3D morphological features and antibiotic resistance in L. monocytogenes - Pseudomonas sp. biofilms

1 poster presented at Biofilms 7, Porto, 26-28 June 2016This research was financially supported by the Spanish Research Council (Project ref.201670 E008)N

Potential of bacteriophage K as an antimicrobial strategy against biofilms of Staphylococcus aureus in the food industry

1 poster presented at the 24th International ICFMH Conference, Food Micro 2014, 1-4 Septembre, Nantes, FranceThe potential of phage K in the removal and prevention of Staphylococcus aureus biofilms on stainless steel surfaces was examined. The host range of the phage was tested on 18 strains from the food industry. Two out of six sensitive strains were selected for study of biofilms. Immature 6-h-old biofilms were challenged wfth a wide range of multipticlties of infection {MOl, 0.01-500) for 18 h at 25ºc. A noticeable effect on cell number was appreciated at MOIs≥10, but no effect was detected at lower MOis. Subsequently, 24 h-old biofilms (with a higher cell density and a more dense extracellular matrix) were challenged too at MOIs between 0.01-3.0 for 24 hat 25ºc. Again, a significant effect was only found at MOls > 1. The effectiveness in the prevention of biofilm formation was examined by Infecting planktonlc cultures of S. aureus with sub-lethal and lethal doses of phage K (MOIs 1-10-7-10.0). A notable effect on cell number and biofilm biomass was observed from MOIs >1·10-5. The potential of phage K as a tool for biohygienization in the food Industry acting specifically against biofilms of S. aureus was thus shown. However, neither biofilm cells were completely removed nor biofilm formation was totally prevented, and a sub-population of live cells was left In both cases As a result, the effectiveness of two co-adjuvant-based strategies was subsequently assessed. Combining DNase (0,1-10 mg/ml) with phage K (MOl of 0.3-3.0) did not show an additional effect on the removal of 24 h-old-biofilms at 25°C. A 30 min pre-treatment at 37ºc aimed to enhance DNase activity also had not effect. DNase did not show any effects by itself either. In contrast, combining cis-2-decenoic acid {1 - 100 nM) with phage K (MOl of 0.03-0.3) seemed to show some effects on biofilmsN

Assessment of tolerance development in L. monocytogenes – E. coli dual – species biofilms to Pronase and Benzalkonium chloride treatments

1 poster presented at VI International Conference on Environmental, Industrial and Applied Microbiology, Barcelona, 28-30 October 2015This research was financially supported by the Spanish Ministerio de Economía y Competitividad (ENZYMONO, AGL2010-22212-C02-02). P. Rodríguez-López acknowledges the financial support from the FPI-MICINN programme (Grant number: BES-2011-050544).N

Efficiency of enzymes and benzalkonium chloride treatments against Listeria monocytogenes dual-species blofllms determined by fluorescence mlcroscopy and image analysis

1 poster presented at the 24th International ICFMH Conference, Food Micro 2014, 1-4 Septembre, Nantes, FranceIn the present study, three different mixed·species Listeria monocytogenes-carrying blofilms previously isolated from surfaces of seafood, meat and dairies Industrial environments were selected in order to test the efficiency of cleanlng and disinfection procedures based on the combination of an enzymatic solution, followed by a treatment with benzalkonium chloride (BAC). Biofilm samples were cultured onto AISI-316 type stainless steel 1 cm2 coupons In a batch system at 25° C. The effect of sequential exposure to different concentrations of Pronase- BAC, Cellulase - BAC or DNAsel - BAC solutions was then assessed in mature biofilms after 168 hours using an orthogonal first order experimental design. Samples were stained using FilmTracerTM LIVE/DEAD Blofllm viability kit (lnvitrogen} and the efficiency of each treatment was then determined by epifluorescence mlcroscopy and subsequent image anatysls of 25·field mosaics representing a total surface of 1.92 mm2, so as to quantify the total area occupied by living and damaged cells attached to the surface. Significant empirical equations obtained reveals that synergistic effects between Pronase - BAC on biofilms coming from flsh and dairy industries obtaining almost a total cell detachment in the latter case. No significant effect was observed among the Cellulase - BAC procedures in the experimental DNAse - BAC against biofilms coming from fish and dairy industries compared with the other two combinations enzyme- benzalkoniom chloride was also demonstrated even with no effect against the consortium isolated from meat industry These results show how the usage of customised treatments combining commerclally available enzymes with classical chemlcally-based disinfection procedures may represent an attractive and efficient alternative against bacterial blofilms present in the food IndustryThis research was financially supported by the Spanish Ministerio de Economía y Competitividad (ENZYMONO, AGL2010-22212-C02-12). P. Rodríguez-López acknowledges the financial support from the FPI-MICINN programme (Grant number BES-2011-060544)N

Survival of lactic acid bacteria in sea water. A factorial study

6 páginas, 3 figuras, 4 tablas.-- The final publication is available at www.springerlink.comA feasibility study of lactic bacteria as potential probiotics in larval cultures of marine fish was performed by investigating the survival of five strains of lactic bacteria in seawater by readily standardized procedures at different temperatures and salinities. These conditions were chosen in such a way that their combinations define a complete first-order factorial design. Depending on the strain and the ambient conditions, the survival adhered to first-order kinetics in some cases, and to the Gompertz equation in others. The half lives (t0.5) calculated from these models were subsequently introduced as responses to the factorial designs, estimating the coefficients of empirical equations that describe the group effect of temperature and salinity on t0.5. Simply additive effects were found in two cases, a negative first-order interaction in another case, while another two required second-order models.Xunta de Galicia (Project PGIDT99MAR40203)Peer reviewe

Combination of mechanism-based and data-based models for the prediction of quality in fresh fish

[Resumen] El desperdicio alimentario supone un gran problema de sostenibilidad. El pescado, en concreto, es un producto especialmente perecedero, degradándose con mucha rapidez cuando la temperatura de almacenamiento no se controla adecuadamente. Los modelos matemáticos son herramientas útiles para predecir la evolución de la calidad del pescado durante el transporte y almacenamiento. Conocer la dinámica de la degradación con antelación también nos permitirá definir estrategias para reducir el desperdicio alimentario y aumentar el valor añadido del pescado. En este trabajo se presenta una nueva metodología para la descripción de la evolución de calidad de filetes de merluza (Merluccius merluccius) envasada en atmósferas modificadas durante el transporte y almacenamiento. Dicha metodología consta de dos partes: un modelo basado en los mecanismos del proceso que describe la evolución de dos de los indicadores de calidad más utilizados (contenido bacteriano y bases volátiles), y un modelo de aprendizaje automático que permite correlacionar dichos indicadores con un indicador sensorial, el QIM (del inglés, Quality Index Method). Para la evolución de las bases volátiles se propone un nuevo modelo basado en la ley de potencias. Además, en este trabajo, los parámetros desconocidos del modelo se estiman utilizando datos experimentales. En el caso de los modelos de aprendizaje automático, se comparan técnicas de redes neuronales y árboles de decisión utilizando diferentes indicadores del error. El modelo combinado supone un avance en la predicción de calidad, ya que permite predecir el QIM a partir, exclusivamente, de datos de temperatura y obtener resultados satisfactorios.[Abstract] Food waste is a significant sustainability problem. Fish, in particular, is a very perishable product. In fact, spoilage increases rapidly when the storage temperature is not adequately controlled. Mathematical models are useful tools to predict fish quality evolution during transport and storage. This knowledge will help to develop strategies to reduce food waste and to increase the product value. In this work, we propose a new methodology to predict the evolution of quality, during transport and storage, of hake fillets packed in modified atmospheres. It consists of two parts: a model based on the process mechanisms to describe the evolution of two highly used quality indicators (bacterial content and volatile bases), and a machine learning model to correlate such indicators with one of the most employed sensory indexes: the Quality Index Method (QIM). Moreover, we propose a Power Law model to describe volatile bases evolution. We estimate the unknown parameters using experimental data. In the machine learning part, we compare random forest models and neural networks using several statistical techniques. Overall, this methodology is an improvement in fish quality prediction because it makes QIM prediction using just temperature data with promising results.Ministerio de Agricultura, Pesca y Alimentación; 202178002Ministerio de Ciencia e Innovación; PRTRC17.I

Identification of emerging hazards in mussels by the Galician Emerging Food Safety Risks Network (RISEGAL). A first approach

Emerging risk identification is a priority for the European Food Safety Authority (EFSA). The goal of the Galician Emerging Food Safety Risks Network (RISEGAL) is the identification of emerging risks in foods produced and commercialized in Galicia (northwest Spain) in order to propose prevention plans and mitigation strategies. In this work, RISEGAL applied a systematic approach for the identification of emerging food safety risks potentially affecting bivalve shellfish. First, a comprehensive review of scientific databases was carried out to identify hazards most quoted as emerging in bivalves in the period 2016–2018. Then, identified hazards were semiquantitatively assessed by a panel of food safety experts, who scored them accordingly with the five evaluation criteria proposed by EFSA: novelty, soundness, imminence, scale, and severity. Scores determined that perfluorinated compounds, antimicrobial resistance, Vibrio parahaemolyticus, hepatitis E virus (HEV), and antimicrobial residues are the emerging hazards that are considered most imminent and severe and that could cause safety problems of the highest scale in the bivalve value chain by the majority of the experts consulted (75%). Finally, in a preliminary way, an exploratory study carried out in the Galician Rías highlighted the presence of HEV in mussels cultivated in class B production areas.info:eu-repo/semantics/publishedVersio

Interlaboratory validation of a multiplex qPCR method for the detection of listeria monocytogenes in a ready-to-eat seafood product

Listeria monocytogenes is a major foodborne pathogen which mainly infects susceptible individuals through the consumption of contaminated foods. To this end, ready-to-eat (RTE) food products are of particular concern as this microorganism is widely distributed, can survive, and even grow, under adverse conditions, and thus must be carefully controlled. In the present study, an interlaboratory ring trial was organized to evaluate an open formula qPCR-based method for the detection of L. monocytogenes. The molecular method was evaluated on a novel RTE seafood product, developed in the framework of a European project, the SEAFOODAGE (EAPA_758/2018). Six laboratories located in Spain and Portugal participated in the study, and the results obtained indicated that this new method presented high diagnostic sensitivity (100%) reaching a low limit of detection (<10CFU/25 g) with an overall agreement with the reference method, attending to the Cohen's k, of 0.97 that is interpreted as almost complete agreement.info:eu-repo/semantics/publishedVersio

Synthesis of compositionally graded nanocast NiO/NiCo2O4/Co3O4 mesoporous composites with tuneable magnetic properties

A series of mesoporous NiO/NiCo2O4/Co3O4 composites has been synthesized by nanocasting using SBA-15 silica as a hard template. The evaporation method was used as the impregnation step. Nickel and cobalt nitrates in different Ni(II) : Co(II) molar ratios were dissolved in ethanol and used as precursors. The composites show variable degrees of order, from randomly organized nanorods to highly ordered hexagonally-packed nanowires as the Ni(II) : Co(II) molar ratio decreases. The materials exhibit moderately large surface areas in the 60-80 m2 g−1 range. Their magnetic properties, saturation magnetization (MS) and coercivity (HC), can be easily tuned given the ferrimagnetic (NiCo2O4) and antiferromagnetic (NiO and Co3O4) character of the constituents. Moreover, the NiCo2O4 rich materials are magnetic at room temperature and consequently can be easily manipulated by small magnets. Owing to their appealing combination of properties, the nanocomposites are expected to be attractive for myriad applications

EEL spectroscopic tomography: Towards a new dimension in nanomaterials analysis

Electron tomography is a widely spread technique for recovering the three dimensional (3D) shape of nanostructured materials. Using a spectroscopic signal to achieve a reconstruction adds a fourth chemical dimension to the 3D structure. Up to date, energy filtering of the images in the transmission electron microscope (EFTEM) is the usual spectroscopic method even if most of the information in the spectrum is lost. Unlike EFTEM tomography, the use of electron energy-loss spectroscopy (EELS) spectrum images (SI) for tomographic reconstruction retains all chemical information, and the possibilities of this new approach still remain to be fully exploited. In this article we prove the feasibility of EEL spectroscopic tomography at low voltages (80kV) and short acquisition times from data acquired using an aberration corrected instrument and data treatment by Multivariate Analysis (MVA), applied to FexCo(3-x)O4@Co3O4 mesoporous materials. This approach provides a new scope into materials; the recovery of full EELS signal in 3D