Superposition of fiber Bragg and LPG gratings for embedded strain measurement

AbstractWhen a fiber Bragg grating strain sensor is embedded inside a structure, the interaction of the sensor with the host material can lead to spurious results if the radial strain is neglected. In this article, we use numerical simulations to show that the axial and radial strains can be simultaneously measured with a single fiber in which a Bragg grating and a long-period grating are superimposed. Moreover, we present an optimal architecture of the sensor

Polymorphisms of a Collagen-Like Adhesin Contributes to Legionella pneumophila Adhesion, Biofilm Formation Capacity and Clinical Prevalence

Legionellosis is a severe respiratory illness caused by the inhalation of aerosolized water droplets contaminated with the opportunistic pathogen Legionella pneumophila. The ability of L. pneumophila to produce biofilms has been associated with its capacity to colonize and persist in human-made water reservoirs and distribution systems, which are the source of legionellosis outbreaks. Nevertheless, the factors that mediate L. pneumophila biofilm formation are largely unknown. In previous studies we reported that the adhesin Legionella collagen-like protein (Lcl), is required for auto-aggregation, attachment to multiple surfaces and the formation of biofilms. Lcl structure contains three distinguishable regions: An N-terminal region with a predicted signal sequence, a central region containing tandem collagen-like repeats (R-domain) and a C-terminal region (C-domain) with no significant homology to other known proteins. Lcl R-domain encodes tandem repeats of the collagenous tripeptide Gly-Xaa-Yaa (GXY), a motif that is key for the molecular organization of mammalian collagen and mediates the binding of collagenous proteins to different cellular and environmental ligands. Interestingly, Lcl is polymorphic in the number of GXY tandem repeats. In this study, we combined diverse biochemical, genetic, and cellular approaches to determine the role of Lcl domains and GXY repeats polymorphisms on the structural and functional properties of Lcl, as well as on bacterial attachment, aggregation and biofilm formation. Our results indicate that the R-domain is key for assembling Lcl collagenous triple-helices and has a more preponderate role over the C-domain in Lcl adhesin binding properties. We show that Lcl molecules oligomerize to form large supramolecular complexes to which both, R and C-domains are required. Furthermore, we found that the number of GXY tandem repeats encoded in Lcl R-domain correlates positively with the binding capabilities of Lcl and with the attachment and biofilm production capacity of L. pneumophila strains. Accordingly, the number of GXY tandem repeats in Lcl influences the clinical prevalence of L. pneumophila strains. Therefore, the number of Lcl tandem repeats could be considered as a potential predictor for virulence in L. pneumophila isolates

Single-cell scattering and auto-fluorescence-based fast antibiotic susceptibility testing for gram-negative and gram-positive bacteria

In this study, we assess the scattering of light and auto-fluorescence from single bacterial cells to address the challenge of fast (<2 h), label-free phenotypic antimicrobial susceptibility testing (AST). Label-free flow cytometry is used for monitoring both the respiration-related auto-fluorescence in two different fluorescence channels corresponding to FAD and NADH, and the morphological and structural information contained in the light scattered by individual bacteria during incubation with or without antibiotic. Large multi-parameter data are analyzed using dimensionality reduction methods, based either on a combination of 2D binning and Principal Component Analysis, or with a one-class Support Vector Machine approach, with the objective to predict the Susceptible or Resistant phenotype of the strain. For the first time, both Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) isolates were tested with a label-free approach, and, in the presence of two groups of bactericidal antibiotic molecules, aminoglycosides and beta-lactams. Our results support the feasibility of label-free AST in less than 2 h and suggest that single cell auto-fluorescence adds value to the Susceptible/Resistant phenotyping over single-cell scattering alone, in particular for the mecA+ Staphylococcus (i.e., resistant) strains treated with oxacillin

New Endemic Legionella pneumophila Serogroup I Clones, Ontario, Canada

Identifying geographic distribution can improve surveillance and clinical testing procedures

Laboratory-based evaluation of legionellosis epidemiology in Ontario, Canada, 1978 to 2006

BACKGROUND: Legionellosis is a common cause of severe community acquired pneumonia and respiratory disease outbreaks. The Ontario Public Health Laboratory (OPHL) has conducted most testing for Legionella species in the Canadian province of Ontario since 1978, and represents a multi-decade repository of population-based data on legionellosis epidemiology. We sought to provide a laboratory-based review of the epidemiology of legionellosis in Ontario over the past 3 decades, with a focus on changing rates of disease and species associated with legionellosis during that time period. METHODS: We analyzed cases that were submitted and tested positive for legionellosis from 1978 to 2006 using Poisson regression models incorporating temporal, spatial, and demographic covariates. Predictors of infection with culture-confirmed L. pneumophila serogroup 1 (LP1) were evaluated with logistic regression models. Results: 1,401 cases of legionellosis tested positive from 1978 to 2006. As in other studies, we found a late summer to early autumn seasonality in disease occurrence with disease risk increasing with age and in males. In contrast to other studies, we found a decreasing trend in cases in the recent decade (IRR 0.93, 95% CI 0.91 to 0.95, P-value = 0.001); only 66% of culture-confirmed isolates were found to be LP1. CONCLUSION: Despite similarities with disease epidemiology in other regions, legionellosis appears to have declined in the past decade in Ontario, in contrast to trends observed in the United States and parts of Europe. Furthermore, a different range of Legionella species is responsible for illness, suggesting a distinctive legionellosis epidemiology in this North American region

Le phénomène killer chez la levure Williopsis saturnus var. mrakii (de la caractérisation de la protéine à la recherche du gène)

Williopsis saturnus var. mrakii MUCL41968 secrète une toxine killer (WmKT) qui est active contre un large spectre de micro-organismes pathogènes non reliés taxonomiquement. Des Anticorps monoclonaux anti-idiotypiques dirigés contre des anticorps neutralisants anti-WmKT, ont un effet létal contre Candida albicans, Pneumocystis carinii et Mycobacterium tuberculosis. Dans le but d'étudier le mécanisme de la WmKT, nous avons purifié cette toxine à partir de surnageants de culture de W. saturnus var. mrakii et montré qu'il s'agit d'une glycoprotéine de 85-kDa. Le séquençage partiel de la WmKT indique que cette toxine est apparentée aux protéines SUN de levure, mais pas aux autres toxines killer.Elle se fixe sur les cellules sensibles en utilisant les bêta-glucanes pariétaux et agit en induisant une augmentation rapide et létale de la perméabilité cellulaire. Une bêta-glucanase a un effet antagoniste sur l'activité de la toxine et des sphéroplastes dérivés de levures sensibles sont résistants à la WmKT, l'interaction avec les bêta-glucanes pariétaux semble donc requise pour l'obtention de l'effet létal de la WmKT. Un inhibiteur de glucosidase abolie l'effet biologique de la WmKT tout comme son activité hydrolytique vis-à-vis du p-nitrophényl bêta-D-glucopyranoside, il est donc probable que la WmKT agisse sur les levures sensibles en utilisant cette activité hydrolytique pour altérer la paroi cellulaire. Enfin, avec l'objectif de cloner le gène de la WmKT, nous avons isolé le gène WMSU1 du génome de W. saturnus var. mrakii. WMSU1 est un nouveau gène SUN codant une protéine pariétale apparentée à la WmKT. L'expression hétérologue de WMSU1 apparaît toxique pour son hôte et, tout comme la WmKT, elle induit des perturbations de la paroi cellulaire. L'analyse du génome de W. saturnus var. mrakii MUCL 41968 par Southern blot en utilisant un domaine très conservé de WMSU1 comme sonde montre que le gène isolé appartient à une famille multigénique qui contient certainement le gène codant la WmKT. Ces résultats suggèrent que la WmKT est une toxine killer d'un genre nouveau dont la caractérisation moléculaire conduira sans doute au développement d'un nouvel agent antimicrobien à large spectre.LILLE1-BU (590092102) / SudocSudocFranceF

Biofilms: the stronghold of Legionella pneumophila

Abstract: Legionellosis is mostly caused by Legionella pneumophila and is defined as a severe respiratory illness with a case fatality rate ranging from 5% to 80%. L. pneumophila is ubiquitous in natural and anthropogenic water systems. L. pneumophila is transmitted by inhalation of contaminated aerosols produced by a variety of devices. While L. pneumophila replicates within environmental protozoa, colonization and persistence in its natural environment are also mediated by biofilm formation and colonization within multispecies microbial communities. There is now evidence that some legionellosis outbreaks are correlated with the presence of biofilms. Thus, preventing biofilm formation appears as one of the strategies to reduce water system contamination. However, we lack information about the chemical and biophysical conditions, as well as the molecular mechanisms that allow the production of biofilms by L. pneumophila. Here, we discuss the molecular basis of biofilm formation by L. pneumophila and the roles of other microbial species in L. pneumophila biofilm colonization. In addition, we discuss the protective roles of biofilms against current L. pneumophila sanitation strategies along with the initial data available on the regulation of L. pneumophila biofilm formation

Biosensors for the Detection of Interaction between Legionella pneumophila Collagen-Like Protein and Glycosaminoglycans

The adhesin Legionella collagen-like (Lcl) protein can bind to extracellular matrix components and mediate the binding of Legionella pneumophila to host cells. In this study, electrochemical impedance spectroscopy (EIS) and surface plasmon resonance (SPR)-based biosensors were employed to characterize these interactions between glycosaminoglycans (GAGs) and the adhesin Lcl protein. Fucoidan displayed a high affinity (KD 18 nM) for Lcl protein. Chondroitin sulfate A and dermatan sulfate differ in the position of a carboxyl group replacing D-glucuronate with D-iduronate. Our results indicated that the presence of D-iduronate in dermatan sulfate strongly hindered its interaction with Lcl. These biophysical studies provided valuable information in our understanding of adhesin-ligand interactions related to Legionella pneumophila infections

De l'utilisation des capteurs à fibres optiques dans les matériaux composites

International audienceThe optical fiber sensors are high technology devices able to provide the strain at the core of a structure. Nevertheless, their performances depend on methods and models of optical signal analysis applied by users. The relations commonly used for the analysis of optical signals are based on simplifying hypotheses which prove to be efficient in some application cases but lead to substantial errors for different configurations. The first aim of this article is to discuss the validity of such hypotheses by studying two application cases: a single fiber in uniaxial tension and the study of a fiber embedded in a homogenous isotropic material. The second part of the article is dedicated to application cases for which it is no longer possible to identify a single peak of Bragg. We investigate the problem of an optical fiber submitted to a gradient of axial strains and then to non-uniform axial and radial strains.Les capteurs à réseaux de Bragg sont des outils technologiques de pointe à même de délivrer une information fiable quant à la déformation au cœur d'une structure. Toutefois, leurs performances dépendent beaucoup des méthodes et des modèles d'analyse du signal optique mis en œuvre par l'utilisateur. Or, les relations communément utilisées pour le dépouillement des signaux optiques reposent sur des hypothèses simplificatrices. Le premier objectif de cet article est d'en discuter la validité à travers deux cas d'application : la fibre en traction pure dans l'air et la fibre en traction enfouie dans un matériau homogène et isotrope. La seconde partie de l'article est consacrée à l'étude de cas de chargement pour lesquels il n'est plus possible d'identifier un unique pic de Bragg : une fibre optique soumise à un gradient de déformation axiale puis à un champ de déformations axiales et radiales non uniforme