München, Techn. Univ., Diss., 2004.

Tierärztl. Hochsch., Diss., 2003--Hannover.

Thesis (MSc Food Sc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Listeria monocytogenes is a foodborne pathogen that has been isolated from a variety of food sources. It is the cause of the food-borne disease, listeriosis that shows symptoms such as meningitis, encephalitis and abortion. Different strains of L. monocytogenes exist and not all are thought to be pathogenic to humans. The aim of this study was to evaluate and compare conventional methods, culturing on selective (Oxford agar) and chromogenic (RAPID’L.mono agar) media, as well as speciesspecific and multiplex polymerase chain reaction (PCR) methods for the detection and identification of 94 L. monocytogenes isolates from various areas in an avocado processing facility, as well as the final product. To achieve a better understanding of the genetic diversity of the confirmed L. monocytogenes strains isolated from the avocado facility, two subtyping techniques, PCR-restriction fragment length polymorphism (PCR-RFLP) and pulsed-field gel electrophoresis (PFGE), were employed. All of the isolates were identified as Listeria species on both Oxford and RAPID’L.mono agar. On the RAPID’L.mono agar, 76 of the 94 isolates produced colonies typical of L. monocytogenes, with the remaining 18 showing colonies typical of L. innocua (n=13) and L. ivanovii (n=5). The species-specific PCR successfully amplified a 730 base pairs region of the hly gene of 80 of the 94 isolates. For the same 80 isolates the multiplex PCR successfully amplified 800, 517 and 238 base pair (bp) fragments of the inlA, inlC and inlJ genes, respectively. The remaining 14 isolates included the 13 isolates identified as L. innocua, as well as an isolate identified as L. monocytogenes on RAPID’L.mono. The results obtained on the Oxford agar showed a 100 % positive correlation when compared to the PCR results in identifying Listeria species, while the RAPID’L.mono had a 4 % false negative result in identifying L. monocytogenes compared to the PCR results. Sixty-four of the confirmed L. monocytogenes isolates were subtyped using PCRRFLP and PFGE. For the PCR-RFLP analysis, a 733 bp fragment of the inlA gene was successfully amplified for all of the isolates, followed by digestion with the restriction enzymes, AluI and Tsp509I. AluI produced three different banding patterns and Tsp509I produced two different banding patterns. Subtyping of the isolates using PFGE was carried out by macrorestriction of the genomic DNA with ApaI and AscI. The restriction fragments were resolved by PFGE and the fingerprints were classified into four clusters. In the combined analyses, cluster I contained forty-eight isolates (n=48), cluster II 1 isolate (n=1), cluster III fifteen isolates (n=15) and cluster IV 1 isolate (n=1). The PCR-RFLP results had a 98 % correlation with the PFGE results. The results of this study indicated inconsistencies between the results obtained by conventional and molecular detection methods for the identification of L. monocytogenes. Species-specific and multiplex PCR, however, proved useful to accurately detect and identify L. monocytogenes in a shorter period of time and could replace the use of conventional agar during identification. Both PCR-RFLP and PFGE proved useful in the subtyping of L. monocytogenes isolates with the PCR-RFLP being less expensive and results obtainable in a shorter period of time. / AFRIKAANSE OPSOMMING: Listeria monocytogenes is ‘n patogeen afkomstig van voedsel wat uit ‘n verskeidenheid voedselbronne geisoleer kan word. Dit is die oorsaak van die voedsel afkomstigde siekte, listeriosis met simptome soos harsingvliesontsteking, ensefalitis en aborsie. ‘n Verskeidenheid L. monocytogenes stamme bestaan, maar nie almal word as patogenies beskou nie. Die doel van hierdie studie was om konvensionele metodes, naamlik mikrobiologiese kweking op selektiewe (Oxford agar) en chromatografiese (RAPID’L.mono agar) media, sowel as spesies-spesifieke en multipleks polimerase ketting reaksie (PKR) metodes te evalueer en vergelyk vir die deteksie en identifikasie van 94 L. monocytogenes isolate geisoleer vanuit verskeie areas in ‘n avokado prosesseringsfasiliteit sowel as die finale produk. Om ‘n beter begrip van die genetiese diversiteit van die isolate wat as L. monocytogenes bevestig is te verkry, is twee subtiperingstegnieke, PKR-restriksiefragmentlengte polimorfisme (PKR-RFLP) en pulsveld jel-elektroforese (PVJE) toegepas. Beide Oxford en RAPID’L.mono agar het al die isolate as Listeria spesies geidentifiseer. Op die RAPID’L.mono agar het 76 van die 94 isolate kolonies tipies van L. monocytogenes gevorm, 13 kolonies was tipies van L. innocua (n=13) en vyf kolonies tipies van L. ivanovii (n=5). Die spesies-spesifieke PKR het ‘n 730 basis paar (bp) streek van die hly geen suksesvol geamplifiseer vir 80 van die 94 isolate. Die multipleks PKR het 800, 517 en 238 bp fragmente van die inlA, inlC and inlJ gene onderskeidelik, vir dieselfde 80 isolate suksesvol geamplifiseer. Die oorblywende 14 isolate het die 13 isolate wat as L. innocua geïdentifiseer is en die een isolaat wat as L. monocytogenes op RAPID’L.mono geïdentifiseer is ingesluit. Resultate verkry met die Oxford agar het 100 % ooreengestem met die PKR resultate vir die identifikasie van Listeria spesies. Die RAPID’L.mono het ‘n 4 % vals negatiewe resultaat gelewer in vergelyking met die PKR resultate. Vier-en-sestig van die bevestigde L. monocytogenes isolate is gesubtipeer deur PKR-RFLP en PVJE. Tydens die PKR-RFLP analise is ‘n 733 bp fragment van die inlA geen suksesvol geamplifiseer, gevolg deur vertering met die restriksie-ensieme, AluI and Tsp509I. AluI het drie verskillende bandpatrone opgelewer en Tsp509I twee verskillende bandpatrone. Subtipering deur PVJE is uitgevoer deur makro-restriksie van die genomiese DNA met ApaI en AscI. Die restriksie fragmente is geskei deur PVJE en die vingerafdrukke is in vier groepe geklassifiseer. Groep I het 48 isolate (n=48), groep II 1 isolaat (n=1), groep III 15 isolate (n=15) en groep IV 1 isolaat (n=1) gehad tydens die gekombineerde analise. Die PKR-RFLP resultate het 98 % ooreengestem met die van die PVJE. Die resultate van hierdie studie het teenstrydighede tussen die resultate van konvensionele en molekulêre deteksie metodes opgelewer vir die identifikasie van L. monocytogenes. Die spesies-spesifieke en multipleks PKR het egter beide goed te pas gekom vir die akkurate deteksie en identifikasie van L. monocytogenes en kan heel moontlik die gebruik van konvensionele agar tydens identifikasie vervang. Beide PKRRFLP en PVJE was nuttig vir die subtipering van L. monocytogenes isolate. PKR-RFLP is egter ‘n goedkoper tegniek en die resultate is in ‘n korter tydsperiode beskikbaar.

A qualidade e a segurança dos produtos fabricados pelas indústrias de alimentos ficam comprometidas quando bactérias aderem e se multiplicam nas superfícies dos equipamentos utilizados na produção de alimentos. O aço inoxidável AISI (American Iron and Steel Institute) 304 e AISI 316 são os mais utilizados na fabricação de diversos tipos de equipamentos e utensílios para as indústrias de alimentos, sendo que muitos deles contêm soldas entre as junções de suas diferentes partes. Alguns pesquisadores relacionam a presença destas soldas à rugosidade e à dificuldade de higienização e consequente adesão microbiana nestas estruturas. No entanto, atualmente, existem poucos trabalhos que estudam o processo de adesão microbiana em soldas. O presente trabalho teve como objetivo investigar a adesão de um patógeno alimentar Gram-negativo (Salmonella Enteritidis) e um Grampositivo (Listeria monocytogenes) em aços inoxidáveis e em soldas MIG (Metal Inert Gas) e TIG (Tungsten Inert Gas); avaliar a influência da topografia e rugosidade dos materiais e a hidrofobicidade das superfícies e das células no processo de adesão; determinar a energia livre de interação e a energia de adesão entre as células e as superfícies e, por fim; estudar o efeito da modificação da superfície dos aços inoxidáveis através de nitretação a plasma na adesão de S. Enteritidis e L. monocytogenes. Os resultados mostraram que não houve diferença significativa (p > 0,05) entre o número de células aderidas às superfícies dos dois tipos de soldas e dos dois aços inoxidáveis para ambas as bactérias e indicaram que não houve correlação entre a adesão e a hidrofobicidade e a rugosidade das superfícies. O tratamento de nitretação a plasma foi capaz de alterar as superfícies dos aços inoxidáveis, reduzir a adesão bacteriana e, portanto, mostra-se como uma promissora tecnologia para prevenção da adesão microbiana. / The quality and safety of products manufactured by food industry are threatened when bacteria attach to and grow on surfaces of equipment used in food production. The stainless steel AISI (American Iron and Steel Institute) 304 and AISI 316 are the most various types used in the manufacture of equipment and utensils for the food industries. Many of these equipments contain welds between its different parts. Some researchers related the presence of these welds to increase the roughness and the difficulty of cleaning, and consequently microbial adhesion occures in these structures. However, currently, there are few researchers that study the process of microbial adhesion in welds. The present study aimed to investigate the adhesion of a Gram-negative (Salmonella Enteritidis) and Gram-positive (Listeria monocytogenes) food pathogens in stainless steels and MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welds; evaluate the influence of topography and roughness of the materials and the hydrophobicity of the material surfaces and cells in the attachment process and determine the free energy of interaction and adhesion energy between cells and surfaces; and finally, also to evaluate the effect of plasma nitriding surface modification of stainless steels on the adhesion of S. Enteritidis and L. monocytogenes. The results showed that there is no significant difference (p > 0.05) between the numbers of cells attached to the surfaces of welds and stainless steel for both bacteria and indicated that there was no correlation between adhesion and hydrophobicity and roughness of surfaces. The plasma nitriding treatment was able to modify the surfaces of the stainless steel reducing bacterial adhesion and therefore there is demonstrated a promising technology for preventing microbial adhesion.

A host can adopt two strategies when facing infection: resistance, where host immune responses prevent or reduce pathogen replication; or tolerance, which refers to all mechanisms that reduce the impact of the infection on host health or performance. Both strategies may be under host genetic control, and could thus be targeted for genetic improvement. Although there is ample evidence of genetic variation in resistance to infection, there is limited evidence to suggest that individuals also differ genetically in tolerance. Furthermore, although resistance and tolerance are typically considered as alternative host defense mechanisms, relatively little is known about the genetic relationship between them and how they change together over time and jointly determine infection outcome. In this thesis, two datasets from experimental challenge infection experiments were considered for investigating tolerance genetics: Porcine Reproductive & Respiratory Syndrome (PRRS), an endemic viral disease which causes loss of growth and mortality in growing pigs; and Listeria monoctyogenes (Lm), a bacterium which causes food-borne infections in mammals. The two datasets differed substantially in size and genetic structure; the PRRS dataset consists of thousands of records from outbred commercial pig populations, whereas the Listeria dataset comprises much fewer records from genetically diverse highly inbred strains of a mice as a model species. The aims of this thesis were to: 1) Identify if genetic variation in host tolerance to infection exists, with case studies in PRRS and listeria, using conventional reaction-norm methodology; 2) Identify if host tolerance, along with resistance, changes longitudinally as infection progresses; 3) Identify whether the WUR genotype is associated with tolerance slope; 4) Analyse the dynamic relationship between host performance and pathogen load over the time-course of infection by examining the relationship at different stages of infection using GWAS; 5) Develop novel trajectory methodology to offer insight into health-infection dynamics, and identify whether there is genetic variation in trajectories; 6) Develop novel trajectory-derived phenotypes that analyse changes in host performance with respect to changes in pathogen load, as an alternative to tolerance, and identify whether genetic variation exists. This study found that conventional reaction-norm methodology is limited to capture genetic variation in tolerance in outbred populations without measures of performance in the absence of infection. However, by utilising repeated longitudinal data on the same dataset, stages of infection (early, mid and late) were defined for each individual, based on host pathogen load. Using these stages of infection, genetic variation in tolerance was identified over all stages of infection and at mid to late stage of infection. Genetic correlation between resistance and tolerance was strong and positive over all stages of infection, and evidence suggested that resistance and tolerance may be under pleiotropic control. Furthermore, this research found that genetic correlations between resistance and growth changed considerably over time, and that individuals who expressed high genetic resistance early in infection tended to grow slower during that time-period, but were more likely to clear the virus by late stage, and thus recover in growth. However, at mid-late stage of infection, those with high virus load also had high growth, indicating potential epidemiological problems with genetic selection of host resilience to infection. Furthermore, genome wide association studies for pathogen load and growth associated with different stages of infection did not identify novel genetic loci associated with these traits than those previously reported for the whole infection period. By adopting conventional methodology, this study found genetic variation in tolerance of genetically diverse mouse strains to Lm and pigs to PRRS, despite statistical problems. The relationship between resistance and tolerance indicated that both traits should be considered in genetic selection programs. By adopting novel trajectory analysis, this study demonstrated that level of expression of resistance and tolerance changed throughout the experimental infection period and, furthermore, that expression of resistance, followed by tolerance, determined survival of infection. Survivors and non-survivors followed different infection trajectories, which were partially determined by genetics. By deriving novel phenotypes from trajectories that explained changes in growth in relation to change in pathogen load at specific time points, and applying these to the PRRS data, this study did not identify genetic variation in these phenotypes. The genetic signal in these phenotypes may have been masked by the fact that individuals were likely at different stages of infection. In summary, this study has shown that genetic improvement of tolerance, in addition to resistance may be desirable, but could be difficult to achieve in practice due to shortcomings in obtaining accurate and unbiased tolerance estimates based on conventional reaction-norms. Infection trajectories have proven to be a promising tool for achieving an optimally timed balance between resistance and tolerance, but further work is needed to incorporate them in genetic improvement programs.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias. Programa de Pós-graduação em Ciência dos Alimentos / Made available in DSpace on 2012-10-22T16:22:03Z (GMT). No. of bitstreams: 1 244637.pdf: 359506 bytes, checksum: 4ba72fe72924c26efac7bb1b9dac9e33 (MD5) / O baixo risco dos salames em provocarem a listeriose é atribuído aos obstáculos criados durante processo de fabricação e presentes no produto final. O pH e atividade água baixos, alta concentração de sal e a presença de bactérias ácido-lácticas e seus metabólitos secundários compõe barreiras que impedem o desenvolvimento de Listeria monocytogenes. Neste trabalho avaliou-se o comportamento das curvas de sobrevivência deste patógeno durante o processo de fabricação de salames tipo Italiano pouco ácidos (pH final de 5,2) em três formulações: inoculada com Lactobacillus plantarum, com adição de 2% lactato de sódio e uma formulação sem agentes inibidores intencionais. Cada formulação foi contaminada artificialmente com L. monocytogenes e paralelamente acompanhada por uma testemunha de igual composição. O tamanho das populações de L.monocytogenes foi avaliado semanalmente através de contagem pela técnica de tubos múltiplos (NMP), durante o período de fabricação de quatro semanas. Os salames naturalmente contaminados apresentaram discreto aumento da população de L. monocytogenes no inicio do processo, seguidas por redução até o final da maturação e os salames artificialmente contaminados tiveram redução considerável da contagem de L.monocytogenes, principalmente na formulação com adição de L. plantarum, seguido pela formulação com lactato de sódio e por último a formulação padrão, entretanto não se verificou diferença significativa entre os tratamentos. The low risk of salamis in provoking listeriosis is attributed to the obstacles created during production process and presents in the final product. The pH and low water activity, high concentration of salt and the presence of lactic acid bacteria and their secondary metabolites compose barriers that prevent the development of Listeria monocytogenes. In this work the behavior of the survival curves of this pathogen was evaluated during the production process in salamis Italian type slightly acid (final pH of 5,2) in three formulations: inoculated Lactobacillus plantarum, with addition of 2% sodium lactate and a formulation without intentional inhibitors agents. Each formulation was contaminated artificially with L. monocytogenes and parallel accompanied by a witness sample of equal composition. The size of the populations of L.monocytogenes was weekly evaluated through counting by the technique of multiple tubes (NMP), during the period of production of four weeks. The naturally contaminated sausage had presented discreet increase of the population of L. monocytogenes in the beginning of the process, followed by reduction until the end of the maturation and the salamis artificially contaminated had considerable reduction of the counting of L.monocytogenes, mainly in the formulation with addition of L. plantarum, followed by the formulation with sodium lactate and last the standard formulation, however significant difference was not verified among the treatments.

The aim of thesis was to study murine melanoma B16- F10 therapy based on the use of TLR agonists combinedwith activation of phagocytosis. Mechanisms of this therapy were studied on the bases of analysis of tumor infiltrating immune cells and evaluationof thein effect on tumor cells.

A exportação de carne bovina possui lugar de destaque na economia brasileira, e, com o intuito de aumentar a disputa por novos mercados, tem-se buscado a produção de alimentos de qualidade e seguros. Dentro dessa concepção, a presença de Listeria monocytogenes constitui uma preocupação, devido à gravidade das infecções, veiculadas por alimentos, em humanos. O objetivo deste estudo foi avaliar a presença de Listeria sp. e microrganismos mesófilos totais em carcaças bovinas, em três pontos da linha de abate, verificando os perfis de resistência aos antimicrobianos das Listeria monocytogenes isoladas. Também objetivou-se avaliar a presença de Listeria sp. no ambiente de produção onde as carcaças foram processadas. Para tanto, suabes de superfície foram utilizados para coletar as amostras no ambiente de produção e nas carcaças bovinas, sendo as amostras ambientais inoculadas em placas Petrifilm para Listeria e as amostras de carcaça avaliadas segundo métodos preconizados pela norma ISO 11290. Das 110 carcaças analisadas, 12 foram positivas para Listeria sp., as quais: 7 L. innocua , 4 L. monocytogenes ,uma Listeria sp.Todas essas amostras foram isoladas do ponto 1, onde os animais ainda estavam com couro. Das 200 amostras ambientais, 25 foram positivas para Listeria sp, sendo uma L. monocytogenes e 24 L. innocua. Os isolados de L. monocytogenes foram susceptíveis a todos os antimicrobianos testados. As contagens médias de microrganismos mesófilos totais foram de 6,3 x 102; 4,9 x102 e 3,8 x102 UFC/100cm2 nos pontos 1, 2 e 3, respectivamente. Observou-se que no dia em que as contagens totais foram mais elevadas nas carcaças, houve maior número de isolamentos de L. innocua no ambiente, sugerindo contaminação cruzada. / The beff export ocupies a prominent place in the Brazilian economy, and, with the aim of increasing competition for new markets, have sought the production of quality food and insurance. Within this concept, the presence of Listeria monocytogenes , the product is a concern, mainly due to the severity of infections transmitted by food in humans. The objective of this study was to evaluate the presence of Listeria sp. And mesophilic microrganism in carcasses of cattle in three points of the slaughter line, checking the profiles of antimicrobial resistance of Listeria monocytogenes isolated. It also aimed to assess the presence of Listeria sp. in the production abbatoir environment industrial. For both, surfaces swabs were used to collect samples in the production environmental cattle carcass, environmental samples were inoculated in Petri film’s plate for Listeria and the samples carcass was evaluated according to the methods suggested by ISO 11290. Of the 110 carcasses, 12 were positives for Listeria spp., which were identified as L. innocua (7), L. monocytogenes (4), Listeria sp. (1). All samples were isolated from a point where the animals were still with leather. Of the 200 environmental samples, 25 were positive for Listeria sp, being one L. monocytogenes and 24 L. innocua. Isolates of L. monocytogenes were susceptible to all antimicrobials. The average counts of mesophilic microrganism were 6,3 x 102; 4,9 x102 e 3,8 x102UFC/100cm2 in the points 1, 2 e 3, respectively. We could see that on the total counts were higher in the carcasses higher number of L. innocua in the environment, suggesting the possibility of cross contamination.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-06-09T12:12:00Z No. of bitstreams: 1 texto completo.pdf: 1065748 bytes, checksum: ee65362a434059bf4cf0d2d814237c1e (MD5) / Made available in DSpace on 2017-06-09T12:12:00Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1065748 bytes, checksum: ee65362a434059bf4cf0d2d814237c1e (MD5) Previous issue date: 2017-02-13 / A Listeria monocytogenes é um micro-organismo patogênico amplamente distribuído na natureza, isolado de diferentes ambientes, e de uma ampla variedade de alimentos, que são consumidos in natura. É uma bactéria de alta importância na indústria de alimentos, uma vez que sobrevive e se multiplica em diferentes condições ambientais, características que lhe permitem superar barreiras impostas durante o processamento de alimentos. Esta bactéria veiculada por alimentos tem sido relacionada a surtos de listerioses, que afeta grupos de maior suscetibilidade e provoca maiores taxas de hospitalização e de mortalidade que outros micro-organismos. Desse modo, a L. monocytogenes tem sido reconhecida como um micro-organismo de importância, tanto para as autoridades de saúde pública, como para a indústria de alimentos (CDC, 2013). Na última década, L. monocytogenes tem sido responsabilizada por um amplo número de surtos e casos esporádicos, de extensão variada e vinculados com diversos tipos de alimentos (BUCHANAN et al., 2017), entre os quais se destacam os relacionados com melão, ocorridos nos Estados Unidos (2011), Austrália e Canadá (JUNG et al., 2016). O objetivo principal desta pesquisa foi estudar a ocorrência da contaminação cruzada por L. monocytogenes e L. fleischmannii subsp. coloradonensis em melão durante a etapa de sanitização sob diferentes condições experimentais, assim como, determinar o efeito da temperatura de estocagem (5 e 12 °C) na capacidade de multiplicação desses dois micro-organismos, após da ocorrência da contaminação cruzada, corte e embalagem do melão. Para o estudo da contaminação cruzada, as amostras foram inoculadas por imersão com cada um dos micro-organismos estudados separadamente, e incubadas até atingir uma concentração entre 10^6 e 10^8 log (UFC.ml^-1). Após ser realizada a simulação dos dois processos de contaminação cruzada, foi avaliada a transferência bacteriana para a superfície dos melões não contaminados e para as águas de sanitização e de enxague, e a permanência dos micro-organismos na superfície dos melões contaminados. A recuperação dos micro-organismos da superfície dos melões não contaminados demonstrou que apesar destes apresentarem reduções nas populações independentemente avaliadas, do a processo transferência de bacteriana contaminação ocorreu simulado e da concentração da solução sanitizante empregada, obtendo-se resultados para L. monocytogenes entre 2,9 e 7,5 log (UFC/fruta) e para L. fleischmannii subsp. coloradonensis entre 4,0 e 7,3 log (UFC/fruta) sem apresentar diferenças significativas entre os micro-organismos avaliados (p>0,05). A quantificação da permanência bacteriana nos melões contaminados para L. monocytogenes foi de 4,9 a 7,4 log (UFC/fruta). Enquanto a L. fleischmannii subsp. coloradonensis foram de 6,6 a 7,5 log (UFC/fruta), apresentando diferenças significativas entre os micro-organismos avaliados (p<0,05). A respeito da transferência dos micro-organismos para as águas de sanitização e as águas de enxague, se evidenciou que independentemente das condições experimentais avaliadas, as transferências obtidas para as águas de enxague foram maiores em comparação às obtidas para as águas de sanitização. O efeito da temperatura de estocagem na capacidade de multiplicação dos micro-organismos estudados, demonstrou que L. monocytogenes tem a capacidade de sobreviver e multiplicar-se na polpa do melão nas temperaturas de refrigeração estudadas. Enquanto que para L. fleischmannii subsp. coloradonensis se determinou que tem a capacidade de sobreviver a ambas temperaturas, mas só pode se multiplicar a 12°C de refrigeração. Os resultados obtidos durante o desenvolvimento desta pesquisa, permitem determinar que o controle eficaz da contaminação durante as diferentes etapas da cadeia produtiva, é muito importante, já que ao se implementar métodos eficientes de sanitização e apropriadas técnicas de manuseio e preparação do alimento, é possível evitar a ocorrência de episódios de contaminação cruzada, que provavelmente ocasionaram surtos de doenças veiculadas por alimentos, representando risco à saúde do consumidor. / Listeria monocytogenes is a pathogenic microorganism widely distributed in nature, isolated from different environments, as well as from a wide variety of foods that are consumed in nature. Is a bacterium of high relevance in the food industry, as it survives and multiplies in different environmental conditions, characteristics that allow it to overcome the barriers imposed during food processing. This bacterium conveyed by food has been linked to outbreaks of listeriosis, which affects groups of grater susceptibility and causes higher rates of hospitalizations and mortality than other microorganisms. Thus, L. monocytogenes has been recognized as a relevant microorganism by public health authorities and the food industry (CDC, 2013). During the last decade, L. monocytogenes has been responsible for a large number of outbreaks and sporadic cases, of varied extent and related to several types of food (BUCHANAN et al., 2017), among which are those related to melon, reported in the United States (2011), Australia and Canada (JUNG et al., 2016). The main purpose of this research was to investigate the cross-contamination occurrence by L. monocytogenes and L. fleischmannii subsp. coloradonensis in melon during sanitization under different experimental conditions; also the research intended to determine the effect of storage temperature (5 and 12° C) on the multiplication capacity of these two microorganisms, after the occurrence of melon cross-contamination, slicing and packaging. For the cross-contamination study, the samples were inoculated by immersion with each of the microorganisms studied separately, and incubated until reaching a concentration between 10^6 and 10^8 (CFU.ml^-1). After the simulation of the two cross-contamination processes, it was evaluated the bacterial transfer to the surface of uncontaminated melons and to the sanitizing and rinsing waters, and the microorganisms permanence on the surface of contaminated melons. The recovery of surface microorganisms from uncontaminated melons demonstrated that even though they present reductions in the evaluated populations, the bacterial transfer occurred, independently of the simulated contamination process and the concentration of sanitizing solution employed, obtaining results for L. monocytogenes between 2,9 and 7,5 log (CFU/fruit) and for L. fleischmannii subsp. coloradonensis between 4,0 and 7,3 log (CFU/fruit) without presenting significant differences between the evaluated microorganisms (p>0.05). The bacterial permanence quantification in contaminated melons for L. monocytogenes was 4,9 to 7,4 log (CFU/fruit). While L. fleischmannii subsp. coloradonensis were 6,6 and 7,5 log (CFU/fruit), presenting significant differences among the evaluated microorganisms (p<0.05). Regarding the transfer of microorganisms to sanitizing and rinsing water, it was evident that, independently of the experimental conditions evaluated, the transfers obtained for rinsing waters were higher comparing to those obtained for sanitizing waters. The effect of storage temperature in the multiplication capacity of the studied microorganisms demonstrated that L. monocytogenes has the ability to survive and multiply in the melon pulp at the cooling temperatures studied. As for L. fleischmannii subsp. coloradonensis, it has been determined that it has the ability to survive both temperatures but is only able to multiply at 12°C cooling. The outcomes obtained during this research, allow to determine the relevance of effective contamination control during the different stages of the productive chain, as implementing efficient sanitization methods and appropriate of food handling and preparation techniques, it is possible to avoid the occurrence of cross-contamination episodes which are likely to cause outbreaks of food-borne diseases, thus representing posing a risk to consumer health.

Made available in DSpace on 2016-05-11T12:48:49Z (GMT). No. of bitstreams: 2 119.pdf: 1745768 bytes, checksum: 9bfd9cd691a8e94e12ca96a48d45f683 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Fundação Oswaldo Cruz. Instituto Nacional de Controle de Qualidade em Saúde / Das espécies existentes de Listeria, a Listeria monocytogenes é considerada patogênica e está envolvida em casos de listeriose. O sorotipo 4b é mais comum entre cepas responsáveis por surtos e casos esporádicos de doença. Há dois tipos de listeriose: a invasiva que pode até afetar o SNC (SistemaNervoso Central) e, a não-invasiva. Existem vários registros da presença desse patógeno em leite e derivados como o queijo, assim como diversos surtos de doenças graves associadas à ingestão desses alimentos contaminados. A infecção patogênica por L. monocytogenes pode afetar indivíduos sadios, eprincipalmente aqueles pré-dispostos através de doenças que afetam o sistemaimunológico, como câncer ou AIDS, e também outros indivíduos susceptíveis como idosos, mulheres grávidas, recém-nascidos ou fetos. Na maioria dos casos os sintomas são diarréia, febre, dor de cabeça e mialgia, e em alguns casos gastroenterite. De acordo com a Resolução -RDC n. 12, de 02/01/2001,do Ministério da Saúde, foi estabelecida ausência de L. monocytogenes em 259 de amostra de queijo minas frescal. O objetivo principal deste trabalho foifazer o isolamento de L. monocytogenes em amostras de queijo tipo minas frescal, utilizando a caracterização fenotípica baseada na IS011290-1 e a caracterização molecular através da Multiplex-PCR otimizada por Doumith et al(2004). Foram utilizados os meios Oxford, Palcam e Cromogênico para cultura,e 5 pares de primers específicos para Multiplex-PCR. Das 30 amostras analisadas, 14 amostras (47 por cento) apresentaram Listeria spp. e 5 (17 por cento)apresentaram L. monocytogenes, que pertence ao grupo dos sorovares 1/2b,3b, 4b, 4d e 4e, sendo provavelmente o sorovar 112b elou 3b o encontrado nasamostras analisadas. Tanto a caracterização fenotípica como a caracterização molecular foram eficazes na identificação de L. monocytogenes, porém a primeira metodologia requer mais tempo para obtenção de resultados conclusivos