Browsing by Author "Carvalho, Patrícia"
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- Bacterial biofilms, antibiotic resistance and healthcare-associated infections: a dangerous connectionPublication . Bandeira, Maria; Carvalho, Patrícia; Duarte, Aida; Jordão, LuísaIn 2012, were estimated 6.7 million cases of healthcare-associated infections (HAI) either in long-term care facilities or acute-care hospitals from which result 37,000 deaths configuring a serious public health problem [1]. The etiological agents are diverse and often resistant to antimicrobial agents. One of the mechanisms responsible for the emergence of drug resistance is biofilm assembly. Biofilms are defined as thin layers of microorganisms adhering to the surface of a structure, which may be organic or inorganic, together with the polymers that they secrete [2]. They are dynamic structures which experience different stages of organization with the ageing and are linked to an increase in bacterial resistance to host defense mechanisms, antibiotics, sterilization procedures other than autoclaving, persistence in water distribution systems and other surfaces. The understanding of bacteria organization within the biofilm and the identification of differences between planktonic and sessile forms of bacteria will be a step forward to fight HAIs. Bacterial isolates were grown in adequate medium. Antibiotic susceptibility was evaluated by broth microdilution method and interpreted according to NCCLS guidelines. A similar assay was performed to evaluate biofilm susceptibility to antibiotics. Bacteria ability to assemble biofilms was assayed by the microtiter-plate test [3] being tested in both abiotic (materials present in healthcare units) and biotic (Hella cells) surfaces. The biofilm structure was assessed by scanning electron microscopy (SEM) in either backscattered electron diffraction or secondary electrons mode. The kinetic of biofilm assembly depends on bacteria growth rate, incubation temperature and medium. Furthermore, the SEM analysis of planktonic and sessile forms of the same bacteria allowed the identification of structural differences which may be involved in virulence (Fig. 1). Bacteria ability to assemble biofilms seems to be independent of the abiotic structure (Fig.2). The same is not observed in biotic surfaces. This fact suggests that biofilm assembly in vivo is dependent of bacteria tropism. The minimum inhibitory concentration (MIC) determine for bacteria organized in biofilms is higher than for their planktonic forms. The increase ranges from 2 to 200 folds and is proportional to the ability of bacteria to assemble biofilms. Further studies will be conducted in order to prevent biofilm assembly within healthcare units which will result in a decrease of HAI and emergence of antibiotic resistant bacteria.
- Effect on Broiler Production Performance and Meat Quality of Feeding Ulva lactuca Supplemented with CarbohydrasesPublication . Costa, Mónica M.; Pestana, José M.; Carvalho, Patrícia; Alfaia, Cristina M.; Martins, Cátia F.; Carvalho, Daniela; Mourato, Miguel; Gueifão, Sandra; Delgado, Inês; Coelho, Inês; Lemos, José P.C.; Lordelo, Madalena M.; Prates, José A.M.SIMPLE SUMMARY: Macroalgae have been increasingly exploited worldwide for feed, food and biofuel applications, due to their nutritive and bioactive compounds. Green seaweeds belonging to the genus Ulva have high growth rates, which makes them suitable for being cultured in sustainable algae production, such as an integrated multi-trophic aquaculture system. This is expected to increase the use of Ulva sp. as an alternative source to conventional feedstuffs (e.g., cereals and soybean meal) for poultry. The objective of the current study was to assess if the incorporation of 15% Ulva lactuca in broiler chickens’ diet, combined or not with carbohydrate-active enzymes, would enhance meat nutritional quality without compromising animal growth performance. Overall, U. lactuca led to an accumulation of antioxidant carotenoids, n-3 PUFA and macrominerals, including magnesium, potassium and phosphorus, in the breast muscle, with likely health benefits, without significantly impairing growth performance. The supplementation of macroalgae with a recombinant ulvan lyase reduced ileal viscosity with possible beneficial effects on broiler digestibility. Although dietary U. lactuca showed potential to increase meat quality, it reduced meat overall acceptability, which suggests the use of a lower algae inclusion level to prevent a negative meat sensory perception for consumers.
- Exploitation of a link between antibacterial agent-resistance and biofilm-formation by classical and emergent pathogensPublication . João, Inês; Reis, Lúcia; Carvalho, Patrícia; Duarte, Aida; Jordão, LuísaObjectives: In recent years nosocomial infections have gained growing importance. Among their etiological agents are “classical” pathogens such as S.aureus and also emergent pathogens, previously neglected, such as nontuberculous mycobacteria (MTM). The ability to resist to antibacterial agents, such as antibiotics and disinfectants, is shared by all of them. Here we aim to establish a link between bacterial virulence, antibacterial agents’ resistance and biofilm formation. Methods: Bacterial reference strains and clinical isolates were grown in adequate medium. Among the “classical” pathogens used are E.coli, K. pneumoniae, S. aureus and P. aeroginosa. The group of emergent pathogens includes M.fortuitum, M.abcessus, M.chelonae, M.avium etc. NTM susceptibility test to antibiotics was evaluated by broth based microdilution method and interpreted according to NCCLS guidelines. The desinfectant (oxygen peroxide, ammonium quaternary salts [AQS] and glutaraldehyde [GA) efficacy was performed according to the approved guidelines. The susceptibility was performed by two different methods: broth microdilution and diffusion in solid medium. In order to evaluate the effect of these agents in bacteria a scanning electron microscopy (SEM) study was performed. Biofilm forming ability was evaluated by the microtiter-plate test. The assay was performed at 25ºC and 37ºC in optimal growth media, phosphate saline buffer pH 7.4 and water during for different periods of time. Fast growing bacteria were assayed for 3 days while slow growers were assayed for 15 days.
- Exploring a link between pathogens structure's and resistance to disinfectantPublication . João, Inês; Reis, Lúcia; Carvalho, Patrícia; Duarte, Aida; Jordão, LuísaIn recent years healthcare-associated infections (HAIs) infections have gained growing importance. Among their etiological agents are classical (e.g. K. pneumoniae, S. aureus) and emergent pathogens, previously neglected, such as nontuberculous mycobacteria (NTM). The ability to resist to antibacterial agents, such as antibiotics and disinfectants, is shared by all of them. Here we aim to establish a link between bacterial virulence, disinfectant resistance and structure. Bacterial reference strains and clinical isolates were grown in adequate medium. NTM susceptibility test to antibiotics was evaluated by broth microdilution method and interpreted according to NCCLS guidelines in a previous work. The susceptibility to disinfectants (hydrogen peroxide, ammonium quaternary salts [AQS] and glutaraldehyde [GA]) was performed by two different methods: broth microdilution and diffusion in solid medium. In order to evaluate the effect of these agents in bacteria a scanning electron microscopy (SEM) study was performed. Hydrogen peroxide was the less effective disinfectant. The efficiencies of QAS and GA were similar. Nevertheless, among NTM we identified one isolate resistant to all disinfectants tested (Table 1). The SEM analysis showed that different disinfectants caused different effects on bacteria suggesting different action mechanisms (Figure 1). Bacterial resistance to antibiotics and disinfectants vary in the same manner. The mechanisms involved in the resistance are not fully elucidated and more studies are needed to provide effective conclusions. Biofilm formation can be part of the mechanism involved both in antibiotic/disinfectant resistance development and infection propagation.
- Influence of Feeding Weaned Piglets with Laminaria digitata on the Quality and Nutritional Value of MeatPublication . Ribeiro, David; Alfaia, Cristina; Pestana, José; Carvalho, Daniela; Costa, Mónica; Martins, Cátia; Lemos, José; Mourato, Miguel; Gueifão, Sandra; Delgado, Inês; Carvalho, Patrícia; Coelho, Diogo; Coelho, Inês; Freire, João; Almeida, André; Prates, JoséLaminaria digitata is a novel feedstuff that can be used in pig diets to replace conventional feedstuffs. However, its resilient cell wall can prevent the monogastric digestive system from accessing intracellular nutrients. Carbohydrate-active enzyme (CAZyme) supplementation is a putative solution for this problem, degrading the cell wall during digestion. The objective of this work was to evaluate the effect of 10% L. digitata feed inclusion and CAZyme supplementation on the meat quality and nutritional value of weaned piglets. Forty weaned piglets were randomly allocated to four experimental groups (n = 10): control, LA (10% L. digitata, replacing the control diet), LAR (LA + CAZyme (0.005% Rovabio® Excel AP)) and LAL (LA + CAZyme (0.01% alginate lyase)) and the trial lasted for two weeks. The diets had no effect on any zootechnical parameters measured (p > 0.05) and meat quality traits, except for the pH measured 24 h post-mortem, which was higher in LAL compared to LA (p = 0.016). Piglets fed with seaweed had a significantly lower n-6/n-3 PUFA ratio compared to control, to which the higher accumulation of C20:5n-3 (p = 0.001) and C18:4n-3 (p < 0.0001) contributed. In addition, meat of seaweed-fed piglets was enriched with bromine (Br, p < 0.001) and iodine (I, p < 0.001) and depicted a higher oxidative stability. This study demonstrates that the nutritional value of piglets’ meat could be improved by the dietary incorporation of L. digitata, regardless of CAZyme supplementation, without negatively affecting growth performance in the post-weaning stage.