Dynamic screening of agricultural contaminants in freshwater ecosystems as part of amphibian biodiversity conservation

C

Towards a food web based control strategy to mitigate an amphibian panzootic in agricultural landscapes

While the emerging amphibian disease chytridiomycosis is causing dramatic and ongoing biodiversity losses worldwide, sustainable strategies to mitigate this global threat to amphibians are currently missing. We here propose a conceptual framework for a novel biological mitigation strategy based on the increasing evidence that naturally occurring micropredators, such as protists, rotifers and crustaceans, are capable of using zoospores of the chytrid pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal) as a food source under controlled laboratory conditions. Pathogen predation may serve as a cost-efficient way to prevent chytridiomycosis outbreaks under natural conditions by reducing zoospore densities and thereby infection loads. This predator-pathogen relationship is not an isolated interaction, but is embedded in the aquatic food web structure that interacts with a wide range of environmental factors. Amphibian breeding ponds are increasingly associated to agricultural landscapes due to ongoing land use occupancy for food production, exposing these water bodies to a variety of environmental stressors such as agrochemical pollution, nutrient enrichment and cattle trampling. Environmental stressors may affect the composition and abundance of aquatic communities, while they can also exert sublethal effects that may reduce the zoospore removal efficiency of micropredators. By carefully controlling environmental stressors, trophic interactions may be steered to optimize chytrid predation with the aim of reducing zoospore densities to such extent that hosts and pathogens can sustainably coexist. We present a scientific outline of this novel concept and provide a framework for ongoing research to develop a complete mitigation strategy against chytridiomycosis based on such food web control

Agreement of quantitative and qualitative antimicrobial susceptibility testing methodologies : the case of enrofloxacin and avian pathogenic escherichia coli

Avian pathogenicEscherichia coli(APEC) is the causal agent of colibacillosis, one of the most common bacterial infections in the poultry sector. Antimicrobial susceptibility testing (AST) is essential for rational and prudent antimicrobial therapy. Subsequently, uniformity in test results from the various testing methodologies used in diagnostic laboratories is pivotal. The aim of this study was therefore to evaluate the agreement between different AST methods in determining fluoroquinolone resistance in APEC. Twenty APEC isolates were selected and subjected to four different susceptibility tests: the quantitative microbroth dilution, agar dilution and gradient strip tests, and the qualitative disk diffusion method. The experiments were performed in triplicate. Categorical agreement, essential agreement and different errors were assessed. Moreover, agreement was also evaluated by calculating intraclass correlation coefficients (ICCs) for the quantitative tests and determining the Pearson correlation coefficients for the agreement between the disk diffusion method and the quantitative tests. Categorical agreement and essential agreement when compared with the microbroth technique ranged from 85-95% and 85-100%, respectively. No very major errors (false susceptible) and only one major error (false resistant) and minor errors (results involving an intermediary category) were detected. The calculated ICC values of the three quantitative tests fluctuated around 0.970 (range 0.940-0.988). There was a high negative correlation between the disk diffusion method and the other tests (correlation coefficients ranging from -0.979 to -0.940), indicating a clear inverse relationship between the minimum inhibitory concentration value and the zone diameter of growth inhibition. In conclusion, the overall agreement between the four different testing methodologies was very high. These results confirm the reliability of the disk diffusion and gradient strip test methods as substantiated alternatives, next to the gold standard agar and microbroth dilution, for fluoroquinolone susceptibility testing of APEC isolates

Presence of low virulence chytrid fungi could protect European amphibians from more deadly strains

Wildlife diseases are contributing to the current Earth’s sixth mass extinction; one disease, chytridiomycosis, has caused mass amphibian die-offs. While global spread of a hypervirulent lineage of the fungus Batrachochytrium dendrobatidis (BdGPL) causes unprecedented loss of vertebrate diversity by decimating amphibian populations, its impact on amphibian communities is highly variable across regions. Here, we combine field data with in vitro and in vivo trials that demonstrate the presence of a markedly diverse variety of low virulence isolates of BdGPL in northern European amphibian communities. Pre-exposure to some of these low virulence isolates protects against disease following subsequent exposure to highly virulent BdGPL in midwife toads (Alytes obstetricans) and alters infection dynamics of its sister species B. salamandrivorans in newts (Triturus marmoratus), but not in salamanders (Salamandra salamandra). The key role of pathogen virulence in the complex host-pathogen-environment interaction supports efforts to limit pathogen pollution in a globalized world

Metadata-oriented multimedia information retrieval : Pesquisa de informação multimedia orientada por meta-informação

Tese de mestr.. Gestão de Informação. Faculdade de Engenharia. Universidade do Porto. 199

Brucellar spondylodiscitis: case report

Brucellosis is a common zoonosis which still remains a major health problem in certain parts of the world. Osteoarticular involvement is the most frequent complication of brucellosis, in which the diagnosis of brucellar spondylodiscitis is often difficult since the clinical presentation may be obscured by many other conditions. Herein, we report an uncommon case of spondylodiscitis due to Brucella in a male who presented with abdominal pain. The diagnosis was established by positron emission tomography combined with computed tomography (PET/CT scan) and magnetic resonance followed by a confirmation on Brucella-agglutination test and positive culture of computed tomography (CT) guided punction fluid. This case report illustrates an atypical presentation of spondylitis and points out the difficulties in diagnosing the aetiological agens Brucella, and differentiating its specific features from tuberculosis

Hydrophobic high quality ring PMOs with an extremely high stability

Ordered mesoporous organosilicas with a high organic loading lead to a more hydrophobic character and can result in better mechanical, hydrothermal and chemical stability. In this paper, we first present an optimized synthesis method of periodic mesoporous organosilicas containing interconnected [Si(CH2)](3) rings in the presence of surfactant Brij-76. Therefore, two important synthesis parameters, which are the acid and surfactant concentration, were systematically varied. This optimization method results in highly ordered mesoporous materials with very high surface areas, high pore volumes, uniform cylindrical pores and thick walls. Further, it was found that the porosity can be controlled by the surfactant concentration without changing the pore diameter. In the second part, it is demonstrated that a post modification with HMDS or an auto-hydrophobization step leads to PMOs which are totally hydrophobic without losing their mesoporosity. In the last part, the impact of the hydrophobization on the (a) hydrothermal, (b) mechanical and (c) chemical stability is investigated. The results reveal that post modification with HMDS creates ordered materials that can withstand (a) steaming at 130 degrees C, (b) a mechanical compression of 272 MPa and (c) a treatment with 1 M NaOH for 2.5 h without any degradation of the silica network

Exploring proteomes and analyzing protein processing by mass spectrometric identification of sorted N-terminal peptides

Current non-gel techniques for analyzing proteomes rely heavily on mass spectrometric analysis of enzymatically digested protein mixtures. Prior to analysis, a highly complex peptide mixture is either separated on a multidimensional chromatographic system(1,2) or it is first reduced in complexity by isolating sets of representative peptides(3-8). Recently, we developed a peptide isolation procedure based on diagonal electrophoresis(9) and diagonal chromatography(10). We call it combined fractional diagonal chromatography (COFRADIC). In previous experiments, we used COFRADIC to identify more than 800 Escherichia coli proteins by tandem mass spectrometric (MS/MS) analysis of isolated methionine-containing peptides(11). Here, we describe a diagonal method to isolate N-terminal peptides. This reduces the complexity of the peptide sample, because each protein has one N terminus and is thus represented by only one peptide. In this new procedure, free amino groups in proteins are first blocked by acetylation(12) and then digested with trypsin. After reverse-phase (RP) chromatographic fractionation of the generated peptide mixture, internal peptides are blocked using 2,4,6-trinitrobenzenesulfonic acid (TNBS)(13,14); they display a strong hydrophobic shift and therefore segregate from the unaltered N-terminal peptides during a second identical separation step. N-terminal peptides can thereby be specifically collected for further liquid chromatography (LC)-MS/MS analysis. Omitting the acetylation step results in the isolation of non-lysine-containing N-terminal peptides from in vivo blocked proteins

MAPK-activated protein kinase 2-deficiency causes hyperacute tumor necrosis factor-induced inflammatory shock

Background: MAPK-activated protein kinase 2 (MK2) plays a pivotal role in the cell response to (inflammatory) stress. Among others, MK2 is known to be involved in the regulation of cytokine mRNA metabolism and regulation of actin cytoskeleton dynamics. Previously, MK2-deficient mice were shown to be highly resistant to LPS/D-Galactosamine-induced hepatitis. Additionally, research in various disease models has indicated the kinase as an interesting inhibitory drug target for various acute or chronic inflammatory diseases. Results: We show that in striking contrast to the known resistance of MK2-deficient mice to a challenge with LPS/D-Gal, a low dose of tumor necrosis factor (TNF) causes hyperacute mortality via an oxidative stress driven mechanism. We identified in vivo defects in the stress fiber response in endothelial cells, which could have resulted in reduced resistance of the endothelial barrier to deal with exposure to oxidative stress. In addition, MK2-deficient mice were found to be more sensitive to cecal ligation and puncture-induced sepsis. Conclusions: The capacity of the endothelial barrier to deal with inflammatory and oxidative stress is imperative to allow a regulated immune response and maintain endothelial barrier integrity. Our results indicate that, considering the central role of TNF in pro-inflammatory signaling, therapeutic strategies examining pharmacological inhibition of MK2 should take potentially dangerous side effects at the level of endothelial barrier integrity into account.Research was supported by the agency for Innovation by Science and Technology (IWT); Research Foundation Flanders (FWO); and Ghent University: Concerted Research Actions (GOA