Browsing by Issue Date, starting with "2019-09-20"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Effect of quorum sensing molecule farnesol on mixed biofilms of Candida anbicans and Staphylococcus aureusPublication . Gaálová, Barbora; Kapustová, Magdaléna; Jordão, Luísa; Dizová, Stanislava; Bujdáková, HelenaSignalling molecules are extensively studied in recent years because of their potential to control pathogens. Microorganisms naturally produce quorum sensing molecules (QS) as a tool for intra- and inter-species communication. Farnesol is synthesized as a by product of the ergosterol pathway of the yeast Candida albicans and in a concentration dependent maner blocks the morphological shift from the yeast to the hyphal form. The aim of this work was to study the effect of farnesol (30-300 microM) and the combination of farnesol with antibiotics (oxacillin, ciprofloxacin) on mixed biofilms formed by C. albicans/ S. aureus. For this purpose, clinical strains of S. aureus from blood cultures and central venous cathethers were collected. Overall, 8 MRSA and 3 MSSA were identified by PCR by detection of FemA, MecA genes. Strains were characterized according to selected virulence factors associated with resistance to antibiotics and disinfectants or biofilm formation (Nor, Qac genes coding for efflux pumps, Ica operon). The efficacy of farnesol to single and mixed biofilms was determined using different approaches, the total biomass stainning (crystal violet), metabolic activity meassuring (MTT test), colony forming units counting (CFU/ml) and microscopy (SEM). The concentration of 300 microMwas determined as the MIC50 of farnesol inhibiting mixed biofilm formation. This concentration did not show mutagenic potential according to the Ames test and was not cytotoxic for HeLa cell line. SEM definitely confirmed that farnesol inhibited hyphae of C. albicans that are a suitable substrate for adherence of staphilococci. Testing a combination of farnesol with oxacillin by E-test revealed an enhancing susceptibility of MRSA and MSSA to oxacillin. This effect was already observed and it can be associated with the inhibition of cell wall biosynthesis through the reduction of free C55 lipid carrier with subsequent retardation of murein monomer precursor transport across the cell membrane. We can conclude, that farnesol has multiple effects on mixed biofilms.
- Effect of Rocha pear peel extracts added to wheat and rye bread formulations on acrylamide reduction and sensory quality maintenancePublication . Morgado, Cátia; Bernardo, Patrícia; Henriques, Inês; Jesus, Susana; Rego, Andreia; Delgado, Inês; Coelho, Inês; Castanheira, Isabel; Félix, Nelson; Fernandes, António; Guerra, Manuela; Brandão, CarlosPear peels are seen as potentially valuable for their low-cost beneficial components content such as polyphenols. These may reveal acrylamide (AA) mitigation effect and thus their application in a susceptible food matrix, such as bread, should be considered. Aiming to assess the AA reduction potential of Rocha pear peels in bread and the effects on its sensory quality, two types of bread highly consumed in Portugal - wheat (WB) and rye (RB) – were assayed with the extract of these by-products, in two forms aqueous [a] and dry [d]. Eight bread batches were produced (4 WB; 4 RB); each composed of one control sample and five replicates added with extract. The process included controlled fermentation, and cooking in a traditional oven (TO) and convection oven (CO). Hedonic evaluation was made to samples of each batch. Overall, slight differences were observed for WB and RB hedonic evaluation between the control sample and those with both extract forms. Lower scores were observed in both bread types baked in CO, with [d] comparing with the control; for bread with [a], oven influence varied; higher scores for WB in CO and for RB baked in TO, comparing with the control. Regarding AA reduction, the highest mitigation rate was accomplished by the [d] in WB cooked in a CO, 27.3%. However, for RB the best formulation was obtained with [d] in the TO, 19.2%. These results support the importance of selecting the best baking process according to the varieties of bread and AA reduction.
- Exploring a link between healthcare associated infections, biofilms and antimicrobial resistancePublication . Bandeira, Maria; Borges, Vítor; Nascimento, Maria; Duarte, Aida; Gomes, Joao Paulo; Jordão, LuísaHAIs are a major public health problem affecting 4 million patients per year in Europe. Here we present results of a retrospective study in wich the ability of K. pneumoniae isolates (collected during a period of 31 years) to assemble biofilms was evaluated; and an ongoing study of multispecies biofilms. In the first study, we found major differences in biofilm assembly kinetics, extracellular polymeric substances (EPS) content, which were further corroborated by in-depth EPS composition analysis. WGS analysis revealed a high nucleotide similarity within the core-genome, but relevant differences in the accessory genome that may account for the detected biofilm phenotypic dissimilarities, such as genes already associated with biofilm formation in other pathogenic bacteria (e.g., genes coding haemogglutinins and haemolysins). These data reinforce that the research efforts to defeat bacterial biofilms should take into account that their dynamics may be contingent on the medical devices-associated materials. The second study is ongoing and we aim at understanding the basis of multispecies biofilm assembly on different surfaces. Bacterial and fungi isolates have been used as models and until now all results suggest that the two microorganisms play different roles on biofilm onset.