1,428 research outputs found
Avaliação do potencial antimicrobiano de óleos essenciais e nisina
No full textTese de mestrado, Microbiologia Aplicada, Universidade de Lisboa, Faculdade de Ciências, 2016Os microrganismos deteriorativos e patogénicos de origem alimentar são ubíquos e continuam a ser uma importante causa de perdas económicas ao nível da produção e de doenças veiculadas por alimentos. Adicionalmente, o aumento crescente de microrganismos resistentes aos antibióticos e desinfetantes, associado à capacidade de formação de biofilmes, constitui um grave problema para a segurança alimentar e uma preocupação crescente na área da saúde pública. O presente estudo teve como principal objetivo a avaliação da atividade antimicrobiana de dois óleos essenciais -OEs- (tomilho e erva-príncipe) e de uma bacteriocina (nisina) sobre microrganismos comummente presentes nos alimentos, nomeadamente Enterococcus faecalis, Listeria monocytogenes, Aeromonas hydrophila e Brochothrix thermosphacta. A ação antimicrobiana dos compostos em análise foi testada tendo como alvo células planctónicas e biofilmes (culturas puras e mistas), tendo sido estudados diferentes tempos de incubação, temperaturas e superfícies de contacto (poliestireno e aço inoxidável). Os compostos antimicrobianos foram utilizados puros ou em combinação, de forma a comprovar possíveis efeitos sinérgicos. Analisando a ação antimicrobiana dos OEs e nisina (tanto individualmente como em combinação) sobre culturas puras e mistas de microrganismos, o OEtomilho demonstrou possuir uma atividade antimicrobiana superior, sendo necessárias menores concentrações deste OE para que ocorra inibição do crescimento microbiano. Quanto ao OEerva-príncipe e nisina, embora também possuam potencial antimicrobiano, são necessárias concentrações mais elevadas para que haja um efeito eficaz. No que diz respeito à ação sinérgica dos compostos antimicrobianos, esta foi demonstrada apenas para algumas das combinações em análise. Quanto à capacidade de erradicação de biofilme, constatou-se que os dois OEs em estudo foram eficazes sobre todas as culturas puras testadas, com uma única exceção (OEerva-príncipe foi incapaz de erradicar o biofilme formado por um dos isolados da espécie E. faecalis em análise). Relativamente à capacidade de erradicação do biofilme formado por culturas mistas, os compostos em análise foram eficazes apenas em metade das situações testadas. Em conclusão, após avaliação da possível aplicabilidade de OEs e nisina como agentes antimicrobianos contra microrganismos patogénicos e deteriorativos presentes nos alimentos, considera-se que estes compostos naturais podem constituir uma importante mais-valia para o desenvolvimento de novas estratégias preventivas a implementar na indústria alimentar.Deteriorative and pathogenic foodborne microorganisms are ubiquitous and continue to be a major cause of economic losses in terms of food production and foodborne illnesses. Moreover, the increasing number of microorganisms resistant to antibiotics and disinfectants, associated with biofilm formation capacity, constitute a serious problem for food safety and a growing concern regarding public health. This study's main objetive was to evaluate the antimicrobial activity of two essential oils -EOs- (thyme and lemongrass) and a bacteriocin (nisin) against microorganisms commonly present in food, including Enterococcus faecalis, Listeria monocytogenes, Aeromonas hydrophila, and Brochothrix thermosphacta. The antimicrobial action of the compounds was tested against planktonic cells and biofilms (both pure and mixed cultures) using different incubation periods, temperatures and contact surfaces (polystyrene and stainless steel). The antimicrobial compounds were used individually or in combination, in order to establish possible synergistic effects. Analyzing the antimicrobial activities of nisin and EOs (both individually or in combination) on pure and mixed cultures of microorganisms, EOthyme showed a superior antimicrobial activity, requiring lower concentrations of EO in order to inhibit microbial growth. As for the EOlemongrass and nisin, although both possess antimicrobial potential, higher concentrations are needed to achieve successful inhibition. Regarding the synergistic action of antimicrobial compounds, it could only be demonstrated for some of the combinations analyzed. Regarding the ability to eradicate biofilms, it was found that the two EOs were effective on all tested pure cultures, with one exception (EOlemongrass was unable to eradicate the biofilm formed by one of the E. faecalis analyzed). Considering the ability to eradicate biofilms formed by mixed cultures, the tested compounds were effective only in half of the cases tested. In conclusion, after evaluation of the putative applicability of EOs and nisin as antimicrobial agents against pathogenic and deteriorative microorganisms present in food, these natural compounds can be considered an important asset for the development of new preventive strategies to be implemented in the food industry
Avaliação do potencial antimicrobiano de óleos essenciais e nisina
No full textTese de mestrado, Microbiologia Aplicada, Universidade de Lisboa, Faculdade de Ciências, 2016Os microrganismos deteriorativos e patogénicos de origem alimentar são ubíquos e continuam a ser uma importante causa de perdas económicas ao nível da produção e de doenças veiculadas por alimentos. Adicionalmente, o aumento crescente de microrganismos resistentes aos antibióticos e desinfetantes, associado à capacidade de formação de biofilmes, constitui um grave problema para a segurança alimentar e uma preocupação crescente na área da saúde pública. O presente estudo teve como principal objetivo a avaliação da atividade antimicrobiana de dois óleos essenciais -OEs- (tomilho e erva-príncipe) e de uma bacteriocina (nisina) sobre microrganismos comummente presentes nos alimentos, nomeadamente Enterococcus faecalis, Listeria monocytogenes, Aeromonas hydrophila e Brochothrix thermosphacta. A ação antimicrobiana dos compostos em análise foi testada tendo como alvo células planctónicas e biofilmes (culturas puras e mistas), tendo sido estudados diferentes tempos de incubação, temperaturas e superfícies de contacto (poliestireno e aço inoxidável). Os compostos antimicrobianos foram utilizados puros ou em combinação, de forma a comprovar possíveis efeitos sinérgicos. Analisando a ação antimicrobiana dos OEs e nisina (tanto individualmente como em combinação) sobre culturas puras e mistas de microrganismos, o OEtomilho demonstrou possuir uma atividade antimicrobiana superior, sendo necessárias menores concentrações deste OE para que ocorra inibição do crescimento microbiano. Quanto ao OEerva-príncipe e nisina, embora também possuam potencial antimicrobiano, são necessárias concentrações mais elevadas para que haja um efeito eficaz. No que diz respeito à ação sinérgica dos compostos antimicrobianos, esta foi demonstrada apenas para algumas das combinações em análise. Quanto à capacidade de erradicação de biofilme, constatou-se que os dois OEs em estudo foram eficazes sobre todas as culturas puras testadas, com uma única exceção (OEerva-príncipe foi incapaz de erradicar o biofilme formado por um dos isolados da espécie E. faecalis em análise). Relativamente à capacidade de erradicação do biofilme formado por culturas mistas, os compostos em análise foram eficazes apenas em metade das situações testadas. Em conclusão, após avaliação da possível aplicabilidade de OEs e nisina como agentes antimicrobianos contra microrganismos patogénicos e deteriorativos presentes nos alimentos, considera-se que estes compostos naturais podem constituir uma importante mais-valia para o desenvolvimento de novas estratégias preventivas a implementar na indústria alimentar.Deteriorative and pathogenic foodborne microorganisms are ubiquitous and continue to be a major cause of economic losses in terms of food production and foodborne illnesses. Moreover, the increasing number of microorganisms resistant to antibiotics and disinfectants, associated with biofilm formation capacity, constitute a serious problem for food safety and a growing concern regarding public health. This study's main objetive was to evaluate the antimicrobial activity of two essential oils -EOs- (thyme and lemongrass) and a bacteriocin (nisin) against microorganisms commonly present in food, including Enterococcus faecalis, Listeria monocytogenes, Aeromonas hydrophila, and Brochothrix thermosphacta. The antimicrobial action of the compounds was tested against planktonic cells and biofilms (both pure and mixed cultures) using different incubation periods, temperatures and contact surfaces (polystyrene and stainless steel). The antimicrobial compounds were used individually or in combination, in order to establish possible synergistic effects. Analyzing the antimicrobial activities of nisin and EOs (both individually or in combination) on pure and mixed cultures of microorganisms, EOthyme showed a superior antimicrobial activity, requiring lower concentrations of EO in order to inhibit microbial growth. As for the EOlemongrass and nisin, although both possess antimicrobial potential, higher concentrations are needed to achieve successful inhibition. Regarding the synergistic action of antimicrobial compounds, it could only be demonstrated for some of the combinations analyzed. Regarding the ability to eradicate biofilms, it was found that the two EOs were effective on all tested pure cultures, with one exception (EOlemongrass was unable to eradicate the biofilm formed by one of the E. faecalis analyzed). Considering the ability to eradicate biofilms formed by mixed cultures, the tested compounds were effective only in half of the cases tested. In conclusion, after evaluation of the putative applicability of EOs and nisin as antimicrobial agents against pathogenic and deteriorative microorganisms present in food, these natural compounds can be considered an important asset for the development of new preventive strategies to be implemented in the food industry
Avaliação do potencial antimicrobiano de óleos essenciais e nisina
No full textTese de mestrado, Microbiologia Aplicada, Universidade de Lisboa, Faculdade de Ciências, 2016Os microrganismos deteriorativos e patogénicos de origem alimentar são ubíquos e continuam a ser uma importante causa de perdas económicas ao nível da produção e de doenças veiculadas por alimentos. Adicionalmente, o aumento crescente de microrganismos resistentes aos antibióticos e desinfetantes, associado à capacidade de formação de biofilmes, constitui um grave problema para a segurança alimentar e uma preocupação crescente na área da saúde pública. O presente estudo teve como principal objetivo a avaliação da atividade antimicrobiana de dois óleos essenciais -OEs- (tomilho e erva-príncipe) e de uma bacteriocina (nisina) sobre microrganismos comummente presentes nos alimentos, nomeadamente Enterococcus faecalis, Listeria monocytogenes, Aeromonas hydrophila e Brochothrix thermosphacta. A ação antimicrobiana dos compostos em análise foi testada tendo como alvo células planctónicas e biofilmes (culturas puras e mistas), tendo sido estudados diferentes tempos de incubação, temperaturas e superfícies de contacto (poliestireno e aço inoxidável). Os compostos antimicrobianos foram utilizados puros ou em combinação, de forma a comprovar possíveis efeitos sinérgicos. Analisando a ação antimicrobiana dos OEs e nisina (tanto individualmente como em combinação) sobre culturas puras e mistas de microrganismos, o OEtomilho demonstrou possuir uma atividade antimicrobiana superior, sendo necessárias menores concentrações deste OE para que ocorra inibição do crescimento microbiano. Quanto ao OEerva-príncipe e nisina, embora também possuam potencial antimicrobiano, são necessárias concentrações mais elevadas para que haja um efeito eficaz. No que diz respeito à ação sinérgica dos compostos antimicrobianos, esta foi demonstrada apenas para algumas das combinações em análise. Quanto à capacidade de erradicação de biofilme, constatou-se que os dois OEs em estudo foram eficazes sobre todas as culturas puras testadas, com uma única exceção (OEerva-príncipe foi incapaz de erradicar o biofilme formado por um dos isolados da espécie E. faecalis em análise). Relativamente à capacidade de erradicação do biofilme formado por culturas mistas, os compostos em análise foram eficazes apenas em metade das situações testadas. Em conclusão, após avaliação da possível aplicabilidade de OEs e nisina como agentes antimicrobianos contra microrganismos patogénicos e deteriorativos presentes nos alimentos, considera-se que estes compostos naturais podem constituir uma importante mais-valia para o desenvolvimento de novas estratégias preventivas a implementar na indústria alimentar.Deteriorative and pathogenic foodborne microorganisms are ubiquitous and continue to be a major cause of economic losses in terms of food production and foodborne illnesses. Moreover, the increasing number of microorganisms resistant to antibiotics and disinfectants, associated with biofilm formation capacity, constitute a serious problem for food safety and a growing concern regarding public health. This study's main objetive was to evaluate the antimicrobial activity of two essential oils -EOs- (thyme and lemongrass) and a bacteriocin (nisin) against microorganisms commonly present in food, including Enterococcus faecalis, Listeria monocytogenes, Aeromonas hydrophila, and Brochothrix thermosphacta. The antimicrobial action of the compounds was tested against planktonic cells and biofilms (both pure and mixed cultures) using different incubation periods, temperatures and contact surfaces (polystyrene and stainless steel). The antimicrobial compounds were used individually or in combination, in order to establish possible synergistic effects. Analyzing the antimicrobial activities of nisin and EOs (both individually or in combination) on pure and mixed cultures of microorganisms, EOthyme showed a superior antimicrobial activity, requiring lower concentrations of EO in order to inhibit microbial growth. As for the EOlemongrass and nisin, although both possess antimicrobial potential, higher concentrations are needed to achieve successful inhibition. Regarding the synergistic action of antimicrobial compounds, it could only be demonstrated for some of the combinations analyzed. Regarding the ability to eradicate biofilms, it was found that the two EOs were effective on all tested pure cultures, with one exception (EOlemongrass was unable to eradicate the biofilm formed by one of the E. faecalis analyzed). Considering the ability to eradicate biofilms formed by mixed cultures, the tested compounds were effective only in half of the cases tested. In conclusion, after evaluation of the putative applicability of EOs and nisin as antimicrobial agents against pathogenic and deteriorative microorganisms present in food, these natural compounds can be considered an important asset for the development of new preventive strategies to be implemented in the food industry
Photoproduction of with neutron tagging in ultra-peripheral collisions of nuclei at RHIC and the LHC
No full textWe present predictions for the cross sections of the coherent and incoherent
photoproduction in ultra-peripheral collisions at RHIC and at the LHC
calculated for different classes of events depending on the presence of
neutrons emitted by colliding nuclei. Since strong nucleus-nucleus interactions
in UPCs are suppressed, it is usually assumed that neutrons at forward
rapidities originate mainly from the electromagnetic dissociation of colliding
nuclei caused by additional photon exchanges. This is a reasonable assumption
for the coherent photoproduction where the state of the target nucleus remains
intact. We consider additional sources of neutrons in the incoherent
quasielastic and nucleon dissociative photoproduction and show that
these processes significantly change probabilities of neutron emission compared
to calculations when only neutrons from electromagnetic dissociation of nuclei
are considered. Such studies should allow one to explore the dynamics of
nuclear shadowing in the incoherent photoproduction down to .Comment: 20 pages, 9 figures, new version accepted by PR
Photoproduction of light vector mesons in Xe–Xe ultraperipheral collisions at the LHC and the nuclear density of Xe-129
No full textWe make predictions for cross sections of ρ and φ vector meson photoproduction in ultraperipheral
Xe–Xe collisions at √sN N = 5.44 TeV. Analyzing the momentum transfer distribution of ρ mesons in this
process, we explore the feasibility of extracting the nuclear density of 129Xe, which is needed in searches
for dark matter with Xenon-based detectors.peerReviewe
Incoherent meson photoproduction in ultraperipheral nuclear collisions at the CERN Large Hadron Collider
No full textUsing the Gribov-Glauber model for photon-nucleus scattering and a generalization of the vector meson dominance model for the hadronic structure of the photon, we make predictions for the cross section of incoherent ρ photoproduction in Pb-Pb ultraperipheral collisions in the Large Hadron Collider kinematics. We find that the effect of the inelastic nuclear shadowing is significant and leads to an additional 25% suppression of the incoherent cross section. Comparing our predictions to those of the STARlight Monte Carlo framework, we observe very significant differences.Using the Gribov-Glauber model for photon-nucleus scattering and a generalization of the vector meson dominance model for the hadronic structure of the photon, we make predictions for the cross section of incoherent photoproduction in Pb-Pb ultraperipheral collisions (UPCs) in the Large Hadron Collider kinematics. We find that the effect of the inelastic nuclear shadowing is significant and leads to an additional 25% suppression of the incoherent cross section. Comparing our predictions to those of the STARlight Monte Carlo framework, we observe very significant differences
Upcgen: a Monte Carlo simulation program for dilepton pair production in ultra-peripheral collisions of heavy ions
No full textUltra-peripheral collisions (UPCs) of heavy ions can be used as a clean
environment to study two-photon induced interactions such as dilepton pair
photoproduction. Recently, precise data on lepton pair production in UPCs were
obtained by the ATLAS experiment at the LHC where significant deviations, of up
to 20%, from available theoretical predictions were observed. In this work, we
present a Monte Carlo event generator, Upcgen, that implements a refined
treatment of the photon flux allowing us to improve the agreement with ATLAS
data at large dilepton rapidities. Besides, the new generator offers a
possibility to study photon polarization effects and set arbitrary values of
the lepton anomalous magnetic moment that can be used in the future studies of
tau g-2 via ditau production measurements in UPCs.Comment: 28 pages, 11 figures, to be submitted to Computer Physics
Communication
Rationale for vaccination with trivalent or quadrivalent live attenuated influenza vaccines: Protective vaccine efficacy in the ferret model
No full textBackground and aim The majority of seasonal influenza vaccines are trivalent, containing two A virus strains (H1N1 and H3N2) and one B virus strain. The co-circulation of two distinct lineages of B viruses can lead to mismatch between the influenza B virus strain recommended for the trivalent seasonal vaccine and the circulating B virus. This has led some manufacturers to produce quadrivalent influenza vaccines containing one strain from each B lineage in addition to H1N1 and H3N2 strains. However, it is also important to know whether vaccines containing a single influenza B strain can provide cross-protectivity against viruses of the antigenically distinct lineage. The aim of this study was to assess in naïve ferrets the potential cross-protective activity of trivalent live attenuated influenza vaccine (T-LAIV) against challenge with a heterologous wild-type influenza B virus belonging to the genetically different lineage and to compare this activity with effectiveness of quadrivalent LAIV (Q-LAIV) in the ferret model. Methods and results Ferrets were vaccinated with either one dose of trivalent LAIV containing B/Victoria or B/ Yamagata lineage virus, or quadrivalent LAIV (containing both B lineages), or placebo. They were then challenged with B/Victoria or B/Yamagata lineage wild-type virus 28 days after vaccination. The ferrets were monitored for clinical signs and morbidity. Nasal swabs and lung tissue samples were analyzed for the presence of challenge virus. Antibody response to vaccination was assessed by routine hemagglutination inhibition assay. All LAIVs tested were found to be safe and effective against wild-type influenza B viruses based on clinical signs, and virological and histological data. The absence of interference between vaccine strains in trivalent and quadrivalent vaccine formulations was confirmed. Trivalent LAIVs were shown to have the potential to be cross-protective against infection with genetically different influenza B/Victoria and B/Yamagata lineages. Conclusions In this ferret model, quadrivalent vaccine provided higher protection to challenge against both B/Victoria and B/Yamagata lineage viruses. However, T-LAIV provided some cross-protection in the case of a mismatch between circulating and vaccine type B strains. Notably, B/Victoria-based T-LAIV was more protective compared to B/Yamagata-based T-LAIV. © 2018 World Health Organization. Licensee Public Library of Science. This is an open access article distributed under the Creative Commons Attribution IGO License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
- …
