Papers by Florence Dubois-Brissonnet
Applied and Environmental Microbiology, 2011
To enhance food safety and stability, the food industry tends to use natural antimicrobials such ... more To enhance food safety and stability, the food industry tends to use natural antimicrobials such as plantderived compounds as an attractive alternative to chemical preservatives. Nonetheless, caution must be exercised in light of the potential for bacterial adaptation to these molecules, a phenomenon previously observed with other antimicrobials. The aim of this study was to characterize the adaptation of Salmonella enterica serovar Typhimurium to sublethal concentrations of four terpenes extracted from aromatic plants: thymol, carvacrol, citral, and eugenol, or combinations thereof. Bacterial adaptation in these conditions was demonstrated by changes in membrane fatty acid composition showing (i) limitation of the cyclization of unsaturated fatty acids to cyclopropane fatty acids when cells entered the stationary phase and (ii) bacterial membrane saturation. Furthermore, we demonstrated an increased cell resistance to the bactericidal activity of two biocides (peracetic acid and didecyl dimethyl ammonium bromide). The implications of membrane modifications in terms of hindering the penetration of antimicrobials through the bacterial membrane are discussed.
Applied and environmental microbiology, Jan 24, 2016
Salmonella is recognized as one of the most significant enteric foodborne bacterial pathogens. In... more Salmonella is recognized as one of the most significant enteric foodborne bacterial pathogens. In recent years, the resistance of pathogens to biocides and other environmental stresses, especially when these are embedded in biofilm structures, has led to the search and development of novel antimicrobial strategies capable of displaying both high efficiency and safety. To this direction, the aim of the present work was to evaluate the antimicrobial activity of hydrosol of the Mediterranean spice Thymbra capitata against both planktonic and biofilm cells of Salmonella Typhimurium, and to compare its action with the one of benzalkonium chloride (BC), a commonly used industrial biocide. In order to achieve this, the disinfectant activity following 6 min treatments was comparatively evaluated for both disinfectants by calculating their concentrations needed to achieve the same log-reductions against both types of cells. Their bactericidal effect against biofilm cells was also comparative...
Veterinary research
The bactericidal activity of various disinfectants (cationic or amphoteric surfactants, oxidizing... more The bactericidal activity of various disinfectants (cationic or amphoteric surfactants, oxidizing agents, phenolic derivatives) was determined against Escherichia coli CIP 54127 obtained by culture on tryptic soy agar (in-suspension or on-germ-carrier test) or in the form of biofilms produced in a continuous culture system. The bacteria tested on germ-carriers or included in biofilms were more resistant than the same strain in suspension. The extent of the reduction in activity depended on the nature of the disinfectant. In the two cases, the greatest reduction was observed with benzalkonium chloride and hexadecyl trimethylammonium bromide, the agents with the lowest hydrophile-lipophile balance. The activity of the oxidizing agents (sodium hypochlorite, peracetic acid/H2O2) and alkyl trimethylammonium derivatives (C12 and C14) was somewhat reduced, while that of the phenolic derivatives (o-cresol, phenol) was either slightly attenuated or unaffected. The reduction in sensitivity wa...
Food safety is dependent on the control of microbiological contamination on equipment surfaces in... more 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 contami- nation persists as a biofilm. The microorganisms present in a biofilm are generally less sensitive to disin- fection 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. SUMMARY
The etiology of food poisoning has changed considerably over time. Well-established pathogens are... more The etiology of food poisoning has changed considerably over time. Well-established pathogens are relatively well-controlled. However, microbial strains are able to evolve by acquiring new virulence factors or antibiotic resistance genes and by developing better tolerance to harmful environments. In addition, climate changes, changes in agricultural and / or technological practices, globalization of world trade, changes in consumption practices, can promote survival and spread of pathogens and thus can modify consumer exposure. All these factors combined with the increase in human sensitive subpopulations (elderly, immunocompromised ...) lead to the emergence of new pathogens in food chain.
Journal of food protection, 2007
The aim of this study was to determine the MICs of 14 antimicrobials for Salmonella Typhimurium w... more The aim of this study was to determine the MICs of 14 antimicrobials for Salmonella Typhimurium with three methods and to check the influence of experiment duration on the estimation of MICs. The growth of Salmonella Typhimurium in a brain heart infusion medium containing various concentrations of natural aromatic compounds, organic acids, or salts was monitored by absorbance measurements for 24 or 72 h. Three different ways of analyzing optical density (OD) curves were tested for the determination of MICs. Both quantitative methods gave similar MICs for most of the compounds. The semiquantitative method does not allow estimating the MIC for all compounds. Noticeable differences were found between MICs obtained for 24- or 72-h experiments, whatever the method used. The proposed methods and models can be used for the estimation of MICs from OD data. MICs could be used for a quantitative approach to Salmonella Typhimurium growth.
Microbios, 2001
The effects of changes in the fatty acid composition of Pseudomonas aeruginosa induced by growth ... more The effects of changes in the fatty acid composition of Pseudomonas aeruginosa induced by growth conditions on its resistance to two quaternary ammonium compounds (QAC) were investigated. The temperature and growth phase were the most influential parameters affecting the fatty acid composition of this bacterium. Furthermore, the formation of saturated fatty acids and cyclopropane fatty acids was stimulated by increasing the temperature, whereas the proportion of unsaturated fatty acids fell. The degree of saturation and the proportion of cyclopropane fatty acids increased in the course of the exponential and stationary phases. These modifications mostly concerned the inner membrane of the bacterium. Resistance of P. aeruginosa to both QAC tested was not significantly influenced by temperature and growth phase variations. Thus, resistance to the two QAC did not seem to be dependent on modifications of the fatty acid composition of the inner membrane.
Journal of Applied Microbiology, 2000
The in¯uence of supplementing the culture medium with magnesium sulphate, D-glucose, L-cysteine, ... more The in¯uence of supplementing the culture medium with magnesium sulphate, D-glucose, L-cysteine, catalase or lithium chloride, of incubation temperature and of oxygen availability on the recovery of salt-or acid-damaged Listeria monocytogenes, was studied on a solid repair medium according to a Hadamard matrix, with seven parameters varying between a high and a low level. The most important factors for repair of stressed Listeria were further studied with complete factorial design experiments. Results show that conditions promoting resuscitation of acid-or salt-injured cells are stress-speci®c, and differ in part from those described in the literature for heat-stressed Listeria.
Food Control, 2011
The purpose of the present study was to characterize the development of Listeria monocytogenes on... more The purpose of the present study was to characterize the development of Listeria monocytogenes on wooden shelves used for cheese ripening. The fate of two L. monocytogenes strains was analysed over time as a function of the presence of a native biofilm, the farmhouse origin of cheeses, and the wooden shelves properties. In presence of a native microbial flora on
AAC
The biocidal activity of peracetic acid (PAA) and benzalkonium chloride (BAC) on Pseudomonas aeru... more 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.
Biofouling
A biofilm can be defined as a community of microorganisms adhering to a surface and surrounded by... more A biofilm can be defined as a community of microorganisms adhering to a surface and surrounded by a complex matrix of extrapolymeric substances. It is now generally accepted that the biofilm growth mode induces microbial resistance to disinfection that can lead to substantial economic and health concerns. Although the precise origin of such resistance remains unclear, different studies have shown that it is a multifactorial process involving the spatial organization of the biofilm. This review will discuss the mechanisms identified as playing a role in biofilm resistance to disinfectants, as well as novel anti-biofilm strategies that have recently been explored.
J Microbiol Method
This study proposes a high throughput method based on Confocal Laser Scanning Microscopy (CLSM) c... more This study proposes a high throughput method based on Confocal Laser Scanning Microscopy (CLSM) combined with the use of 96-wells microtiter plates compatible with high resolution imaging for the study of biofilm formation and structure. As an illustration, the three-dimensional structures of biofilms formed by 60 opportunistic pathogens were thus observed and quantified. The results revealed the diversity of biofilm architectures. Specific spatial arrangement such as the mushroom-like structures already described for Pseudomonas aeruginosa was observed. Other features, such as hollow voids in microcolonies of Salmonella enterica strain Agona, were identified for the first time. The combined use of microplates and confocal imaging proved to be a good alternative to the other high throughput methods commonly used as it enables the direct, insitu, qualitative and quantitative characterization of biofilm architecture. This high content method should lead to a clearer understanding of the structure-function relationships implicated in biofilms traits.
Salmonella - Distribution, Adaptation, Control Measures and Molecular Technologies, 2012
Bulletin de l'Académie vétérinaire de France, 2006
Journal of Hospital Infection, 2011
Advances in Experimental Medicine and Biology, 2011
In natural, industrial and medical environments, microorganisms mainly live as structured and org... more In natural, industrial and medical environments, microorganisms mainly live as structured and organised matrix-encased communities known as biofilms. In these communities, microorganisms demonstrate coordinated behaviour and are able to perform specific functions such as dramatic resistance to antimicrobials, which potentially lead to major public health and industrial problems. It is now recognised that the appearance of such specific biofilm functions is intimately related to the three-dimensional organisation of the biological edifice, and results from multifactorial processes. During the last decade, the emergence of innovative optical microscopy techniques such as confocal laser scanning microscopy in combination with fluorescent labelling has radically transformed imaging in biofilm research, giving the possibility to investigate non-invasively the dynamic mechanisms of formation and reactivity of these biostructures. In this chapter, we discuss the contribution of fluorescence analysis and imaging to the study at different timescales of various processes: biofilm development (hours to days), antimicrobial reactivity within the three-dimensional structure (minutes to hours) or molecular diffusion/reaction phenomena (pico- to milliseconds).
Dobretsov/Biofouling Methods, 2014
to the treatments currently applied to limit biofilm formation in the environment of paper mill m... more to the treatments currently applied to limit biofilm formation in the environment of paper mill machines.
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Papers by Florence Dubois-Brissonnet