Staphylococcus aureus infective endocarditis versus bacteremia strains: Subtle genetic differences at stake

AbstractInfective endocarditis (IE)(1) is a severe condition complicating 10–25% of Staphylococcus aureus bacteremia. Although host-related IE risk factors have been identified, the involvement of bacterial features in IE complication is still unclear. We characterized strictly defined IE and bacteremia isolates and searched for discriminant features. S. aureus isolates causing community-acquired, definite native-valve IE (n=72) and bacteremia (n=54) were collected prospectively as part of a French multicenter cohort. Phenotypic traits previously reported or hypothesized to be involved in staphylococcal IE pathogenesis were tested. In parallel, the genotypic profiles of all isolates, obtained by microarray, were analyzed by discriminant analysis of principal components (DAPC)(2). No significant difference was observed between IE and bacteremia strains, regarding either phenotypic or genotypic univariate analyses. However, the multivariate statistical tool DAPC, applied on microarray data, segregated IE and bacteremia isolates: IE isolates were correctly reassigned as such in 80.6% of the cases (C-statistic 0.83, P<0.001). The performance of this model was confirmed with an independent French collection IE and bacteremia isolates (78.8% reassignment, C-statistic 0.65, P<0.01). Finally, a simple linear discriminant function based on a subset of 8 genetic markers retained valuable performance both in study collection (86.1%, P<0.001) and in the independent validation collection (81.8%, P<0.01). We here show that community-acquired IE and bacteremia S. aureus isolates are genetically distinct based on subtle combinations of genetic markers. This finding provides the proof of concept that bacterial characteristics may contribute to the occurrence of IE in patients with S. aureus bacteremia

Influence des facteurs sociaux sur le stade de découverte d une infection par le VIH et sur la réponse au traitement antirétroviral (étude rétrospective entre 2005 et 2007 dans un hôpital du nord-ouest parisien)

PARIS7-Xavier Bichat (751182101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Proof-Guided Test Selection from First-Order Specifications with Equality

International audienceThis paper deals with test case selection from axiomatic speci cations whose axioms are quanti er-free rst-order formulas with equality. We rst prove the existence of an ideal exhaustive test set to start the selection from. We then propose an extension of the test selection method called axiom unfolding, originally de ned for algebraic speci cations, to quanti er-free rst-order speci cations with equality. This method basically consists of a case analysis of the property under test (the test purpose) according to the speci cation axioms. It is based on a proof search for the di erent instances of the test purpose, thus allowing a sound and complete coverage of this property. The generalisation we propose allows to deal with any kind of predicate (not only equality) and with any form of axiom and test purpose (not only equations or Horn clauses). Moreover, it improves our previous works with e ciently dealing with the equality predicate, thanks to the paramodulation rule

Test Selection Criteria for Quantifier-Free First-Order Specifications

This paper deals with test case selection from axiomatic specifications whose axioms are quantifier-free first-order formulae. Test cases are modeled as ground formulae and any specification has an exhaustive test data set whose successful submission means correctness, provided that the software under verification can be modeled as a firstorder structure over the same signature. As it has already been done for positive conditional equational specifications, we derive test cases from selection criteria based on axiom coverage. Our selection criteria allows us to select test cases by iteratively unfolding an initial target test purpose, given as a formula. The initial reference test set is iteratively split into successive subsets. Each subset of test cases is defined by constraints which are increasingly introduced by the unfolding procedure to ensure an appropriate matching between the current test purpose under unfolding and specification axioms. Our unfolding procedure is sound (no test is added) and complete (no test is lost) with respect to the starting test purpose. It is exemplified on a simple example

A Temporal Logic for Input Output Symbolic Transition Systems

International audienceIn this paper, we present a temporal logic called F whose interpretation is over Input Output Symbolic Transition Systems (IOSTS). IOSTS extend transition systems to communications and data in order to tackle communications with system environment. F is then defined as an extension of temporal logic CTL* (a temporal logic which mixes together the features of Linear Temporal Logic (LTL) and Computational Temporal Logic (CTL)). Three basic properties are established on F: adequacy and preservation of properties along synchronized product and IOSTS refinement

Viscoplastic constitutive equations of combustion chamber materials including cyclic hardening and dynamic strain aging

International audienceCobalt-base and nickel-base superalloys for aircraft engine combustion chamber applications (e.g. Haynes 188, Haynes 230, Hastelloy X) show a complex viscoplastic behavior. In a large temperature range from 300 to 800 °C, an important cyclic hardening with memory effects combined with a negative strain rate sensitivity are observed. This behavior can be related to the dynamic strain aging phenomenon. The present contribution aims at proposing a set of constitutive equations that are able to predict those experimental observations. A classical unified viscoplastic framework is coupled with a physically motivated macroscopic modeling of dynamic strain aging initially introduced by McCormick and Kubin, Estrin. The complete model has been identified on original multilevel and multirate cyclic experiments and cyclic relaxation experiments on the Haynes 188 alloy. The predictive abilities of the model are demonstrated by simulations of a large set of experimental data including fatigue tests from the literature