The bacterial pathogen Klebsiella pneumoniae is a cause of community-and hospital-acquired lung, urinary tract, and blood stream infections. A common contaminant of indwelling catheters, it is theorized that a common infection pathway for this organism is via shedding of aggregates off of biofilm colonies.In an effort to better understand bacterial proliferation in the host bloodstream, we develop a PDE model for the flocculation dynamics of Klebsiella pneumoniae in suspension. Existence and uniqueness results are provided, as well as a brief description of the numerical approximation scheme. We generate artificial data and illustrate the requirements to accurately identify proliferation, aggregation, and fragmentation of flocs in the experimental domain of interest.
Bifidobacteria play a vital role in human nutrition and health by shaping and maintaining the gut ecosystem. In order to exert a beneficial effect, a sufficient population of bifidobacteria must colonise the host. In this study, we developed a miniaturised high-throughput in vitro assay for assessing the colonising ability of bacterial strains in human cells. We also investigated a variety of components isolated from different milk sources for their ability to increase the adherence of Bifidobacterium longum subsp. infantis ATCC 15697, a common member of the gastrointestinal microbiota of breastfed infants, to HT-29 cells. Both conventional and miniaturised colonisation assays were employed to examine the effect of 13 different milk-derived powders on bacterial adherence, including positive controls which had previously resulted in increased bifidobacterial adherence (human milk oligosaccharides and a combination of 3′- and 6′-sialylactose) to intestinal cells. Immunoglobulin G enriched from bovine whey and goat milk oligosaccharides resulted in increased adhesion (3.3- and 8.3-fold, respectively) of B. infantis to the intestinal cells and the miniaturised and conventional assays were found to yield comparable and reproducible results. This study highlights the potential of certain milk components to favourably modulate adhesion of bifidobacteria to human intestinal cells.
The etiology of Crohn's disease (CD) is complex and involves both host susceptibility factors (i.e., the presence of particular genetic alleles) and environmental factors, including bacteria. In this regard, adherent-invasive Escherichia coli (AIEC), have recently emerged as an exciting potential etiological agent of CD. AIEC are distinguished from commensal strains of E. coli through their ability to adhere to and invade epithelial cells and replicate in macrophages. Recent molecular analyses have identified genes required for both invasion of epithelial cells and replication in the macrophage. However, these genetic studies, in combination with recent genome sequencing projects, have revealed that the pathogenesis of this group of bacteria cannot be explained by the presence of AIEC-specific genes. In this article, we review the role of AIEC as a pathobiont in the pathology of CD. We also describe the emerging link between AIEC and autophagy, and we propose a model for AIEC pathogenesis.
The Rcs phosphorelay is composed of RcsC, RcsD and the response regulator RcsB, and this signalling pathway has been implicated in virulence and biofilm formation in many enteric bacteria. It was previously shown that a mutation in rcsC resulted in defective biofilm formation in Escherichia coli [Ferrières, L. & Clarke, D. J. (2003) Mol Microbiol 50, 1665–1682]. To identify the molecular mechanisms underlying the observed biofilm defect we carried out a screen looking for suppressor mutants that restored biofilm formation in the rcsC mutant background. One of the mutants was identified to be in rprA, a gene encoding a small RNA molecule that is involved in the post-transcriptional control of the alternative sigma factor, σ S. The expression of rprA is regulated by the Rcs phosphorelay, and there are elevated σ S levels present in the rcsC mutant due to the overexpression of rprA in this background. Using different approaches, we have established that the increase in σ S levels is responsible for the biofilm defect. Therefore, the Rcs phosphorelay is involved in maintaining appropriate levels of σ S during biofilm formation in E. coli.
Techniques used in four major sand and gravel resource analyses in the UK are described. For each survey, an archive of pre-existing borehole data was assembled. Borehole distribution may be uneven and, in glaciated terrains, they may be concentrated in the valleys and absent from positive geomorphological features, which might represent the major resources. Satellite imagery may be useful for assessment of coastal resources and was also used to illustrate the environmental context of deposits but it is unreliable as a predictive tool in the UK. Geomorphological surveys provided a rapid cost-effective method for identifying potential resources, particularly in glaciated terrains with prominent landforms. Geophysical techniques were less successful. Seismic surveying was expensive and did not provide consistently accurate results. Resistivity surveys were used and an experiment was devised to assess their accuracy. For this, detailed logs were provided for ten boreholes to allow on-site instrument calibration, then another ten borehole locations were given but without geological data. Resistivity estimates at the latter borehole locations overestimated overburden by 39% and depth to bedrock by 340ut underestimated mineral thickness by 29%. Hydrogeological data were collected as part of the data bases and gave a broad indication of likely groundwater conditions existing in most resource areas. Resource criteria used in previous IMAU assessments are considered insufficiently stringent and, in particular, an upper limit for mineral of 40 0.000000ines is considered too high and a reduction to 20uggested. This would significantly reduce the volumes of some previously estimated resources. Within the areas surveyed here, the reduction in mineral volume would vary from 5 0n the Lleyn to 77 0n Harbury-Kineton. Planning analyses have been undertaken as part of three of these surveys and provide useful information on likely constraints to exploitation but they must avoid compromising the County Councils in their role as Minerals Planning Authorities. Techniques of data presentation are crucial to success in reaching a wider audience and the usefulness of three-dimensional diagrams is indicated.
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