Plant-associated symbiotic Burkholderia species lack hallmark strategies required in mammalian pathogenesis

Burkholderia is a diverse and dynamic genus, containing pathogenic species as well as species that form complex interactions with plants. Pathogenic strains, such as B. pseudomallei and B. mallei, can cause serious disease in mammals, while other Burkholderia strains are opportunistic pathogens, infecting humans or animals with a compromised immune system. Although some of the opportunistic Burkholderia pathogens are known to promote plant growth and even fix nitrogen, the risk of infection to infants, the elderly, and people who are immunocompromised has not only resulted in a restriction on their use, but has also limited the application of non-pathogenic, symbiotic species, several of which nodulate legume roots or have positive effects on plant growth. However, recent phylogenetic analyses have demonstrated that Burkholderia species separate into distinct lineages, suggesting the possibility for safe use of certain symbiotic species in agricultural contexts. A number of environmental strains that promote plant growth or degrade xenobiotics are also included in the symbiotic lineage. Many of these species have the potential to enhance agriculture in areas where fertilizers are not readily available and may serve in the future as inocula for crops growing in soils impacted by climate change. Here we address the pathogenic potential of several of the symbiotic Burkholderia strains using bioinformatics and functional tests. A series of infection experiments using Caenorhabditis elegans and HeLa cells, as well as genomic characterization of pathogenic loci, show that the risk of opportunistic infection by symbiotic strains such as B. tuberum is extremely low

Towards a Synthetic Chloroplast

The evolution of eukaryotic cells is widely agreed to have proceeded through a series of endosymbiotic events between larger cells and proteobacteria or cyanobacteria, leading to the formation of mitochondria or chloroplasts, respectively. Engineered endosymbiotic relationships between different species of cells are a valuable tool for synthetic biology, where engineered pathways based on two species could take advantage of the unique abilities of each mutualistic partner.We explored the possibility of using the photosynthetic bacterium Synechococcus elongatus PCC 7942 as a platform for studying evolutionary dynamics and for designing two-species synthetic biological systems. We observed that the cyanobacteria were relatively harmless to eukaryotic host cells compared to Escherichia coli when injected into the embryos of zebrafish, Danio rerio, or taken up by mammalian macrophages. In addition, when engineered with invasin from Yersinia pestis and listeriolysin O from Listeria monocytogenes, S. elongatus was able to invade cultured mammalian cells and divide inside macrophages.Our results show that it is possible to engineer photosynthetic bacteria to invade the cytoplasm of mammalian cells for further engineering and applications in synthetic biology. Engineered invasive but non-pathogenic or immunogenic photosynthetic bacteria have great potential as synthetic biological devices

Prophylactic antibiotic treatment in severe acute ischemic stroke: the Antimicrobial chemopRrophylaxis for Ischemic STrokE In MaceDonIa–Thrace Study (ARISTEIDIS)

Infections represent a leading cause of mortality in patients with acute ischemic stroke, but it is unclear whether prophylactic antibiotic treatment improves the outcome. We aimed to evaluate the effects of this treatment on infection incidence and short-term mortality. This was a pragmatic, prospective multicenter real-world analysis of previously independent consecutive patients with acute ischemic stroke who were >18 years, and who had at admission National Institutes of Health Stroke Scale (NIHSS) >11. Patients with infection at admission or during the preceding month, with axillary temperature at admission >37 °C, with chronic inflammatory diseases or under treatment with corticosteroids were excluded from the study. Among 110 patients (44.5 % males, 80.2 ± 6.8 years), 31 (28.2 %) received prophylactic antibiotic treatment, mostly cefuroxime (n = 21). Prophylactic antibiotic treatment was administered to 51.4 % of patients who developed infection, and to 16.4 % of patients who did not (p < 0.001). Independent predictors of infection were NIHSS at admission [relative risk (RR) 1.16, 95 % confidence interval (CI) 1.08–1.26, p < 0.001] and prophylactic antibiotic treatment (RR 5.84, 95 % CI 2.03–16.79, p < 0.001). The proportion of patients who received prophylactic antibiotic treatment did not differ between patients who died during hospitalization and those discharged, or between patients who died during hospitalization or during follow-up and those who were alive 3 months after discharge. Prophylactic administration of antibiotics in patients with severe acute ischemic stroke is associated with an increased risk of infection during hospitalization, and does not affect short-term mortality risk. © 2016, SIMI

High-density haplotype structure and association testing of the insulin-degrading enzyme (IDE) gene with type 2 diabetes in 4,206 people.

The insulin-degrading enzyme is responsible for the intracellular proteolysis of insulin. Its gene IDE is located on chromosome 10, in an area with suggestive linkage to type 2 diabetes and related phenotypes. Due to the impact of genetic variants of this gene in rodents and the function of its protein product, it has been proposed as a candidate gene for type 2 diabetes. Various groups have explored the role of the common genetic variation of IDE on insulin resistance and reported associations of various single nucleotide polymorphisms (SNPs) and haplotypes on both type 2 diabetes and glycemic traits. We sought to characterize the haplotype structure of IDE in detail and replicate the association of common variants with type 2 diabetes, fasting insulin, fasting glucose, and insulin resistance. We assessed linkage disequilibrium, selected single-marker and multimarker tags, and genotyped these markers in several case-control and family-based samples totalling 4,206 Caucasian individuals. We observed no statistically significant evidence of association between single-marker or multimarker tests in IDE and type 2 diabetes. Nominally significant differences in quantitative traits are consistent with statistical noise. We conclude that common genetic variation at IDE is unlikely to confer clinically significant risk of type 2 diabetes in Caucasians

Association testing of common variants in the insulin receptor substrate-1 gene (IRS1) with type 2 diabetes

Aims/hypothesis Activation of the insulin receptor substrate-1 (IRS1) is a key initial step in the insulin signalling pathway. Despite several reports of association of the G972R polymorphism in its gene IRS1 with type 2 diabetes, we and others have not observed this association in well-powered samples. However, other nearby variants might account for the putative association signal. Subjects and methods We characterised the haplotype map of IRS1 and selected 20 markers designed to capture common variations in the region. We genotyped this comprehensive set of markers in several family-based and case-control samples of European descent totalling 12,129 subjects. Results In an initial sample of 2,235 North American and Polish case-control pairs, the minor allele of the rs934167 polymorphism showed nominal evidence of association with type 2 diabetes (odds ratio [OR] 1.25, 95% CI 1.03-1.51, p=0.03). This association showed a trend in the same direction in 7,659 Scandinavian samples (OR 1.16, 95% CI 0.96-1.39, p=0.059). The combined OR was 1.20 (p=0.008), but statistical correction for the number of variants examined yielded a p value of 0.086. We detected no differences across rs934167 genotypes in insulin-related quantitative traits. Conclusion/interpretation Our data do not support an association of common variants in IRS1 with type 2 diabetes in populations of European descent

Common ABCB1 polymorphisms in Greek patients with chronic hepatitis C infection: A comparison with hyperlipidemic patients and the general population

Background Hepatitis C virus infectivity and replication efficiency appears to be dependent on the lipid content and organization of the plasma membrane of the host cell, as well as of the intracellular membranous web. As there is increasing awareness of a role played by the efflux pump ABCB1 (p-glycoprotein, P-gp) in lipid homeostasis, its function could be a determinant of chronic HCV infection. The aim of the present study was to examine and compare the distribution of common ABCB1 genotypes in patients with chronic HCV infection (n = 168), hyperlipidemic patients (n = 168) and a control group (n = 173), all from Greece. Methods Participants were genotyped for the ABCB12677G&amp;gt;T/A and 3435C&amp;gt;T polymorphisms with previously reported PCR-RFLP methods. Genotype and allele frequency distributions were compared between the three groups with the χ2 test of independence. Results The ABCB1 2677GG (ancestral) genotypes were significantly over-represented in patients with chronic hepatitis C compared to controls (39.3% vs. 26.6%, p = 0.015 according to the dominant model). A similar result was obtained when hyperlipidemic patients were compared to controls (45.2% vs. 26.6%, p &amp;lt; 0.001 according to the dominant model). Comparison of ABCB1 3435C&amp;gt;T genotype and allele distributions provided similar but not as significant differences. Genotype and allele distributions for both ABCB12677G&amp;gt;T/A and 3435C&amp;gt;T were very similar between HCV patients and hyperlipidemic patients. Conclusion Our findings imply an influence of ABCB1 polymorphisms on HCV infectivity, possibly through an effect on lipid homeostasis. © 2015 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved

<i>S. elongatus</i> can grow inside the macrophage cytoplasm.

<p>A.) Time lapse microscopy of macrophages infected with +inv+llo <i>S. elongatus</i> kept in the dark shows the gradual decrease in red autofluorescence over the course of 12 hours. In contrast, when kept in the light, B.) empty vector <i>S. elongatus</i> autofluorescence is observed to gradually decrease over the course of several days (top row), while a significant increase in red <i>S. elongatus</i> autofluorescence was observed in macrophages infected with inv llo <i>S. elongatus</i> for two days post-infection (bottom row). This fluorescence was observed to decrease after the third day of infection. C.) This change in fluorescence over time can be quantified as a change in background subtracted mean fluorescence in ImageJ and averaged over triplicate experiments. Empty vector (blue line) and +inv+llo <i>S. elongatus</i> (red line) show marked differences in growth when infected at similar densities of 1–2 bacterial cells per macrophage. D.) +inv+llo <i>S. elongatus</i> displayed infection density dependent growth rates in macrophages. Each line shows change in mean fluorescence in cells infected at a single starting density, ranging in multiples of two from fewer than one cell per macrophage to approximately 4 bacteria per macrophage. E.) Macrophage cell counts were variable across replicates and over the course of the experiment but displayed no significant difference between macrophages infected with empty vector <i>S. elongatus</i> at low (green line) or high density (blue line), or +inv+llo <i>S. elongatus</i> at low (red line) or high (yellow line) density. F.) When infected at low density of fewer than one bacteria per macrophage, <i>S. elongatus</i> division was observed during 18 hour time-lapse fluorescent microscopy in approximately 1% of macrophages observed, in particular those cells that contained more than one bacterial cell due to stochastic fluctuations.</p