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Acord transformatiu CRUE-CSIC, The aims of this study were, first, to determine Listeria monocytogenes, Salmonella enterica, ser. Typhimurium, and Staphylococcus aureus biofilm counts, structure, and their composition in macromolecules by direct epifluorescence microscopy (DEM); and second, to evaluate the distribution of the components of the produced biofilms through 3D representations obtained by confocal laser scanning microscopy (CLSM). Results showed that all assessed strains have a high capacity to generate biofilms, with counts greater than 7 log CFU cm⁻ in all cases. The highest and lowest survival percentages were obtained by S. aureus with 94.13 ± 1.77% and S. Typhimurium with 60.31 ± 4.45%, respectively. Biofilm matrix composition in macromolecules was as follows: (a) L. monocytogenes: proteins 83.35 ± 5.81%, polysaccharides 10.98 ± 5.77%, and extracellular DNA 5.67 ± 2.5%; (b) S. Typhimurium: 83.37 ± 3.35%, 0.68 ± 0.77%, and 15.95 ± 3.39%, respectively; and (c) S. aureus: 82.55 ± 2.39%, 8.48 ± 2.07%, and 8.97 ± 2.27%, respectively. The qualitative analysis of the 3D representations of the biofilms formed by the pathogens modelized showed no homogeneity and/or ordered distribution of their components within the biofilm architecture. These findings could lead to the development of addressed cleaning and disinfection alternatives.

Altres ajuts: Acord transformatiu CRUE-CSIC, Conventional cleaning with chemical products uses a substantial amount of water and energy to clean the fouling related to dairy production, resulting in significant economic costs. We evaluated an enzymatic treatment based on the use of protease and amylase to clean dairy fouling generated in an indirect plate heat exchanger and the spray dryer equipment of a pilot plant, representing real cleaning conditions in the dairy industry. The efficacy of the enzymatic treatment in removing fouling at 50 °C was comparable to that of the clean-in-place method, with alkaline-acid cleaning performed at a maximum temperature of 80 °C. Microbiological analysis showed that the cleaning treatments guaranteed adequate hygienic conditions of the dairy products manufactured. Monitoring fluorescence markers, such as tryptophan, riboflavin, Maillard compounds, and dityrosine could help improve the effectiveness of both alkaline and enzymatic cleaning. The enzymatic treatment fulfills dairy industry objectives, saving water and energy during washing by reducing chemical product use. Considering that enzymatic cleaning is biodegradable after use and that its economic cost is competitive compared to chemical cleaning, it represents a viable alternative to the chemical cleaning of dairy fouling.

Acord transformatiu CRUE-CSIC, Alternatives to combat the persistence of pathogens need to consider the microbiota established on industrial surfaces as they can influence the protection or replacement (i.e. reduction/inhibition) of pathogens. The objective of the present study was to determine the ecological interactions established in dual-species biofilms between Listeria monocytogenes and Salmonella enterica as target pathogens, and isolates recovered from a meat processing facility (i.e. Pseudomonas fluorescens, Pseudomonas fragi, Bacillus safensis, Bacillus megaterium, and Candida zeylanoides). Results showed different ecological relations in biofilms depending on the species evaluated. Pseudomonas spp. did not influence the growth of either pathogen, although tested species tended to protect the pathogens in the structures generated. B. megaterium and C. zeylanoides affected the two pathogens differently, demonstrating a reduction of L. monocytogenes adhered cells within the formed biofilm. B. safensis reduced or presented non-influence on S. enterica depending on the incubation conditions. Contrarily, B. safensis was the microorganism that demonstrated the highest replacement capacity for L. monocytogenes, reducing its growth by up to 4 log CFU/cm2. The in vitro study of bispecies biofilms is important for the food industry, helping to understand how they behave and to find an effective way to eliminate them.

Food contact surfaces are primary sources of bacterial contamination in food industry processes. With the objective of preventing bacterial adhesion and biofilm formation on surfaces, this study evaluated the antimicrobial activity of silver (Ag-NPs) and zinc oxide (ZnO-NPs) nanoparticle-containing polyester surfaces (concentration range from 400 ppm to 850 ppm) using two kinds of bacteria, Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli), and the prevention of bacterial biofilm formation using the pathogen Listeria monocytogenes. The results of antimicrobial efficacy (reductions ≥ 2 log CFU/cm 2) showed that at a concentration of 850 ppm, ZnO-NPs were effective against only E. coli (2.07 log CFU/cm 2). However, a concentration of 400 ppm of Ag-NPs was effective against E. coli (4.90 log CFU/cm 2) and S. aureus (3.84 log CFU/cm 2). Furthermore, a combined concentration of 850 ppm Ag-NPs and 400 ppm ZnO-NPs showed high antimicrobial efficacy against E. coli (5.80 log CFU/cm 2) and S. aureus (4.11 log CFU/cm 2). The results also showed a high correlation between concentration levels and the bacterial activity of Ag-ZnO-NPs (R 2 = 0.97 for S. aureus, and R 2 = 0.99 for E. coli). They also showed that unlike individual action, the joint action of Ag-NPs and ZnO-NPs has high antimicrobial efficacy for both types of microorganisms. Moreover, Ag-NPs prevent the biofilm formation of L. monocytogenes in humid conditions of growth at concentrations of 500 ppm. Additional studies under different conditions are needed to test the durability of nanoparticle containing polyester surfaces with antimicrobial properties to optimize their use.

Aquest article se centra en el problema freqüent de l’anàlisi i la interpretació de resultats per a la detecció de patògens en les indústries alimentàries, posant coma exemple Listeria monocytogenes, com un model que pot ser extrapolat a altres microorganismes. Amb aquest objectiu s’explica la situació actual amb relació a la seguretat alimentària, tot centrant-se en la contaminació de les superfícies, un problema de primer ordre, especialment després d’avaluar el brot ocorregut a Sevilla l’estiu de 2019, relacionat amb L. monocytogenes, com a exemple d’altres casos que es poden estar donant avui en dia al nostre país. Per abordar el problema de l’anàlisi i la interpretació dels resultats analítics a les empreses alimentàries, el mostreig es considera la base de la interpretació, i es diferencia entre mesures quantitatives i qualitatives. En tot moment es pretén donar un estudi estadístic senzill, aportant exemples que permetin ajudar en la presa de decisions d’una empresa alimentària preocupada per la seguretat dels productes que elabora i que vulgui obtenir un bon rendiment dels costos analítics. Es tracten conceptes com mostreig i estadística descriptiva, la diferència de concepte entre mesures independents i mesures repetides, així com la importància de l’objectiu de seguretat alimentària (FSO, de l’anglès food safety objective) i la interpretació de la freqüència en què es presenta un patogen, en funció de la mida de la mostra i l’històric de resultats. Amb aquesta informació és d’esperar que es pugui ajudar la indústria i que es faciliti la presa de decisions.PARAULES CLAU: Listeria monocytogenes, control de microorganismes, interpretaci&, This paper focuses on the frequent problem of analysis and interpretation of results in the detection of pathogens in the food industries, using the case of Listeria monocytogenes as a model that can be extrapolated to other microorganisms. To this end, we deal with the current situation of food safety, discussing surface contamination, which represents a first-rate problem in the food industry. Specifically, the outbreak of infection in Seville in the summer of 2019, caused by L. monocytogenes contamination, may be taken as an example of similar situations that may be happening in our country today. Sampling is considered the basis of interpretation, differentiating between quantitative and qualitative measures. At all times it is sought to establish a simple statistical approach, providing examples that may contribute to the understanding of the situation. This is of help in the decision-making process of any food-processing company which is concerned about the safety of its products, and which seeks to obtain a good yield from its analytical costs. We cover concepts such as sampling, descriptive statistics, the difference in concept between isolated and repeated measures, as well as the importance of the food safety objective (FSO) and the interpretation of the frequency of occurrence of a pathogen, depending on the sample size and the record of results. With this information, it is hoped that industry may be assisted and that the decision-making process may be facilitated.KEYWORDS: Listeria monocytogenes, microorganism control, interpretation of results, descriptive statistics, pathogens, food safety.