Immune modulation by group B Streptococcus influences host susceptibility to urinary tract infection by uropathogenic Escherichia coli

Urinary tract infection (UTI) is most often caused by uropathogenic Escherichia coli (UPEC). UPEC inoculation into the female urinary tract (UT) can occur through physical activities that expose the UT to an inherently polymicrobial periurethral, vaginal, or gastrointestinal flora. We report that a common urogenital inhabitant and opportunistic pathogen, group B Streptococcus (GBS), when present at the time of UPEC exposure, undergoes rapid UPEC-dependent exclusion from the murine urinary tract, yet it influences acute UPEC-host interactions and alters host susceptibility to persistent outcomes of bladder and kidney infection. GBS presence results in increased UPEC titers in the bladder lumen during acute infection and reduced inflammatory responses of murine macrophages to live UPEC or purified lipopolysaccharide (LPS), phenotypes that require GBS mimicry of host sialic acid residues. Taken together, these studies suggest that despite low titers, the presence of GBS at the time of polymicrobial UT exposure may be an overlooked risk factor for chronic pyelonephritis and recurrent UTI in susceptible groups, even if it is outcompeted and thus absent by the time of diagnosis

Quantitative RT-PCR profiling of the Rabbit Immune Response: Assessment of Acute Shigella flexneri Infection

Quantitative reverse transcription PCR analysis is an important tool to monitor changes in gene expression in animal models. The rabbit is a widely accepted and commonly used animal model in the study of human diseases and infections by viral, fungal, bacterial and protozoan pathogens. Only a limited number of rabbit genes have, however, been analyzed by this method as the rabbit genome sequence remains unfinished. Recently, increasing coverage of the genome has permitted the prediction of a growing number of genes that are relevant in the context of the immune response. We hereby report the design of twenty-four quantitative PCR primer pairs covering common cytokines, chemoattractants, antimicrobials and enzymes for a rapid, sensitive and quantitative analysis of the rabbit immune response. Importantly, all primer pairs were designed to be used under identical experimental conditions, thereby enabling the simultaneous analysis of all genes in a high-throughput format. This tool was used to analyze the rabbit innate immune response to infection with the human gastrointestinal pathogen Shigella flexneri. Beyond the known inflammatory mediators, we identified IL-22, IL-17A and IL-17F as highly upregulated cytokines and as first responders to infection during the innate phase of the host immune response. This set of qPCR primers also provides a convenient tool for monitoring the rabbit immune response during infection with other pathogens and other inflammatory conditions

Salmonella – the ultimate insider. Salmonella virulence factors that modulate intracellular survival

Salmonella enterica serovar Typhimurium is a common facultative intracellular pathogen that causes food-borne gastroenteritis in millions of people worldwide. Intracellular survival and replication are important virulence determinants and the bacteria can be found in a variety of phagocytic and non-phagocytic cells in vivo. Invasion of host cells and intracellular survival are dependent on two type III secretion systems, T3SS1 and T3SS2, each of which translocates a distinct set of effector proteins. However, other virulence factors including ion transporters, superoxide dismutase, flagella and fimbriae are also involved in accessing and utilizing the intracellular niche

Bacterial Effector Binding to Ribosomal Protein S3 Subverts NF-κB Function

Enteric bacterial pathogens cause food borne disease, which constitutes an enormous economic and health burden. Enterohemorrhagic Escherichia coli (EHEC) causes a severe bloody diarrhea following transmission to humans through various means, including contaminated beef and vegetable products, water, or through contact with animals. EHEC also causes a potentially fatal kidney disease (hemolytic uremic syndrome) for which there is no effective treatment or prophylaxis. EHEC and other enteric pathogens (e.g., enteropathogenic E. coli (EPEC), Salmonella, Shigella, Yersinia) utilize a type III secretion system (T3SS) to inject virulence proteins (effectors) into host cells. While it is known that T3SS effectors subvert host cell function to promote diarrheal disease and bacterial transmission, in many cases, the mechanisms by which these effectors bind to host proteins and disrupt the normal function of intestinal epithelial cells have not been completely characterized. In this study, we present evidence that the E. coli O157:H7 nleH1 and nleH2 genes encode T3SS effectors that bind to the human ribosomal protein S3 (RPS3), a subunit of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcriptional complexes. NleH1 and NleH2 co-localized with RPS3 in the cytoplasm, but not in cell nuclei. The N-terminal region of both NleH1 and NleH2 was required for binding to the N-terminus of RPS3. NleH1 and NleH2 are autophosphorylated Ser/Thr protein kinases, but their binding to RPS3 is independent of kinase activity. NleH1, but not NleH2, reduced the nuclear abundance of RPS3 without altering the p50 or p65 NF-κB subunits or affecting the phosphorylation state or abundance of the inhibitory NF-κB chaperone IκBα NleH1 repressed the transcription of a RPS3/NF-κB-dependent reporter plasmid, but did not inhibit the transcription of RPS3-independent reporters. In contrast, NleH2 stimulated RPS3-dependent transcription, as well as an AP-1-dependent reporter. We identified a region of NleH1 (N40-K45) that is at least partially responsible for the inhibitory activity of NleH1 toward RPS3. Deleting nleH1 from E. coli O157:H7 produced a hypervirulent phenotype in a gnotobiotic piglet model of Shiga toxin-producing E. coli infection. We suggest that NleH may disrupt host innate immune responses by binding to a cofactor of host transcriptional complexes

Effets de la migration transépithéliale des polynucléaires neutrophiles sur les mécanismes apoptotiques des cellules épithéliales intestinales et des polynucléaires neutrophiles

La migration massive des polynucléaires neutrophiles (PNN) à travers l épithélium intestinal caractérise mes phases aiguës des maladies inflammatoires intestinales chroniques de l intestin (MICI), et permet l élimination des micro-organismes pathogènes. La résolution de l inflammation dépend aussi de l apoptose, ou mort cellulaire programmée des cellules épithéliales intestinales (CEI) et des PNN. Grâce à l utilisation d un modèle de migration transépithéliale des PNN in vitro, nous avons mis en évidence que la migration transépithéliale massive des PNN induit l apoptose des CEI (cellules T84) et prolonge la durée de vie des PNN transmigrés. L apoptose des cellules T84 ne dépend pas de la voie Fas alors que la réorganisation prolongée du cytosquelette d actine dans les cellules T84 est directement impliquée. L effet anti-apoptotique de la transmigration sur la durée de vie des PNN est associé à une diminution d expression des procaspases et de Fas ligand dans les PNN transmigrés. Cette diminution d expression de Fas ligand est directement impliquée dans le rallongement de la durée de vie des PNN. Par ailleurs, nous avons aussi montré qu Helicobacter pylori, une bactérie pathogène, induit l apoptose des CEI par un mécanisme impliquant l activation du récepteur Fas et l expression des facteurs de virulence bactériens, la cytotoxine vacA et l îlot de pathogénicité cag.NICE-BU Sciences (060882101) / SudocSudocFranceF

Understanding carbonaceous deposit formation resulting from engine oil degradation

International audienceThe formation processes of carbonaceous deposits in the first piston ring grooves of direct injection diesel engines have been studied. Deposits generated during engine tests were analysed by SEM/EDX, thermogravimetric analysis, pyrolysis/gas chromatography/mass spectrometry, and FT-IR spectroscopy. These analyses showed that the deposits, with a structure of cracked varnishes, mainly resulted from the degradation of lubricants. Their state strongly depends on the severity of the tests, which resulted in the formation of two kinds of deposits, termed as 'oily' and 'dry', according to their content of volatile organic matters. Then, to better understand the deposit formation process, a thermo-oxidative degradation of the lubricating oil was carried out in a tubular furnace, while varying temperature, duration of the test, and adding metallic elements to simulate the engine wear. The consumption of antioxidant additives and the lubricant carbonization were highlighted. Temperature level was identified as the most influential parameter during the lubricant degradation process. The presence of metallic elements appeared to act as a catalyst by speeding up the degradation when the tests duration was increased. Cop. 2008 Elsevier Ltd. All rights reserved

Analysis of the volatile organic matter of engine piston deposits by direct sample introduction thermal desorption gas chromatography/mass spectrometry.

International audienceThis article establishes an alternative method for the characterization of volatiles organic matter (VOM) contained in deposits of the piston first ring grooves of diesel engines using a ChromatoProbe direct sample introduction (DSI) device coupled to gas chromatography/mass spectrometry (GC/MS) analysis. The addition of an organic solvent during thermal desorption leads to an efficient extraction and a good chromatographic separation of extracted products. The method was optimized investigating the effects of several solvents, the volume added to the solid sample, and temperature programming of the ChromatoProbe DSI device. The best results for thermal desorption were found using toluene as an extraction solvent and heating the programmable temperature injector from room temperature to 300 degrees C with a temperature step of 105 degrees C. With the use of the optimized thermal desorption conditions, several components have been positively identified in the volatile fraction of the deposits: aromatics, antioxidants, and antioxidant degradation products. Moreover, this work highlighted the presence of diesel fuel in the VOM of the piston deposits and gave new facts on the absence of the role of diesel fuel in the deposit formation process. Most importantly, it opens the possibility of quickly performing the analysis of deposits with small amounts of samples while having a good separation of the volatiles