2 resultados para economic impacts
em Glasgow Theses Service
New prophylactic and therapeutic treatments to combat pathogenic Enterohaemorrhagic Escherichia coli
Resumo:
Bacterial diarrhoeal diseases have significant influence on global human health, and are a leading cause of preventable death in the developing world. Enterohaemorrhagic Escherichia coli (EHEC), pathogenic strains of E. coli that carry potent toxins, have been associated with a high number of large-scale outbreaks caused by contaminated food and water sources. This pathotype produces diarrhoea and haemorrhagic colitis in infected humans, and in some patients leads to the development of haemolytic uremic syndrome (HUS), which can result in mortality and chronic kidney disease. A major obstacle to the treatment of EHEC infections is the increased risk of HUS development that is associated with antibiotic treatment, and rehydration and renal support are often the only options available. New treatments designed to prevent or clear E. coli infections and reduce symptoms of illness would therefore have large public health and economic impacts. The three main aims of this thesis were: to explore mouse models for pre-clinical evaluation in vivo of small compounds that inhibit a major EHEC colonisation factor, to assess the production and role of two proteins considered promising candidates for a broad-spectrum vaccine against pathogenic E. coli, and to investigate a novel compound that has recently been identified as a potential inhibitor of EHEC toxin production. As EHEC cannot be safely tested in humans due to the risk of HUS development, appropriate small animal models are required for in vivo testing of new drugs. A number of different mouse models have been developed to replicate different features of EHEC pathogenesis, several of which we investigated with a focus on colonisation mediated by the Type III Secretion System (T3SS), a needle-like structure that translocates bacterial proteins into host cells, resulting in a tight, intimate attachment between pathogen and host, aiding colonisation of the gastrointestinal tract. As E. coli models were found not to depend significantly on the T3SS for colonisation, the Citrobacter rodentium model, a natural mouse pathogen closely related to E. coli, was deemed the most suitable mouse model currently available for in vivo testing of T3SS-targeting compounds. Two bacterial proteins, EaeH (an outer membrane adhesin) and YghJ (a putative secreted lipoprotein), highly conserved surface-associated proteins recently identified as III protective antigens against E. coli infection of mice, were explored in order to determine their suitability as candidates for a human vaccine against pathogenic E. coli. We focused on the expression and function of these proteins in the EHEC O157:H7 EDL933 strain and the adherent-invasive E. coli (AIEC) LF82 strain. Although expression of EaeH by other E. coli pathotypes has recently been shown to be upregulated upon contact with host intestinal cells, no evidence of this upregulation could be demonstrated in our strains. Additionally, while YghJ was produced by the AIEC strain, it was not secreted by bacteria under conditions that other YghJ-expressing E. coli pathotypes do, despite the AIEC strain carrying all the genes required to encode the secretion system it is associated with. While our findings indicate that a vaccine that raises antibodies against EaeH and YghJ may have limited effect on the EHEC and AIEC strains we used, recent studies into these proteins in different E. coli pathogens have suggested they are still excellent candidates for a broadly effective vaccine against E. coli. Finally, we characterised a small lead compound, identified by high-throughput screening as a possible inhibitor of Shiga toxin expression. Shiga toxin production causes both the symptoms of illness and development of HUS, and thus reduction of toxin production, release, or binding to host receptors could therefore be an effective way to treat infections and decrease the risk of HUS. Inhibition of Shiga toxin production by this compound was confirmed, and was shown to be caused by an inhibitory effect on activation of the bacterial SOS response rather than on the Shiga toxin genes themselves. The bacterial target of this compound was identified as RecA, a major regulator of the SOS response, and we hypothesise that the compound binds covalently to its target, preventing oligomerisation of RecA into an activated filament. Altogether, the results presented here provide an improved understanding of these different approaches to combating EHEC infection, which will aid the development of safe and effective vaccines and anti-virulence treatments against EHEC.
Resumo:
Background: Community participation has become an integral part of many areas of public policy over the last two decades. For a variety of reasons, ranging from concerns about social cohesion and unrest to perceived failings in public services, governments in the UK and elsewhere have turned to communities as both a site of intervention and a potential solution. In contemporary policy, the shift to community is exemplified by the UK Government’s Big Society/Localism agenda and the Scottish Government’s emphasis on Community Empowerment. Through such policies, communities have been increasingly encouraged to help themselves in various ways, to work with public agencies in reshaping services, and to become more engaged in the democratic process. These developments have led some theorists to argue that responsibilities are being shifted from the state onto communities, representing a new form of 'government through community' (Rose, 1996; Imrie and Raco, 2003). Despite this policy development, there is surprisingly little evidence which demonstrates the outcomes of the different forms of community participation. This study attempts to address this gap in two ways. Firstly, it explores the ways in which community participation policy in Scotland and England are playing out in practice. And secondly, it assesses the outcomes of different forms of community participation taking place within these broad policy contexts. Methodology: The study employs an innovative combination of the two main theory-based evaluation methodologies, Theories of Change (ToC) and Realist Evaluation (RE), building on ideas generated by earlier applications of each approach (Blamey and Mackenzie, 2007). ToC methodology is used to analyse the national policy frameworks and the general approach of community organisations in six case studies, three in Scotland and three in England. The local evidence from the community organisations’ theories of change is then used to analyse and critique the assumptions which underlie the Localism and Community Empowerment policies. Alongside this, across the six case studies, a RE approach is utilised to examine the specific mechanisms which operate to deliver outcomes from community participation processes, and to explore the contextual factors which influence their operation. Given the innovative methodological approach, the study also engages in some focused reflection on the practicality and usefulness of combining ToC and RE approaches. Findings: The case studies provide significant evidence of the outcomes that community organisations can deliver through directly providing services or facilities, and through influencing public services. Important contextual factors in both countries include particular strengths within communities and positive relationships with at least part of the local state, although this often exists in parallel with elements of conflict. Notably this evidence suggests that the idea of responsibilisation needs to be examined in a more nuanced fashion, incorporating issues of risk and power, as well the active agency of communities and the local state. Thus communities may sometimes willingly take on responsibility in return for power, although this may also engender significant risk, with the balance between these three elements being significantly mediated by local government. The evidence also highlights the impacts of austerity on community participation, with cuts to local government budgets in particular increasing the degree of risk and responsibility for communities and reducing opportunities for power. Furthermore, the case studies demonstrate the importance of inequalities within and between communities, operating through a socio-economic gradient in community capacity. This has the potential to make community participation policy regressive as more affluent communities are more able to take advantage of additional powers and local authorities have less resource to support the capacity of more disadvantaged communities. For Localism in particular, the findings suggest that some of the ‘new community rights’ may provide opportunities for communities to gain power and generate positive social outcomes. However, the English case studies also highlight the substantial risks involved and the extent to which such opportunities are being undermined by austerity. The case studies suggest that cuts to local government budgets have the potential to undermine some aspects of Localism almost entirely, and that the very limited interest in inequalities means that Localism may be both ‘empowering the powerful’ (Hastings and Matthews, 2014) and further disempowering the powerless. For Community Empowerment, the study demonstrates the ways in which community organisations can gain power and deliver positive social outcomes within the broad policy framework. However, whilst Community Empowerment is ostensibly less regressive, there are still significant challenges to be addressed. In particular, the case studies highlight significant constraints on the notion that communities can ‘choose their own level of empowerment’, and the assumption of partnership working between communities and the local state needs to take into account the evidence of very mixed relationships in practice. Most importantly, whilst austerity has had more limited impacts on local government in Scotland so far, the projected cuts in this area may leave Community Empowerment vulnerable to the dangers of regressive impact highlighted for Localism. Methodologically, the study shows that ToC and RE can be practically applied together and that there may be significant benefits of the combination. ToC offers a productive framework for policy analysis and combining this with data derived from local ToCs provides a powerful lens through which to examine and critique the aims and assumptions of national policy. ToC models also provide a useful framework within which to identify specific causal mechanisms, using RE methodology and, again, the data from local ToC work can enable significant learning about ‘what works for whom in what circumstances’ (Pawson and Tilley, 1997).