Commensal bacteria augment Staphylococcus aureus infection by inactivation of phagocyte-derived reactive oxygen species

Staphylococcus aureus is a human commensal organism and opportunist pathogen, causing potentially fatal disease. The presence of non-pathogenic microflora or their components, at the point of infection, dramatically increases S. aureus pathogenicity, a process termed augmentation. Augmentation is associated with macrophage interaction but by a hitherto unknown mechanism. Here, we demonstrate a breadth of cross-kingdom microorganisms can augment S. aureus disease and that pathogenesis of Enterococcus faecalis can also be augmented. Co-administration of augmenting material also forms an efficacious vaccine model for S. aureus. In vitro, augmenting material protects S. aureus directly from reactive oxygen species (ROS), which correlates with in vivo studies where augmentation restores full virulence to the ROS-susceptible, attenuated mutant katA ahpC. At the cellular level, augmentation increases bacterial survival within macrophages via amelioration of ROS, leading to proliferation and escape. We have defined the molecular basis for augmentation that represents an important aspect of the initiation of infection

Iterative computation of modal sensitivities

The computation of frequency and mode shape sensitivities with respect to design parameters is essential to many, structural optimization and finite element updating algorithms. Approximating the gradients may lead to poor estimates and loss of convergence, but on the other hand the cost of exact methods, such as Nelson's (Nelson, R.,, "Simplified Calculations of Eigenvector Derivatives," A1AA Journal, Vol. 14, No. 9,1976, pp. 1201-1205), is often not acceptable for industrial-size models. The present study thus analyses existing approximation methods, suggests a first-order improvement of Fox and Kapoor's modal basis (Fox, R., and Kapoor, M., "Rate of Change of Eigenvalues and Eigenvectors"' A1AA Journal, Vol. 6, No. 12, 1968, pp. 2426-242, 9) and proposes a residual iteration technique allowing accurate computations of modeshape sensitivities. An engine cover model and a model of the Ariane 5 main cryogenic stage are used to analyze, for models of realistic sizes, the accuracy and computational costs of the proposed methods

An efficient algorithm for the RCS modulation prediction from jet inlet-engines

Communication to : IEEE AP-S international symposium and USNC/URSI national radio science meeting, Orlando (USA), July 11-16, 1999Available from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1999 n.99 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

A numerical scheme combining FEM, MoM and modal techniques for large inlet scattering

Communication to : URSI 1998 international symposium on electromagnetic theory, Thessaloniki (Greece), May 25-28, 1998Available from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1998 n.65 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

A partial metabolic pathway enables group b streptococcus to overcome quinone deficiency in a host bacterial community.

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