18 research outputs found

    Infections chroniques à staphylocoques: mécanismes de persistance intracellulaire et nouvelles approches thérapeutiques

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    Staphylococcus aureus, pathogĂšne opportuniste responsable d’un large panel d’infections a motivĂ© l’utilisation intensive d’antibiotique ces derniĂšres dĂ©cennies, favorisant l’émergence de S. aureus rĂ©sistants notamment Ă  la vancomycine, appelĂ©es VISA (Vancomycin Intermediate S. aureus). Des Ă©tudes ont mis en Ă©vidence un lien entre baisse de virulence et de sensibilitĂ© Ă  la vancomycine en associant cette infection au passage Ă  la chronicitĂ©. Dans ce contexte, le premier objectif de notre Ă©tude a Ă©tĂ© d’étudier le mĂ©canisme de persistance des souches VISA dans les CPNP (Cellules Phagocytaires Non Professionnelles) in vitro dans un modĂšle de culture cellulaire. Cette premiĂšre Ă©tude a Ă©tĂ© rĂ©alisĂ©e sur 2 couples de souches cliniques composĂ©s d’une souche VSSA (Vancomycin Susceptible Staphylococcus aureus), d’une souche VISA ainsi qu’une souche inactivĂ©e pour le gĂšne stp1 suspectĂ© pour son rĂŽle dans la diminution de la sensibilitĂ© Ă  la vancomycine. Les rĂ©sultats obtenus montraient une homogĂ©nĂ©itĂ© de phĂ©notypes prĂ©sentĂ©s par les 2 couples de souches, dĂ©montrant que les souches VISA Ă©taient moins cytotoxiques, induisaient une rĂ©ponse inflammatoire amoindrie et persistaient en plus grand nombre jusqu’à 14 jours post-infection dans les ostĂ©oblastes. La souche dĂ©lĂ©tĂ©e pour stp1 a montrĂ© quant Ă  elle peu de diffĂ©rences phĂ©notypiques par rapport Ă  la souche parentale VSSA. Nos rĂ©sultats suggĂšrent que cette baisse de virulence observĂ©e avec les souches VISA serait associĂ©e Ă  une plus grande capacitĂ© de persistance intracellulaire et Ă  un moindre pouvoir cytotoxique. Ces rĂ©sultats ont aussi montrĂ© l’importance de dĂ©velopper de nouvelles molĂ©cules anti staphylococciques Ă  visĂ©e intracellulaire. Dans cette optique, dans un second temps, nous avons rĂ©alisĂ© deux Ă©tudes sur l’efficacitĂ© de nouvelles molĂ©cules anti-staphylococciques Ă  visĂ©e intracellulaire dans le cadre de collaboration avec des sociĂ©tĂ©s pharmaceutiques. Les rĂ©sultats obtenus lors de ces Ă©tudes ont Ă©tĂ© encourageants, en effet, nos rĂ©sultats prĂ©liminaires ont montrĂ© l’intĂ©rĂȘt de ces nouveaux inhibiteurs anti-staphylococciques dans l’élimination des S. aureus intracellulaires, avec une efficacitĂ© supĂ©rieure Ă  la rifampicine pour l’une de ces molĂ©cules. Ces molĂ©cules, en combinaison avec des antibiotiques standards, pourraient constituer une option thĂ©rapeutique prĂ©cieuse pour le traitement des infections ostĂ©o-articulaires.La derniĂšre partie de ce travail portait sur les capacitĂ©s d’internalisation et de persistance intracellulaire de Staphylococcus non-aureus (SNA). Nous avons Ă©tudiĂ© diffĂ©rentes souches de S. simiae et S. schleiferi ainsi que S. argenteus et S. schweitzeri qui ont Ă©tĂ© dĂ©crites plus rĂ©cemment. Les souches S. argenteus, S. schweitzeri et S. schleiferi ont indiquĂ© une capacitĂ© Ă  persister dans les CPNP autant voire plus importante que S. aureus, exigeant une nouvelle vigilance d’un point de vu clinique sur le choix thĂ©rapeutique lors d’une infection Ă  l’un de ces staphylocoques

    Evaluation of the ability of linezolid and tedizolid to eradicate intraosteoblastic and biofilm-embedded Staphylococcus aureus in the bone and joint infection setting

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    Objectives: Prolonged use of linezolid for bone and joint infection (BJI) is limited by its long-term toxicity. The better safety profile of tedizolid, a recently developed oxazolidinone, could offer an alternative. However, its efficacy against biofilm-embedded and intracellular Staphylococcus aureus, the two main bacterial reservoirs associated with BJI chronicity, is unknown.Methods: Using three S. aureus strains (6850 and two clinical BJI isolates), linezolid and tedizolid were compared regarding their ability: (i) to target the S. aureus intracellular reservoir in an in vitro model of osteoblast infection, using three concentrations increasing from the bone concentration reached with standard therapeutic doses (Cbone = 2.5 × MIC; Cplasm = 10 × MIC; Cmax = 40 × MIC); (ii) to eradicate mature biofilm [minimal biofilm eradication concentration (MBEC)]; and (iii) to prevent biofilm formation [biofilm MIC (bMIC) and confocal microscopy].Results: Linezolid and tedizolid weakly reduced the intracellular inoculum of S. aureus in a strain-dependent manner despite the similar MICs for the tested strains, but improved cell viability even in the absence of an intracellular bactericidal effect. Conversely, linezolid and tedizolid were ineffective in eradicating mature biofilm formed in vitro, with MBEC >2000 and >675?mg/L, respectively. bMICs of tedizolid were 4-fold lower than those of linezolid for all strains.Conclusions: Linezolid and tedizolid alone are not optimal candidates to target bacterial phenotypes associated with chronic forms of BJI. Despite weak intracellular activity, they both reduce infection-related cytotoxicity, suggesting a role in modulating intracellular expression of staphylococcal virulence factors. Although inactive against biofilm-embedded S. aureus, both-but particularly tedizolid-are able to prevent biofilm formation

    Bone and Joint Infection Involving Corynebacterium spp.: From Clinical Features to Pathophysiological Pathways

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    Introduction: Corynebacteria represent often-neglected etiological agents of post-traumatic and/or post-operative bone and joint infection (BJI). We describe here clinical characteristics and bacteriological determinants of this condition. Methods: A retrospective cohort study described characteristics, outcome and determinants of treatment failure of all patients with proven Corynebacterium spp. BJI (i.e., ?2 culture-positive gold-standard samples). Available strains were further characterized regarding their antibiotic susceptibilies, abilities to form early (BioFilm Ring TestÂź) and mature (crystal violet staining method) biofilms and to invade osteoblasts (gentamicin protection assay). Results: The 51 included BJI were mostly chronic (88.2%), orthopedic device-related (74.5%) and polymicrobial (78.4%). After a follow-up of 60.7 weeks (IQR, 30.1-115.1), 20 (39.2%) treatment failures were observed, including 4 Corynebacterium-documented relapses, mostly associated with non-optimal surgical management (OR 7.291; p = 0.039). Internalization rate within MG63 human osteoblasts was higher for strains isolated from delayed (>3 months) BJI (p < 0.001). Infection of murine osteoblasts deleted for the ?1-integrin resulted in a drastic reduction in the internalization rate. No difference was observed regarding biofilm formation. Conclusions: Surgical management plays a crucial role in outcome of BJI involving corynebacteria, as often chronic and device-associated infections. Sanctuarisation within osteoblasts, implicating the ?1 cellular integrin, may represent a pivotal virulence factor associated with BJI chronicity

    Clinical evaluation of three chromogenic media for the isolation of Staphylococcus aureus in respiratory samples in patients with cystic fibrosis

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    International audienceWe evaluated the performance of three chromogenic media (BBL CHROMagarℱ Staph aureus, ChromIDℱ S. aureus SAID, ChromIDℱ S. aureus Elite SAIDE) for the isolation of Staphylococcus aureus in respiratory samples in patients with cystic fibrosis in comparison with CNA media. We reported a similar ability of the four media to support the growth of S. aureus and that sensitivity increased when incubation lasted more than 24 h. SAIDE had the higher sensitivity compared to the other media and kept a high specificity even after 72 h

    LipoParticles: A Lipid Membrane Coating onto Polymer Particles to Enhance the Internalization in Osteoblast Cells

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    International audienceLipoParticles, core–shell assemblies consisting of a polymer core coated by a lipid membrane, are promising carriers for drug delivery applications with intracellular targets

    Combinatorial Drug Therapy: Compartmentalized Encapsulation of Two Antibiotics in Porous Nanoparticles: an Efficient Strategy to Treat Intracellular Infections (Part. Part. Syst. Charact. 3/2019)

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    International audienceBack Cover : As demonstrated by Ruxendra Gref and co‐workers in article number 1800360, two synergic drugs, amoxicillin and potassium clavulanate, were co‐encapsulated within highly porous nanoparticles made of metal‐organic frameworks (nanoMOFs). Within the interconnected 3D structure, each drug located in a separate compartment and these findings were supported by molecular simulations. NanoMOFs were efficiently internalized in infected macrophages and contributed together with the entrapped drugs to kill intracellular bacteria

    Compartmentalized Encapsulation of Two Antibiotics in Porous Nanoparticles: an Efficient Strategy to Treat Intracellular Infections

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    International audienceCombinatorial drug therapies emerge among the most promising strategies to treat complex pathologies such as cancer and severe infections. Biocompatible nanoparticles of mesoporous iron carboxylate metal–organic framework (nanoMOFs) are used here to address the challenging aspects related to the coincorporation of two antibiotics. Amoxicillin and potassium clavulanate, a typical example of drugs used in tandem, are efficiently coincorporated with payloads up to 36 wt%. Due to the occurrence of two distinct pore sizes/apertures within the MOF architecture, each drug is able to infiltrate the porous framework and localize within separate compartments. Molecular simulations predict drug loadings and locations consistent with experimental findings. Drug loaded nanoMOFs that are internalized by Staphylococcus aureus infected macrophages are able to colocalize with the pathogen, which in turn leads to an alleviation of bacterial infection. The data also reveal potential antibacterial properties of nanoMOFs alone as well as their ability to deliver a high payload of drugs to fight intracellular bacteria. These results pave the way toward the design of engineered “all‐in‐one” nanocarriers in which both the loaded drugs and their carrier play a role in fighting intracellular infections
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