108 research outputs found
Infections of implantable cardiac devices by biofilm forming bacteria in western Algeria hospitals
Background: The significant increase in the use of implantable cardiac devices (ICDs) has been accompanied by biofilm formation and increase rate of infection on the devices. The purpose of our study is to describe the clinical and microbiological findings of infection of ICDs in the cardiology units of western Algeria hospitals.
Methodology: All patients with clinical diagnosis of ICD infections or infective endocarditis upon removal of their ICDs from December 2012 to August 2014 in cardiology units of 4 Algerian hospitals were included in the study. Each element of the ICD pocket and lead was separately sonicated in sterile saline, inoculated onto Chapman and MacConkey agar plates and incubated aerobically at 37oC for colony count after 24 hours. Biochemical identification of the bacteria isolates was made by API 20E, API 20 NE and API Staph, and confirmed by Siemens Healthcare Diagnostics WalkAwayÂź 96 Plus System. Antibiotic susceptibility testing on each isolate was performed by the disk diffusion method on Mueller Hinton agar. Biofilm formation was detected by Congo Red Agar (CRA) and Tissue Culture Plate (TCP) methods, and hydrophobicity of the bacterial cell was determined by the MATH protocol.
Results: Over a period of twenty-one months, 17 ICDs were removed from patients with post-operative infections; 6 (35.3%) had early infection of ICD and 11 (64.7%) had late ICD infection. Fifty-four bacterial strains were isolated and identified, with coagulase-negative staphylococci being the predominant bacteria with 46.3% (25/54). There was no significant association between hydrophobicity and antimicrobial resistance in the 54 isolates but there is positive correlation between biofilm production and antimicrobial resistance, with the strongest biofilm producers resistant to more than one antibiotic. Four independent predictors of infection of resynchronization devices were reported; reoperation, multi-morbidity, long procedure, and ICD implantation.
Conclusion: Our study is the first in Algeria to describe microbiological characteristics of ICD infection. The bacteria in the biofilm were protected, more resistant and tolerated high concentrations of antibiotics and thus played a major role in the development of ICD infections. Despite the improvements in ICD design and implantation techniques, ICD infection remains a serious challenge.
Keywords: implantable cardiac devices, staphylococci, resistance, biofilm, hydrophobicity
French title: Infections des dispositifs cardiaques implantables par des bactéries formant un biofilm dans les hÎpitaux de l'ouest Algérien
Contexte: L'augmentation significative de l'utilisation des dispositifs cardiaques implantables est un risque majeur d'augmentation du taux d'infection et donc du risque de formation d'un biofilm sur ce genre de dispositifs. L'objectif de notre étude est de décrire les résultats cliniques et microbiologiques de l'infection sur les dispositifs cardiaques implantables (DCI) dans les unités de cardiologie des hÎpitaux de l'ouest Algérien.
Méthodologie: Tous les patients cliniquement diagnostiqués avec une infection sur DCI, ou une endocardite infectieuse et ayant subit un retrait de leur dispositif cardiaque sont inclus dans cette étude et cela sur une période entre décembre 2012 et aout 2014 dans 4 unités de cardiologie. Chaque élément du DCI (boitier et sonde) est trempé séparément dans une solution saline stérile, ensemencé sur deux milieux de culture, un milieu de Chapman et un milieu MacConkey et incubé en aérobiose à 37°C pour la numération des colonies aprÚs 24 heures. L'identification biochimique des isolats de bactéries est effectuée par le API 20E, API 20 NE et API Staph, et confirmée par le systÚme WalkAwayŸ 96 Plus de Siemens Healthcare Diagnostics. Les tests de sensibilité aux antibiotiques de chaque isolat sont effectués par la méthode de diffusion des disques sur gélose de Mueller Hinton. La formation d'un biofilm est détectée par les méthodes de la gélose rouge du Congo (CRA) et de la plaque de culture tissulaire (TCP), et l'hydrophobicité de la cellule bactérienne est déterminée par le protocole MATH.
RĂ©sultats: Sur une pĂ©riode de 21 mois, 17 DCI sont retirĂ©s de patients atteints d'infections postopĂ©ratoires; 6 patients (35,3%) sont identifiĂ©s comme ayant une infection prĂ©coce sur leurs DCI et 11 patients (64,7%) ayant une infection tardive. Cinquante-quatre souches bactĂ©riennes sont isolĂ©es et identifiĂ©es, les staphylocoques Ă coagulase nĂ©gative Ă©tant les bactĂ©ries prĂ©dominantes avec 46,3% (25/54). Il n'y a pas d'association significative entre l'hydrophobicitĂ© et la rĂ©sistance aux antimicrobiens dans les 54 isolats, mais il existe une corrĂ©lation positive entre la production de biofilm et la rĂ©sistance aux antimicrobiens, les plus puissants en biofilm sont rĂ©sistant Ă plus d'un antibiotique. Quatre facteurs prĂ©dictifs indĂ©pendants dâinfection des dispositifs cardiaques implantable sont retrouvĂ©s dans ce travail: rĂ©-intervention, longue procĂ©dure, sujets multi-tarĂ©s, et implantation dâun DCI
Conclusion: Notre étude est la premiÚre en Algérie à décrire les caractéristiques microbiologiques de l'infection des DCI. Les bactéries présentes dans le biofilm sont protégées, plus résistantes et tolÚrent de fortes concentrations d'antibiotiques et jouent ainsi un rÎle majeur dans le développement des infections par DCI. Malgré des améliorations dans les techniques de conception et d'implantation de DCI, l'infection des dispositifs cardiaques implantables reste un problÚme grave et trÚs couteux.
Mots-clés: dispositifs cardiaques implantables; staphylocoque; résistance; biofilm; hydrophobicit
Multi-Lagrangians for Integrable Systems
We propose a general scheme to construct multiple Lagrangians for completely
integrable non-linear evolution equations that admit multi- Hamiltonian
structure. The recursion operator plays a fundamental role in this
construction. We use a conserved quantity higher/lower than the Hamiltonian in
the potential part of the new Lagrangian and determine the corresponding
kinetic terms by generating the appropriate momentum map. This leads to some
remarkable new developments. We show that nonlinear evolutionary systems that
admit -fold first order local Hamiltonian structure can be cast into
variational form with Lagrangians which will be local functionals of
Clebsch potentials. This number increases to when the Miura
transformation is invertible. Furthermore we construct a new Lagrangian for
polytropic gas dynamics in dimensions which is a {\it local} functional
of the physical field variables, namely density and velocity, thus dispensing
with the necessity of introducing Clebsch potentials entirely. This is a
consequence of bi-Hamiltonian structure with a compatible pair of first and
third order Hamiltonian operators derived from Sheftel's recursion operator.Comment: typos corrected and a reference adde
Magnetic Branes Supported by Nonlinear Electromagnetic Field
Considering the nonlinear electromagnetic field coupled to Einstein gravity
in the presence of cosmological constant, we obtain a new class of
-dimensional magnetic brane solutions. This class of solutions yields a
spacetime with a longitudinal nonlinear magnetic field generated by a static
source. These solutions have no curvature singularity and no horizons but have
a conic geometry with a deficit angle . We investigate the effects
of nonlinearity on the metric function and deficit angle and also find that for
the special range of the nonlinear parameter, the solutions are not asymptotic
AdS. We generalize this class of solutions to the case of spinning magnetic
solutions, and find that when one or more rotation parameters are nonzero, the
brane has a net electric charge which is proportional to the magnitude of the
rotation parameters. Then, we use the counterterm method and compute the
conserved quantities of these spacetimes. Finally, we obtain a constrain on the
nonlinear parameter, such that the nonlinear electromagnetic field is
conformally invariant.Comment: 15 pages, one eps figur
Holographic Superconductors with Power-Maxwell field
With the Sturm-Liouville analytical and numerical methods, we investigate the
behaviors of the holographic superconductors by introducing a complex charged
scalar field coupled with a Power-Maxwell field in the background of
-dimensional Schwarzschild AdS black hole. We note that the Power-Maxwell
field takes the special asymptotical solution near boundary which is different
from all known cases. We find that the larger power parameter for the
Power-Maxwell field makes it harder for the scalar hair to be condensated. We
also find that, for different , the critical exponent of the system is still
1/2, which seems to be an universal property for various nonlinear
electrodynamics if the scalar field takes the form of this paper.Comment: 14 pages, 1 figure, and 2 table
Effects of certain disinfectants and antibiotics on biofilm formation by Staphylococcus aureus isolated from medical devices at the University Hospital Center of Sidi Bel Abbes, Algeria
Background: Staphylococcus aureus is one of the species of bacteria most frequently isolated from medical devices. The ability to produce biofilm is an important step in the pathogenesis of these staphylococci infection, and biofilm formation is strongly dependent on environmental conditions as well as antibiotics and disinfectants used in the treatment and prevention of infections.Methodology: In this study, 28 S. aureus isolated from medical devices at the University Hospital Center of Sidi Bel Abbes in Northwestern Algeria were tested for biofilm formation by culture on Red Congo Agar (RCA). The tube method (TM) and tissue culture plate (TCP) techniques were also used to investigate the effect of penicillin, ethanol and betadine on pre-formed biofilm.Results: Nineteen S. aureus isolates produced biofilm on the RCA and 7 produced biofilms by the tube method, 2 of which were high producer. In addition, 9 S. aureus isolates produced biofilm on polystyrene micro-plates, and in the presence of penicillin and ethanol, this number increased to 19 and 11 biofilm producing S. aureus isolates respectively. On the other hand, no biofilm was formed in the presence of betadine.Conclusion: It is important to test for biofilm formation following an imposed external constraint such as disinfectants and antibiotics in order to develop new strategies to combat bacterial biofilms but also to better control their formation.
Keywords : Staphylococcus aureus, biofilm, medical device, disinfectant, antibiotic
French Title: Effets de certains désinfectants et antibiotiques sur la formation de biofilms par Staphylococcus aureus isolé à partir de dispositifs médicaux au Centre Hospitalier Universitaire de Sidi Bel AbbÚs, Algérie
Contexte: Staphylococcus aureus est l'une des espÚces de bactéries les plus fréquemment isolées des dispositifs médicaux. La capacité de produire du biofilm est une étape importante dans la pathogenÚse de ces infections à staphylocoques, et la formation de biofilm dépend fortement des conditions environnementales ainsi que des antibiotiques et des désinfectants utilisés dans le traitement et la prévention des infections.
Méthodologie: Dans cette étude, 28 S. aureus isolés à partir de dispositifs médicaux au Centre hospitalier universitaire de Sidi Bel AbbÚs dans le nord-ouest de l'Algérie ont été testés pour la formation de biofilm par culture sur gélose rouge du Congo (RCA). La méthode des tubes (TM) et les techniques de plaques de culture tissulaire (TCP) ont également été utilisées pour étudier l'effet de la pénicilline, de l'éthanol et de la bétadine sur le biofilm préformé.
Résultats: Dix-neuf isolats de S. aureus ont produit un biofilm sur le RCA et 7 ont produit des biofilms par la méthode des tubes, dont 2 étaient trÚs productifs. De plus, 9 isolats de S. aureus ont produit du biofilm sur des microplaques en polystyrÚne, et en présence de pénicilline et d'éthanol, ce nombre est passé à 19 et 11 isolats de S. aureus producteurs de biofilm respectivement. En revanche, aucun biofilm ne s'est formé en présence de bétadine.
Conclusion: Il est important de tester la formation de biofilm suite à une contrainte externe imposée comme les désinfectants et les antibiotiques afin de développer de nouvelles stratégies pour lutter contre les biofilms bactériens mais aussi pour mieux contrÎler leur formation.
Mots-clés: Staphylococcus aureus, biofilm, dispositif médical, désinfectant, antibiotique
 
Ricci flat rotating black branes with a conformally invariant Maxwell source
We consider Einstein gravity coupled to an gauge field for which the
density is given by a power of the Maxwell Lagrangian. In -dimensions the
action of Maxwell field is shown to enjoy the conformal invariance if the power
is chosen as . We present a class of charge rotating solutions in
Einstein-conformally invariant Maxwell gravity in the presence of a
cosmological constant. These solutions may be interpreted as black brane
solutions with inner and outer event horizons or an extreme black brane
depending on the value of the mass parameter. Since we are considering power of
the Maxwell density, the black brane solutions exist only for dimensions which
are multiples of four. We compute conserved and thermodynamics quantities of
the black brane solutions and show that the expression of the electric field
does not depend on the dimension. Also, we obtain a Smarr-type formula and show
that these conserved and thermodynamic quantities of black branes satisfy the
first law of thermodynamics. Finally, we study the phase behavior of the
rotating black branes and show that there is no Hawking--Page phase transition
in spite of conformally invariant Maxwell field.Comment: 13 pages, one figur
Blood pressure and risk of venous thromboembolism: a cohort analysis of 5.5 million UK adults and Mendelian randomization studies
\ua9 The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology. Aims Evidence for the effect of elevated blood pressure (BP) on the risk of venous thromboembolism (VTE) has been conflicting. We sought to assess the association between systolic BP and the risk of VTE. Methods and results Three complementary studies comprising an observational cohort analysis, a one-sample and two-sample Mendelian randomization were conducted using data from 5 588 280 patients registered in the Clinical Practice Research Datalink (CPRD) dataset and 432 173 UK Biobank participants with valid genetic data. Summary statistics of International Network on Venous Thrombosis genome-wide association meta-analysis was used for two-sample Mendelian randomization. The primary outcome was the first occurrence of VTE event, identified from hospital discharge reports, death registers, and/or primary care records. In the CPRD cohort, 104 017(1.9%) patients had a first diagnosis of VTE during the 9.6-year follow-up. Each 20 mmHg increase in systolic BP was associated with a 7% lower risk of VTE [hazard ratio: 0.93, 95% confidence interval (CI): (0.92â0.94)]. Statistically significant interactions were found for sex and body mass index, but not for age and subtype of VTE (pulmonary embolism and deep venous thrombosis). Mendelian randomization studies provided strong evidence for the association between systolic BP and VTE, both in the one-sample [odds ratio (OR): 0.69, (95% CI: 0.57â0.83)] and two-sample analyses [OR: 0.80, 95% CI: (0.70â0.92)]. Conclusion We found an increased risk of VTE with lower BP, and this association was independently confirmed in two Mendelian randomization analyses. The benefits of BP reduction are likely to outweigh the harms in most patient groups, but in people with predisposing factors for VTE, further BP reduction should be made cautiously
Transgression forms and extensions of Chern-Simons gauge theories
A gauge invariant action principle, based on the idea of transgression forms,
is proposed. The action extends the Chern-Simons form by the addition of a
boundary term that makes the action gauge invariant (and not just
quasi-invariant). Interpreting the spacetime manifold as cobordant to another
one, the duplication of gauge fields in spacetime is avoided. The advantages of
this approach are particularly noticeable for the gravitation theory described
by a Chern-Simons lagrangian for the AdS group, in which case the action is
regularized and finite for black hole geometries in diverse situations. Black
hole thermodynamics is correctly reproduced using either a background field
approach or a background-independent setting, even in cases with asymptotically
nontrivial topologies. It is shown that the energy found from the thermodynamic
analysis agrees with the surface integral obtained by direct application of
Noether's theorem.Comment: 28 pages, no figures. Minor changes in the introduction, final
comments and reference
Quantum vortices in systems obeying a generalized exclusion principle
The paper deals with a planar particle system obeying a generalized exclusion
principle (EP) and governed, in the mean field approximation, by a nonlinear
Schroedinger equation. We show that the EP involves a mathematically simple and
physically transparent mechanism, which allows the genesis of quantum vortices
in the system. We obtain in a closed form the shape of the vortices and
investigate its main physical properties.
PACS numbers: 03.65.-w, 03.65.Ge, 05.45.YvComment: 7 pages, 4 figure
Push-over Analysis of Optimized Steel Frames
The traditional optimization methods are effective when dealing with small-scale problems. However, for large-scale problems, these methods fail to obtain optimal solutions, and after a long operation, several solutions are obtained. New methods, known as metaheuristics, have provided new implementations to be used in many applications. They have enabled the resolution of many complex industrial and technical problems. They have the merits of avoiding local optima and finding optimal solutions, due to their ease of understanding, flexibility, adaptation simplicity, and ability to get out of local optima traps. This article aims to model a 2D metal frame gantry with two spans and two levels already optimized by ROBOT Millennium software in order to show the effect of structural optimization in the pre-design phase and of obtaining its non-linear behavior by the pushover method. Three optimal dimensional configurations of this gantry were taken into account and the best was chosen, one which satisfied an adequate behavior in the non-linear domain while respecting the CM66 and Eurocode3 regulations
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