The role of biofilms in the development and dissemination of microbial resistance within the food industry

Biofilms are multicellular sessile microbial communities embedded in hydrated extracellular polymeric matrices. Their formation is common in microbial life in most environments, while those formed on food-processing surfaces are of considerable interest in the context of food hygiene. Biofilm cells express properties that are distinct from planktonic ones, in particular, notorious resistance to antimicrobial agents. Thus, a special feature of biofilms is that, once they have been developed, they are hard to eradicate, even when careful sanitization procedures are regularly applied. A great deal of ongoing research has investigated how and why surface-attached microbial communities develop such resistance, and several mechanisms are to be acknowledged (e.g., heterogeneous metabolic activity, cell adaptive responses, diffusion limitations, genetic and functional diversification, and microbial interactions). The articles contained in this Special Issue deal with biofilms of some important food-related bacteria (including common pathogens such as Salmonella enterica, Listeria monocytogenes, and Staphylococcus aureus, as well as spoilage-causing spore-forming bacilli), providing novel insights on their resistance mechanisms and implications, together with novel methods (e.g., use of protective biofilms formed by beneficial bacteria, enzymes) that could be used to overcome such resistance and thus improve the safety of our food supply and protect public health

Chemical or natural tools to control microbiological contamination of surfaces

Food safety is dependent on the control of microbiological contamination on equipment surfaces in food processing facilities. Cleaning/disinfection procedures are not always adequate and microbial contamination persists as a biofilm. The microorganisms present in a biofilm are generally less sensitive to disinfection treatments than their planktonic counterparts. The increased resistance of biofilms is frequently attributed to the presence of a “protective” organic matrix and the particular physiology of cells within the biofilm. New curative methods are currently emerging for equipment surface decontamination: for instance, some of these use the interesting bactericidal potential of natural compounds.La qualité hygiénique des aliments nécessite une maîtrise de la contamination surfacique des équipements des ateliers de transformation alimentaire. Parfois, les procédures de nettoyage/désinfection s'avèrent limitées et une contamination microbienne subsiste alors sous forme de biofilm. Les micro-organismes contenus dans un biofilm sont généralement moins sensibles aux traitements de désinfection que leurs homologues planctoniques. La présence d'une matrice organique « protectrice » et la physiologie particulière des cellules au sein du biofilm sont fréquemment avancées comme explications à la résistance accrue des biofilms. De nouvelles méthodes curatives se développent actuellement pour limiter la contamination des surfaces utilisant les potentialités bactéricides intéressantes de certains antimicrobiens naturels

Characterization of cider by its hydrophobicproteinprofile and foamparameters

This paper describes the characterization of ciders (both “natural” and sparkling cider) from the Principality of Asturias (northwest region of Spain) through the analysis of their protein content, based on their hydrophobic properties, and their foam characteristics. A reversed-phase high performance liquid chromatography (RP-HPLC) was applied to the protein analysis, and the foamparameters were measured with Bikerman’s method. Multivariate techniques allowed the authors to differentiate ciders on the basis of the press and foam taking technologies, and foam sensory quality. Feasible and robust models were constructed for classifying purposes. Higher than 95% correct classifications were obtained for differentiating ciders on the basis of the factors studied (cider making technology and foam sensory quality). The multivariate regression model computed allowed the authors to predict (correlation coefficients higher than 0.8) the foamparameters related to foam stability and bubble average lifetime in “natural” cider

Ferulic Acid and Eugenol Have Different Abilities to Maintain Their Inhibitory Activity Against Listeria monocytogenes in Emulsified Systems

Natural phenolic compounds are found in large quantities in plants and plant extracts and byproducts from agro-industries. They could be used to ensure food quality and safety due to their antimicrobial properties demonstrated in systems such as culture media. The aim of this study was to evaluate the ability of two natural phenolic compounds, ferulic acid and eugenol, to maintain their inhibitory activity against the growth of Listeria monocytogenes in an oil-in-water emulsion, simulating a complex food system. The minimum inhibitory concentration (MIC) of each phenolic compound was first determined in culture medium, consisting of TS broth and an added emulsifier. Whey proteins and Tween 80 increased the MIC of the antimicrobial activity of eugenol. The MIC of ferulic acid was less affected by the addition of Tween 80. The inhibitory activities of both phenolic compounds were then compared at the same concentration in emulsions and their corresponding aqueous phases by following the growth of L. monocytogenes by plate counting. In emulsified systems, eugenol lost the high inhibitory activity observed in the aqueous phase, whereas ferulic acid retained it. The partition coefficient (logPoct/wat) appears to be a key factor. Eugenol (logPoct/wat = 2.61) dispersed in the aqueous phase intercalates into the bacterial membrane and has high antimicrobial activity. In contrast, it likely preferentially partitions into the lipid droplets when dispersed in an emulsion, consequently losing its antimicrobial activity. As ferulic acid is more hydrophilic, a higher proportion probably remains in the aqueous phase of the emulsion, retaining its antimicrobial activity

Multivalency To Inhibit and Discriminate Hexosaminidases

A set of multivalent polyhydroxylated acetamidoazepanes based on ethylene glycol, glucoside, or cyclodextrin scaffolds was prepared. The compounds were assessed against plant, mammalian, and therapeutically relevant hexosaminidases. Multimerization was shown to improve the inhibitory potency with synergy, and to fine tune the selectivity profile between related hexosaminidases

The Spatial Architecture of Bacillus subtilis Biofilms Deciphered Using a Surface-Associated Model and In Situ Imaging

The formation of multicellular communities known as biofilms is the part of bacterial life cycle in which bacteria display cooperative behaviour and differentiated phenotypes leading to specific functions. Bacillus subtilis is a Gram-positive bacterium that has served for a decade as a model to study the molecular pathways that control biofilm formation. Most of the data on B. subtilis biofilms have come from studies on the formation of pellicles at the air-liquid interface, or on the complex macrocolonies that develop on semi-solid nutritive agar. Here, using confocal laser scanning microcopy, we show that B. subtilis strains of different origins are capable of forming biofilms on immersed surfaces with dramatically protruding “beanstalk-like” structures with certain strains. Indeed, these structures can reach a height of more than 300 µm with one undomesticated strain from a medical environment. Using 14 GFP-labeled mutants previously described as affecting pellicle or complex colony formation, we have identified four genes whose inactivation significantly impeded immersed biofilm development, and one mutation triggering hyperbiofilm formation. We also identified mutations causing the three-dimensional architecture of the biofilm to be altered. Taken together, our results reveal that B. subtilis is able to form specific biofilm features on immersed surfaces, and that the development of these multicellular surface-associated communities involves regulation pathways that are common to those governing the formation of pellicle and/or complex colonies, and also some specific mechanisms. Finally, we propose the submerged surface-associated biofilm as another relevant model for the study of B. subtilis multicellular communities

Little Red Riding Hood... yet again? : The tale adapted to youth literature and standing the test of a modern world.

Cette thèse propose une lecture des réécritures du Petit Chaperon Rouge en littérature de jeunesse des années 1970 à nos jours. Elle montre que les œuvres ne peuvent se définir uniquement dans la relation qu'elles entretiennent avec l'hypotexte de Charles Perrault ou celui des frères Grimm qui constitue un élément, seulement, de leur construction. Il faut donc dépasser cette analyse traditionnelle qui participe à enfermer ces livres en les considérant alors comme un autre Petit Chaperon Rouge... encore un ! Ainsi, le retour sur le modèle de Gérard Genette proposé dans Palimpsestes, ne sera qu'un point de départ à l'étude. La culture commune du conte et sa plasticité permettent un nombre infini de jeux du texte et de l'image à tel point que la typologie de Genette est insuffisante pour rendre compte des transpositions du conte. Ces éditions sont marqués par leur époque et à ce titre témoignent de l'évolution de la cellule familiale et de celle de la littérature de jeunesse car c'est bien à cet ensemble plus vaste qu'elles appartiennent. Elles sont porteuses d'une dynamique éditoriale forte et stimulante amenant l'éditeur comme le créateur à se démarquer des autres collections de contes mais aussi des autres types de productions en littérature de jeunesse. Ainsi, non seulement ces Petit Chaperon Rouge ont su évoluer en même temps que la littérature de jeunesse mais aussi être le moteur de nouvelles formes d'expression. Le corpus nous a permis de questionner la littérature de jeunesse plus généralement : l'opposition systématique par exemple entre un auteur/illustrateur et un auteur distinct de l'illustrateur ne résiste pas à ces œuvres.This thesis suggests a reading of Little Red Riding's rewritings in youth literature from the 1970s to nowadays. It shows that the works can't only be defined through their relationship with Charles Perrault's or the Grimm brothers' hypotext which is just one element in their building. This traditional analysis which tends to imprison these books, thus considered as one more Little red Riding Hood (yet again…), must be overtaken. Thus, Gérard Genette's model proposed in Palimpsestes is only the starting point of our work. The tale's common culture and plasticity allow countless games with texts and pictures, that's why Genette's typology is not enough to explain the transpositions of the story. These editions are marked by their times in so far as they indicate an evolution in the family unit as well as in youth literature, for they belong to this larger set. They bring a strong and stimulating editorial dynamic, leading the publisher and the creator to distinguish themselves from other collections of tales as from other types of youth literature works. Thus, not only these Little Red Riding Hood‘s transpositions evolved in the same time as youth literature but they launched new forms of expression. Thanks to the corpus, youth literature could be more generally questioned: for example, a systematic opposition between an author/illustrator and an author different from the illustrator doesn't stand up to the corpus