Les bactéries pathogènes opportunistes de l'Homme (bpo) sont retrouvées dans le milieu hospitalier où elles sont responsables d'infections nosocomiales ainsi que dans les milieux naturels terrestres et aquatiques. Elles présentent souvent des résistances intrinsèques aux antibiotiques élevées. En milieu clinique, l'usage intensif d'antibiotiques peut conduire à l'émergence de souches dites « Multi Drug Resistant ». L'anthropisation des milieux naturels peut également influencer la prévalence et les propriétés de résistance des bpo. Mes travaux ont porté sur l'impact de l'épandage d'amendements organiques sur la prévalence de bpo dans les sols, leur diversité génétique et leurs propriétés de résistance aux antibiotiques. Une étude des espèces Stenotrophomonas maltophilia, Pseudomonas aeruginosa et Burkholderia du « cepacia complexe » (Bcc) réalisée sur des sites du Burkina-Faso amendés ou non en déchets urbains bruts a mis en évidence des différences dans les propriétés de résistance des 3 modèles. S. maltophila présente fréquemment des phénotypes MDR contrairement à P. aeruginosa et aux Bcc. Une approche de génomique comparative entre souches de S. maltophilia d'origine environnementale ou clinique et de phénotypes sensibles à MDR a été réalisée afin d'élucider l'origine génétique de l'hétérogénéité des phénotypes de résistance. Une variation dans le contenu en pompes à efflux et la présence de pompes souche spécifique chez des souches environnementales ont été observées. L'étude de l'expression d'une de ces pompes confirme son implication dans la résistance aux antibiotiques et dans l'adaptation à des paramètres environnementaux tels que la température / Opportunistic bacterial pathogens (obp) of Man are found in hospital setting where they are responsible for nosocomial infections as well as in terrestrial and aquatic natural environments. Obp often show high intrinsic antibiotic resistance level. Moreover, the intensive use of antibiotics in clinical settings can lead to the emergence of "Multi Drug Resistant" strains. The anthropisation of the natural environment leads to modifications in bacterial diversity of these environments and can affect the prevalence and the antibiotic resistance properties of obp. My research focused on the impact of organic amendments on the prevalence, genetic diversity and antibiotic resistance properties of obp. A study on the species Stenotrophomonas maltophilia, Pseudomonas aeruginosa and the “Burkholderia cepacia complex" (Bcc) was conducted on sites in Burkina Faso amended or not with raw urban wastes. This study showed differences in antibiotic resistance properties between the 3 models. S. maltophila frequently showed MDR phenotypes unlike P. aeruginosa and Bcc. A comparative genomics study between S. maltophilia strains from environmental or clinical origin showing sensitive or MDR phenotypes was performed to elucidate the genetic origins of heterogeneity in the resistance phenotypes. A variation in the efflux pumps content was observed between strains. The expression of an efflux pump specific to an environmental MDR strain was then evaluated and confirmed its likely involvement in antibiotic resistance and adaptation to environmental parameters such as temperature

Dans le milieu clinique, Stenotrophomonas maltophilia est décrite comme bactérie pathogène opportuniste, responsable d'infections nosocomiales principalement chez des patients immunodéprimés ou présentant des pathologies sévères ou chroniques. L'impressionnant bouclier de résistance aux antibiotiques observé chez les souches cliniques rend les traitements particulièrement complexes pour les patients atteints. Les souches de S. maltophilia représentent une réelle menace pour la santé humaine. De plus, les fortes potentialités d'adaptation des S. maltophilia leur permettent une dispersion dans un éventail très large de biotopes cliniques mais aussi environnementaux. En effet, les S. maltophilia colonisent aussi abondamment les niches écologiques environnementales telles que les sols rhizosphériques. Le niveau des connaissances sur ces souches environnementales est particulièrement limité face à celui disponible du milieu médical. Les propriétés en tant que pathogène opportuniste de ces souches environnementales restent encore peu connues et controversées tant au niveau génétique que phénotypique. Afin de mieux évaluer le potentiel danger sanitaire que représentent les souches environnementales face aux souches cliniques, il a été envisagé lors de ce projet de thèse d'évaluer des caractéristiques phénotypiques d'un groupe de souches de S. maltophilia provenant de contextes différemment en contact avec l'homme et l'environnement. Des souches de S. maltophilia fortement impactées par le contact de l'homme ont été isolées de patients atteints de pathologies variables (mucoviscidose, infections nosocomiales, pathologies sévères). Ce groupe de souches considérées comme les plus à risque pour l'homme, a été comparé à un groupe de souches de S. maltophilia environnementales provenant de contextes ayant pu favoriser des acquisitions/maintiens de résistances aux molécules antimicrobiennes tels que les sols rhizosphériques, les sols pollués aux métaux lourds ou encore les sols soumis aux activités répétées de l'homme. Tout d'abord, les signatures métaboliques (croissance, dégradations de substrats) et les capacités de résistance à diverses molécules antibiotiques cliniques ont été évaluées pour la collection de souches de S. maltophilia. Dans un deuxième volet, ont été étudiées les potentialités de virulence de ces souches telles que la mobilité, les sécrétions enzymatiques, la formation de biofilm et la virulence envers des amibes. Enfin, une analyse croisée statistique a mis en lien les différentes signatures obtenues à partir des données métaboliques, de résistance aux antibiotiques et de virulence en confrontant les origines des souches et les influences qu'elles ont subies vis-à-vis de l'homme. D'après le jeu de données du projet, quatre signatures distinctes émergent entre les souches de S. maltophilia structurées par les effets dus la proximité de l'homme et à leur origine. Des souches environnementales potentiellement les plus impactées par les contacts avec l'homme possèdent des caractéristiques similaires aux souches cliniques ; elles sont donc potentiellement aussi dangereuses que les souches cliniques / In the clinical settings, Stenotrophomonas maltophilia is described as an opportunistic bacterial pathogen responsible for nosocomial infections mainly in immunocompromised patients or with severe or chronic diseases. The heavy shield of antibiotic resistances observed in clinical strains lead to particularly complex treatments for patients. S. maltophilia strains represent a real threat to human health. Moreover, the high potential for adaptation of S. maltophilia allow their dispersion in a wide range of clinical habitats but also environmental. Indeed, S. maltophilia strains also colonize widely environmental niches such as the rhizospheric soils. The knowledge about these environmental strains is particularly limited compared to the available medical data. The properties as opportunistic pathogenic of environmental strains remain poorly known and controversial. To better assess the potential health hazard of these environmental S. maltophilia compared to the clinical ones, were assessed in this Ph-D project phenotypic characteristics of a group of S. maltophilia strains from contexts differentially affected by human and environment imprints. S. maltophilia heavily impacted by human contacts have been isolated from patients with varying disease (cystic fibrosis, nosocomial infections, severe pathologies). This group of strains considered as the most at risk to humans, was compared to a group of S. maltophilia from environmental contexts that could promote acquisition/maintaining of resistances to antimicrobial molecules such as rhizospheric soils, heavy metal-contaminated soils or agricultural soils. Firstly, metabolic signatures (growth, substrate degradations) and antibiotic resistance capacities were evaluated among the collection of S. maltophilia strains. In a second part, were studied pathogenic potentialities of these strains such as mobility, enzyme secretions, biofilm formation and virulence to amoebae. Finally, a statistical analysis made connections on the different signatures obtained from the metabolic data, antibiotic resistance and virulence with the origins of the strains and human impacts. According to the datasets of the project, four distinct signatures emerged between S. maltophilia strains structured by the effects of human proximity and origin of the strains. Environmental strains potentially the most impacted by contact with humans showed similar characteristics with the clinical strains; they could potentially be as dangerous as clinical strains

Les espèces bactériennes opportunistes responsables d'infections nosocomiales chez l'Homme se rencontrent dans les environnements terrestres et aquatiques. Elles sont très souvent caractérisées par une résistance naturelle aux antibiotiques leur conférant un phénotype appelé Multi-Drug Resistant (MDR). L'efflux d'antibiotiques via des pompes, est un des mécanismes à l'origine de cette multi-résistance. Alors que le rôle de ces pompes chez des bactéries isolées en milieu clinique est connu, aucune donnée n'est disponible concernant leur rôle chez les bactéries associées avec d'autres organismes eucaryotes du sol tels que les amibes. Pourtant des données de la littérature indiquent que les amibes, jusqu'alors principalement connues pour leur rôle prédateur de bactéries sont susceptibles d'héberger des bactéries " résistantes " aux amibes (ARB). Parmi ces ARB, des pathogènes opportunistes ont été identifiés dont certains sont connus pour être porteurs de pompes à efflux. Les pompes à efflux de ces bactéries pourraient donc intervenir dans l'adaptation aux amibes du sol. Afin de vérifier cette hypothèse, nous avons, dans un premier temps, isolé et identifié la flore amibienne et les ARB de différents sols. Parmi les ARB identifiées, Stenotrophomonas maltophilia, Pseudomonas aeruginosa et Burkholderia cepacia sont caractérisées par des propriétés d'antibiorésistance contrastées et de virulence élevées. Des études d'interaction ont montré que S. maltophilia se multipliait dans des amibes axéniques et que des pompes à efflux Sme étaient surexprimées. Par ailleurs des molécules sécrétées par l'amibe stimulent la croissance bactérienne et des études préliminaires de profilage métabolique ont montré la présence de différents métabolites secondaires produits par l'amibe au cours de l'interaction avec S. maltophilia pouvant jouer un rôle dans l'expression des pompes à efflux / The opportunistic bacterial species, responsible for nosocomial infections in humans, occurs in terrestrial and aquatic environments. They are often characterized by natural resistance to antibiotics giving them a phenotype called Multi-Drug Resistant (MDR). The efflux of antibiotics via pumps, is one of the mechanisms behind this multi-resistance. While the role of these pumps in bacteria isolated from hospital is known, no data are available regarding their role in bacteria associated with other soil eukaryotic organisms such as amoebae. Nevertheless, data from the literature indicate that amoebae, mainly known to be predators of bacteria, are likely to harbour "amoeba resistant bacteria” (ARB). Among these ARB, opportunistic pathogens have been identified, some of which are known to be carriers of efflux pumps. The efflux pumps of these bacteria could thus interfere in the adaptation to soil amoebae. In order to verify this hypothesis, we first isolated and identified the amoebal population and the ARB of different soils. Among the identified ARB, Stenotrophomonas maltophilia, Pseudomonas aeruginosa and Burkholderia cepacia are characterized by high contrast antibiotic resistance and high virulence. Interaction studies showed that S. maltophilia could multiplied in axenic amoebae and Sme efflux pumps were overexpressed. Furthermore, molecules secreted by the amoeba stimulate bacterial growth and preliminary studies of metabolic profile have shown that production of various secondary metabolites by the amoeba during the interaction with S. maltophilia could play a role in the efflux pumps expression

Thesis (Ph. D.)--Miami University, Dept. of Chemistry and Biochemistry, 2008. / Title from second page of PDF document. Includes bibliographical references.

Indiana University-Purdue University Indianapolis (IUPUI) / Cystic fibrosis (CF) is a fatal, incurable genetic disease that affects over 30,000 people in the United States alone. People with this disease have a homozygous mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) which causes defects in chloride transport and leads to build up of mucus in the lungs and disruption of function in various organs. CF patients often suffer from chronic bacterial infections within the lungs, wherein the bacteria persist as a biofilm, leading to poor prognosis. Two of these pathogens, Stenotrophomonas maltophilia and Pseudomonas aeruginosa, are often found in the lungs of patients with CF and are an increasing medical concerns due to their intrinsic antimicrobial resistance. Both species can readily form biofilms on biotic and abiotic surfaces such as intravascular devices, glass, plastic, and host tissue. Biofilm formation starts with bacterial attachment to a surface and/or adjacent cells, initiating the acute infection stage. Chronic, long-term infection involves subsequent or concurrent altered genetic regulation, including a downregulation of virulence factors, resulting in the bacteria committing to a sessile lifestyle, markedly different from the planktonic one. Many of these genetic switches from an acute to chronic lifestyle are due to pressures from the host immune system and lead to permanently mutated strains, most likely an adaptive strategy to evade host immune responses. Biofilms are extremely problematic in a clinical setting because they lead to nosocomial infections and persist inside the host causing long-term chronic infections due to their heightened tolerance to almost all antibiotics. Understanding the genetic networks governing biofilm initiation and maintenance would greatly reduce consequences for CF and other biofilm-related infections and could lead to the development of treatments and cures for affected patients. This study showed that in S. maltophilia, isogenic deletion of phosphoglycerate mutase (gpmA) and two chaperone-usher pilin subunits, S. maltophilia fimbrae-1 (smf-1) and cblA, lead to defects in attachment on abiotic surfaces and cystic fibrosis derived bronchial epithelial cells (CFBE). Furthermore, Δsmf-1 and ΔcblA showed defects in long-term biofilm formation, mimicking that of a chronic infection lifestyle, on abiotic surfaces and CFBE as well as stimulating less of an immune response through TNF-α production. This study also showed that in P. aeruginosa, the Type III secretion system (T3SS), an important virulence factor activated during the acute stage of infection, is downregulated when polB, a stress-induced alternate DNA polymerase, is overexpressed. This downregulation is due to post-transcriptional inhibition of the master regulatory protein, ExsA. Taken together, this project highlights important genes involved in the acute and chronic infection lifestyle and biofilm formation in S. maltophilia and genetic switches during the acute infection lifestyle in P. aeruginosa.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18888号 / 医博第3999号 / 新制||医||1009(附属図書館) / 31839 / 京都大学大学院医学研究科医学専攻 / (主査)教授 中川 一路, 教授 木原 正博, 教授 西渕 光昭 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

yes / Recent studies portend a rising global spread and adaptation of human- or healthcare- associated pathogens. Here, we analyse an international collection of the emerging, multi-drug-resistant, opportunistic pathogen Stenotrophomonas maltophilia from 22 countries to infer population structure and clonality at a global level. We show that the S. maltophilia complex is divided into 23 monophyletic lineages, most of which harbour strains of all degrees of human virulence. Lineage Sm6 comprises the highest rate of human-associated strains, linked to key virulence and resistance genes. Transmission analysis identifies potential outbreak events of genetically closely related strains isolated within days or weeks in the same hospitals.

No description available.

Cystic fibrosis (CF) is a fatal, incurable genetic disease that affects over 30,000 people in the United States alone. People with this disease have a homozygous mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) which causes defects in chloride transport and leads to build up of mucus in the lungs and disruption of function in various organs. CF patients often suffer from chronic bacterial infections within the lungs, wherein the bacteria persist as a biofilm, leading to poor prognosis. Two of these pathogens, <i>Stenotrophomonas maltophilia</i> and <i>Pseudomonas aeruginosa</i>, are often found in the lungs of patients with CF and are an increasing medical concerns due to their intrinsic antimicrobial resistance. Both species can readily form biofilms on biotic and abiotic surfaces such as intravascular devices, glass, plastic, and host tissue. Biofilm formation starts with bacterial attachment to a surface and/or adjacent cells, initiating the acute infection stage. Chronic, long-term infection involves subsequent or concurrent altered genetic regulation, including a downregulation of virulence factors, resulting in the bacteria committing to a sessile lifestyle, markedly different from the planktonic one. Many of these genetic switches from an acute to chronic lifestyle are due to pressures from the host immune system and lead to permanently mutated strains, most likely an adaptive strategy to evade host immune responses. Biofilms are extremely problematic in a clinical setting because they lead to nosocomial infections and persist inside the host causing long-term chronic infections due to their heightened tolerance to almost all antibiotics. Understanding the genetic networks governing biofilm initiation and maintenance would greatly reduce consequences for CF and other biofilm-related infections and could lead to the development of treatments and cures for affected patients. This study showed that in<i> S. maltophilia</i>, isogenic deletion of phosphoglycerate mutase (<i>gpmA</i>) and two chaperone-usher pilin subunits, <i>S. maltophilia</i> fimbrae-1 (<i>smf-1</i>) and<i> cblA</i>, lead to defects in attachment on abiotic surfaces and cystic fibrosis derived bronchial epithelial cells (CFBE). Furthermore, Δ<i>smf-1</i> and Δ<i>cblA</i> showed defects in long-term biofilm formation, mimicking that of a chronic infection lifestyle, on abiotic surfaces and CFBE as well as stimulating less of an immune response through TNF-α production. This study also showed that in <i>P. aeruginosa</i>, the Type III secretion system (T3SS), an important virulence factor activated during the acute stage of infection, is downregulated when <i>polB</i>, a stress-induced alternate DNA polymerase, is overexpressed. This downregulation is due to post-transcriptional inhibition of the master regulatory protein, ExsA. Taken together, this project highlights important genes involved in the acute and chronic infection lifestyle and biofilm formation in <i>S. maltophilia</i> and genetic switches during the acute infection lifestyle in <i>P. aeruginosa</i>.