Antibiotic Transport in Resistant Bacteria: Synchrotron UV Fluorescence Microscopy to Determine Antibiotic Accumulation with Single Cell Resolution

A molecular definition of the mechanism conferring bacterial multidrug resistance is clinically crucial and today methods for quantitative determination of the uptake of antimicrobial agents with single cell resolution are missing. Using the naturally occurring fluorescence of antibacterial agents after deep ultraviolet (DUV) excitation, we developed a method to non-invasively monitor the quinolones uptake in single bacteria. Our approach is based on a DUV fluorescence microscope coupled to a synchrotron beamline providing tuneable excitation from 200 to 600 nm. A full spectrum was acquired at each pixel of the image, to study the DUV excited fluorescence emitted from quinolones within single bacteria. Measuring spectra allowed us to separate the antibiotic fluorescence from the autofluorescence contribution. By performing spectroscopic analysis, the quantification of the antibiotic signal was possible. To our knowledge, this is the first time that the intracellular accumulation of a clinical antibitiotic could be determined and discussed in relation with the level of drug susceptibility for a multiresistant strain. This method is especially important to follow the behavior of quinolone molecules at individual cell level, to quantify the intracellular concentration of the antibiotic and develop new strategies to combat the dissemination of MDR-bacteria. In addition, this original approach also indicates the heterogeneity of bacterial population when the same strain is under environmental stress like antibiotic attack

Wood transverse fracture analysis at the mesoscopic scale

The present study is an analysis of wood fracture behavior at the mesoscopic scale (i.e. the scale of growth ring). Radial TR crack growth mechanisms are complex and involve several events such as secondary cracks creation while cracks extend from one growth ring to another. Crack tip strain field of radial TR crack is measured by digital image correlation in order to better understand these phenomena. A numerical model for wood fracture has been conducted and a transverse model of spruce wood has been implemented. The simulation is realized by Material Point Method, a meshless method that discretizes material bodies into a collection of material points or particles. This promising tool improves the understanding of transverse fracture in spruce wood and can easily be used in further studies

Détermination expérimentale du facteur d'intensité des contraintes sous sollicitation dynamique

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Epidemiological surveillance of mycoplasmas belonging to the 'Mycoplasma mycoides' cluster: is DGGE fingerprinting of 16S rRNA genes suitable?

International audienceAIMS: The analysis by Denaturing Gradient Gel Electrophoresis (DGGE) of the PCR-amplified V3 region of 16S rRNA gene was previously shown to detect and differentiate a large number of human and animal mycoplasmas. In this study, we further assessed the suitability of the technique for epidemiological surveillance of mycoplasmas belonging to the 'Mycoplasma mycoides' cluster, a phylogenetic group that includes major ruminant pathogens. METHODS AND RESULTS: The V3 region of 16S rRNA genes from approx. 50 field strains was amplified and analysed by DGGE. Detection and identification results were compared with the ones obtained by antigenic testing and sequence analysis. CONCLUSIONS: The DGGE technique is robust and valuable as a first-line test, but the patterns obtained for strains belonging to the 'M. mycoides' cluster were too variable within a taxon and in contrast too conserved between taxa to allow an unequivocal identification of isolates without further analysis. SIGNIFICANCE AND IMPACT OF THE STUDY: Issues raised by the quest for a single universal test able to detect and identify any mycoplasma in one clinical sample are thoroughly documented

Uses of Usumacinta River sediments as a sustainable resource for unpaved roads: an experimental study on a full-scale pilot unit

Purpose: Transportation is a key factor for economic growth and poverty reduction because it improves access to services and opportunities for rural communities. Unpaved roads, however, still represent 80% of the global road network. The state of Tabasco, Mexico, is not an exception.Materials and methods: Geotechnical identifications of raw and lime-treated sediments are performed. A methodology is developed to reproduce a soil-model close to the raw sediment's properties. The reconstituted soil-model is used for full-scale testing including CBR indexes determination, cyclic vertical plate testing and horizontal traffic loads tests.Results: The rutting generated from the cyclic plate and traffic load tests, on both the untreated and the lime-treated soil-model, are compared. The lime treatment appears to improve the properties of both the soil-model and the sediments.Conclusions: The findings give promising perspectives regarding the use of Usumacinta River sediments for the construction of unpaved roads

Stress and strain state in the segmental linings during mechanized tunnelling

The application of the mechanized tunnelling has been extended in recent years. There are at present different approaches that are used in the design of segmental tunnel linings supported in mechanized tunnels. Even though segmental lining is utilized for mechanized tunnels, its behaviour is still quite unclear under in situ stress and there is a lack of data regarding the distribution of stresses inside segmental linings. So far no single effective calculation method exists for segmental lining design. The lack of clear solutions makes the use of segmental lining to be more expensive due to the adoption of greater safety factors. Therefore, a particular attention must be given in order to obtain data from monitored tunnels which permits to validate design methods. In this study, strain measurements, which were conducted during the construction of twin tunnels in the Bologna-Florence railway line, have been presented. The behaviour of segmental lining during the excavation and the influence of a new tunnel excavation on an existing tunnel have been shown through the measured data. The data are then compared with the results obtained with Einstein and Schwartz's method and Duddeck and Erdmann's method, which permits to highlight the fact that the two analytical methods underestimate structural forces induced in the segmental lining and then must be used with caution

Novel synthetic bis-indolic derivatives with antistaphylococcal activity, including against MRSA and VISA strains

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A plant trait-based response-and-effect framework to assess vineyard inter-row soil management

International audienceBiodiversity impacts ecosystem properties and the ecosystem services provided by those ecosystems. As a result, promoting plant diversity in agricultural systems has been a key issue in agriculture over recent years. In this context, weeds have an important role in maintaining field biodiversity, when it is balanced with their potential negative impact on crop production. Functional trait diversity, rather than the diversity of species per se, is a facet of biodiversity most directly related to species and community responses to management practices, with subsequent consequences for ecosystem services. Trait-based approaches, originally developed in the field of comparative ecology, allowed the description of weed species responses to management practices in annual crop systems. Here, we aimed to extend the trait-based approach to the spontaneous vegetation of vineyards. First, we propose a brief summary of current knowledge about weed communities in vineyards. Then we show how the relationships between management practices, weeds and grape vines can be translated into a response-effect framework: soil management practices (tillage, cover crops, spontaneous vegetation) can be considered as environmental filters that determine the composition and structure of vegetation, which, in turn, modify grapevine growth conditions in the vineyard. Finally, we tested this framework in a Mediterranean vineyard where, for 2 years, we characterized the responses of different components of weed communities (taxonomic and functional composition) in three inter-row management practices (tillage, cover crops and mowing spontaneous vegetation) and their effects on several grapevine processes (vine yield, vine leaf water potential and assimilable nitrogen in must)