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International audience; Legionella pneumophila is a pathogenic bacterium involved in regular outbreaks characterized by a relatively high fatality rate and an important societal impact. Frequent monitoring of the presence of this bacterium in environmental water samples is necessary to prevent these epidemic events, but the traditional culture-based detection and identification method requires up to 10 days. Reported herein is a method allowing identification of Legionella pneumophila by metabolic lipopolysaccharide labeling which targets, for the first time, a precursor to monosaccharides that are specifically present within the O-antigen of the bacterium. This new approach allows easy detection of living Legionella pneumophila, while other Legionella species are not labeled.

International audience; The Gram-negative bacterium Neisseria meningitidis asymptomatically colonizes the throat of 10 to 30% of the human population, but throat colonization can also act as the port of entry to the blood (septicemia) and then the brain (meningitis). Colonization is mediated by filamentous organelles referred to as type IV pili, which allow the formation of bacterial aggregates associated with host cells. We found that proliferation of N. meningitidis in contact with host cells increased the transcription of a bacterial gene encoding a transferase that adds phosphoglycerol onto type IV pili. This unusual posttranslational modification specifically released type IV pili-dependent contacts between bacteria. In turn, this regulated detachment process allowed propagation of the bacterium to new colonization sites and also migration across the epithelium, a prerequisite for dissemination and invasive disease.

International audience; In Salmonella-infected cells, the bacterial effector SifA forms a functional complex with the eukaryotic protein SKIP (SifA and kinesin-interacting protein). The lack of either partner has important consequences on the intracellular fate and on the virulence of this pathogen. In addition to SifA, SKIP binds the microtubule-based motor kinesin-1. Yet the absence of SifA or SKIP results in an unusual accumulation of kinesin-1 on the bacterial vacuolar membrane. To understand this apparent contradiction, we investigated the interaction between SKIP and kinesin-1 and the function of this complex. We show that the C-terminal RUN (RPIP8, UNC-14 and NESCA) domain of SKIP interacted specifically with the tetratricopeptide repeat (TPR) domain of the kinesin light chain. Overexpression of SKIP induced a microtubule- and kinesin-1-dependent anterograde movement of late endosomal/lysosomal compartments. In infected cells, SifA contributed to the fission of vesicles from the bacterial vacuole and the SifA/SKIP complex was required for the formation and/or the anterograde transport of kinesin-1-enriched vesicles. These observations reflect the role of SKIP as a linker and/or an activator for kinesin-1.

International audience; SifA is a Salmonella effector that is translocated into infected cells by the pathogenicity island 2-encoded type three secretion system. SifA is a critical virulence factor. Previous studies demonstrated that, upon translocation, SifA binds the pleckstrin homology motif of the eukaryotic host protein SKIP. In turn, the SifA-SKIP complex regulates the mobilization of the molecular motor kinesin-1 on the bacterial vacuole. SifA exhibits multiple domains containing functional motifs. Here we performed a molecular dissection and a mutational study of SifA to evaluate the relative contribution of the different domains to SifA functions. Biochemical and crystallographic analysis confirmed that the N-terminal domain of SifA is sufficient to interact with the PH domain of SKIP, forming a 1:1 complex with a micromolar dissociation constant. Mutation of the tryptophan (W) residue in the WxxxE motif, which has been proposed to mimic active form of GTPase, deeply affected the stability and the translocation of SifA while mutations of the glutamic residue (E) had no functional impact. A SifA L130D mutant that does not bind SKIP showed a sifA-like phenotype both in infected cells and in the mouse model of infection. We concluded that the WxxxE motif is essential for maintaining the tertiary structure of SifA, the functions of which require the interaction with the eukaryotic protein SKIP.

Understanding the mechanisms of Salmonella virulence is an important challenge. The capacity of this intracellular bacterial pathogen to cause diseases depends on the expression of virulence factors including the second type III secretion system (TTSS-2), which is used to translocate into the eukaryotic cytosol a set of effector proteins that divert the biology of the host cell and shape the bacterial replicative niche. Yet little is known about the eukaryotic functions affected by individual Salmonella effectors. Here we report that the TTSS-2 effector PipB2 interacts with the kinesin light chain, a subunit of the kinesin-1 motor complex that drives anterograde transport along microtubules. Translocation of PipB2 is both necessary and sufficient for the recruitment of kinesin-1 to the membrane of the Salmonella -containing vacuole. In vivo , PipB2 contributes to the attenuation of Salmonella mutant strains in mice. Taken together, our data indicate that the TTSS-2-mediated fine-tuning of kinesin-1 activity associated with the bacterial vacuole is crucial for the virulence of Salmonella .

La maladie athéromateuse rénovasculaire est responsable d’une morbi-mortalité élevée. Plusieurs essais randomisés ont conclu à l’absence de bénéfice de la revascularisation percutanée en comparaison au traitement médical optimisé. Cependant ces études ne prenaient pas en compte les présentations cliniques à haut-risque regroupant hypertension artérielle (HTA) résistante, œdème aigu pulmonaire (OAP) flash ou insuffisance rénale rapidement progressive. Ainsi, nous avons évalué l’intérêt de l’angioplastie plus particulièrement dans cette population en contexte de sténoses bilatérales des artères rénales sévères.ObjectifsNous avons réalisé une étude observationnelle rétrospective au CHU de Rouen sur 83 patients, entre le 01/01/1996 et le 31/12/2017 inclus, atteints de sténose athéromateuse des artères rénales (SAAR) ≥ 50% bilatérales ou unilatérales sur rein unique (40% des SAAR ≥ 80%). L’objectif principal de l’étude était d’analyser à la fois pour les présentations à haut-risque (n=53, 64%) regroupant HTA résistantes (n=29), OAP flashs (n=11), HTA résistantes avec insuffisance rénale aiguë (IRA) associée (n=9) et IRA isolée (n=4) ; et à bas-risque (n=30, 36%), l’impact de l’angioplastie sur la mortalité, l’évolution vers l’insuffisance rénale chronique (IRC) terminale et la survenue d’évènements cardiovasculaires (ECV) en comparaison au traitement médical. Secondairement, nous avons évalué l’intérêt de l’angioplastie sur le profil tensionnel et la fonction rénale.RésultatsAu total 54 patients ont été revascularisés dont 66% dans le groupe haut-risque. Au cours d’un suivi médian de 52 mois, 60% des patients haut-risque sont décédés, 25% ont évolué vers l’IRC terminale et enfin plus de 40% ont subi au moins un ECV. Nous mettons en évidence, dans ce groupe, un bénéfice de l’angioplastie à la fois sur la mortalité et la survie rénale en cas de SAAR ≥ 80% (respectivement p=0,01 et p=0,02). Nous montrons également un bénéfice de l’angioplastie sur l’amélioration de la PA systolique (groupe haut-risque) à 6 et 12 mois avec respectivement une baisse de 9 mmHg (p=0,01) et 10 mmHg (p=0,005). L’interprétation de nos résultats est limitée par l’aspect rétrospectif de l’étude et ses biais, le faible effectif et le manque de puissance de notre analyse statistique.ConclusionCette étude tend à montrer un bénéfice supérieur de l’angioplastie comparativement au traitement médical, dans la prise en charge des patients à haut-risque en contexte de MARV sévère, en cohérence avec les publications récentes.