Dynamics of the action of biocides in Pseudomonas aeruginosa biofilms Bridier , Arnaud (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine); Dubois-Brissonnet , Florence (INRA , Jouy-En-Josas (France). UMR 1319 MICrobiologie de l'ALImentation au Service de la Santé Humaine); Greub , Gilbert (Centre Hospitalier Universitaire Vaudois, Lausanne(Suisse). Institut de Microbiologie) ...
2011
Publication
The biocidal activity of peracetic acid (PAA) and benzalkonium chloride (BAC) on Pseudomonas aeruginosa biofilms was investigated by using a recently developed confocal laser scanning microscopy ...(CLSM) method that enables the direct and real-time visualization of cell inactivation within the structure. This technique is based on monitoring the loss of fluorescence that corresponds to the leakage of a fluorophore out of cells due to membrane permeabilization by the biocides. Although this approach has previously been used with success with various Gram-positive species, it is not directly applicable to the visualization of Gram-negative strains such as P. aeruginosa, particularly because of limitations regarding fluorescence staining. After adapting the staining procedure to P. aeruginosa, the action of PAA and BAC on the biofilm formed by strain ATCC 15442 was investigated. The results revealed specific inactivation patterns as a function of the mode of action of the biocides. While PAA treatment triggered a uniform loss of fluorescence in the structure, the action of BAC was first localized at the periphery of cell clusters and then gradually spread throughout the biofilm. Visualization of the action of BAC in biofilms formed by three clinical isolates then confirmed the presence of a delay in penetration, showing that diffusion-reaction limitations could provide a major explanation for the resistance of P. aeruginosa biofilms to this biocide. Biochemical analysis suggested a key role for extracellular matrix characteristics in these processes.
Les textes qui suivent constituent le premier volet d’un dossier consacré au corps au Moyen Âge et dont un prochain numéro de la Revue des langues romanes donnera la suite et la fin. Les articles ...présentés ici sont le fruit d’une série de séminaires consacrés à cette question et tenus à Bordeaux en 2009 et 2010. Historiens et spécialistes de la littérature avaient alors dialogué autour de la question du corps et de ses représentations. Si une idée force se dégage de cette première partie du dossier, c’est celle-ci : le corps est neutre en régime chrétien. Il est un instrument et non un ennemi.
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