Browsing by Author "Silva, Vanessa"
Now showing 1 - 10 of 15
Results Per Page
Sort Options
- Antibiotic resistance among gastrointestinal bacteria in broilers: a review focused on Enterococcus spp. and Escherichia coliPublication . Ribeiro, Jessica; Silva, Vanessa; Monteiro, Andreia; Vieira-Pinto, Madalena; Igrejas, Gilberto; Reis, Filipa S.; Barros, Lillian; Poeta, PatríciaSimple Summary Chicken meat has become one of the most consumed meats worldwide, and antibiotics have been used to ensure high levels of production. However, antibiotic usage in animal production has contributed to the development of antibiotic-resistant bacteria, largely among intestinal microbiota. Enterococcus spp. and Escherichia coli are frequently found in the gastrointestinal tract of chickens, and the presence of resistant strains has been revealed by several studies. Enterococcus spp. isolated from broilers have shown resistance to at least seven classes of antibiotics, while E. coli have shown resistance to at least four. Furthermore, some clonal lineages, such as ST16, ST194, and ST195 in Enterococcus spp. and ST117 in E. coli, have been identified in broilers and humans. These data suggest that bacteria can be transmitted through the consumption of contaminated animal-source food, direct contact with animals, or environmental exposure. Therefore, the main goal of this review was to highlight the existing literature on the gastrointestinal microbiota in broilers and antibiotic-resistant Enterococcus spp. and E. coli of broiler origin. Chickens can acquire bacteria at different stages, and bacterial diversity can occur due to production practices, diet, and environment. The changes in consumer trends have led to increased animal production, and chicken meat is one of the most consumed meats. To ensure high levels of production, antimicrobials have been used in livestock for therapeutic purposes, disease prevention, and growth promotion, contributing to the development of antimicrobial resistance across the resident microbiota. Enterococcus spp. and Escherichia coli are normal inhabitants of the gastrointestinal microbiota of chickens that can develop strains capable of causing a wide range of diseases, i.e., opportunistic pathogens. Enterococcus spp. isolated from broilers have shown resistance to at least seven classes of antibiotics, while E. coli have shown resistance to at least four. Furthermore, some clonal lineages, such as ST16, ST194, and ST195 in Enterococcus spp. and ST117 in E. coli, have been identified in humans and animals. These data suggest that consuming contaminated animal-source food, direct contact with animals, or environmental exposure can lead to the transmission of antimicrobial-resistant bacteria. Therefore, this review focused on Enterococcus spp. and E. coli from the broiler industry to better understand how antibiotic-resistant strains have emerged, which antibiotic-resistant genes are most common, what clonal lineages are shared between broilers and humans, and their impact through a One Health perspective.
- Antimicrobial activity and phenolic profile of chestnut (Castanea sativa Mill.) by-productsPublication . Silva, Vanessa; Falco, Virgílio; Dias, Maria Inês; Barros, Lillian; Amaral, Joana S.; Igrejas, Gilberto; Ferreira, Isabel C.F.R.; Poeta, PatríciaDifferent agro-industrial by-products have been described as potential sources of phenolic compounds, which have been reported to exhibit several properties, such as, antimicrobial, antioxidant, anti-inflammatory, antimutagentic and cardioprotective [1]. During chestnut (Castanea sativa Mill.) processing, a large amount of wastes are generated that could be used as interesting and cheap sources of these compounds [2]. Therefore, this study aimed to extract phenolic compounds from chestnut by-products of Longal variety and evaluate their antimicrobial activity against antibiotic resistant bacteria. The phenolic compounds were extracted from different parts of the chestnut, namely the shell, inner shell and bur, as well as from the leaves of chestnut tree. The extraction was performed with 100% ethanol, which was eliminated by rotoevaporation at low temperature (40ºC) and the obtained residue was re-dissolved in DMSO to a final concentration of 100, 75, 50, 25 and 10 mg/mL for the antimicrobial activity assay. The antimicrobial susceptibility assay was performed using the Kirby-Bauer disc diffusion method against 6 Gram-positive bacteria: Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Listeria monocytogenes; and 4 Gram-negative bacteria: Escherichia coli, Salmonella enteritidis, Klebsiella pneumoniae, Pseudomonas aeruginosa. For the phenolic compounds analysis, the extracts were dissolved in ethanol and the analysis was performed by HPLC-DAD-ESI/MS. The individual major phenolic compounds identified and quantified in the chestnut by-products were gallic acid, ellagic acid, trigalloyl-HHDP-glucose and quercetin, syringetin and myricetin glycoside derivatives. All the extracts showed antibacterial activity, with the inner shell’s extract being effective against all Gram-positive and two Gram-negative bacteria. This extract presented syringetin-3-O-galactoside and myricetin glycoside derivatives as the main phenolic compounds. None of the extracts had antibacterial activity against E. coli and S. enteritidis, while S. aureus and S. epidermidis showed susceptibility to all tested extracts. The obtained results show that chestnut by-products are a good source of phenolic compounds with antimicrobial activity, being a potential tool to potentiate antibiotic effects in combating multidrug-resistant bacteria.
- Antimicrobial activity of polyphenols extracted from winery by-products against antibiotic resistant bacteriaPublication . Silva, Vanessa; Igrejas, Gilberto; Falco, Virgílio; Amaral, Joana S.; Poeta, PatríciaThe emergence of dmg resistant bacteria worldwide is becoming a threat to human health since commonly used antibiotics are no longer effective against these bacteria. Therefore, it is necessary to investigate and develop new effective antimicrobials. Polyphenols are secondary metabolites of plants which confer health protective benefits. Several studies have demonstrated the antimicrobial activity of these compounds since they cause structural or functional damage to the bacterial cell membrane. Agro-industrial byproducts, namely from the winey industry, are a potential source of polyphenols and can be used as cheap source of these compounds. Thus, the aim of this study was to extract the polyphenols from the winery by-products and evaluate their antimicrobial activity against antibiotic re sistant bacteria.
- Avaliação do desempenho e mudança em contabilidade de gestão: o caso do Direção Regional de Administração Educativa da Região Autónoma da MadeiraPublication . Silva, Vanessa; Pires, Amélia M.M.; Leite, JoaquimOs objetivos desta investigação foram compreender como e por que foi introduzido o istema Integrado de gestão e Avaliação do Desempenho na Administração Pública (SIADAP) na Região Autónoma da Madeira (RAM), como e por que se implementou o SIADAP-RAM na Direção Regional da Administração Educativa (DRAE), e, por fim, como tem sido utilizada a informação proveniente do SIADAP-RAM na DRAE e porquê. Com enquadramento na teoria institucional, o estudo de caso fez uma análise dos documentos legais e, com base nos resultados das entrevistas realizadas aos avaliadores e avaliados, concluiu-se que os avaliadores da DRAE não executam o processo de avaliação do desempenho, estabelecido por lei, de forma uniforme. O SIADAP surgiu em substituição do Sistema de Classificação de Serviço. A mudança surgiu por imposição legal, conforme com o fenómeno de isomorfismo coercivo a que se refere a literatura.
- Chemical characterization and antimicrobial activity of ozonized oil against methicillin resistant Staphylococcus aureusPublication . Silva, Vanessa; Peirone, Cecília; Amaral, Joana S.; Marques-Magallanes, José A.; Igrejas, Getúlio; Poeta, PatríciaMethicillin resistant Staphylococcus aureus (MRSA) are frequently found in infected skin wounds due to the exposure of deep tissues to the bacteria, in particular in infected diabetic foot ulcers in which the prevalence can be between 15 to 40% [1]. Clinical MRSA are usually resistant to most classes of antibiotics and, therefore, it is necessary to investigate new antimicrobial agents. Ozone has a recognized bactericidal activity and has been widely used as a clinical therapeutic agent for chronic wounds, such as, ulcers and other diabetic lesions, due to its wound healing ability [2]. This study aimed to characterize ozone oil suspensions and their activity against MRSA isolated from infected diabetic foot ulcers. Six ozonized oils with different ozonization doses were tested by disk diffusion method. The oils were prepared from a 50:50 mixture of extra virgin olive oil and refined sunflower oil and submitted to a gas stream of O2/O3 mixture at a concentration of 75 μg/ml of ozone in continuous flow (4 L/min). The oil content in fatty acid methyl esters after ozonization were investigated using a Bruker® SCION 436-GC gas chromatograph equipped with a flame ionization detector (GC-FID). All ozone suspension oils tested showed antimicrobial activity against all strains. The ozone suspension oil with the highest ozonization dose originated clear zones with a maximum of 12 mm. Composition of fatty acids in ozonized oils showed gradual decrease in unsaturated fatty acids with gradual increase in ozone doses. Overall, there was a decrease in the total fatty acid investigated and an increase in the content of unknown oxidized fatty acid with the increase of ozonization period. Our results indicate that ozonized oils have a significant antimicrobial activity, however, it is still unclear which compounds may be responsible for the bactericidal action.
- Chemical composition, antioxidant and antimicrobial activity of phenolic compounds extracted from wine industry by-productsPublication . Silva, Vanessa; Igrejas, Gilberto; Falco, Virgílio; Santos, Teresa P.; Torres, Carmen; Oliveira, Ana M.P.; Pereira, José Eduardo; Amaral, Joana S.; Poeta, PatríciaWinery by-products are a rich source of polyphenols, which have proven to have several beneficial biological properties, such as, antioxidant and antimicrobial activities. Therefore, this study aimed the extraction of polyphenols from winery by-products of two Portuguese red grape varieties, Touriga Nacional and Preto Martinho, and evaluate their phenolic profile, antioxidant properties and antimicrobial activity against antibiotic resistant bacteria. The polyphenols were extracted from the grapes' skins, seeds and stems. Extracts were analysed for total phenolic, anthocyanin and tannin contents, and the polyphenol profile was determined by High Performance Liquid Chromatography. The antioxidant activity of the extracts was determined by ABTS+ and DPPH methods. Antimicrobial susceptibility assay was performed using Kirby-Bauer disc diffusion method. Preto Martinho variety presented a higher polyphenolic content than Touriga Nacional. Malvidin 3-O-glucoside was the most abundant compound found in the skins extracts in both varieties. The main phenolic compound found in the seeds and stems extracts was catechin. From the several flavonols quantified, rutin was the most abundant. For both varieties, the seeds extracts showed the highest antioxidant and antimicrobial properties, followed by the stems extracts. The extracts showed antibacterial activity against all tested strains except on gram-negative bacteria Salmonella enteritidis, Escherichia coli and Pseudomonas aeruginosa. These results show that, natural products, such as polyphenols, may represent a source for the development of novel antimicrobials to combat gram-positive resistant bacteria and possibly be used as natural food preservatives. However, they were not effective against gram-negative resistant bacteria which shows that polyphenols, alone, might not substitute antibiotics.
- Comparative insight upon chitosan solution and chitosan nanoparticles application on the phenolic content, antioxidant and antimicrobial activities of individual grape components of Sousão varietyPublication . Silva, Vanessa; Singh, Rupesh Kumar; Gomes, Nelson; Soares, Bruno Gonçalves; Silva, Adriana; Falco, Virgílio; Capita, Rosa; Alonso-Calleja, Carlos; Pereira, José Eduardo; Amaral, Joana S.; Igrejas, Gilberto; Poeta, PatríciaChitosan, a natural polysaccharide, has been previously proposed as an elicitor in plants to prevent pathogen infections. The present study aimed to analyze the e ect of chitosan solution and chitosan nanoparticles treatment applied on the grapevine variety Sousão with respect to the phenolic composition, antioxidant potential and antibacterial activity of its individual grape components. Grapevine plants of selected lines were sprayed with chitosan solution and chitosan nanoparticles, and ethanolic extracts of stems, seeds and skins were prepared from grapevines treated and not treated with chitosan. Total phenolic, anthocyanin and tannin contents were studied, and the identification of the individual phenolic compounds was performed by HPLC-DAD. The antimicrobial susceptibility method was performed using the Kirby-Bauer disc di usion method against multidrug-resistant bacteria. Overall, there was small increase in the concentration of phenolic compounds, antioxidant and antimicrobial activities in grape components treated with chitosan solution. Seed extracts showed the highest antioxidant and antimicrobial activities. The studied individual components obtained from chitosan-treated grapevines could represent an added value due to the increased antioxidant and antibacterial potentials. The phenolic compounds found in components may be used in food and pharmaceutical industries as natural food preservers and antibiotic adjuvants.
- Effect of phenolic compounds extracted from chestnut (Castanea sativa Mill) industry by-products on antibiotic resistant bacteriaPublication . Silva, Vanessa; Igrejas, Gilberto; Falco, Virgílio; Amaral, Joana S.; Poeta, PatríciaIn the last years, antibiotic resistance has become a selious threat tohuman and animal health since a large number of microorganisms have developed resistance to the drugs commonly used.Several natural compounds have been gcttingincreased attention as alternatives to many drugs. Phenolic compounds are secondary metabolites which exhibit several properties, such as, antimicrobial. antioxidant, anti-inflammatory, antimutagentic and cardioprotective. Thus, this study aims to investigate the antibacterial properties of the iJhenolic compounds extracted from the chestnut (Castaneasativa Mill.) industry by-products !gains! antibiotic resistant bacteria.
- Evaluation of the phenolic profile of Castanea sativa mill. By-products and their antioxidant and antimicrobial activity against multiresistant bacteriaPublication . Silva, Vanessa; Falco, Virgílio; Dias, Maria Inês; Barros, Lillian; Silva, Adriana; Capita, Rosa; Alonso-Calleja, Carlos; Amaral, Joana S.; Igrejas, Gilberto; Ferreira, Isabel C.F.R.; Poeta, PatríciaThe chestnut industry generates a large amount of by-products. These agro-industrial wastes have been described as potential sources of phenolic compounds with high bioactive potential. Therefore, we aimed to extract the phenolic compounds from chestnut by-products and assess their antioxidant potential and evaluate their antimicrobial activity against multidrug resistant bacteria. The individual phenolic compounds in the ethanolic extracts of chestnut shell, inner shell, bur, and leaves were characterized by HPLC-DAD/electrospray ionization (ESI)-MS. The antioxidant properties were determined by DPPH and ABTS assays. The minimum inhibitory concentration (MIC) and the antimicrobial susceptibility was performed using the Kirby–Bauer disc di usion method against 10 bacterial strains. The major phenolic compounds identified in the extracts were trigalloyl-HHDP-glucose, gallic acid, quercetin, and myricetin glycoside derivatives. All chestnut by-products presented promising antioxidant activity in both assays, with leaf samples the ones presenting the highest antioxidant capacity. The inner shell’s extract was e ective against all Gram-positive and two Gram-negative bacteria; nevertheless, all extracts showed antibacterial activity. Staphylococcus epidermidis showed susceptibility to all extracts while none of the extracts was able to suppress the growth of Escherichia coli and Salmonella enteritidis. Chestnut by-products are a source of phenolic compounds with prominent antioxidant and antimicrobial activities. Nevertheless, further studies should be conducted to assess the correlation between phenolic compounds and the bioactivities obtained.
- High efficacy of ozonated oils on the removal of biofilms produced by methicillin-resistant staphylococcus aureus (MRSA) from infected diabetic foot ulcersPublication . Silva, Vanessa; Peirone, Cecília; Amaral, Joana S.; Capita, Rosa; Alonso-Calleja, Carlos; Marques-Magallanes, José A.; Martins, Ângela; Carvalho, Águeda; Maltez, Luís; Pereira, José Eduardo; Capelo, José Luís; Igrejas, Gilberto; Poeta, Patrícia© 2020 by the authors. Ozone has a high wound healing capacity and antibacterial properties and can be used as a complementary treatment in infections. Methicillin-resistant S. aureus (MRSA) is the most common pathogen found in infected diabetic foot ulcers. Most of MRSA are resistant to several classes of antibiotics and, therefore, there is a need for new, effective, and well-tolerated agents. Thus, we aimed evaluate the antimicrobial and antibiofilm potentials of ozonated vegetable oils against MRSA strains isolated from diabetic foot ulcers. Six ozonated oils were produced with concentrations of ozone ranging from 0.53 to 17 mg of ozone/g of oil. The peroxide values were determined for each oil. Ozonated oils content on fatty acid was determined by gas chromatography equipped with a flame ionization detector. The antimicrobial susceptibility testing was performed by the Kirby-Bauer disk diffusion method and the effect of ozonated oils on biofilm formation ability and on established biofilms was investigated. In general, the content in identified unsaturated fatty acid in oils decreased with the increase of ozonation time and, consequently, the peroxide value increased. Most bacterial strains were inhibited by ozonated oil at a concentration of 4.24 mg/g. Ozonated oils had moderate to high ability to remove adhered cells and showed a high capacity to eradicate 24 h old biofilms. Our results show promising use of ozonated oils on the treatment of infections, in particular those caused by multidrug-resistant MRSA strains.