Material influence on biocontamination level and adhering cell physiology

In most environments, association with a surface in a structure known as a biofilm is the prevailing microbial lifestyle. Several factors may influence the biofilm formation e.g. nutrients, temperature, flow velocity, initial microflora and the nature of materials. Considering the biocontamination mechanism described in four steps, the initial adhesion is a key element in the biocontamination phenomenon and the substratum is of major concern in controlling bacterial adhesion. Stainless steel is well used in numerous markets because of its high cleanability and corrosion resistance properties. However, other materials are put forward by focusing on properties which differentiate them from those of stainless steel. Thereby, to select the material best suited to the problem, there should have data on their aptitude for biocontamination as well as adhesion impact on cell physiology. For all materials, the ratio of dead adhering cells is lower than 55%. The results obtained show that cell injury is not higher on material known to be bactericidal than on other ones.Dans la plupart des environnements, les microorganismes vivent pr ́ ef ́ erentiellement au sein de biofilms. De nombreux facteurs influencent leur formation i.e. les nutriments, la temp ́ erature, le r ́ egime du fluide environnent, la microflore et les mat ́ eriaux. Dans le m ́ ecanisme de biocontamination, d ́ ecrit en quatre ́ etapes successives, l’adh ́ esion initiale est un ́ el ́ ement cl ́ e de la bioadh ́ esion et les mat ́ eriaux un ́ el ́ ement majeur pour son contr ˆ ole. L’acier inoxydable est tr ` es utilis ́ e dans de nombreux secteurs d’activit ́ e pour sa bonne nettoyabilit ́ e et son excellente r ́ esistance ` a la corrosion. Pour se diff ́ erencier, certains mat ́ eriaux mettent en avant d’autres propri ́ et ́ es.Ainsi,las ́ election du mat ́ eriau le mieux adapt ́ e ` a un probl ` eme donn ́ en ́ ecessite de connaitre son aptitude ` a la biocontamination ainsi que son impact sur la physiologie des microorganismes. Pour tous les mat ́ eriaux test ́ es, la mortalit ́ e des bact ́ eries adh ́ erentes est inf ́ erieure ` a55%.Lesr ́ esultats obtenus ont montr ́ e qu’un mat ́ eriau dit antimicrobien n’induit pas plus de cellules endommag ́ ees comparativement aux autres mat ́ eriaux

Les biosurfactants, des biomolécules à forte potentialité d'application

Biosurfactants are surface-active molecules synthesized by certain microorganisms. Their chemical nature as well as their surface-active properties are dramatically dependent on the type of microorganism (bacteria, yeasts, moulds), on the individual strain tested and on the available nutrients. The various known biosurfactants comprise glycolipids, lipopeptides, phospholipids, neutral lipids, fatty acids or lipopolysaccharides. As their chemical synthetic counterparts, they may exhibit emulsifying, foaming, wetting or dispersing properties, as well as more specific characteristics i.e. antibiotic activity. Such properties may be still efficient in extreme conditions such as acidic pH and high temperatures. In regard to their potentiality and their low toxicity, they are nowadays used in different applications such as environmental protection, petroleum industry, agronomy or cosmetology and should shortly settle in new sectors such as food processing, pharmaceutical industries or health care. The main objective of the following review is to synthesize the present knowledge in this research area.Les biosurfactants sont des molécules tensioactives produites par certains micro-organismes. Leur nature tout comme leur pouvoir tensioactif sont fortement dépendants du type de micro-organisme utilisé (bactéries, levures, champignons), de la souche testée ainsi que du substrat nutritif disponible pour le développement cellulaire. Parmi les différents biosurfactants recensés, on trouve aujourd’hui des glycolipides, des lipopeptides, des phospholipides, des lipides neutres, des acides gras ou des lipopolysaccharides. Tout comme leurs homologues de synthèse chimique, ils peuvent avoir des propriétés émulsifiantes, moussantes, mouillantes ou encore dispersantes, mais également des propriétés plus spécifiques (i.e. propriétés antibiotiques). Certaines de ces propriétés peuvent, de plus, être conservées dans des conditions extrêmes utilisation telles que pH acides, températures élevées, etc. Compte tenu de leurs potentialités et de leur innocuité, ils sont aujourd’hui utilisés dans différents domaines d’application tels que l’environnement, l’industrie pétrolière, l’agronomie ou encore la cosmétologie et devraient rapidement trouver leur place dans de nouveaux secteurs d’applications tels que les industries agroalimentaires, pharmaceutiques ou encore le domaine médical. La revue présentée ici a pour principal objectif de synthétiser les connaissances acquises à ce jour dans ce domaine

Material influence on biocontamination level and adhering cell physiology Influence des matériaux sur le niveau de biocontamination et la physiologie des cellules adhérentes

Dans la plupart des environnements, les microorganismes vivent préférentiellement au sein de biofilms. De nombreux facteurs influencent leur formation i.e. les nutriments, la température, le régime du fluide environnent, la microflore et les matériaux. Dans le mécanisme de biocontamination, décrit en quatre étapes successives, l'adhésion initiale est un élément clé de la bioadhésion et les matériaux un élément majeur pour son contrôle. L'acier inoxydable est très utilisé dans de nombreux secteurs d'activité pour sa bonne nettoyabilité et son excellente résistance à la corrosion. Pour se différencier, certains matériaux mettent en avant d'autres propriétés. Ainsi, la sélection du matériau le mieux adapté à un problème donné nécessite de connaitre son aptitude à la biocontamination ainsi que son impact sur la physiologie des microorganismes. Pour tous les matériaux testés, la mortalité des bactéries adhérentes est inférieure à 55 %. Les résultats obtenus ont montré qu'un matériau dit antimicrobien n'induit pas plus de cellules endommagées comparativement aux autres matériaux. In most environments, association with a surface in a structure known as a biofilm is the prevailing microbial lifestyle. Several factors may influence the biofilm formation e.g. nutrients, temperature, flow velocity, initial microflora and the nature of materials. Considering the biocontamination mechanism described in four steps, the initial adhesion is a key element in the biocontamination phenomenon and the substratum is of major concern in controlling bacterial adhesion. Stainless steel is well used in numerous markets because of its high cleanability and corrosion resistance properties. However, other materials are put forward by focusing on properties which differentiate them from those of stainless steel. Thereby, to select the material best suited to the problem, there should have data on their aptitude for biocontamination as well as adhesion impact on cell physiology. For all materials, the ratio of dead adhering cells is lower than 55%. The results obtained show that cell injury is not higher on material known to be bactericidal than on other ones

Determination of the van der Waals, electron donor and electron acceptor surface tension components of static Gram-positive microbial biofilms

A large number of studies have shown the influence of the physico-chemical properties of a surface on microbial adhesion phenomenon. In this study, we considered that the presence of a bacterial biofilm may be regarded as a "conditioning film" that may modify the physico-chemical characteristics of the support, and thus the adhesion capability of planktonic micro-organisms coming into contact with this substratum. In this context, we adapted a protocol for biofilm formation that allows, under our experimental conditions, contact angle measurements, the reference method to determine the energetic surface properties of a substratum. This made it possible to determine the van der Waals, electron acceptor and electron donor properties of static biofilms grown at 25 degrees C on stainless-steel slides with six Gram-positive bacteria isolated in dairy plants. A variance analysis indicated significant effects (P<0.05) of the bacterial strains and of the physiological state of the micro-organisms (planktonic or sessile) on the contact angles. To link the energetic properties of the six biofilms with direct adhesion experiments, we measured the affinity of fluorescent carboxylate-modified polystyrene beads for the different biofilm surfaces. The results correlated best with the electron-acceptor components of the biofilm surface energies, stressing the importance of Lewis acid-base interactions in adhesion mechanisms

Exploring complex transitions between polymorphs on a small scale by coupling AFM, FTIR and DSC: the case of Irganox 1076 (R) antioxidant

This study illustrates the significant interest of using atomic force microscopy (AFM) in force curve imaging mode for discovering and studying not easily detectable solid/solid transitions between polymorphs: we show that AFM in this imaging mode is a powerful means for studying in situ these transitions as they can be (i) detected in a very early step because of the high spatial resolution (at nanometer scale) of AFM and (ii) be distinguished from melting/recrystallization processes that can occur in the same temperature range. This was illustrated with the case of Irganox 1076 (R). This compound is a phenolic antioxidant currently used in standard polymers; it can bloom on the surface of polymer-based medical devices and its polymorphism might affect the device surface state and thus the biocompatibility. In a previous paper, the polymorphism of this compound was studied: four forms were characterized at a macroscopic level and one of them (form III) was identified on the surface of a polyurethane catheter. However, it was difficult to characterize the transitions between the different forms with only classical tools (DSC, FTIR and SAXS). In the present study, to evidence these transitions, we use AFM measurements coupled with a heating stage and we correlate them to ATR-FTIR measurements and to DSC analysis. This new study put into evidence a solid-solid transition between form III and II

Les flagelles d’Escherichia coli entérohémorragiques dans l’adhésion et la colonisation des surfaces

National audienc

Exploring complex transitions between polymorphs on a small scale by coupling AFM, FTIR and DSC: the case of Irganox 1076 (R) antioxidant

This study illustrates the significant interest of using atomic force microscopy (AFM) in force curve imaging mode for discovering and studying not easily detectable solid/solid transitions between polymorphs: we show that AFM in this imaging mode is a powerful means for studying in situ these transitions as they can be (i) detected in a very early step because of the high spatial resolution (at nanometer scale) of AFM and (ii) be distinguished from melting/recrystallization processes that can occur in the same temperature range. This was illustrated with the case of Irganox 1076 (R). This compound is a phenolic antioxidant currently used in standard polymers; it can bloom on the surface of polymer-based medical devices and its polymorphism might affect the device surface state and thus the biocompatibility. In a previous paper, the polymorphism of this compound was studied: four forms were characterized at a macroscopic level and one of them (form III) was identified on the surface of a polyurethane catheter. However, it was difficult to characterize the transitions between the different forms with only classical tools (DSC, FTIR and SAXS). In the present study, to evidence these transitions, we use AFM measurements coupled with a heating stage and we correlate them to ATR-FTIR measurements and to DSC analysis. This new study put into evidence a solid-solid transition between form III and II

Escherichia coli Resistance to Nonbiocidal Antibiofilm Polysaccharides Is Rare and Mediated by Multiple Mutations Leading to Surface Physicochemical Modifications

Antivirulence strategies targeting bacterial behavior, such as adhesion and biofilm formation, are expected to exert low selective pressure and have been proposed as alternatives to biocidal antibiotic treatments to avoid the rapid occurrence of bacterial resistance. Here, we tested this hypothesis using group 2 capsule polysaccharide (G2cps), a polysaccharidic molecule previously shown to impair bacterium-surface interactions, and we investigated the nature of bacterial resistance to a nonbiocidal antibiofilm strategy. We screened an Escherichia coli mutant library for an increased ability to form biofilm in the presence of G2cps, and we identified several mutants displaying partial but not total resistance to this antibiofilm polysaccharide. Our genetic analysis showed that partial resistance to G2cps results from multiple unrelated mutations leading to modifications in surface physicochemical properties that counteract the changes in ionic charge and Lewis base properties induced by G2cps. Moreover, some of the identified mutants harboring improved biofilm formation in the presence of G2cps were also partially resistant to other antibiofilm molecules. This study therefore shows that alterations of bacterial surface properties mediate only partial resistance to G2cps. It also experimentally validates the potential value of nonbiocidal antibiofilm strategies, since full resistance to antibiofilm compounds is rare and potentially unlikely to arise in clinical settings

Combined Effects of Long-Living Chemical Species during Microbial Inactivation Using Atmospheric Plasma-Treated Water▿

Electrical discharges in humid air at atmospheric pressure (nonthermal quenched plasma) generate long-lived chemical species in water that are efficient for microbial decontamination. The major role of nitrites was evidenced together with a synergistic effect of nitrates and H2O2 and matching acidification. Other possible active compounds are considered, e.g., peroxynitrous acid

Surface Engineering and Cell Adhesion

Cell adhesion is a multi-process phenomenon involving physical, physico-chemical and biological mechanisms. The complexity of interfaces is the reason why progress in the theory of cell adhesion has been slow. Greater understanding of interaction mechanisms has been enhanced by complete knowledge of supports and of biological components, in particular the extracellular matrix, membrane walls, cell multiplication processes and apoptosis. The construction of novel surfaces with strongly hydrophilic or ultrahydrophobic properties has allowed new theoretical advances, while at the same time offering numerous and varied technological applications. These include: • Bioadhesion with mechanical anchoring using ubiquitous surface roughness and deformability of certain micro-organisms. • Physico-chemical bioadhesion or repellence resulting mainly from the energy characteristics of support surfaces. • Processes of sorting and guidance by biomolecules present at the support–biofilm interface, generating biochemical responses that can induce cell multiplication or degeneration (as in cancer), or cell death