An in vitro evaluation of the efficacy of tedizolid: implications for the treatment of skin and soft tissue infections

Skin and soft tissue infections (SSTI) are among the most commonly occurring infections and evidence suggests that these are increasing world-wide. The aetiology is diverse, but Staphylococcus aureus predominate and these are often resistant to antimicrobials that were previously effective. Tedizolid is a new oxazolidinone-class antibacterial indicated for the treatment of adults with SSTI caused by Gram-positive pathogens, including S. aureus. The aim of this study was to evaluate the in vitro efficacy of tedizolid in comparison to other clinically used antibacterials against antibiotic sensitive- and resistant-staphylococci, grown in planktonic cultures and as biofilms reflecting the growth of the microorganism during episodes of SSTI. Against a panel of 66 clinical staphylococci, sensitivity testing revealed that a lower concentration of tedizolid was required to inhibit the growth of staphylococci compared to linezolid, vancomycin and daptomycin; with the tedizolid MIC being 8-fold (S. aureus) or 4-fold (S. epidermidis) below that obtained for linezolid. In addition, cfr+ linezolid-resistant strains remained fully susceptible to tedizolid. Against S. aureus biofilms, 10×MIC tedizolid was superior or comparable with 10×MIC comparator agents in activity, and superior to 10×MIC linezolid against those formed by S. epidermidis (65 vs. 33% reduction, respectively). Under flow-conditions both oxazolidinones at 10×MIC statistically out-performed vancomycin in their ability to reduce the viable cell count within a S. aureus biofilm with fewer the 12% of cells surviving compared to 63% of cells. In conclusion, tedizolid offers a realistic lower-dose alternative agent to treat staphylococcal SSTI, including infections caused by multi-drug resistant strains

Antagonisme de lactococcus garvieae vis-à-vis de Staphylococcus aureus : étude physiologique et transcriptomique des mécanismes

Among strategies aiming to control the growth of spoilage microorganisms in food, the biopreservation is based on the inhibitory capacities of other microorganisms and presents a considerable variety of opportunities. A good understanding of the molecular and physiologic mechanisms underlying the antagonism of the preservative microorganism against the spoilage bacterium is also required. This thesis aimed to characterize the antagonism of L. garvieae N201 dairy strain against S. aureus strains combining in vitro strategies: genomic, transcriptomic (targeted concerning S. aureus, global concerning L. garvieae) and phenotypic. The involvement of hydrogen peroxide (H2O2) produced by L. garvieae under high aeration was already known. Although H2O2 concentration was undetectable using spectrophotometry method, it was produced by L. garvieae under low aeration at sufficient concentration to induce S. aureus inhibition. L. garvieae H2O2 -synthesis genes (poxB, sodA) seemed constitutively expressed whatever the aeration level. L. garvieae H2O2-degradation (katA, sodA, ahpC / ahpF) genes were overexpressed under low aeration, suggesting their involvement in control of autogenous H2O2 level. In parallel, three other mechanisms may be involved in this antagonistic relationship: i) the repression of S. aureus stress-response genes (clpC, ctsR, dnaK) by L. garvieae and / or under high aeration, ii) the repression of S. aureus cell-division genes (mraZ, mraW and probably the dcw cluster) by L. garvieae, iii), the production by L. garvieae of an extracellular effector which has to be characterized. Additionally, L. garvieae can modulate the expression of S. aureus major virulence genes, repressing those coding for enterotoxins under low aeration. Thus, L. garvieae N201 turned out to be an interesting candidate for biopreservative applications. However, its safety for humans should be approved and its antagonism against S. aureus has to be investigated in food matrices. The data resulting from this work may be used to study other interactions between other valuable species and in other ecosystems.Parmi les stratégies visant à contrôler la croissance de microorganismes pathogènes dans un aliment, la biopréservation qui s’appuie sur l’utilisation des capacités inhibitrices d’autres microorganismes offre une grande diversité d’opportunités. Il est cependant nécessaire de comprendre les mécanismes moléculaires et physiologiques régissant l’antagonisme du microorganisme protecteur vis-à-vis de la bactérie indésirable. L’objectif de cette thèse était de caractériser l’antagonisme de L. garvieae N201, isolé de fromage, vis-à-vis de souches de S. aureus par des approches in vitro : génomique, transcriptomique (ciblée concernant S. aureus, globale concernant L. garvieae) et phénotypique. Un acteur avait déjà été identifié : le peroxyde d’hydrogène (H2O2) produit par L. garvieae sous un niveau d’aération élevé. Lors de ces travaux de thèse, il a été montré que le peroxyde d’hydrogène serait également produit par L. garvieae sous une faible aération en quantité faible (indétectable par spectrophotométrie) mais suffisante pour induire une inhibition de S. aureus. Les gènes de production du H2O2 de L. garvieae (poxB, sodA) seraient exprimés constitutivement quel que soit le niveau d’aération. Les gènes de dégradation du H2O2 (katA, sodA, ahpC / ahpF) seraient plutôt surexprimés sous une faible aération, suggérant leur rôle dans un mode de contrôle de la concentration en H2O2 autogène par L. garvieae. En parallèle, trois autres mécanismes potentiellement impliqués dans l’antagonisme ont été mis en évidence : i) la répression de gènes de réponse au stress (clpC, ctsR, dnaK) de S. aureus par L. garvieae et l’aération, ii) la répression de gènes de division cellulaire de S. aureus (mraZ, mraW, potentiellement le cluster dcw) par L. garvieae, iii) la production d’un effecteur extracellulaire par L. garvieae dont la nature reste à caractériser. Ajouté à cela, la présence de L. garvieae modulerait l’expression des principaux gènes de virulence de S. aureus, réprimant ceux codant pour les entérotoxines sous une faible aération. Ainsi, la souche L. garvieae N201 s’est révélée être une candidate intéressante comme agent de biopréservation. Cependant, son innocuité pour l’Homme devra être vérifiée et son antagonisme sur S. aureus devra être évalué en matrice alimentaire. Les données générées ainsi que la démarche développée pourront être utilisées afin d’étudier des interactions entre d’autres espèces d’intérêt et dans des écosystèmes différents

Approche stratigraphique des temps Gravettiens : l’éclairage aquitain

Le cadre spatio-temporel du gravettien est relativement large. En effet, la période gravettienne a sans doute duré plusieurs milliers d’années, au moins 6 000 “ années 14 C ” réparties de part et d’autre de 25 000 BP. Quant au territoire, il s’étale d’ouest en est sur toute l’Europe, ce qui pose la question des corrélations à grande distance. Dans ce travail, nous avons utilisé les moyens et méthodes de la stratigraphie pour tenter d’établir des liens chronologiques entre entités gravettiennes de l’ouest et du centre de l’Europe. Pour cela, nous nous sommes intéressés tout d’abord à la région Aquitaine et avons recherché des phénomènes environnementaux marqueurs. Ces derniers ont servi de points d’ancrage entre entités stratigraphiques ouest et centre européennes. Les datations physiques, prises en compte dans un deuxième temps, ne contredisent pas l’hypothèse de corrélation proposée. Elles conduisent néanmoins à mettre en garde contre l’utilisation d’une maille chronologique trop fine.The Gravettian was widely distributed in time and space. Temporally, it lasted at least 6000 radiocarbon years, centering on 25,000 BP. Spatially, it extended across all of Europe, posing the challenge of correlating assemblages across vast distances. We have used stratigraphic methods in an attempt to establish chronological ties between Gravettian assemblages in western and central Europe. Using the record from the Aquitaine, we have constructed a series of environmental horizon markers which serve as anchor points among stratigraphic entities in western and central Europe. Our hypothesized correlations are not contradicted by the radiocarbon dates available for the Gravettian. Those dates do, however, suggest that we should be wary of building highly precise links among far-flung Gravettian assemblages

Jules Verne 2.0, renewal of a large wind tunnel facility

International audienceThe paper aims at showing the evolution of methods to design a large wind tunnel. The current Jules Verne facility was designed with a scale model of the wind tunnel which enabled hot wire local wind speed measurements. The new facility is designed according a numerical modelling approach which parameters were validated by PIV measurements in the reduced scale physical model

The Aurignacian and Gravettian in northern Aquitaine: the contribution of Flageolet I

The site of Le Flageolet (Bézenac, Dordogne) contains two rock shelters excavated between 1966 and 1993. Le Flageolet I, the subject of this paper, opens to the west. On the bedrock, a first lithostratigraphic unit yielded three Aurignacian archaeostrata in a mass of very large blocks that collapsed before or during the earliest human occupations. A second overlying lithostratum contained at least six Gravettian archaeostrata. Due to the complexity of this archaeostratigraphy, we conceived and applied a method of excavation based on the three-dimensional recording of all artefacts with a maximum dimension over 1.5 cm, the use of artefact drawings at a scale of 1/5, and feature distributions, and the concomitant production of narrow vertical artefact projections along various frontal and sagittal axes. This method allowed for tight control over the definition and integrity of artefact levels. Analyses of the resulting assemblages show that the traditional regional cultural “markers” do not have the unambiguous chronological significance attributed to them in the past based on interpretations from excavations at La Ferrassie, Pataud, Caminade, and Roc-de-Combe. The large ungulate mammal biostratigraphy enabled us to chronologically position all the Aurignacian and Gravettian faunal assemblages from Le Flageolet I in relation to those from other Aquitaine sites; the faunal remains allow for the identification of particular environmental conditions that may be considered as “key events,” marking certain specific periods during the development of the Aurignacian-Gravettian sequence. Based on radiocarbon ages, several major Aquitaine sites, including Le Flageolet I, have been situated on the NGRIP climatic curve, thereby providing a chronological context independent of stone tool technology and typology. Based on all of this, a chronological-cultural model can be proposed that considers functional variation as an important influence on Aurignacian and Gravettian assemblage composition at Le Flageolet I and elsewhere. Since 1982, numerous publications on Le Flageolet I have contributed to a lively debate on the Western European Early Upper Palaeolithic. This paper addresses some recently expressed criticisms

L’Aurignacien et le Gravettien du nord de l’Aquitaine : la contribution du Flageolet I (Bézenac, Dordogne, France)

Le site du Flageolet (Bézenac, Dordogne) comporte deux abris sous roche fouillés entre 1966 et 1993. Le Flageolet I, objet de cet article, est orienté vers l’ouest. Sur le sol rocheux, une première unité lithostratigraphique a livré trois niveaux aurignaciens dans une structure d’accueil composée de blocs rocheux volumineux correspondant à l’effondrement de l’abri précédant ou contemporain des premières occupations. La seconde unité a livré plus de six niveaux gravettiens. En raison de la complexité de l’archéostratigraphie, nous avons conçu et appliqué une méthode de fouille basée sur l’enregistrement tridimensionnel de tous les vestiges lithiques et osseux de plus de 1,5 cm mis au jour, sur le relevé planimétrique au 1/5e des vestiges et des structures anthropiques ou naturelles et sur la réalisation concomitante de projections géométrales frontales et sagittales de faible épaisseur. Cette méthode a permis d’exercer un contrôle taphonomique sur l’homogénéité des nappes de vestiges. L’analyse des industries lithiques des ensembles aurignaco-gravettiens montre que les principaux marqueurs culturels n’ont pas la signification chronologique qui leur avait été attribuée précédemment sur la base de l’interprétation univoque des résultats des fouilles des abris de La Ferrassie, Pataud, Caminade et Roc de Combe. Les recherches fondées sur la biostratigraphie des grands mammifères ongulés ont permis de situer dans le temps les ensembles aurignaciens et gravettiens du Flageolet I relativement à ceux d’autres sites aquitains ; elles ont aussi conduit à la mise en évidence d’environnements particuliers qui peuvent être considérés comme des événements clés, marqueurs de certaines périodes au cours desquelles s’est développée la séquence aurignaco-gravettienne. À partir de leurs datations radiocarbones, plusieurs sites majeurs d’Aquitaine ont été situés relativement à la courbe NGRIP fournissant ainsi un cadre chronologique indépendant des données techno-typologiques. Sur cette base, une interprétation alternative au modèle chrono-culturel a été alors proposée faisant intervenir une variabilité d’ordre fonctionnel applicable au Flageolet I ainsi qu’à bien d’autres sites aurignaco-gravettiens. Depuis 1982, de nombreuses publications sur le Flageolet I ont contribué à un débat vigoureux sur les premières industries du Paléolithique supérieur de l’Europe de l’Ouest. Cet article répond également à quelques critiques récemment exprimées.The site of Le Flageolet (Bézenac, Dordogne) contains 2 rockshelters excavated between 1966 and 1993. Le Flageolet I, the subject of this paper, opens to the west. On the bedrock, a first lithostratigraphic unit yielded 3 Aurignacian archaeostrata within a mass of very large breakdown blocks that fell before or during the earliest human occupations. A second overlying lithostratum contained at least six Gravettian archaeostrata. Because of the complexity of this archaeostratigraphy, we conceived and applied a method of excavation based on three-dimensional recording of every artifact over 1,5 cm in maximum dimension, the use of scale drawings at 1/5 of artifact and feature distributions, and the concomitant production of narrow vertical artifact projections along various frontal and sagittal axes. This method allowed for fine control over the definition and integrity of artifact levels. Analyses of the resulting assemblages show that the traditional regional cultural “markers” do not have the unambiguous chronological significance attributed to them in the past based on interpretations from excavations at La Ferrassie, Pataud, Caminade, and Roc de Combe. Large ungulate mammal biostratigraphy allows chronological placement for all Aurignacian and Gravettian faunal assemblages from Le Flageolet I in relation to those from other Aquitaine sites ; the faunal remains permit the identification of particular environmental conditions that may be considered as “key events,” marking certain specific periods during the development of the Aurignacian-Gravettian sequence. Based on radiocarbon ages, several major Aquitaine sites, including Le Flageolet I, have been situated within the NGRIP climatic curve, thereby providing a chronological context independent of stone tool technology and typology. Based on all of this, a chronological-cultural model can be proposed that sees functional variation as an important influence on Aurignacian and Gravettian assemblage composition at Le Flageolet I and elsewhere. Since 1982, numerous publications on Le Flageolet I have contributed to a vigorous debate on the Western European Early Upper Paleolithic. This paper answers some recently expressed criticisms

Development of a preclinical model of donation after circulatory determination of death for translational application

BACKGROUND: Extracorporeal membranous oxygenation is proposed for abdominal organ procurement from donation after circulatory determination of death (DCD). In France, the national Agency of Biomedicine supervises the procurement of kidneys from DCD, specifying the durations of tolerated warm and cold ischemia. However, no study has determined the optimal conditions of this technique. The aim of this work was to develop a preclinical model of DCD using abdominal normothermic oxygenated recirculation (ANOR). In short, our objectives are to characterize the mechanisms involved during ANOR and its impact on abdominal organs. METHODS: We used Large White pigs weighing between 45 and 55 kg. After 30 minutes of potassium-induced cardiac arrest, the descending thoracic aorta was clamped and ANOR set up between the inferior vena cava and the abdominal aorta for 4 hours. Hemodynamic, respiratory and biochemical parameters were collected. Blood gasometry and biochemistry analysis were performed during the ANOR procedure. RESULTS: Six ANOR procedures were performed. The surgical procedure is described and intraoperative parameters and biological data are presented. Pump flow rates were between 2.5 and 3 l/min. Hemodynamic, respiratory, and biochemical objectives were achieved under reproducible conditions. Interestingly, animals remained hemodynamically stable following the targeted protocol. Arterial pH was controlled, and natremia and renal function remained stable 4 hours after the procedure was started. Decreased hemoglobin and serum proteins levels, concomitant with increased lactate dehydrogenase activity, were observed as a consequence of the surgery. The serum potassium level was increased, owing to the extracorporeal circulation circuit. CONCLUSIONS: Our ANOR model is the closest to clinical conditions reported in the literature and will allow the study of the systemic and abdominal organ impact of this technique. The translational relevance of the pig will permit the determination of new biomarkers and protocols to improve DCD donor management

Matrix Isolation Infrared Spectroscopic and Theoretical Study of the Interaction of Water with Dimethyl Methylphosphonate

Matrix isolation infrared spectroscopy has been combined with theoretical calculations for the characterization of the 1:1 hydrogen-bonded complex between H2O and dimethyl methylphosphonate (DMMP). The symmetric O-H stretching mode was observed to shift 203 cm-1 to lower energy upon hydrogen bond formation, while a 32 cm-1 blue shift was noted for the H-O-H bending mode of the H2O subunit in the complex. These values compare extremely well with the (unscaled) shifts of -203 and +32 cm-1, respectively, that were calculated theoretically at the MP2/6-31+G** level. Additional perturbed modes of the DMMP subunit were observed, shifted relative to the parent band position. The greatest perturbation was to the P=O stretching mode near 1270 cm-1, where a shift of -17 cm-1 was observed (-21 cm-1 calculated theoretically). This suggests that the site of hydrogen bonding in the complex is at the P=O group, in agreement with theoretical calculations. The binding energy ΔE° for the 1:1 complex was calculated to be -7.7 kcal/mol