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Recovery of severely deformed ferrite was followed in situ by High Energy X Ray Diffraction during heating and isothermal holding experiments. Dislocation densities during annealing were determined by a modified Williamson Hall method. The deduced recovery kinetics was compared to post-mortem hardness measurements. A temperature dependent saturation of recovery was exhibited during holding. Dislocation density drop and saturation behavior cannot be reproduced simultaneously by the classical physically based models.

International audience; Knowledge of phase transformation kinetics is a key point in designing steel grades, in particular modern high-performance grades, highly sought-after in energy and transportation applications. The design space for these grades is highly multi-dimensional given the numerous potential alloying elements. The characterization techniques that are usually relied on to assess transformation kinetics, such as metallography or dilatometry, are highly time consuming, due to their limitation to either a single transformation time or a single composition per experiment. The high-throughput approach showcased here overcomes those limitations by combining compositionally graded samples with time-and space-resolved in situ Xray diffraction, yielding full kinetic records over a range of compositions in a single run. Its application to low-alloy steel required addressing specific challenges related to the reactivity and thermodynamics of the material. The transformation of austenite into ferrite was chosen to illustrate its benefits. Using the rich resulting database, the transformation mechanism was examined quasi-continuously across sections of the composition space. Neither the paraequilibrium, nor the local equilibrium with negligible partitioning model, nor a transition from the former to the latter is applicable over the whole range of investigated conditions. Instead, the observed kinetics were explained by accounting for the solute drag exerted on the mobile interface. This work is a major contribution in accelerating the design of future low-alloy steel grades, involving the transformation of austenite into ferrite or any other transformation to which the present high-throughput methodology can be adapted.

International audience; The aim of this paper is to investigate the effective properties of Fe–TiB2 composites obtained after hot or cold rolling. The elastic moduli of both hot and cold rolled composites are measured experimentally using several methods. Microstructure analyses based on SEM observations are performed to characterize the distribution of particles and cracks, and are then used to generate 3D representative microstructures using the RSA method. This allows the numerical determination of the overall elastic behavior of Fe–TiB2 composites using full-field FFT-based simulations. In addition, Young’s moduli of the hot rolled Fe–TiB2 composites are also determined analytically using the mean-field homogenization scheme of Mori–Tanaka. The elastic properties determined experimentally, analytically and numerically are in a good agreement. Overall, a significant improvement of the specific stiffness in comparison to standard steels is achieved irrespective of the processing conditions

The evolution of the dislocation densities in martensite and in austenite during the quench of a low-carbon (0.215 wt% C) steel is investigated in situ by the mean of a High Energy X-Ray Diffraction experiment on a synchrotron beamline. The line configuration offers an excellent time resolution well adapted to the studied martensitic transformation kinetics. The mean density of dislocations in martensite increases as the transformation proceeds confirming that dislocations are not homogeneously distributed between the laths in agreement with some recent post-mortem observations. The resulting spatial distribution of dislocations and the associated strain-hardening support the views assuming that lath martensite is a heterogeneous microstructure and behaves as a “multiphase” aggregate. In austenite, the increase in dislocation densities is even more significant meaning that austenite in martensite is also a hard phase, contradicting some recent theories attributing to films of retained austenite a major role in the plasticity of martensite.

The disk diffusion test is very popular but for anaerobes the main pitfalls arise from the significant variation of diameters for an individual MIC and the weak correlation observed between the MIC's values and diameters zone that generates many major and very major errors. Aims of the study without any change in the methodology and revisiting only new diameter breakpoints, we try to improve the previous French recommendations and therefore decrease number of errors by introducing recent EUCAST concepts such as ECOFF and ATU Zone. Method MIC determination by agar dilution was done on 100 anaerobes against 6 antibiotics. Clinical categorization was based on EUCAST Breakpoints. Disk-diffusion method was realized on the same Brucella blood agar incubated in an anaerobic chamber. 550 categorizations by both methods could be done as amoxicillin was not tested on the 50 B. fragilis group. As anaerobic infections are severe and treated by antibiotics at higher dosage, we focus on resistance breakpoint to avoid mainly very major errors (VME). Distribution of inhibition zones for each MIC allow us to fix the zone diameter breakpoints. These results were matched to a large data on distribution of zone diameters for each antibiotic collected from two French hospitals from 1990 to 2005. As example for metronidazole and the B. fragilis group, we calculated the cut-off diameter (15 mm) from a wild type population, at a time when there was no resistance to this antibiotic and observed that it was identical to the diameter breakpoint for susceptibility. Results For an individual value of MIC, the distribution of diameters is wider for anaerobes especially for clindamycin and metronidazole. Using a 15 mm breakpoint for these two antibiotics limits dramatically the number of very major errors but slowly increases the number of major errors that could be overcome by MIC determination if inhibition zone is less than 15 mm. ATU zones (Area of technical uncertainty) were introduced for amoxicillin-clavulanate (17–20 mm), piperacillin-tazobactam (17–20 mm), imipenem (18–23 mm). Categorization inside the ATU requires MIC determination. Finally, out of 550 determinations, VME were observed in 1.45% of cases, an acceptable rate. Conclusion in combination with introduction of ATU zones disk diffusion method allows to detect resistant strains with little MIC determinations and very major errors.

International audience; The thermo-mechanical properties of a ferritic-steel-based metal matrix composite reinforced with titanium diboride (TiB 2) particles were studied using synchrotron X-ray diffraction. The samples were subjected to in situ heat treatment to investigate the effect of the mismatch in the coefficient of thermal expansion between the matrix and reinforcement. In addition, in situ tensile tests were performed to examine the load partitioning in the composite. Load transfer from the ferritic matrix to the TiB 2 particles was observed at the onset of plasticity in the matrix.

Cephalosporinases, which are naturally present in some enterobacterial species, can be mobilized by transposons, migrate to plasmids, and spread into other species such as Escherichia coli. The aim of this study was to characterize genes responsible for the production of extended-spectrum β-lactamases (ESBL) in E. coli isolates from urinary origin isolated in two hospitals in Senegal. Thus, a fortuitous discovery of plasmidic cephalosporinase in two isolates was noted. One of the isolates produced dha-1 associated with ESBL CTX-M-14, the other produced cmy-2, ESBL CTXM-15, tem-1 penicillinase, and oxa-1. This confirms the circulation of multidrug-resistant bacteria producing plasmidic cephalosporinase in Senegal. However, a large study is needed to better understand the prevalence and the nature of the genes involved.

Objectives To decrease the incidence of early-onset group B streptococcal (GBS) disease, a culture-based screening of all pregnant women at 35–37 weeks is recommended. This gold standard test requires 24–72 hours culture. This delay precludes its use for intrapartum screening. This study assesses a new immunoassay, the DIMA test, for identifying GBS-positive patients in the labor ward. Materials and methods This was a prospective observational study of 195 pregnant women presenting with full-term labor at a single site in France between June and August 2012. We assessed the diagnostic accuracy of intrapartum DIMA testing as compared to intrapartum GBS culture and prenatal screening at 35–38 weeks. Results The DIMA test sensitivity and specificity were 57.1% and 83.2%, respectively, as compared to 42.9% and 97% for prenatal culture screening. Conclusion The DIMA test assay is a rapid and inexpensive test for the detection of maternal GBS colonization in the labor ward. Its sensitivity is higher than antepartum culture but its specificity is lower. Its performance was inferior to that reported for rapid polymerase chain reaction assays.

International audience; The MastA (R) D68C test is a phenotypical test that allows the detection of extended-spectrum beta-lactamase (ESBL) production, even in AmpC-producing Enterobacteriaceae. We assessed its detection accuracy against a large collection of 106 Enterobacteriaceae isolates producing a wide diversity of well-characterized beta-lactamases (53 ESBL producers, 25 Amp. producers, seven AmpC and ESBL producers, five carbapenemase producers, three carbapenemase and ESBL producers, one AmpC, carbapenemase, and ESBL producer, three TEM-1 producers, three SHV-1 producers, three OXA-1 producers, and one hyperOXY producer, ATCC 35218, ATCC 25922 [a beta-lactamase-negative control strain]). The results were compared with those of the double disk test and the Clinical and Laboratory Standards Institute (CLSI) confirmatory test for the detection of ESBL. The sensitivity was 90.6 % for the synergy test, 87.5 % for the CLSI method, and only 73.1 % for D68C, which, however, reached 92.1 % if the strains for which supplementary investigations were recommended and the complex mutant TEM (CMT)-producing strains were excluded versus 94.1 % and 88.2 % for the other methods. The specificity was 90.2 % for the synergy test and 100 % for the CLSI method and D68C. D68C was also efficient in detecting AmpC-overproducing strains (sensitivity = 97 %, specificity = 95.9 %): among the 74 strains belonging to natural AmpC-producing species, the sensitivity and specificity were 100 and 94.8 %, respectively. The MastA (R) D68C-test is a promising method that is easy to perform for the detection of current ESBLs and could also be useful for the detection of plasmid-encoded AmpC enzymes (sensitivity = 100 %).

International audience; The elastic distortions nearby the two emerging points of a straight inclined dislocation located in an elastically anisotropic thin foil are expressed with the aid of the integral formalism [D.M. Barnett and J. Lothe, Phys. Norv. 7 (1973) p.13], an approach complementary to that of the Eshelby's sextic formalism. They are included in the calculation of the intensities of diffracted beams in transmission electron microscopy to produce theoretical images, a well known procedure when elastic free surface relaxation is ignored. Examples of theoretical images point out some contrast differences between images calculated with the assumptions of isotropic and anisotropic crystals. These calculations can be simplified for a dislocation normal to the surface and a line direction parallel to a two-fold axis.

Pseudomonas luteola (formerly classified as CDC group Ve-1 and named Chryseomonas luteola ) is an unusual pathogen implicated in rare but serious infections in humans. A novel β-lactamase gene, bla LUT-1 , was cloned from the whole-cell DNA of the P. luteola clinical isolate LAM, which had a weak narrow-spectrum β-lactam-resistant phenotype, and expressed in Escherichia coli . This gene encoded LUT-1, a 296-amino-acid Ambler class A β-lactamase with a pI of 6 and a theoretical molecular mass of 28.9 kDa. The catalytic efficiency of this enzyme was higher for cephalothin, cefuroxime, and cefotaxime than for penicillins. It was found to be 49% to 59% identical to other Ambler class A β-lactamases from Burkholderia sp. (PenA to PenL), Ralstonia eutropha (REUT), Citrobacter sedlakii (SED-1), Serratia fonticola (FONA and SFC-1), Klebsiella sp. (KPC and OXY), and CTX-M extended-spectrum β-lactamases. No gene homologous to the regulatory ampR genes of class A β-lactamases was found in the vicinity of the bla LUT-1 gene. The entire bla LUT-1 coding region was amplified by PCR and sequenced in five other genetically unrelated P. luteola strains (including the P. luteola type strain). A new variant of bla LUT-1 was found for each strain. These genes (named bla LUT-2 to bla LUT-6 ) had nucleotide sequences 98.1 to 99.5% identical to that of bla LUT-1 and differing from this gene by two to four nonsynonymous single nucleotide polymorphisms. The bla LUT gene was located on a 700- to 800-kb chromosomal I-CeuI fragment, the precise size of this fragment depending on the P. luteola strain.

This paper describes an outbreak of Pseudomonas aeruginosa and Pseudomonas putida that occurred in an oncohaematology paediatric unit between January and April 2005. Eight children had nosocomial infections due to P. aeruginosa (N=5) or P. putida (N=3), which were recovered from central venous catheter blood cultures (N=4), the catheter exit site alone (N=2), or the catheter exit site and the catheter tip (N=2). Subsequent investigation showed that contaminated water outlets represented the possible source of spread. Studies of nursing and environmental cleaning practices revealed two modes of catheter contamination. A reduction in the size of the catheter dressing at the exit site gave less protective cover during showers, and a detergent-disinfectant diluted with tap water had contaminated perfusion bottles. Repetitive intergenic consensus polymerase chain reaction indicated two discrete patterns for P. aeruginosa and one for P. putida. The water network was chlorinated, and disposable seven-day filters were fitted on all taps and showers. Due to the deleterious effects of chlorination on the water network and the cost of the weekly filter change, a water loop producing microbiologically controlled water was installed. In addition, the concentration of the detergent-disinfectant was increased and refillable sprayers were replaced with ready-to-use detergent-disinfectant solution for high-risk areas. Following these measures, no Pseudomonas spp. have since been isolated in clinical or environmental samples from the ward.

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