Impact de l'implantation du module d'enregistrement des ventes sur le secteur de la restauration au Québec

C’est grâce à une initiative de Revenu Québec, avec la collaboration de l’Association des restaurateurs du Québec, que le module d'enregistrement des ventes a été déployé dans le secteur de la restauration, entre le 1er septembre 2010 et le 1er novembre 2011, afin de lutter contre l’évasion fiscale. Jusqu’à ce jour, l’impact de ce projet a seulement été évalué à l’interne par Revenu Québec. Cette étude propose donc une analyse empirique, avec les données publiques canadiennes, afin d’évaluer l’impact de l’implantation du module d'enregistrement des ventes dans le secteur de la restauration au Québec, à l’aide d’un modèle en difference-in-differences et d’un modèle en Premières différences. Plus précisément, nous cherchons à déterminer si la mesure a eu un impact sur le PIB du secteur de l’hébergement et des services de restauration au Québec. Avec l’implantation du module d’enregistrement des ventes, on s’attend à ce que les possibilités d’évasion fiscale soient réduites et que les ventes déclarées augmentent. Les résultats de l’analyse suggèrent des signes potentiels d’effets de la mesure, sans toutefois avoir suffisamment de précision dans les données pour appuyer l’hypothèse avec certitude

Growth of Yersinia pseudotuberculosis in human plasma: impacts on virulence and metabolic gene expression

<p>Abstract</p> <p>Background</p> <p>In man, infection by the Gram-negative enteropathogen <it>Yersinia pseudotuberculosis </it>is usually limited to the terminal ileum. However, in immunocompromised patients, the microorganism may disseminate from the digestive tract and thus cause a systemic infection with septicemia.</p> <p>Results</p> <p>To gain insight into the metabolic pathways and virulence factors expressed by the bacterium at the blood stage of pseudotuberculosis, we compared the overall gene transcription patterns (the transcriptome) of bacterial cells cultured in either human plasma or Luria-Bertani medium. The most marked plasma-triggered metabolic consequence in <it>Y. pseudotuberculosis </it>was the switch to high glucose consumption, which is reminiscent of the acetogenic pathway (known as "glucose overflow") in <it>Escherichia coli</it>. However, upregulation of the glyoxylate shunt enzymes suggests that (in contrast to <it>E. coli</it>) acetate may be further metabolized in <it>Y. pseudotuberculosis</it>. Our data also indicate that the bloodstream environment can regulate major virulence genes (positively or negatively); the <it>yadA </it>adhesin gene and most of the transcriptional units of the pYV-encoded type III secretion apparatus were found to be upregulated, whereas transcription of the pH6 antigen locus was strongly repressed.</p> <p>Conclusion</p> <p>Our results suggest that plasma growth of <it>Y. pseudotuberculosis </it>is responsible for major transcriptional regulatory events and prompts key metabolic reorientations within the bacterium, which may in turn have an impact on virulence.</p

Impact de l'implantation du module d'enregistrement des ventes sur le secteur de la restauration au Québec

C’est grâce à une initiative de Revenu Québec, avec la collaboration de l’Association des restaurateurs du Québec, que le module d'enregistrement des ventes a été déployé dans le secteur de la restauration, entre le 1er septembre 2010 et le 1er novembre 2011, afin de lutter contre l’évasion fiscale. Jusqu’à ce jour, l’impact de ce projet a seulement été évalué à l’interne par Revenu Québec. Cette étude propose donc une analyse empirique, avec les données publiques canadiennes, afin d’évaluer l’impact de l’implantation du module d'enregistrement des ventes dans le secteur de la restauration au Québec, à l’aide d’un modèle en difference-in-differences et d’un modèle en Premières différences. Plus précisément, nous cherchons à déterminer si la mesure a eu un impact sur le PIB du secteur de l’hébergement et des services de restauration au Québec. Avec l’implantation du module d’enregistrement des ventes, on s’attend à ce que les possibilités d’évasion fiscale soient réduites et que les ventes déclarées augmentent. Les résultats de l’analyse suggèrent des signes potentiels d’effets de la mesure, sans toutefois avoir suffisamment de précision dans les données pour appuyer l’hypothèse avec certitude

YAPI, a New Yersinia pseudotuberculosis Pathogenicity Island

Pathogenicity islands (PAIs) are chromosomal clusters of pathogen-specific virulence genes often found at tRNA loci. In the Yersinia pseudotuberculosis 32777 chromosome, we characterized a 98-kb segment that has all of the characteristic features of a PAI, including insertion in a (phenylalanine) tRNA gene, the presence of a bacteriophage-like integrase-encoding gene, and direct repeats at the integration sites. The G+C content of the segment ranges from 31 to 60%, reflecting a genetic mosaic: this is consistent with the notion that the sequences were horizontally acquired. The PAI, termed YAPI (for Yersinia adhesion pathogenicity island), carries 95 open reading frames and includes (i) the previously described pil operon, encoding a type IV pilus that contributes to pathogenicity (F. Collyn et al., Infect. Immun. 70:6196-6205, 2002); (ii) a block of genes potentially involved in general metabolism; (iii) a gene cluster for a restriction-modification system; and (iv) a large number of mobile genetic elements. Furthermore, the PAI can excise itself from the chromosome at low frequency and in a precise manner, and deletion does not result in a significant decrease of bacterial virulence compared to inactivation of the fimbrial gene cluster alone. The prevalence and size of the PAI vary from one Y. pseudotuberculosis strain to another, and it can be found integrated into either of the two phe tRNA loci present on the species' chromosome. YAPI was not detected in the genome of the genetically closely related species Y. pestis, whereas a homologous PAI is harbored by the Y. enterocolitica chromosome

Yersinia pseudotuberculosis Harbors a Type IV Pilus Gene Cluster That Contributes to Pathogenicity

Fimbriae have been shown to play an essential role in the adhesion of pathogenic gram-negative bacteria to host cells. In the enteroinvasive bacterium Yersinia pseudotuberculosis, we characterized a previously unknown 11-kb chromosomal locus involved in the synthesis of type IV pili. The locus consists of 11 open reading frames forming a polycistronic unit and encoding putative Pil proteins, PilLMNOPQRSUVW. When introduced into Escherichia coli, the Y. pseudotuberculosis operon reconstituted bundles of filaments at a pole on the bacterial surface, demonstrating that the pil locus was functional in a heterogenous genetic background. Environmental factors regulated transcription of the Y. pseudotuberculosis operon; in particular, temperature, osmolarity, and oxygen tension were critical cues. Deletion of the type IV pilus gene cluster was associated with a reduction of Y. pseudotuberculosis pathogenicity for mice infected orally. Forty-one percent of Y. pseudotuberculosis strains isolated from human or animal sources harbored the type IV pilus locus. Therefore, the pil locus of Y. pseudotuberculosis might constitute an “adaptation island,” permitting the microorganism to colonize a vast reservoir

Evaluation of the Role of the opgGH Operon in Yersinia pseudotuberculosis and Its Deletion during the Emergence of Yersinia pestis

International audienceThe opgGH operon encodes glucosyltransferases that synthesize osmoregulated periplasmic glucans (OPGs) from UDP-glucose, using acyl carrier protein (ACP) as a cofactor. OPGs are required for motility, biofilm formation, and virulence in various bacteria. OpgH also sequesters FtsZ in order to regulate cell size according to nutrient availability. Yersinia pestis (the agent of flea-borne plague) lost the opgGH operon during its emergence from the enteropathogen Yersinia pseudotuberculosis. When expressed in OPG-negative strains of Escherichia coli and Dickeya dadantii, opgGH from Y. pseudotuberculosis restored OPGs synthesis, motility, and virulence. However, Y. pseudotuberculosis did not produce OPGs (i) under various growth conditions or (ii) when overexpressing its opgGH operon, its galUF operon (governing UDP-glucose), or the opgGH operon or Acp from E. coli. A ⌬opgGH Y. pseudotuberculosis strain showed normal motility, biofilm formation, resistance to polymyxin and macro-phages, and virulence but was smaller. Consistently, Y. pestis was smaller than Y. pseudotuberculosis when cultured at >37°C, except when the plague bacillus expressed opgGH. Y. pestis expressing opgGH grew normally in serum and within macrophages and was fully virulent in mice, suggesting that small cell size was not advantageous in the mammalian host. Lastly, Y. pestis expressing opgGH was able to infect Xenopsylla cheopis fleas normally. Our results suggest an evolutionary scenario whereby an ancestral Yersinia strain lost a factor required for OPG biosynthesis but kept opgGH (to regulate cell size). The opgGH operon was presumably then lost because OpgH-dependent cell size control became unnecessary

Transcriptome analysis of Yersinia pestis in human plasma: an approach for discovering bacterial genes involved in septicaemic plague

International audienceYersinia pestis is the aetiologic agent of plague. Without appropriate treatment, the pathogen rapidly causes septicaemia, the terminal and fatal phase of the disease. In order to identify bacterial genes which are essential during septicaemic plague in humans, we performed a transcriptome analysis on the fully virulent Y. pestis CO92 strain grown in either decomplemented human plasma or Luria-Bertani medium, incubated at either 28 or 37 degrees C and harvested at either the mid-exponential or the stationary growth phase. Y. pestis genes involved in 12 iron-acquisition systems and one iron-storage system (bfr, bfd) were specifically induced in human plasma. Of these, the ybt and tonB genes (encoding the yersiniabactin siderophore virulence factor and the siderophore transporter, respectively) were induced at 37 degrees C, i.e. under conditions mimicking the mammalian environment. Growth in human plasma also upregulated genes involved in the synthesis of five fimbrial-like structures (including the Psa virulence factor), and in purine/pyrimidine metabolism (the nrd genes). Genes known to play a role in the virulence of several bacterial pathogens (such as those encoding the Lpp lipoprotein and non-iron metal-uptake proteins) were induced in human plasma, during either the exponential or the stationary phase. Finally, 120 genes encoding proteins of unknown function were upregulated in human plasma. Eleven of these genes were specifically transcribed at 37 degrees C and may thus represent new virulence factors that are important during the septicaemic phase of human plague