Discrete star formation events in the central bar of the Small Magellanic Cloud

We present the results of the photometric analysis of a large part of the main body of the Small Magellanic Cloud. Using the 6.5m Magellan Telescope at the Las Campanas Observatory in Chile, we have acquired deep B and I images in four fields (0.44 deg each in diameter), yielding accurate photometry for 1068 893 stars down to 24th magnitude, with a spatial resolution of 0.20 arcsec per pixel. Colour–magnitude diagrams and (completeness-corrected) luminosity functions have been constructed, yielding significant new results that indicate at least two discrete star formation events over a period from 2.7 to 4 Gyr ago. Also, we have derived star formation rates as a function of look-back time and have found enhancements of SF between 4 and 6 Gyr and at younger ages. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Anti-infectious properties of the probiotic Saccharomyces cerevisiae CNCM I-3856 on enterotoxigenic E. coli (ETEC) strain H10407

International audienceEnterotoxigenic Escherichia coli (ETEC) are major food-borne pathogens responsible for traveler's diarrhea. The production of adhesins and the secretion of enterotoxins constitute the major virulence traits of the bacteria. Treatments are mainly symptomatic and can involve antibiotherapy. However, given the rise of antibiotic resistance worldwide, there is an urgent need for the development of new preventive strategies for the control of ETEC infections. Among them, a promising approach is the use of probiotics. The aim of this study was to investigate, using complementary in vitro and in vivo approaches, the inhibitory potential of the yeast Saccharomyces cerevisiae CNCM I-3856 against the human ETEC reference strain H10407. In conventional culture media, S. cerevisiae significantly reduced ETEC growth and toxin production. The yeast also inhibited bacterial adhesion to mucin-agar and intestinal Caco-2/TC7 cells in a dose-dependent manner. Lastly, pre-treatment with S. cerevisiae inhibited interleukin-8 production by ETEC-infected intestinal cells. In streptomycin-treated mice, the probiotic yeast decreased bacterial colonization, mainly in the ileum, the main site of ETEC pathogenesis. For the first time, this study shows that the probiotic yeast S. cerevisiae CNCM I-3856 can exert an anti-infectious activity against a human ETEC strain through a multi-targeted approach, including inhibition of bacterial growth and toxin production, reduction of bacterial adhesion to mucins and intestinal epithelial cells, and suppression of ETEC-induced inflammation. Interestingly, the highest activity was obtained with a prophylactic treatment. Further studies will aim to assess the effect of the yeast on ETEC survival and virulence under human simulated digestive conditions

Proteomic detection as an alternative for the quantification of Staphylococcus aureus enterotoxins

&lt;p&gt;Food poisoning caused by ingestion of Staphylococcus aureus enterotoxins is one of the most common foodborne diseases. Staphylococcus aureus is a well-studied, omnipresent bacterium which is not only found in the environment but is also part of the commensal mammalian flora. This microorganism produces enterotoxins, protein by their structure which can cause gastro-enteritis, emesis or act as superantigen. The methods used to its confirmation in food samples are mainly of microbiological character and are not quantitative. They may not be used in prevention of any foodborne outbreaks or to properly identify them. Besides, none of those methods allow unambiguous identification, nor quantification, as molecular tools are inefficient at proving the existence of the toxins in foods and immunoassays are not specific enough, not suitable for quantification and more importantly limited in the range of toxins they can identify. The proteomic approach method for the specific detection and quantification of each toxin is achieved through the analysis of peptides (toxin fragments) unique to a toxin. The peptides are obtained by extraction, purification and concentration of the enterotoxins out of the matrix and submitted to a proteotypic digestion by trypsin, The goal was to select two specific peptides per toxin to ensure proper identification and quantification. With a recognizable extraction concept the toxin is isolated from the incriminated matrix. During the process of method development the toxin was spiked at various steps down the extraction procedure to a matrix for additional control of the extraction losses. The spiked amount of toxins (1000 ng of each enterotoxin) is not representative of a real contamination but was used for the estimation. The major conclusions were that the extraction efficiency was dependent (eg milk vs meat) on the food matrix and the selection of the proteotypicpeptides&lt;/p&gt;</p