The analysis of para-cresol production and tolerance in Clostridium difficile 027 and 012 strains

<p>Abstract</p> <p>Background</p> <p><it>Clostridium difficile </it>is the major cause of antibiotic associated diarrhoea and in recent years its increased prevalence has been linked to the emergence of hypervirulent clones such as the PCR-ribotype 027. Characteristically, <it>C. difficile </it>infection (CDI) occurs after treatment with broad-spectrum antibiotics, which disrupt the normal gut microflora and allow <it>C. difficile </it>to flourish. One of the relatively unique features of <it>C. difficile </it>is its ability to ferment tyrosine to <it>para</it>-cresol via the intermediate <it>para</it>-hydroxyphenylacetate (<it>p-</it>HPA). <it>P</it>-cresol is a phenolic compound with bacteriostatic properties which <it>C. difficile </it>can tolerate and may provide the organism with a competitive advantage over other gut microflora, enabling it to proliferate and cause CDI. It has been proposed that the <it>hpdBCA </it>operon, rarely found in other gut microflora, encodes the enzymes responsible for the conversion of <it>p-</it>HPA to <it>p</it>-cresol.</p> <p>Results</p> <p>We show that the PCR-ribotype 027 strain R20291 quantitatively produced more <it>p</it>-cresol <it>in-vitro </it>and was significantly more tolerant to <it>p</it>-cresol than the sequenced strain 630 (PCR-ribotype 012). Tyrosine conversion to <it>p</it>-HPA was only observed under certain conditions. We constructed gene inactivation mutants in the <it>hpdBCA </it>operon in strains R20291 and 630Δ<it>erm </it>which curtails their ability to produce <it>p</it>-cresol, confirming the role of these genes in <it>p-</it>cresol production. The mutants were equally able to tolerate <it>p</it>-cresol compared to the respective parent strains, suggesting that tolerance to <it>p</it>-cresol is not linked to its production.</p> <p>Conclusions</p> <p><it>C. difficile </it>converts tyrosine to <it>p</it>-cresol, utilising the <it>hpdBCA </it>operon in <it>C. difficile </it>strains 630 and R20291. The hypervirulent strain R20291 exhibits increased production of and tolerance to <it>p-</it>cresol, which may be a contributory factor to the virulence of this strain and other hypervirulent PCR-ribotype 027 strains.</p

Metabolic Profiling of an Echinostoma caproni Infection in the Mouse for Biomarker Discovery

Consumption of raw fish and other freshwater products can lead to unpleasant worm infections. Indeed, such worm infections are of growing public health and veterinary concern, but they are often neglected, partially explained by the difficulty of accurate diagnosis. In the present study we infected 12 mice with an intestinal worm (i.e., Echinostoma caproni) and collected blood, stool, and urine samples 7 times between 1 and 33 days after the infection. At the same time points, blood, stool, and urine were also sampled from 12 uninfected mice. These biofluid samples were examined with a spectrometer and data were analyzed with a multivariate approach. We observed important differences between the infected and the uninfected control animals. For example, we found an increased level of branched chain amino acids in the stool of infected mice and subsequent depletion in blood plasma. Additionally, we observed changes related to a disturbed intestinal bacterial composition, particularly in urine and stool. The combination of results from the three types of biofluids gave the most comprehensive characterization of an E. caproni infection in the mouse. Urine would be the biofluid of choice for diagnosis of an infection because the ease of sample collection and the high number and extent of changed metabolites

A metabolomic approach to assessing life-history traits in Caenorhabditis elegans

The proximate causes of ageing and the biological processes that determine lifespan are still unclear. However, many studies using model organisms have led to the identification of genes associated with longevity. While there is a clear link between changes in metabolism and changes in longevity, there has been relatively little ageing-related research that has measured metabolites directly. Metabolic profiling of low molecular weight metabolites (metabolomics) has an advantage over other 'omics' techniques, in that it directly samples the metabolic changes in an organism, and integrates information from changes at the gene, transcript and protein levels, as well as post-translational modification. This thesis demonstrates that metabolic profiling provides a new and useful phenotyping tool for studying ageing in the nematode Caenorhabditis elegans. Using both nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry (GC-MS), I have identified metabolites that are linked with long life. I have carried out the first characterisation of the C. elegans metabolome throughout both development and ageing. Comparing these metabolic changes in wild type worms with those seen in a long-lived mutant aid the understanding of when and how mutant worms acquire their long-lived phenotype. In addition to this, I have examined the effects on metabolism of a commonly used technique in C. elegans ageing research: the inhibition of DNA synthesis to maintain synchronous ageing populations. This provided a way to control for the effects of this technique when used in my work, but also demonstrated that its use may result in artefacts in data. I have also investigated the effect of mutation accumulation on the C. elegans metabolic profile. I have shown that metabolomics provides a way to obtain new phenotypes in this type of study, and novel information about the variation that occurs as a result of spontaneous mutation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Ageing with elegans : a research proposal to map healthspan pathways

Human longevity continues to increase world-wide, often accompanied by decreasing birth rates. As a larger fraction of the population thus gets older, the number of people suffering from disease or disability increases dramatically, presenting a major societal challenge. Healthy ageing has therefore been selected by EU policy makers as an important priority ; it benefits not only the elderly but also their direct environment and broader society, as well as the economy. The theme of healthy ageing figures prominently in the Horizon 2020 programme , which has launched several research and innovation actions (RIA), like "Understanding health, ageing and disease: determinants, risk factors and pathways" in the work programme on "Personalising healthcare". Here we present our research proposal entitled "ageing with elegans" (AwE), funded by this RIA, which aims for better understanding of the factors causing health and disease in ageing, and to develop evidence-based prevention, diagnostic, therapeutic and other strategies. The aim of this article, authored by the principal investigators of the 17 collaborating teams, is to describe briefly the rationale, aims, strategies and work packages of AwE for the purposes of sharing our ideas and plans with the biogerontological community in order to invite scientific feedback, suggestions, and criticism.Peer reviewe

Balanced harvest: concept, policies, evidence, and management implications

Balanced harvest has been proposed to reduce fishing impact on ecosystems while simultaneously maintaining or even increasing fishery yield. The concept has attracted broad interest, but also received criticisms. In this paper, we examine the theory, modelling studies, empirical evidence, the legal and policy frameworks, and management implications of balanced harvest. The examination reveals unresolved issues and challenges from both scientific and management perspectives. We summarize current knowledge and address common questions relevant to the idea. Major conclusions include: balanced harvest can be expressed in several ways and implemented on multiple levels, and with different approaches e.g. métier based management; it explicitly bridges fisheries and conservation goals in accordance with international legal and policy frameworks; modelling studies and limited empirical evidence reveal that balanced harvest can reduce fishing impact on ecosystem structure and increase the aggregate yield; the extent of balanced harvest is not purely a scientific question, but also a legal and social choice; a transition to balanced harvest may incur short-term economic costs, while in the long-term, economic results will vary across individual fisheries and for society overall; for its application, balanced harvest can be adopted at both strategic and tactical levels and need not be a full implementation, but could aim for a “partially-balanced” harvest. Further objective discussions and research on this subject are needed to move balanced harvest toward supporting a practical ecosystem approach to fisheries.</p

Balanced harvest : concept, policies, evidence, and management implications

Balanced harvest has been proposed to reduce fishing impact on ecosystems while simultaneously maintaining or even increasing fishery yield. The concept has attracted broad interest, but also received criticisms. In this paper, we examine the theory, modelling studies, empirical evidence, the legal and policy frameworks, and management implications of balanced harvest. The examination reveals unresolved issues and challenges from both scientific and management perspectives. We summarize current knowledge and address common questions relevant to the idea. Major conclusions include: balanced harvest can be expressed in several ways and implemented on multiple levels, and with different approaches e.g. métier based management; it explicitly bridges fisheries and conservation goals in accordance with international legal and policy frameworks; modelling studies and limited empirical evidence reveal that balanced harvest can reduce fishing impact on ecosystem structure and increase the aggregate yield; the extent of balanced harvest is not purely a scientific question, but also a legal and social choice; a transition to balanced harvest may incur short-term economic costs, while in the long-term, economic results will vary across individual fisheries and for society overall; for its application, balanced harvest can be adopted at both strategic and tactical levels and need not be a full implementation, but could aim for a “partially-balanced” harvest. Further objective discussions and research on this subject are needed to move balanced harvest toward supporting a practical ecosystem approach to fisheries

Balanced harvest: concept, policies, evidence, and management implications

Balanced harvest has been proposed to reduce fishing impact on ecosystems while simultaneously maintaining or even increasing fishery yield. The concept has attracted broad interest, but also received criticisms. In this paper, we examine the theory, modelling studies, empirical evidence, the legal and policy frameworks, and management implications of balanced harvest. The examination reveals unresolved issues and challenges from both scientific and management perspectives. We summarize current knowledge and address common questions relevant to the idea. Major conclusions include: balanced harvest can be expressed in several ways and implemented on multiple levels, and with different approaches e.g. métier based management; it explicitly bridges fisheries and conservation goals in accordance with international legal and policy frameworks; modelling studies and limited empirical evidence reveal that balanced harvest can reduce fishing impact on ecosystem structure and increase the aggregate yield; the extent of balanced harvest is not purely a scientific question, but also a legal and social choice; a transition to balanced harvest may incur short-term economic costs, while in the long-term, economic results will vary across individual fisheries and for society overall; for its application, balanced harvest can be adopted at both strategic and tactical levels and need not be a full implementation, but could aim for a “partially-balanced” harvest. Further objective discussions and research on this subject are needed to move balanced harvest toward supporting a practical ecosystem approach to fisheries