Staphylococcus aureus is one of the main pathogenic agents responsible for nosocomial and community-acquired bacterial infections. The pathogenicity of this Gram-positive bacterium is ensured by its different adhesion...Staphylococcus aureus is one of the main pathogenic agents responsible for nosocomial and community-acquired bacterial infections. The pathogenicity of this Gram-positive bacterium is ensured by its different adhesion factors. Collagen and the extracellular glycoprotein adhesin are among the Staphylococcus most important virulence factors. It has been shown that most of the S. aureus strains carry the ica operon, responsible for biofilm production. However, the coexpression of the icaA and the icaD genes is necessary for complete biofilm synthesis. The aim of our study was to study a collection of 15 clinical strains of S. aureus from different sources for the presence of can and icaD genes coding intercellular adhesion proteins. We also intended to estimate the strains’ ability to form biofilms by the red Cong method and to test the adhesion ability of S. aureus to the ciliated protist Tetrahymena pyriformis, which we used as a novel cellular adhesion model. Finally, we checked the adhesion’s inhibition capacity of some plants extracts. The molecular detection of adhesion genes revealed that 80% of strains are cna positive, and 73% are icaD positive. Qualitative biofilm production of S. aureus revealed that 66.6% of strains were slime producers. The adhesion test revealed that 20% of strains are strongly adhering to T. pyriformis and that the Clematis cirrhosa extract has an anti-adhering effect of S. aureus to the ciliate T. pyriformis.展开更多
Selective oxidation of Fe-Mn alloys was characterizied through X-ray photoelectron spectroscopy and scanning/transmission electron microscopy during industrial continuous annealing(in an atmosphere of N_(2)-5 vol.%H_(...Selective oxidation of Fe-Mn alloys was characterizied through X-ray photoelectron spectroscopy and scanning/transmission electron microscopy during industrial continuous annealing(in an atmosphere of N_(2)-5 vol.%H_(2) with traces of water at 800℃).After annealing,only MnO oxides are formed on and below the surface and few iron oxides appear on the top surface due to oxidation of ambient air or the formation of FeO-MnO solid solutions.Mn concentration profiles exhibit typical selective oxidation and show similar features.Mn concentration first increases to a peak value at a depth of 5-10 nm from surface,and then decreases to the minimum at the oxidation front,following with a floating up and down to bulk composition.According to XPS spectra and Mn concentration profiles as a function of depth,the annealed alloy surfaces can be divided into four zones:ambient air contaminated zone,MnO enrichment zone(external and internal oxidation coexisting here),Mn depletion zone and bulk composition zone.Mn concentration reaches a minimum value at the oxidation front,whose position is deeper with annealing temperature and time increasing.The value of Mn diffusion coefficient in ferrite estimated using diffusion flux at the oxidation front is 2.9×10^(-15)m^(2)s^(-1) at 800℃,which is slightly greater than that in literature.展开更多
文摘Staphylococcus aureus is one of the main pathogenic agents responsible for nosocomial and community-acquired bacterial infections. The pathogenicity of this Gram-positive bacterium is ensured by its different adhesion factors. Collagen and the extracellular glycoprotein adhesin are among the Staphylococcus most important virulence factors. It has been shown that most of the S. aureus strains carry the ica operon, responsible for biofilm production. However, the coexpression of the icaA and the icaD genes is necessary for complete biofilm synthesis. The aim of our study was to study a collection of 15 clinical strains of S. aureus from different sources for the presence of can and icaD genes coding intercellular adhesion proteins. We also intended to estimate the strains’ ability to form biofilms by the red Cong method and to test the adhesion ability of S. aureus to the ciliated protist Tetrahymena pyriformis, which we used as a novel cellular adhesion model. Finally, we checked the adhesion’s inhibition capacity of some plants extracts. The molecular detection of adhesion genes revealed that 80% of strains are cna positive, and 73% are icaD positive. Qualitative biofilm production of S. aureus revealed that 66.6% of strains were slime producers. The adhesion test revealed that 20% of strains are strongly adhering to T. pyriformis and that the Clematis cirrhosa extract has an anti-adhering effect of S. aureus to the ciliate T. pyriformis.
基金financially supported by the French"Agence Nationale de la Recherche"through the"Investissements d'avenir"Program(No.ANR-10-EQPX-37 MATMECA)the Chinese"International Exchange Program"(No.YJ20210129)the Shuimu Tsinghua Scholar Program(No.2020SM100)
文摘Selective oxidation of Fe-Mn alloys was characterizied through X-ray photoelectron spectroscopy and scanning/transmission electron microscopy during industrial continuous annealing(in an atmosphere of N_(2)-5 vol.%H_(2) with traces of water at 800℃).After annealing,only MnO oxides are formed on and below the surface and few iron oxides appear on the top surface due to oxidation of ambient air or the formation of FeO-MnO solid solutions.Mn concentration profiles exhibit typical selective oxidation and show similar features.Mn concentration first increases to a peak value at a depth of 5-10 nm from surface,and then decreases to the minimum at the oxidation front,following with a floating up and down to bulk composition.According to XPS spectra and Mn concentration profiles as a function of depth,the annealed alloy surfaces can be divided into four zones:ambient air contaminated zone,MnO enrichment zone(external and internal oxidation coexisting here),Mn depletion zone and bulk composition zone.Mn concentration reaches a minimum value at the oxidation front,whose position is deeper with annealing temperature and time increasing.The value of Mn diffusion coefficient in ferrite estimated using diffusion flux at the oxidation front is 2.9×10^(-15)m^(2)s^(-1) at 800℃,which is slightly greater than that in literature.
