Variability in the response of salmonella and listeria strains to different strategies for inactivation

[ENG] The last EFSA report, notified a total of 5146 food outbreaks in the European Union in 2018. The food industry plays an important role in the food chain and has to adapt and reinvent itself when consumers place certain demands on products. Food safety is the first issue to take into account. There is already a large variety of microbiological species that are capable of developing in food and the safety of food makes it questionable whether or not the product is suitable for consumption. Listeria monocytogenes and Salmonella spp. are characterised by being two ubiquitous microbial species capable of living in borderline conditions of pH, water activity and sodium chloride concentrations. Another circumstance of these two microorganisms is the variability between their different strains and the capacity they have to recover from the different stresses to which they are subjected. For these reasons, it is of utmost importance to know their response to stress in order to control their inactivation and/or development in any situation. This knowledge will enable to efficiently apply technologies and treatments that are capable of inactivating or inhibiting growth of microorganisms, so to prevent or, at least, reduce food contamination. So, in this thesis, the main objective was to study the application of different strategies for the inactivation of L monocytogenes and Salmonella that could reduce the intensity of the treatments, while ensuring food safety. In this thesis, the effect that different inactivation strategies have on L. monocytogenes and Salmonella spp. has been studied. Firstly, the heat resistance of four L. monocytogenes strains -Scott A, CECT 4031, CECT 4032 and 12MOB052- in three different matrices -buffered peptone water (BPW), pH 7 Mcllvaine phosphate citrate buffer and a last one of food origin; semi- skimmed milk- was studied. Under isothermal conditions, there was no between-strains and between-media variability in the resistance. However, when this experiment was carried out under dynamic conditions, some strains were able to develop acclimation to stress, leading to important differences in resistance. Between-strains, the CECT 4031 increased its D-value by 10, with CECT 4032 being the least acclimated and between-media, peptone water buffer and semi- skimmed milk were the mediums where most acclimation was found. These results are of great importance, as they highlight that some mechanisms of heat resistance may not be detected when conditions, such as acclimation.Another part of the research was carried out to evaluate the response to heat when Salmonella Senftenberg and S. Enteritidis - the treatment applied is under isothermal conditions, but they show up under dynamic heating were exposed to a previous acid shock. Both serovars of Salmonella were grown at pH 4.5 and subsequently exposed to heat treatment under isothermal conditions at four different temperatures. The heating medium used was peptone water at pH 4.5 and 7.0. The results showed that both serovars had a different response to a heat treatment after the exposure to acid. On the one hand, S. Senftenberg reduced its heat resistance when subjected to a previous acid shock, while in S. Enteritidis its heat resistance increased. Again, these results bring out the inherent variability in microorganisms, in this case related to a stress response mechanisms. Finally, the effectiveness of the combination of applying electrical pulses (PEF) and oregano essential oil to L. monocytogenes was determined. The medium used was a Mcllvaine buffer at pH 7 with a conductivity of 6 μS/cm. On the one hand, the efficiency of the electric field was evaluated between 5 and 20 kV/cm and it was found that after 60 pulses at 20 kV/cm field strength, 1 Hz frequency and 20 μs pulse width, an inactivation of 2.01 log10 cycles was achieved, while to achieve a similar level of inactivation at 15 kV/cm, 300 pulses were required. Then, PEF treatments were then applied (20 kV/cm field strength, 60 pulses, 1 Hz frequency and 20 μs pulse width) after having exposed the cells to the minimum inhibitory concentration (MIC) of the oregano essential oil (2000 ppm) and these results showed no significant differences (p>0.05) with respect to the PEF treatments applied alone. However, when the same PEF treatment as above was applied first and then the surviving microorganisms were resuspended on the MIC of oregano essential oil, significant differences (p0,05) con respecto a los tratamientos PEAV aplicados solos. Sin embargo, cuando se aplicó primero el mismo tratamiento PEAV que el anterior y luego se resuspendió a los microorganismos sobrevivientes en la CIM del aceite esencial de orégano, se encontraron diferencias significativas (p<0,05) con respecto al FEM aplicado solo y al PEAV después del orégano. También se encontró que al reducir a 1/16 la CIM (125 ppm) el efecto fue el mismo que si aplicáramos la CIM. Para concluir, esta tesis ha investigado cómo pueden combinarse diferentes estrategias de inactivación microbiana para conseguir un alimento seguro con un tratamiento más suave, que en un solo tratamiento convencional. También ha ayudado a abordar las predicciones para futuros estudios y como contribución a la industria alimentaria mejorará la cuantificación de la evaluación de riesgos microbiológicos.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de Doctorado de Técnicas avanzadas en investigación y desarrollo agrario y alimentari

Epithelial Cell Division: Keeping Aneuploidy Levels in Check

SummaryAneuploidy is deleterious at the cellular and organismal level and can promote tumorigenesis. Two new studies in Drosophila imaginal discs underscore the cellular and tissue-wide mechanisms that prevent the accumulation of aneuploid cells in symmetrically dividing epithelial tissues upon changes in centrosome number

A influência da gestão de recursos humanos e organização do trabalho dos enfermeiros na prática dos cuidados que prestam aos utentes no período perioperatório e o grau de satisfação destes com esses cuidados

RESUMO: Este estudo subordinado ao tema “A influência da Gestão de Recursos Humanos e Organização do trabalho dos Enfermeiros na prática dos cuidados que prestam aos utentes no período perioperatório e o grau de satisfação destes com esses cuidados”, pretende analisar as percepções de trinta enfermeiros do Bloco Operatório relativamente ao clima, cultura organizacional e politicas de recursos humanos, no Hospital Nossa Senhora do Rosário, E.P.E.. Pretende também avaliar a satisfação de cento e quatro utentes com os cuidados de enfermagem no período perioperatório. Os resultados permitiram verificar que as estratégias de recursos humanos e os modelos de organização do trabalho foram determinantes para as práticas de enfermagem e estas contribuíram para a satisfação dos utentes. ABSTRACT: This study entitled “The influence of Human Resources Management and the Organisation of Work of nursing practice regarding care given to patients in the period perisurgery, and the degree of patients’ satisfaction with their care” aims to investigate the perceptions of thirty nurses from the Operating Room regarding the climate and organisational culture, and politics of Human Resources Management at Nossa Senhora do Rosario Hospital (Public Entity Enterprise). It also intends to evaluate the satisfaction of one hundred and forty patients regarding their nursing care in the period perisurgery. The results obtained verified that human resources strategies and the models of organisation of work are fundamental to the practice of nursing care, and these contribute for the satisfaction of the patients

Pop-up hotels versus chain hotels: does the type of hotel accommodation influence the traveler’s risk-taking behavior?

This research aims to understand if the type of hotel accommodation, i.e. pop-up versus chain hotel, can have an effect on thetravelers’ risk-taking behavior during the staying period. It was predicted that a pop-up hotel would lead to a higher risk-taking intention in the recreational and health domains, due to a higher ‘fling’ perception and consequent identity change while ina pop-up environment. An experiment was conducted to test the prediction. Data analyses including an ANOVA, ANCOVA and a serial mediation model showed that the pop-up hotel leads to higher recreational risk-intentions, however, no indirect relationships of ‘fling’ and identity change supported the casual chain predicted. Thus, it remains unknown what caused the higher recreational risk intentions, however possible underlying mechanisms are suggested. Finally, managerial implications are discussed based on the findings regarding the connection between hotels, ‘fling’ relationship and identity change

Sequences of purchases in credit card data reveal life styles in urban populations

Zipf-like distributions characterize a wide set of phenomena in physics, biology, economics and social sciences. In human activities, Zipf-laws describe for example the frequency of words appearance in a text or the purchases types in shopping patterns. In the latter, the uneven distribution of transaction types is bound with the temporal sequences of purchases of individual choices. In this work, we define a framework using a text compression technique on the sequences of credit card purchases to detect ubiquitous patterns of collective behavior. Clustering the consumers by their similarity in purchases sequences, we detect five consumer groups. Remarkably, post checking, individuals in each group are also similar in their age, total expenditure, gender, and the diversity of their social and mobility networks extracted by their mobile phone records. By properly deconstructing transaction data with Zipf-like distributions, this method uncovers sets of significant sequences that reveal insights on collective human behavior.Comment: 30 pages, 26 figure

Development of an Embedded Myokinetic Prosthetic Hand Controller

The quest for an intuitive and physiologically appropriate human machine interface for the control of dexterous prostheses is far from being completed. In the last decade, much effort has been dedicated to explore innovative control strategies based on the electrical signals generated by the muscles during contraction. In contrast, a novel approach, dubbed myokinetic interface, derives the control signals from the localization of multiple magnetic markers (MMs) directly implanted into the residual muscles of the amputee. Building on this idea, here we present an embedded system based on 32 magnetic field sensors and a real time computation platform. We demonstrate that the platform can simultaneously localize in real-time up to five MMs in an anatomically relevant workspace. The system proved highly linear (R2 = 0.99) and precise (1% repeatability), yet exhibiting short computation times (4 ms) and limited cross talk errors (10% the mean stroke of the magnets). Compared to a previous PC implementation, the system exhibited similar precision and accuracy, while being ~75% faster. These results proved for the first time the viability of using an embedded system for magnet localization. They also suggest that, by using an adequate number of sensors, it is possible to increase the number of simultaneously tracked MMs while introducing delays that are not perceivable by the human operator. This could allow to control more degrees of freedom than those controllable with current technologies

Evaluation of constitutive iron reductase (AtFRO2) expression on mineral accumulation and distribution in soybean (Glycinemax.L)

Iron is an important micronutrient in human and plant nutrition. Adequate iron nutrition during crop production is central for assuring appropriate iron concentrations in the harvestable organs, for human food or animal feed. The whole-plant movement of iron involves several processes, including the reduction of ferric to ferrous iron at several locations throughout the plant, prior to transmembrane trafficking of ferrous iron. In this study, soybean plants that constitutively expressed the AtFRO2 iron reductase gene were analyzed for leaf iron reductase activity, as well as the effect of this transgene's expression on root, leaf, pod wall, and seed mineral concentrations. High Fe supply, in combination with the constitutive expression of AtFRO2, resulted in significantly higher concentrations of different minerals in roots (K, P, Zn, Ca, Ni, Mg, and Mo), pod walls (Fe, K, P, Cu, and Ni), leaves (Fe, P, Cu, Ca, Ni, and Mg) and seeds (Fe, Zn, Cu, and Ni). Leaf and pod wall iron concentrations increased as much as 500% in transgenic plants, while seed iron concentrations only increased by 10%, suggesting that factors other than leaf and pod wall reductase activity were limiting the translocation of iron to seeds. Protoplasts isolated from transgenic leaves had three-fold higher reductase activity than controls. Expression levels of the iron storage protein, ferritin, were higher in the transgenic leaves than in wild-type, suggesting that the excess iron may be stored as ferritin in the leaves and therefore unavailable for phloem loading and delivery to the seeds. Also, citrate and malate levels in the roots and leaves of transgenic plants were significantly higher than in wild-type, suggesting that organic acid production could be related to the increased accumulation of minerals in roots, leaves, and pod walls, but not in the seeds. All together, these results suggest a more ubiquitous role for the iron reductase in whole-plant mineral accumulation and distribution.info:eu-repo/semantics/publishedVersio