To see the other types of publications on this topic, follow the link: E.coli O157.
Dissertations / Theses on the topic 'E.coli O157'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'E.coli O157.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
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.
Full text
2
Silagyi, Karen Suzanne. "Biofilm formation by Escherichia coli O157:H7." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7806.
Full textAbstract:
Thesis (M.S.) -- University of Maryland, College Park, 2007.<br>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.
3
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.
Full text
4
Ntuli, Victor. "Shigatoxin producing Escherichia coli O157 and non-O157 serotypes in producer-distributor bulk milk." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/65932.
Full textAbstract:
Several recent large outbreaks of gastrointestinal diseases have highlighted the threat posed by morbidity and mortality associated with shigatoxin-producing Escherichia coli (STEC). Furthermore, the treatment of STEC infections is now threatened by the emergence of antibiotic resistance which is an alarming health concern in the world of medicine. The most implicated STEC in foodborne disease outbreaks across the globe is O157 serotype, although some emerging STEC non-O157 serotypes are increasingly becoming recognised as foodborne pathogens of important public health concern. This study was undertaken to characterise bacterial species in raw and pasteurised producer-distributor bulk milk (PDBM) with specific emphasis on E. coli and other Enterobacteriaceae. E. coli was further investigated for the prevalence and distribution of virulence factors (stx 1, stx 2 and hlyA), serotypes and antibiotic resistance patterns, which also included extended-spectrum ?-lactamase (ESBL) producing capacity. Subsequently, the study further estimated the haemolytic uraemic syndrome (HUS) risk associated with the consumption of STEC contaminated PDBM and also estimated the resulting burden of illness that may be associated with the consumption of such milk in South Africa (SA). A total of 258 PDBM samples were collected, using convenience sampling, from outlets (purchase points) in eight different geographical provinces in SA. Isolation, detection and enumeration of total aerobic bacteria, coliforms and E. coli were carried out using 3M E. coli /coliform petrifilm plates. Matrix assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) was used for the rapid identification of the bacterial isolates. The identification of E. coli was confirmed using PCR of the uidA gene. Further characterisation of E. coli into serogroups, identification of virulence factors and antibiotic resistance profiles were then performed. E. coli O157 was characterised using selective media and confirmed using mismatch amplification mutation assay (MAMA)-multiplex PCR. Identification of E. coli -serogroups was carried out by the restriction of amplified O-antigen gene cluster (rfb-RFLP), coupled with serum agglutination assay. Virulence factors (stx 1, stx 2 and hlyA) were determined using both phenotypic and genotypic characterisation. Antimicrobial agent susceptibility tests and detection of extended spectrum beta-lactamase (ESBL) producing capacity of the E. coli isolates were performed using phenotypic characterisation. Finally, a quantitative risk assessment for STEC in PDBM was also conducted. More than 60% of the PDBM samples were found not to be fit for human consumption on the basis of the minimum standards prescribed in the Foodstuffs, Cosmetics and Disinfectants Act (Act 54 of 1972). Raw and pasteurised PDBM was contaminated with a wide diversity of Enterobacteriaceae species, which included spoilage microbiota.<br>Thesis (PhD)--University of Pretoria, 2017.<br>Food Science<br>PhD<br>Unrestricted
5
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.
Full textAbstract:
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.
6
Nauer, Timo. "Untersuchungen zum Wachstum und zur Persistenz von Escherichia coli O26:H11, O157:H7, O157:H45 und O159:H~ in Bezug auf Säurestress /." [S.l.] : [s.n.], 2009. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000274968.
Full text
7
Ungkuraphinunt, Paphapit. "Factors contributing to the presence of Escherichia coli O157:H7 and O157:NM in feedlots and feedlot cattle." Texas A&M University, 2003. http://hdl.handle.net/1969.1/1172.
Full textAbstract:
Environmental sources within 5 feedlots were sampled for E. coli O157:H7 and O157:NM to determine the prevalence of this pathogen with a view to minimize or control its spread in the feedlot environment. Monthly samples were taken from the feedlots in the Panhandle and South Plains of Texas over a nine-month period. Samples were examined by an immunomagnetic bead separation, followed by plating onto CT-SMAC and CHROMagar O157 media. Sorbitol-negative colonies were tested using ImmunoCard Stat! E. coli O157:H7 Plus and confirmed as E. coli O157:H7, using biochemical (Vitek system) and serological tests (latex agglutination). Additionally, one hundred sponge samples were collected from the hides of stunned cattle at the slaughter plant. All isolates were subjected to rep-PCR DNA fingerprinting and antimicrobial profiling.
E. coli O157 was isolated from hide (56%) and environmental samples (4%). E. coli O157 was isolated from all environmental sources, with peak prevalence during November (9%) and March (10%). At least one sample from each feedlot was positive 42% of the time. The most contaminated sites were the chute area (6%) and sludge from waste water ponds (6%). Positive samples were most frequently found from feedlot 5 (7%) and the greatest variation in positive samples between feedlots (0-34%) occurred during March. A decrease in the presence of E. coli O157 in feedlots was observed during January (0%), when ambient, water, and pond sludge temperatures were consistently low. No correlation with other environmental factors was observed. Hide was a primary source of E. coli O157 on carcasses with an overall prevalence of 56%. Of two sampling days, the number of positive hide samples varied from 14% for the first day to 98% for the second day. The total positive samples collected (environmental (47); hide (56)) were 64% H7, and 36% NM. The environmental isolates showed similar antibiotic resistance patterns, regardless of the source. Most E. coli O157 isolates from the feedlots and hides showed a high level of resistance to cephalothin (45%) and sulfisoxazole (56%). E. coli O157 isolates from feedlots were resistant to more than 10 antibiotics (9/317). All of the isolates appeared highly similar, with an average similarity of 53% by rep-PCR DNA fingerprinting.
8
Rosser, Tracy. "Pathogenic potential of Escherichia coli O26 and sorbitol-fermenting Escherichia coli O157:NM." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4427.
Full textAbstract:
Verocytotoxin-producing Escherichia coli (VTEC) are important human pathogens that may cause diarrhoea, haemorrhagic colitis and haemolytic uremic syndrome (HUS). Worldwide, non-sorbitol-fermenting (NSF) VTEC O157:H7 is the most common serogroup associated with HUS but several non-O157:H7 serogroups have emerged as causes of this disease. This research investigated the pathogenic potential of two non-O157:H7 serogroups: O26 and sorbitol-fermenting (SF) O157:NM. While VTEC O26 have emerged as a significant cause of HUS in continental Europe, human infections associated with this pathogen are uncommon in Scotland and generally only result in simple diarrhoea. The study characterised E. coli O26 isolates recovered from human infections in Europe and Scotland and isolates collected from Scottish cattle with the objectives to identify factors which may allow strains to cause more serious clinical disease and to investigate the potential of bovine VTEC O26 in Scotland to cause human infection. MLST analysis of housekeeping genes found little genetic variation in the genomic ‘backbone’ among the vast majority of E. coli O26 isolates. The gene for verocytotoxin 2 (vtx2) alone was carried by VTEC O26 isolates recovered from patients in continental Europe but was found in no Scottish human isolate, where the majority of isolates did not harbour a vtx gene. It was demonstrated that among the European VTEC O26 human isolates, 67% carried a specific allele within the promoter region for LEE1 and 87% harboured the tccP2 gene. In contrast, no Scottish VTEC O26 human isolate carried this allele or the tccP2 gene. The impact these genotypic characteristics have on the pathogenic potential of a strain remains uncertain. There were no clear differences in verocytotoxin titres, levels of LEEencoded protein secretion or levels of adherence to Caco-2 cells between VTEC O26 isolates recovered from human infections of varying severity. However, levels of LEE-encoded protein secretion from cattle isolates were generally higher than those from many of the human isolates. The differences in pathogenic potential between isolates are likely to be due to horizontally acquired DNA, including vtx2 carriage and the O-island-phage-associated effector protein repertoire. Further work is required to determine if the differences identified may also impact on shedding levels from cattle and therefore the likelihood of transmission to humans. Since 1988, SF VTEC O157:NM strains have emerged and have been associated with a higher incidence of progression to HUS than NSF VTEC O157:H7. This study investigated bacterial factors that may account for the increased pathogenic potential of SF VTEC O157:NM. While no evidence of toxin or toxin expression differences between the two VTEC O157 groups was found, the SF VTEC O157:NM strains adhered at significantly higher levels to a human colonic cell line. Under the conditions tested, curli were shown to be the main factor responsible for the increased adherence to Caco-2 cells. The capacity of SF VTEC O157:NM strains to express curli at 37C may have relevance to the epidemiology of human infections as curliated strains could promote higher levels of colonization and inflammation in the human intestine. In turn this could lead to increased toxin exposure and an increased likelihood of progression to HUS.
9
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.
Full textAbstract:
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.<br>xv, 162 leaves : ill. ; 29 cm.
10
Hopkins, Katie Louise. "Molecular methods for strain characterisation of Escherichia coli O157." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368793.
Full text
11
O'Brien, Stephen Benedict. "Exposure assessment of Escherichia coli O157 in minced beef." Thesis, University of Ulster, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415874.
Full text
12
Urabi, Iftikhar. "Virulence factors of verotoxin-producing Escherichia coli O157:H7." Thesis, University of Warwick, 1993. http://wrap.warwick.ac.uk/104210/.
Full textAbstract:
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.
13
Flockhart, Allen Forrest. "Analysis of O-island deletions in Escherichia coli O157:H7." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/8154.
Full textAbstract:
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.
14
Corbishley, Alexander. "Cellular immune responses of cattle to Escherichia coli O157:H7." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/17605.
Full textAbstract:
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.
15
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.
Full text
16
Paddock, Zachary Dean. "Shiga toxin producing Escherichia coli (STEC) in cattle: factors affecting fecal shedding of E. coli O157:H7 and detection methods of non-O157 STEC." Diss., Kansas State University, 2013. http://hdl.handle.net/2097/15732.
Full textAbstract:
Doctor of Philosophy<br>Department of Diagnostic Medicine/Pathobiology<br>T. G. Nagaraja<br>Escherichia coli O157:H7 and over 380 non-O157 serotypes of Shiga toxin producing E. coli (STEC) are human food-borne pathogens that inhabit the hindgut of ruminants and are shed in the feces, which subsequently contaminate food products. Recent epidemiological data have shown that six non-O157 STEC (O26, O103, O111, O121, O45 and O145) account for majority of human STEC infections. Fecal shedding of STEC is influenced by a number of factors, including diets, supplements, and feed additives, because of their potential to alter hindgut ecosystem. Not much is known about the fecal shedding of non-O157 STEC in cattle because of lack of standardized detection methods. Fecal shedding of E. coli O157:H7 was studied to determine the effects of supplemental urea, monensin, an ionophore, and ractopamine, a beta-agonist. Cattle fed monensin at 44 mg/kg of feed had lower (P = 0.05) fecal O157:H7 prevalence than cattle fed 33 mg/kg. Supplemental urea (0.35 or 0.70% of the diet) and inclusion of ractopamine at 200 mg/animal/day had no effect on fecal shedding of E. coli O157:H7. In an experimental inoculation study, inclusion of corn starch to a distiller’s grains (DG)-supplemented diet had no effect on fecal shedding of E. coli O157 suggesting that either the decreased starch content in the DG-supplemented diet is not a factor in the increased shedding of E. coli O157:H7 or inclusion of pure starch in the diet may not have achieved our intended goal to have starch flow into the hindgut similar to that of corn grain. A multiplex PCR to detect O26, O45, O103, O111, O121, O145, and O157 was designed and applicability to detect the seven serogroups in cattle feces was evaluated. A multiplex PCR, designed to detect E. coli O104, feces showed presence of O104 in cattle feces (20.6%), but the isolated strains did not carry genes characteristic of the virulent strain responsible for the 2011 food-borne outbreak in Germany. Two preharvest interventions, a siderophore receptor and porin proteins-based vaccine and a Lactobacillus acidophilus-based direct-fed microbial, intended to control E. coli O157, had no effect on fecal shedding of O26 assessed by culture-based or PCR-based method.
17
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.
Full text
18
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.
Full textAbstract:
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 werden<br>Infection 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
19
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.
Full text
20
Gordon, Helen E. "Movement and survival of Escherichia coli O157 in the environment." Thesis, University of Aberdeen, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446620.
Full textAbstract:
<i>E. coli</i> O157 is shed into the environment from the faeces of infected animals. Once in the soil, the availability of hydrological pathways enables cells to disperse through the soil and enter the groundwater. This thesis investigates the transmission and survival of <i>E. coli</i> O157 in the farming environment with particular emphasis on the role of hydrological pathways. Findings from fieldwork included the observation that <i>E. coli</i> O157 population densities in faeces varied due to animal shedding rates and increasing temperature. Rainfall events were found to increase transport of <i>E. coli</i> O157 to a local stream. Strain typing using MLVA demonstrated that one strain had been transported from faeces into overland flow. Microcosm based experiments found that soil water content, temperature and soil type affected the recoverability of <i>E. coli</i> O157 from soil. The transport of <i>E. coli</i> O157 was influenced by the presence of preferential flow pathways under heavy rainfall conditions. The days after rainfall event caused changes in both the population density and the cellular activity of <i>E. coli </i>O157. The population dynamics and activity of <i>E. coli </i>O157 was monitored in different environmental matrices at different temperatures. These variables were found to influence the population and cellular activity of <i>E. coli</i> O157. During this experiment, cells appeared to enter a viable but non-culturable state. The study showed that the dispersal of <i>E. coli</i> O157 is mediated by soil-related hydrological pathways. By using the thesis findings to improve current risk assessment strategies, the number of <i>E. coli</i> O157 cases from environmental sources may be reduced.
21
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.
Full text
22
Persad, Anil Kenneth. "Epidemiological studies on Non-O157 Shiga toxin-producing Escherichia coli." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1467817228.
Full text
23
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.
Full text
24
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.
Full text
25
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.
Full textAbstract:
Made available in DSpace on 2014-07-29T15:07:48Z (GMT). No. of bitstreams: 1
Dissertacao_Joice_Costa.pdf: 1218899 bytes, checksum: 93178d81a8f2ef95cc6d5f75deb0fef8 (MD5)
Previous issue date: 2008-08-27<br>There 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.<br>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
26
Goll, Melanie. "Nachweis und DNA-Fingerprinting von Escherichia-coli-O157-Stämmen bei Pferden." Wetteberg : VVB Laufersweiler, 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976072742.
Full text
27
Botero, Cláudia Luzia Quintero. "Phäno- und Genotypisierung von Escherichia-coli-O157-Stämmen aus unterschiedlichen Habitaten." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969490313.
Full text
28
Fox, J. Trent. "Prevalence, characterization and intervention of Escherichia coli o157 in finishing cattle." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/446.
Full text
29
Cooper, Ian Richard. "The role of freshwater biofilms as reservoirs of Escherichia coli O157." Thesis, University of Brighton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412427.
Full textAbstract:
Escherichia coli 0157 is a strain of enteric bacteria that is associated with two potentially fatal diseases, haemorrhagic colitis and haemolytic uraemic syndrome. The bacterium has been implicated with outbreaks of disease where the individual has been exposed either to water or to land contaminated with faecal material, or to food poisoning pertaining to inadequate slaughter, cooking, or hygiene practices. E. coli 0157 has been isolated from private and municipal water supplies, mainly as a result of contamination of the source water. Animal grazing and the use of untreated, manure-based fertiliser can lead to an influx of faecal bacteria to the soil, where cultivation and natural run-off transfer the bacteria deep into the soil, as well as ground and surface waters. A dairy farm in East Sussex (United Kingdom) was used to investigate the potential of virulent E. coli 0157 isolates to exist within temperate freshwater biofilms. Devices using indigenous flint shingle were set up at four sites along the stream network to allow natural biofilm formation. Stones were removed from each site at four week intervals for one year, and screened to characterise eight Enterobacteriaceae genera and obtain total heterotrophic counts. Pooled faecal samples were obtained from indigenous grazing animals were also characterised to investigate their potential role as vectors of this pathogenic organism. A total of 1002 E. coli isolates were recovered from both the biofilm and animal faeces, 48 of which were identified as E. coli 0157. All E. coli isolates were analysed for kinetic biochemical phenotypes using the PhenePlateTM technique, and all confirmed E. coli 0157 isolates were subjected to an antibiotic resistance screen in an attempt to develop a host-specific resistance profile using the VetMICTM technique. The presence of five virulence traits known to cause or to be associated with human enteric disease were identified among confirmed E. coli O157 isolates using PCR. Phenotypic analysis revealed that distinct sub-populations of E. coli exist for each animal population, some of which displayed a significant phenotypic similarity to those recovered from the biofilms, suggesting that a source of faecal bacteria may be entering the streams. The antibiotic screen was not able to determine host-specific antibiotic profiles due to the small number of isolates recovered from the pooled faeces from each animal population (fourteen from pooled goat faeces, four from cattle, two from chickens and two from pigs). PCR confirmed the presence of the two verotoxin genes, those for intimin and an enterohaemolysin-encoding plasmid, as well as two ERIC sequences determined from E. coli O157 strains known to cause disease. This work supports research revealing that the bacterium can survive in environmental conditions that are in stark contrast to those of the mammalian gastro-intestinal tract. It suggests a link between strains that are excreted by grazing animals and those found in the aquatic epilithic biofilms, and represent a potential reservoir for the dissemination of disease to susceptible human populations. This research has implications for epidemiological studies, and suggests that disease control measures should be adjusted to account for the transfer of bacteria from land-based environments to aquatic ones, accounting for both natural and human-associated processes. E. coli 0157 is a clear and present danger to human health if ingested, but the bacterium exists in the biofilms as a naturallyoccurring organism, and should be treated as a result of natural run-off and leaching processes rather than the deliberate contamination of surface waters.
30
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.
Full text
31
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.
Full text
32
Abongo, BO, and MNB Momba. "Prevalence and characterization of Escherichia coli O157:H7 isolates from meat and meat products sold in Amathole District, Eastern Cape Province of South Africa." Elsevier, 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001755.
Full textAbstract:
a b s t r a c t
Meat and meat products have been implicated in outbreaks of Escherichia coli O157:H7 in most parts of
the world. In the Amathole District Municipality of the Eastern Cape Province of South Africa, a large
number of households consume meat and meat products daily, although the microbiological quality of
these types of food is questionable. The present study investigated the prevalence of E. coli O157:H7
isolated from selected meat and meat products (45 samples each of biltong, cold meat, mincemeat, and
polony) sold in this area. Strains of E. coli O157:H7 were isolated by enrichment culture and confirmed by
polymerase chain reaction (PCR). Also investigated were the antibiogram profiles of the E. coli O157:H7
isolates. Five (2.8%) out of 180 meat and meat products examined were positive for E. coli O157:H7 that
carried the fliCH7, rfbEO157, and eaeA genes. Two of the E. coli O157:H7 isolates were resistant against all
the eight antibiotics tested. To prevent E. coli O157:H7 infections, meat and meat products such as
biltong, cold meat, mincemeat and polony should be properly handled, and packed in sterile polyvinyl
wrappers.
33
Nissen, Silke. "Remediation of water-borne pollutants and pathogens by photoelectrocatalysis." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25471.
Full text
34
Dadgar, Ashraf. "Detection of enterohemorrhagic Escherichia coli (EHEC)." Thesis, Uppsala University, Department of Medical Biochemistry and Microbiology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6011.
Full textAbstract:
<p>Escherichia coli is a natural inhabitant of the intestines of both humans and animals, but there are also several pathogenic types of E. coli which cause disease in humans.</p><p>Strains of enterohemorrhagic E. coli (EHEC) have been associated with outbreaks of diarrhea, hemorrhagic colitis and hemolytic uremic syndrome in humans. Most clinical signs of disease arise as a consequence of the production of shigatoxin 1 and 2 or combination of these toxins. Other major virulence factors include EHEC hemolysin and intimin, the product of the eae gene that is involved in attaching and effacing adherence phenotype. EHEC has also been associated with uncomplicated diarrhea.</p><p>The capacity to control EHEC disease and to limit the scale of outbreaks is dependent upon prompt diagnosis and identification of the source of infection.</p><p>The principal reservoirs of EHEC are cattle and food products, which presumably have come into contact with domestic animal manure and/or are inadequately pasteurised, these are important vehicles of infection.</p><p>In the present study, the PCR technique with primers detecting the verocytotoxin genes was shown to be a possible method to screen for and identify EHEC.</p><p>In summary stx genes were detected in 16 samples of 228 sampels and the eae gene was detected in 2 samples using PCR.</p>
35
Gonçalves, Vanessa Parpinelli [UNESP]. "Eliminação de Escherichia coli Shigatoxigênica não-O157 em compostagem de esterco bovino." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/103895.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:32:53Z (GMT). No. of bitstreams: 0
Previous issue date: 2006-08-31Bitstream added on 2014-06-13T19:03:36Z : No. of bitstreams: 1
goncalves_vp_dr_jabo.pdf: 2137160 bytes, checksum: e87c3ecace3827353ad491c1f873e090 (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Escherichia coli é a bactéria mais comum entre os patógenos entéricos causadores de doenças intestinais. As diferentes classes de E. coli causadoras de diarréia são reconhecidas através dos fatores de virulência que elas apresentam. As E. coli produtoras de Shiga toxina (STEC), especialmente o sorotipo O157:H7 tem sido associado a diversas doenças no ser humano. Além do sorotipo O157:H7, vários outros sorogrupos não-O157 também estão associados a infecções em humanos. Estas bactérias podem ser recuperadas de muitos animais, mas o gado bovino é reconhecido como o seu mais importante reservatório natural. Para análise da sobrevivência de cepas STEC não-O157 em sistemas de compostagem, inicialmente foram coletadas fezes de três vacas saudáveis que apresentaram E. coli portando o gene stx2, característico de cepas STEC. Foram montados dois sistemas de compostagem: o primeiro foi realizado em vala de 60cmd, no qual E. coli apresentando o gene stx2 foi eliminada após 8, 25 e 30 dias nas temperaturas de 40, 42 e 38°C, respectivamente; o segundo sistema foi realizado sobre o solo em um monte em forma de pirâmide com 1md, no qual as bactérias foram eliminadas após 4, 4 e 7 dias nas temperaturas de 65, 56 e 52°C, respectivamente. A temperatura alcançada durante a compostagem e os microrganismos presentes no esterco parecem ser os responsáveis pela eliminação do patógeno nos sistemas de compostagem, o qual pode ser útil para a redução da carga patogênica presente no esterco destinado para aplicações no solo.<br>Escherichia coli is the most common bacteria among the enteric pathogens able to cause intestinal disease. Several classes of diarrhea-causing E. coli are recognized on the basis of their virulence factors production. Shiga-like toxigenic E. coli (STEC), especially serotype O157:H7, have been associated with many diseases in human beings. Besides sorotype O157:H7, many others non-O157 sorogroups have also been associated with human infections. These bacterias can be isolated from a range of animals, but cattle is generally recognized as the major natural source. To analyze the survival of non-O157 STEC strains in composting system, first was collected faeces from three healthy cows that contain E. coli STEC cells carrying the stx2 gene. Two composting systems were used: the first one was a cave with 60cmd were the E. coli STEC cells with stx2 gene were eliminated after 8, 25 and 30 days at 40, 42 and 38°C, respectively; the second one was a heap pyramid system with 1md, where the cells were eliminated after 4, 4, 7 days at 65, 56 and 52°C, respectively. The reached temperature in the composting systems and the indigenous microorganisms present in the manure seems to contribute to pathogen elimination, what may be a useful means of reducing the pathogen load of manure destined for soil application.
36
Gonçalves, Vanessa Parpinelli. "Eliminação de Escherichia coli Shigatoxigênica não-O157 em compostagem de esterco bovino /." Jaboticabal : [s.n.], 2006. http://hdl.handle.net/11449/103895.
Full textAbstract:
Orientador: José Moacir Marin<br>Banca: Clóvis Wesley Oliveira de Souza<br>Banca: José Eduardo Zaia<br>Banca: Alessandra Aparecida Medeiros<br>Banca: Lúcia Maria Carareto Alves<br>Resumo: Escherichia coli é a bactéria mais comum entre os patógenos entéricos causadores de doenças intestinais. As diferentes classes de E. coli causadoras de diarréia são reconhecidas através dos fatores de virulência que elas apresentam. As E. coli produtoras de Shiga toxina (STEC), especialmente o sorotipo O157:H7 tem sido associado a diversas doenças no ser humano. Além do sorotipo O157:H7, vários outros sorogrupos não-O157 também estão associados a infecções em humanos. Estas bactérias podem ser recuperadas de muitos animais, mas o gado bovino é reconhecido como o seu mais importante reservatório natural. Para análise da sobrevivência de cepas STEC não-O157 em sistemas de compostagem, inicialmente foram coletadas fezes de três vacas saudáveis que apresentaram E. coli portando o gene stx2, característico de cepas STEC. Foram montados dois sistemas de compostagem: o primeiro foi realizado em vala de 60cmd, no qual E. coli apresentando o gene stx2 foi eliminada após 8, 25 e 30 dias nas temperaturas de 40, 42 e 38°C, respectivamente; o segundo sistema foi realizado sobre o solo em um monte em forma de pirâmide com 1md, no qual as bactérias foram eliminadas após 4, 4 e 7 dias nas temperaturas de 65, 56 e 52°C, respectivamente. A temperatura alcançada durante a compostagem e os microrganismos presentes no esterco parecem ser os responsáveis pela eliminação do patógeno nos sistemas de compostagem, o qual pode ser útil para a redução da carga patogênica presente no esterco destinado para aplicações no solo.<br>Abstract: Escherichia coli is the most common bacteria among the enteric pathogens able to cause intestinal disease. Several classes of diarrhea-causing E. coli are recognized on the basis of their virulence factors production. Shiga-like toxigenic E. coli (STEC), especially serotype O157:H7, have been associated with many diseases in human beings. Besides sorotype O157:H7, many others non-O157 sorogroups have also been associated with human infections. These bacterias can be isolated from a range of animals, but cattle is generally recognized as the major natural source. To analyze the survival of non-O157 STEC strains in composting system, first was collected faeces from three healthy cows that contain E. coli STEC cells carrying the stx2 gene. Two composting systems were used: the first one was a cave with 60cmd were the E. coli STEC cells with stx2 gene were eliminated after 8, 25 and 30 days at 40, 42 and 38°C, respectively; the second one was a heap pyramid system with 1md, where the cells were eliminated after 4, 4, 7 days at 65, 56 and 52°C, respectively. The reached temperature in the composting systems and the indigenous microorganisms present in the manure seems to contribute to pathogen elimination, what may be a useful means of reducing the pathogen load of manure destined for soil application.<br>Doutor
37
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.
Full text
38
Saad, Susana Marta Isay. "Comportamento de Escherichia coli enterohemorrágica O157:H7 frente a bactérias autóclones em carne bovina móida." Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/9/9131/tde-31102007-152112/.
Full textAbstract:
E. coli O157:H7 é um patógeno de importância em alimentos, tendo sido envolvido, nos últimos anos, em surtos de grandes proporções, principalmente por produtos cárneos. Entretanto sua ocorrência em alimentos, particularmente em carne crua, é baixa e poderia, eventualmente, ser atribuída à atividade antagônica expressa por outros microrganismos presentes. Assim sendo, foi avaliada a interferência de bactérias que fazem parte da microbiota normal de carne sobre a multiplicação de E. coli O157:H7 em carne bovina moída mantida em refrigeração e em temperatura ambiente. Com essa finalidade, foram realizados testes de desafio (\"challenge tests\") em porções de 25 g de carne bovina moída inoculadas com diferentes concentrações de E. coli O157:H7 (101, 103 e 106 CFC/g), desafiadas com diferentes inóculos de E. coli não patogênica, Pseudomonas putida e Leuconostoc spp. As cepas de Pseudamonas putida e de Leuconostoc spp., isoladas de carne, foram selecionadas em função de atividade inibitória contra E. calí O157:H7 observada \"in vitro\". Para o monitoramento de E. coli O157:H7, foram utilizados o método convencional, ou seja, plaqueamento em ágar Mac Conkey-sorbitol e identificação de colônias (testes bioquímicos e sorológicos), bem como um método considerado rápido, empregando o Petrifilm™ Kit-HEC. De maneira geral, não foram observadas interferências significativas da presença de diferentes inóculos de E. coli não patogênica, P. putida e Leuconostoc spp., sobre a multiplicação de diferentes inóculos de E. coli O157:H7 à temperatura ambiente e à temperatura de refrigeração. Paralelamente, o Petrifilm™ Kit-HEC revelou um alto índice de correlação com o ágar Mac Conkey-sorbitol (97,2%), com contagens da mesma ordem de grandeza. Os experimentos à temperatura ambiente revelaram um maior índice de correlação (99,0%), quando comparados àqueles à temperatura de refrigeração (94,9%). Aparentemente, a baixa ocorrência de E. coli O157:H7 em alimentos, particularmente em carne bovina crua, não pode ser atribuída à atividade antagônica de alguns microrganismos presentes.<br>Escherichia coli O157:H7 is a foodborne pathogen of increasing importance, since it has been involved in several threatening outbreaks, most of them associated with meat products. Though, it is possible that the low occurrence af E. coli O157:H7 in food, particularly in meat, may be due to antagonistic effects af other microorganisms present. Therefore, the influence of some bacteria isolated from meat, over E. coli O157:H7 in meat samples stored at chill and room temperatures was evaluated. For that purpose, studies were performed on 25 g of ground beef inoculated with different spiking levels of E. coli O157:H7 (101, 103 and 106 CFC/g), challenged with different spiking levels of non pathogenic E. coli, Pseudomonas putida or Leuconostoc spp. The Ps. putida and Leuconostoc spp. strains were selected based on deferred antagonism observed against E. coli O157:H7. Multiplication was monitored by means of cultural methods, employing sorbitol Mac Conkey agar and additional identification tests, and the rapid method Petrifilm™ Kit-HEC. No significant influence of non pathogenic E. coli, Pseudomonas putida and Leuconostoc spp. over the multiplication of E. coli O157:H7 was observed. Results on Petrifilm™ Kit-HEC showed high correlation with results on sorbitol Mac Conkey agar (97,2%). Experiments performed with meat kept at room temperatures resulted in higher correlation values (99,0%), when compared to those of meat kept at chill temperatures (94,9%). Apparently, the low occurrence of E. coli O157:H7 in food, particularly in raw meat, can\'t be attributed to antagonistic effects of other bacteria from natural microflora.
39
Cui, Shenghui. "Detection and characterization of escherichia coli O157:H7 and salmonella in food." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1381.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2004.<br>Thesis research directed by: Food Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
40
Lowe, Ross M. S., and University of Lethbridge Faculty of Arts and Science. "Escherichia coli O157:H7 lineage persistence and colonization of cattle in vitro." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, c2009, 2009. http://hdl.handle.net/10133/2509.
Full textAbstract:
Escherichia coli O157:H7 is an important human pathogen that resides primarily in cattle and feedlot environments. E. coli O157:H7 can be divided into phylogenetic groups termed lineages; lineage I strains are responsible for most human illnesses. An understanding of the etiology of these lineages within cattle and the feedlot environment could allow for more effective surveillance and mitigation strategies. There were no lineage associated differences in growth or survival of E. coli O157:H7 in bovine feces at 4°C, 12°C or 25°C. Lineage I strains more readily colonized cattle jejunum tissue and a bovine colonic cell line than lineage II and intermediate type strains. Enhanced colonization of cattle by lineage I strains may increase the persistence of these strains in feedlots via re-infection and increased shedding. This outcome could increase the transmission of lineage I strains to the food supply and increase the potential for these strains to cause human illness.<br>xiii, 101 leaves ; 29 cm
41
Robinson, Susan Elizabeth. "Temporal characteristics of shedding of Escherichia coli O157 in UK dairy cattle." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406663.
Full text
42
Scott, Fiona Wendy. "Fluorescent amplified fragment length polymorphism typing of salmonella and Escherichia coli O157." Thesis, Open University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392870.
Full text
43
Dodd, Charles C. "Epidemiology of salmonella and E. coli O157 in beef cattle production systems." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/6916.
Full textAbstract:
Doctor of Philosophy<br>Food Science Institute -- Diagnostic Medicine/Pathobiology<br>David G. Renter<br>Salmonella and Escherichia coli O157 are important causes of foodborne illness in humans and have been associated with the consumption of undercooked, contaminated beef. Individual feedlot cattle may shed these organisms in their feces and subsequently contaminate cattle hides and carcasses at harvest. Preharvest and harvest interventions may significantly decrease the risk of beef contamination and subsequent risk of human illness. Previous research suggests that preharvest interventions for Salmonella or E. coli O157 may compliment harvest interventions and reduce the risk of carcass contamination. In my research, I used diverse study designs to develop a better understanding of the epidemiology of Salmonella and E. coli O157 and evaluate the impact of specific preharvest interventions in commercial feedlot cattle. A randomized controlled trial indicated that a commercially available vaccine did not affect the fecal prevalence of Salmonella, or health and performance of cohorts of feedlot cattle. However, the fecal prevalence of Salmonella varied by cohort, suggesting cattle source as a risk factor. In a repeated cross-sectional study, the fecal prevalence of Salmonella in cattle at feedlot arrival was not associated with the prevalence immediately prior to harvest, yet specific Salmonella subtypes, as defined by pulsed-field gel electrophoresis (PFGE), persisted throughout the feeding period. Another of my studies defined and compared PFGE subtypes of E. coli O157 isolated from cattle feces and carcass samples at harvest to determine relationships between fecal shedding and carcass contamination. Truckload appeared to be an important factor, and feces from cattle shedding both high- and low-concentrations of E. coli O157 posed a risk for carcass contamination. A stochastic Monte-Carlo modeling framework was later used to assess the impact of seasonal fecal prevalence and combinations of preharvest interventions on the risk of carcass contamination with E. coli O157. Results indicated that it may be important to incorporate multiple preharvest interventions, especially during periods of high fecal prevalence of E. coli O157. Overall, the research described in this dissertation demonstrates that multiple risk factors and interventions at the cohort level must be considered in order to mitigate the risks associated with Salmonella and E. coli O157 in beef production systems.
44
Boyer, Renee R. "Mechanisms Associated with Attachment of Escherichia coli O157:H7 to Lettuce Surfaces." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27003.
Full textAbstract:
Fresh produce is increasingly associated with foodborne outbreaks. In order to develop effective intervention and measures to reduce microbial risks, it is essential to attain a better understand the mechanisms of attachment of foodborne pathogens to fruits and vegetables. Using lettuce as a model, the attachment of Escherichia coli O157:H7 to produce surfaces was studied. Strains expressing various extracellular proteins (curli, O157-antigen, and intimin) known to influence attachment of E. coli to intestinal cells were evaluated for their physicochemical properties and ability to adhere to cut edge and whole leaf lettuce. Escherichia coli O157:H7 strains included: 0018, 43894 and 43895 (curli producing and non-producing); 86-24 (WT), F-12 (O157-antigen negative), pRFBE (O-antigen replaced on plasmid); and 86-24, 86-24Ã eae10 (intimin negative). The eleven strains were surveyed for their hydrophobicity and cell charge using hydrophobic interaction chromatography (HIC) and electrostatic interaction chromatography (ESIC) techniques. Iceberg lettuce squares (2 x 2 cm) were inoculated with E. coli O157:H7 strains separately (7.0 log CFU/square) and dried in a laminar flow hood. Lettuce was sampled before (unrinsed) and after being rinsed twice with sterile de-ionized water (rinsed). Strips (2 mm wide) of each cut edge of the lettuce were aseptically removed. Cut-edge and whole-leaf samples were homogenized and spiral plated onto Luria-Bertani agar, supplemented with nalidixic acid (50ppm), to assess levels of bacteria remaining on the lettuce leaf after rinsing. The rinse steps were not effective in significantly removing bacteria from lettuce (p>0.05). Curli-producing and non-producing strains preferentially attached to cut edge versus the whole leaf portions of lettuce (p<0.05); however the 86-24 strains showed no preference for attachment. With the exception of 0018 curli-producing and non-producing strains, presence/absence of extracellular proteins surveyed did not influence attachment of E. coli O157:H7 to either cut edge or whole leaf lettuce. There was significantly greater attachment of the curli-producing 0018 strain over the curli non-producing 0018 strain to cut and whole lettuce surfaces (p<0.05). Production of curli and O-polysaccharide significantly increased (p<0.05) the cellâ s overall hydrophobicity of the cell; however this did not affect attachment (p<0.05). The overall cell charge of all strains was negative; however, charge did not affect attachment of E. coli O157:H7 to lettuce. The presence of extracellular appendages (curli, O157-antigen, intimin) as well as hydrophobicity and cell charge properties had no affect on attachment of the cell to lettuce.<br>Ph. D.
45
Scharpe, Jennifer Marie. "Crisis communication during beef recalls due to E. coli O157:H7 contamination." [Ames, Iowa : Iowa State University], 2009.
Find full text
46
Carruthers, Michael D. "Transcriptional analysis of Escherichia coli O157:H7 during in vivo mimicking conditions." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3389094.
Full text
47
Bollman, Jill. "Effects of cold shocking on the survival and injury of Escherichia coli O157:H7 under freezing conditions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ45023.pdf.
Full text
48
Schuehle, Celeste Elaine. "Evaluation of the relationship between stress response and the fecal shedding of Escherichia coli O157:H7." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4436.
Full textAbstract:
This study was conducted to determine if a relationship exists between
temperament, stress response, and the shedding of Escerhichia coli O157:H7. Cattle (n
= 150) were evaluated for disposition and stress response before shipping to the feeding
operation, upon arrival at the feedlot, at approximately 70d on feed, and prior to
transport to the harvesting facility. Chute and pen scores, as well as serum cortisol
concentrations, were measured in order to assess individual temperament and stress
response. A temperament index was created to classify cattle as Excitable, Intermediate,
or Calm. The presence of E. coli O157:H7 was determined by rectal swabs on the live
cattle and swabs of colons collected postmortem at the processing facility. As expected,
variables for pre-shipment temperament index, exit velocity, pen score, arrival and midpoint
exit velocity, and mid-point cortisol concentrations differed (P < 0.05) greatly
between temperament groups. However, pre-shipment chute scores and cortisol
concentration, as well as arrival and final cortisol concentrations differed (P < 0.05) only
for Excitable cattle compared to both Calm and Intermediate groups. The percentage of
cattle shedding the pathogen at arrival was approximately equal between temperament
groups. When sampled before shipment to the processing facility, a higher proportion (P
= 0.03) of cattle displaying Calm temperaments shed E. coli O157:H7 than the other groups. Results from postmortem colon samples exhibited a similar trend. When the
results from all four sampling periods were pooled, the Calm cattle had a greater
numerical percentage test positive for E. coli O157:H7. However, the pooled frequency
distribution is largely dictated by the results of the final sampling time. Based on these
results, it appears that Excitable cattle are not more likely to shed E. coli O157:H7. In
fact, it seems that Calm cattle may be equally or more susceptible to shed at later points
in the feeding period. However, it is important to note that a relatively small number of
the samples tested positive for E. coli O157:H7, thus, potentially causing dramatic
changes in the distributions.
49
Malone, Aaron S. "INACTIVATION MECHANISMS OF ALTERNATIVE FOOD PROCESSES ON ESCHERICHIA COLI O157:H7." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1237307369.
Full text
50
Aperce, Celine C. "Factors influencing Escherichia coli O157 colonization of the gastrointestinal tract of feedlot cattle." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/14987.
Full textAbstract:
Doctor of Philosophy<br>Department of Animal Sciences and Industry<br>J. S. Drouillard<br>The first chapter of this dissertation reviews factors affecting E. coli O157:H7 prevalence in the gastrointestinal tracts of cattle. Chapter 2 assessed E. coli O157:H7 ability to use bovine intestinal mucus and its constituents as substrates for growth in vitro in the presence and absence of fecal inoculum and exogenous enzymes. Whole mucus supported the greatest pathogen growth (P < 0.05), but all components tested were able to sustain E. coli growth. Chapter 3 evaluated the impact of crude glycerin feeding on E. coli O157 fecal shedding by cattle fed growing and finishing feedlot diets with corn or a combination of corn, distiller’s grains, and soybean hulls. Increasing levels of crude glycerin decreased incidence of E. coli O157 in growing cattle (linear effect, P < 0.01) and tended to do so in finishing cattle fed corn-based diets (P < 0.06). No effect of glycerin was observed in finishing cattle fed the byproduct-based diets (P > 0.05), highlighting potential for glycerin use as a means for controlling fecal prevalence of E. coli O157 in cattle fed conventional grain-based diets. Chapter 4 evaluated transportation and lairage effects on fecal shedding of E. coli in feedlot cattle by mimicking transport to the abattoir. Shedding patterns were influenced by transportation, with significantly lower E. coli O157 prevalence in transported animals 4 hours after transit (P < 0.05). Additional post-transit samplings are, however, needed to confirm effects of transport stress on pathogen prevalence and shedding patterns. The experiment summarized in chapter 5 evaluated the potential for utilizing fecal long-chain fatty acid (LCFA) profiles as an indicator of E. coli O157 status. Out of 39 LCFA evaluated, only eicosapentaenoic acid (EPA) concentration was associated with presence of the pathogen (P < 0.02). The final chapter assessed the impact of dietary menthol, up to 0.3% of diet DM, on antimicrobial resistance in commensal E. coli. Menthol addition affected prevalence of tetracycline resistant E. coli, but contrary to our hypothesis, increased their
occurrence after 30 days of treatment (P < 0.006). No hypothesis on mechanism responsible for this increase could be made from the present study.