Global ETD Search

11	Architecture des biofilms et résistance à la désinfection : apport de l'imagerie de fluorescence multimodale / architecture of biofilms and resistance to disinfection : contribution of multimodal fluorescence imaging Bridier, Arnaud 09 June 2011 (has links) Dans les environnements naturels, industriels ou médicaux, les microorganismes sont majoritairement présents en étant associés aux surfaces dans des communautés hautement organisées appelées biofilms. Ces édifices biologiques constituent une stratégie de survie étonnement efficace témoignant d’une grande capacité de résistance à différent stress environnementaux tels que les traitements de nettoyage et de désinfection. L’impact des biofilms d’un point de vue sanitaire est donc considérable du fait qu’ils permettent la persistance et la transmission de germes pathogènes dans l’environnement. Dans ce contexte, ce travail de thèse avait pour objectif une meilleure compréhension des phénomènes limitant l’efficacité de désinfectants au sein des biofilms en s’appuyant notamment sur des techniques innovantes d’imagerie de fluorescence non-invasive. Le but final étant d’apporter des éléments utiles à l’optimisation des traitements de désinfection. Dans une première partie, une méthode d’investigation structurale à haut-débit par microscopie confocale a été développée et utilisée pour étudier la diversité architecturale des biofilms bactériens formés par un large panel de souches. Cette étude nous a permis d’identifier des souches d’intérêt en termes de structures de biofilms formés pour la suite du travail. Nous avons notamment pu mettre en évidence la capacité de B. subtilis à former des structures importantes et avec une architecture spécifique dans un système immergé. Dans une deuxième partie, les dynamiques d’action spatiotemporelles de désinfectants ont été visualisées dans les biofilms de souches de P. aeruginosa ou B. subtilis par des approches de microscopie confocale de fluorescence en temps réel. L’utilisation de cette technique nous a permis de mettre en évidence les difficultés de pénétration du chlorure de benzalkonium au sein des structures formées par différentes souches de P. aeruginosa. La corrélation des paramètres cinétiques d’inactivation et des données obtenues par la caractérisation biochimique de la matrice suggère un rôle majeur des substances extracellulaires dans la limitation de pénétraton du désinfectant. Nous avons également pu montrer une résistance marquée du biofilm formé par une souche de B. subtilis isolée d’un dispositif médical à l’acide péracétique, à la concentration et au temps d’utilisation du biocide dans le milieu médical. De plus, les structures tridimensionnelles formées par cette souche étaient capables de protéger le pathogène Staphylococcus aureus dans un biofilm mixte vis-à-vis du même traitement soulignant l’importance des interactions multi-espèces dans la résistance des bactéries aux désinfectants et la persistance de pathogènes dans nos environnements. / In natural, industrial or medical environments, microorganisms are present mainly in being associated with surfaces in highly organized communities called biofilms. These biological structures cosntitute a surprisingly effective survival strategy showing a large ability to withstand environmental stresses such as cleaning and disinfection treatments. Therefore, biofilms have a considerable impact on public health because they allow the persistence and transmission of pathogens. In this context, this work aimed to better understand the phenomena limiting the effectiveness of disinfectants in biofilms noticeably by using innovative imaging fluorescence non-invasive techniques. The ultimate goal was to provide data which can help to optimize disinfection treatments. In the first part, a high-throughput structural method based on confocal microscopy was developed and used to study the architectural diversity of bacterial biofilms formed by a wide range of strains. This study allowed us to identify strains of interest in terms of biofilm structure for the second part of the work. In particular, we demonstrated the ability of B. subtilis to form protruding structures with a specific architecture in a submerged system. In the second part, the spatiotemporal dynamic of the action of disinfectants were visualized in the biofilms of P. aeruginosa or B. subtilis strains by a time-lapse fluorescence confocal microscopy method. Using this technique, we showed that benzalkonium chloride encountered problems of penetration in the biofilms formed by P. aeruginosa strains. The correlation of kinetic inactivation parameters and data obtained by the characterization biochemical matrix suggested a key role of extracellular substances in the penetration limitations of the disinfectant. We also observed a pronounced resistance of the biofilm formed by a strain of B. subtilis isolated from a medical device to peracetic acid at the in-use concentration and time of biocide in medical areas. In addition, three-dimensional structures formed by this strains afforded protection to the pathogen Staphylococcus aureus in mixed biofilm against the same treatment This point highlights the importance of multi-species interactions in bacterial resistance to disinfectants and in the persistence of pathogens in our environments. Biofilm Désinfection Fluorescence Pseudomonas aeruginosa Bacillus subtilis Microscopie confocale Chlorure de benzalkonium Acide peracétique Biofilm Disinfection Fluorescence Pseudomonas aeruginosa Bacillus subtilis Confocal microscopy Benzalkonium chloride Peracetic acid 579.178
12	In vitro anti-bacterial activity of titanium oxide nano-composites containing benzalkonium chloride and chlorhexidine gluconate Atbayga, Abdalla Mohammed Ali January 2013 (has links) Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Biomedical Technology In the Faculty of Health and Wellness Sciences At Cape Peninsula University of Technology 2013 / Newly developed and commercial dental resins which are commonly used nowadays have to be tested for their antimicrobial susceptibility. The purpose of this in vitro study was to investigate the antimicrobial activity of a titanium oxide (TiO2) nano-composite which was prepared with different antibacterial substances and used as restoratives in dentistry to combat certain selected bacteria that are considered the principle causes of some tooth diseases, for example, tooth decay and to prevent unsuccessful dental restoration. The TiO2 nano-composite was prepared and divided into four groups: The first group was an untreated TiO2 nano-composite. The second group was silane-treated TiO2 nano-composite. The third group was treated TiO2 nano-composite which was combined with chlorhexidine gluconate (CHxG). The fourth group was treated TiO2 nano-composite which was combined with benzalkonium chloride (BzCl). Five of the selected bacteria were grown overnight in Petri dishes. Four of them, namely, Escherichia coli (E. coli) ATCC 11775, Staphylococcus aureus (S. aureus) ATCC 12600, Enterococcus faecalis (E. faecalis) ATCC 29212, and Pseudomonas aeruginosa (P. aeruginosa) ATCC 10145, were grown on Müller-Hinton Agar (MHA). Streptococcus mutans (S. mutans) ATCC 25175 was grown on Brain Heart Infusion (BHI) agar. All these bacteria were tested against the TiO2 nano-composite, and incubated for 24 hours at 37°C, except S. mutans, which was incubated separately and exposed to CO2. It was placed into a CO2 water-jacketed incubator in an atmosphere of 5% CO2 for 24 hours at 37°C. The obtained results showed that neither of the groups of TiO2 nano-composites, (untreated TiO2 nano-composite and treated TiO2 nano-composite) exhibited antimicrobial activity against the pathogens. Only preparations of TiO2 nano-composites at a concentration of 3 %m/m of both CHxG and BzCl showed antimicrobial activity against S. aureus. Antimicrobial activity against S. mutans, E. coli, P. aeruginosa, E. faecalis and S. aureus, were only realized at a concentration of 10 %m/m for both CHxG and BzCl.. Dental resins Dental materials Composite materials Nanostructured materials Nanocomposites (Material) Carbon dioxide Titanium oxide Camphorquinone Urethane dimethacrylate Silane Dental restoratvie materials Antimicrobial activity Benzalkonium chloride Chlorhexidine gluconate
13	Vliv hyaluronanu na vlastnosti očních kapek / Effects of hyaluronan on properties of eye drops Chromá, Kateřina January 2019 (has links) Modifying eye drops using hyaluronan leads to an increased retention time on the eye surface. Long-lasting observations of the stability of two different eye drops, Opthalmo-Septonex and Visine Classic, after the addition of hyaluronan with varying concentration are presented in this work. The interactions of hyaluronan with the eye drops, or their components benzalkonium chloride and tetryzoline, are investigated by monitoring particle sizes and the charge of the molecules. Additionally, rheological examinations of the samples are done and the mucoadhesion index is determined by using the mucine method.
14	Development of Sensitive In Vitro Assays to Assess the Ocular Toxicity Potential of Chemicals and Ophthalmic Products McCanna, David January 2009 (has links) The utilization of in vitro tests with a tiered testing strategy for detection of mild ocular irritants can reduce the use of animals for testing, provide mechanistic data on toxic effects, and reduce the uncertainty associated with dose selection for clinical trials. The first section of this thesis describes how in vitro methods can be used to improve the prediction of the toxicity of chemicals and ophthalmic products. The proper utilization of in vitro methods can accurately predict toxic threshold levels and reduce animal use in product development. Sections two, three and four describe the development of new sensitive in vitro methods for predicting ocular toxicity. Maintaining the barrier function of the cornea is critical for the prevention of the penetration of infections microorganisms and irritating chemicals into the eye. Chapter 2 describes the development of a method for assessing the effects of chemicals on tight junctions using a human corneal epithelial and canine kidney epithelial cell line. In Chapter 3 a method that uses a primary organ culture for assessing single instillation and multiple instillation toxic effects is described. The ScanTox system was shown to be an ideal system to monitor the toxic effects over time as multiple readings can be taken of treated bovine lenses using the nondestructive method of assessing for the lens optical quality. Confirmations of toxic effects were made with the utilization of the viability dye alamarBlue. Chapter 4 describes the development of sensitive in vitro assays for detecting ocular toxicity by measuring the effects of chemicals on the mitochondrial integrity of bovine cornea, bovine lens epithelium and corneal epithelial cells, using fluorescent dyes. The goal of this research was to develop an in vitro test battery that can be used to accurately predict the ocular toxicity of new chemicals and ophthalmic formulations. By comparing the toxicity seen in vivo animals and humans with the toxicity response in these new in vitro methods, it was demonstrated that these in vitro methods can be utilized in a tiered testing strategy in the development of new chemicals and ophthalmic formulations. in vitro Alternative Methods alamarBlue rhodamine tight junctions bovine lens viability toxicity mitochondria mitochondria integrity benzalkonium chloride sodium dodecyl sulphate sodium lauryl sulfate scanning electron microscopy Draize Draize maximal average scores zonula occludens cosmetic directive PETA humane society animal league ICCVAM ECVAM JaCVAM BCOP bovine cornea ocular irritants ocular irritation ocular toxicity human corneal epithelial cells vitro confocal confocal microscopy metabolic activity optical quality reactive oxygen species contact lens contact lens care solutions barrier function microbial keratitis mulitipurpose solutions tight junction cell damage claudin ZO-1 occludin MDCK Madin Madin-Darby canine kidney cells cornea human cornea human corneal epithelium epithelial cell line human corneal epithelial cell line sodium fluorescein sodium fluorescein permeability fluorescein permeability ocular surface cell monolayer Araki-Sasaki cell physiology risk assessment safety assessment ScanTox scanning laser lens epithelium corneal cells in vitro model ophthalmic formulations multiple instillation back vertex animal testing rabbit testing alternatives to animal testing cultured bovine lens toxicity of chemicals irritation irritants laser scanner organ culture delayed toxicity toxins hydrogen peroxide cornea toxicity cornea toxicity models prediction of human toxicity no observable adverse effect level lowest observable adverse effect level NOAEL LOAEL toxicity thresholds safety factors cornea uncertainty factors preservatives disinfectants ophthalmic products preclinical preclinical testing epithelial barrier drug penetration clinical confocal microscopy animal rights rabbit cornea human cornea human clinical effects toxic animal rights activist sensitive measures toxic effect toxicity threshold agar overlay agar diffusion agar overlay method agar diffusion method cytochrome cytochrome c apoptosis necrotic apoptotic necrosis caspase rhodamine 123 resazuran resorufin cell death cell viability metabolic dye microsomal microsomal enzymes cytotoxicity cytotoxic cytotoxic effect MTT XTT WST-1 plasma membrane mitochondrial mitochondrial morphology ocular toxicity potential ocular toxicity human corneal epithelial cell line confocal analysis corneal epithelium cell fluorescence alamarBlue assay rhodamine dye animal welfare toxic injury degraded mitochondria epithelial monolayer disinfectants membrane integrity eye toxicity eye viability dye toxicity in humans human toxicity effects on the mitochondria mitochondrial toxicity in vitro battery in vitro test battery ophthalmic eye drop direct contact product safety cytotoxicity potential molecular molecular biology refine reduce replace sensitivity and relevance sensitivity relevance rabbit ocular irritation test product development cytotoxicity models cytotoxicity alternative methods replacements for animal testing three r's beagle tiered testing tiered testing strategy replacements animal testing mechanistic toxicity cornea mitochondria dose response threshold Vision Science and Biology
15	Development of Sensitive In Vitro Assays to Assess the Ocular Toxicity Potential of Chemicals and Ophthalmic Products McCanna, David January 2009 (has links) The utilization of in vitro tests with a tiered testing strategy for detection of mild ocular irritants can reduce the use of animals for testing, provide mechanistic data on toxic effects, and reduce the uncertainty associated with dose selection for clinical trials. The first section of this thesis describes how in vitro methods can be used to improve the prediction of the toxicity of chemicals and ophthalmic products. The proper utilization of in vitro methods can accurately predict toxic threshold levels and reduce animal use in product development. Sections two, three and four describe the development of new sensitive in vitro methods for predicting ocular toxicity. Maintaining the barrier function of the cornea is critical for the prevention of the penetration of infections microorganisms and irritating chemicals into the eye. Chapter 2 describes the development of a method for assessing the effects of chemicals on tight junctions using a human corneal epithelial and canine kidney epithelial cell line. In Chapter 3 a method that uses a primary organ culture for assessing single instillation and multiple instillation toxic effects is described. The ScanTox system was shown to be an ideal system to monitor the toxic effects over time as multiple readings can be taken of treated bovine lenses using the nondestructive method of assessing for the lens optical quality. Confirmations of toxic effects were made with the utilization of the viability dye alamarBlue. Chapter 4 describes the development of sensitive in vitro assays for detecting ocular toxicity by measuring the effects of chemicals on the mitochondrial integrity of bovine cornea, bovine lens epithelium and corneal epithelial cells, using fluorescent dyes. The goal of this research was to develop an in vitro test battery that can be used to accurately predict the ocular toxicity of new chemicals and ophthalmic formulations. By comparing the toxicity seen in vivo animals and humans with the toxicity response in these new in vitro methods, it was demonstrated that these in vitro methods can be utilized in a tiered testing strategy in the development of new chemicals and ophthalmic formulations. in vitro Alternative Methods alamarBlue rhodamine tight junctions bovine lens viability toxicity mitochondria mitochondria integrity benzalkonium chloride sodium dodecyl sulphate sodium lauryl sulfate scanning electron microscopy Draize Draize maximal average scores zonula occludens cosmetic directive PETA humane society animal league ICCVAM ECVAM JaCVAM BCOP bovine cornea ocular irritants ocular irritation ocular toxicity human corneal epithelial cells vitro confocal confocal microscopy metabolic activity optical quality reactive oxygen species contact lens contact lens care solutions barrier function microbial keratitis mulitipurpose solutions tight junction cell damage claudin ZO-1 occludin MDCK Madin Madin-Darby canine kidney cells cornea human cornea human corneal epithelium epithelial cell line human corneal epithelial cell line sodium fluorescein sodium fluorescein permeability fluorescein permeability ocular surface cell monolayer Araki-Sasaki cell physiology risk assessment safety assessment ScanTox scanning laser lens epithelium corneal cells in vitro model ophthalmic formulations multiple instillation back vertex animal testing rabbit testing alternatives to animal testing cultured bovine lens toxicity of chemicals irritation irritants laser scanner organ culture delayed toxicity toxins hydrogen peroxide cornea toxicity cornea toxicity models prediction of human toxicity no observable adverse effect level lowest observable adverse effect level NOAEL LOAEL toxicity thresholds safety factors cornea uncertainty factors preservatives disinfectants ophthalmic products preclinical preclinical testing epithelial barrier drug penetration clinical confocal microscopy animal rights rabbit cornea human cornea human clinical effects toxic animal rights activist sensitive measures toxic effect toxicity threshold agar overlay agar diffusion agar overlay method agar diffusion method cytochrome cytochrome c apoptosis necrotic apoptotic necrosis caspase rhodamine 123 resazuran resorufin cell death cell viability metabolic dye microsomal microsomal enzymes cytotoxicity cytotoxic cytotoxic effect MTT XTT WST-1 plasma membrane mitochondrial mitochondrial morphology ocular toxicity potential ocular toxicity human corneal epithelial cell line confocal analysis corneal epithelium cell fluorescence alamarBlue assay rhodamine dye animal welfare toxic injury degraded mitochondria epithelial monolayer disinfectants membrane integrity eye toxicity eye viability dye toxicity in humans human toxicity effects on the mitochondria mitochondrial toxicity in vitro battery in vitro test battery ophthalmic eye drop direct contact product safety cytotoxicity potential molecular molecular biology refine reduce replace sensitivity and relevance sensitivity relevance rabbit ocular irritation test product development cytotoxicity models cytotoxicity alternative methods replacements for animal testing three r's beagle tiered testing tiered testing strategy replacements animal testing mechanistic toxicity cornea mitochondria dose response threshold Vision Science and Biology

Page generated in 0.0757 seconds