Navegando por Autor "Vanetti, Maria Cristina Dantas"
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Item Acid and low temperature treatments on Salmonella Enteritidis inoculated in pork and its subsequent survival in simulated gastric fluid(Ciência Rural, 2016-03) Santos, Míriam Teresinha dos; Paes, Simone Albino; Vanetti, Maria Cristina Dantas; Silva, Simone QuintaoThe objective of this study was to evaluate the acid resistance of Salmonella enterica serovar Enteritidis (S. Enteritidis) in stored pork and in simulated gastric fluid (SGF). A culture of S. Enteritidis was subjected to acid treatment prior to inoculation into pork, stored under refrigeration at frozen temperatures and exposed to SGF. The S. Enteritidis CCS3 and ATCC 13076 strains previously subjected to acid treatment (at pH 4.0-5.0) were inoculated in pork and stored at 4[degrees]C and -18[degrees]C. Storage at 40C did not affect the populations of both S. Enteritidis strains. After 84 days at -18[degrees]C, the mean population of both CCS3 and ATCC strains were reduced by 0.8 and 1.5 log cycles, respectively. Prior acid treatment did not enhance the survival of both strains at low temperatures. After acid treatment and low temperature storage, S. Enteritidis ATCC 13076 lost culturability after being exposed to SGF for 10 minutes. In contrast, S. Enteritidis CCS3 was tolerant until three hours of SGF exposure. S. Enteritidis CCS3 submitted to pH 4.0 was more tolerant to SGF exposure than when submitted to pH 4.5, 5.0 and without acid treatment. Therefore, this study indicates that exposure to an acidic and cold environment during processing enhanced the ability of S. Enteritidis to survive in the gastric environment of the human stomach, possibly increasing the risk of a Salmonella infection after consumption of pork.Item Acyl homoserine lactone changes the abundance of proteins and the levels of organic acids associated with stationary phase in Salmonella Enteritidis(Microbial Pathogenesis, 2016-12-01) Almeida, Felipe Alvesde; Pimentel-Filho, Natan de Jesus; Carrijo, Lanna Clícia; Bento, Claudia Braga Pereira; Baracat-Pereira, Maria Cristina; Pinto, Uelinton Manoel; Oliveira, Leandro Licursi de; Vanetti, Maria Cristina DantasQuorum sensing (QS) is cell-cell communication mechanism mediated by signaling molecules known as autoinducers (AIs) that lead to differential gene expression. Salmonella is unable to synthesize the AI-1 acyl homoserine lactone (AHL), but is able to recognize AHLs produced by other microorganisms through SdiA protein. Our study aimed to evaluate the influence of AI-1 on the abundance of proteins and the levels of organic acids of Salmonella Enteritidis. The presence of N-dodecyl-homoserine lactone (C12-HSL) did not interfere on the growth or the total amount of extracted proteins of Salmonella. However, the abundance of the proteins PheT, HtpG, PtsI, Adi, TalB, PmgI (or GpmI), Eno, and PykF enhanced while the abundance of the proteins RplB, RplE, RpsB, Tsf, OmpA, OmpC, OmpD, and GapA decreased when Salmonella Enteritidis was anaerobically cultivated in the presence of C12-HSL. Additionally, the bacterium produced less succinic, lactic, and acetic acids in the presence of C12-HSL. However, the concentration of extracellular formic acid reached 20.46 mM after 24 h and was not detected when the growth was in the absence of AI-1. Considering the cultivation period for protein extraction, their abundance, process and function, as well as the levels of organic acids, we observed in cells cultivated in presence of C12-HSL a correlation with what is described in the literature as entry into the stationary phase of growth, mainly related to nitrogen and amino acid starvation and acid stress. Further studies are needed in order to determine the specific role of the differentially abundant proteins and extracellular organic acids secreted by Salmonella in the presence of quorum sensing signaling molecules.Item Acyl homoserine lactone-based quorum sensing stimulates biofilm formation by Salmonella Enteritidis in anaerobic conditions(Archives of Microbiology, 2016-11-12) Almeida, Felipe Alves de; Pimentel-Filho, Natan de Jesus; Pinto, Uelinton Manoel; Mantovani, Hilário Cuquetto; Oliveira, Leandro Licursi de; Vanetti, Maria Cristina DantasQuorum sensing regulates a variety of phenotypes in bacteria including the production of virulence factors. Salmonella spp. have quorum sensing systems mediated by three autoinducers (AI-1, AI-2, and AI-3). The AI-1-mediated system is incomplete in that the bacterium relies on the synthesis of signaling molecules by other microorganisms. This study aimed to evaluate the influence of the AI-1 N-dodecanoyl-DL-homoserine lactone (C12-HSL) on the growth, motility, adhesion, and biofilm formation of Salmonella enterica serovar Enteritidis PT4 578 on a polystyrene surface. Experiments were conducted at 37 °C in anaerobic tryptone soy broth supplemented with C12-HSL and/or a mixture of four synthetic furanones, at the concentration of 50 nM each. The planktonic growth, adhesion, swarming, and twitching motility were not altered in the presence of C12-HSL and/or furanones under anaerobic conditions. However, C12-HSL induced biofilm formation after 36 h of cultivation as determined by quantification of biofilm formation, by enumeration of adhered cells to polystyrene coupons, and finally by imaging the presence of multilayered cells on an epifluorescence microscope. When furanones were present in the medium, an antagonistic effect against C12-HSL on the biofilm development was observed. The results demonstrate an induction of biofilm formation in Salmonella Enteritidis by AI-1 under anaerobic conditions. Considering that Salmonella does not produce AI-1 but respond to it, C12-HSL synthesized by other bacterial species could trigger biofilm formation by this pathogen in conditions that are relevant for its pathogenesis.Item Análise e monitoramento de pontos críticos no abate de frangos utilizando indicadores microbiológicos(Ciência Rural, 2008-10) Pinto, Paulo Sérgio de Arruda; Vanetti, Maria Cristina Dantas; Bevilacqua, Paula Dias; Nero, Luís Augusto; Pinto, Mayara Souza; Rodrigues, Augusto César AlmeidaA presença de microrganismos indicadores de contaminação na linha de abate de frangos foi determinada visando identificar os possíveis pontos de controle e oferecer uma opção para o monitoramento ou a verificação pelo sistema “Análise de Perigos e Pontos Críticos de Controle” (APPCC). A contaminação superficial das carcaças foi determinada pela enumeração de microrganismos aeróbios mesófilos, coliformes totais, coliformes termotolerantes e de Escherichia coli nas seguintes fases de abate: A - antes do primeiro chuveiro de higienização, B - após o primeiro chuveiro, C - após a evisceração manual, D - após o chuveiro de lavagem final e E - na saída do pré-resfriamento. Não houve diferença significativa (P<0,05) entre as médias de mesófilos, coliformes totais e termotolerantes, entre as fases A, B, C e D. Entretanto, as médias obtidas para esses microrganismos indicadores na fase E (pré-resfriamento) foram significativamente menores. Não houve diferença significativa entre as médias de Escherichia coli nas cinco fases. As chances de contaminação (Razão de Chances) por mesófilos foram maiores na fase A e por coliformes na fase C. Entre os parâmetros analisados, os níveis de contaminação por mesófilos, coliformes totais e termotolerantes foram os mais indicados para monitoramento e verificação de um plano APPCC no abate de aves. Os resultados obtidos indicaram que a fase de pré-resfriamento pode ser considerada um importante ponto crítico de controle, uma vez que foi capaz de reduzir a contaminação microbiológica de forma significativa.Item Antimicrobial activity and mineral composition of shiitake mushrooms cultivated on agricultural waste(Brazilian Archives of Biology and Technology, 2011-09) Kasuya, Maria Catarina Megumi; Casaril, Kérley Braga Pereira Bento; Vanetti, Maria Cristina DantasThe antimicrobial activity and mineral composition of shiitake mushrooms were evaluated in four isolates of Lentinula edodes. Mushrooms were cultivated on artificial logs, based on eucalyptus sawdust enriched with 20% rice, wheat, or soybean bran, or combination of 10% of two of these supplements. The substrates were humidified with a 0.1% mate tea extract or water. Logs of Eucalyptus grandis were also used to cultivate the shiitake mushrooms. The antimicrobial activity of an aqueous extract, corresponding to 40 mg of mushroom dry matter, was in some cases, depending on the isolate, able to inhibit both Bacillus subtilis and Escherichia coli K-12, independent of substrate composition or the growth stage of the mushrooms. Nitrogen, phosphorus, potassium, magnesium and calcium concentrations varied according to the substrate on which the mushrooms were cultivated, being, generally, higher with cultivation on artificial rather than natural eucalyptus logs. It could be concluded that, in addition to the fungal isolate, substrate composition and, processing methods must be considered during the production of antimicrobial substance(s) as well as in the mushroom nutritional compositionItem Biocontrole de Listeria monocytogenes por Pediococcus acidilactici em couve minimamente processada(Food Science and Technology, 2009-10) Costa, Wanessa Altimiras; Vanetti, Maria Cristina Dantas; Puschamann, RolfEste estudo avaliou um sistema de biocontrole para inibição de Listeria monocytogenes em couve minimamente processada, objetivando sua segurança durante estocagem sob refrigeração e em condições de abuso de temperatura. O potencial inibitório de bactérias láticas tolerantes ao sal e psicrotróficas contaminantes naturais da couve e Lactobacillus plantarum, Lactobacillus delbrueckii ATCC 9649 e Lactobacillus casei CCT 1465 foram avaliadas contra L. monocytogenes. O isolado de couve identificado como P. acidilactici CCA3 inibiu L. monocytogenes a 10 e 15 °C em ágar MRS e foi selecionado como possível agente de biocontrole. O número de L. monocytogenes na couve minimamente processada aumentou 3,7 e 4,7 ciclos logarítmicos a 5 e 10 °C, respectivamente, após 20 dias de armazenamento e 4,6 ciclos logarítmicos após oito dias a 15 °C. Entretanto, quando 108 UFC.g-1 de P. acidilactici CCA3 foram inoculados no produto processado, o crescimento de L. monocytogenes reduziu 2,3 ciclos logarítmicos sob temperatura abusiva de 15 °C. A acidez titulável e as características sensoriais da couve não foram alteradas pela presença de CCA3 ao longo do período de vida útil. Estes resultados sugerem o potencial de aplicação dos bioconservantes na couve minimamente processada, que necessitam estar associados à refrigeração e sanitização para garantir segurança.Item The biodiversity of the microbiota producing heat-resistant enzymes responsible for spoilage in processed bovine Milk and dairy products(Frontiers in Microbiology, 2017-03-01) Machado, Solimar Gonçalves; Baglinière, François; Marchand, Sophie; Coillie, Els Van; Vanetti, Maria Cristina Dantas; Block, Jan De; Heyndrickx, MarcRaw bovine milk is highly nutritious as well as pH-neutral, providing the ideal conditions for microbial growth. The microbiota of raw milk is diverse and originates from several sources of contamination including the external udder surface, milking equipment, air, water, feed, grass, feces, and soil. Many bacterial and fungal species can be found in raw milk. The autochthonous microbiota of raw milk immediately after milking generally comprises lactic acid bacteria such as Lactococcus, Lactobacillus, Streptococcus, and Leuconostoc species, which are technologically important for the dairy industry, although they do occasionally cause spoilage of dairy products. Differences in milking practices and storage conditions on each continent, country and region result in variable microbial population structures in raw milk. Raw milk is usually stored at cold temperatures, e.g., about 4°C before processing to reduce the growth of most bacteria. However, psychrotrophic bacteria can proliferate and contribute to spoilage of ultra-high temperature (UHT) treated and sterilized milk and other dairy products with a long shelf life due to their ability to produce extracellular heat resistant enzymes such as peptidases and lipases. Worldwide, species of Pseudomonas, with the ability to produce these spoilage enzymes, are the most common contaminants isolated from cold raw milk although other genera such as Serratia are also reported as important milk spoilers, while for others more research is needed on the heat resistance of the spoilage enzymes produced. The residual activity of extracellular enzymes after high heat treatment may lead to technological problems (off flavors, physico-chemical instability) during the shelf life of milk and dairy products. This review covers the contamination patterns of cold raw milk in several parts of the world, the growth potential of psychrotrophic bacteria, their ability to produce extracellular heat-resistant enzymes and the consequences for dairy products with a long shelf life. This problem is of increasing importance because of the large worldwide trade in fluid milk and milk powder.Item Bovicin HC5 and nisin reduce Staphylococcus aureus adhesion to polystyrene and change the hydrophobicity profile and Gibbs free energy of adhesion(International Journal of Food Microbiology, 2014-11-03) Pimentel-Filho, Natan de Jesus; Martins, Mayra Carla de Freitas; Nogueira, Guilherme Bicalho; Mantovani, Hilário Cuquetto; Vanetti, Maria Cristina DantasStaphylococcus aureus is an opportunistic pathogen often multidrug-resistant that not only causes a variety of human diseases, but also is able to survive on biotic and abiotic surfaces through biofilm communities. The best way to inhibit biofilm establishment is to prevent cell adhesion. In the present study, subinhibitory concentrations of the bacteriocins bovicin HC5 and nisin were tested for their capability to interfere with the adhesion of S. aureus to polystyrene. Subinhibitory dosages of the bacteriocins reduced cell adhesion and this occurred probably due to changes in the hydrophobicity of the bacterial cell and polystyrene surfaces. After treatment with bovicin HC5 and nisin, the surfaces became more hydrophilic and the free energy of adhesion (∆Gadhesion) between bacteria and the polystyrene surface was unfavorable. The transcriptional level of selected genes was assessed by RT-qPCR approach, revealing that the bacteriocins affected the expression of some important biofilm associated genes (icaD, fnbA, and clfB) and rnaIII, which is involved in the quorum sensing mechanism. The conditioning of food-contact surfaces with bacteriocins can be an innovative and powerful strategy to prevent biofilms in the food industry. The results are relevant for food safety as they indicate that bovicin HC5 and nisin can inhibit bacterial adhesion and consequent biofilm establishment, since cell adhesion precedes biofilm formation.Item Características físico-químicas e microbiológicas de morango minimamente processado(Food Science and Technology, 2010-01) Ponce, Adriana dos Reis; Bastiani, Maria Inês Dantas; Minim, Valéria Paula; Vanetti, Maria Cristina DantasO presente trabalho teve como objetivo avaliar as alterações físico-químicas e microbiológicas de morangos submetidos ao processamento mínimo. Foram avaliados os efeitos da lavagem com cloreto de cálcio ou polietilenoglicol na microbiota contaminante e na textura dos morangos e da sanificação com ozônio gasoso ou clorado orgânico. Análises de textura, cor, perda de massa e microbiota contaminante foram feitas durante o armazenamento a 5 °C por 12 dias em embalagens envoltas com uma a quatro camadas de filme de cloreto de polivinil (PVC). A adição de até 1,5% de cloreto de cálcio ou de 0,5% de polietilenoglicol na água de lavagem não garantiu a manutenção da textura do morango ao final do período de armazenamento. A ozonização dos morangos por 60 minutos foi mais efetiva para reduzir (p < 0,05) a contagem de mesófilos aeróbios, fungos e leveduras e coliformes do que a ozonização por 30 minutos ou a imersão em solução de clorado orgânico. Os morangos armazenados em embalagens recobertas com três camadas de filme PVC apresentaram aumento na textura e na intensidade de escurecimento e redução na microbiota contaminante. Os principais fungos isolados de morangos minimamente processados durante o armazenamento pertenciam ao gênero Fusarium e à espécie Cladosporium cladosporioides.Item Changes in the Salmonella enterica Enteritidis phenotypes in presence of acyl homoserine lactone quorum sensing signals(Journal of Basic Microbiology, 2015-11-11) Campos‐Galvão, Maria Emilene Martino; Ribon, Andrea Oliveira Barros; Araújo, Elza Fernandes; Vanetti, Maria Cristina DantasQuorum sensing is used by bacteria to coordinate gene expression in response to population density and involves the production, detection and response to extracellular signaling molecules known as autoinducers (AIs). Salmonella does not synthesize the AI-1, acyl homoserine lactone (AHL) common to gram-negative bacteria; however, it has a receptor for AI-1, the SdiA protein. The effect of SdiA in modulating phenotypes of Salmonella has not been elucidated. In this report, we provide evidence that the AIs-1 affect Salmonella enterica serovar Enteritidis behavior by enhancing the biofilm formation and expression of virulence genes under anaerobic conditions. Biofilm formation by Salmonella was detected by the crystal violet method and by scanning electron microscopy. The presence of AHLs, particularly C12-HSL, increased biofilm formation and promoted expression of biofilm formation genes (lpfA, fimF, fliF, glgC) and virulence genes (hilA, invA, invF). Our results demonstrated that AHLs produced by other organisms played an important role in virulence phenotypes of Salmonella Enteritidis.Item Detecção de Listeria, Salmonella e Klebsiella em serviço de alimentação hospitalar(Revista de Nutrição, 2004-07) Pinto, Uelinton Manoel; Cardoso, Rodrigo Rezende; Vanetti, Maria Cristina DantasA presença de Listeria monocytogenes, Salmonella sp. e Klebsiella sp. em dietas enterais e em ambientes, utensílios e equipamentos de preparo de alimentos em serviço de alimentação hospitalar, foi o objetivo desta pesquisa. A contaminação de ambientes, utensílios e equipamentos de preparo de alimentos em serviço de alimentação hospitalar por Listeria monocytogenes, Salmonella sp. e Klebsiella sp. foi avaliada em 50 amostras coletadas pela técnica de swab. Quatro amostras de dietas enterais também foram analisadas. Colônias típicas de bactérias do gênero Listeria foram isoladas de dieta enteral em ágar Oxford e a identificação da espécie L. monocytogenes foi feita por testes bioquímicos e imunológicos. A presença de Salmonella foi detectada em dieta enteral e identificada como S. rissen por sorologia. Pela relevância como agente causador de infecções hospitalares, bactérias do gênero Klebsiella foram pesquisadas e isoladas em ágar seletivo MacConkey-inositol-carbenicilina. K. pneumoniae foi encontrada em equipamento e utensílio e K. oxytoca em ambiente, equipamento e dieta enteral. Os isolados de L. monocytogenesapresentaram resistência apenas ao antibiótico cefoxitina e os do gênero Klebsiella foram resistentes a ampicilina e amoxilina. S. rissen foi sensível aos 13 antibióticos avaliados. A contaminação de 11% das amostras analisadas com pelo menos um dos patógenos, alerta para a necessidade de implantação de um rigoroso sistema de controle de qualidade nas áreas de manipulação dos alimentos, a fim de aumentar a segurança alimentar dos pacientes hospitalizados.Item Effect of eugenol on growth and listeriolysin O production by Listeria monocytogenes(Brazilian Archives of Biology and Technology, 2006-05) Filgueiras, Cristina Tostes; Vanetti, Maria Cristina DantasThe inhibitory effect of eugenol, a naturally occurring compound mainly present in the essential oil fraction of cloves, was studied on the growth and listeriolysin O (LLO) production by Listeria monocytogenes. Potassium efflux from cells promoted by eugenol was also determined after 24 h incubation in phosphate buffered saline. Eugenol promoted a delay on the growth of L. monocytogenes at concentrations of 100, 300 and 500 μ g mL -1 and above 800 μ g mL -1 the effect was bactericidal. Production of LLO by L. monocytogenes in the presence of eugenol was reduced 80-100%. An accumulation of external K + was observed above 300 μ g mL -1 of eugenol which indicated that the cell membrane was affected. The results showed the effectiveness of eugenol in controlling growth and LLO production of L. monocytogenes cells.Item Endophytic bacteria isolated from common bean (Phaseolus vulgaris) exhibiting high variability showed antimicrobial activity and quorum sensing inhibition(Current Microbiology, 2015-07-23) Lopes, Ralf Bruno Moura; Vanetti, Maria Cristina Dantas; Araújo, Elza Fernandes de; Queiroz, Marisa Vieira de; Costa, Leonardo Emanuel de OliveiraEndophytic bacteria play a key role in the biocontrol of phytopathogenic microorganisms. In this study, genotypic diversity was analyzed via repetitive element PCR (rep-PCR) of endophytic isolates of the phylum Actinobacteria that were previously collected from leaves of cultivars of common bean (Phaseolus vulgaris). Considerable variability was observed, which has not been reported previously for this phylum of endophytic bacteria of the common bean. Furthermore, the ethanol extracts from cultures of various isolates inhibited the growth of pathogenic bacteria in vitro, especially Gram-positive pathogens. Extracts from cultures of Microbacterium testaceum BAC1065 and BAC1093, which were both isolated from the ‘Talismã’ cultivar, strongly inhibited most of the pathogenic bacteria tested. Bean endophytic bacteria were also demonstrated to have the potential to inhibit the quorum sensing of Gram-negative bacteria. This mechanism may regulate the production of virulence factors in pathogens. The ability to inhibit quorum sensing has also not been reported previously for endophytic microorganisms of P. vulgaris. Furthermore, M. testaceum with capacity to inhibit quorum sensing appears to be widespread in common bean. The genomic profiles of M. testaceum were also analyzed via pulsed-field gel electrophoresis, and greater differentiation was observed using this method than rep-PCR; in general, no groups were formed based on the cultivar of origin. This study showed for the first time that endophytic bacteria from common bean plants exhibit high variability and may be useful for the development of strategies for the biological control of diseases in this important legume plant.Item Enrichment of mushrooms: an interesting strategy for the acquisition of lithium(PubMed, 2012-03-19) Assunção, Laélia Soares de; Luz, José Maria Rodrigues da; Silva, Marliane de Cássia Soares da; Vieira, Patrícia Aparecida Fontes; Bazzolli, Denise Mara Soares; Vanetti, Maria Cristina Dantas; Kasuya, Maria Catarina MegumiThe capability of Pleurotus ostreatus mushroom to accumulate lithium (Li) and the accessibility of this Li compared with lithium carbonate (Li2CO3), often used as psychiatric medicine, were investigated. Mushrooms were produced on a substrate-based on coffee husk, with different added concentrations of lithium chloride (LiCl). Biological efficiency (BE), the crude protein content, the concentration of Li and other elements present in mushrooms were determined. The sequential extraction and in vitro test were used to verify the accessibility and the degree of solubility of this element. Li concentration in mushrooms was directly influenced by increasing LiCl concentration in the substrate (P < 0.05). The BE was not affected by different concentrations of LiCl. Li present in enriched mushrooms showed greater accessibility than in Li2CO3. Therefore, P. ostreatus mushrooms, enriched with lithium can be an alternative source of Li, as well as being a food with high nutritional value.Item Estudo da atividade antibacteriana de plantas medicinais, aromáticas e corantes naturais(Revista Brasileira de Farmacognosia, 1998) Bara, Maria Teresa Freitas; Vanetti, Maria Cristina DantasO emprego de recursos naturais como mecanismo auxiliar no tratamento de distintas patologias tem ressurgido, com ênfase, nos útimos tempos. Tendo em vista esta situação, este estudo teve por finalidade investigar a atividade antimicrobiana de algumas plantas medicinais e aromáticas bastantes comuns na cultura brasileira. Foi constatado que, de modo particular, o alecrim-pimenta (Lippia sidoides) levou a uma considerável inibição do crescimento bacteriano. Tambêm plantas como alecrim (Rosmarinus officinalis), cravo (Sysygium aromaticum), noz-moscada (Myristica fragrans), pimenta-da-jamaica (Pimenta dioica) e sálvia (Salvia officinalis) demonstraram constituir fontes eficientes de compostos bioativos antibacterianos.Item Identificação de bactérias psicrotróficas proteolíticas isoladas de leite cru refrigerado e caracterização do seu potencial deteriorador(Revista do Instituto Laticínios Cândido Tostes, 2015-05-25) Machado, Solimar Gonçalves; Pinto, Cláudia Lúcia de Oliveira; Martins, Maurilio Lopes; Vanetti, Maria Cristina DantasOs objetivos deste estudo foram identificar bactérias psicrotróficas proteolíticas isoladas de leite cru refrigerado, avaliar o seu poder deteriorador e a sua capacidade de adesão em superfícies de aço inoxidável sob temperaturas de refrigeração. Dentre as bactérias gram-positivas, 23,81% e 33,33% dos isolados pertenciam aos gêneros Bacillus e Paenibacillus respectivamente. No grupo de bactérias gram-negativas fermentadoras de glicose foram identificados os gêneros Cedecea, Enterobacter, Hafnia, Klebsiella, Pantoea, Providencia, Rhanella e Serratia e dentre as bactérias gram-negativas não-fermentadoras, os gêneros Acinetobacter,Aeromonas, Burkholderia, Chryseobacteriun (Flavobacterium), Chryseomonas, Moraxella e Pseudomonas. O gênero Pseudomonas foi predominante entre as bactérias identificadas e representou 33,98% do total de isolados. Dentre as bactérias fermentadoras de glicose 14,6%, 15,3% e 20,8% dos isolados apresentaram predominantemente atividade proteolítica a 6,5 ºC, 21 ºC e 35 ºC, respectivamente, enquanto as bactérias gram-negativas não-fermentadoras apresentaram 25% e 23,6% dos isolados com atividades associadas de proteases, lipases e lecitinases a 6,5 ºC e 21 ºC, respectivamente, o que indicou maior potencial deteriorador. Em espécies de bactérias gram-negativas e gram-positivas, constatou-se a produção de enzimas termorresistentes e adesão à superfície de aço inoxidável a 6,5 ºC. Os resultados deste estudo reforçaram a importância da implementação das boas práticas de produção e de fabricação na cadeia produtiva do leite para fins de prevenção de sua deterioração e minimização de perdas de qualidade e econômicas.Item Morphological changes in Salmonella Typhimurium caused by the lantibiotic bovicin HC5 in association with EDTA(Annals of Microbiology, 2015-07-03) Prudêncio, Cláudia Vieira; Ferreira, Sukarno Olavo; Mantovani, Hilário Cuquetto; Vanetti, Maria Cristina DantasBacteriocins, particularly those produced by Gram-positive bacteria, have in recent years been considered promising antimicrobial agents to inhibit bacterial growth in food, and thus are potential food preservatives. These peptides generally exhibit a spectrum of action limited to Gram-positive bacteria. However, their action can be extended to Gram-negative bacteria through association with chelating agents. In the present study, we evaluated the occurrence of morphological changes on the cell envelope of Salmonella Typhimurium cells treated with bovicin HC5—a lantibiotic from Streptococcus bovis HC5—in association with EDTA. The morphological changes of the cells were visualized by atomic force microscopy (AFM), and the increase in cell membrane permeability was confirmed by the leakage of potassium ions (K+). The images displayed changes in the cell envelope, with increased surface roughness and a decreased cell volume. These changes indicate that EDTA plays a role in the destabilization of the outer membrane, allowing bovicin HC5 to act on the cytoplasmic membrane through the formation of pores, which was confirmed by the detection of potassium in the cell supernatant. These results suggest that bovicin HC5 combined with EDTA has potential for use on Salmonella cells.Item N-dodecanoyl-homoserine lactone influences the levels of thiol and proteins related to oxidation-reduction process in Salmonella(PLOS ONE, 2018-10-10) Almeida, Felipe Alves de; Carneiro, Deisy Guimarães; Barros, Edvaldo; Pinto, Uelinton Manoel; Oliveira, Leandro Licursi de; Vanetti, Maria Cristina Dantas; Mendes, Tiago Antônio de OliveiraQuorum sensing is a cell-cell communication mechanism mediated by chemical signals that leads to differential gene expression in response to high population density. Salmonella is unable to synthesize the autoinducer-1 (AI-1), N-acyl homoserine lactone (AHL), but is able to recognize AHLs produced by other microorganisms through SdiA protein. This study aimed to evaluate the fatty acid and protein profiles of Salmonella enterica serovar Enteritidis PT4 578 throughout time of cultivation in the presence of AHL. The presence of N-dodecanoyl-homoserine lactone (C12-HSL) altered the fatty acid and protein profiles of Salmonella cultivated during 4, 6, 7, 12 and 36 h in anaerobic condition. The profiles of Salmonella Enteritidis at logarithmic phase of growth (4 h of cultivation), in the presence of C12-HSL, were similar to those of cells at late stationary phase (36 h). In addition, there was less variation in both protein and fatty acid profiles along growth, suggesting that this quorum sensing signal anticipated a stationary phase response. The presence of C12-HSL increased the abundance of thiol related proteins such as Tpx, Q7CR42, Q8ZP25, YfgD, AhpC, NfsB, YdhD and TrxA, as well as the levels of free cellular thiol after 6 h of cultivation, suggesting that these cells have greater potential to resist oxidative stress. Additionally, the LuxS protein which synthesizes the AI-2 signaling molecule was differentially abundant in the presence of C12-HSL. The NfsB protein had its abundance increased in the presence of C12-HSL at all evaluated times, which is a suggestion that the cells may be susceptible to the action of nitrofurans or that AHLs present some toxicity. Overall, the presence of C12-HSL altered important pathways related to oxidative stress and stationary phase response in Salmonella.Item Novel insights from molecular docking of SdiA from Salmonella enteritidis and Escherichia coli with quorum sensing and quorum quenching molecules(Microbial Pathogenesis, 2016-08-24) Almeida, Felipe Alves de; Pinto, Uelinton Manoel; Vanetti, Maria Cristina DantasQuorum sensing is a cell-to-cell communication mechanism leading to differential gene expression in response to high population density. The autoinducer-1 (AI-1) type quorum sensing system is incomplete in Escherichia coli and Salmonella due to the lack of the AI-1 synthase (LuxI homolog) responsible for acyl homoserine lactone (AHL) synthesis. However, these bacteria encode the AHL receptor SdiA (a LuxR homolog) leading to gene regulation in response to AI-1 produced by other bacteria. This study aimed to model the SdiA protein of Salmonella enterica serovar Enteritidis PT4 578 based on three crystallized SdiA structures from Enterohemorrhagic E. coli (EHEC) with different ligands. Molecular docking of these predicted structures with AHLs, furanones and 1-octanoyl-rac-glycerol were also performed. The available EHEC SdiA structures provided good prototypes for modeling SdiA from Salmonella. The molecular docking of these proteins showed that residues Y63, W67, Y71, D80 and S134 are common binding sites for different quorum modulating signals, besides being conserved among other LuxR type proteins. We also show that AHLs with twelve carbons presented better binding affinity to SdiA than AHLs with smaller side chains in our docking analysis, regardless of the protein structures used. Interestingly, the conformational changes provided by AHL binding resulted in structural models with increased affinities to brominated furanones. These results suggest that the use of brominated furanones to inhibit phenotypes controlled by quorum sensing in Salmonella and EHEC may present a good strategy since these inhibitors seem to specifically compete with AHLs for binding to SdiA in both pathogens.Item Performance of two alternative methods for Listeria detection throughout Serro Minas cheese ripening(Brazilian Journal of Microbiology, 2016-04-22) Mata, Gardênia Márcia Silva Campos; Martins, Evandro; Machado, Solimar Gonçalves; Vanetti, Maria Cristina Dantas; Pinto, Maximiliano Soares; Carvalho, Antônio Fernandes deThe ability of pathogens to survive cheese ripening is a food-security concern. Therefore, this study aimed to evaluate the performance of two alternative methods of analysis of Listeria during the ripening of artisanal Minas cheese. These methods were tested and compared with the conventional method: Lateral Flow System™, in cheeses produced on laboratory scale using raw milk collected from different farms and inoculated with Listeria innocua; and VIDAS®-LMO, in cheese samples collected from different manufacturers in Serro, Minas Gerais, Brazil. These samples were also characterized in terms of lactic acid bacteria, coliforms and physical–chemical analysis. In the inoculated samples, L. innocua was detected by Lateral Flow System™ method with 33% false-negative and 68% accuracy results. L. innocua was only detected in the inoculated samples by the conventional method at 60-days of cheese ripening. L. monocytogenes was not detected by the conventional and the VIDAS®-LMO methods in cheese samples collected from different manufacturers, which impairs evaluating the performance of this alternative method. We concluded that the conventional method provided a better recovery of L. innocua throughout cheese ripening, being able to detect L. innocua at 60-day, aging period which is required by the current legislation.