Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Poultry transport coops are rarely washed and demonstrate to be a major point of broiler carcass contamination. Our laboratory hypothesized that foaming disinfectants and cleaners commonly used within processing plants may be used to clean and disinfect poultry transport coops. The objective of this study was to evaluate treatments consisting of a low-pressure water rinse (LPWR), a foaming additive alone, foaming cleaner or peroxyacetic acid with a foaming additive to reduce bacteria on broiler transport coops. A high-pressure water rinse (HPWR) applied prior to and following treatments was also evaluated. Homogenized feces was evenly applied to the floors of pre-cleaned transport coops and allowed to dry. The first study used fresh layer feces and evaluated the treatments ability to reduce aerobic bacteria from the manure. The second study added a HPWR step to determine whether this technique would reduce bacteria. In the third study, Salmonella Typhimurium was added to the homogenized fecal slurry to evaluate how effectively these methods reduce aerobic bacteria and Salmonella on coop surfaces. The field study utilized laboratory treatments proven to be most effective on freshly soiled broiler integrator coops. All foaming treatments were applied using a compressed air foam system (CAFS) using a 1 inch fire hose. Ten minutes post-treatment, all surfaces were rinsed with a LPWR for 30 seconds to remove residual disinfectant. Samples were collected from the transport coops prior to and following treatments utilizing a flame sterilized 5 x 5 cm stainless steel template and a gauze swab pre-applied with buffered peptone water. All samples were stomached, serially diluted, spread plated onto agar plates, incubated for 24 h at 37° C and enumerated. The foam cleaner and peroxyacetic acid with a foam additive significantly reduced (P < 0.05) aerobic bacteria up to 4.84 to 5.17 logs, respectively when compared to the LPWR. The addition of a HPWR following product application significantly reduced bacteria on integrator coops, in the field study, but didn’t improve efficacy of our treatments in laboratory trials. These data suggest that a CAFS may be used in combination with disinfectants and cleaners to reduce bacteria on poultry transport coops.

Avaliação dos procedimentos de limpeza e desinfecção de superfícies realizados em restaurantes comerciais self-service do município de São Paulo. Introdução Os procedimentos de higienização têm como objetivo controlar os microrganismos para diminuir a deterioração dos alimentos e minimizar os riscos de ocorrência das Doenças Transmitidas por Alimentos (DTAs), sendo indispensáveis para a garantia da qualidade e inocuidade dos alimentos. As DTAs, na maioria das vezes, são ocasionadas por microrganismos e a contaminação acontece nos pontos finais de preparo de alimentos restaurantes; atualmente, são um dos maiores problemas de saúde pública mundial. Objetivos Analisar os procedimentos de limpeza e desinfecção realizados em restaurantes comerciais self-service do município de São Paulo, verificar a sua conformidade aos requisitos técnicos e legais, identificar facilidades e dificuldades na adoção de procedimentos adequados e investigar as ações da fiscalização sanitária referentes aos procedimentos de higienização. Método Estudo descritivo mediante levantamento, realizado através de entrevistas individuais com os responsáveis pelos restaurantes, aplicando-se um questionário, em uma amostra por critério de acesso, sendo voluntária a participação dos entrevistados. Resultados Em 14,3 por cento dos estabelecimentos investigados os procedimentos estavam em conformidade com as legislações; apenas 23,8 por cento dos locais estudados usavam produtos adequados; somente em 23,8 por cento dos locais avaliados possuíam treinamento estruturado; em 47,6 por cento dos restaurantes estudados não havia qualquer exigência de escolaridade na contratação; as atividades consideradas fáceis, pela maioria, foram: aquisição de produtos adequados, controle da concentração de produtos químicos, aplicação de ações corretivas e avaliação de resultados; as consideradas difíceis, pela maioria, foram: elaboração de procedimentos e treinamentos; e, cerca de 60,0 por cento dos locais estudados passaram por fiscalização sanitária, porém os dados indicam a necessidade de uma atuação mais criteriosa. Conclusões Os melhores resultados foram obtidos nos locais que possuíam responsáveis técnicos, sendo possível identificar que as falhas nos procedimentos de higienização estavam associadas, principalmente, à falta de conhecimentos e/ou capacitação no que tange as variáveis determinantes de sua eficácia e legislações pertinentes. Recomendações São necessárias ações para: informar e formar os empresários do setor, aprimorar os conhecimentos dos profissionais técnicos da área alimentícia e dos funcionários das empresas fornecedoras de produtos químicos / Evaluation of surfaces cleaning and disinfection procedures carried out in commercial self-service restaurants of the city of São Paulo. Introduction Sanitation procedures aim at controlling microorganisms to diminish food deterioration and minimizing the risks of foodborne disease. They are indispensable quality and food safety insurance. The foodborne disease are most frequently caused by microorganisms with contamination taking place at the final point of food preparation restaurants, which currently poses one of the major problems of world public health. Objectives Analyzing the cleaning and disinfection procedures taking place in commercial restaurants self-service of the city of São Paulo, verifying their compliance with technical and legislation requirements, identifying the levels of difficulty in the adoption of adequate procedures and investigating sanitary surveillance actions concerning sanitation procedures. Method - Descriptive study survey obtained by means of the application of voluntary response individual interviews with restaurant technical supervisors in charge in an accessibility criterion sample. Results In 14.3 per cent of the investigated restaurants the procedures were found to be in accordance with legislation; only 23.8 per cent of the institutions in sample used adequate products and only 23.8 per cent presented structured in-service training. 47.6 per cent of the studied restaurants demanded no schooling level on hiring. The activities seen as easy were mostly: adequate product acquisition, chemical products concentration control, rectifying action application and result evaluation. The actions deemed difficult by the most of the respondents were procedure scheme design and service training. About 60.0 per cent restaurants were object of sanitary surveillance but data indicate the need for strict sanitary surveillance action. Conclusions - The best results were obtained in the restaurants presenting technical supervisors. It was possible to identify that the flaws in sanitation procedures were mainly associate to the lack of knowledge and/or qualification in relation to the efficacy variable determinants and pertinent legislation. Recommendations Actions geared at informing and qualifying the sector entrepreneurs and bettering the knowledge of the technical and chemical product suppliers personnel are needed

La capacité de Listeria monocytogenes à adhérer et à persister sur les surfaces dans les ateliers agro-alimentaires pendant de longues périodes malgré l’application correcte et fréquente des opérations de nettoyage & désinfection (N&D), peut être responsable de la contamination croisée de produits alimentaires par simple contact avec une surface contaminée. De plus, il est important de prendre en considération la présence potentielle de bactéries viables non cultivables (VNC) qui ne sont pas détectées par les méthodes culturales utilisées lors de la recherche de L. monocytogenes dans un prélèvement de surface.Un des objectifs a été de vérifier si les milieux de culture conventionnels fréquemment utilisés pour les expérimentations en laboratoire étaient représentatifs des conditions environnementales des ateliers agro-alimentaires et de définir pour la suite des expérimentations un milieu synthétique pouvant modéliser une souillure alimentaire. Pour assurer la sécurité sanitaire des aliments et préserver la santé des consommateurs, optimiser les opérations d’hygiène est une nécessité. Dans ce but, la survie des cellules adhérentes de L. monocytogenes soumises à des conditions simulant en laboratoire l’alternance des phases de N&D et de production a été étudiée. Plusieurs facteurs pouvant influencer la survie de ces cellules ont été pris en considération et combinés par un plan d’expériences fractionnaire : la souillure alimentaire, la souche de L. monocytogenes, le matériau de surface, la présence d’une souche de Pseudomonas fluorescens qui favorise l’adhésion de L. monocytogenes et le scénario de l’opération d’hygiène. Dans les industries agro-alimentaires, les bactéries sont soumises à de nombreux stress, nécessitant pour survivre l’expression et l’induction appropriées de gènes et de protéines de réponse aux stress. Les mécanismes de réponse aux stress mis en place par les cellules de L. monocytogenes adhérentes après stress hydrique (dessiccation), stress chimique (N&D) et stress froid ont été déterminés par une analyse transcriptomique.Selon les critères étudiés (croissance, forces d’adhésion, distribution spatiale et état physiologique des cellules adhérentes), il s’avère que le milieu TSB/5m peut modéliser le jus de saumon fumé. Au contraire, aucun des milieux synthétiques testés ne permet de remplacer l’utilisation de l’exsudat de viande pour mimer les conditions de terrain. Concernant les facteurs influençant la survie de L. monocytogenes, les opérations d’hygiène impactent uniquement la cultivabilité des cellules adhérentes ; toutefois, le séchage des surfaces permet une optimisation de l’efficacité de la procédure de N&D, d’autant plus lorsqu’il est réalisé quotidiennement / Despite the correct and frequent application of cleaning & disinfection (C&D), Listeria monocytogenes has the ability to adhere to and persist on surfaces in food processing plants for long periods. Consequently, L. monocytogenes may be responsible for cross-contamination of food through contact with contaminated surfaces. In addition, it is important to consider the potential presence of viable but non culturable (VBNC) bacteria that are not detected by the microbiological methods used in the research of L. monocytogenes in a surface sample.One aim was to verify whether the conventional culture media commonly used for laboratory experiments were representative of the environmental conditions of food processing plants and define for further experiments a synthetic medium that can model a food soil. Optimization of the C&D procedures is a necessary to ensure food safety and protect the health of consumers. For this purpose, the survival of L. monocytogenes adherent cells subjected to laboratory conditions simulating alternating phases of C&D and production was studied. Several factors that may influence the survival of these cells were considered and combined with a fractional factorial design, including: the food soil, the strain of L. monocytogenes, the surface material, the presence of a strain of Pseudomonas fluorescens, which enhances the adhesion of L. monocytogenes, and the scenario of the sanitation procedure. Moreover, in the food industry, bacteria can be subject to many stresses; thus, the expression and induction of appropriate genes and stress response proteins are required for survival. The stress response mechanisms set up by the adherent L. monocytogenes cells after hydric stress (i.e. desiccation), chemical stress (i.e. C&D), and cold stress were determined by a transcriptomic analysis.According to the criteria studied (i.e. growth, adhesion forces, spatial distribution, and physiological state of adherent cells), TSB/5m medium was found to be a sufficient model for smoked salmon juice. In contrast, none of the tested synthetic media can replace the use of meat exudate to mimic field conditions. About the factors influencing the survival of L. monocytogenes, C&D procedures were found to only impact the culturability of adherent cells; however, drying surfaces were found to optimize the effectiveness of the C&D procedures, especially when performed daily

Avaliação dos procedimentos de limpeza e desinfecção de superfícies realizados em restaurantes comerciais self-service do município de São Paulo. Introdução Os procedimentos de higienização têm como objetivo controlar os microrganismos para diminuir a deterioração dos alimentos e minimizar os riscos de ocorrência das Doenças Transmitidas por Alimentos (DTAs), sendo indispensáveis para a garantia da qualidade e inocuidade dos alimentos. As DTAs, na maioria das vezes, são ocasionadas por microrganismos e a contaminação acontece nos pontos finais de preparo de alimentos restaurantes; atualmente, são um dos maiores problemas de saúde pública mundial. Objetivos Analisar os procedimentos de limpeza e desinfecção realizados em restaurantes comerciais self-service do município de São Paulo, verificar a sua conformidade aos requisitos técnicos e legais, identificar facilidades e dificuldades na adoção de procedimentos adequados e investigar as ações da fiscalização sanitária referentes aos procedimentos de higienização. Método Estudo descritivo mediante levantamento, realizado através de entrevistas individuais com os responsáveis pelos restaurantes, aplicando-se um questionário, em uma amostra por critério de acesso, sendo voluntária a participação dos entrevistados. Resultados Em 14,3 por cento dos estabelecimentos investigados os procedimentos estavam em conformidade com as legislações; apenas 23,8 por cento dos locais estudados usavam produtos adequados; somente em 23,8 por cento dos locais avaliados possuíam treinamento estruturado; em 47,6 por cento dos restaurantes estudados não havia qualquer exigência de escolaridade na contratação; as atividades consideradas fáceis, pela maioria, foram: aquisição de produtos adequados, controle da concentração de produtos químicos, aplicação de ações corretivas e avaliação de resultados; as consideradas difíceis, pela maioria, foram: elaboração de procedimentos e treinamentos; e, cerca de 60,0 por cento dos locais estudados passaram por fiscalização sanitária, porém os dados indicam a necessidade de uma atuação mais criteriosa. Conclusões Os melhores resultados foram obtidos nos locais que possuíam responsáveis técnicos, sendo possível identificar que as falhas nos procedimentos de higienização estavam associadas, principalmente, à falta de conhecimentos e/ou capacitação no que tange as variáveis determinantes de sua eficácia e legislações pertinentes. Recomendações São necessárias ações para: informar e formar os empresários do setor, aprimorar os conhecimentos dos profissionais técnicos da área alimentícia e dos funcionários das empresas fornecedoras de produtos químicos / Evaluation of surfaces cleaning and disinfection procedures carried out in commercial self-service restaurants of the city of São Paulo. Introduction Sanitation procedures aim at controlling microorganisms to diminish food deterioration and minimizing the risks of foodborne disease. They are indispensable quality and food safety insurance. The foodborne disease are most frequently caused by microorganisms with contamination taking place at the final point of food preparation restaurants, which currently poses one of the major problems of world public health. Objectives Analyzing the cleaning and disinfection procedures taking place in commercial restaurants self-service of the city of São Paulo, verifying their compliance with technical and legislation requirements, identifying the levels of difficulty in the adoption of adequate procedures and investigating sanitary surveillance actions concerning sanitation procedures. Method - Descriptive study survey obtained by means of the application of voluntary response individual interviews with restaurant technical supervisors in charge in an accessibility criterion sample. Results In 14.3 per cent of the investigated restaurants the procedures were found to be in accordance with legislation; only 23.8 per cent of the institutions in sample used adequate products and only 23.8 per cent presented structured in-service training. 47.6 per cent of the studied restaurants demanded no schooling level on hiring. The activities seen as easy were mostly: adequate product acquisition, chemical products concentration control, rectifying action application and result evaluation. The actions deemed difficult by the most of the respondents were procedure scheme design and service training. About 60.0 per cent restaurants were object of sanitary surveillance but data indicate the need for strict sanitary surveillance action. Conclusions - The best results were obtained in the restaurants presenting technical supervisors. It was possible to identify that the flaws in sanitation procedures were mainly associate to the lack of knowledge and/or qualification in relation to the efficacy variable determinants and pertinent legislation. Recommendations Actions geared at informing and qualifying the sector entrepreneurs and bettering the knowledge of the technical and chemical product suppliers personnel are needed

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Técnicas de limpeza química ou mecânica são comumente empregadas para evitar a formação de biofilmes e problemas associados com a colonização de superfícies por micro-organismos. Neste trabalho, amostras de aço inox 304L foram submetidas a ensaios acelerados de crescimento de biofilme, o qual foi posteriormente removido por tratamentos de limpeza e desinfecção (choque térmico com água a 70C por 1h, limpeza com ácido fosfórico 20 % v/v por 30min e desinfecção com peróxido de hidrogênio 0,17 % v/v por 1h). Com o objetivo de verificar a influência destes tratamentos na remoção do biofilme, este foi caracterizado (por quantificação microbiana e análises de espectroscopia de impedância eletroquímica - EIE), antes e após a aplicação dos tratamentos. Dois casos foram estudados. No primeiro caso, simularam-se condições presentes em tubulações de ambientes hospitalares e sistemas de distribuição de água quente. O micro-organismo utilizado foi a bactéria Serratia marcences. O processo de formação de biofilme e posterior limpeza e desinfecção foi realizado de modo contínuo durante 15 semanas. Os resultados de quantificação microbiana e de EIE mostraram que desde a primeira semana de exposição e ao longo dos ensaios, formou-se um biofilme aderente à superfície do aço e que o emprego dos tratamentos de limpeza e desinfecção não foi eficaz na remoção do biofilme. Em um segundo caso, simularam-se condições presentes em tubulações da indústria de água mineral, empregando-se a bactéria Pseudomonas aeruginosa. Neste caso, as técnicas de limpeza e desinfecção foram aplicadas individualmente e em conjunto. A aplicação de choque térmico, assim como da limpeza ácida, sobre um biofilme com 72 h de formação foi capaz de eliminar as bactérias viáveis, presentes na superfície do aço. Entretanto, a desinfecção com peróxido de hidrogênio não foi capaz de eliminá-las. Nas duas condições, porém, as análises de EIE do sistema aço/biofilme mostraram que o mesmo não foi completamente removido da superfície do metal. Correlacionando os dois casos, pode-se inferir que a superfície do aço inox 304L é rapidamente colonizada pelas duas espécies microbianas e que as técnicas de limpeza e desinfecção são capazes de reduzir e até eliminar as células viáveis, embora não removam completamente o biofilme da superfície. Por outro lado, é importante ressaltar que fatores como a arquitetura, espessura e porosidade do biofilme, e propriedades intrínsecas da superfície, são fatores que afetam os valores de impedância medidos, sendo necessário considerá-los na análise, tanto da formação do biofilme, quanto dos efeitos dos procedimentos de limpeza e desinfecção / Techniques for chemical or mechanical cleaning are usually employed to prevent the formation of biofilm and the problems associated with the colonization of surfaces by micro-organisms. In this work, samples of 304 L stainless steel were submitted to experiments of accelerated growth of biofilm, which was subsequently removed by cleaning and disinfection treatment (heat shock with water at 70 C for 1h, cleaning with phosphoric acid 20% v/v for 30 min and disinfection with hydrogen peroxide 0,17% v/v for 1h). In order to verify the influence of these treatments on biofilm removal, analyses of microbial quantification and electrochemical impedance spectroscopy (EIS), before and after the treatments were employed. Two cases were studied. In the first case, it was simulated the conditions found in piping for hospital environment and systems for the distribution of hot water. The micro-organism used was the bacteria Serratia marcences. The process of biofilm formation and subsequent cleaning and disinfection was performed continuously for 15 weeks. The results of measurement of microbial and EIS showed that since the first week of exposure and during the testing, an adherent biofilm was formed on the steel surface and that the use of cleaning and disinfecting treatments were not effective in removing biofilm. In a second case, it was simulated the conditions present in the pipes of the mineral water industry, using the bacterium Pseudomonas aeruginosa. In this case, the cleaning and disinfection techniques were applied individually and as a whole. The application of heat shock, as well as acid cleaning, to the biofilm formated after 72 h was able to eliminate the viable bacteria present in the steel surface. However, disinfection with hydrogen peroxide was not able to eliminate them. In both conditions, however, the EIS analysis of the steel/biofilm system showed that it was not satisfactorily removed from the metal surface. Comparing the two cases, it can be inferred that the surface of 304L stainless steel is rapidly colonized by the two microbial species studied and that the cleaning and disinfection techniques are able to reduce and even eliminate viable cells, although they could not completely remove the biofilm from the surface. On the other hand, it is important to note that factors such as properties of the electrode surface (roughness, porosity and adsorption), the electrode potential, and the architecture, thickness and porosity of the biofilm, are factors that affect the measured impedance values, it is necessary to consider them in the analysis of biofilm formation and effects of cleaning and disinfection

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Técnicas de limpeza química ou mecânica são comumente empregadas para evitar a formação de biofilmes e problemas associados com a colonização de superfícies por micro-organismos. Neste trabalho, amostras de aço inox 304L foram submetidas a ensaios acelerados de crescimento de biofilme, o qual foi posteriormente removido por tratamentos de limpeza e desinfecção (choque térmico com água a 70C por 1h, limpeza com ácido fosfórico 20 % v/v por 30min e desinfecção com peróxido de hidrogênio 0,17 % v/v por 1h). Com o objetivo de verificar a influência destes tratamentos na remoção do biofilme, este foi caracterizado (por quantificação microbiana e análises de espectroscopia de impedância eletroquímica - EIE), antes e após a aplicação dos tratamentos. Dois casos foram estudados. No primeiro caso, simularam-se condições presentes em tubulações de ambientes hospitalares e sistemas de distribuição de água quente. O micro-organismo utilizado foi a bactéria Serratia marcences. O processo de formação de biofilme e posterior limpeza e desinfecção foi realizado de modo contínuo durante 15 semanas. Os resultados de quantificação microbiana e de EIE mostraram que desde a primeira semana de exposição e ao longo dos ensaios, formou-se um biofilme aderente à superfície do aço e que o emprego dos tratamentos de limpeza e desinfecção não foi eficaz na remoção do biofilme. Em um segundo caso, simularam-se condições presentes em tubulações da indústria de água mineral, empregando-se a bactéria Pseudomonas aeruginosa. Neste caso, as técnicas de limpeza e desinfecção foram aplicadas individualmente e em conjunto. A aplicação de choque térmico, assim como da limpeza ácida, sobre um biofilme com 72 h de formação foi capaz de eliminar as bactérias viáveis, presentes na superfície do aço. Entretanto, a desinfecção com peróxido de hidrogênio não foi capaz de eliminá-las. Nas duas condições, porém, as análises de EIE do sistema aço/biofilme mostraram que o mesmo não foi completamente removido da superfície do metal. Correlacionando os dois casos, pode-se inferir que a superfície do aço inox 304L é rapidamente colonizada pelas duas espécies microbianas e que as técnicas de limpeza e desinfecção são capazes de reduzir e até eliminar as células viáveis, embora não removam completamente o biofilme da superfície. Por outro lado, é importante ressaltar que fatores como a arquitetura, espessura e porosidade do biofilme, e propriedades intrínsecas da superfície, são fatores que afetam os valores de impedância medidos, sendo necessário considerá-los na análise, tanto da formação do biofilme, quanto dos efeitos dos procedimentos de limpeza e desinfecção / Techniques for chemical or mechanical cleaning are usually employed to prevent the formation of biofilm and the problems associated with the colonization of surfaces by micro-organisms. In this work, samples of 304 L stainless steel were submitted to experiments of accelerated growth of biofilm, which was subsequently removed by cleaning and disinfection treatment (heat shock with water at 70 C for 1h, cleaning with phosphoric acid 20% v/v for 30 min and disinfection with hydrogen peroxide 0,17% v/v for 1h). In order to verify the influence of these treatments on biofilm removal, analyses of microbial quantification and electrochemical impedance spectroscopy (EIS), before and after the treatments were employed. Two cases were studied. In the first case, it was simulated the conditions found in piping for hospital environment and systems for the distribution of hot water. The micro-organism used was the bacteria Serratia marcences. The process of biofilm formation and subsequent cleaning and disinfection was performed continuously for 15 weeks. The results of measurement of microbial and EIS showed that since the first week of exposure and during the testing, an adherent biofilm was formed on the steel surface and that the use of cleaning and disinfecting treatments were not effective in removing biofilm. In a second case, it was simulated the conditions present in the pipes of the mineral water industry, using the bacterium Pseudomonas aeruginosa. In this case, the cleaning and disinfection techniques were applied individually and as a whole. The application of heat shock, as well as acid cleaning, to the biofilm formated after 72 h was able to eliminate the viable bacteria present in the steel surface. However, disinfection with hydrogen peroxide was not able to eliminate them. In both conditions, however, the EIS analysis of the steel/biofilm system showed that it was not satisfactorily removed from the metal surface. Comparing the two cases, it can be inferred that the surface of 304L stainless steel is rapidly colonized by the two microbial species studied and that the cleaning and disinfection techniques are able to reduce and even eliminate viable cells, although they could not completely remove the biofilm from the surface. On the other hand, it is important to note that factors such as properties of the electrode surface (roughness, porosity and adsorption), the electrode potential, and the architecture, thickness and porosity of the biofilm, are factors that affect the measured impedance values, it is necessary to consider them in the analysis of biofilm formation and effects of cleaning and disinfection

Ce travail de thèse concerne l'étude de l'écologie microbienne d'un atelier de découpe de viande bovine, dans le but de mieux comprendre la persistance bactérienne, c'est-à-dire, la présence répétée d'un même clone bactérien pendant une longue période malgré l'application bien conduite et régulière du nettoyage et de la désinfection (N-D). Des prélèvements par « chiffonnages » multiples de surfaces d'équipements ont été réalisés lors de trois campagnes de prélèvement espacées les unes des autres d'au moins six mois. Les prélèvements ont été réalisés sur un tapis convoyeur en polychlorure de vinyle (PVC) et sur des machines éplucheuses en acier inoxydable avant et après N-D. Nous avons quantifié les cellules totales (les cellules vivantes et les cellules mortes) par PCR quantitative en temps réel (qPCR), les cellules viables par EMA-qPCR, et les UFC (provenant de cellules cultivables) par dénombrement après incubation à 25°C sur gélose tryptone soja. Les résultats montrent qu'avant N-D, les cellules totales (en moyenne 5,6 – exprimé en log10 cellules/cm2 – sur PVC et 4,7 sur acier inoxydable) sont plus nombreuses que les cellules viables (4,5 sur PVC et 4,4 sur acier inoxydable) lesquelles sont plus nombreuses que les UFC (3,8 sur PVC et 2,9 sur acier inoxydable). Le N-D entraîne moins d'une réduction décimale (RD) des populations à l'exception des UFC sur acier inoxydable qui subissent 1,5 RD en moyenne. Ce dernier chiffre s'explique par des forces d'adhésion faibles. L'étude de la diversité des bactéries cultivables montre que sur un total de 51 genres identifiés, 13 seulement sont retrouvés lors des trois campagnes de prélèvements. Les isolats de ces 13 genres représentent 75, 72 et 62% des isolats des campagnes1, 2 et 3 respectivement. Parmi ces isolats, les plus fréquents sont (par ordre décroissant du nombre d'isolats) : Pseudomonas, Staphylococcus, Microbacterium, Acinetobacter, Chryseobacterium, Psychrobacter et Kocuria. Le génotypage d'isolats de 3 genres majoritaires (Staphylococcus, Pseudomonas et Acinetobacter) montre qu'une seule souche, Staphylococcus equorum, est sans aucun doute persistante. L'ensemble de ces observations montrent que l'écosystème varie d'une campagne à une autre. Ces modifications de la diversité bactérienne reflèteraient les modifications de flores des viandes traitées dans l'atelier, qui ont des origines multiples. En outre, il apparaît que, contrairement à ce qui est généralement admis, les bactéries à coloration de Gram négative cultivables sont plus facilement inactivées par le N-D que les bactéries à coloration de Gram positive. L'étude de l'écosystème par PCR-DGGE a permis d'identifier sept genres bactériens et montre que les espèces dominantes sont toutes sous forme vivante, autrement dit, aucune des espèces dominantes n'a été détectée uniquement sous forme de cellules mortes. Sur les sept genres identifiés six sont des Gram – dont majoritairement les genres Acinetobacter, Pseudomonas et Psychrobacter. Cette dominance montre que le N-D permet une forte perte de cultivabilité des bactéries Gram – mais qu'une grande partie n'est pas détachée. La dominance des bactéries Gram – observée par PCR-DGGE masque les staphylocoques qui ne sont pas détectés alors qu'ils sont majoritaires parmi la flore cultivable. Seul un genre bactérien, Propionibacterium, est identifié par PCR-DGGE uniquement mais il n'est trouvé qu'à une seule campagne et uniquement sur l'acier inoxydable avant N-D. En conclusion, l'avancée majeure de ce travail est la mise en évidence qu'une proportion importante de bactéries survit après les opérations très poussées de N-D mais pour une période transitoire. / The aim of this work is to acquire a better knowledge of the microbial ecology of a beef processing plant to understand bacterial persistence, e.g. the presence of a clone isolated several times on several visits in the same processing plant despite regular Cleaning and disinfection (C&D) procedures. Successive swabbing were performed on a PVC conveyor belt and skinning machines made of stainless steel before and after C&D during three surveys in minimal 6 month-intervals. Total cells (live and dead cells) were quantified using real-time quantitative PCR (qPCR). Viable cells e.g. cells with intact membrane, were assessed using Ethidium Monoazide combined with qPCR. Culturable cells (CFU) were determined from plate counts on Tryptone Soy Agar. Before C&D, total cells (5.6 log cells/cm2 and 4.7 log10 cells/cm2 on PVC and stainless steel respectively) were greater than viable cells (4.5 and 4.4 log10 cells/cm2) and CFUs (3.8 and 2.9 log10 CFU/cm2). C&D lead to less than 1 log10 reduction in bacterial populations except for CFU counts on stainless steel where a 1.5 log reduction is observed. This result is highlighted by the weak attachment strengths observed on stainless steel for CFUs. Identification of the culturable microbiota revealed that out of 51 genera identified, 13 were found at all the visits. These genera represented 75, 72 and 62% of the total isolates. The most frequently identified bacteria were Pseudomonas, Staphylococcus, Microbacterium, Acinetobacter, Chryseobacterium, Psychrobacter and Kocuria. Molecular typing of three dominant genera (Staphylococcus, Pseudomonas and Acinetobacter) showed that only one strain, Staphylococcus equorum, was persistent in the premises. Our results show that the microbial ecosystem is different from one survey to another, which reflect the various geographical origins of meat products. Contrary to widespread belief, Gram negative strains were more easily eliminated by C&D than Gram positive strains. Furthermore, the microbial diversity assessed by PCR-DGGE allowed the identification of 7 genera. This molecular approach showed that dominant species are all in a viable state: none of these species was solely detected in a dead state. Of the 7 genera identified, 6 were Gram negative, Acinetobacter, Pseudomonas and Psychrobacter being predominant. This result highlights that C&D induced the lost of culturability of Gram negative bacteria although a high proportion was not detached from the surface. The predominance of Gram negative microflora, didn’t allow the detection of staphylococcal isolates which were numerous in the culturable microflora. One genus, Propionibacterium, isolated in one survey on stainless steel before C&D was only identified by PCR-DGGE. In conclusion, the present study has demonstrated that a large proportion of bacteria can survive drastic cleaning and disinfection for a transient period.