The engineering of nanomaterials, because of their specific properties, is increasingly being developed for commercial purposes over the past decades, to enhance diagnosis, cosmetics properties as well as sensing efficiency. However, the understanding of their fate and thus their interactions at the cellular level with bio-organisms remains elusive. Here, we investigate the size- and charge-dependence of the damages induced by silica nanoparticles (SiO2-NPs) on Gram-negative Escherichia coli bacteria. We show and quantify the existence of a NPs size threshold discriminating toxic and inert SiO2-NPs with a critical particle diameter (Φc) in the range 50nm-80nm. This particular threshold is identified at both the micrometer scale via viability tests through Colony Forming Units (CFU) counting, and the nanometer scale via atomic force microscopy (AFM). At this nanometer scale, AFM emphasizes the interaction between the cell membrane and SiO2-NPs from both topographic and mechanical points of view. For SiO2-NPs with Φ>Φc no change in E. coli morphology nor its outer membrane (OM) organization is observed unless the NPs are positively charged in which case reorganization and disruption of the OM are detected. Conversely, when Φ<Φc, E. coli exhibit unusual spherical shapes, partial collapse, even lysis, and OM reorganization.

The present study aims at evaluating intrinsic changes in Escherichia coli (E. coli) surface over time, by Atomic Force Microscopy (AFM). For that purpose, bacteria were immobilized on mica or on mica previously functionalized by the deposition of a polyelectrolyte multilayer cushion. AFM images reveal that E. coli population goes through different stages. Firstly, after a week, the number of healthy bacteria decreases resulting in a release of cellular components which likely become, in turn, a nutrition source for increasing the healthy population after around two weeks. Finally, after one month, most of the bacteria is dead. Our study shows a transition of a healthy rod-shaped bacterium to a dead collapsed one. Most importantly, along with the morphological evolution of bacteria, are the structure changes and the mechanical properties of their outer membrane, emphasized by AFM phase images with very high resolution. Indeed, the surface of healthy bacteria is characterized by a phase separation pattern, thereafter mentioned as "ripples". Bacterial ageing goes along with the loss of this organized structure, turning into circular areas with irregular boundaries. These changes are likely caused by a re-organization, due to external stress, of mainly lipopolysaccharides (LPS) present in the outer membrane of E. coli.

Human actinomycosis with involvement of the spine is a rare condition although it has been first described a long time ago. It is probably underrecognized since its clinical presentation is often misleading and accurate bacteriological diagnosis is challenging. We herein report a rare case of cervical actinomycosis with paravertebral abscess and spondylitis imputed to an infection by Actinomyces meyeri in a 52-year-old immunocompetent Caucasian man. A. meyeri should be considered as a potential cause for subacute or chronic spondylitis, even in immunocompetent subjects. Modern diagnostic tools such as Matrix-Assisted Laser Desorption–Ionization Time of Flight mass spectrometry and 16S rRNA sequencing are efficient for accurate microbiological identification.

The objective of the present investigation was to evaluate the morphology of Escherchia coli bacteria in interaction with SiO2 nanoparticles. This study was made by atomic force microscopy and quartz crystal microbalance using SiO2 nanoparticles with 10nm, 50nm and 100nm diameter and bacteria immobilized on polyelectrolyte multilayer films obtained by spin coating or by “layer by layer” (LbL) method. Keywords—Atomic Force Microscopy, Escherichia coli, Quartz Crystal Microbalance, polyelectrolyte, silica nanoparticle.

Polyphenolic anthocyanins are major colorful compounds in red fruits, known to prevent cardiovascular and other diseases. Grape polyphenols are a mixture of various molecules and their exact contribution to above bioactivities remains to be clarified. In the present study, we first analyzed the effect of purified grape-derived compounds on human peripheral blood mononuclear cell (PBMC) survival, proliferation, as well as for their ability to inhibit the activation of human normal macrophages. Data indicated that malvidin-3-O-β glucoside (Malβg), the major grape anthocyanin, is bioactive with no toxicity on human PBMC. Malβg decreased the transcription of genes encoding inflammatory mediators, confirmed by the inhibition of TNFα, IL1, IL-6 and iNOS-derived nitric oxide (NO) secretion from activated macrophages. As Malβg also inhibited inflammatory response of rat macrophages, we investigated the anti-inflammatory potential of Malβg in chronic rat adjuvant-induced arthritis (AIA). Malβg significantly diminished inflammatory cachexia and arthritic paw scores in AIA rats at both therapeutic and preventive levels. In vivo effects of Malβg correlated with down-regulation of NO generation from AIA rats' peritoneal macrophages ex vivo. These data indicate that Malβg, major grape anthocyanin, is a potent anti-inflammatory agent in vitro and in vivo, without detectable toxic effect.

Background In addition to helminthic infections, elevated serum IgE levels were observed in many protozoal infections, while their contribution during immune response to these pathogens remained unclear. As IgE/antigen immune complexes (IgE-IC) bind to human cells through FcεRI or FcεRII/CD23 surface molecules, the present study aimed to identify which functional receptor may be involved in IgE-IC interaction with human macrophages, the major effector cell during parasite infection. Methodology/Principal Findings Human monocyte-derived macrophages were infected with Toxoplasma gondii before being incubated with IgE-IC. IgE receptors were then identified using appropriate blocking antibodies. The activation of cells and parasiticidal activity were evaluated by mediator quantification and direct counting of infected macrophages. RNAs were extracted and cell supernatants were also collected for their content in tumor necrosis factor (TNF)-α, interleukin-10 (IL-10) and nitrites. Sera from symptomatic infected patients were also tested for their content of IgE, IL-10 and nitrites, and compared to values found in healthy donors. Results showed that IgE-IC induced intracellular elimination of parasites by human macrophages. IgE-mediated effect was FcεRI-independent, but required cross-linking of surface FcεRII/CD23, cell activation and the generation of nitric oxide (NO). Although TNF-α was shown to be produced during cell activation, this cytokine had minor contribution in this phenomenon while endogenous and exogenous IL-10 down-regulated parasite killing. Inverse relationship was found between IL-10 and NO expression by infected human macrophages at both mRNA and mediator levels. The relationship between these in vitro data and in vivo levels of various factors in T. gondii infected patients supports the involvement of CD23 antigen and IL-10 expression in disease control. Conclusion Thus, IgE may be considered as immune mediator during antiprotozoal activity of human macrophages through its ability to trigger CD23 signaling. Increased cell activation by IgE-IC may also account for chronic inflammatory diseases observed in some patients.

Background Corynebacterium mucifaciens has been mainly isolated from skin, blood and from other normally-sterile body fluids. It has rarely been described as a human pathogen since its description. Case presentation We herein report the first case of cavitary pneumonia due to C. mucifaciens in an immunocompetent man returning from Maghreb. Conclusion C. mucifaciens should be considered as important human pathogen in patients with severe illness and compatible history of exposure even in individuals with no clearly identified immunosuppression.

A very-long-chain (C22) organosilicon self-assembled monolayer (SAM) with terminal glycidyl groups was used to immobilize antibodies on the silica waveguide of a Love mode surface acoustic wave (SAW) immunosensor. This route enabled us to specifically detect, in real time, living Escherichia coli bacteria by using monoclonal anti-E. coli antibodies, leading to a marked sensor response in liquid aqueous medium. Conversely, no bacteria detection could be observed by this direct method upon functionalization of the waveguide surface by a (3-glycidoxypropyl) trimethoxysilane (GPTS) monolayer. This improvement was attributed to a surface smoothing effect resulting from the very-long-chain SAM and a better accessibility of the surface epoxide groups.

Background Chikungunya fever is an emerging arboviral disease characterized by an algo-eruptive syndrome, inflammatory polyarthralgias, or tenosynovitis that can last for months to years. Up to now, the pathophysiology of the chronic stage is poorly understood. Case presentation We report the first case of CHIKV infection with chronic associated rheumatism in a patient who developed progressive erosive arthritis with expression of inflammatory mediators and persistence of specific IgM antibodies over 24 months following infection. Conclusions Understanding the specific features of chikungunya virus as well as how the virus interacts with its host are essential for the prevention, treatment or cure of chikungunya disease.