Microcalorimetric Study of the Action of Yb^3＋ ion on the Growth of Staphylococcus aureus

A microcalorimetric method was used to evaluate the action of Yb^3 ions onthe growth metabolism of Staphylococcus aureus.The power-time curves of the growth metabolism of Staphylo.coccus aureus and the action of Yb^3 ions were obtained by us-ing stopped-flow method at 37 ℃. For evaluation of the action,the growth rate constants ( k1 and k2) for the log phase 1, log phase 2, and the total heat effect (Qtotal) for Staphylococcus aureus were determined. The results show that Yb^3 ions at low concentrations have the stimnlatory effect on Staphylococcus au-reus and that Yb^3 ions at higher concentration could inhibit its growth.     

Synthesis,characterization, and antibacterial activity of 6-Chloro-8-methyl-2-oxo-2H-chromene-3-carboxylic acid ethyl ester

The title compound was synthesized by reacting 2-hydroxy-4-methoxy-benzaldehyde with diethyl malonate in the presence of piperidine catalyst and ethanol as solvent. The chemical structure of the title compound was elucidated by elemental analysis, ¹H-NMR, and IR. The crystal structure was determined by X-ray diffraction data. It crystallizes in monoclinic crystal system, P2₁/c space group with unit cell parameters, a = 12.840(2) Å, b = 24.790(4) Å, c = 7.8544(13) Å, β = 98.035(5)°, V = 2475.5(7) ų, and Z = 8. The molecular and crystal structure of the title compound is stabilized by inter- and intramolecular interactions of the type C—H···O. The newly synthesized compound was screened for its antibacterial activity against two gram-positive and two gram-negative bacteria.     

Highly Stable,Amide‐Bridged Autoinducing Peptide Analogues that Strongly Inhibit the AgrC Quorum Sensing Receptor in Staphylococcus aureus

Blocking quorum sensing (QS) pathways has attracted considerable interest as an approach to suppress virulence in bacterial pathogens. Toward this goal, we recently developed analogues of a native autoinducing peptide (AIP‐III) signal that can inhibit AgrC‐type QS receptors and attenuate virulence phenotypes in Staphylococcus aureus. Application of these compounds is limited, however, as they contain hydrolytically unstable thioester linkages and have only low aqueous solubilities. Herein, we report amide‐linked AIP analogues with greatly enhanced hydrolytic stabilities and solubilities relative to our prior analogues, whilst maintaining strong potencies as AgrC receptor inhibitors in S. aureus. These compounds represent powerful tools for the study of QS.     

Sub-inhibitory stress with essential oil affects enterotoxins production and essential oil susceptibility in Staphylococcus aureus

Fourteen wild strains of Staphylococcus aureus positive for gene sea were tested for enterotoxins production and the minimum inhibitory concentration of Leptospermum scoparium, Origanum majorana, Origanum vulgare, Satureja montana and Thymus vulgaris essential oils (EOs) were determined. After this trial, bacteria stressed with sub-inhibitory concentration of each EO were tested for enterotoxins production by an immunoenzymatic assay and resistance to the same EO. Oregano oil exhibited the highest antibacterial activity followed by manuka and thyme oils. After the exposure to a sub-inhibitory concentration of EOs, strains displayed an increased sensitivity in more than 95% of the cases. After treatment with oregano and marjoram EOs, few strains showed a modified enterotoxins production, while 43% of the strains were no longer able to produce enterotoxins after treatment with manuka EO. The results obtained in this study highlight that exposure to sub-inhibitory concentration of EO modifies strains enterotoxins production and EOs susceptibility profile.     

Effect of metal complex formation on the antibacterial activity of nitazoxanide: Spectroscopic and density functional theory calculations

In the present work, experimental and theoretical structural studies of two new nitazoxanide (NTZ) complexes, [Co(NTZ)(NO₃)₂(OH₂)] ( 1 ) and [Ni(NTZ)(CH₃COO)(OH₂)]·CH₃COO ( 2 ) were reported. The susceptibility of Staphylococcus aureus and Escherichia coli towards NTZ and its complexes was assessed. NTZ behaves as a monodentate ligand via the thiazole N atom forming distorted octahedral and tetrahedral complexes with Co(II) and Ni(II) ions, respectively. The d‐d transitions were assigned by the aid of time‐dependent density functional theory calculations. The magnetic susceptibility value of 1 remains unchanged in the temperature range of 298–77K, while that of 2 decreases linearly with the temperature to attain 2.79 μ_B at 77K. Coordination of NTZ (0.084 μmol ml^?1) to Co(II) ( 1 ) (0.028 μmol ml^?1) and Ni(II) ions ( 2 ) (0.079 μmol ml^?1) leads to an improvement in the toxicity against S. aureus.     

鹅葡萄球菌病研究进展

葡萄球菌病的流行和分布遍及全世界,在我国,鹅感染葡萄球菌病而大量发病和死亡的报道越来越多,并严重威胁着养鹅业的发展.除鹅以外,很多禽类都可以感染发病.鹅葡萄球菌病是由致病性金黄色葡萄球菌引起的一种传染病,不同日龄的鹅均可感染,但临床上多见于幼鹅.本病一年四季都可发生,临床症状有急性败血型和关节炎型、脐炎型等.本文介绍鹅葡萄球菌病的流行病学、临床症状、诊断方法及防治措施.     

Some Novel Oxadiazolyl/Azetidinyl Benzimidazole Derivatives: Synthesis and in Vitro Biological Evaluation

In a wide search program for new and efficient antimicrobial agents, a series of oxadiazole/azetidinone-incorporated benzimidazoles have been synthesized and evaluated against different Gram-positive and Gram-negative bacteria. Derivatives having long alkyl chain on the oxadiazole/azetidinone moiety with three or more carbon atoms have shown less antibacterial activity.     

乳品中金黄色葡萄球菌肠毒素B免疫传感检测方法的研究

本文利用自制的金黄色葡萄球菌肠毒素B(SEB)抗体构建了一种L-半胱氨酸和纳米金的双层自组装免疫传感器,采用循环伏安法及交流阻抗法对传感器进行表征与测定,并对各项相关条件进行优化,最终建立了SEB检测的标准曲线,线性范围分别在2～10 ng/mL和10～100 ng/mL,相关系数分别为0.9939和0.9926,检出限(S/N=3)为0.667 ng/mL,乳品检测回收率在84.3%～93.2%之间。该传感器特异性良好,稳定性好,可再生使用,可应用于乳品中SEB的快速检测。     

磁弹性无线传感器检测不同液体介质中的金黄色葡萄球菌

研制了磁弹性金黄色葡萄球菌无线传感器,用于检测不同液体介质中的金黄色葡萄球菌。取0.2mL一定浓度菌液加到含2mL无菌液体介质的检测玻璃管中,磁弹性传感器共振频率随细菌的生长而改变。通过改变牛肉膏和蛋白胨的浓度,得出传感器在含有2×105cells/mL金黄色葡萄球菌的培养基CM2-2中共振频率响应最大。结果表明,此传感器可以测定的金黄色葡萄球菌浓度范围在CM2-2中是3×103～2×107cells/mL,在牛奶中是1×104～2×107cells/mL,检出限分别是1×103cells/mL和1×104cells/mL。传感器共振频移大小与金黄色葡萄球菌的浓度呈线性相关关系,相关系数在牛奶中是0.98,在培养基中是0.99。