffithii Hook. F. el. Thoms. Their structures were elucidated by analysis the spectral d...Three new alkaloids, griffithdionc 1, griffiazanone A 2 and griffiazanone B 3 were isolated from the rhizomes of Goniothalamus griffithii Hook. F. el. Thoms. Their structures were elucidated by analysis the spectral data (IR, UV, MS, 1 H and 13C NMR, HMBC, NOE experiment).The absolute configuration of griffithazanone A 2 was determined by Mosher's methods.展开更多
Four different ZSM 5 zeolites are tested for the gas phase Beckmann rearrangement of cyclohexanone oxime (CHO) into lactam. B ZSM 5 derived titanosilicalite (Ti ZSM 5) exhibits catalytic performances comparabl...Four different ZSM 5 zeolites are tested for the gas phase Beckmann rearrangement of cyclohexanone oxime (CHO) into lactam. B ZSM 5 derived titanosilicalite (Ti ZSM 5) exhibits catalytic performances comparable to hydrothermally synthesized titanosilicalite (TS 1), much better than B ZSM 5 and Al ZSM 5. The effect of reaction conditions (solvent, feed space velocity, and water) on the catalytic performance of Ti ZSM 5 is studied. It is found that a quantitative relationship exists among the feed space velocity, the reaction time, and the CHO constant conversion. Ethanol or methanol as solvent shows higher activity, lactam selectivity, and stability than benzene and n hexanol. The addition of water to the rearrangement with a maximum amount of 1.0 mole per mole CHO results in the increase of CHO conversion while no meaningful changes in lactam selectivity and stability are observed.展开更多
基金supported by the National Key Research and Development Program of China (2017YFC1200200)Major Infectious Diseases such as AIDS and Viral Hepatitis Prevention and Control Technology Major Projects (2018ZX10712-001)+1 种基金National Natural Science Foundation of China (81702045 and 81902030)Shenzhen Basic Research projects (JCYJ20190807144409307)
文摘Carbapenem resistance presents a major challenge for the global public health network, as clinical infections caused by carbapenem-resistant organisms(CRO) are frequently associated with significant morbidity and mortality. Ceftazidime–avibactam(CAZ–AVI) is a novel cephalosporin/β-lactamase inhibitor combination offering an important advance in the treatment of CRO infections. CAZ–AVI has been reported to inhibit the activities of Ambler classes A, C, and some class D enzymes. However, bacterial resistance has been emerging shortly after the introduction of this combination in clinical use, with an increasing trend. Understanding these resistance mechanisms is crucial for guiding the development of novel treatments and aiding in the prediction of underlying resistance mechanisms. This review aims to systematically summarize the epidemiology of CAZ–AVI-resistant strains and recently identified resistance mechanisms of CAZ–AVI, with a focus on the production of β-lactamase variants, the hyperexpression of β-lactamases, reduced permeability, and overexpressed efflux pumps. The various mechanisms of CAZ–AVI resistance that have emerged within a short timescale emphasize the need to optimize the use of current agents, as well as the necessity for the surveillance of CAZ–AVI-resistant pathogens.
基金This work was financially supported by the National Natural Science Foundation of China (No. 29972037).
文摘A 1-b-methylcarbapenem analogue 6 was synthesized on polystyrene-diethylsilane resin (PS-DES) using 2-azetidinone bearing with 2-oxazolidone chiral auxiliary as starting material.
文摘Three new alkaloids, griffithdionc 1, griffiazanone A 2 and griffiazanone B 3 were isolated from the rhizomes of Goniothalamus griffithii Hook. F. el. Thoms. Their structures were elucidated by analysis the spectral data (IR, UV, MS, 1 H and 13C NMR, HMBC, NOE experiment).The absolute configuration of griffithazanone A 2 was determined by Mosher's methods.
基金the Foundations for Basic Research ofTsinghua U niversity and of China Petrochem icalCompany
文摘Four different ZSM 5 zeolites are tested for the gas phase Beckmann rearrangement of cyclohexanone oxime (CHO) into lactam. B ZSM 5 derived titanosilicalite (Ti ZSM 5) exhibits catalytic performances comparable to hydrothermally synthesized titanosilicalite (TS 1), much better than B ZSM 5 and Al ZSM 5. The effect of reaction conditions (solvent, feed space velocity, and water) on the catalytic performance of Ti ZSM 5 is studied. It is found that a quantitative relationship exists among the feed space velocity, the reaction time, and the CHO constant conversion. Ethanol or methanol as solvent shows higher activity, lactam selectivity, and stability than benzene and n hexanol. The addition of water to the rearrangement with a maximum amount of 1.0 mole per mole CHO results in the increase of CHO conversion while no meaningful changes in lactam selectivity and stability are observed.
