Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 104-116).

Thesis (Ph. D., Microbiology, Molecular Biology and Biochemistry)--University of Idaho, August 2009. / Major professor: Carolyn H. Bohach. Includes bibliographical references. Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Aug. 26, 2009). Bibliography: leaves 40-45.

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.

Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on June 07, 2010). Includes bibliographical references.

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Made available in DSpace on 2014-06-11T19:27:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-30Bitstream added on 2014-06-13T18:56:07Z : No. of bitstreams: 1 prata_cb_me_jabo.pdf: 1292020 bytes, checksum: 1886044e5ddc4f62eed48d5f34981c8d (MD5) / Universidade Estadual Paulista (UNESP) / Escherichia coli O157:H7 é uma cepa de importância crescente por estar associada a vários surtos graves de doença em humanos, a maioria derivada do consumo de carne bovina crua ou mal cozida. Os bovinos constituem seu reservatório mais importante, aventando-se a hipótese de que mudanças do regime alimentar em confinamentos atuariam favoravelmente ao aparecimento de cepas shigatoxigênicas. Neste estudo objetivou-se verificar, comparativamente durante o abate, a prevalência desse sorotipo e o comportamento de métodos indicadores como a contagem total de microrganismos viáveis (CTMV) e de contaminação fecal - coliformes totais e E. coli, em amostras de fezes e em carcaças de bovinos terminados a pasto e em confinamento, possibilitando a disponibilização de subsídios necessários aos programas de Análise de Perigos e Pontos Críticos de Controle (APPCC) e de Análise de Risco (RA), empregados na redução do risco de doenças transmitidas por alimentos. Identificados os lotes de acordo com a terminação (dez de cada tipo), desses foram aleatoriamente colhidas e analisadas 100 amostras de suabe retal, 100 amostras de carcaças e 67 amostras de “recortes” da desossa (carne industrial) utilizando-se, para a E. coli O157- H7, técnica automatizada de PCR. À exceção de uma única amostra de recortes (0,37%), as demais, tanto de fezes quanto de carcaças, foram negativas para a cepa pesquisada. Além de contatar-se uma prevalência muito baixa, não se evidenciou diferenças entre os tipos de terminação dos animais. Os resultados dos indicadores - CTMV, de coliformes totais e E. coli, foram considerados aceitáveis em 91%, 85% e 93% das amostras, respectivamente, oferecendo suporte e concordância com a baixa prevalência encontrada. / Escherichia coli O157:H7 is an important strain that has been associated with outbreaks of serious disease in humans, most being derived from consumption of raw or poorly cooked beef. It is likely that cattle are an important reservoir, suggesting the possibility that changes in feedlot diet favor the emergence of shigatoxigenic strains of E. coli. This study is intended to verify, comparatively during bovine slaughter, the occurrence of E. coli O157:H7 associated with the sampling results obtained by means of general indicator methods (total viable count) and fecal contamination indicators (coliforms and E. coli). Samples will be taken from both excreta and carcasses of cattle finished either on pasture or feedlot, allowing the provision of subsidies necessary for Hazard Analysis and Critical Control Points (HACCP) and Risk Analysis (RA) programs and applied in the reduction of the risk of foodborne diseases. After identification of batches according to the type of finishing (feedlot or pasture), samples were randomly collected and analyzed. 100 rectal swabs, 100 samples from carcasses sponging, and 67 samples of sliced meat from the boning room (industrial meat). An automatic PCR technique for detection of E. coli O157:H7 was used. Except for one sample of sliced meat (0.37%), all others, both for excreta and carcasses, were negative for the O157:H7 E. coli strain. There were no significant differences in prevalence between the types of cattle finishing of the animals. The results of the indicators methods (TVC, coliforms and E. coli); were considered acceptable in 91%, 85% and 93% of tested samples, respectively, supporting and in agreement with low prevalence of O157:H7 found.

Detecta la presencia y determina la prevalencia de E. coli O157:H7 en Latuca sativa (lechuga) y Spinacea oleracea (espinaca), obtenidas de fundos agrícolas de la periferia de la ciudad de Lima. Se analizan 120 muestras de hortalizas, proveniente de 4 fundos de Lima; se utiliza la técnica del número más probable para la enumeración de E. coli, para la caracterización de E. coli O157:H7 se emplea el enriquecimiento selectivo, el análisis bioquímico y pruebas serológicas. Para determinar la presencia de los factores de virulencia shigatoxina (stx) e intimina (eaeA) se emplea el método de PCR en tiempo real. Para la entero hemolisina se realiza la prueba de hemólisis. Del total de muestras recolectadas (120), el 13,33 %(16) resulta positivo para E. coli O157:H7, el 1,67 %(2) presenta E. coli O157 no H7. De las 16 cepas (13,33 %) de E. coli O157:H7 se obtienen las siguientes secuencias de factores de virulencia: 3 (2.50 %) stx - / eaeA + y Hem - ; 8 (6,65 %) stx +/ eaeA + y Hem -; 2 (1,67 %) stx + / eaeA + y Hem +; 2 (1,67 %) stx + / eaeA - y Hem -; y 1 (0,83 %) stx - / eaeA + y Hem +. Así mismo el 86,67 % resulta negativo para E. coli O157:H7. El estudio revela la presencia de E. coli O157:H7 con una prevalencia del 13,33 % en hortalizas de fundos agrícolas de la periferia de la ciudad de Lima. / Tesis

With modern culture moving towards convenience in terms of fresh produce, especially with meat products, science needs to constantly evolve to serve these customer needs. These needs however can sometimes be implemented too hastily without the proper assessment done for factors such as food safety. One such improvement is the use of modified atmosphere packaged minced meat. This form allows the minced meat to be kept for much longer than normal without freezing the product, providing the fast pasted consumer both the convenience of having fresh, unfrozen meat as well as an added shelf life. MAP works by disrupting the atmosphere within these packages, retarding the growth of the spoilage micro-organisms, thus causing them to require a longer time span to reach spoilage numbers. The problem however arises that although most of these techniques are tried and trusted on the products’ spoilage organisms, it does not take into consideration the effect MAP and the altered spoilage organism communities would have on a pathogen that might be present on the products. This study thus aimed to assess the effect of both factors on Escherichia coli O157:H7 (phase 1) and Staphylococcus aureus (phase 2) in minced meat kept at 5°C as well as trying to identify the major affecting factors. The two subject organisms were each inoculated into 2 different types of MAP packs and a non-atmosphere modified PVC overlaid minced meat sample at two differing concentrations of 105 and 102 to also assess the impact of high andlow initial pathogen presence. These packs were then analysed over a time period of 16 days to track the changing minced meat environment. APC, Pseudomonads, LAB and Enterobacteriaceae counts were all investigated along with the pathogenic counts. Apart from colony enumeration, the colour of the minced meat samples were also taken to determine the effect that these parameters have on the appearance of the product, as colour is often the first sensorial characteristic that determines the purchase of fresh meat products. pH was determined to ascertain the environmental changes occurring in the product and whether groups such as the LAB would change the environment to better suit their needs. Finally the atmospheric makeup was also measured to determine the effect of the MAP system and the change occurring in a closed system that could be attributed to the growth and respiration of the bacterial communities present. Apart from the main aim of the study, two additional studies were performed that arose during the planning and analyses of the two primary phases. Firstly the use of a quarter versus a full plate enumeration was studied to determine its accuracy as well as possibility of use in full studies to aid enumeration and decrease time and financial input. Here a direct comparison was done between the two techniques after which they were compared and assessed in their functionality for both homogenous and heterogeneous community enumeration on selective and non-selective media. The other secondary study focussed on the use of new technology for both the enumeration and tracking of genetically modified organisms in a variety of different environments. Here a bioluminescent imaging system was used on a genetically modified strain of E. coli to track its spread through minced meat, packaged either in a MAP or PVC overlaid pack, over 48 hours in an accelerated shelf life study. Enumeration of said organism was also undertaken whereby the intensity of emitted light would correspond to a defined count, enabling rapid enumeration of samples, whether overgrown or not. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Food Science / unrestricted

Escherichia coli 0157:H7 is classified as a member of the enterohaemorrhagic E. coli (EHEC) family. These organisms are responsible for a variety of clinical manifestations ranging from non-bloody diarrhoea to gross bloody diarrhoea with complications that include haemorrhagic colitis (HC), haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopaenic purpura (TTP). Infection occurs by the ingestion of faecally contaminated food products, water sources and through person-to-person contact. Outbreaks of E. coli O157:H7 have been reported worldwide although most outbreaks seem to be from countries in the Northern hemisphere. Very little information is available on the prevalence of E. coli O157:H7 in South Africa. The only data available on E. coli O157:H7 were from a 1992 outbreak in Swaziland with some cases spreading to the adjacent provinces of South Africa. Selective methods were assessed and optimised to identify and isolate E. coli O157:H7 from food, water and faeces. These methods included culture techniques, immunomagnetic separation, immunoassays and molecular confirmation techniques. The methods optimised and assessed in this study proved to be suitable for the detection and isolation of E. coli O157:H7 from environmental water, food and faecal samples. In addition to the isolation of E. coli O157:H7 from these sources, methods were also optimised for the characterisation of E. coli O157:H7 using repetitive sequence analysis and induction of shiga toxin (Stx)¬converting phages which carry the genes coding for Stx from strains of E. coli O157:H7. The prevalence of E. coli O157:H7 in human-, bovine- and porcine faeces, sewage and recreational waters was investigated in a selected region of South Africa. Data suggested a low prevalence in sewage (0.76%), recreational waters (0%) and human faecal (0%) samples with a higher prevalence among carriers such as cattle (12.5%) and pigs (14.29%). UV-induced Stx-converting phages were examined and found to have different phage morphologies to the previously described lambdoid structure. In order to establish the host range susceptibility of these phages, all induced phages were subjected to conditions favourable for infecting E. coli O157:H7, non-O157 E. coli and other members of the enterobacteriaceae family including Salmonella, Shigella, Enterobacter, Klebsiella, and Proteus. These results have shown that Stx-phages were able to infect Salmonella cholerasuis and produce infectious progeny from these strains. Stx-converting phages propagated in Salmonella cholerasuis were able to re-infect strains of E. coli O157:H7. This study has shown that IMS in combination with molecular techniques was a sensitive tool for the isolation, identification and characterisation of E. coli O157:H7 from different sources. Results indicated that Stx-phages induced from E. coli O157:H7 demonstrated lambdoid structure as well as phages with long hexagonal heads and long non-contractile tails. / Dissertation (MSc (Medical Virology))--University of Pretoria, 2005. / Medical Virology / unrestricted