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Silva, Neusely da. "Escherichia coli 0157:H7 em alimentos." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256596.
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Orientador: Fumio YokoyaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Doutorado
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Zin, Noraziah Mohamad. "Studies on escherichia coli 0157:H7 and its toxins." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366820.
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Garven, Sarah Jane. "Bovine dendritic cells & their interaction with E. coli 0157:H7." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/8741.
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E. coli O157:H7 is the most important serotype of enterohaemorrhagic E. coli (EHEC) which is of concern to public health worldwide. As a common cause of haemorrhagic colitis, EHEC infection can progress to life threatening sequelae including haemolytic uraemic syndrome (HUS) in humans. Human infection rates are higher in Scotland than found in the rest of the UK. Cattle are asymptomatic carriers of EHEC and are an important reservoir from which disease outbreaks can spread. The terminal rectum has been indicated as a site of E. coli O157:H7 colonisation in the bovine intestinal tract. This is the location of numerous lymphoid follicles which contain dendritic cells (DCs) which are professional antigen presenting cells and important directors of immune responses. DCs are likely to come into contact with EHEC and therefore could be key in this location for enabling EHEC to colonise the bovine host. The first aim of this project was to characterise dendritic cells within the bovine intestinal tract at various anatomical locations, including the terminal rectum, using immunohistochemistry techniques. Following this, work to extract and further phenotype dendritic cells from terminal rectal tissues was undertaken. Finally, a widely-used bovine dendritic cell model was employed to generate dendritic cells from circulating blood monocytes. This model was utilised to investigate the interactions of dendritic cells with EHEC strains compared with responses to bovine enterotoxigenic (ETEC) and bovine commensal E. coli strains. Early work identified that there are potentially numerous DCs within the bovine intestinal tissues and these cells were found in greater numbers at the terminal rectum. Protocols to extract and further characterise these cells were developed but proved inconsistent, with large variation between animals. Using the monocyte derived dendritic cells (moDCs), differences were observed between immunological responses to challenge with E. coli O157:H7 strains and bovine pathogenic or commensal E. coli strains. Cytokine production, cell surface molecule expression, cell phenotype and viability as well as intracellular bacterial counts were compared. The data presented here shows that the bovine moDCs respond differently to EHEC strains when compared with commensal or pathogenic E. coli in several key areas. This has important implications for the responses of the bovine host to various E. coli strains. This work also indicates that dendritic cells could be central to these responses and if studied further still, may hold the key to reducing the colonization and persistence of E. coli O157:H7 in cattle, and subsequent human disease outbreaks.
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Dlamini, Bhekisisa Chushuta. "Acid adaptation of Escherichia coli 0157:H7 in fermented goat milk." Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-02102009-102022.
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Paton, Neil. "Bovine epithelial cell responses to colonisation by Escherichia coli 0157:H7." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/29314.
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E. coli 0157:H7 was the first identified pathogen of a group that have come to be referred to as Enterohaemorrhagic E. coli (EHEC) and was identified in 1983 as being associated with Haemolytic ureamic syndrome (HUS). This bacterium carries the potent cytotoxin Shigalike toxin (Stx), also known as verotoxin, which through the inhibition of protein synthesis causes cell necrosis in the endothelium of the renal vasculature and this leads to the triad of symptoms - renal failure, thrombocytopenia and microangiopathic haemolytic anaemia. EHEC is also associated with Haemorrhagic colitis in humans as endothelium of both the colonic vasculature and the renal system express Gb3 receptors. These receptors bind the toxin and internalisation of the toxin allows the inhibition of protein synthesis. EHEC is a food borne zoonosis and its reservoir host is the bovine and faecal contamination of the environment, the food chain and direct contact with cattle are the most recognised routes for human infection to occur. The bovine host is asymptomatically colonised in the field and detection and removal is problematic, any future intervention strategy to remove this pathogen from the national herd is likely to be expensive and labour intensive. EHEC has a number of virulence factors that are involved in colonisation and proinflammatory responses. These were examined in a bovine model system. The flagellum was the only virulence factor that produced a proinflammatory response when measured by quantitative and traditional RTPCR. Commensal bacteria were unable to produce a response although one motile strain was included in the panel and was presumed to express flagella which were shown to be pro-inflammatory when associated with EHEC. In the host animal there is limited evidence for a pathological effect and to elucidate the mechanisms that explain this lack of response to pathogenic effects microarray was utilised to tease out these mechanisms. The data produced identified a limited set of genes that were differentially regulated including CyclinC Angiopoetin-1 like protein, Jumonji domain containing protein 2B, Zinc finger protein 161 and Est-lplike protein, all of which were thought to be involved in cell cycle regulation. Quantitative RTPCR was unable to confirm the data from the array; further work is therefore required to determine whether colonisation does in fact alter the expression of these genes. EHEC was therefore hypothesized to alter the proliferation rate within the epithelium and an immunohistochemical approach was used to assess this. Proliferating cell nuclear antigen (PCNA) was used as a marker to identify replicating cells and counts of cells in the epithelium demonstrated a reduction in proliferating cells in colonised epithelium. Further analysis suggested that retinoblastoma protein was a central protein that was involved in pathways influenced by the proteins already outlined. IHC was used to study this protein and differences in the number of cells expressing this protein and localisation within the cells. Retinoblastoma appears to be retained in the cytoplasm in colonised cattle which limits its ability to induce proliferation through release of E2F. It is suggested that E.coli 0157:H7 can manipulate the epithelial cell proliferation rate in the bovine host and increases the time that the bacterium is retained in the host. It was hoped that microarray data and QtRT-PCR would identify proteins involved in this phenotype but the lack of support from the real time data for targets identified by the array makes it impossible to conclude that these proteins are defiantly involved. This increase in time allows for a greater chance of spread to other host animals within the herd. Further work to clarify the details of this pathway will allow interventions which limit colonisation the National herd to be designed.
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Byrne, Caitriona Martina. "Survival and persistence of Escherichia coli 0157:H7 within meat production processes." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365916.
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Ding, Yajun Mustapha Azlin. "Transfer of Listera monocytogenes and Escherichia coli 0157:H7 during food processing." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/6071.
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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on Oct. 7, 2009). Thesis advisor: Dr. Azlin Mustapha. Includes bibliographical references.
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Bromberg, Renata. "Fatores que afetam a recuperação de celulas de Escherichia coli 0157:H7 termicamente injuriadas." [s.n.], 1997. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256612.
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Orientadores: Fumio Yokoya, Michael William PeckTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Um método popular de se prolongar a vida-de-prateleira de alimentos minimamente processados é através da utilização de tratamentos térmicos brandos e embalagem com atmosfera modificada (com baixas concentrações de oxigênio). Tradicionalmente, a eficácia dos tratamentos térmicos aplicados a estes alimentos é medida através da contagem em aerobiose das células injuriadas pelo calor. Contudo, no caso da bactéria Escheríchia coli 0157:H7, obtém-se uma melhor recuperação das células subletalmente injuriadas quando se utiliza técnicas estritamente anaeróbias. Estudou-se o efeito do tratamento térmico brando em células de E. Coli 0157H7 e as condições de recuperação da sua sensibilidade ao oxigênio em meio de cultura e em meio a base de alimentos. Células de E. Coli 0157:H7 em fase estacionária de crescimento, cultivadas em meio triptona de soja acrescido de 0,3% de extrato de levedura e 1% de glicose (TSYGB) a 30°C durante 24 horas, e submetidas a tratamento térmico a 59°C durante 5 minutos sob condições anaeróbias, recuperaram sua habilidade de crescer em presença de oxigênio em 6 horas. Similarmente, quando as células foram submetidas a tratamento térmico e mantidas em presença de 20% de oxigênio, estas apresentaram maior sensibilidade ao oxigênio, necessitando de um período maior de tempo para se recuperar do que as células mantidas em condições de anaerobiose (9 horas comparado a 6 horas). Células de E. coli 0157:H7 foram submetidas a tratamentos térmicos de letalidade equivalente a 55, 59 e 61 °C. Após tratamento térmico a 55°C por 100 minutos, as células necessitaram de mais de 20 horas para recuperar sua tolerância ao oxigênio, comparativamente a 6 e 2 horas para as células tratadas termicamente a 59°C por 5 minutos e a 61 °C por 1 minuto, respectivamente. Isto indica, que as células deste microrganismo recuperam sua sensibilidade ao oxigênio mais rapidamente após tratamentos térmicos mais curtos com temperaturas mais altas. Células de E. coli 0157:H7 submetidas a tratamento térmico a 59°C durante 5 minutos e incubadas a 10, 20 e 30°C, recuperaram sua tolerância ao oxigênio após aproximadamente 130, 50 e 6 horas, respectivamente. Contudo, quando mantidas a 5°C, estas células não recuperaram sua tolerância, sobrevivendo no mesmo nível durante o período de observação de 34 dias. A inclusão de 50% de dióxido de carbono ao meio de contagem, não apresentou efeito na recuperação das células sensíveis ao oxigênio, porém o aumento da concentração de oxigênio afetou a recuperação das células injuriadas. O choque térmico a 42°C durante 5 minutos, seguido de tratamento térmico a 59°C durante 5 minutos não influenciou a resistência térmica ou o reparo celular de E. coli 0157:H7. Entretanto, células deste microrganismo submetidas a choque térmico a 45°C durante 5 minutos, apresentaram um aumento em sua resistência térmica de cerca de 10 vezes, tanto em condições aeróbias como anaeróbias, não afetando porém, sua sensibilidade ao oxigênio. E. coli 0157:H7 foi inoculada em tubos contendo meios a base de alimentos, preparados em condições aeróbias e anaeróbias. Estes foram submetidos a tratamentos térmicos e incubados a 30°C. Foi verificada uma grande diferença na resistência térmica das células nos diferentes alimentos testados. Os valores Dsg-c nos tubos preparados em anaerobiose foram, para carne bovina 5,3 minutos, cogumelo 4 minutos, frango 3,7 minutos e de apenas 1,9 minutos para leite. Os valores D nos meios preparados em aerobiose foram similares aos obtidos no meio anaeróbio. Isto ocorreu porque os meios preparados em condições aeróbias apresentam potenciais de óxido-redução reduzidos, similares aos meios preparados em anaerobiose. Não se detectou crescimento de E. coli 0157:H7 em meios preparados a base de batata, brócolis e cenoura.
Abstract: A popular method of extending the shelf life of minimally processed foods is to subject the food to a mild heat treatment and package under a modified atmosphere (low level of oxygen). The effectiveness of the heat treatment is measured by aerobic enumeration of heat damaged cells. However, for Escherichia coli 0157:H7, the greatest recovery of sublethally damaged cells was obtained using strictly anaerobic techniques The effect of a mild heat treatment and the recovery conditions on oxygen sensitivity of E coli 0157:H7 cells was studied in media and foods. Stationary phase cells grown in tryptone soy agar with 0.3% yeast extract and 1 % glucose (TSYGB) at 30°C for 24 hours and heat treated at 59°C for 5 minutes recovered their ability to grow in oxygen in 6 hours when held in anaerobic conditions. Similarly when cells were heat treated and held in the presence of 20% oxygen, the cells were more sensitive to oxygen and took longer to recover than cells held in anaerobic conditions (9 hours compared with 6 hours). Cells of E coli 0157.H7 were subjected to heat treatments of equivalent lethality at 55, 59 and 61 °C. Following a heat treatment of 100 minutes at 55°C, cells took 20 hours to recover their tolerance to oxygen compared to 6 and 2 hours for cells heat treated for 5 minutes at 59°C and 1 minute at 61 °C, respectively. This shows that injured cells recover their oxygen tolerance faster after a short heat treatment at a higher temperature. Cells heat treated at 59°C for 5 minutes and held at 10, 20 and 30°C, recovered their oxygen tolerance after 130, 50 and 6 hours respectively. However, when held at 5°C, the cells did not recover their oxygen tolerance in 34 days. The inclusion of 50% carbon dioxide in the enumeration medium had no effect on the recovery of oxygen sensitive cells but oxygen concentration affected the recovery of injured cells A heat shock of 5 minutes at 42°C had no effect on heat resistance or recovery of damaged cells. However, 5 minutes at 45°C before a heat treatment of 5 minutes at 59°C increased the heat resistance of E. coli 0157:H7 by 10 fold but had no effect on its oxygen sensitivity. E. coli 0157:H7 was inoculated into tubes of food media prepared aerobically and anaerobicallly and given a heat treatment before incubating at 30°C. There was a large difference in heat resistance of cells in the different foods tested. Dsg-c in anaerobically prepared beef was 5.3 minutes, in mushroom, 4.0 minutes, in chicken, 3.7 minutes and in milk only 1.9 minutes. D values in aerobically prepared media were similar to those in anaerobic media. This was because aerobically prepared media had very low redox potentials, similar to those of the anaerobically prepared media. Growth of E. coli 0157:H7 was not detected in broccoli, carrot or potato media.
Doutorado
Doutor em Ciência de Alimentos
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Naylor, Stuart Warren. "Colonisation and persistence of Escherichia coli 0157:H7 in the bovine gastro-intestinal tract." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/27109.
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The principal aim during this study was to develop appropriate in vitro and in vivo systems to examine colonisation mechanisms of E. coli O157:H7 in the bovine GIT. An adherence assay on cultured tissue explants was developed to compare the ability of different aspects of E. coli O157:H7 adherence. In two separate experiments the contribution of intimate attachment, thought to be essential for virulence in humans, was assessed. The ability to intimately attach did not affect the level of E. coli O157:H7 adherence to bovine intestinal epithelium in vitro. A strain lacking the genes required for intimate attachment however exhibited enhanced adherence to bovine Peyer’s patch. The other strains did not exhibit tropism for any of the tissue type examined. The most relevant system to assess the behaviour of E. coli O157:H7 is within its natural host. Persistent colonisation of weaned calves was achieved for a number of isolates marked by nalidixic acid resistance, including a Stx negative strain that colonised at a similar level and duration to the equivalent Stx positive strain. At the conclusion of each calf colonisation experiment, those individuals still shedding the organism were examined under necropsy to determine its distribution. The first attempts failed to recover the organism in significant numbers at any site examined despite it being present in ante-mortem faeces. One explanation was that the organism was multiplying primarily in the distal rectum. Further necropsies revealed that the organism was colonising the mucosal surface of the distal 3 cm of the rectum via intimate attachment and confirmed that this phenomenon was indeed typical of persistently colonised calves. This small region contained a high density of lymphoid tissue.
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Emmerson, James R. "Tagging of the type three secretion system basal apparatus of enterohaemorrhagic Escherichia coli 0157:H7." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/30180.
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The aim of this project was to label inner membrane basal apparatus proteins with fluorescent markers or immunogenic tags in order to investigate their function, regulation and localization. Cloning strategies were designed to insert tags at the 3’ end of eight genes encoding putative inner membrane proteins and to use these fusions to replace the wild type sequences by allelic exchange. From the eight strategies, escR and escU were taken forward to produce five EHEC O157:H7 strains. One strain contained EscR labelled at the C-terminus with an HA (haemagglutinin) epitope tag and the other four strains contained different labelled versions of EscU. Work with these strains demonstrated that the T3SS could not be visualized using fluorescence microscopy. However, Western blot analysis did show that the EscU protein was cleaved into 30kDa and 10kDa peptides, both of which localized to the membrane fraction of the bacterial cell. This cleavage was most likely occurring at the conserved cleavage site NPTH. Interestingly all the mutant strains constructed did not secrete a detectable level of EspD, apart from one fusion that had previously been shown to cleave the tag from EscU. This indicated that, despite the small size of the HA tag, all the tags interfered with the function of EscR or EscU. Fusions to the 10kDa fragment of EscU, along with a deletion of this domain, were used to elucidate its function in the T3SS. All the EscU mutants did not form EspA filaments, secrete EspD at wild type levels or secrete detectable levels of Tir, whilst the expression from the LEE1-5 promoters remained unaffected. These phenotypes could not be restored upon supplying the 10kDa peptide in trans. It is proposed that the uncleaved EscU protein is needed to secrete EscF. After a defined period EscU is cleaved (possibly auto-catalytically) and this allows the secretion of EspA, B and D. The lack of wild type EscU in the mutant strains may not allow EscF to be secreted or assembled correctly and this in turn leads to the inhibition of EspA, B and D translocation. It was evident that even minimal changes were not tolerated and inhibited secretion by the system. Future research will have to proceed with either alternative target proteins or the generation of high affinity antibodies coupled with sensitive imaging technology.
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Dundas, Stephanie. "The 1996 central Scotland outbreak of Escheria coli 0157:H7 : investigation of clinical presentations and consequences." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/23332.
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In 1996 a large outbreak of Escherichia coli (E. coli) 0157 occurred in central Scotland. The outbreak recorded the largest number of adults with HUS and consequently the largest number of deaths, ever attributed to E. coli 0157. This unfortunate event provided opportunity to investigate severe acute disease and the chronic sequelae of infection. The retrospective studies aimed to assess host factors associated with the development of the haemolytic uraemic syndrome (HUS), to identify the earliest laboratory predictors of HUS, to develop a community monitoring protocol able to detect those with early HUS, to define the role of therapeutic plasma exchange (TPE) in the treatment of adults with HUS and to determine genetically mediated inflammatory responses associated with the severity of acute disease. The studies of chronic disease investigated renal function abnormalities in cases surviving HUS, and gastrointestinal complications and quality of life (QOL) in all cases. 512 cases were provisionally identified and 270 were confirmed by stool culture. 120 cases were admitted to hospital, 34 developed HUS and 17 died. Children and older adults were at greatest risk of HUS. However high white cell count (WCC) at presentation was as least as good a predictor of HUS as age. Acquired risk factors for HUS were low gastric acid and antibiotic therapy prior to symptom onset. 186 patients were assessed for blood group markers (ABO, Lewis and P). Blood group O and absent or weak expression of the PI erythrocyte antigen were associated with HUS. Very high levels of TNFa, implicated in the pathogenesis of HUS, were produced by leucocytes of P-negative individuals. Adults in Lanarkshire who developed HUS were treated with TPE, which is unproven and controversial in the context of E. coli 0157. The mortality associated with HUS was 45%, which compares favorably with previously reported mortality of 88%. Therefore TPE appears to be a promising treatment. Thirty per cent of children develop chronic renal disease following VTEC induced HUS but there was no information on the renal outcome of adults. In Lanarkshire 12 of 22 adults with HUS survived the acute illness. To the third anniversary chronic renal disease was demonstrated in all; one progressed to ESRD, three developed CRF and eight had clear evidence of renal insufficiency. Comparison with a control group confirmed that these changes could not simply be attributed to age. Prospective investigation determined the prevalence of irritable bowel syndrome (IBS) after E. coli 0157 infection and its impact QOL. On the second and third anniversaries of infection IBS was significantly higher in cases compared to matched controls. Almost forty per cent of cases developed new IBS within three years of infection. Cases with IBS had significantly lower SF-36 scores in all scales particularly those reflecting mental health. Therefore IBS is common after E. coli 0157 with a detrimental effect on QOL. This thesis provides new insight into the pathogenesis and clinical consequences of disease due to E. coli 0157, particularly in adults a previously undocumented group.
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Mori, Julie Y., and University of Lethbridge Faculty of Arts and Science. "Prevalence and survival of Escherichia coli 0157:H7 and Salmonella spp. in surface waters of Southern Alberta." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2001, 2001. http://hdl.handle.net/10133/137.
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E. coli 0157:H7 were isolated from 0.86% (n=1520) water samples and Salmonella species from 6.04% (n=1456) samples collected within the Oldman River watershed in southern Alberta. Peak prevalence of E. coli0157:H7 in July 2000 was 6.3% (n=48). Peak prevalence of Salmonella was 16.2% (n=11) in August 1999 and 33.% (n=42) in July 2000. Prevalence was greater in water from some sampling locations than from others. In non-filtered surface water E. coli0157:H7 and S. typhimurium numbers decreased significantly faster at 20 degrees celsius than at 10 degrees celsius (P=0.000); however this difference did not exist when the same water was filtered (P=0.439). Pathogen survival in one water sample was greater when it was filtered (0.2um pore) than when it was not filtered even though there were no autochthonous bacteria in the water prior to filtration.xi, 268 leaves ; 28 cm.
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Middleton, Karen Elizabeth. "Investigation of the effect of acids and detergents on the biocide susceptibility of Escherichia coli 0157:H7." Thesis, University of Wolverhampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288936.
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Wang, Chenbo. "Evaluation of the antimicrobial activity of a bifidobacteria mix against Escherichia coli 0157:H7 under aerobic conditions." Master's thesis, Mississippi State : Mississippi State University, 2006. http://library.msstate.edu/etd/show.asp?etd=etd-04112006-164012.
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Xu, Chuanling Huang Tung-Shi. "Decontamination of Escherichia coli 0157:H7 and Salmonella in lettuce, chicken, and apples by chlorine dioxide and ultrasound." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Thesis/XU_CHUANLING_6.pdf.
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Murano, Elsa Alina. "The effect of heat shock, growth atmosphere, and recovery atmosphere on the survival of Escherichia coli 0157:H7 to heat." Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39239.
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Reinhard, Robert G. "Analysis of Campylobacter jejuni, Campylobacter coli, Salmonella, Klebsiella pneumoniae, and Escherichia coli 0157:H7 in fresh hand picked blue crab (Callinectes sapidus) meat." Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/44250.
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Silveira, Josete Baialardi. "Investigação de Escherichia coli O157: H7 em carne moída no Estado do Rio Grande do Sul, Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/24802.
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As Escherichia (E.) coli produtoras de toxinas Shiga (STEC) compõem um dos mais importantes grupos de patógenos alimentares do mundo. Dentre as STEC, a E. coli O157:H7 tem sido a mais amplamente estudada, uma vez que pode causar diarréia sanguinolenta, anemia hemolítica, síndrome urêmica hemolítica (HUS) e púrpura trombótica trombocitopênica (TTP), sendo que a carne bovina tem sido um dos principais veículos desse microrganismo. O objetivo deste estudo foi investigar a presença de E. coli O157:H7 em amostras de carne moída coletadas no Estado do Rio Grande do Sul (RS), sul do Brasil. Para tanto, 95 amostras de carne moída foram coletadas em diferentes municípios do RS. Dentre essas amostras, três isolados foram identificadas como prováveis E. coli O157:H7, segundo os testes recomendados pelo USDA/FSIS. Nesses métodos as cepas cresceram em meio TSB adicionado de novobiocina e casaminoácido, foram positivas para o teste de “screening” utilizando anticorpos específicos, desenvolveram colônias típicas nos meios SMAC (MacConkey sorbitol) e SMAC-CT (Cefixina-telurito), após terem sido submetidas à separação imunomagnética (IMS), aglutinaram o anti-soro para a E. coli O157 e não apresentaram atividade de ß-glucoronidase. Após a caracterização genotípica por PCR Multiplex, investigando genes de virulência (rfbO157, stx1 e stx2), no Laboratório de referência para a vigilância regional de HUS e diarréias sanguinolentas no cone sul, do Ministério da Saúde da Argentina (INEI-ANLIS), os resultados apontaram que os três isolados foram negativos para os fatores de virulência, não produziram Shiga toxinas, não sendo classificados como E. coli 0157:H7. Cabe ressaltar que a caracterização genotípica dessas cepas dificilmente é realizada em indústrias de alimentos, e mesmo resultados falso-positivos para E. coli O157, como os demonstrados nesse trabalho, poderiam afetar significativamente o comércio nacional e internacional de carne bovina brasileira.The Shiga toxin-producing Escherichia coli (STEC) is one of the most important food pathogen groups worldwide. Among the STEC, E. coli O157:H7 has been the most widely studied, once it may cause bloody or nonbloody diarrhea, hemolytic anemia, hemolytic uremic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP), being beef one of the main carriers of this microorganism. The aim of the present study was to investigate the presence of E. coli O157:H7 in ground beef samples collected in the State of Rio Grande do Sul (RS), Southern Brazil. Thus, 95 ground beef samples were collected in different cities of RS. Among the samples, three isolates were identified as probable E. coli O157:H7, according to tests recommended by USDA/FSIS. In these methods, the strains grew in TSB medium added to novobiocine and casamino acid, were positive in the screening test using specific antibodies, developed typical colonies in SMAC (MacConkey sorbitol) and SMAC-CT (Cefixime tellurite) media, after being subjected to Immunomagnetic Separation (IMS), agglutinated the antiserum to E. coli O157 and did not show ß-glucoronidase activity. After the genotypic characterization by PCR Multiplex, investigating virulence genes (rfbO157, stx1 and stx2), at the Reference laboratory for regional surveillance of HUS and bloody diarrheas in the Southern Cone, from the Ministry of Health of Argentina (INEI-ANLIS), the results demonstrated that the three isolates were negative for the virulence factors, did not produce Shiga toxins, not being classified as E. coli 0157:H7. It is worth mentioning that the genotypic characterization of these strains is hardly performed in food industries, and even false-positive results for E. coli O157, as the ones presented in this study, could significantly affect the national and international trade of Brazilian beef.
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Smith, Jeffrey V. "Evaluation of Levulinic Acid for Topical Decontamination of Meat Surfaces." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1009.
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Experiments were performed to investigate the effects of wash treatments, consisting of hot water, 2% lactic, 2% acetic, or 2% levulinic acid, for decontamination of pathogenic bacteria previously inoculated onto meat surfaces, to inhibit growth of pathogenic bacteria inoculated onto previously washed meat surfaces, and on the organoleptic quality of sliced turkey roll and beef trim. Acid washes were no more effective at reducing Escherichia coli O157:H7 on beef plate, Listeria monocytogenes on sliced turkey roll, and Salmonella on pork belly than was water wash. Only lactic acid treatment was more effective than water at reducing Salmonella on chicken skin, but by less than 1 log CFU/cm2. Increasing wash temperatures with 2% levulinic acid did not reduce E. coli O157:H7 on beef plate. Organic acid washes did not protect against growth of L. monocytogenes and E. coli O157:H7. Acetic acid prevented growth of Salmonella, but only on chicken skin. Organic acid spray treatments of sliced turkey roll and beef trim did not affect consumer liking of turkey roll or cooked ground beef patties. Acid treatments had some effect on instrumental color measurements, but these appear to have little practical significance. Overall, washing with 2% organic acid solutions was no more effective at reducing pathogenic bacteria on meat surfaces than washing with water.
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Jackson, Kerry. "RT-PCR : a potential solution to the detection of viable-but-non-culturable Escherichia Coli 0157:H7 in the environment." Thesis, University of East London, 2004. http://roar.uel.ac.uk/3882/.
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Despite evidence that selective enrichment inhibits the recovery of stressed E. coli O157, the nature of the effect of selective agents on the pathogen has not been identified to date. Initial studies were completed to elucidate the nature of the response of E. coli O157: H7 12900 to selective agents. Two-dimensional gel electrophoresis was used to evaluate the effect of selective agents on gene expression. Selective agents reduce the recovery of viable-but non-culturable pathogens such as E. coli O157, which has implications for the efficacy of cultural isolation techniques. A sensitive and accurate identification technique is required and RT-PCR may facilitate the detection of viable STEC in quality control, environmental and clinical samples. Conditions that positively regulate virulence genes could be utilised to induce the transcription of these genes in viable-but-non-culturable bacteria and the subsequent detection of STEC specific virulence gene transcripts would provide evidence that samples contain infective STEC. The work reported here was completed with an aim to developing such an RT-PCR assay. Although the stx genes are obvious targets, toxigenic strains could not be employed in the present study due to the absence of a category three facility. Consequently, RT-PCR assays were designed to target the pO157 hlyA and katP genes and studies were completed with non-toxigenic E. coliOlSl: H7 NCTC 12900. E. coli O157: H7 NCTC 12900 lacks the stx genes but appears to survive as well as toxigenic E. coli O157 strains despite its non-toxigenic phenotype (Bolton et al, 1999). Other non-toxigenic E. coli 0157 strains are available, but NCTC 12900 is sold commercially and is recommended for use in quality control studies as the sole representative of STEC strains in a panel of other intestinal pathogens (www.phls.co.uk/labservices/nctc/qcrefsets.htm). Consequently, although the use of virulent clinical strains would have provided definitive evidence concerning the factors regulating hlyA and katP, E. coli O157: H7 NCTC 12900 was considered a suitable model for use in developing and assessing initial RT-PCR based viability assays. The work reported in subsequent chapters aimed to identify conditions that can be employed to initiate hlyA and katP transcription in the laboratory, facilitating the development and optimisation of an RT-PCR assay to detect viable-butnon- culturable E. coli 0157 in environmental samples.
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Cavalcante, Daniel Augusto. "Avaliação do tratamento com agua ozonizada para higienização de alface (Lactuca sativa)." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254839.
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Orientador: Marcelo CristianiniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: A etapa de sanitização é critica e de suma importância para a qualidade microbiológica de vegetais. ÿ importante que o sanitizante seja além de eficaz, seguro do ponto de vista toxicológico. O uso do ozÃ'nio durante o processamento de vegetais prolonga a vida de prateleira, preserva os atributos sensoriais e não produz resÃduos tóxicos. O objetivo deste trabalho foi estudar a eficiência o ozÃ'nio como sanitizante em hortaliças folhosas. Em um primeiro momento foi verificada a ação do sanitizante in vitro em Escherichia coli O157:H7 e Bacillus subtilis. O ozÃ'nio foi utilizado nas concentrações de 0,6, 0,8 e 1,0 mg L-1 nos tempos de 1, 3 e 5 minutos para cada concentração. Na seqüência observou-se a ação de água ozonizada durante um minuto na sanitização de alface americana inoculada com E. coli O157:H7 na concentração de 1,0 mgL-1 e, para completar o estudo, foi verificado o comportamento da hortaliça durante dez dias de armazenamento a 2ºC, sob ação de 1,0 mg L-1 de água ozonizada nos tempos de 1, 2 e 3 minutos. No estudo in vitro a E. coli O157:H7 e o Bacillus subtilis, no tempo de 3 minutos de exposição a 1,0 mg L-1 de água ozonizada, apresentaram uma redução de 6,6 e 6,3 ciclos logarÃtmicos, respectivamente. A atuação de 1,0 mgL-1 de água ozonizada aplicada durante 1,0 minuto em alface americana inoculada intencionalmente com E. coli O157:H7 apresentou uma redução média de 3,2 ciclos logarÃtmicos. No trabalho de vida de prateleira a alface permaneceu com menos de 3 NMP g-1 de Coliformes termotolerantes durante os 10 dias de tempo de estocagem nos tempos de 1, 2 e 3 minutos, após ser sanitizada com água ozonizada na concentração de 1,0 mgL-1, enquanto que as alfaces tratadas apenas com água corrente apresentaram, no último dia de estocagem, uma população de 1,1x104 NMP g-1 do mesmo microorganismo. Os resultados demonstram que o ozÃ'nio na concentração de 1,0 mgL-1 no tempo de 1 minuto é capaz de manter a qualidade microbiológica de alface americana dentro dos padrões higiênicos vigentes
Abstract: The sanitization is a critical stage for the microbiological quality of vegetables. It�s important that the sanitizer has effectiveness, and most be safe of the toxicological point of view. The use of ozone during the process of vegetables contributes to extend their shelf life, to preserve their sensorial attributes without producing toxic residues. The objective of this work was to study the potential of ozone as sanitizer in vegetables. In a first moment, the action of the sanitizer in vitro was verified in Escherichia coli O157:H7 and Bacillus subtlis. The ozone was used at concentrations of 0,6, 0,8 and 1,0 mg L-1 in times of 1, 3 and 5 minutes for each concentration. In the sequence the action of 1,0 mg L-1 of ozone water was observed during one minute in the sanitization of iceberg lettuce inoculated with E. coli O157:H7 and, to complete, the behavior of the vegetable was verified during ten days of storage at 2ºC, by the action of 1,0 mg L-1 of ozone water in times of 1, 2 and 3 minutes. In the study in vitro, the E. coli O157:H7 and the Bacillus subtilis, exposed for 3 minutes to 1,0 mg L-1 of ozone water, presented a reduction of 6,6 and 6,3 logarithmic cycles, respectively. The performance of 1,0 mg L-1 of ozone water applied for 1,0 minutes in Iceberg lettuce inoculated intentionally with E. coli O157:H7 presented a medium reduction of 3,2 logarithmic cycles. Concerning to shelf life the lettuce stayed with less than 3 MPN g-1 of Coliforms thermtolerants during the 10 days of storage in the times, after being sanitized with ozone water 1, 2 and 3 minutes in the concentration of 1,0mg L-1. On the other hand, the lettuce treated only with current water presented, in the last day of storage, a population of 1,1x104 MPN g-1 of the same microorganism. The results demonstrate that the ozone in the concentration of 1,0 mg L-1 in the time of 1 minute is capable to maintain the microbiological quality of iceberg lettuce inside of the effective hygienic patterns
Mestrado
Mestre em Tecnologia de Alimentos
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Manhani, Maria Raquel. "Desempenho da metodologia para isolomento e contagem de Escherichia coli 0157:H7 em leite e queijo e sua ocorrencia em queijo minas frescal produzido comercialmente." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255121.
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Orientador: Mauro Faber de Freitas LeitãoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: A etapa inicial deste trabalho consistiu na avaliação da resistência de uma cepa de Escherichia colí 0157:H7 e da microbiota contaminante de queijo Minas frescaI a antibióticos utilizados para conferir seletividade a meios de isolamento dessa bactéria. Observou-se que E colí 0157:H7 mostrou sensibilidade a concentrações de novobiocina superiores a 30 mg/L, sendo desaconselhável o uso de 100 mg/L, conforme preconizado em alguns meios de isolamento. Como o microrganismo mostrou-se menos tolerante à combinação de três antibióticos (cefixima a 0,05 mg/L, cefsuloqina a 10 mg/L e vancomicina a 8 mg/L) do que a microbiota contaminante do queijo frescal, tornou-se questionável a indicação do uso desses antibióticos para conferir seletividade aos meios de isolamento da bactéria. Em outra etapa foram avaliados os meios seletivos MacConkey sorbitol modificado, HC de acordo com 8zabo et aI. (1986), Rainbow 0157, EMB modificado e 8039 modificado, suplementados ou não com cefixima (0,05 mg/L) e telurito de potássio (2,5 mg/L), na contagem de Ecolí 0157:H7, inoculada experimentalmente em amostras de queijo Minas frescal e de leite, submetidas ou não a tratamento térmico. Os resultados revelaram a inadequação de todos esses meios nas contagens de amostras apresentando elevada contaminação (sem tratamento térmico). Nas amostras com contaminação baixa (tratadas termicamente), os meios HC e 8039 modificado, ambos suplementados, revelaram desempenho superior na análise de queijo (95,9 e 95,0 % de recuperação, respectivamente). Na análise de leite, o HC foi o mais eficiente, levando a 85,3% de recuperação. A técnica do Número Mais Provável revelou-se deficiente e pouco prática na contagem de E colí 0157:H7 em amostras de queijo, não representando, portanto, uma alternativa recomendável. Na avaliação qualitativa de Ecolí 0157:H7 foram avaliados os enriquecimentos em caldo BPW + 3 antibióticos, segundo Blanco et aI. (1996), em meio mEC+n segundo Okrend & Rose (1989), em meio mT8B segundo Padhye & Ooyle (1991), além do método proposto pelo FOA (1998) e o método imunoenzimático TECRA@. Na análise de amostras de queijo Minas frescal inoculadas experimentalmente, nenhum dos sistemas revelou desempenho altamente satisfatório. No entanto, entre as metodologias clássicas testadas, a do FDA mostrou-se superior, enquanto o método TECRA@foi aquele que, comparativamente, possibilitou a maior porcentagem de isolamentos e menor índice de resultados falso-negativos. Na análise de 60 amostras de queijo Minas frescal, submetidas ou não a inspeção federal, nenhuma delas revelou a presença de E. coli 0157:H7. Os resultados obtidos indicaram a necessidade de se aperfeiç.oar a metodologia para a pesquisa deste patógeno em alimentos, principalmente naqueles cuja microbiota contaminante apresenta-se em números elevados
Abstract: In a first experiment, it was evaluated the tolerance of Escheríchía colí 0157:H7 and natural contaminants found in Minas frescaI cheese to antibiotics used in selective culture media. It was noticed that E. colí 0157:H7 exhibited low tolerance to novobiocin concentrations above 30 mg/L, although the use of 100 mg/L is indicated in some isolation media. The microorganism was less tolerant to antibiotic combination (cefixime at 0,05 mg/L, cefsulodin at 1O mg/L and vancomincin at 8 mg/L) when compared to the natural contaminant cheese microflora what could be a drawback concerning the use of these agents in selective culture media. In a second experiment, the selective media MacConkey sorbitol (modified), HC according to Szabo (1990), Rainbow 0157, modified EMB and modified S039, supplemented or not with cefixime (0,05 mg/L) and potassium telurite (2,5 mg/L) were evaluated for E. colí 0157:H7 counting, with the bacterium inoculated in Minas frescal cheese and milk samples, both submitted or not to thermal treatment. Ali the tested media were inadequate when used for bacterial counts in the samples with high natural contamination (without thermal treatment). However, when the cheese samples with lower contamination were analyzed, the media HC and modified S039, both supplemented, showed superior performance (95,9 and 95,0% recovery, respectively). In milk analysis, HC medium was the most efficient (85,3% recovery). The Most Probable Number technique showed an inadequate performance for E. colí 0157:H7 counts. For the qualitative evaluation of E. coli 0157:H7 it was evaluated BPW+3 antibiotics broth according to Blanco et a/. (1996), mEC+n (Okrend & Rose, 1989), mTSB (Padhye & Ooyle, 1991), FOA proposed method (1998) and the immunoenzimatic method TECRA@.None of the tested methods showed superior performance for E. calí 0157:H7 recovery in inoculated cheese samples in the presence of the natural microflora. However the FDA method was the most efficient among the classical ones, while the TECRA@ assay was the best concerning E. calí 0157:H7 recovery and no false negative results. The results suggest the need for improvment in the methodology for E. calí
Mestrado
Mestre em Tecnologia de Alimentos
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COSTA, Joice Vinhal. "PERFIS DE ERIC-PCR DE Escherichia coli E E. coli O157:H7 EM MEIAS-CARCAÇAS BOVINAS." Universidade Federal de Goiás, 2008. http://repositorio.bc.ufg.br/tede/handle/tde/913.
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Previous issue date: 2008-08-27There are different sorotypes of Escherichia coli responsable for enteric disfunctions, and in the most of time those are related with meat consume or contaminated food that had not been cooked with an efficient thermal treatment before been ingested. In Brazil there aren t inform data of possible outbreaks caused by E. coli O157:H7, but this pathogen has been frequently isolated from cattle s feces, and it was recently isolated from bovine carcass at two slaughterhouses in Goiás. The present study has the objective to characterize by ERIC-PCR E. coli and E. coli O157:H7 detected at bovine carcass surfaces and check the power of this methodology to identify different isolates of E. coli and E. coli O157:H7. ERIC-PCR was used to characterize 111 samples, and it was obtained 32 fingerprints separated in 90 isolates of E. coli and eight fingerprints separated in 16 isolates of E. coli O157:H7. From the total of 111 samples, two isolates of E. coli and five of E. coli O157:H7 were non-tipables. The fingerprints varies from one to 18 bands. The discrimination between the samples was high, showing the big power of ERIC-PCR to discriminate isolates from one specie. The discriminatory index between E. coli and E. coli O157:H7 obtained was 0,96.
São diferentes os sorotipos de Escherichia coli responsáveis por distúrbios entéricos, muitas vezes relacionados com o consumo de carne ou alimentos que foram contaminados e não passaram por tratamento térmico eficiente antes de serem ingeridos. No Brasil não há dados sobre possíveis surtos causados por E. coli O157:H7, mas este patógeno vem sendo frequentemente encontrado em fezes bovinas e recentemente foi isolado de meias carcaças quentes e resfriadas bovinas destinadas à exportação no Estado de Goiás. O presente trabalho objetivou identificar os perfis de ERIC-PCR em E. coli e E. coli O157:H7 isoladas de superfícies de meias-carcaças quentes e resfriadas de bovinos de dois matadouros-frigoríficos de Goiás além de verificar a capacidade de discriminação desta metodologia. A técnica de ERIC-PCR foi utilizada na caracterização molecular das 111 amostras analisadas, sendo obtidos 32 perfis distribuídos em 90 cepas de E. coli e oito perfis distribuídos em 16 cepas de E. coli O157:H7. De um total de 111 amostras, duas cepas de E. coli e cinco de E. coli O157:H7 eram não-tipáveis. Os perfis de ERIC-PCR de E. coli variavam de um a 18 fragmentos. A discriminação entre as cepas de E. coli e E. coli O157:H7 pela técnica utilizada foi alta, mostrando a grande capacidade da técnica de ERIC-PCR em discriminar cepas de uma mesma espécie. O índice de discriminação entre E. coli e E. coli O157:H7 foi de 0,96
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HANSON, JAMES F. "CHARACTERIZATION OF NEUTRALIZING RESPONSES TO ANTHRAX TOXINS AND ISOLATION AND CHARACTERIZATION OF THE SHIGA-TOXIN ENCODING PHAGE OF ESCHERICHIA COLI 0157:H7." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1093017639.
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Cameron, Pamela. "The cytotoxic and inflammatory effects of E. coli 0157:H7 : the role of stress-activated protein kinases and nuclear factor kappa B." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366792.
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Teixeira, Junia Pacheco. "Efeito das proteinas do soro de leite sobre a colonização de Escherichia coli 0157:H7 na mucosa intestinal de camundongos Balb/C." Universidade Federal de Minas Gerais, 2008. http://hdl.handle.net/1843/FRPO-7KXHBZ.
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The effect of dietary whey protein concentrate on adhesion and colonization of enterohemorrhagic Escherichia coli O157:H7 in small intestine of Balb/C mice was available. Eight groups of the six females each one, had been separate and had randomly and received diet standard (AIN93G) (control group) and modified (AIN93 modified with addition from the fractions: alpha-lactalbumin and beta-lactoglobulin and total whey protein concentrate - WPC) and water ad libitum per seven days. The blunt groups had received aliquot from 0,5ml of E. coli O157: H7 (ATCC 43895), in the concentration of 7 x 1010 UFC/ml by means of gavage cannula. The animals had been examined clinically and sacrificed, in 8º experimental day, as recommendations of the bioethics committee (CETEA/UFMG). The samples of the intestinal portions had been submitted to the histopathology and morphometry. The statistical analyses had been carried through by the Test t-Student and by test ANOVA ONE WAY including analysis of variance and test of multiple comparison according to Tukey (Software GraphPad Prism 3.0.3® - San Diego HERE). The fractions beta-lactoglobulin and alpha-lactalbumin had protective effect on the intestinal vilosity of the distal part on the jejune and the ileum (p< 0,05), respectively, in Balb/C mice infected by E. coli 0157: H7. On the other hand, the WPC did not demonstrate protective effect on the intestinal vilosity. The whey protein presents great potential
for the control of intestinal infections caused by E. coli 0157: H7Este trabalho teve por objetivo avaliar o efeito protetor das frações protéicas do soro do leite sobre as vilosidades intestinais de camundongos Balb/C, infectados por Escherichia coli 0157:H7 amostra ATCC 43895. Oito grupos, compostos por seis fêmeas cada um, foram separados aleatoriamente e receberam dieta padrão (AIN93G) (grupo controle) e modificada (AIN93 modificada com adição das frações: alfa-lactalbumina, beta-lactoglobulina e concentrado protéico total) e água ad libitum por sete dias. Os grupos desafiados receberam alíquotas de 0,5ml de E. coli O157: H7, na concentração de 7 x 1010UFC/ml por meio de cânula de gavagem. Os animais foram acompanhados clinicamente e sacrificados, no 8º dia experimental, conforme recomendações do CETEA/UFMG. As amostras das porções intestinais foram submetidas à histopatologia e morfometria. As análises estatísticas foram realizadas pela técnica de pareamento através do Teste t-Student e pelo teste ANOVA ONE WAY incluindo análise de variância e teste de comparação múltipla segundo Tukey (Software GraphPad Prism 3.0.3® - San Diego CA). As frações beta-lactoglobulina e alfa-lactalbumina exerceram efeito protetor sobre as vilosidades intestinais do jejuno distal e íleo (p < 0,05), respectivamente, em camundongos Balb/C infectados por E. coli 0157:H7. Por outro lado, o concentrado protéico total (WPC) não demonstrou efeito protetor sobre as vilosidades intestinais. O soro do leite apresenta grande potencial para o controle de infecções intestinais causadas por E. coli 0157:H7
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Sheibani, Sara. "Comparison of the efficiency of two bio-pasteurization systems to eliminate escherichia coli 0157:H7 and salmonella enterica subsp. enterica serovar typhimurium in manure." Master's thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24608/24608.pdf.
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Sheibani, Sara. "Comparison of the efficiency of two bio-pasteurization systems to eliminate Escherichia coli 0157:H7 and Salmonella enterica subsp.enterica serovar Typhimurium in manure." Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24608/24608.pdf.
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Roberts, Alison K'Ann. "The Effect of Sorbic Acid on the Survival oOf Escherichia coli 0157:H7, Salmonella, Listeria monocytogenes, and Staphylococcus aureus on Shredded Cheddar and Mozzarella Cheese." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31440.
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The objective of this study was to determine the effectiveness of sorbic acid in inhibiting Escherichia coli 0157:H7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus on shredded cheddar and mozzarella cheese over 70 days storage. Samples of cheese were inoculated and placed into bags with a sorbic acid (0, 0.1, 0.15, 0.2 and 0.3 %) and anti caking agent mixture and stored at 10â aC. Each variable was enumerated after 0,14,28,42,56, and 70 days of storage. Survival of E. coli 0157:H7 showed no significant difference from control in either cheese. There were significantly lower Salmonella counts for days 14 to 42 on mozzarella cheese. No significant differences in survival were found for cheddar cheese. There were significantly lower counts noted in L. monocytogenes, and S. aureus in mozzarella. Though no significant differences were found over time in the cheddar, most of the sorbate concentrations exhibited lower counts than control on days 14 and 28. Overall, in the presence of sorbic acid there was a more rapid decline in numbers of each test organism, especially against L. monocytogenes, and S. aureus for both high and low moisture cheeses.Master of Science
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Solecki, Olivia. "Explaining the urban and rural differences of Escherichia coli 0157 human infection in Grampian." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25203.
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Ownis, Ali A. "Verocytotoxin expression by E. coli O157:H7." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343149.
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Silagyi, Karen Suzanne. "Biofilm formation by Escherichia coli O157:H7." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7806.
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Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Nutrition and Food Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Nqunq, Sphamandla. "Optical and microarray silver-gold based sensors for the detection of e.coli 0157:h7 in seawater." University of the Western Cape, 2021. http://hdl.handle.net/11394/8256.
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>Magister Scientiae - MScRecently researchers reported that nanoparticles functionalised through chemical methods possess risks to the environment and to the human health since they use hazardous chemicals and produce toxic waste. The increasing demand of nanomaterials for application in the field of science require an alternative method for synthesis of nanomaterials that are environmentally friendly, eco-friendly and non-toxic. The present study describes the green synthesis method for functionalisation of nanomaterials. Green synthesis methods are considered as a novel approach for functionalisation of nanoparticles using biological sources.
2022
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Braoudaki, Maria. "Antibiotic and biocide resistaance in Salmonella enterica and Escherichia coli 0157." Thesis, Aston University, 2004. http://publications.aston.ac.uk/11016/.
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Bacterial resistance to antibiotics and biocides is a prevalent problem, which may be exacerbated by the commonplace and often unnecessary inclusion of biocides into domestic products. Addition of antimicrobials, to domestic disinfectants has raised concern about promoting microbial resistance and potential cross-resistance to therapeutic antibiotics. This study investigated the potential for resistance in Salmonella enterica serovars Enteritidis, Typhimurium, Virchow and Escherichia call 0157 to commonly used biocides, to identify mechanisms underlying resistance and whether these provided cross-resistance to antibiotics. Salmonella enterica and E. coli 0157 strains were serially exposed to sub-inhibitory. concentrations of erythromycin (ERY), benzalkonium chloride (BKC), chlorhexidine hydrochloride (CHX)and triclosan (TLN). Once resistance was achieved permeability changes in the outer membrane, including LPS, cell surface charge and hydrophobicityand the presence of,an active efflux were investigated as possible resistance candidates. Thin layer chromatography (TLC) and Gas chromatography (GC) were carried out to examine fatty acid and lipid changes in E. coli 0157 isolates with reduced susceptibility to TLN. Cross-resistance was studied by the Stoke's method and standard microdilution assays. Examination of the outer membrane proteins and LPS did not reveal any significant changes between parent and resistant strains. The hydrophobicity of the cells increased as the cells were passaged and became less. susceptible. An active efflux system was the most likely mechanism of resistance in all strains tested and a fab1 mutation was associated with E. coli 0157 resistant to TLN isolates. In all isolates investigated the resistance was stable for over 30 passages in biocide-free media. A high degree of cross-resistance was obtained in TLN-resjstant Escherichia coli 0157 strains, which repeatedly exerted decreased susceptibility to various antimicrobials, including chloramphenicol, erythromycin, imipenem, tetracycline and trimethoprirn:, as well as to various biocides. The results of this laboratory-based investigation suggest that it is possible for microorganisms to become resistant to biocides when repeatedly exposed to sublethal concentrations. This may be especially the case in the domestic environment where administration of biocides is poorly controlled. Eventually it could lead to the undesirable situation of resident strains becoming resistant to disinfection and cross resistant to other antimicrobials.
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Wales, Andrew Derek. "Studies on Escherichia coli O157:H7 in sheep." Thesis, University of Bristol, 2002. http://hdl.handle.net/1983/63ae6bc6-8e5d-43fb-9ede-594711a03357.
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Escherichia coli 0157: 1-17is a significant human pathogent hat persistsi n asymptomatic animal hosts. It forms a characteristic attachment, the attaching-effacing (AE) lesion, on cell monolayers in vitro and in the intestine in some animal models. Cattle and sheep are asymptomatic carriers of E. coli 0157: H7 and sources of the organism for humans. The present studies examined the persistence of several strains of E. coli 0157: H7 in orally inoculated sheep, and attempted to correlate persistence with features of the strains in vitro and in vivo. A particular hypothesis tested was that adhesion of the bacterium to the intestinal mucosa is a significant mechanism for persistence in animal hosts. Host- and strain-dependentv ariation in the persistente xcretion of E. cola 0157: H7 was observed. Correlations could not be discerned between the persistence of the various bacterial strains and the results of a range of phenotypic tests. The ability of E. coli 0157: H7 to form AE attachments to the large intestinal mucosa in sheep of up to six months of age was demonstrated. No consistent site of persistence of E. coli 0157: H7 within the ovine alimentary tract was found, and AE lesions were not detected in sheep which were persistently excreting the organism. However, commensal bacteria, including E. coli 026, were seen to have formed AE attachments on the large intestinal mucosa. It was concluded that the attachment of E. coli 0157: H7 to the large intestinal mucosa by AE lesion formation may have a role in persistent carriage, but that persistence of the bacterium in the ovine intestine is probably influenced by additional bacterial and host factors. The potential value of interference in the formation of AE lesions, to reduce the prevalence of E. coli 0157: H7 excretion by sheep and other ruminants, merits further investigation.
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Hallewell, Jennyka, and University of Lethbridge Faculty of Arts and Science. "Shiga toxin-producing bacteriophage in Escherichia coli O157:H7." Thesis, Lethbridge, Alta. : University of Lethbridge, Deptartment of Biochemistry, 2008, 2008. http://hdl.handle.net/10133/776.
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Shiga toxin-producing E. coli (STEC) including E. coli O157:H7 are potential food and water borne zoonotic bacterial pathogens capable of causing outbreaks of severe illness in humans. The virulence of E. coli O157:H7 strains may be related to the type of Stx produced and several Stx2 variants have been identified which appear to differ in their ability to cause disease. Two lineages exist within O157 strains where lineage I is associated mainly with human and bovine isolates and lineage II is associated mainly with bovine isolates. The goal of this study was to identify and characterize a lineage II EC970520 Stx2c phage and determine if variations in the phage compared to Stx2 phage found within the lineage I strain, EDL933, can result in differences in virulence observed between the lineages. This study suggests: 1) that the lineage II strain EC970520 contains a highly heterogeneous Stx2c variant phage; 2) that location of integration of the phage within the genome of a bacterium may be important for host selection; 3) that EC970520 Stx2c phage genes are lineage II specific but only a subset of EDL933 phage genes are lineage I specific; 4) that differences in the stability of phages within bacteria contribute to the evolution of new pathogens; 5) that variation in phage genes can be used to detect different strains of E. coli O157:H7 and other STEC; and 6)that the type of phage may result in phenotypic differences between lineages and occurrence of human disease. Results of this study indicate that lineage II strains may be less virulent than lineage I strains due to specific genetic differences and the ability to release phage which is important to the evolution of new pathogenic strains.xv, 162 leaves : ill. ; 29 cm.
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Urabi, Iftikhar. "Virulence factors of verotoxin-producing Escherichia coli O157:H7." Thesis, University of Warwick, 1993. http://wrap.warwick.ac.uk/104210/.
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Escherichia coli O157:H7 is one of several E.coli serotypes that produce Verocytotoxins (VTs); they are collectively called "Verocytotoxin-producing E.coli" (VTEC). VTEC are medically important bacteria which have been implicated in cases of haemorrhagic colitis and haemolytic uremic syndrome. Two distinct VTs are known, VT1 and VT2, and variants of VT2 have been described. They are potent exotoxins which kill mammalian cells by inhibiting protein synthesis. The virulence properties manifested by these organisms include the elaboration of VT1 or VT2 (or both), and the adherence to intestinal epithelial cells via an attaching-effacing mechanism. Many strains carry a 60 MDa plasmid which is thought to be involved in adhesion. Initial data demonstrated that the VTEC O157:H7 isolates under study possess two virulence factors, production of VTs and adherence to epithelial cells. However, effort has focused on investigating bacterial adherence, largely because attachment of VTEC is thought to be an important pathogenic mechanism since it allows colonisation, which facilitates toxin delivery, and adherence may be sufficient to cause diarrhoea in experimental animals in the absence of VTs. Moreover, a better understanding of the adhesion mechanism should help in finding ways by which adherence can be prevented. Since the bacterial-mucosal interactions are complicated in vivo by events and conditions that are not reproduced in current in vitro tests, a series of experiments were designed to investigate bacterial adherence to epithelial cells under conditions which are as close as possible to the in vivo situation. Significantly different data were obtained when quantitative adherence assays were performed under different physiological conditions, (different growth media, growth phase, pH values, low iron and oxygen limitation). Both iron-restricted, and oxygen- limited media induced a reduction in the final cell density, however, anaerobiosis significantly increased the adherence capacity of VTEC O157:H7 to HeLa cells while low iron caused a reduction in the number of adherent bacteria. Actively growing cells in the exponential phase were more adherent to HeLa cells than cells in the stationary phase. Since adhesion results from mutual recognition of surface structures from both the bacterial cell (adhesin) and the host cell (receptor), the bacterial cell envelope, and the HeLa cell outer membranes were investigated. Results of the preliminary characterisation of VTEC 0157:H7 surface components which have been implicated as adherence factors indicated that these strains are not fimbriated, however, they have been shown to be capable of binding to epithelial cells. Further studies were therefore, focused upon the identification of nonfimbrial adhesin(s). The use of competitive inhibitors, such as bacterial outer membrane extracts (OMPs), isolated lipopolysaccharides (LPS) and rabbit antisera to the H-7 flagella, OMPs, and LPS suggested that the role of H-7 flagella is insignificant, the LPS may in part be involved, but the OMPs seemed to have the major role in mediating attachment of O157:H7 to HeLa cells. The expression of OMPs under variable cultural conditions was examined, and significant differences were detected by the SDS-PAGE analysis of these extracts. The expression and repression of certain proteins was apparent under anaerobiosis, iron-restriction, different pH values and different bacterial growth phases. HeLa cell outer membranes were studied to identify the receptors on the host cell. Purified outer membranes were analysed by SDS-PAGE and used as inhibitors of bacterial adherence. Two proteins were identified by immunoblotting as a potential receptors.
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Wetzel, Amy Noel. "Studies in Shiga toxin-producing Escherichia coli O157:H7 determination of factors contributing to the dissemination of Escherichia coli O157:H7 among dairy farms /." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133239436.
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Snedeker, Kate Grayston. "Analysing Escherichia coli 0157 outbreaks in Scotland, Canada and the United States of America." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/25210.
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It was found that most outbreak and case trends between 1996 and 2004 in Scotland, 1996 and 2003 in Canada, and 1998 and 2004 in the United States could be described using simple linear models. In each of the three countries, the inability to fit simple linear models to particular trends could generally be ascribed to the effect of one or two disproportionately large outbreaks, which tended to act as outliers in models, and to low number of data points when data was split by mode of transmission. In Scotland there were statistically significant decreases over time in the number of sporadic cases, the number of foodborne cases and the number of ill case per outbreak, while in United States, the trend in the number of ill cases from outbreaks decreased statistically significantly. Lastly, in Canada, a statistically significant increase exists in the trends in the number of outbreaks, both overall and in those spread person to person and by water. When the trends in the number of outbreaks, ill cases and outbreak size were compared between countries there were few statistically significant differences. The analyses of the trends provide the first statistical analysis of temporal trends in outbreaks within countries and one of the very first comparisons of E. coli O157 between countries. Analyses of the primary and secondary cases in outbreaks suggested that approximately 19% of outbreak cases are secondary. In addition there were very few statistically significant differences in secondary or primary case characteristics between countries, with the results suggesting that median age and mode of secondary transmission, but not country are important in determining the rate of secondary cases in an outbreak.
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Flockhart, Allen Forrest. "Analysis of O-island deletions in Escherichia coli O157:H7." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/8154.
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Escherichia coli (E. coli) are a diverse species of bacteria that reside, often harmoniously and beneficially, in the gastrointestinal tracts of humans and other mammals. However, some strains are associated with serious intestinal and extra-intestinal disease and are considered pathogens. The main differences between strains of these different E. coli pathotypes can be explained by the acquisition of genetic information introduced by mobile genetic elements, in particular bacteriophage. In enterohaemorrhagic E. coli (EHEC) O157:H7 strain EDL933, a pathotype of E. coli containing prophage-encoded Shiga toxins associated with severe gastrointestinal and systemic disease in humans, these horizontally acquired elements have been termed O-islands (OIs) and include both fully functional and cryptic prophages. The overall aim of this research was to try and determine what these OIs are actually doing for the bacteria. Systems pertinent in the life cycle and virulence of this pathogen were therefore investigated by phenotypically screening a large library of OI deletions in EHEC strain TUV93-0, a Shiga toxin-negative derivative strain of EDL933, and then comparing these with the parent strain. These analyses highlighted a subset of OIs with the potential to regulate motility and type III secretion (T3S), the latter being an essential colonisation factor for EHEC that is encoded by the locus of enterocyte effacement (LEE). Deletion of OI-51, a 14.93 Kb cryptic prophage designated as CP-933C, significantly reduced persistence of faecal shedding in sheep and levels of T3S expression in vitro. Cloning and complementation together with targeted allelic replacements in OI-51 identified a novel positive regulator of the LEE, encoded by ecs1581 in the sequenced E. coli O157:H7 strain Sakai that is present but not annotated in the EDL933 sequence. Functionally important residues of ECs1581 were identified by site-directed mutagenesis based on phenotypic variants present in strains from different E. coli pathotypes, including strains not harbouring a LEE-encoded T3S system. This regulator was subsequently termed RgdR based on a motif demonstrated to be important for stimulation of gene expression from LEE1. Purified RgdR protein was able to form multiple complexes on a PCR generated LEE1 promoter fragment, and activation of this operon appeared to require this DNA binding capacity as a non-T3S inducing variant was unable to bind this same LEE1 promoter fragment. RgdR did not directly activate LEE1 transcription in vitro, nor did it activate transcription by relieving H-NS repression as proposed for the global regulator Ler (LEE-encoded regulator). However, RgdR activation did require a wild type LEE1 promoter and the Ler auto-induction cycle to induce LEE2-5 expression and T3S. RgdR was able to increase binding to Congo red and was capable of repressing bacterial motility. Further analyses demonstrated that RgdR did not regulate T3S and cell motility via GrlA (global regulator of LEE activator) and QseC (quorum sensing E. coli regulator C), two established regulators in E. coli that control LEE gene expression and motility in conjunction with their partners, GrlR (global regulator of LEE repressor) and QseB (quorum sensing E. coli regulator B) respectively. RgdR is therefore identified as a novel regulator able to co-ordinate T3S and motility expression. This research has identified OI-51 as being important for EHEC O157:H7 colonisation in sheep and has identified a completely new family of small bacterial regulators that control surface factor expression in E. coli.
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Herold, Sylvia. "Modulation der Genexpression von Escherichia coli O157:H7 durch Norfloxacin." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1137946605371-64953.
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Shiga Toxin produzierende Escherichia coli (STEC) sind wichtige Erreger von Lebensmittelinfektionen und gelten als Hauptverursacher für die Ausbildung einer hämorrhagischen Colitis und dem lebensbedrohlichen hämolytisch-urämischen Syndrom. Als Hauptvirulenzfaktor und wichtigstes Charakteristikum der STEC wird die Fähigkeit angesehen, Shiga Toxine (Stx) zu produzieren. Die genetische Information für deren Produktion ist im Genom lambdoider Prophagen kodiert. Eine Antibiotikatherapie bei STEC-assoziierten Infektionen wird sehr kontrovers diskutiert, da sowohl die Produktion der Stx als auch die Freisetzung der Bakteriophagen in vitro durch antibiotisch wirkende Substanzen stimuliert werden kann. Der enterohämorrhagische E. coli O157:H7 Stamm EDL933 beherbergt insgesamt 18 lambdoide Prophagen und prophagenähnliche Elemente, darunter den Stx1-kodierenden Phagen CP-933V und den Stx2-kodierenden Phagen BP-933W. Ziel der vorliegenden Arbeit war es, den Einfluss des Gyrasehemmers Norfloxacin auf das Gesamttranskriptom von EDL933 mit Hilfe der DNA-Microarraytechnologie und unter Verwendung des MWG E. coli O157 Arrays umfassend zu untersuchen und insbesondere die Expression der Prophagengene zu analysieren. Hierfür wurde der E. coli O157:H7 Stamm EDL933 mit 200 ng/ml Norfloxacin inkubiert, Gesamt-RNA isoliert und diese mittels reverser Transkription in cDNA synthetisiert, wobei ein Einbau von fluoreszenzmarkierten Nukleotiden erfolgte. Diese cDNA wurde mit den auf dem E. coli O157 Array befindlichen Oligonukleotiden hybridisiert. Die Auswertung der Fluoreszenzintensitäten ermöglicht eine Analyse der Genexpression. Infolge der Induktion von EDL933 mit 200 ng/ml Norfloxacin zeigten 118 Spots eine Hochregulation und 122 eine Deregulation von Genen an. Bei genauerer Betrachtung resultierte auf Grund der Inkubation mit Norfloxacin eine erhöhte Expression von 52 Genen der Stx-kodierenden Phagen CP-933V und BP-933W. Insbesondere erfolgte eine erhöhte Regulation von Genen der späten Region des BP-933W. Das stxA2-Gen wurde dabei im Vergleich zur nicht-induzierten Kultur 158-fach stärker exprimiert. Im Falle des Stx1-Phagen wiesen nur einige Gene der frühen Region eine gesteigerte Genaktivität auf. Auffallend war die Hochregulation einzelner Gene der nicht Stx-kodierenden Phagen. Gene des Primärstoffwechsels, u. a. Gene der Aminosäurebiosynthese, des Energiehaushaltes und der Zellteilung zeigten eine verminderte Genaktivität nach Induktion. Diese Ergebnisse weisen darauf hin, dass die verwendete Konzentration von Norfloxacin große Auswirkungen auf das Gesamttranskriptom des untersuchten Stammes haben und insbesondere die Genexpression von zehn im Genom des EDL933 befindlichen Prophagen erhöht wurde. Die durch die Microarrayversuche erhaltenen Expressionsraten wurden durch Quantifizierung der cDNA mittels RT Real-Time PCR Untersuchungen überprüft. Zusammenfassend ist festzustellen, dass Norfloxacin neben der antibiotischen Wirkung in der hier verwendeten geringen Konzentration multiple Effekte auf E. coli O157:H7 ausübt und die Auswirkungen in Zukunft noch detaillierter untersucht werden müssen. Die DNA-Microarraytechnologie und der kommerziell erhältliche E. coli O157 Array ermöglichen diese umfassenden Analyse des Transkriptionsprofils. Im Rahmen dieser Arbeit konnte diese Technologie für Untersuchungen der Genexpression von E. coli O157 etabliert und validiert werdenInfection with Shiga toxin producing Escherichia coli (STEC) is a serious cause of bloody diarrhea and sporadic cases and outbreaks of food-related diseases such hemorrhagic colitis and the hemolytic uremic syndrome (HUS) worldwide. The use of antibiotics in therapy of STEC-associated diseases has been discussed controversially. Release of phage-encoded Shiga toxins is the major virulence factor of enterhemorrhagic Escherichia coli (EHEC). The genome of the EHEC strain E. coli O157:H7 EDL933 contains 18 prophages or prophages elements, including the Stx1- and Stx2-encoding phages CP-933V and BP-933W. Stx-production and Stx-prophage induction can be stimulated by certain antibiotics, e.g. mitomycinC or UV light. The aim of this study was to investigate the influence of a low concentration of the gyrase inhibitor norfloxacin on the whole transcriptom of E. coli O157:H7 strain EDL933 and particularly on the gene expression of prophages using the DNA-microarraytechnology and the commercial available MWG E. coli O157 Array. To determine this, E. coli O157:H7 cultures were incubated with 200 ng/ml norfloxacin. Total RNA was isolated and labelled with fluorescence dyes during reverse transcription. Following this, the labelled cDNA was hybridized with the commercial E. coli O157 Arrays and the fluorescence intensities were measured, analysed and evaluated with appropriate software. Results of this study have indicated that a low concentration of norfloxacin have profound effects on the trancriptome of E. coli O157:H7. Under the conditions applied (200 ng/ml norfloxacin) and an incubation time of 120 minutes, 118 spots indicated a transcriptional upregulation and 122 spots a transcriptional downregulation of E. coli O157:H7 genes present on the array. In detail, 85 spots could be ascribed to EDL933 phage genes. Fifty-two of them could be assigned to the Shiga toxin encoding phages CP-933V and BP-933W, the others belonged to the non-Stx encoding phages or prophages elements existing in the EDL933 genome. Conspicuous, genes present in the late region of the BP-933W prophage were induced most strongly, up to 158-fold in the case of stxA2. Only some genes present in the early region of the Stx1 encoding phage CP-933V were induced upon induction with norfloxacin. Notably, only some genes of the non-Stx phages of EDL933 appeared to be induced after induction. The additional upregulated genes were related to recombination and stress functions and to E. coli O157:H7 RIMD0509952 genes. The majority of downregulated genes belonging to primary metabolism, such as amino acid biosynthesis, cell division and energy metabolism. In conclusion, an induction of E. coli O157:H7 strain EDL933 with 200 ng/ml norfloxacin has profound effects on the transcriptome of E. coli O157:H7, in particular on the global gene expression of more then ten prophages. The DNA-microarray technology and especially the E. coli O157 Array offer a modern tool for analysis of transcription profiles of the serious pathogen EHEC O157 in response to stress, e.g. antibiotics. In the context of this work, the DNA-microarraytechnology could be established and validated to provide the opportunity for further studies about the global effects on the whole transcriptome of E. coli O157
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Eriksson, Erik. "Verotoxinogenic Escherichia coli O157:H7 in Swedish cattle and pigs /." Uppsala : Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, 2010. http://epsilon.slu.se/201003.pdf.
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McCleery, David R. "Interaction between Escherichia coli O157:H7 and food spoilage bacteria." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394887.
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Corbishley, Alexander. "Cellular immune responses of cattle to Escherichia coli O157:H7." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/17605.
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Enterohaemorrhagic Escherichia coli O157:H7 causes haemorrhagic diarrhoea and potentially fatal renal failure in humans. Ruminants are considered to be the primary reservoir for human infection. Vaccines that reduce shedding in cattle are only partially protective and their underlying protective mechanisms are unknown. Studies investigating the response of cattle to colonisation generally focus on humoral immunity, leaving the role of cellular immunity unclear. To inform future vaccine development, the cellular immune response of cattle during EHEC O157:H7 colonisation was examined. Calves were challenged with either a phage type (PT) 21/28 strain possessing the Shiga toxin (Stx) 2a and Stx2c genes or a PT32 strain possessing the Stx2c gene only. T-helper cell associated transcripts at the terminal rectum were analysed by reverse transcriptase quantitative PCR (RT-qPCR). Induction of interferon (IFN)γ and T-bet was observed, with peak expression of both genes at 7 days in PT32 challenged calves, whilst up regulation was delayed, peaking at 21 days in PT21/28 challenged calves. Cells isolated from gastro-intestinal lymph nodes demonstrated antigen-specific proliferation and IFNγ release in response to type III secreted proteins (T3SPs); however responsiveness was suppressed in cells isolated from PT32 challenged calves. Lymph node cells showed increased expression of the proliferation marker Ki67 in CD4+ T cells from PT21/28, NK cells from PT32 and CD8+ and γδ T cells from both PT21/28 and PT32 challenged calves following ex vivo stimulation with T3SPs. Epitope mapping of rectal lymph node CD4+ T cell responses to 16 EHEC O157:H7 proteins, identified 20 CD4+ T cell epitopes specific to E. coli. The highly conserved N-terminal region of Intimin, including the signal peptide, was consistently recognised by mucosal CD4+ T cell populations from multiple animals of different major histocompatibility complex (MHC) class II haplotypes. Studies investigating the impact of secreted bacterial proteins on bovine peripheral blood mononuclear cells (PBMC) identified the ability of these proteins to cleave the surface molecule CD8 and that this phenotype was dependent on the ler virulence regulator but not the type III secretory system (T3SS) machinery. This effect was also observed in murine and ovine, but not human lymphocytes. Preliminary in vitro experiments suggest that this activity may reduce the efficiency of CD8+ T cell killing. This study demonstrates that cattle mount cellular immune responses during colonisation with EHEC O157:H7, the temporality of which is strain dependent, with further evidence of strain-specific immunomodulation.
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McGannon, Colleen M. "Antibiotic Therapy in the Treatment of E. coli O157:H7." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1230919332.
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Skinner, Kim David. "Effect of trace mineral supplementation and the use of an experimental Escherichia coli O157:H7 vaccine on Escherichia coli O157:H7 fecal shedding in beef calves." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/skinner/SkinnerK1205.pdf.
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Cho, Chia-Hui. "Acid tolerance in Escherichia coli O157, H7 following cold shock treatment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57527.pdf.
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Kerr, Marie. "The survival of Escherichia coli O157:H7 in natural mineral water." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365397.
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Nasri, Hassen. "Mechanisms of inhibition of escherichia coli O157:H7 by food preservatives /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9988686.
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Page, Jennifer Anne. "Diversity in Escherichia coli O157:h7 between human and bovine strains." Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2292.
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