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Favrin, Stacy Jane. „The use of bacteriophage in detecting foodborne bacterial pathogens“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ40410.pdf.
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Banerjee, Mousumi. „Occurrence and behaviour of foodborne bacterial pathogens in Indian retail spices“. Thesis, University of North Bengal, 2002. http://hdl.handle.net/123456789/1071.
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Rakshit, Mousumi. „Survivability and Growth of food borne bacterial pathogens as influenced by processing technologies during the production and storage of some legume - based traditional foods of India“. Thesis, University of North Bengal, 2014. http://ir.nbu.ac.in/hdl.handle.net/123456789/1844.
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Roy, Arindam. „Occurrence and behaviour of foodborne bacterial pathogens in some lagume-based traditional fermented foods marketed in West Bengal, India“. Thesis, University of North Bengal, 2007. http://hdl.handle.net/123456789/1050.
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Huff, Karleigh Rose. „Association of foodborne pathogens with Capsicum annuum fruit and evaluation of the fruit for antimicrobial compounds“. Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77213.
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Hot peppers are gaining popularity in the United States as both a vegetable and a spice. In 2008, jalapeño peppers were involved in a multistate outbreak of Salmonella Saintpaul. This is the first outbreak implicating jalapeño as a vehicle for foodborne illness. Hot peppers contain many compounds thought to possess antimicrobial characteristics. This research was conducted to provide more information on the interactions of pathogenic bacteria and jalapeño peppers, as well as to identify properties of Capsicum annuum that affect bacterial survival, growth, and inhibition.
Behavior of pathogens associated with jalapeños was investigated by inoculating jalapeño fruits with a cocktail of Listeria monocytogenes, Salmonella enterica, or Escherichia coli O157:H7 on the intact external surface, injured external surface, or intact internal cavity and storing the jalapeños at 7°C or 12°C. Intact external jalapeñosurfaces did not support the growth of the bacteria tested under storage conditions of 7°C. However, L. monocytogenes populations remained detectable throughout the 2 week study. At 7°C, pathogenic bacteria were able to survive but not grow on injured and internally inoculated jalapeño, but populations increased at 12°C (p=0.05). The most supportive growth environment for the pathogenic bacteria was the internal cavity of jalapeño held at 12°C. This study demonstrated the importance of intact uninjured produce and proper storage temperatures for food microbial safety.
Inhibitory properties of jalapeños were studied by making extracts from fresh jalapeño peppers to test for antimicrobial activity. A disk diffusion assay determined that the extracts were capable of inhibiting the growth of the pathogenic bacteria tested. Listeria monocytogenes was especially sensitive to the extracts. jalapeño extracts were fractionated using HPLC and used for inhibition assays using disk diffusion and growth curve generation. Two fractions stimulated bacterial growth (p=0.05), while two other fractions inhibited bacterial growth. The inhibitory fractions were separated further using HPLC and tested for antimicrobial activity. Fraction E1 suppressed the growth of L. monocytogenes. HPLC-MS analysis revealed that Fraction E1 contained compounds known as capsianosides. To prove that inhibition is caused by capsianoside(s) and determine minimum inhibitory concentrations, a method to isolate the pure compound should be developed.Ph. D.
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Moreirinha, Ana Catarina Fernandes. „Development of infrared spectroscopy for assessing bacterial quality in foods“. Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15278.
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Doutoramento em BiologiaRapid and specific detection of foodborne bacteria that can cause food spoilage or illness associated to its consumption is an increasingly important task in food industry. Bacterial detection, identification, and classification are generally performed using traditional methods based on biochemical or serological tests and the molecular methods based on DNA or RNA fingerprints. However, these methodologies are expensive, time consuming and laborious. Infrared spectroscopy is a reliable, rapid, and economic technique which could be explored as a tool for bacterial analysis in the food industry. In this thesis it was evaluated the potential of IR spectroscopy to study the bacterial quality of foods. In Chapter 2, it was developed a calibration model that successfully allowed to predict the bacterial concentration of naturally contaminated cooked ham samples kept at refrigeration temperature during 8 days. In this part, it was developed the methodology that allowed the best reproducibility of spectra from bacteria colonies with minimal sample preparation, which was used in the subsequent work. Several attempts trying different resolutions and number of scans in the IR were made. A spectral resolution of 4 cm-1, with 32 scans were the settings that allowed the best results. Subsequently, in Chapter 3, it was made an attempt to identify 22 different foodborne bacterial genera/species using IR spectroscopy coupled with multivariate analysis. The principal component analysis, used as an exploratory technique, allowed to form distinct groups, each one corresponding to a different genus, in most of the cases. Then, a hierarchical cluster analysis was performed to further analyse the group formation and the possibility of distinction between species of the same bacterial genus. It was observed that IR spectroscopy not only is suitable to the distinction of the different genera, but also to differentiate species of the same genus, with the simultaneous use of principal component analysis and cluster analysis techniques. The utilization of IR spectroscopy and multivariate statistical analysis were also investigated in Chapter 4, in order to confirm the presence of Listeria monocytogenes and Salmonella spp. isolated from contaminated foods, after growth in selective medium. This would allow to substitute the traditional biochemical and serological methods that are used to confirm these pathogens and that delay the obtainment of the results up to 2 days. The obtained results allowed the distinction of 3 different Listeria species and the distinction of Salmonella spp. from other bacteria that can be mistaken with them. Finally, in chapter 5, high pressure processing, an emerging methodology that permits to produce microbiologically safe foods and extend their shelf-life, was applied to 12 foodborne bacteria to determine their resistance and the effects of pressure in cells. A treatment of 300 MPa, during 15 minutes at room temperature was applied. Gram-negative bacteria were inactivated to undetectable levels and Gram-positive showed different resistances. Bacillus cereus and Staphylococcus aureus decreased only 2 logs and Listeria innocua decreased about 5 logs. IR spectroscopy was performed in bacterial colonies before and after HPP in order to investigate the alterations of the cellular compounds. It was found that high pressure alters bands assigned to some cellular components as proteins, lipids, oligopolysaccharides, phosphate groups from the cell wall and nucleic acids, suggesting disruption of the cell envelopes. In this work, bacterial quantification and classification, as well as assessment of cellular compounds modification with high pressure processing were successfully performed. Taking this into account, it was showed that IR spectroscopy is a very promising technique to analyse bacteria in a simple and inexpensive manner.
A deteção rápida e específica de bactérias que podem provocar deterioração de alimentos ou doenças associadas ao seu consumo é cada vez mais importante na indústria alimentar. A deteção, identificação e classificação de bactérias são geralmente realizadas utilizando métodos tradicionais baseados em testes bioquímicos e/ou serológicos e em métodos moleculares baseados em análise de DNA ou RNA. Contudo, estas metodologias são dispendiosas, demoradas e trabalhosas. A espectroscopia de infravermelho é uma técnica confiável, rápida e económica, que pode ser explorada como ferramenta para a indústria alimentar. Nesta tese foi avaliado o potencial da espectroscopia de infravermelho para estudar a qualidade bacteriana de alimentos. No capítulo 2, foi desenvolvido um modelo de calibração que permitiu prever com sucesso a concentração bacteriana de fiambre naturalmente contaminado, mantido em refrigeração durante 8 dias. Nesta parte, foi desenvolvida a metodologia que permitiu obter a melhor reprodutibilidade dos espectros das colónias de bactérias, com preparação mínima das amostras, que foi utilizada no trabalho subsequente. Foram realizadas várias tentativas para a obtenção de espectros de infravermelho, testando diferentes resoluções e número de scans. Os melhores resultados foram obtidos utilizando uma resolução espectral de 4 cm-1 e 32 varrimentos. De seguida, no capítulo 3, foi feita uma tentativa de identificar 22 bactérias provenientes de alimentos usando a espectroscopia de infravermelho associada a análise multivariada. A análise de componentes principais, utilizada como método exploratório, permitiu a formação de grupos distintos, cada um correspondendo a um género diferente, na grande maioria dos casos. Posteriormente, foi realizada uma análise hierárquica por clusters de forma a investigar a formação de grupos e a possibilidade de distinção de espécies dentro de um mesmo género de bactérias. Observou-se que a espectroscopia de infravermelho é adequada não só para a distinção de diferentes géneros, mas também para diferenciar espécies dentro de um mesmo género, com o uso simultâneo de análise de componentes principais e análise hierárquica por clusters. A utilização de espectroscopia de infravermelho e análise estatística multivariada foram também investigadas no capítulo 4 para confirmação da presença de Listeria monocytogenes e Salmonella spp., isoladas a partir de alimentos contaminados, após crescimento em meio selectivo. Isto permitiria a substituição dos métodos bioquímicos e serológicos que são usados para confirmar a presença destas bactérias patogénicas e que podem atrasar a obtenção de resultados por 2 dias. Os resultados obtidos permitiram a distinção de Salmonella spp. de outras bactérias que se possam confundir com elas. Por fim, no capítulo 5, o processamento por alta pressão, uma metodologia emergente que permite produzir alimentos microbiologicamente seguros e aumentar o seu tempo de prateleira, foi aplicada a 12 bactérias alimentares, de forma a determinar a sua resistência e os efeitos da pressão a nível das células. Foi aplicado um tratamento de 300 MPa, à temperatura ambiente e durante 15 minutos. As bactérias de Gram-negativo foram inativadas até níveis não detetáveis, enquanto as de Gram-positivo mostraram diferentes níveis de resistência. As espécies Bacillus cereus e Staphyloccus aureus decresceram apenas 2 unidades logarítmicas enquanto a espécie Listeria innocua diminuiu cerca de 5 unidades logarítmicas. A espectroscopia de infravermelho foi utilizada na análise das colónias bacterianas antes e após o tratamento por alta pressão, de forma a investigar as alterações que são provocadas nos componentes celulares com este tipo de processamento. Descobriu-se que a alta pressão altera bandas espectrais correspondentes a alguns componentes celulares, de entre os quais proteínas, lípidos, oligopolissacarídeos, grupos fosfato da parede celular e ácidos nucleicos, podendo indicar rutura da parede/membrana celular. Neste trabalho, a quantificação de bactérias e a sua classificação, bem como a análise de modificação nos componentes celulares após processamento por alta pressão foram realizados com sucesso. Assim, a espectroscopia de infravermelho demonstrou ser uma técnica bastante promissora para analisar bactérias provenientes de alimentos de uma forma simples e pouco dispendiosa.
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Shane, Sharon L. „Reported bacterial foodborne outbreaks occurring in institutional settings and group gatherings : United States, 2000 through 2004 /“. abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1440932.
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Thesis (M.P.H.)--University of Nevada, Reno, 2006."December, 2006." Includes bibliographical references (leaves 90-117). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm.
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Friedriczewski, Anelise Bravo. „Efeito da formação de biofilme por Staphylococcus coagulase positiva isolados de queijo mussarela elaborado com leite de búfala sobre a sensibilidade a sanitizantes“. Universidade Federal de Pelotas, 2017. http://guaiaca.ufpel.edu.br:8080/handle/prefix/3943.
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A mussarela de leite de búfala, principal tipo de queijo obtido a partir desse leite no Brasil, é um produto novo no mercado, com alta aceitação pelos consumidores e excelentes perspectivas de comércio. O queijo é um alimento rico em nutrientes, o que favorece a proliferação de micro-organismos que podem provocar toxi-infecções ou intoxicações nos consumidores. A gastrenterite estafilocócica é causada pela ingestão de alimentos que contenham enterotoxinas produzidas por Staphylococcus coagulase positiva. Um problema que pode dificultar a eliminação de microorganismos indesejáveis na indústria de alimentos é a formação de biofilme. O objetivo deste estudo foi determinar o efeito da formação de biofilme por Staphylococcus coagulase positiva (SCP) isolados de queijo mussarela de búfala sobre a sensibilidade a sanitizantes. A partir de contagens de SCP realizadas em 50 amostras de queijo mussarela de búfala foram obtidos isolados, que foram comparados entre si por rep-PCR e identificados bioquimicamente e por multiplex PCR. As cepas distintas foram testadas quanto a formação de biofilme em placas de microtitulação. As cepas forte formadoras e uma não formadora de biofilme foram testadas em superfícies de polietileno de alta densidade, aço inoxidável e vidro. Também foram testadas quanto à sensibilidade ao hipoclorito de sódio e ao iodo após a formação do biofilme. Vinte amostras de queijo albergavam SCP, entretanto as contagens estavam dentro dos limites estabelecidos pela legislação brasileira. A rep-PCR mostrou que cada uma das amostras que estavam contaminadas apresentava uma única cepa, as quais foram identificadas como S. aureus. Dois isolados foram classificados como forte formadores de biofilme, sete como moderados formadores, dez fracos formadores e um como não formador de biofilme. As duas cepas forte formadoras produziram biofilme nas três superfícies testadas. A aplicação dos sanitizantes hipoclorito de sódio e iodo promoveu uma redução das populações bacterianas de aproximadamente 2 log em todas as superfícies, tanto das cepas formadoras de biofilme como da não formadora. Embora as cepas formadoras de biofilme não sejam mais resistentes aos sanitizantes hipoclorito de sódio e iodo do que as não formadoras, elas atingem maiores concentrações no biofilme, o que resulta em maiores populações bacterianas remanescentes após a aplicação dos sanitizantes.
The Buffalo milk mozzarella cheese, main type of chesse obtained from this milk in Brazil, is a new product in the market, with high consumer acceptance and excellent prospects for trade. The cheese is rich in nutrients, which favors the proliferation of microorganisms that can cause food toxi-infections in the consumer. The staphylococcal gastro-enteritis is caused by ingestion of food containing enterotoxins produced by coagulase-positive Staphylococcus. One problem that may hinder the elimination of undesirable microorganisms in the food industry is the formation of biofilms. The objective of this study was to determine the effect of biofilm formation by coagulase-positive (CPS) Staphylococcus isolated from buffalo mozzarella cheese on sensitivity to sanitizers. From CPS counts carried out on 50 samples of buffalo mozzarella cheese were obtained isolates, which were compared by rep-PCR and biochemically identified and by multiplex PCR. The distinct strains were tested for biofilm formation in microtiter plates. Strong forming and non-biofilm forming strains were tested on high density polyethylene, stainless steel and glass surfaces. They were also tested for sensitivity to sodium hypochlorite and iodine after biofilm formation. Twenty samples of cheese harbor CPS, however the counts were within the limits established by Brazilian legislation. Rep-PCR showed that each of the samples that were contaminated had a single strain, which was identified as S. aureus. Two isolates were classified as strong biofilm formers, seven as moderate formers, ten weak formers and one as non-biofilm builder. The two strong forming strains produced biofilm on the three surfaces tested. The application of sodium hypochlorite and iodine sanitizers promoted a reduction of approximately 2 log bacterial populations on all surfaces of both the biofilm and non-forming strains. Although biofilm forming strains are no longer resistant to sanitizers sodium hypochlorite and iodine than non-forming sanitizers, they reach higher concentrations in the biofilm, resulting in larger bacterial populations remaining after application of the sanitizers.
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Abong'o, Benard Omondi. „Prevalence of Escherichia coli O157:H7 in water and meat and meat products and vegetables sold in the Eastern Cape Province of South Africa and its impact on the diarrhoeic conditions of HIV/AIDS patients“. Thesis, University of Fort Hare, 2008. http://hdl.handle.net/10353/87.
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Water and food borne Escherichia coli O157:H7 could be one of the pathogens posing high health risk to patients suffering from Acquired Immunodeficiency Syndrome (AIDS) because of its incrimination in diarrhoea cases in AIDS patients. The present study, which was conducted between March 2005 and August 2006, investigated the prevalence of E. coli O157:H7 in water, meat and meat products and vegetables and its impact on diarrhoeic conditions of confirmed and non-confirmed HIV/AIDS patients in the Amathole District in the Eastern Cape Province of South Africa. The water samples used in the study were obtained from stand pipes supplying treated drinking water to communities residing in Fort Beaufort, Alice, Dimbaza and Mdantsane whereas borehole waters were sampled from Ngwenya and Kwasaki. The meat and meat products and vegetable samples were purchased from shops, butcheries, supermarkets and open air markets in Fort Beaufort, Alice and Mdantsane. The stool swabs used in the study were obtained from HIV/AIDS and outpatient clinics at Frere Hospital in East London. A total of 180 each of water, meat and meat products and vegetable samples and another 360 stool samples were analyzed for E. coli O157:H7. Presumptive E. coli O157 was isolated from the samples by culture-based methods and confirmed using Polymerase Chain Reaction techniques. Anti-biogram as well as risk assessment were also carried out using standard methods. The viable counts of presumptive E. coli O157 for water samples ranged between 3.3 × 104 and 1.71 × 105 CFU/ml, and between 1.8 × 104 and 5.04 × 106 CFU/g for meat and meat products, whereas those for vegetables ranged between 1.3 × 103 and 1.6 × 106 CFU/g. The counts of presumptive E. coli O157 for the water and vegetable samples were not significantly different whereas those for meat and meat products were found to be significantly different (P ≤ 0.05). The prevalence rates of presumptive E coli O157 in meat and meat products was 35.55 percent (64/180), and 25.55 percent (46/180) and 21.66 percent (39/180) for water and vegetables respectively. Prevalence of presumptive E. coli O157 in the stool samples of HIV/AIDS patients was 36.39 percent (131/360), of which 56.5 percent (74/131) and 43.5 percent (57/131) were from stools of confirmed and non-confirmed HIV/AIDS patients, respectively. Molecular analysis of representative presumptive E. coli O157 indicated that 10.29 percent (4/39) of vegetables; 14.81 percent (4/27) of water and 38.46 percent (5/13) of meat and meat products carried E. coli O157:H7. Also 36 percent (9/25) and 17.24 percent (5/29) of the stool samples were positive for E. coli O157:H7. Antimicrobial susceptibility profile revealed that all of the E. coli O157:H7 isolated from water, meat and meat products and vegetables as well as those isolated from stools of confirmed and non-confirmed HIV/AIDS patients were resistant (R) to gentamycin and erythromycin. However, 75 percent (20/27) of these isolates were resistant (R) to ampicillin and tetracycline whereas approximately 25 percent (6/27) were resistant (R) to nalidixic acid, ceftriaxone, and chloramphenicol. All the isolates (27/27) were susceptible (S) to amikacin. Probability of risk of E. coli O157:H7 infection was high for confirmed HIV/AIDS patients than for the non-confirmed HIV/AIDS patients. Estimated probability of risk of E. coli O157:H7 due to ingestion of water was 1.00 for 100 confirmed and non-confirmed HIV/AIDS patients. Risk due to meat and meat products was estimated at 0.27 and 0.20 and for vegetables at 0.21 and 0.15 per 100 confirmed and non-confirmed HIV/AIDS patients. The findings of this study predicted a possible link between E. coli O157:H7 isolated from drinking water, meat and meat products and vegetables and diarrhoeic conditions in both confirmed and non-confirmed HIV/AIDS patients, and concludes that confirmed HIV/AIDS patients can be at higher risk of contracting water and food borne E. coli O157:H7 than nonconfirmed HIV/AIDS patients. It is thus recommended that proper water treatment and food handling, maximum food and water safety and sanitation as well as personal body hygiene should be maintained, in order to prevent E. coli O157:H7 infections. Education initiatives and active surveillance of E. coli O157:H7 should be taken by all the stake-holders working directly or indirectly towards ensuring enduring sound public health.
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Olivier, Dedré. „The influence of thermal and nonthermal food preservation methodologies on the liberation and ultrastructure of bacterial endotoxins“. Thesis, Bloemfontein : Central University of Technology, Free State, 2010. http://hdl.handle.net/11462/123.
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Thesis (D. Tech. (Biomed. Tech.)) -- Central University of Technology free State, 2010Consumer demands for fresh, microbiologically safe foods with high organoleptical and nutritional quality has led to the development of novel food preservation technologies as alternatives or enhancements to traditional preservation techniques. An example of these novel preservation technologies is high hydrostatic pressure (HHP) processing. It involves the applications of static pressure of 50 to 1 000 mega Pascals (MPa) to solid or packaged liquid foods, with varying holding times. The combination of factors to enhance preservation is increasingly being used in industry, e.g. the use of different temperatures and additives (hurdles) can enhance the preservative effect of HHP. In this study the influence of HHP on organism viability and growth response was assessed. The organisms evaluated included Escherichia coli O111, Listeria monocytogenes (UAFSBCC) and Staphylococcus aureus (ATCC 25923), in peptone water, which was subjected to HHP of 200 MPa for 15 minutes at 8 and 50 ºC respectively. Subsequent to the mentioned pressurisation, sub-culturing was performed and growth responses were evaluated at 0, 6, 18, 24, 30, 42 and 48 hours. Bacterial survival and growth response was measured by means of intact cell count, colony forming units and optical density. From the results it was eminent that bacterial cells were only sublethally injured and were able to repair within 48 hours of enriched sub-culturing. E. coli O111 proved to be most sensitive to HHP with Staphylococcus aureus (ATCC 25923) most resistant. This study also proved that bacterial concentration and inactivation rate are inversely proportionate to each other. Subsequent to growth and cell repair assessments, E. coli O111 was selected as a model to evaluate the effect of sublethal HHP on the liberation and toxicity of bacterial endotoxins (free and cell wall bound). It is also known that different extraction procedures extract different lipopolysaccharides (LPS) fractions and therefore LPS was extracted from the test broth by a combination method of Folch, Lees & Sloane-Stanley, and Venter and Ivanov. The extraction yielded a biphasic system, LPS with reduced lipid content in the upper phase (aqueous) and LPS with increased lipid content in the lower phase (organic). Following extraction the Limulus amebocyte lysate (LAL) test was performed to quantify the concentration (assumed) of LPS in the aqueous and organic phases. Free LPS was detected within six hours in the supernatant in the high and low bacterial loads, moreover the toxicity response of post HHP cell damage was more pronounced at 50 ºC (hurdle) than that observed for the treatments at 8 ºC (hurdle) and more so in the organic phases. The latter implied that HHP not only resulted in quantity LPS variation but also in structural change. However membrane repair was apparently complete after 48 hours, as differences in toxicity were no longer evident. Furthermore, the use of a porcine IL-6 ELISA assay was evaluated as an alternative for the customary LAL as a biomarker for pyrogenic substances in matrixes. Porcine whole blood was challenged for IL-6 production by LPS in the samples from the organic and aqueous systems. A porcine IL-6 enzyme-linked immunosorbent assay was used to assess IL-6 expression in whole blood after being challenged with LPS. From the results it emanated that HHP caused in a change in LPS structure which resulted in a decreased IL-6 expression in whole blood, indicating that structural adaptation of the cell membrane in response to HHP influenced the ability of LPS to stimulate macrophages and monocytes. Therefore, further research and development would be required to evaluate the influence of post HHP LPS on human IL-6 expression. When comparing the porcine IL-6 with the LAL no correlation in toxicity could be established in any of the treatment parameters. Finally it can be concluded that HHP had an influence in the structural morphology of LPS. These structural changes could result in LPS being more toxic, it could also have an effect on the accuracy of immunological assessments, the ability to form biofilm, and susceptibility to phages.
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Brandão, Barros Delfina Celeste. „Simultaneous detection of foodborne bacteria based on magnetic particles“. Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/385720.
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En la actualidad, está ampliamente aceptado en Europa que la investigación y la innovación son factores clave para reforzar la capacidad industrial y las perspectivas de negocios.
La tecnología es necesaria para abordar los problemas del mundo, pero también lo es la investigación, que permite la aparición de tecnologías innovadoras. Por lo tanto, invertir en investigación e innovación es esencial para el desarrollo de soluciones para los desafíos sociales, como por ejemplo la seguridad alimentaria. En este contexto, surge el término KETS (Key Enabling Technologies), que permite unificar diferentes campos de la ciencia, tales como la nanotecnología, los materiales avanzados y la biotecnología, entre otros. Esto indica una clara convergencia de la tecnología en el desarrollo de nuevas soluciones. Por ejemplo, con el fin de ofrecer soluciones en seguridad alimentaria, la investigación en química analítica no está solamente basada en el desarrollo de estrategias para obtener información cualitativa y cuantitativa sobre la composición y naturaleza de las sustancias, sino que ésta ha convergido en un campo de investigación más aplicado y multidisciplinar, formando alianzas entre diferentes áreas de conocimiento a través de la ciencia. Esta nueva concepción abre la posibilidad de crear nuevos principios analíticos, procedimientos de detección automatizados o in-situ, así como sondas de detección específica o nuevos dispositivos sensores.
La presente Tesis doctoral es el resultado de dicho carácter multidisciplinar de la química analítica, y con el objetivo de proporcionar soluciones a problemas relacionados con la seguridad alimentaria, se ha desarrollado un nuevo dispositivo sensor en base a conocimientos de química analítica pero también de biotecnología, microbiología y materiales avanzados.
Por ello, el primer apartado de este trabajo pretende ser una introducción general sobre la inocuidad de los alimentos y su importancia a nivel mundial, haciendo especial énfasis en los patógenos alimentarios emergentes responsables de los principales brotes y la contribución de la tecnología de los biosensores como factor conductor para el desarrollo de nuevas metodologías para la detección de bacterias transmitidas por los alimentos mediante técnicas de multiplexado.
Además, se discutirá también la integración de nuevos materiales con dimensiones nano/micrométricas en biosensores electroquímicos, destacando algunas de las ventajas de las partículas magnéticas: i) su capacidad para preconcentrar las bacterias presentes en muestras complejas mediante una reacción inmunológica ii) us uso como plataforma para el bioreceptor en los dispositivos de biosensores iii) o como soporte para la inmovilización magnética en la superficie de un electrodo de trabajo por atracción magnética.
Los métodos de detección para seguridad alimentaria actuales han permitido un avance significativo en relación al desarrollo de métodos rápidos y sensibles, en los que la implementación de bioensayos con capacidad de multiplexado es una de las tendencias emergentes. Sin embargo, se han descrito pocas estrategias basadas en biosensores electroquímicos para la detección simultánea de bacterias en alimentos. Por esta razón, en el presente trabajo se propone desarrollar un biosensor electroquímico que detecte simultáneamente Salmonella enterica, Listeria monocytogenes y Escherichia coli, basado en el uso de partículas magnéticas.
Las estrategias presentadas en esta Tesis doctoral se basan por un lado en un reconocimiento electroquímico inmunológico, que proporciona la detección de las células bacterianas, y por otro un reconocimiento genético, que permite la detección del ADN bacteriano. Estas dos estrategias se combinan con un paso de separación inmunomagnética que da lugar a la captura y preconcentración de las bacterias a partir de muestras de alimentos. Así, se ha realizado un estudio de las partículas magnéticas de diferentes tamaños (micro y nanométrica), para después efectuarse la separación inmunomagnética de S. enterica, L. monocytogenes y E. coli. Además, se han comparado posteriormente las dos estrategias para la detección de Salmonella, usándose como modelo muestras leche.
Finalmente, se describe una estrategia de PCR multiplexada combinada con un magneto-genosensor electroquímico usando partículas magnéticas de sílice para la detección simultánea de S. enterica, L. monocytogenes y E. coli.Nowadays, it is widely recognised in Europe that research and innovation are key factors to reinforce the industrial capacities and business perspectives. We need technology to address world´s problems, but we also need research to develop innovative technologies. Therefore, investing in research and innovation is essential to develop solutions for societal challenges, as for instance Food Safety. In this context, it comes out the term KETs (Key Enabling Technologies) to unify different fields across science, such as Nanotechnologies, Advanced materials, Biotechnology, among others. This indicates a clear convergence of technologies to address new solutions. For instance, analytical chemistry research is not only based anymore on the development of strategies to obtain qualitative and quantitative information about the composition and nature of substances. In order to provide solutions in food safety, analytical chemistry research has been converging into a more applied and multidisciplinary research field, forming alliances between different fields across science. This opens the possibility for the creation of new analytical principles, automated or in-situ detection procedures, as well as specific detection probes or new sensing devices. This Dissertation is a result of the multidisciplinary character of analytical chemistry. The aim of providing solutions to problems related to food safety bonds different science fields as analytical chemistry, biotechnology and advanced materials for the development of a new sensing device. Therefore, it is intended to give a general introduction about food safety and its importance worldwide, with special focus on the emerging foodborne pathogens responsible for the main outbreaks and the contribution of biosensors technology as the driver factor for the development of new methodologies for foodborne bacteria detection with multiplexing capabilities. Furthermore, the integration of new materials with nano/micrometer dimensions on electrochemical biosensors will be also discussed, highlighting some advantages of the use of magnetic particles: i) preconcentration of the bacteria from complex samples through an immunological reaction, ii) as a platform for the biorecognition element in the biosensing devices iii) as a support for the magnetic immobilisation on the surface of a working electrode under magneto-actuation. The current state of art for detection methods for food safety shows a significant progress relative to the development rapid and sensitive methods, in which the implementation of bioassays with multiplexing capabilities is one of the emergent trends. However, few approaches based on electrochemical biosensors for the simultaneous detection of foodborne bacteria have been reported. For this reason, it is proposed to develop an electrochemical biosensor for the simultaneous detection of Salmonella enterica, Listeria monocytogenes and Escherichia coli, based on the use of magnetic particles. The strategies presented in this Dissertation are based on electrochemical magneto-immuno and genosensing, in which electrochemical magneto-immunosensing provides the detection of whole bacterial cells, whereas the electrochemical magneto-genosensing provides the detection of the bacterial DNA. These two strategies are combined with an immunomagnetic separation step to capture and preconcentrate bacteria from food samples. Hence, a study of different magnetic particles with micro and nanometer sizes will be achieved for the immunomagnetic separation of S. enterica, L. monocytogenes and E. coli. Afterwards, electrochemical magneto-immuno and genosensing will be compared for the detection of Salmonella in milk, as a model. Finally, triple-tagging multiplex PCR combined with an electrochemical magneto-genosensor using silica magnetic particles as a platform will be reported for the simultaneous detection of S. enterica, L. monocytogenes and E. coli.
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Guan, Tat Yee. „Fate of foodborne bacteria in pesticide formulations“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0028/MQ51719.pdf.
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Saracino, Pasquale <1977>. „New signalling molecules in some foodborne bacteria“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/421/1/Saracino_Pasquale_tesi_dottorato.pdf.
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Saracino, Pasquale <1977>. „New signalling molecules in some foodborne bacteria“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/421/.
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Reyna-Granados, Javier Rolando. „Control of Foodborne Pathogenic Bacteria Using Natural Plant Antimicrobials“. Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228511.
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Foodborne pathogens are a threat to public health worldwide. Because many consumers prefer natural compounds to synthetic additives, research on safe plant-derived compounds with antimicrobial activity against foodborne pathogens is vital. The aim of this investigation was to evaluate the antimicrobial activities of plant essential oils (oregano, cinnamon, lemongrass), their active components (carvacrol, trans-cinnamaldehyde, citral) and plant-extracts such as green tea, apple skin extract, black and decaffeinated black tea, grapes seed and pomace extracts against foodborne bacteria. Salmonella enterica serotype Typhimurium DT104, and serotype Newport, were selected conducting an antibiotic screening on 23 Salmonella isolates using seven antibiotics to determine antibiotic resistance. Listeria monocytogenes (strain 101M; beef and pork sausage isolate; resistant to antimicrobials in past investigations) was included to represent gram-positive bacteria. Escherichia coli O157:H7 virulent isolates (932- apple juice isolate; ATCC 35150- human isolate; F4637- sprouts isolate; used as a cocktail) were selected after conducting a Multiplex PCR over nine E. coli O157:H7 isolates to detect shiga-toxin 1 and 2 genes. All antimicrobials were evaluated in vitro in phosphate buffered saline. In general, all pathogens were more susceptible to essential oils and their active components, than powder extracts. The most active antimicrobials from each category were directly applied on foods. The activity of oregano oil (0.5%) and green tea (3%) was evaluated against S. Typhimurium on chicken and S. Newport on tomatoes and sprouts, and the results showed that oregano oil was more effective. In addition, baby spinach leaf samples inoculated with green fluorescent protein labeled S. Newport were examined under confocal scanning laser microscope before and after antimicrobial treatments. Antimicrobial experiments against L. monocytogenes on sprouts, ham and bologna, carvacrol at 0.5% and grape seed extract at 3% were used and carvacrol showed better activity. Antimicrobial activity against E. coli O157:H7 was tested on romaine lettuce, spinach and ground beef using oregano oil at 0.5% and green tea at 3%. Both compounds were effective showing no recovery of E. coli O157:H7 from lettuce and spinach; however, was not reduced in ground beef. Antimicrobial plant compounds have the potential for reducing foodborne pathogenic bacteria on/in various foods.
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Smith-Palmer, Mary Alison. „The antimicrobial properties of plant essential oils against foodborne pathogens“. Thesis, Queen Margaret University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327082.
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Subires, Orenes Alicia. „Optimization of flow cytometry assays for the detection of injured foodborne pathogenic bacteria“. Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/311611.
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Algunos tratamientos de elaboración y conservación de los alimentos lesionan las bacterias, de manera que pierden la capacidad para multiplicarse y no son detectadas por métodos de cultivo convencionales. La citometría de flujo es una técnica de análisis independiente del cultivo de los microorganismos, usada ampliamente para evaluar de manera rápida el estado fisiológico de células bacterianas individuales, siendo la integridad de membrana unos de los indicadores más habituales debido a su importancia en la supervivencia de éstas. Sin embargo, los resultados obtenidos mediante citometría de flujo se ven afectados por la presencia de partículas de las muestras alimentarias.
En esta tesis, se evaluaron estrategias para desarrollar un ensayo por citometría de flujo basado en el uso del yoduro de propidio (YP), fluorocromo que no atraviesa las membranas intactas, combinado con un fluorocromo que penetra las membranas intactas, para detectar y cuantificar con precisión bacterias patógenas lesionadas. En el primer experimento, se ajustaron las concentraciones y las ratios de combinaciones de YP con SYTO 9, SYTO 24 y SYTO BC para mejorar la resolución de poblaciones de células sanas y muertas de Escherichia coli O157:H7, Salmonella Enteritidis y Listeria monocytogenes en suspensiones control. Esto permitió detectar células lesionadas en suspensiones expuestas a estreses relacionados con los alimentos. En el segundo experimento, se aplicaron las tinciones optimizadas a muestras de ensalada de pasta inoculadas con E. coli O157:H7. Asimismo, se compararon ocho pre-tratamientos basados en la filtración gruesa de las muestras homogeneizadas y en un paso de dilución/lavado, para evaluar la reducción de partículas interferentes y la recuperación de E. coli O157:H7 de la ensalada. El pre-tratamiento más favorable fue la combinación de la bolsa de homogenización con filtro de 63 µm y la filtración centrífuga a través de un filtro de 5 µm, ya que redujo la concentración de partículas interferentes tanto como diluir la muestra. Considerando que el objetivo principal de esta tesis fue detectar específicamente bacterias patógenas lesionadas, en el tercer experimento, la optimización se llevó a cabo para suspensiones control de E. coli O157:H7 en soluciones tampón comúnmente usadas en inmunoensayos, y teñidas con SYBR Green I, un fluorocromo con alta afinidad por los ácidos nucleicos, YP y un anticuerpo marcado con R-ficoeritrina (Ac-RFE). La adición de Ac-RFE no afectó notablemente la resolución de las poblaciones en comparación con la resolución conseguida con la tinción con SYBR Green I y YP, y permitió reconocer claramente las células de E. coli O157:H7. En el cuarto experimento, se evaluaron estrategias de filtración de señal analítica para reducir la adquisición de datos procedentes de partículas interferentes. Posteriormente, se aplicó el pre-tratamiento de muestra optimizado, la tinción para evaluar la integridad de membrana y la inmunodetección, y la filtración de señal analítica, para monitorizar los cambios de la integridad de membrana de E. coli O157:H7 inoculada en ensalada de pasta durante 14 días de almacenamiento en refrigeración (pH 4,5; 4°C). Con este protocolo optimizado, el límite de detección disminuyó a 5 log UFC/g. Además, se observó que la mayoría de células de E. coli O157:H7 estaban lesionadas al principio del almacenamiento, pero mostraban una membrana intacta al final, lo que sugiere que las células lesionadas repararon su membrana durante la exposición a ácido y refrigeración y, por lo tanto, sobrevivieron en la ensalada de pasta.
En conclusión, el ensayo por citometría de flujo para la evaluación de la integridad de membrana y la inmunodetección desarrollado en esta tesis es una buena herramienta para monitorizar el efecto de tratamientos relacionados con los alimentos sobre el estado de la membrana de E. coli O157:H7, parámetro fisiológico relacionado con la presencia de células lesionadas.Nowadays, one of the key factors driving consumer food choice is convenience. This has led to an increase in the ready-to-eat (RTE) meal market, with a consequent emergence of new food safety hazards, since food processing and preservation technologies that may be applied to these food products have a milder effect on microorganisms than traditional food processing strategies (e.g. pasteurization, sterilization). As a result, some of those technologies render injured bacteria, which may lose their ability to multiply and are therefore not detected by conventional plating. However, their presence in food must not be overlooked, due to their potential capacity to recover and pose a hazard to health in the case of pathogens. Flow cytometry is a culture-independent technique which has been widely used in bacterial research to rapidly assess the physiological state of individual cells, with membrane integrity being one of the most popular parameters due to its essential role in survival. However, flow cytometry results are largely affected by the interference of food particles. In this thesis, several strategies were evaluated to develop a flow cytometry assay, based on the use of the membrane-impermeant dye propidium iodide (PI) combined with a membrane-permeant dye, to accurately detect and enumerate injured pathogenic bacteria. In the first experiment, concentrations and ratios of combinations of PI with SYTO 9, SYTO 24, and SYTO BC were adjusted to improve resolution of healthy and dead Escherichia coli O157:H7, Salmonella Enteritidis and Listeria monocytogenes populations in control suspensions. This allowed detection of injured cells in suspensions exposed to food-related stresses. In the second experiment, optimized stainings were applied to RTE pasta salad samples inoculated with E. coli O157:H7. Moreover, eight different salad sample pre-treatments based on coarse filtration of homogenates and a dilution/wash step were compared in terms of background particle reduction and E. coli O157:H7 recovery. The most advantageous pre-treatment was the combination of a 63-µm filter blender bag and centrifugal filtration through a 5-µm filter, since it was equivalent to sample dilution in reducing background particle concentration. Considering that the ultimate goal of this thesis was to detect specific injured pathogen cells in RTE pasta salad, in the third experiment, optimization was carried out for E. coli O157:H7 control suspensions in buffers commonly used in immunoassays and stained with the high-affinity nucleic acid dye SYBR Green I, PI, and an R-phycoerythrin-labeled antibody (Ab-RPE). Addition of Ab-RPE did not remarkably affect population resolution compared with staining only with SYBR Green I and PI, and allowed clear recognition of E. coli O157:H7. Finally, in the fourth experiment, a range of signal filtering strategies were evaluated for reduced acquisition of flow cytometry data arising from interfering food particles. Then, optimized salad sample pre-treatment, combined membrane integrity and immunodetection staining, and signal filtering were applied to monitor the changes in membrane integrity of E. coli O157:H7 inoculated in pasta salad throughout 14-day refrigerated storage (pH 4.5, 4°C). With this optimized flow cytometry protocol, the limit of detection of the assay was reduced to 5 log CFU/g. Additionally, it was observed that most E. coli O157:H7 cells were injured at the beginning of refrigeration, but showed an intact membrane at the end, which suggests that injured cells repaired their membrane during exposure to refrigeration and acid stresses, and therefore survived in RTE pasta salad. In conclusion, the immunodetection and membrane integrity flow cytometry assay in food samples developed in this thesis is a good tool to monitor the effect of a number of food-related treatments on E. coli O157:H7 cell membrane state, a physiological parameter that can be related to the presence of injured cells.
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Nino, Maria Eugenia Ramos. „Quantitative and mechanistic studies of the effect of phenols on foodborne bacteria“. Thesis, University of Surrey, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320905.
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Paiva, Diego Moreira Singh Manpreet. „Effect of concrete sealant on survival of foodborne bacteria in processing environments“. Auburn, Ala, 2009. http://hdl.handle.net/10415/1835.
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Trias, Mansilla Rosalia. „Lactic acid bacteria as bioprotective agents against foodborne pathogens and spoilage microorganisms in fresh fruits and vegetables“. Doctoral thesis, Universitat de Girona, 2008. http://hdl.handle.net/10803/7932.
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La present tesi doctoral es centra en l'aplicació dels bacteris de l'àcid lactic (BAL) com a agents bioprotectors davant microorganismes patògens i deteriorants.Es van aïllar i seleccionar BAL de fruites i hortalisses fresques i es van assajar in vitro davant 5 microorganismes fitopatògens i 5 patògens humans.Es van realitzar assajos d'eficàcia en pomes Golden Delicious amb tots els aïllats enfront les infeccions causades pel fong Penicillium expansum. La soca més eficaç era Weissella cibaria TM128, que reduïa el diàmetre de les infeccions en un 50%.Les soques seleccionades es van assajar enfront els patògens Salmonella typhimurium, Escherichia coli i Listeria monocytogenes en enciams Iceberg i pomes Golden Delicious.Els BAL interferien eficientment amb el creixemet de S. typhimurium, and L. monocytogenes, però van mostrar poc efecte enfront E. coli.Finalment, es van realitzar assajos dosi-resposta amb les soques Leuconostoc mesenteroides CM135, CM160 and PM249 enfront L. monocytogenes. De totes les soques assajades, la soca CM160 va ser la més efectiva.The present thesis focuses on the use of lactic acid bacteria as bioprotective cultures to inhibit pathogenic and spoilage microorganisms.
Lactic acid bacteria were isolated and selected from fresh fruit and vegetables and tested in vitro against five plant pathogens and five human pathogen test bacteria.Efficacy trials with all the isolates were performed in Golden Delicious apples against the blue mould rot infections, caused by Penicillium expansum. The highest effectivity found in this assay was of about 50%, with strain Weissella cibaria TM128.Selected lactic acid bacteria were tested against Salmonella typhimurium, Escherichia coli and Listeria monocytogenes in Iceberg lettuce and Golden Delicious apples. Lactic acid bacteria interfered efficiently with the growth of S. typhimurium, and L. monocytogenes, but showed little effectivity over E. coli.Finally, dose-response assays were done with Leuconostoc mesenteroides strains CM135, CM160 and PM249 against L. monocytogenes.Among the three strains tested, strain CM160 showed the highest effectivity.
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Shallcross, Jane Amanda. „An investigation into gene probe methods to detect viable foodborne bacteria using Listeria monocytogenes as a model organism“. Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318623.
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Nyenje, Mirriam E. „Genetic and phenotypic characterisation of foodborne bacteria isolated from ready-to-eat foods in Alice, South Africa“. Thesis, University of Fort Hare, 2014. http://hdl.handle.net/10353/d1016109.
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Foodborne illnesses following the ingestion of contaminated food are a major public health problem worldwide. They include a broad group of illnesses ranging from mild to chronic or life-threatening; caused by either toxins released from the disease-causing microbes, or by the microbes themselves. Antimicrobial susceptibility data shows an alarming increase in the frequency of antimicrobial resistance of foodborne pathogens, a situation which is worrisome as it decreases the effectiveness of drugs employed to reduce the morbidity and mortality associated with serious and life-threatening infections and thus, compromising human health. This study was therefore designed to assess the occurrence and characterization of bacterial foodborne pathogens in various foods sold in Alice, Eastern Cape Province of South Africa in an effort to throw more light on the inherent risk associated with such foods. The study was conducted during the period of 2011 - 2013. Two university restaurants and eight ready-to-eat food vending sites in Alice Town were selected based on their prominence to the students, workers and rest of the community. Microbiological analysis was conducted on 252 samples which included vegetables, potatoes, rice, pies, beef and chicken stew. The isolates were identified using biochemical tests and confirmation of the two most prevalent organisms (Listeria ivanovii and Enterobacter cloacae) was done using PCR techniques. The antimicrobial susceptibility profile of Listeria ivanovii and Enterobacter cloacae strains were identified using the disc diffusion technique; minimum inhibitory concentration was determined by the broth dilution method and M.I.C. Evaluator test strips. The microtiter plate adherence assay was employed to ascertain the ability of these isolates to adhere to a surface whereas the role of cell surface properties in biofilm formation was assessed using the coaggregation and autoaggregation assays. The architecture of the formed biofilms was examined under the scanning electron microscope. The virulence and resistant genes were also detected and characterised by sequencing the PCR products. Bacterial growth was present in all the food types tested; organisms isolated included: Listeria spp. (22%), Enterobacter spp. (18%), Aeromonas hydrophila (12%), Klebsiella oxytoca (8%), Proteus mirabilis (6.3%), Staphylococcus aureus (3.2%) and Pseudomonas luteola (2.4%). PCR confirmed 30 (97%) isolates as E. cloacae complex while 44% (22/50) tested positive for L. ivanovii. All the strains of E. cloacae (100%) and 96% of L. ivanovii isolates (based on phenotypic identification) were resistant to at least four or more of the antibiotics. In this study, bla-TEM was also detected from 48 (96%) of L. ivanovii and 30 (100%) of E. cloacae strains; further analysis of the bla-TEM demonstrated the occurrence of bla-TEM-1. Of the 56 bla-TEM-1 positive isolates sequenced, 7% (4/56) had mutation of either insertion or substitution of a nucleotide. Two virulence genes (ucaA and hlyA) were detected in E. cloacae isolates and none in L. ivanovii using PCR. Sequence analysis of the hsp60 gene reported the presence of two sub-species for E. cloacae; E. cloacae cluster III (75%) and E. cloacae cluster IV (25%); while analysis of the iap60 gene demonstrated that 55.8% (19/34) were L. ivanovii, 44% (15/34) L. seeligeri and 14.7% (5/34) L. welshemeri. A total of 90% L. ivanovii and 88% E. cloacae strains demonstrated the ability to form biofilms; the coaggregation index ranged from 12 to 77% while the autoaggregation index varied from 11 to 55% for L. ivanovii and 27% to 98% for E. cloacae. The findings of this study indicate that most of the ready-to-eat food samples examined did not meet bacteriological quality standards, thus posing potential risks to consumers. This should draw the attention of the relevant authorities to certify that hygienic standards are improved to curtain foodborne infections. Furthermore, the presence of multi-resistant strains is of major concern as these foods could serve as important vehicles transmitting multi-resistant bacteria and genes to humans. In addition the ability of these pathogens to form biofilms may lead to adherence of these organisms to kitchen utensils and other environments leading to cross-contamination of food processed in these areas and increase resistance of organisms to antimicrobial agents.
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Qiu, Xujian. „Use of Natural Ingredients to Control Foodborne Pathogens: Antimicrobial Effects and Inhibition Mechanisms“. Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/QiuX2007.pdf.
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Cetin-Karaca, Hayriye. „EVALUATION OF NATURAL ANTIMICROBIAL PHENOLIC COMPOUNDS AGAINST FOODBORNE PATHOGENS“. UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/652.
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Raw and processed foods are vulnerable to contamination during their production, distribution and sale. Thus, a wide variety of chemical preservatives are used in the food industry to prevent the growth of food spoilage and pathogenic bacteria. However, health and economic concerns have led to an intensive search for natural alternatives, such as plant extracts, that can safely be used as substitutes for synthetic antimicrobials and preservatives to partially or completely inhibit the growth of bacteria.
This study evaluated the antimicrobial effects of natural phenolic compounds extracted from vegetables, fruits, herbs and spices. The main objective was to determine the lowest concentration of phenolics to inhibit the visible growth of the pathogenic bacteria which is defined as the minimum inhibitory concentration (MIC).
Some of the most common Gram-positive and Gram-negative foodborne pathogens were treated with several natural phenolic compounds. Concentrations of 5, 10, 15, and 20 ppm (pH 5-6) of each compound were evaluated by broth micro-dilution method and the MICs were determined by using official density (OD) assay. The results demonstrated that the phenolic compounds have varying antimicrobial activities against foodborne pathogens. Natural sources of phenolic compounds contain major antibacterial components and have great potential to be used as natural antimicrobials and food preservatives.
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DeNiro, Julia L. „Airborne Transport of Foodborne Pathogens from Bovine Manure to Vegetable Surfaces“. The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376925440.
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Pollard, Stephanie Kay. „Identification of food safety risks at Virginia farmers' markets and development of a food safety plan to help farmers market managers“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/78196.
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The growing popularity of farmers' markets coupled with a high percentage of produce-related foodborne outbreaks highlights the need for an emphasis on food safety within these markets to protect farmers, patrons and local economies. The number of farmers' markets registered in the United States has almost tripled in the last 15 years. Fresh produce constitutes the majority of food sold at farmers'markets. Between 1998 and 2008, raw produce accounted for almost half of the 4,589 foodborne illness outbreaks linked to a specific commodity. This research was conducted to identify practices at farmers' markets which may contribute to an increased risk of contamination, assess the microbial quality of produce sold at farmers' markets, as well as to develop a food safety management plan template for market managers to utilize to build their own food safety plan.
Using an observational data collection method, risky food safety practices were identified at Southwest Virginia farmers' markets. While market managers and vendors in three of the five markets observed had formal food safety training, numerous risky food safety behaviors were still observed including temperature abuse, cross contamination opportunities, and poor personal hygiene and sanitation. Additionally, the microbial quality of produce from Southwest Virginia farmers' markets was compared to produce sold at retail using culture based microbiological plating and molecular methods. Total aerobic bacteria and coliforms were enumerated, and the presence of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus and generic E. coli were determined. A significantly greater quantity of total aerobic bacteria was isolated from farmers' market leafy greens, onions and tomatoes when compared to a retail grocery store (P=0.0011, P=0.0395, and P<0.0001, respectively). Additionally, one or more target pathogen was isolated from 28 farmers' market samples and 16 retail grocery store samples. The observed risky food safety behaviors along with the bacterial data collected emphasize the need for a pathogen reduction focus on fresh produce not only at farmers' markets, but also with growers and other retail outlets.
To help promote proper food safety practices at farmers' markets, a farmers' market food safety management plan (FSMP) template was developed to address the top five risk factors contributing to foodborne illness as identified by the Centers for Disease Control and Prevention (CDC). The FSMP was evaluated for practicality and feasibility through interviews with market mangers in North Carolina and Virginia. Most market managers (66.7%) agreed that the FSMP was practical for their market while only 33.3% agreed that they could implement the plan immediately. Revisions suggested to the FSMP will be made and it will be made available in Virginia and North Carolina in spring 2016.Ph. D.
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Prévost, Kirkwood Jonah. „Identification of bacteria by infrared imaging with the use of focal plane array Fourier transform infrared spectroscopy“. Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111855.
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The application of infrared imaging employing focal plane array Fourier transform infrared (FPA-FTIR) instrumentation for the identification of bacteria was investigated. FPA-FTIR spectroscopy was shown to provide new opportunities for bacteria identification with unprecedented reliability and throughput by allowing 102--103 FTIR spectra to be acquired simultaneously from surface areas of 90 x 90 to 200 x 200 mum with a spatial resolution of ∼6 mum. The combination of data redundancy and spatial resolution afforded by infrared imaging made it possible to acquire highly reproducible spectra from bacterial films. A protocol for enhancing the reliability of bacteria identification by transmission-mode FPA-FTIR spectroscopy was developed by optimizing spectral acquisition parameters, spectral processing and data analysis; using the differentiation of two Campylobacter species as a test case. The results for this test case were compared with those obtained from three alternate FTIR spectral acquisition modes. The optimized protocol was employed for the generation of a spectral database of foodborne bacteria, containing over 1,000,000 spectra acquired by infrared imaging of 36 species from 19 genera. The development of a modular hierarchical clustering (MHC) model, in combination with the use of a region selection algorithm, allowed all species in the database to be differentiated from each other down to the species level based on differences in their infrared absorption profiles. A validation study involving the identification of well-characterized isolates by comparison of their spectra to those in the database demonstrated the robustness of the MHC model. In a further study employing 44 strains of Clostridium botulinum, the discriminatory power of FPA-FTIR spectroscopy was compared with that of pulsed-field gel electrophoresis, and the region selection algorithm was applied to identify growth medium-independent spectral regions that allowed for the differentiation of Group I and Group II C. botulinum strains in two blind validation studies. The research carried out also demonstrated the high-throughput potential of bacteria identification by infrared imaging when combined with the use of a microarray system for sample deposition. Overall, the novel FPA-FTIR spectroscopy-based bacteria identification protocol developed in this work provides a rapid-response and reagent-free technique suitable for routine use in both food and clinical microbiology laboratories.
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Frederick, Jennifer Leanne. „EVALUATION OF SEPARATION METHOD ADDITIVES FOR THE RECOVERY OF BACTERIA FROM FOOD MATRICES“. UKnowledge, 2012. http://uknowledge.uky.edu/bae_etds/10.
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The microbiological testing of foods is a well-established science. Due to the severity of foodborne pathogen illnesses, the widespread use and implementation of rapid detection methods in food testing labs is increasingly important. The first step for successful testing is sampling. Surfactants have been highly used in food microbiology, but there is not much, if any, published research about the use of fatty alcohols and chemical dispersants as aids in microbial separation. The microbial extraction efficiency of Escherichia coli K12 and Listeria innocua from hot dogs, spinach, and milk was measured using chemical additives (surfactants, fatty alcohols, and a chemical dispersant) in a buffer solution. Dry matter content was calculated using the oven method to determine how clean the sample was at the end of processing. Tween 80 at 0.01% was found to be the most effective additive for microbial recovery for each food matrix examined. The addition of fatty alcohols to surfactants also showed much promise in aiding separation as well as in minimizing dry matter in the final solution. However, the use of Buffered Peptone Water as the diluting agent resulted in very high recovery percentages without the need for additives.
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Rossi, Franca Gabriela. „The use of Lactic Acid Bacteria to control the growth of foodborne pathogens on fresh-cut fruits and sprout vegetables“. DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1559.
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Growing consumer awareness of the health benefits associated with fruits and vegetables and demand for easy to prepare products has prompted the development of a wide variety of minimally processed fruits and vegetables. Minimally processed fruits and vegetables are often peeled, cut, or diced which compromise the produces’ natural protective barriers, exposing a nutrient rich medium and providing an ideal environment for the growth of microorganisms, including foodborne pathogens. The germination conditions of sprout vegetables consisting of relatively high temperatures and humidity, low light and abundance of nutrients are also conducive to the proliferation of foodborne pathogens. Recent outbreaks and recalls indicate additional measures are needed to improve food safety and maintain the integrity of the food industry.
The objective of this research was to evaluate the efficacy of Lactic Acid Bacteria (LAB) against E. coli O157:H7, L. monocytogenes, and Salmonella spp. on apple slices and alfalfa sprouts and it’s influence on product quality. Apple slices inoculated with E. coli O157:H7, L. monocytogenes, and Salmonella spp. (each at 104 CFU/g) were treated with Lb. plantarum alone and in combination with Pediococcus acidophilus and P. pentosaceus (LPP) (107 CFU/g) while alfalfa seeds were inoculated with L. monocytogenes and Salmonella spp. (each at 101 CFU/g and 103 CFU/g) and treated with LPP (107 CFU/g). The growth of the microorganisms on the apple slices was assessed during five and seven days of storage at 4◦C and 20◦C, respectively. Growth on alfalfa seeds was reported during five days of sprouting at 20◦C. Populations of LAB were maintained between 7.0 log CFU/g and 8.0 log CFU/g throughout storage and sprouting on the sliced apples and alfalfa seeds, respectively.
Although LAB had no significant effect on pathogen populations on apple slices during storage at 4°C (p > 0.05), populations were significantly different at 20°C (p < 0.05). Populations of L. monocytogenes in the presence of Lb. plantarum and LPP were 1.84 log CFU/g and 2.84 log CFU/g less than the controls after five days of storage at 20°C (p < 0.05). Populations of E. coli O157:H7 in the presence of Lb. plantarum and LPP were 1.83 log CFU/g and 1.86 log CFU/g less than the control after one and three days of storage, respectively. Finally, populations of Salmonella spp. were 0.86 log CFU/g less than populations in the absence of LPP after three days of storage.
LPP had a significant effect on the growth of L. monocytogenes and Salmonella spp. on alfalfa seeds (p < 0.05). After five days of sprouting, populations of L. monocytogenes at an initial concentration of 101 CFU/g and 103 CFU/g on seeds treated with LPP were approximately 4.5 log CFU/g and 1.0 log CFU/g less than the untreated seeds, respectively. Populations of Salmonella spp. at an initial concentration of 101 CFU/g and 103 CFU/g were 1.0 log CFU/g less than the control.
Overall, on apple slices the combination of Lb. plantarum with P. acidophilum and P. pentosaceus demonstrated greater efficacy than Lb. plantarum alone and reduction of L. monocytogenes by Lb. plantarum and LPP was greater than Salmonella spp. and E. coli O157:H7 on apple slices and alfalfa seeds, alike. LAB had a minimal effect on the quality of the apple slices and alfalfa seeds. LAB could be an effective strategy in reducing pathogen populations at abusive temperatures and germination conditions without influencing the quality of minimally processed fruit and vegetables.
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Abdulmalik, Takiyah. „Use of plant-derived essential oil compounds and naturally-occurring apple flavor compounds to control foodborne pathogens in apple juice“. Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77367.
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Recent demands for minimally-processed foods, has led to the exploration of plant-derived essential oil (EO) compounds as an alternative means of preservation. While some of these compounds are effective against foodborne pathogens, their strong aroma and "spicy" flavor are not compatible with the flavor of juice. The purpose of this research was to evaluate the antimicrobial activity of three EO compounds (thymol, eugenol, and trans-cinnamaldehyde) alone and in combination with three naturally-occurring apple aroma compounds (hexanal, trans-2-hexenal and 1-hexanol) in order to identify combinations that lower the concentrations needed to destroy foodborne pathogens in apple juice.
The standard agar dilution method (SAD) and the Spiral Gradient Endpoint method (SGE) were compared for their abilities to determine minimum inhibitory concentrations (MIC) of the EO compounds. Both methods produced similar patterns of inhibition; however, the MICs produced by the SGE system were significantly higher than those produced by the SAD method of analysis (P<0.05). Since the results produced by the SAD method were more comparable with those published in literature, this method was selected for further testing.
In general, the EO compounds were significantly more effective against the test pathogens (Listeria monocytogenes, Salmonella Typhimurium and Staphylococcus aurues) than were the apple aroma compounds (P<0.05). Cinnamaldehye exhibited the highest degree of activity, followed by thymol and eugenol. Eugenol was the only compound that acted synergistically with the apple aroma compounds.
The most effective compounds (cinnamaldehyde, eugenol and trans-2-hexenal) were then used to inactivate L. monocytogens and S. Typhimurium in preservative-free apple juice. In most cases, treatment with 0.05% of each compound resulted in a 5 log CFU/ml reduction in bacterial numbers following one day of storage at 4°C or 25°C. Likewise, treatment with antimicrobial combinations (containing 0.025% of trans-2-hexenal in combination with 0.025% trans-cinnamaldehyde or eugenol) also resulted in a 5 log CFU/ml reduction in bacterial numbers, following one day of storage at 4°C or 25°C. Since these combinations contained half the effective concentration of the essential oil compounds, they may be used to preserve the microbial quality of apple juice, while reducing the likelihood of off flavors in the final juice product.Ph. D.
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Price, Erin Peta. „Development of novel combinatorial methods for genotyping the common foodborne pathogen Campylobacter jejuni“. Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16601/1/Erin_Peta_Price_Thesis.pdf.
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Campylobacter jejuni is the commonest cause of bacterial foodborne gastroenteritis in industrialised countries. Despite its significance, it remains unclear how C. jejuni is disseminated in the environment, whether particular strains are more pathogenic than others, and by what routes this bacterium is transmitted to humans. One major factor hampering this knowledge is the lack of a standardised method for fingerprinting C. jejuni. Therefore, the overall aim of this project was to develop systematic and novel genotyping methods for C. jejuni.
Chapter Three describes the use of single nucleotide polymorphisms (SNPs) derived from the multilocus sequence typing (MLST) database of C. jejuni and the closely related Campylobacter coli for genotyping these pathogens. The MLST database contains DNA sequence data for over 4000 strains, making it the largest comparative database available for these organisms. Using the in-house software package "Minimum SNPs", seven SNPs were identified from the C. jejuni/C. coli MLST database that gave a Simpson's Index of Diversity (D), or resolving power, of 0.98. An allele-specific real-time PCR method was developed and tested on 154 Australian C. jejuni and C. coli isolates. The major advantage of the seven SNPs over MLST is that they are cheaper, faster and simpler to interrogate than the sequence-based MLST method. When the SNP profiles were combined with sequencing of the rapidly evolving flaA short variable region (flaA SVR) locus, the genotype distributions were comparable to those obtained by MLST-flaA SVR.
Recent technological advances have facilitated the characterisation of entire bacterial genomes using comparative genome hybridisation (CGH) microarrays. Chapter Four of this thesis explores the large volume of CGH data generated for C. jejuni and eight binary genes (genes present in some strains but absent in others) were identified that provided complete discrimination of 20 epidemiologically unrelated strains of C. jejuni. Real-time PCR assays were developed for the eight binary genes and tested on the Australian isolates. The results from this study showed that the SNP-binary assay provided a sufficient replacement for the more laborious MLST-flaA SVR sequencing method.
The clustered regularly interspaced short palindromic repeat (CRISPR) region is comprised of tandem repeats, with one half of the repeat region highly conserved and the other half highly diverse in sequence. Recent advances in real-time PCR enabled the interrogation of these repeat regions in C. jejuni using high-resolution melt differentiation of PCR products. It was found that the CRISPR loci discriminated epidemiologically distinct isolates that were indistinguishable by the other typing methods (Chapter Five). Importantly, the combinatorial SNP-binary-CRISPR assay provided resolution comparable to the current 'gold standard' genotyping methodology, pulsed-field gel electrophoresis.
Chapter Six describes a novel third module of "Minimum SNPs", 'Not-N', to identify genetic targets diagnostic for strain populations of interest from the remaining population. The applicability of Not-N was tested using bacterial and viral sequence databases. Due to the weakly clonal population structure of C. jejuni and C. coli, Not-N was inefficient at identifying small numbers of SNPs for the major MLST clonal complexes. In contrast, Not-N completely discriminated the 13 major subtypes of hepatitis C virus using 15 SNPs, and identified binary gene targets superior to those previously found for phylogenetic clades of C. jejuni, Yersinia enterocolitica and Clostridium difficile, demonstrating the utility of this additional module of "Minimum SNPs".
Taken together, the presented work demonstrates the potentially far-reaching applications of novel and systematic genotyping assays to characterise bacterial pathogens with high accuracy and discriminatory power. This project has exploited known genetic diversity of C. jejuni to develop highly targeted assays that are akin to the resolution of the current 'gold standard' typing methods. By targeting differentially evolving genetic markers, an epidemiologically relevant, high-resolution fingerprint of the isolate in question can be determined at a fraction of the time, effort and cost of current genotyping procedures. The outcomes from this study will pave the way for improved diagnostics for many clinically significant pathogens as the concept of hierarchal combinatorial genotyping gains momentum amongst infectious disease specialists and public health-related agencies.
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Price, Erin Peta. „Development of novel combinatorial methods for genotyping the common foodborne pathogen Campylobacter jejuni“. Queensland University of Technology, 2007. http://eprints.qut.edu.au/16601/.
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Campylobacter jejuni is the commonest cause of bacterial foodborne gastroenteritis in industrialised countries. Despite its significance, it remains unclear how C. jejuni is disseminated in the environment, whether particular strains are more pathogenic than others, and by what routes this bacterium is transmitted to humans. One major factor hampering this knowledge is the lack of a standardised method for fingerprinting C. jejuni. Therefore, the overall aim of this project was to develop systematic and novel genotyping methods for C. jejuni. Chapter Three describes the use of single nucleotide polymorphisms (SNPs) derived from the multilocus sequence typing (MLST) database of C. jejuni and the closely related Campylobacter coli for genotyping these pathogens. The MLST database contains DNA sequence data for over 4000 strains, making it the largest comparative database available for these organisms. Using the in-house software package "Minimum SNPs", seven SNPs were identified from the C. jejuni/C. coli MLST database that gave a Simpson's Index of Diversity (D), or resolving power, of 0.98. An allele-specific real-time PCR method was developed and tested on 154 Australian C. jejuni and C. coli isolates. The major advantage of the seven SNPs over MLST is that they are cheaper, faster and simpler to interrogate than the sequence-based MLST method. When the SNP profiles were combined with sequencing of the rapidly evolving flaA short variable region (flaA SVR) locus, the genotype distributions were comparable to those obtained by MLST-flaA SVR. Recent technological advances have facilitated the characterisation of entire bacterial genomes using comparative genome hybridisation (CGH) microarrays. Chapter Four of this thesis explores the large volume of CGH data generated for C. jejuni and eight binary genes (genes present in some strains but absent in others) were identified that provided complete discrimination of 20 epidemiologically unrelated strains of C. jejuni. Real-time PCR assays were developed for the eight binary genes and tested on the Australian isolates. The results from this study showed that the SNP-binary assay provided a sufficient replacement for the more laborious MLST-flaA SVR sequencing method. The clustered regularly interspaced short palindromic repeat (CRISPR) region is comprised of tandem repeats, with one half of the repeat region highly conserved and the other half highly diverse in sequence. Recent advances in real-time PCR enabled the interrogation of these repeat regions in C. jejuni using high-resolution melt differentiation of PCR products. It was found that the CRISPR loci discriminated epidemiologically distinct isolates that were indistinguishable by the other typing methods (Chapter Five). Importantly, the combinatorial SNP-binary-CRISPR assay provided resolution comparable to the current 'gold standard' genotyping methodology, pulsed-field gel electrophoresis. Chapter Six describes a novel third module of "Minimum SNPs", 'Not-N', to identify genetic targets diagnostic for strain populations of interest from the remaining population. The applicability of Not-N was tested using bacterial and viral sequence databases. Due to the weakly clonal population structure of C. jejuni and C. coli, Not-N was inefficient at identifying small numbers of SNPs for the major MLST clonal complexes. In contrast, Not-N completely discriminated the 13 major subtypes of hepatitis C virus using 15 SNPs, and identified binary gene targets superior to those previously found for phylogenetic clades of C. jejuni, Yersinia enterocolitica and Clostridium difficile, demonstrating the utility of this additional module of "Minimum SNPs". Taken together, the presented work demonstrates the potentially far-reaching applications of novel and systematic genotyping assays to characterise bacterial pathogens with high accuracy and discriminatory power. This project has exploited known genetic diversity of C. jejuni to develop highly targeted assays that are akin to the resolution of the current 'gold standard' typing methods. By targeting differentially evolving genetic markers, an epidemiologically relevant, high-resolution fingerprint of the isolate in question can be determined at a fraction of the time, effort and cost of current genotyping procedures. The outcomes from this study will pave the way for improved diagnostics for many clinically significant pathogens as the concept of hierarchal combinatorial genotyping gains momentum amongst infectious disease specialists and public health-related agencies.
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Jones, Grant Steven. „ROLE OF INTRACELLULAR GROWTH DURING THE GASTROINTESTINAL STAGE OF LISTERIA MONOCYTOGENES INFECTION“. UKnowledge, 2017. http://uknowledge.uky.edu/microbio_etds/13.
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Listeria monocytogenes is a facultative intracellular bacterium that causes foodborne disease in humans. L. monocytogenes invade the gut mucosa and then disseminate, causing systemic infections associated with high mortality rates in immunocompromised individuals. It is unknown how L. monocytogenes traffic to the mesenteric lymph nodes, which represent an important bottleneck for systemic spread. In addition, little is known about the gastrointestinal stage of infection due to the general resistance of mice to oral infection with L. monocytogenes. Our laboratory developed a novel foodborne mouse model of listeriosis utilizing a murinized strain of L. monocytogenes to investigate the gastrointestinal stage of infection. First, we found that the majority of L. monocytogenes isolated from the intestinal tissue and MLN were extracellular; however, the minimal fraction of intracellular L. monocytogenes was vital for persistence in the gut and spread to the MLN. The vast majority of cell-associated L. monocytogenes in the MLN were adhered to inflammatory monocytes, but these cells did not support the intracellular growth of L. monocytogenes. A minor proportion of L. monocytogenes were associated with migratory dendritic cells in the intestinal lamina propria and MLN, but like monocytes, these cells did not appear to serve as an intracellular growth niche for L. monocytogenes. Lastly, extracellular L. monocytogenes were observed migrating in mesenteric lymphatic vessels that drain from the intestine to the MLN, suggesting that L. monocytogenes can spread beyond the intestinal mucosa independent of migratory immune cells. Overall, these studies are the first to characterize the interaction of L. monocytogenes with immune cells in the intestine and MLN following foodborne infection and suggest that extracellular, and not cytosolic L. monocytogenes, primarily drive innate immune responses in the gut.
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Chung, Hyun-Jung. „Control of foodborne pathogens by bacteriocin-like substances from Lactobacillus spp. in combination with high pressure processing“. Columbus, Ohio Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1070416352.
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Thesis (Ph.D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xiv, 182 p.; also includes graphics. Includes abstract and vita. Advisor: Ahmed E. Yousef, Dept.of Food Science and Nutrition. Includes bibliographical references (p. ).
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Camiade, Mathilde. „Persistance de bactéries entériques antibiorésistantes ou pathogénes sur des végétaux de consommation humaine ( modèle la laitue )“. Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR032/document.
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Depuis quelques années, des Toxi-Infections Alimentaires Collectives causées par la contamination de produits frais, comme les laitues, par des bactéries pathogènes entériques (Salmonella, Escherichia coli productrice de shigatoxines -ou STEC-) apparaissent de plus en plus nombreuses. La présence de ces bactéries dans cet environnement inhabituel est un risque sanitaire émergent majeur, d'autant plus que les bactéries entériques, pathogènes ou non, présentent fréquemment des résistances aux antibiotiques. Afin d’étudier la persistance des bactéries antibiorésistantes ou pathogènes sur des laitues, la caractérisation de plasmides de résistance portés par des souches de E. coli issues d’environnements aquatiques contaminés a été réalisé pour, par la suite, étudier leur implication potentielle dans l’adhésion des souches-hôtes sur différentes variétés de laitues. L’étude de la survie et de l’adhésion de souches de E. coli environnementales et de laboratoire, transformées avec les plasmides d’intérêt, sur de jeunes plants de laitues a permis de mettre en évidence trois points : 1) plus le temps de contact entre bactéries et feuilles augmente et moins la survie bactérienne est importante ; 2) il existe une différence de survie et d’adhésion selon les variétés de laitues étudiées ; 3) il existe une différence de survie et d’adhésion entre les souches de laboratoire et les souches environnementales, ces dernières étant en meilleur état métabolique et montrant une adhésion plus importante durant les 11-12 jours d’expérimentation. Après ces constatations de persistance des E. coli antibiorésistantes en conditions contrôlées, des études en champs sur 4 exploitations maraîchères normandes, possédant des itinéraires techniques différents, ont été réalisées. La recherche de pathogènes entériques, Salmonella et STEC, a été effectuée sur les laitues et une recherche de E. coli, témoin de contamination fécale, a été réalisée sur les laitues ainsi que dans l’eau d’irrigation d’un des sites. Les résultats révèlent une qualité microbiologique satisfaisante des parcelles étudiées (selon l’arrêté européen N°2073/2005) bien que des E. coli aient été régulièrement retrouvées au niveau des laitues, dont certaines antibiorésistantes. L’analyse de l’eau d’irrigation a montré la présence continue de E. coli, dont des souches présentant des profils d’antibiorésistance communs à ceux retrouvés sur les laitues, montrant que l’eau d’irrigation est l’une des sources critiques de contamination des végétaux en champsIn recent years, foodborne diseases caused by fresh products contaminated, such as lettuce, with enteric pathogenic bacteria (Salmonella, Shigatoxin-producing Escherichia coli-or STEC-) increasingly. The presence of these bacteria in this unusual environment is a major emerging health risk, especially since enteric bacteria, whether pathogenic or not, are frequently resistant to antibiotics. To study the persistence of antibiotic-resistant or pathogenic bacteria on lettuce, the characterization of resistance plasmids carried by E. coli strains from contaminated aquatic environments was carried out in order to study their potential involvement in adhesion of host strains on different varieties of lettuce. The study of the survival and adhesion of environmental and laboratory E. coli strains, transformed with the plasmids of interest, on young lettuce plants allowed to highlight three points: 1) more time contact between bacteria and leaves increases and less bacterial survival is important; 2) there is a difference in survival and adhesion depending on the varieties of lettuce studied; 3) there is a difference in survival and adhesion between laboratory strains and environmental strains, the latter being in better metabolic state and showing greater adhesion during the 11-12 days of experimentation. After the persistence of antibiotic-resistant E. coli strains under controlled conditions, field studies on 4 Normandy vegetable farms, with different technical itineraries, were carried out. The search for enteric pathogens, Salmonella and STEC, was carried out on lettuce and a search for E. coli, a control of fecal contamination, was realized on the lettuce as well as in the irrigation water of one of the sites. The results reveal a satisfactory microbiological quality of the agricultural plots studied (according to the European decree N ° 2073/2005) although E. coli strains were regularly found at the lettuce level, including some antibiotic resistant. Analysis of the irrigation water showed the continued presence of E. coli strains, including strains with common antimicrobial resistance profiles to those found on lettuce, showing that irrigation water is one of the critical sources of plant contamination in the field
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Andersson, Nadja, und Winroth Markus Petersson. „Det nya måltidskonceptet, salladsbaren : risker vid livsmedelshantering i en offentlig miljö“. Thesis, Högskolan Kristianstad, Sektionen för lärande och miljö, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-16960.
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Inledning: Salladsbarer är ett trendigt och lättillgängligt måltidsalternativ som finns i de flesta dagligvaruhandelsbutiker. Personal och konsumenter hanterar dagligen livsmedel och utrustning vid salladsbaren. Det saknas idag information och kunskap om hur personers beteende kring en salladsbar kan påverka livsmedelssäkerheten. Syfte: Undersöka risker med offentlig livsmedelshantering vid en salladsbar. Metod: Dolda observationer av personal och konsumenters riskbeteende. Hygienkontroll av portionsförpackningar. Bakterieprovtagningar av ytor i anknytning till salladsbaren följt av en artbestämning. Studiens intention är att ge en kvalitativ bild av de hygienutmaningar som livsmedelshantering i en offentlig miljö kan innebära. Resultat/Slutsats: Resultatet av observationerna visar att det sker ett flertal olika riskbeteende i anknytning till salladsbaren, framför allt bland konsumenter, vilket kan leda till korskontamination. Hygienkontrollen visade att medelvärdet av samtliga portionsförpackningar låg inom gränsvärdet för godkänd hygienstandard. Analysen av bakterieprover tagna från olika ytor kopplade till salladsbaren visade att det förekommer en hög variation av olika bakterier. Det finns en risk för bakteriespridning genom personers riskbeteende kopplade till salladsbaren. Risker kan förebyggas genom ökad kunskap och information om hygien och normer för beteende kring salladsbarer.Introduction: Salad bars are a trendy and easily accessible meal option available in most grocery stores. Staff and consumers handle food and equipment at the salad bar daily. There is today no information and knowledge about how people's behavior around a salad bar can affect food safety. Purpose: To investigate risks with public food management at a salad bar. Method: Hidden observations of staff and consumer risk behavior. Hygiene control of portion packages. Bacterial sampling of surfaces associated with the salad bar followed by a species determination. The aim of the study is to provide a qualitative picture of the hygiene challenges that food management in a public environment may imply. Result/Conclusion: The results of the observations show that there are a variety of risk behaviors associated with the salad bar, especially among consumers, which can lead to cross contamination. The hygiene check showed that the average of all portion packages was within the limit of approved hygiene standards. The analysis of bacterial samples taken from different surfaces linked to the salad bar showed that there was a high variety of different bacteria. There is a risk of bacterial spread through people's risk behavior linked to the salad bar. Risks can be prevented through increased knowledge and information on hygiene and norms around salad bars.
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Santos, Leonardo Alves dos. „Estudo da relação estrutural e atividade antimicrobiana da Leucocina C-TA33a de Leuconostoc mesenteroides TA33a /“. Araraquara, 2019. http://hdl.handle.net/11449/183244.
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Orientador: Saulo Santesso GarridoResumo: Os peptídeos antimicrobianos (PAMs) são uma alternativa interessante como bioconservantes de alimentos devido a sua eficiência e, principalmente, à baixa toxicidade quando comparados aos conservantes químicos tradicionais. As bacteriocinas, uma classe de PAMs, têm atividade antimicrobiana em espécies responsáveis pela degradação de alimentos e, portanto, atualmente são exploradas como bioconservadores. A Leucocina C-TA33a (LeuC), um tipo de bacteriocina produzida pela cepa bacteriana Leuconostoc mesenteroides TA33a, é conhecida por ter um amplo espectro antimicrobiano. Estudos de alinhamento da estrutura primária de diferentes bacteriocinas revelaram que LeuC conserva em sua estrutura regiões homólogas também compartilhadas por outras bacteriocinas, como Sacacina P, Bavaricina A e Enterocina A, possivelmente revelando uma importante relação entre essas sequências de aminoácidos e suas atividades antimicrobianas. Este estudo tem como objetivo sintetizar diferentes peptídeos baseados na estrutura primária da Leucocina CTA33a, a fim de identificar as principais regiões responsáveis pela atividade antimicrobiana. Os peptídeos LeuC-Nt, LeuC-0Cys, LeuC-Ala9, LeuC-Ala14 e LeuC-Cys9,14 foram sintetizados por metodologia de fase sólida, purificados e analisados por HPLC e caracterizados por ESI-MS. Ensaios em meio líquido foram realizados para a determinação do percentual de inibição de crescimento microbianos dos peptídeos sobre espécies patogênicas. Os micro-organismos testados fora... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Antimicrobial peptides (PAMs) are an interesting alternative, because biopreservatives present high efficiency and low toxicity when compared to classic preservatives. Bacteriocins, a class of PAMs, have antimicrobial activity in species responsible for food degradation and are currently being exploited as biopreservatives. The Leucocin C-TA33a (LeuC), a type of bacteriocin, is produced by the Leuconostoc mesenteroides TA33a strain and is known for a broad antimicrobial spectrum. Studies of alignment of the primary structure of different bacteriocins revealed that LeuC retains in its structure homologous regions also shared by other bacteriocins, such as Sacacin P, Bavaricin A and Enterocin A, possibly revealing an important relationship between these amino acid sequences and their antimicrobial activities. This study aims to synthesize different peptides based on the primary structure of Leucocin C-TA33a, with the objective of identifying the main regions responsible for antimicrobial activity. The peptides LeuC-Nt, LeuC-0Cys, LeuC-Ala9, LeuC-Ala14 and LeuC-Cys9,14 were synthesized by solid phase methodology, purified by HPLC and characterized by ESI-MS. Liquid assays were performed to determine the percentage of inhibition of microorganisms of the peptides on pathogenic species. The microorganisms tested were Salmonella serotype Typhimurium, Staphylococcus aureus, Escherichia coli and Listeria monocytogenes. Studies were also conducted through circular dichroism, molecular ... (Complete abstract click electronic access below)
Mestre
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Lukanji, Zinathi, und R. N. Ndip. „Isolation and molecular characterization of Bacillus cereus from cow’s raw milk“. Thesis, University of Fort Hare, 2015. http://hdl.handle.net/10353/d1021284.
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Bacillus cereus is a group of ubiquitous facultative anaerobic spore forming Gram-positive rods commonly found in soil. It has been detected and implicated in several contaminated food products and raw milk in dairy farms and it causes foodborne gastroenteritis by producing several toxins. This study is aimed at characterizing virulence determinants of B. cereus from cow‟s raw milk. A total of 400 raw milk samples were collected in Fort Hare Dairy Trust and Middledrift Dairy Farm; and cultured on Polymyxin pyruvate Egg-Yolk Mannitol Bromothymol Agar (PEMBA) for 48 hours at 37°C. DNA was isolated from the isolates and 16S rDNA was amplified and sent to Central Analytical Laboratory for sequencing. The gyrB gene of B. cereus was also used to confirm the identity of the isolates. Antibiotic susceptibility profiles of the isolates together with virulence genes were investigated. Multilocus Sequence typing was used to investigate the genetic relatedness of some selected isolates. Furthermore, spores of the isolates were produced, harvested and their concentrations determined. All (100%) of the isolates were identified as having a 96-99% similarity to B. cereus, B. thuringiensis and B. anthracis using sequencing; while gyrB gene was observed in all (100%) of the isolates. Three virulence genes nheA, nheB, nheC encoding for non haemolysin enterotoxin were amplified in all (100%) the isolates. All (100%) of the isolates were susceptible to doxycycline, gentamycin, tetracycline, ciprofloxacin, chloramphenicol and streptomycin. Resistance to rifampicin and penicillin G was predominant with equal rate of 100%, while susceptibility to erythromycin, clindamycin and doxycycline ranged from 60% to 100%. The selected isolates were related and are descendants of the same ancestor. All (100%) the isolates produced spores. The B. cereus isolates contain virulence genes, has multiple antibiotic drug resistance and produce spores, which poses a health risk to the public and cannot be used as probiotics.
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Snyman, Marina J. „Isolation and antimicrobial susceptibility characterisation of listeria SPP. in selected food premises in Central South Africa“. Thesis, Bloemfontein : Central University of Technology, Free State, 2011. http://hdl.handle.net/11462/138.
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Thesis (M. Tech. Environmental health) -- Central University of technology, Free State, 2011Microbial pathogens play an important role in the food industry where they could cause disease and subsequently significant economic losses. Limited information is available on the situation with regard to Listeria in food products in South Africa. However, much research is being done in the rest of the world on Listeria indicating serious problems as a result of resistance development against various antimicrobial agents, including the organic acids. It is hypothesised that the situation with regard to resistance development may be more serious than generally admitted. Isolation of 200 different food samples was done by using a slightly modified EN ISO 11290-1/A1:2004 standard method. Identification of presumptive positive colonies was confirmed as Listeria by API (Analytical profile index) Listeria. API positive cultures were subjected to 16S rDNA sequencing to compare and confirm identification. Isolates and standard strains were screened for resistance to food preservatives such as organic acids and antibiotics used in the current treatment regime for Listeria infections. The organisms evaluated included isolated strains namely Listeria monocytogenes, Listeria welshimeri, Listeria innocua and their corresponding ATCC (American type culture colletion) strains. An agar dilution method as described by the Clinical and Laboratory Standard Institute (CLSI) was used to determine the minimum inhibitory concentrations (MICs) of 11 antibiotics and 13 organic acids and salts for all the isolates. Overall antibiotic susceptibility patterns of all the isolates indicated high level susceptibility to all the antibiotics tested. Susceptibility to all the organic acids was notably reduced at pH 7 in all the isolates and control strains. Eight highly susceptible strains were selected for induction and represented each of the species isolated. These isolates were exposed to increasing concentrations of three antibiotics and three organic acids. MICs were again determined for all the induced strains for five antibiotics and three organic acids. Proteins extracted from the induced strains were separated on discontinuous SDS-PAGE slab gels to generate total protein profiles. Notable variations were observed in MICs, although induction with antibiotics as well as organic acids did not result in general resistance development. However, evidence was provided that continuous exposure to antimicrobial agents may cause Listeria spp. to develop resistance to different antimicrobial agents. Further research and in depth studies on mechanisms involved in the development of resistance to food preservatives would, therefore, be required. Finally, it is concluded that Listeria monocytogenes may be a possible threat in the Central South African food industry, which deserves more attention. The situation may actually pose a problem that is overseen, because only a small percentage of people that get sick from food, would seek medical advice.
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Ochoa, Mariela L. „Forensic and Proteomic Applications of Thermal Desorption Ion Mobility Spectrometry and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry“. Ohio University / OhioLINK, 2005. http://www.ohiolink.edu/etd/view.cgi?ohiou1113585811.
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41
Lin, Chien-Ju, und 林建汝. „Feasibility Study of Rapid Detection for Foodborne Pathogenic Bacterial by Multiple primers-PCR and PCR-enrichment“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/10614801838677193718.
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碩士國立臺灣海洋大學
食品科學系
95
First part of this study is to develop a combination of multiple primers for the major food poisoning pathogens: Bacillus cereus、Campylobacter jejuni, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., Shigella spp., Staphylococcus aureus and Vibrio parahaemolyticus, and further to investigate the feasibility of applying those primer combination for rapid detection the presence of those pathogens by PCR. The second part of this study is to develop a PCR enrichment technique that can rapidly identify the presence of target pathogen at low number of cells and at a shorter period of incubation time as compared to traditional enrichment procedures. Escherichia coli O157:H7, and Vibrio parahaemolyticus were selected for this part of study. Results indicated that the production of non-specific PCR products will obstruct the interpretation of DNA electrophoretograms with multiple PCR primer combination, and thus make individual identification of those pathogens impossible. Possible approaches to resolve these inferences including categorized primer pair and combination design, Ta (annealing temperature) selection, and target pathogen grouping were suggested for further studies. In PCR enrichment experiment, results suggested that the detection limit can be reduced from 102~103 CFU/ml for traditional selective enrichment procedures to as low as a single cell for both Escherichia coli O157:H7 and Vibrio parahaemolyticus by PCR enrichment technique. Since PCR enrichment technique tends to cause non-specific signal and different primers need respective Ta, it is not suitable for applying on various pathogenic microbes. However, PCR enrichment technique will still be a potential, low costing, time saving, and sensitive methology while the problems of annealing conditions and non-specific PCR reactions are solved.
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Huang, Yen Ying, und 黃彥穎. „Studies on the inhibition of foodborne bacterial pathogens by bacteriocin from Lactococcus lactis DY11212 under various conditions“. Thesis, 1997. http://ndltd.ncl.edu.tw/handle/50607708764245209847.
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碩士國立中興大學
食品科學系
85
Lactococcus lactis DY11212 具有分泌細菌素之能力，該細菌素對格蘭 氏陽性菌具有廣效性的抑制作用，包括 Staphylococcus aureus、 Bacillus cereus 及 Listeria monocytogenes，然本研究所測試之格蘭 氏陰性菌則未或僅受到該細菌素之微弱抑制。使用 10,000 AU/ml 的細菌 素處理五株不同的格蘭氏陰性菌，且於 30 ℃ 培養 60 min，可使菌數降 低 0.1 至 0.3 log CFU/ml，但當與螯合劑 EDTA (50 mM) 共同作用時， 則可使菌數降低 0.3 至 2.2 log CFU/ml。其中以 Salmonella typhi CCRC 10746 最具敏感性，Salmonella typhimurium ATCC 14028 則最不 具敏感性。當使用不同的螯合劑 (100 mM citrate, 50 mM EDTA, 500 mM lactate) 與細菌素合併作用進行試驗時，500 mM lactate 具有最佳的效 果。當於不同 buffer 濃度 (1 mM or 10 mM PBS)、不同培養條件下 (5℃, 30 min or 37℃, 60 min)，以細菌素 (2000 AU/ml) 及 EDTA (50 mM) 對 S. typhmurium ATCC 14028 合併作用，結果顯示低溫下可以得到 較佳的抑制效果。於食品系統中，細菌素 DY11212 可有效降低熟肉中 S. aureus 之初菌數達 3 log CFU/ml，並有效延緩 S. aureus 之生長，使 最大生長菌數 (maximum population density) 較控制組低 0.45 log10 CFU/ml。本實驗亦利用反應曲面法探討細菌素濃度 (S. aureus 0 至 2000 AU/ml，B. cereus 0 至 4000 AU/ml)、溫度 (S. aureus 17.3 ℃ 至 42 ℃，B. cereus 17℃ 至 43 ℃) 及 pH (S. aureus pH 4.5 至 pH 8.9，B. cereus pH 5.5 至 pH 8.5) 對所測試病原菌生長之影響，並以 螺旋平板系統計數菌數。細菌生長曲線則以 Gompertz 方程式進行非線性 迴歸，並用以求得：遲滯時間 (lag phase duration)，對數生長速率 (exponential growth rate)，世代時間 (generation time) 及最大生長 菌數 (maximum population density) 等生長參數。結果顯示 S. aureus 及 B. cereus 之生長皆受到此三因子的影響。尤其是 S. aureus 的遲滯 時間更顯著受到此三因子的影響 (P ＜ 0.001)，其他如 S. aureus 的對 數生長速率及最大生長菌數，受到溫度的影響則較顯著 (P ＜ 0.05)。至 於B. cereus 的對數生長速率，則顯著受到溫度及 pH 的影響。由此可知 細菌素 DY11212 具有顯著抑菌作用，當與其他因子結合作用時，更可有 效抑制細菌生長，使其具有應用於食品上之潛力。 The bacteriocin produced by Lactococcus lactis DY11212 can actively against various gram-positive bacteria such as Staphylococcus aureus, Bacillus cereus and Listeria monocytogenes. However, gram-negative bacteria were weakly or not inhibited by this bacteriocin. When used in combination with chelating agents such as EDTA, this bacteriocin was effective for reducing populations of gram-negative bacteria in vitro. Five strains of gram-negative bacteria were treated in PBS buffer containing purified bacteriocin, alone or in combination with EDTA. Treatments with bacteriocin in buffer resulted in reduction of ca. 0.1 log10 CFU/ml, as compared to untreated controls. Population reductions ranging from 0.3 to 2.2 log10 CFU/ml were observed when cells were treated with bacteriocin and chelator combinations at 37℃ for 60 min. Among the gram- negative microorganisms tested Salmonella typhi CCRC 10746 was the most sensitive one ; Salmonella typhimurium ATCC 14028 was the most resistant one. When S. typhi CCRC 10746 and S. typhimurium ATCC 14028 were treated with different chelators, 500 mM lactate showed the best results. On the other hand, a better inhibition of S. typhimurium ATCC 14028 was achieved when this strain was grown at 5℃. On the cooked meat system, the bacteriocin could decrease the initial colony-forming units and maximum population density of S. aureus by 3 log10 CFU/ml and 0.45 log10 CFU/ml, respectively.In this investigation, response surface analysis was also used to determine the effects and interactions of bacteriocin concentrations (S. aureus 0 to 2000 AU/ml, B. cereus 0 to 4000 AU/ml), temperature (S. aureus 17.3 to 42℃, B. cereus 17 to 43℃) and pH (S. aureus 4.5 to 8.9, B. cereus 5.5 to 8.5) on the growth of S. aureus and B. cereus. Microbial growth was prepared by a spiral system. The growth curves were fit using nonlinear regression with a modified Gompertz equation. Parameter estimates were used to calculate lag phase duration, exponential growth rate, generation time and maximum population density values. The data indicated that the growth kinetics of S. aureus and B. cereus were affected by the three variables, particularly in regard to lag phase duration of S. aureus (P＜0.001). The results also indicated that this bacteriocin had significant bacteriostatic activity against pathogens, particularly when combined with other environmental conditions.
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Leopoldo, Yolanda Patrícia Manuel. „Development of an alginate and shellac microencapsulation system for phages: targeting intestinal foodborne bacterial pathogens on ruminant livestock“. Master's thesis, 2021. http://hdl.handle.net/1822/76535.
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Dissertação de mestrado em BiotecnologiaThis work consisted in the development of a microencapsulation system for the oral administration of bacteriophages (phages) to ruminants, to protect them during their passage through the rumen and the abomasum, releasing them later in the intestine. Ruminants are a major reservoir for some of the most relevant bacterial foodborne pathogens, such as human pathogenic Escherichia coli (e.g., Shiga Toxin-producing E. coli - STEC). Infections with these types of bacteria are often related to foodborne outbreaks, causing complications that can be fatal. Oral administration of phages, which are natural and highly selective antibacterial agents, is one of the most promising strategies to prevent these contaminations. The encapsulation method used was based on the extrusion of the polymers and allowed to form spherical microparticles, through the prilling by vibration technique followed by ionic gelation. Two natural, biodegradable, and biocompatible polymers were used, alginate and shellac (considered safe food additives by the European Food Safety Authority), under conditions of temperature, pH, and mechanical stress not harmful for phages. The microparticles optimized were composed of a mixture of 2 % (w/v) alginate and 3 % (w/v) shellac. By Wide-Field Microscopy, it was possible to determine that their average diameter was 488 ± 16 μm and that they had a spherical morphology. In vitro stability tests showed that the polymeric matrix remained intact at the temperature (38.5 °C) and pH values corresponding to the rumen (pH 5.8, 6.5 and 7) and abomasum (pH 3) and disintegrated at the pH corresponding to the intestine (pH 7.5). Scanning Electron Microscopy was used to verify that the microparticles had a porous surface and a compact interior. Confocal microscopy analysis showed that the 200 nm diameter fluorescent nanospheres, previously encapsulated to simulate phages remained encapsulated for three days of storage and were released when placed in TRIS buffer pH 7.5. The two phages selected as proof of concept were the E. coli phage T4 as a model and the phage CBA120, which is specific for STEC O157:H7, the most common strain of STEC. Phages were encapsulated within the polymeric matrix, then stability tests with encapsulated and free phages were performed, proving that encapsulated phages resisted more at pH 3, compared to free phages, which were totally inactivated at the same pH. These results allow us to conclude that the alginate and shellac microparticles developed in this work, present great potential as an encapsulation system that could help phages to reach the intestine in viable and effective quantities, thus eliminating the target bacteria present there. Subsequently, the method developed here may be applied to different phages and pathogenic bacteria to reduce the high number of foodborne diseases that occur worldwide and are considered a public health issue by the World Health Organization, representing a high socio-economic cost.
Este trabalho consistiu no desenvolvimento de um sistema de micro-encapsulamento para administração oral de bacteriófagos (fagos) a ruminantes, para protege-los durante a passagem pelo rúmen e abomaso, libertando-os posteriormente no intestino. Os ruminantes são um dos principais reservatórios de alguns dos patogénios alimentares bacterianos mais relevantes, como Escherichia coli patogénicas para humanos (ex. STEC, do inglês Shiga toxin-producing E. coli). As infeções por este tipo de bactérias estão frequentemente relacionadas a surtos de doenças alimentares, provocando complicações que podem ser fatais. A administração oral de fagos, que são agentes antibacterianos naturais e altamente seletivos, é uma das estratégias mais promissoras para evitar estas contaminações. O método de encapsulamento utilizado baseou-se na extrusão dos polímeros e permitiu formar micropartículas esféricas através da técnica de prilling by vibration seguida de gelificação iónica. Foram utilizados dois polímeros naturais, biodegradáveis e biocompatíveis, o alginato e a shellac (considerados aditivos alimentares seguros pela European Food Safety Authority), em condições de temperatura, pH e stress mecânico não prejudiciais para os fagos. As micropartículas optimizadas são constituídas por uma mistura de 2 % (w/v) alginato and 3 % (w/v) shellac. Através de Microscopia Wide-Field foi possível determinar que o seu diâmetro médio era de 488 ± 16 μm e que estas possuíam uma morfologia esférica. Os testes in vitro realizados mostraram que a matriz polimérica manteve-se intacta à temperatura (38.5 °C) e aos valores de pH correspondentes ao rúmen (pH 5.8, 6.5 e 7) e ao abomaso (pH 3) e desintegrou-se no pH respetivo ao intestino (pH 7.5). Foi utilizada Microscopia Eletrónica de Varrimento, que permitiu verificar que as micropartículas apresentavam uma superfície porosa e um interior compacto. A análise por Microscopia Confocal mostrou que as nano-esferas fluorescentes de 200 nm de diâmetro, encapsuladas previamente para simular os fagos, mantiveram-se encapsuladas durante três dias de armazenamento e foram libertadas quando colocadas em tampão TRIS pH 7.5. Os dois fagos selecionados como prova de conceito foram, o T4 que é um fago modelo de E. coli e o CBA120 que é específico para STEC O157:H7, a estirpe mais comum de STEC. Após o encapsulamento dos fagos na matriz polimérica, testes de estabilidade foram realizados com fagos encapsulados e livres, provando que os fagos encapsulados resistiram mais ao pH 3, comparativamente aos fagos livres, que foram totalmente inativados no mesmo pH. Estes resultados permitem concluir que as micropartículas de alginato e shellac desenvolvidas neste trabalho, apresentam grande potencial como sistema de encapsulamento que poderá ajudar os fagos a chegar ao intestino viáveis e em quantidades eficazes, eliminando assim as bactérias alvo aí presentes. Posteriormente, a técnica aqui desenvolvida poderá ser aplicada para diferentes fagos e bactérias patogénicas, no sentido de reduzir o elevado número de doenças alimentares que ocorrem mundialmente e são consideradas um problema de saúde pública pela Organização Mundial de Saúde, representando um elevado custo a nível socioeconómico.
Agradeço também ao projeto PhageSTEC, financiado pela FCT (POCI-01-0145-FEDER-029628), que ajudou a suportar este trabalho.
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May, Fiona J. „Epidemiology of foodborne and emerging infectious diseases in Australia, 2014 to 2015“. Phd thesis, 2015. http://hdl.handle.net/1885/109815.
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My placement was with the Zoonoses, Foodborne and Emerging
Infectious Diseases section in the Office of Health Protection at
the Australian Government Department of Health during 2014-2015.
I focused on the following five projects.
I described the epidemiology of bacterial toxin mediated
foodborne outbreaks in Australia and identified risk factors and
risk groups, from an analysis of outbreak data recorded from 2001
to 2013. The main risk factor for bacterial toxin mediated
foodborne outbreaks is temperature abuse (storage between 4C and
60 C) of solid masses of foods, such as lasagna. Residents of
aged care facilities were the group at highest risk of illness
and death from bacterial toxin mediated foodborne outbreaks. Few
outbreaks were identified with food prepared at home.
As part of the national response to the large outbreak of Ebola
virus disease (EVD) in West Africa (2014-2015), a national
surveillance system was established to enable reporting and to
provide information to jurisdictions to assist monitoring of
travellers at risk of contracting EVD. I conducted an evaluation
of this system. The system was considered useful and achieved its
aims; however a coordinated central, online database would
improve reporting and ease of use.
Culture independent diagnostic testing (CIDT) for bacterial
causes of gastroenteritis is becoming commonly used in pathology
laboratories in Australia. These tests are rapid, cheap and
require less technical expertise than traditional culture based
laboratory tests. However, these tests do not provide the
subtyping information required for public health surveillance,
including outbreak detection. For the time being, laboratories
are continuing culture in addition to CIDT. My project documents
this transition in Queensland.
In May 2014, three cases of bacteraemia caused by Ralstonia
species were diagnosed in South Australia. The only common
exposure was propofol, a sedative. An investigation into the
cause of this cluster of cases was led by the Therapeutic Goods
Administration (TGA) as the agency responsible for the regulation
of propofol. Additional cases were identified from Queensland
(four cases), and Victoria (one case). I was part of the
epidemiology team assisting and advising the TGA. The
investigation incorporated evidence from the case series,
molecular analysis of isolates (including whole genome
sequencing), assessment of causal association and expert
consultation through the Delphi method. The cases of Ralstonia
bacteraemia were determined to be associated with at least two
separate exposures. Cases in Queensland were linked to
contaminated bottled water, while cases in South Australia and
Victoria were associated with propofol. The mechanism of
contamination of the propofol was unable to be determined.
During a multi-jurisdictional investigation into an outbreak of
hepatitis A associated with consumption of frozen mixed berries
in 2015, a national case control study was conducted. I assisted
OzFoodNet Queensland with interviewing controls and conducted a
sub-analysis of cases and controls from Queensland. Frozen mixed
berries were the only food exposure with a statistically
significant association with illness, supporting the implication
of frozen mixed berries as the source of the outbreak, as
indicated by traceback and microbiological evidence.
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Gandhi, Kalpesh K. „Bacillus subtilis endospore coat protein solubilization methods for studying effects of high pressure precessing“. Thesis, 2002. http://hdl.handle.net/1957/27290.
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Spores of foodborne pathogens such as Clostridium botulinum,
Clostridium perfringens and Bacillus cereus are widely distributed in nature.
Presence of those spores in food products, particularly C. botulinum spores in
vacuum packed, ready-to-eat low-acid products, is a great safety concern. The
research here described is a first effort towards understanding the role of the
spore coat proteins in the inactivation of bacterial spore using high pressure
processing. This study proposes a coat protein solubilization methodology
using non-ionic detergents minimizing protein damage and compatible with
spectroscopy methods. The methodology developed here was compared with
approaches proposed in the literature with respect to protein yield, protein
fractions identified, amino acid composition and suitability with spectroscopy
techniques for the further analysis of coat proteins.
Bacillus subtilis ATCC 6633 spore coat proteins were solubilized
(n=3) using octyl-β-D-glucopyranoside (OGP) at room temperature and
urea/sodium dodecyl sulphate (UDS) at 37C and 70C. Analysis of variance
(ANOVA) showed no significant (95% confidence) differences between the
three repetitions of the three spore coat protein solubilization methods. Protein
yield was significantly larger (95% confidence) when using UDS at 70C as
compared to UDS at 37C. OGP gave the lowest protein yield but allowed circular dichroism (CD) analysis of the spore coat protein solution with
minimum blank signal. SDS-PAGE revealed that the UDS-70C coat protein
solutions consisted of five major and six minor proteins ranging 6 to 65 kD
while the OGP solution appear to consist of four major and nine minor bands
in the same mw range. Amino acid analysis of the protein extracted by the
OGP method was conducted using reverse phase HPLC (RP-HPLC) and
compared with published information. The OGP spore coat protein solution
showed a higher proportion of aspartate, glutamate, alanine and tyrosine.
Pressure, heat and time effects were studied on spore coat proteins
obtained from untreated and pressure-treated B. subtilis ATCC 6633 spores.
Pressure treatments of spores, and of extracted spore coat protein solutions, at
50 kpsi (345 mPa) and 85 kpsi (586 mPa) for 10 and 30 min at constant 85C
along with appropriate heat- and pressure-only controls and untreated sample,
were used to study the effect of pressure, heat and time on spore coat proteins.
Both spore coat protein solubilization procedures showed a significant
reduction in protein yield for pressure-only, heat-only and pressure/heat treated
spores when compared with untreated spores. When OGP-solubilized proteins
from untreated spores were pressure treated, SDS-PAGE profile showed an
increasing overall band intensity with increasing pressure and time. In the case
of protein solution obtained from pressure-treated spores the electrophoretic
pattern showed the loss of higher molecular weight proteins.
The significance of this study is that for the first time we have observed
extensive changes on spore coat proteins caused by pressure, as well as heat
treatments. Future studies will examine what is the probable physiological role
of the proteins damaged by these physical treatments. An advantage of the
protein solubilization here developed will allow the application of
spectroscopy techniques to characterize changes in spore coat proteins.Graduation date: 2003
46
Chen, SH. „Campylobacter persistence in poultry processing“. Thesis, 2020. https://eprints.utas.edu.au/34817/1/Chen_whole_thesis.pdf.
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The Foodborne Illness Reduction Strategy 2018-2021+ released by Australia's Food Regulation Secretariat regards Campylobacter as one of the main foodborne pathogens requiring actions at all points along the food supply chain. The ultimate objective of this thesis was to help poultry processors understand the impact of current processing strategies and develop better hurdle interventions to reduce Campylobacter numbers and prevalence on chicken meat products during slaughter, which may reduce the burden of disease currently associated with this pathogen. Five aims were established for the thesis and included: 1) understanding the impact of current processing interventions on the bacterial numbers and diversity on chicken carcasses throughout commercial processing; 2) mapping changes of the bacterial community on carcasses throughout processing to the end of shelf life and to link the data to the processing environment; 3) developing an in vitro model to test Campylobacter inactivation under mimicked poultry processing conditions; 4) using the in vitro model to evaluate peracetic acid (PAA) as a potential antimicrobial agent in reducing Campylobacter; 5) understanding the potential mechanisms for C. jejuni survival during a 45 min treatment of a sub-lethal of PAA by examining timedependent global proteomic expression.
Currently the success of commercial poultry processing lines is measured based on culture-based microbiological analysis, e.g. total bacterial population, count of Campylobacter, etc. This approach is unable to provide information on the entire bacterial community diversity and the importance of Campylobacter in the community in terms of its abundance and relationships with other microbes including those microbes that are not able to be isolated at various processing steps. More recently, the use of chlorine-based disinfectants has been questioned in terms of its effectiveness and potential harm to human health. Looking for alternative processing aids is in demand by the poultry industry and consumers. By completing the aforementioned aims, this thesis will utilise culture-independent techniques along with well-established culture-based methods to fill the gaps outlined, understand indepth the microbial profiles of commercial processing systems and test PAA as a potential antimicrobial aid that could be considered for the replacement of chlorine-based disinfectants.
Two different types of poultry processing lines from a single abattoir in Australia, Line A and Line B, were examined. The major differences between Line A and B included: 1) Line A operates with separate steps of scalding, defeathering and plucking, whereas Line B incorporates these three steps together in a confined tunnel, and 2) the time length of immersion chilling (Line A 0.5 h and Line B 1.5 h) and air chilling (Line A 1.5 h and Line B 0.5 h) were different. Both lines produced significant declines (p <0.001) of the bacterial counts on carcasses through scalding and immersion chilling with no decrease through air chilling. However, the confined tunnel in Line B may elevate the temperature inside the tunnel and select and distribute thermoduric/thermophilic bacteria between carcasses, as the results of the culturebased and culture-independent approaches indicated the high level of presence of Campylobacter and Anoxybacillus. Psychrotolerant bacteria dominated bacterial community on carcasses after air chilling from Line A, while immersion chilling in Line B showed a greater impact on the bacterial diversity on carcasses than air chilling. Together with the bacterial diversity through chilling in Line A and B, it was noted that the longer the time that a particular chilling process occurs for (either immersion chilling or air chilling), the greater the change in the bacterial diversity. Furthermore, the culture-independent approach suggested: 1) each sampled processing step acted as a contamination source by distinctively changing the bacterial diversity on carcasses, and 2) Campylobacter was revealed to be a minor but persistent component in the bacterial community on carcasses through processing.
Acknowledging the importance of scalding and chilling in reducing bacterial loads on carcasses, a poultry processing in vitro model was developed to mimic the poultry processing system. This model consisted of three laboratory-based food matrices (buffered peptone water (BPW), chicken breast meat and a meat-based broth utilising chicken breast meat to reflect the protein concentration of an immersion chilling tank) and eight processing conditions including scalding alone (54.5°C and 57°C), chilling alone, scalding + chilling, chilling with PAA (80 ppm) and scalding + chilling with PAA. PAA was added to the in vitro model to evaluate its impact on two poultry C. jejuni strains, strain 2674 and strain 2704. The meat-based broth showed a greater Campylobacter inactivation when comparing chilling with PAA to chilling without PAA, indicating the usefulness of PAA during immersion chilling even with the presence of organic matter. The condition of chilling with PAA in BPW and the chicken breast meat demonstrated the greatest Campylobacter inactivation, even greater than the combined condition of scalding + chilling with PAA in the respective food matrices. This indicates a hypothesis that prior scalding may activate a heat shock stress response that also cross-protects against oxidative stress from PAA exposure.
To validate this hypothesis, it is important to understand how Campylobacter survives when subjected to a sub-lethal level of PAA over a period of exposure. Therefore, the global proteomic responses of Campylobacter poultry strain 2704 in a sub-lethal PAA (60 ppm) treatment over a 45 min time course was determined by using the sequential window acquisition of all theoretical fragment-ion spectra-mass spectrometry (SWATH-MS) protein analysis method. Amongst 591 proteins identified across 0, 15, 30 and 45 min PAA treatments, 108 proteins (~6.2% of all proteins identified from the genome) were differentially expressed based on logarithmic two-fold changes. The hypothesis was supported by the detection of two heat stress proteins, Lon protease (Lon) and 10 kDa chaperone (GroS). Other than two heat stress proteins, proteins in the energy production, amino acid-related metabolism, cell mobility and oxidative response were found to be abundant. By comparing changes in the proteome profile across time points (15, 30 and 45 min), Campylobacter was found to actively respond to PAA in the first 15 min and then reached a status quo from 30 to 45 min.
In summary, this thesis contributes to further understanding the impact of current poultry processing strategies in terms of how they influence the bacterial diversity on chicken carcasses at various processing steps. Campylobacter was determined to be a minor but persistent component in the bacterial community on carcasses with high prevalence after processing. This suggest that more effort is required to reduce the level of Campylobacter in poultry processing in Australia. The environmental attributes during chilling have an important influence on the bacterial diversity on carcasses through processing. Minimizing levels of heat stress proteins of Campylobacter when implementing PAA during commercial poultry processing is recommended. Together with all the findings in this thesis, it is probably most practical to add PAA in post-chill dipping tanks at the end of processing or spray PAA onto chicken carcasses during air chilling than add PAA in immersion chilling tanks in order to achieve improved Campylobacter reduction.
The findings in this thesis may prove to be of value to Australian poultry processors, to develop better processing hurdles to control Campylobacter and limit the public health burden through reducing human Campylobacter illness cases as set out by the Foodborne Illness Reduction Strategy 2018- 2021+.
47
Chang, Ju-Mei, und 張洳楣. „A study of bacterial foodborne outbreaks in Taiwan and the survival of Escherichia coli O157:H7 and Salmonella Typhimurium in iceberg lettuce and their detection by the multiplex-PCR“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/32834130137965215845.
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博士中興大學
食品暨應用生物科技學系
95
With the increasing international trade of the agri-food chain, it is more important than ever that systems for the control of hazards and management of food safety be established with operating principles that are unambiguous and acceptable worldwide. In Taiwan, the Department of Health (DOH) is responsible for ensuring the microbiological safety of foods that enter into national markets. Significant changes in the life styles of developing countries have taken place during the past decade, especially in the food preparation facilities and industry, as well as in food safety. The surveillance for foodborne illness has been stressed because of centralization of food production and increased international trade and tourism. During 1991 to 2000, 274 outbreaks of foodborne illness including 12,845 cases and 3 deaths were reported in central Taiwan. Of the 274 reported outbreaks, 171 were caused by bacterial pathogens, while chemical and natural toxins appeared to be the minor causes. Microorganisms, particularly Bacillus cereus (41.2%, 113 of 171 outbreaks), Staphylococcus aureus (17.9%, 49 of 171 outbreaks), Vibrio parahaemolyticus (15.7%, 43 of 171 outbreaks) were the main etiologic agents. The microbiological safety of fresh produce is a significant concern of consumers and industry. An increasing number of outbreaks caused by Escherichia coli O157:H7 and Salmonella spp. associated with lettuce consumption are reported worldwide. In this study we (1) investigate the survival and growth behavior of E. coli O157:H7 and S. enterica serovars Typhimurium inoculated on lettuce and water at 4℃ (14 days) and 22℃ (7 days); (2) examine the antimicrobial effect of rice vinegar (acetic acid) on the population of E. coli O157:H7 on chopped lettuce treated with rice vinegar for 5 min at 25℃ (Small inoculum 104 CFU g-1; large inoculum 107 CFU g-1). The results showed that at the end of 4℃ storage, populations of two pathogens in lettuce and water decreased approximately 1 log CFU g-1. However, microbial levels on shredded lettuce increased 3 logs within 3 days at 22℃. Methods based on PCR (polymerase chain reaction) for the detection of E. coli O157:H7 and Salmonella in food have been developed recently. A multiplex PCR assay for concurrent identification of E. coli O157:H7 or Salmonella using eaeA, stx1/stx2, invA, ST11 and ST15 primers were developed. Under the optimum conditions, the assay yielded a 228-bp product and 397-bp product from E. coli O157:H7, a 284-bp product and 429-bp product from Salmonella, respectively. The results showed that PCR method allowed E. coli O157:H7 and Salmonella with a low population (1-10 CFU/g) in fruits and vegetables be detected within 27 h protocol. Hence, the multiplex PCR assay can potentially be a simple, rapid and efficient tool presumptive and simultaneously screening of produce for contamination by E. coli O157:H7 and Salmonella. Besides, to decrease the health risk to human and environment from exposure to pesticides, the government samples and analyzes agricultural products for pesticide residues to enforce the limits set by Department of Health every year. The objectives in this study are: (1) to collect and analyze the data of pesticide residues in vegetables and fruits in central Taiwan; (2) to compare the statistics of pesticide residues data in vegetables and fruits in four regions of Taiwan; and (3) to introduce the Hazard Analysis Critical Control Point (HACCP) system to industries and growers of vegetables and fruits for improving the safety of agricultural products.
48
Ngwenya, Lloyd. „Microbiological analysis of bacterial pathogens in poultry feeds and water resources in Blouberg Poultry Value Chain Project, Limpopo Province, South Africa“. Thesis, 2019. http://hdl.handle.net/10386/2961.
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Thesis (M.Sc. Agriculture (Animal Production)) -- University of Limpopo, 2019Poultry is a good source of animal protein for many households due to its affordability. However, it is prone to bacterial infections which can be passed on to consumers, hence chickens that are reared without constant health checks present a potential health threat to humans. The objective of the study was to identify the zoonotic bacterial pathogens in poultry feeds and water resources in Blouberg poultry value chain project. A total of 88 samples comprising of 14 feed samples, 14 water samples, 60 mouth and rectal swab samples were collected from the farms. The samples were screened for the presence of Escherichia coli, Salmonella spp. and Shigella spp. through selective cultivation. Only coliforms and the dominant isolates were identified as Escherichia coli, Klebsiella spp., and Enterobacter spp., Salmonella and Shigella spp. were not detected in all the samples. E. coli strains that were isolated from the water sources and mouth and rectal swabs of the chickens showed a significant resistance to gentamycin, neomycin, penicillin, streptomycin, tetracycline, erythromycin, nalidixic acid, ciprofloxacin and ampicillin (p<0.05). Klebsiella pneumoniae showed resistance to neomycin; penicillin; erythromycin (p<0.05) while K. oxytoca and E. absuriae showed similar antibiotic resistance profile as penicillin, erythromycin, nalidixic acid and ampicillin. E. coli and K. pneumonia are mostly implicated in poultry disease outbreaks and they are enteric pathogens in humans as well. The presence of pathogens in poultry presents a great risk of secondary infection in humans and this will lead to socio-economic problems for the affected communities. The information generated in this study will guide the relevant stakeholders who handle poultry feeds and water resources in following good management practices. 1
National Research Foundation (NRF)
49
(5929649), Rishi Drolia. „CELLULAR AND MOLECULAR MECHANISM OF LISTERIA ADHESION PROTEIN-MEDIATED BACTERIAL CROSSING OF THE INTESTINAL BARRIER“. Thesis, 2021.
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The crossing of host barriers (intestinal, blood-brain, and placental) is a critical step for systemic infections caused by entero-invasive pathogens. In the intestine, the epithelial cells are the first line of defense against enteric pathogens. Listeria monocytogenes is a facultative-intracellular foodborne pathogen that first crosses the intestinal barrier to cause a systemic infection. However, the underlying mechanism is not well understood.
We demonstrate that Listeria adhesion protein (LAP) promotes the translocation of L. monocytogenes across the intestinal barrier in mouse models (A/J and C57BL/6). Relative to the wild-type (WT; serotype 4b) or the isogenic bacterial invasion protein Internalin A mutant (ΔinlA) strain, the lap─ strain showed significant defect in translocation across the intestinal barrier and colonization of the mesenteric-lymph nodes, liver and spleen in the early phase of infection (24 h and 48 h). LAP induces intestinal epithelial barrier dysfunction for increased translocation as evidenced by increased permeability to 4-kDa FITC-dextran (FD4), a marker of paracellular permeability, in the serum and urine of WT and ΔinlA- infected mice and across Caco-2 cell barrier, but not the lap─ mutant strain. Microscopic examination confirmed localization of the WT and ΔinlA strains in the tight junction, a crucial barrier of intestinal paracellular permeability, in the mouse ileal tissue but the lap─ strain remained confined in the lumen. LAP also upregulates TNF-α and IL-6 in intestinal epithelia of mice and in Caco-2 cells for increased permeability.
Investigation of the underlying molecular mechanisms of LAP-mediated increase in intestinal permeability by using lap─ mutant strain, purified LAP and shRNA-mediated Hsp60 suppression, we demonstrate that LAP interacts with its host receptor, Hsp60, and activates the canonical NF-κB signaling, which in turn facilitates myosin light-chain kinase (MLCK)-mediated opening of the epithelial barrier via the cellular redistribution of major epithelial junctional proteins claudin-1, occludin, and E-cadherin. Pharmacological inhibition of NF-κB or MLCK in cells or genetic ablation of MLCK in mice (C57BL/6) prevents mislocalization of epithelial junctional proteins, intestinal permeability and L. monocytogenes translocation across the intestinal barrier.
Furthermore, LAP also promotes L. monocytogenes translocation across the intestinal barrier and systemic dissemination in a Mongolian gerbil that are permissive to the bacterial invasion proteins; InlA-and InlB-mediated pathways; similar to that in humans. We show a direct LAP-dependent and InlA-independent pathway for L. monocytogenes paracellular translocation across the intestinal epithelial cells that do not express luminally accessible E-cadherin. Additionally, we show a functional InlA/E-cadherin interaction pathway that aids L. monocytogenes translocation by targeting cells with luminally accessible E-cadherin such as cells at the site of epithelial cell extrusion, epithelial folds and mucus-expelling goblet cells. Thus, L. monocytogenes uses LAP to exploit epithelial innate defense in the early phase of infection to cross the intestinal epithelial barrier, independent of other invasion proteins.
This work fills a critical gap in our understanding of L. monocytogenes pathogenesis and sheds light to the complex interplay between host-pathogen interactions for bacterial crossing of the crucial intestinal barrier.
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Zeng, Shi-Chin, und 曾詩琴. „Development of the Liposome Immunoassay for Foodborne Pathogenic Bacteria“. Thesis, 2006. http://ndltd.ncl.edu.tw/handle/65831128613029014381.
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碩士國立暨南國際大學
應用化學系
94
Salmonellae are ubiquitous human pathogens that have been associated with foodborne illness for over a hundred years. Though they do not cause serious complications in healthy individuals, Salmonellae do pose a danger to the elderly and children, who have weak immune systems. Due to the increased number of outbreaks of human illness associated with the consumption of contaminated products in the United States and many other countries, there is an urgent need to develop rapid assays to detect common foodborne pathogens. This study demonstrates that it is feasible to use methyl blue (MB), a visible dye, entrapped inside liposomes as a detectable label. Immunoliposomes tagged with anti-Salmonella common structural antigens (CSA) encapsulating MB dye were used as the signal amplifier for the development of a field-portable colorimetric immunoassay to detect Salmonellae. For the preparation of immunoliposomes, the N-succinimidyl-S-acetylthioacetate (SATA) derivative of the antibodies (anti-Salmonella CSA) was reacted with the activated N-(k-Maleimidoundecanoyloxy) sulfo-succinimide ester (sulfo-KMUS) derivative of dipalmitoyl-phosphatidylethanolamine (DPPE), which was incorported into the liposomes bilayer. A plastic-backed nitrocellulose strip with two immobilized zones was the basis for a sandwich assay. The first zone was the antigen capture zone (AC zone), used in a sandwich (noncompetitive) assay format; the other was the biotin capture zone (BC zone), used as a quality control index for the strip assay. During the capillary migration of the wicking reagent containing 80 L of immunoliposomes and 40 L of the test sample (heat-killed S. typhimurium), sample pathogens with surface-bound immunoliposomes were captured at the AC zone, while the unbound immunoliposomes continued to migrate and bind to the anti-biotin antibodies coated on the BC zone. The color density of the AC zone was directly proportional to the number of Salmonella typhimurium in the test sample. The detection limit of the current assay with heat-killed Salmonella typhimurium was 1,680 cells. The cross-reactivity of the proposed immunoassay was also investigated, and pathogens including E. coli O157:H7 and Listeria genus specific caused no interference with the detection of Salmonella typhimurium. The surface topographical image of the prepared nitrocellulose membrane was analyzed using atomic force microscopy (AFM) for the monitoring of the antibody immobilization and immunorecognition reactions.