Strategic Project - LA 16 - 2011-2012

Funder

Organizational Unit

Publications

Listeria monocytogenes persistence in food associated environments: epidemiology, strain characteristics, and implications for public health

Publication . Ferreira, V.; Wiedmann, M.; Teixeira, P.; Stasiewicz, M. J.

Over the last 10 to 15 years, increasing evidence suggests that persistence of Listeria monocytogenes in food processing plants for years or even decades is an important factor in the transmission of this foodborne pathogen and the root cause of a number of human listeriosis outbreaks. L. monocytogenes persistence in other food-associated environments (e.g., farms and retail establishments) may also contribute to food contamination and transmission of the pathogen to humans. Although L. monocytogenes persistence is typically identified through isolation of a specific molecular subtype from samples collected in a given environment over time, formal (statistical) criteria for identification of persistence are undefined. Environmental factors (e.g., facilities and equipment that are difficult to clean) have been identified as key contributors to persistence; however, the mechanisms are less well understood. Although some researchers have reported that persistent strains possess specific characteristics that may facilitate persistence (e.g., biofilm formation and better adaptation to stress conditions), other researchers have not found significant differences between persistent and nonpersistent strains in the phenotypic characteristics that might facilitate persistence. This review includes a discussion of our current knowledge concerning some key issues associated with the persistence of L. monocytogenes, with special focus on (i) persistence in food processing plants and other food-associated environments, (ii) persistence in the general environment, (iii) phenotypic and genetic characteristics of persistent strains, (iv) niches, and (v) public health and economic implications of persistence. Although the available data clearly indicate that L. monocytogenes persistence at various stages of the food chain contributes to contamination of finished products, continued efforts to quantitatively integrate data on L. monocytogenes persistence (e.g., meta-analysis or quantitative microbial risk assessment) will be needed to advance our understanding of persistence of this pathogen and its economic and public health impacts.

2014Journal article

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Bacterial community dynamics in a rotating biological contactor treating 2‑fluorophenol‑containing wastewater

Publication . Duque, Anouk F.; Bessa, Vânia S.; Castro, Paula M. L.

One of the main factors affecting the performance of rotating biological contactors (RBC) is the biofilm characteristics. Therefore, a deep understanding of the microbial population dynamics and structure of the biofilm is mandatory if optimization of organic matter and nutrients removal is targeted. This study focused on the effects of organic shock loads of 2-fluorophenol (2-FP) on the microbial diversity present in an RBC biofilm. The RBC was seeded with activated sludge from a conventional wastewater treatment plant and was operated during 496 days. During the first 126 days, the RBC was subjected to intermittent 2-FP shocks of 25 mg l(-1) and no degradation occurred. Therefore, the reactor was subsequently augmented with a 2-FP-degrading strain (FP1). Afterwards, the RBC had a stable performance when subjected to 2-FP shocks up to 50 mg l(-1) and to a starvation period, as indicated by removal of the compound. Denaturing gradient gel electrophoresis (DGGE) revealed large shifts in microbial communities present in the first and fifth stages, although no clear relation between the sample collection time and spatial factor was found. Phylogenetic affiliation of some predominant members was assessed by direct sequencing of correspondent DGGE bands. Affiliations to alpha-, beta- and delta-Proteobacteria were found. Several bacterial strains isolated from the reactor showed capacity for 2-FP degradation. Strain FP1 was successfully recovered from the biofilm by plating and by DGGE, reinforcing that bioaugmentation was successfully achieved.

2014Journal article

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Enantioselective HPLC analysis and biodegradation of atenolol, metoprolol and fluoxetine

Publication . Ribeiro, Ana R.; Afonso, Carlos M.; Castro, Paula M. L.; Tiritan, Maria E.

The accurate quantification of enantiomers is crucial for assessing the biodegradation of chiral pharmaceuticals in the environment. Methods to quantify enantiomers in environmental matrices are scarce. Here, we used an enantioselective method, high-performance liquid chromatography with fluorescence detection (HPLC-FD), to analyze two beta-blockers, metoprolol and atenolol, and the antidepressant fluoxetine in an activated sludge consortium from a wastewater treatment plant. The vancomycin-based chiral stationary phase was used under polar ionic mode to achieve the enantioseparation of target chiral pharmaceuticals in a single chromatographic run. The method was successfully validated over a concentration range of 20–800 ng/mL for each enantiomer of both beta-blockers and of 50–800 ng/mL for fluoxetine enantiomers. The limits of detection were between 5 and 20 ng/mL and the limits of quantification were between 20 and 50 ng/mL, for all enantiomers. The intra- and inter-batch precision was lower than 5.66 and 8.37 %, respectively. Accuracy values were between 103.03 and 117.92 %, and recovery rates were in the range of 88.48–116.62 %. Furthermore, the enantioselective biodegradation of atenolol, metoprolol and fluoxetine was followed during 15 days. The (S)-enantiomeric form of metoprolol was degraded at higher extents, whereas the degradation of atenolol and fluoxetine did not show enantioselectivity under the applied conditions.

2013Journal article

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A hydroxyapatite–Fe2O3 based material of natural origin as an active sunscreen filter

Publication . Piccirillo, C.; Rocha, C.; Tobaldi, D. M.; Pullar, R. C.; Labrincha, J. A.; Ferreira, M. O.; Castro, Paula M. L.; Pintado, M. E.

The use of sunscreens as protective barriers against skin damage and cancer, by absorbing harmful UVA and UVB rays, is becoming an increasingly important issue. Such products are usually based on TiO2 or ZnO, although both Fe2O3 and hydroxyapatite (Ca10(PO4)6(OH)2, HAp) doped with metal ions have been reported as being ultraviolet (UV) absorbing materials. HAp is the main component of bone; it is, therefore, highly biocompatible. In the present work, an iron-doped HAp-based material, containing both Fe ions substituted into the HAp structure and iron oxide in hematite (a-Fe2O3) form, was successfully developed from waste cod fish bones. This was achieved through a simple process of treating the bones in a Fe(II) containing solution, followed by heating at 700 C. The material showed good absorption in the whole UV range and did not form radicals when irradiated. The sunscreen cream formulated with this material could be used as a broad sunscreen protector (lcrit > 370 nm), showing high absorption both in the UVA and UVB ranges. Because of its absorption properties it would be classified as 5 star protection according to the Boots UVA star rating system. The cream is also photostable, and does not cause irritation or erythema formation when in contact with the human skin. These results show that a food by-product such as fish bones could be converted into a valuable product, with potential applications in health care and cosmetics. This is the first time a HAp-based sunscreen cream has been developed and validated as a proof of concept.

2014Journal article

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Effects of physical parameters onto adsorption of the Borderline Amino Acids Glycine, Lysine, Taurine, and Tryptophan upon Amberlite XAD16 Resin

Publication . Ferraro, Vicenza; Cruz, Isabel B.; Jorge, Ruben Ferreira; Pintado, Manuela E.; Castro, Paula M. L.

The adsorption of the borderline amino acids glycine, lysine, taurine, and tryptophan on the commercial resin Amberlite XAD16 was investigated. The effect of amino acid hydrophobicity/hydrophilicity and effects of environmental conditions upon adsorption equilibrium were evaluated. Optimal settings for a maximum recovery of a selected amino acid, namely, taurine, were obtained by the response surface methodology. Changes in temperature, pH, ionic strength, percentage of ethanol added to the amino acid solution, amino acid concentration, and adsorbent dose showed effects on the recovery of each amino acid upon the uncharged, nonfunctionalized, and hydrophobic matrix of the Amberlite XAD16 resin. Adsorption was favored at the lower temperature investigated, 10 degrees C; a pH decrease down to 2 favored adsorption of glycine, lysine, and tryptophan; the addition of ethanol allowed an increase in amino acid recovery except for lysine. The addition of sodium chloride up to the value of 1.5 M showed a positive effect on adsorption of all amino acids. A dose of 10 g Amberlite XAD16 for 100 mL of solution was the most adequate at the amino acid concentrations tested. Optimal conditions for the maximum recovery of taurine were achieved at a temperature of 13.5 degrees C and at a ionic strength of 1.32 M NaCl.

2013Journal article

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