Isolation and Characterization of Cytotoxic, Aggregative Citrobacter freundii

Citrobacter freundii is an infrequent but established cause of diarrhea in humans. However, little is known of its genetic diversity and potential for virulence. We analyzed 26 isolates, including 12 from human diarrheal patients, 2 from human fecal samples of unknown diarrheal status, and 12 from animals, insects, and other sources. Pulsed field gel electrophoresis using XbaI allowed us to divide the 26 isolates into 20 pulse types, while multi-locus sequence typing using 7 housekeeping genes allowed us to divide the 26 isolates into 6 sequence types (STs) with the majority belonging to 4 STs. We analyzed adhesion and cytotoxicity to HEp-2 cells in these 26 strains. All were found to adhere to HEp-2 cells. One strain, CF74, which had been isolated from a goat, showed the strongest aggregative adhesion pattern. Lactate dehydrogenase (LDH) released from HEp-2 cells was evaluated as a measure of cytotoxicity, averaging 7.46%. Strain CF74 induced the highest level of LDH, 24.3%, and caused >50% cell rounding, detachment, and death. We named strain CF74 “cytotoxic and aggregative C. freundii.” Genome sequencing of CF74 revealed that it had acquired 7 genomic islands, including 2 fimbriae islands and a type VI secretion system island, all of which are potential virulence factors. Our results show that aggregative adherence and cytotoxicity play an important role in the pathogenesis of C. freundii

Fitness of Isogenic Colony Morphology Variants of Pseudomonas aeruginosa in Murine Airway Infection

Chronic lung infections with Pseudomonas aeruginosa are associated with the diversification of the persisting clone into niche specialists and morphotypes, a phenomenon called ‘dissociative behaviour’. To explore the potential of P. aeruginosa to change its morphotype by single step loss-of–function mutagenesis, a signature-tagged mini-Tn5 plasposon library of the cystic fibrosis airway isolate TBCF10839 was screened for colony morphology variants under nine different conditions in vitro. Transposon insertion into 1% of the genome changed colony morphology into eight discernable morphotypes. Half of the 55 targets encode features of primary or secondary metabolism whereby quinolone production was frequently affected. In the other half the transposon had inserted into genes of the functional categories transport, regulation or motility/chemotaxis. To mimic dissociative behaviour of isogenic strains in lungs, pools of 25 colony morphology variants were tested for competitive fitness in an acute murine airway infection model. Six of the 55 mutants either grew better or worse in vivo than in vitro, respectively. Metabolic proficiency of the colony morphology variant was a key determinant for survival in murine airways. The most common morphotype of self-destructive autolysis did unexpectedly not impair fitness. Transposon insertions into homologous genes of strain PAO1 did not reproduce the TBCF10839 mutant morphotypes for 16 of 19 examined loci pointing to an important role of the genetic background on colony morphology. Depending on the chosen P. aeruginosa strain, functional genome scans will explore other areas of the evolutionary landscape. Based on our discordant findings of mutant phenotypes in P. aeruginosa strains PAO1, PA14 and TBCF10839, we conclude that the current focus on few reference strains may miss modes of niche adaptation and dissociative behaviour that are relevant for the microevolution of complex traits in the wild

L’apport d’Internet aux petites entreprises touristiques dans la construction de leur positionnement stratégique : le cas des hébergeurs

International audienc

La contribution d'internet au positionnement stratégique des petites entreprises dans l'industrie du tourisme

International audienceSmall and medium-sized enterprises (SMEs) represent a significant share of firms in industrialised countries. However, little work is available concerning small businesses (SB) that have less than 50 employees (according to the majority of official definitions). ICT are considered a contributing factor in the renewal of competitiveness, in particular by reducing constraints that bear on SMEs. In this context, one can ask under what conditions the implementation of a website may change the strategic positioning of small accommodation businesses in the tourism sector

How entrepreneur's personality and network relationships help international new ventures to overcome constraints to rapid internationalization: the case of french firms

Firms that have both gone abroad from inception and have actively achieved a presence in lead industry markets are called international new ventures (INVs) or born-globals (BGs). The speed and international market presence lie in notably through an international network established by the entrepreneur and his or her team. Based on six in-depth case studies of young firms located in the Rhône-Alpes region of France, our study focuses on the founders' capabilities in detecting opportunities and in creating an international business network. The results clearly show that entrepreneurs build upon their skills and prior professional experience to mobilize international networks during the start-up phase in order to drive the firm's activities

The Corporate Accelerator: A New Kind of Strategic Factor Market to Access Strategic Resources

International audienceCorporate accelerators are often viewed as a way to capture innovation from startups. In this study, we present a fresh understanding of the specific role of corporate accelerators in accessing a number of strategic resources held by startups other than innovation. This research study explores the ways in which corporations use corporate accelerators to acquire resources held within the strategic factor markets in which startups compete. Using six in-depth case studies of corporate accelerators and 43 interviews with accelerators, corporations, and startups, we investigate the type of strategic resources that can be accessed by firms via corporate accelerators. We also explain the dynamics through which corporations gain access to some of these strategic resources

La mise en oeuvre d'innovations nécessite-t-elle l'instauration de certains types de réseaux ? Une application aux stations de sports d'hiver

International audienceCet article vise à étudier le lien entre la forme des réseaux interorganisationnels et les types d'innovation dans les services. Contrairement aux innovations industrielles, les innovations dans les services ne peuvent pas être protégées par des brevets ou dessins et modèles. Ainsi, la recherche de partenaires complémentaires voire la construction d'un réseau apparaît souvent comme la clé pour développer une innovation permettant de générer un avantage concurrentiel durable. C'est pourquoi nous nous sommes intéressées aux principales formes de réseaux interorganisationnels qui ont donné naissance à des innovations de services. Une typologie des innovations de service et une grille d'analyse des réseaux nous ont permis d'étudier les innovations mises en oeuvre par deux grands domaines skiables : les Portes du Soleil et Paradiski. Au total, nous avons ainsi étudié la structure de 12 réseaux d'innovation. Nos résultats montrent qu'en fonction du type d'innovation mis en place, les réseaux qui les portent diffèrent en termes de partenaires mobilisés, de mode de régulation et de rayonnement. En revanche, le type d'innovation à développer n'influence pas l'architecture du réseau, qui demeure centrée dans tous les cas

NEUTRON DIFFRACTION BY LIQUID SEGREGATED COPPER-LEAD ALLOYS

Neutron scattering experiments were performed on liquid Cu-Pb alloys above the miscibility gap. Two different enrichments in Cu65 were used in order to extract two of the three BHATIA-THORNTON pertial structure factors SNN and SNC. The variations of SNN and SNC with atomic concentration (xcu = 0.50, 0.64 and 0.80) and deporture from the demixtion temperature (950 < t < 1200°C) were determined and attributed to size effects

CALCULATION OF THE PARTIAL STRUCTURE FACTORS IN BINARY LIQUID ALLOYS BY A THERMODYNAMICAL APPROACH

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