Cross-talk mediated by Rgg-peptide cell-cell communication systems from Streptococcus salivarius.

The oral cavity is presumably one of the most challenging environments considering the tremendous and diversified bacterial community that struggle to thrive coupled to constant and multiple external changes. Remarkably, the commensal Streptoccoccus salivarius species is one of the prime colonizers of oral mucosal surfaces that remains predominant in the buccal cavity throughout the human lifespan. Furthermore, several lines of evidence argue in favour of a dampening effect of S. salivarius on its closely-related pathogen and dental caries agent S. mutans. In all likelihood, S. salivarius cells are able to sense the physiological state of S. mutans population in order to provide the ad hoc response and endeavour to restrain the spreading of its competitor. Our preliminary results suggest that S. salivarius is able to recognize a signalling peptide excreted by S. mutans, via the orthologous ComRS cell-cell communication system involved in DNA transformation and production of bacteriocins. We are deciphering S. salivarius molecular mechanisms that allow intra- and inter-species cross-talk in the framework of streptococcal population dynamics. A newly discovered family of pheromone-responsive transcriptional regulators called Rgg is of particular interest as it encompasses the ComRS system. We systematically deleted rgg genes and assessed the role of Rgg proteins for various phenotypes such as natural DNA transformation, predation through bacteriocin production, biofilm formation, and global fitness. Currently, we are assessing the impact of cross-talk between Rgg members in a single S. salivarius strain. Future work will include the investigation of inter-species cross-talk in mixed-species biofilm of S. salivarius and S. mutans strains for a given Rgg system, starting with the better characterized ComRS system

The CovRS Environmental Sensor Directly Controls the ComRS Signaling System To Orchestrate Competence Bimodality in Salivarius Streptococci

In bacteria, phenotypic heterogeneity in an isogenic population compensates for the lack of genetic diversity and allows concomitant multiple survival strategies when choosing only one is too risky. This powerful tactic is exploited for competence development in streptococci where only a subset of the community triggers the pheromone signaling system ComR-ComS, resulting in a bimodal activation. However, the regulatory cascade and the underlying mechanisms of this puzzling behavior remained partially understood. Here, we show that CovRS, a well-described virulence regulatory system in pathogenic streptococci, directly controls the ComRS system to generate bimodality in the gut commensal Streptococcus salivarius and the closely related species Streptococcus thermophilus. Using single-cell analysis of fluorescent reporter strains together with regulatory mutants, we revealed that the intracellular concentration of ComR determines the proportion of competent cells in the population. We also showed that this bimodal activation requires a functional positive-feedback loop acting on ComS production, as well as its exportation and reinternalization via dedicated permeases. As the intracellular ComR concentration is critical in this process, we hypothesized that an environmental sensor could control its abundance. We systematically inactivated all two-component systems and identified CovRS as a direct repression system of comR expression. Notably, we showed that the system transduces its negative regulation through CovR binding to multiple sites in the comR promoter region. Since CovRS integrates environmental stimuli, we suggest that it is the missing piece of the puzzle that connects environmental conditions to (bimodal) competence activation in salivarius streptococci

Expanding natural transformation to improve beneficial lactic acid bacteria.

Nowadays, the growing human population exacerbates the need for sustainable resources. Inspiration and achievements in nutrient production or human/animal health might emanate from microorganisms and their adaptive strategies. Here, we exemplify the benefits of lactic acid bacteria (LAB) for numerous biotechnological applications and showcase their natural transformability as a fast and robust method to hereditarily influence their phenotype/traits in fundamental and applied research contexts. We described the biogenesis of the transformation machinery and we analyzed the genome of hundreds of LAB strains exploitable for human needs to predict their transformation capabilities. Finally, we provide a stepwise rational path to stimulate and optimize natural transformation with standard and synthetic biology techniques. A comprehensive understanding of the molecular mechanisms driving natural transformation will facilitate and accelerate the improvement of bacteria with properties that serve broad societal interests

Prognostic significance of imaging contrast enhancement for WHO grade II gliomas

In this study, we investigated the prognostic value of MRI contrast enhancement (CE) at the time of histological diagnosis specifically in a selected population of WHO grade II gliomas. We reviewed 927 histologically proven WHO grade II gliomas for which contrast-enhanced MR images were available at the time of histological diagnosis. CE patterns were classified into three categories: “patchy and faint,” “nodular-like,” and “ring-like.” CE progression over time was recorded before oncological treatment on successive MR images, when available. CE was present in 143 cases (15.9%), with 93 patchy and faint, 50 nodular-like, and no ring-like patterns. CE areas were time progressive before oncological treatment in 35 of the 56 available cases (62.5%). Regardless of its pattern, the presence of CE was not significantly associated with a worsened prognosis (p = 0.415) by univariate analysis. Only the nodular-like pattern of CE (p < 0.01) and the time-progressive CE (p < 0.001) in the available subgroup proved to be statistically associated with survival since first oncological treatment. The present results show the necessity, in cases of WHO grade II gliomas, to study CE at the time of histological diagnosis and, whenever possible, to follow its progression over time before oncological treatment. Nodular-like CE and time- progressive CE are associated with a worsened prognosis, both suggesting malignant transformation, even though histopathological examination cannot initially disclose signs of malignancy in those areas

Recommandations sur les alimentations standard et thérapeutiques chez l’adulte en établissements de santé

International audienceObjectifsL’alimentation à l’hôpital est soumise à de multiples contraintes de fabrication, organisationnelle, sanitaire, écologique, qui influent sur le plateau repas proposé au patient. L’addition d’un ou plusieurs régimes peut ajouter à la complexité et contribuer à sa non-consommation et augmente les risques de dénutrition. L’élaboration de recommandations sur l’alimentation et les régimes à l’hôpital est d’un enjeu majeur.MéthodesUn groupe de pilotage constitué à parité par des médecins et diététiciens de l’Association Française des Diététiciens Nutritionnistes (AFDN) et de la Société Francophone de Nutrition Clinique et Métabolisme (SFNCM) a été constitué pour élaborer des propositions de recommandations, basées sur les résultats d’une enquête nationale sur les régimes à l’hôpital et sur les données de la littérature. Vingt-trois propositions de recommandations ont alors été soumises à 50 experts nationaux, selon la méthode DELPHI définie par la Haute Autorité de Santé d’élaboration de consensus formalisé d’experts.RésultatsCes vingt-trois recommandations ont été jugées appropriées et validées par un accord fort après trois tours de vote, après modifications et argumentations. Elles visent à définir chez l’adulte : 1-le vocabulaire lié aux alimentations/régimes à l’hôpital, 2-l’offre alimentaire (quantitative et qualitative), 3-la prescription nutritionnelle, 4-les modes alimentaires et adaptations aux patients, 5-délimiter les alimentations restreintes afin de réduire les régimes inutiles et sans preuve scientifique, 6-montrer l’importance de la place d’une alimentation spécifiquement adaptée aux patients dénutris et à risque de dénutrition.ConclusionCes recommandations devraient permettre à toutes les équipes de restauration et de soin, de rationnaliser l’offre alimentaire et les prescriptions d’alimentations thérapeutiques et de focaliser leur objectif sur la qualité d’une offre alimentaire adaptée aux besoins et au plaisir du patient

Antenatal prognostic factor of fetal echogenic bowel

International audienceObjective: The aim of this study was to identify antenatal prognostic factors of neonatal outcomes in cases of fetal echogenic bowel (FEB). Study design: A retrospective study in three tertiary referral centers including fetal echogenic bowel over a 10-year period (from January 2003 to December 2013). The echogenicity of the fetal bowel was graded from 1 to 3, according to Slotnick's definition. Associated echographic findings such as bowel dilations, gallbladder abnormalities, calcifications, extra-abdominal abnormalities, intrauterine growth restriction (IUGR) and a decrease in amniotic fluid volume, if present were also recorded. This was followed by the FEB's sonographic evolution. The sonographic evolution was considered favorable if it was stable or decreasing and unfavorable if the echogenicity of the bowel increased or if additional sonographic findings appeared. Neonates had a pediatric examination in the delivery room and upon discharge from the maternity hospital. An outcome was considered good in the case of on-term delivery of a newborn with normal clinical examination and meconium elimination. Results: Complete pregnancy outcome data were available for 409 pregnancies. 338 newborns had uneventful outcomes (82.6%). Antenatal exploration diagnosed 4 cases of aneuploidy (1 case of trisomy 13, 1 case of trisomy 18 and 2 cases of triploidies), 16 cases of congenital infections, 9 cases of cystic fibrosis and 11 cases of bowel abnormalities. After a multivariate analysis, we discovered the sonographic grade of the echogenic bowel was not a prognostic factor of neonatal outcome. The isolated fetal echogenic bowel had a 6.6-fold increase chance of uneventful outcomes (adjusted odd ratio (aOR) 6.6, 95% CI 3-14.4). Notably, favorable sonographic evolution (aOR 8.1, 95% CI 4.1-16) and late gestational age at the time of the diagnosis (aOR 1.17, 95% CI 1.07-1.27) are independent, good prognostic factors of good neonatal outcomes. None of the 180 fetuses with isolated fetal echogenic bowel and favorable sonographic evolution had adverse outcomes. Among these, 4 cases (0.98%) of aneuploidy, 17 cases (4.2%) of congenital infections and 9 cases (2.2%) of cystic fibroses were also diagnosed. No cases of Down syndrome (DS) were reported. Conclusion: Our study shows that the grade should not be considered a prognostic factor of neonatal outcomes. Our data suggests the need to reevaluate the concept of systematic amniocentesis. Sonographic evolution of fetal bowel is an independent, strong prognostic factor for good neonatal outcomes. It also better defines the FEB prognostic. (C) 2017 Elsevier B.V. All rights reserved