Decolonization of asymptomatic carriage of multi-drug resistant bacteria by bacteriophages?

Antimicrobial resistance is a major threat to human and animal health and accounted for up to 4.5 million deaths worldwide in 2019. Asymptomatic colonization of the digestive tract by multidrug resistant (multi-resistant) bacteria such as extended-spectrum beta-lactamase-, or carbapenemase- producing Enterobacterales is (i) a risk factor for infection by these multi-resistant bacteria, (ii) a risk factor of dissemination of these multi-resistant bacteria among patients and in the community, and (iii) allows the exchange of resistance genes between bacteria. Hence, decolonization or reduction of the gastrointestinal tract colonization of these multi-resistant bacteria needs to be urgently explored. Developing new non-antibiotic strategies to limit or eradicate multi-resistant bacteria carriage without globally disrupting the microbiota is considered a priority to fight against antibiotic resistance. Probiotics or Fecal Microbiota Transplantation are alternative strategies to antibiotics that have been considered to decolonize intestinal tract from MDR bacteria but there is currently no evidence demonstrating their efficacy. Lytic bacteriophages are viruses that kill bacteria and therefore could be considered as a promising strategy to combat antibiotic resistance. Successful decolonization by bacteriophages has already been observed clinically. Here, we discuss the current alternative strategies considered to decolonize the digestive tract of multidrug resistant bacteria, briefly describing probiotics and fecal microbiota transplantation approaches, and then detail the in vivo and in vitro studies using bacteriophages, while discussing their limits regarding the animal models used, the characteristics of phages used and their activity in regards of the gut anatomy

Fixation symbiotique d'azote par les légumineuses en association. Résultats obtenus en Guadeloupe.

Les légumineuses (pois, haricots, soja, arachide, trèfles, luzerne...) sont une famille deplantes regroupant environ 20.000 espèces, lesquelles constituent une source de protéinesessentielle pour l'alimentation humaine et animale. Les racines des légumineuses possèdentla particularité de former des associations de coopération (symbiose) avec des bactéries dusol qui ont la capacité de fixer l'azote (N) atmosphérique, lequel n'est pas assimilable par lesvégétaux, et le transformer en substances azotées utilisables par la plante hôte. Cettepropriété permet aux légumineuses d'être cultivées sans utiliser d'engrais azotés. Encontrepartie, la légumineuse apporte à ces bactéries le carbone (source d'énergie)nécessaire à leur activité fixatrice et à leur croissance.Une partie de l'N ainsi fixé peut être aussi transférée vers les plantes associées (dansle cas d'associations de cultures) et vers le sol. Ces caractéristiques confèrent auxlégumineuses un rôle clé dans la dynamique de l'N au sein des systèmes de culture, car ellespermettent de réduire l'utilisation d'engrais, diminuer le risque de pollution azotée etaméliorer la fertilité des sols.Dans ce rapport nous réalisons une synthèse des travaux développés durant 12 ansdans notre unité, en collaboration avec des collègues de l'Université d'Helsinki (Finlande),sur la fixation symbiotique d'N et le transfert de l'N fixé. L'objectif est de mettre en évidencela fonction que les légumineuses pourraient remplir dans l'agriculture guadeloupéenne, afinde rendre plus efficaces et durables les systèmes de culture appliqués actuellement ou àappliquer dans l'avenir.Dans une première partie, nous décrivons le processus de la fixation symbiotique etla relation plante hôte/bactérie fixatrice. Nous présentons ensuite les systèmes de cultureétudiés (association sylvopastorale herbe tropicale/légumineuse ligneuse et associationbananier/légumineuse herbacée), et les résultats obtenus pour ces deux systèmes.L'N fixé par la légumineuse ligneuse a été de 470 kg N/ha/an (équivalent à 437€/ha/an) et de 111 kg N/ha/an par la légumineuse herbacée (102 €/ha/an). L'N transféré parla légumineuse (rhizodéposition, engrais vert) équivaut à un tiers de la biomasse azotée de laplante associée, ce qui démontre l'efficacité de ce processus en termes d'économie azotéedans les cultures associées. Le transfert vers le sol améliore fortement sa fertilité azotée,notamment dans le système sylvopastoral (+81 kg N/ha/an). Dans l'ensemble, les résultatssoulignent la valeur agronomique des légumineuses étudiées et leur bonne performance entant que plantes de services. Ces services écosystémiques peuvent être utilisés pouraméliorer la qualité fourragère des savanes, pour réduire l'emploi d'engrais minéraux, etpour accroitre la résilience des sols de Guadeloupe face aux impacts négatifs du changementclimatique

Spindle Assembly in Xenopus Egg Extracts: Respective Roles of Centrosomes and Microtubule Self-Organization

In Xenopus egg extracts, spindles assembled around sperm nuclei contain a centrosome at each pole, while those assembled around chromatin beads do not. Poles can also form in the absence of chromatin, after addition of a microtubule stabilizing agent to extracts. Using this system, we have asked (a) how are spindle poles formed, and (b) how does the nucleation and organization of microtubules by centrosomes influence spindle assembly? We have found that poles are morphologically similar regardless of their origin. In all cases, microtubule organization into poles requires minus end–directed translocation of microtubules by cytoplasmic dynein, which tethers centrosomes to spindle poles. However, in the absence of pole formation, microtubules are still sorted into an antiparallel array around mitotic chromatin. Therefore, other activities in addition to dynein must contribute to the polarized orientation of microtubules in spindles. When centrosomes are present, they provide dominant sites for pole formation. Thus, in Xenopus egg extracts, centrosomes are not necessarily required for spindle assembly but can regulate the organization of microtubules into a bipolar array

Virulent Clones of Klebsiella pneumoniae: Identification and Evolutionary Scenario Based on Genomic and Phenotypic Characterization

Klebsiella pneumoniae is found in the environment and as a harmless commensal, but is also a frequent nosocomial pathogen (causing urinary, respiratory and blood infections) and the agent of specific human infections including Friedländer's pneumonia, rhinoscleroma and the emerging disease pyogenic liver abscess (PLA). The identification and precise definition of virulent clones, i.e. groups of strains with a single ancestor that are associated with particular infections, is critical to understand the evolution of pathogenicity from commensalism and for a better control of infections. We analyzed 235 K. pneumoniae isolates of diverse environmental and clinical origins by multilocus sequence typing, virulence gene content, biochemical and capsular profiling and virulence to mice. Phylogenetic analysis of housekeeping genes clearly defined clones that differ sharply by their clinical source and biological features. First, two clones comprising isolates of capsular type K1, clone CC23K1 and clone CC82K1, were strongly associated with PLA and respiratory infection, respectively. Second, only one of the two major disclosed K2 clones was highly virulent to mice. Third, strains associated with the human infections ozena and rhinoscleroma each corresponded to one monomorphic clone. Therefore, K. pneumoniae subsp. ozaenae and K. pneumoniae subsp. rhinoscleromatis should be regarded as virulent clones derived from K. pneumoniae. The lack of strict association of virulent capsular types with clones was explained by horizontal transfer of the cps operon, responsible for the synthesis of the capsular polysaccharide. Finally, the reduction of metabolic versatility observed in clones Rhinoscleromatis, Ozaenae and CC82K1 indicates an evolutionary process of specialization to a pathogenic lifestyle. In contrast, clone CC23K1 remains metabolically versatile, suggesting recent acquisition of invasive potential. In conclusion, our results reveal the existence of important virulent clones associated with specific infections and provide an evolutionary framework for research into the links between clones, virulence and other genomic features in K. pneumoniae

Imaging of Red-Shifted Light From Bioluminescent Tumors Using Fluorescence by Unbound Excitation From Luminescence

Early detection of tumors is today a major challenge and requires sensitive imaging methodologies coupled with new efficient probes. In vivo optical bioluminescence imaging has been widely used in the field of preclinical oncology to visualize tumors and several cancer cell lines have been genetically modified to provide bioluminescence signals. However, the light emitted by the majority of commonly used luciferases is usually in the blue part of the visible spectrum, where tissue absorption is still very high, making deep tissue imaging non-optimal, and calling for optimized optical imaging methodologies. We have previously shown that red-shifting of bioluminescence signal by Fluorescence Unbound Excitation from Luminescence (FUEL) is a mean to increase bioluminescence signal sensitivity detection in vivo. Here, we applied FUEL to tumor detection in two different subcutaneous tumor models: the auto-luminescent human embryonic kidney (HEK293) cell line and the murine B16-F10 melanoma cell line previously transfected with a plasmid encoding the Luc2 firefly luciferase. Tumor size and bioluminescence were measured over time and tumor vascularization characterized. We then locally injected near infrared emitting Quantum Dots (NIR QDs) in the tumor site and observed a red-shifting of bioluminescence signal by (FUEL) indicating that FUEL could be used to allow deeper tumor detection in mice

Ensconsin/Map7 promotes microtubule growth and centrosome separation in Drosophila neural stem cells.

International audienceThe mitotic spindle is crucial to achieve segregation of sister chromatids. To identify new mitotic spindle assembly regulators, we isolated 855 microtubule-associated proteins (MAPs) from Drosophila melanogaster mitotic or interphasic embryos. Using RNAi, we screened 96 poorly characterized genes in the Drosophila central nervous system to establish their possible role during spindle assembly. We found that Ensconsin/MAP7 mutant neuroblasts display shorter metaphase spindles, a defect caused by a reduced microtubule polymerization rate and enhanced by centrosome ablation. In agreement with a direct effect in regulating spindle length, Ensconsin overexpression triggered an increase in spindle length in S2 cells, whereas purified Ensconsin stimulated microtubule polymerization in vitro. Interestingly, ensc-null mutant flies also display defective centrosome separation and positioning during interphase, a phenotype also detected in kinesin-1 mutants. Collectively, our results suggest that Ensconsin cooperates with its binding partner Kinesin-1 during interphase to trigger centrosome separation. In addition, Ensconsin promotes microtubule polymerization during mitosis to control spindle length independent of Kinesin-1